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A STUDY ON EFFICACY OF HELICAL COMPUTED
TOMOGRAPHY IN DETERMINATION OF CAUSE,
SITE OF HIGH GRADE SMALL BOWEL
OBSTRUCTION, BOWEL VIABILITY AND
CORRELATION WITH INTRAOPERATIVE
FINDINGS.
BY DR. SATHISH RAVIRALA
Regn. No: 140-41159-112-101908
A thesis submitted as part of fulfillment of the requirements for the
DIPLOMATE OF NATIONAL BOARD OF EXAMINATIONS
RADIODIAGNOSIS.
MEENAKSHI MISSION HOSPITAL& RESEARCH CENTRE
MADURAI -625107
TAMILNADU, INDIA.
JUNE-2014
CERTIFICATE
This is to certify that A study on efficacy of helical computed
tomography in determination of cause, site of high grade small bowel
obstruction, bowel viability and correlation with intra operative
findings. Is a bonafide work of Dr.Sathish Ravirala, DNB Resident,
carried out in the Department of Imaging sciences, Meenakshi Mission
Hospital and Research Centre, Madurai.
I have great pleasure in forwarding this dissertation to the National
Board of Examinations, New Delhi in part of fulfillment of the regulations
for the award of DNB post graduate Degree in Radio Diagnosis prior to the
examination to be held in June 2014.
Madurai Dr.RameshArdhanari MS.,MCh.(SGE)FRCS Medical Director, Sr.Consultant and Head of Department, Department of Surgical Gastro-enterology , Meenakshi Mission Hospital and Research Centre, Madurai, Tamilnadu.
CERTIFICATE
This is to certify that A study on efficacy of helical computed
tomography in determination of cause, site of high grade small bowel
obstruction ,bowel viability and correlation with intra operative
findings is a bonafide work has been carried out by the candidate himself
under my direct supervision and the findings presented have been checked
thoroughly by me. I am fully satisfied with the work of Dr.Sathish Ravirala,
which is being presented by him as a dissertation for Diplomate of National
Board in the subject of Radio Diagnosis during his training period at
Meenakshi Mission Hospital and Research Centre, Madurai, Tamilnadu.
Madurai Dr. S. Manohar MD., DMRD.
Head of the Department. Department of Imaging sciences, Meenakshi Mission Hospital and Research Centre, Madurai, Tamilnadu.
CERTIFICATE
This is to certify that A study on efficacy of helical computed
tomography in determination of cause, site of high grade small bowel
obstruction ,bowel viability and correlation with intra operative
findings is a bonafide work has been carried out by the candidate himself
under my direct supervision and the findings presented have been checked
thoroughly by me as a guide , i am fully satisfied with the work of
Dr.Sathish Ravirala, which is being presented by him as a dissertation for
Diplomate of National Board in the subject of Radio Diagnosis during his
training period at Meenakshi Mission Hospital and Research Centre,
Madurai, Tamilnadu.
Madurai Dr. N.S. Mani MD., DMRD., Consultant, Department of Imaging sciences, Meenakshi Mission Hospital and Research Centre, Madurai, Tamilnadu.
DECLARATION
I declare that this dissertation titled A study on efficacy of helical
computed tomography in determination of cause, site of high grade
small bowel obstruction ,bowel viability and correlation with
intraoperative findings has been conducted by me under the guidance and
supervision of Dr.N.S.MANI., MD., DMRD., Consultant, Department of
Imaging sciences, Meenakshi Mission Hospital and Research Center,
Madurai. It is submitted as part of fulfillment of the requirement for the
award of the D.N.B. RadioDiagnosis, June 2014 examination held under
National Board of Examinations, New Delhi.
Dr. Sathish Ravirala
]
ACKNOWLEDGEMENT
I am extremely thankful to the Chairman, ViceChairman and
Medical Director of Meenakshi Mission Hospital and Research Center,
Madurai, who have been kind enough to permit me to use the hospital
resources. I thank all the patients who have been a part of this study making
my thesis possible.
I express my sincere and heartful gratitude to my guide
Dr.N,S.Mani.,MD.,DMRD for his guidance and support. My sincere thanks
also goes to Dr. S.Manohar MD., DMRD. (Head of the department)
My sincere thanks to Dr.T.Mukuntharajan.,DMRD., (Sr.Consultant),
Dr.N.Karunakaran., DMRD.,DNB.,(Consultant), Dr.R.Ganesh.,DMRD.,
DNB.,(Consultant), Dr.Nancy manodoss., MD., (Registar) for their ideas,
wisdom, supervision and guidance without whom I could not have done my
dissertation. I thank my other consultants Dr.M.S.Senthilnathan.,MD., for
their valuable ideas.
My special acknowledgement to Department of Surgical -
Gastroenterology for their co-operation throughout my thesis work.
I wish to thank my department seniors Dr.Kokilan, Dr.SunilBorade,
who always helping me throughout my course period, My special thanks to
my colleagues Dr.Kiranmai, Dr.Mohan, Dr.Chetan, my juniors Dr.Kiran
Kumar, Dr.Jayanthan & Dr.Divya., my friends Dr.Srikanth, Dr.Naresh .
I thankful to Medical records Department , Mr.Mani Bio-statistician ,
nursing staff, ward secretaries Lakshmi, Elizabeth for helping me in
conducting the study.
Last but not least my parents, and my wife Dr.Sindhuri, my sister
Dr.Manjula, my brother Dr.Sandeep for their support as always.
CONTENTS
S.NO. TITLE PAGE NO
1. Introduction 1
2. Aims & Objectives 6
3. Review of Literature 26
4. Materials and Methods 38
5. Results and Analysis 43
6. Discussion 53
7. Conclusion 59
Annexure
Bibliography
Proforma
Master chart
INTRODUCTION
Small Bowel Obstruction (SBO) is a common clinical condition, one
of the important causes of pain abdomen and forms 20% of surgical
emergencies. Small Bowel Obstruction usually suspected on the basis of
clinical signs and patient history .It can be self-limiting or life threatening
and therefore prompt diagnosis to determine the site and cause of obstruction
is mandatory to reduce the morbidity and mortality.
Till last decade, conventional Radiographs played a major role in the
diagnosis of small bowel obstruction but it has a low sensitivity of 69% and
specificity of 57% .With the advent of multi-slice imaging techniques, rapid
comprehensive assessment of the entire abdomen can be done in a matter of
few seconds thus allowing the entire small bowel to be studied for the cause
and site of obstruction and also more importantly the viability of the bowel.
Several studies have shown the value of CT in demonstrating diagnosis and
determining the cause of high grade obstruction with the sensitivity of about
94-100% and specificity of 90%-95%1.
History:
X-Rays were discovered by Wilhelm-Conrad Roentgen in November
1895, Whilst he was experimenting with the passage of electricity through
gases at very low pressure. When an electric discharge at high voltage was
passed through the almost evacuated tube, Roentgen noticed a glow on a
piece of cloth covered with Zinc Sulphide, which was lying at a short
distance from the tube. The glow persisted even when the tube was covered
with black paper and Roentgen was quickly able to recognize this as a
hitherto undiscovered radiation and named it as X-Rays.
At the Annual congress of the British Institute of Radiology, in April
of 1972, G.N.Hounsfield, a senior research scientist at EMI limited in
Middlesex, England, announced the invention of a revolutionary new
imaging technique, which he called Computerized axial transverse
scanning. The basic concept was very simple, a thin cross section of the
head, a tomographic slice, was examined from multiple angles with a pencil
like x-ray beam. The transmitted radiation was counted by a scintillation
detector, fed into the computer for analysis by a mathematical algorithm and
reconstructed.
The image had a remarkable characteristic, one never before seen in a
x-ray imaged; it demonstrated a radiographic difference in the various soft
tissues; blood clots, gray matter, white matter, cerebrospinal fluid, tumors
and cerebral edema all appeared as separate entities. The soft tissues could
no longer be assigned the physical characteristics of water. The computer
had changed that concept.
The basic principle behind CT is that the internal structure of an
object can be reconstructed from multiple projections of the object. CT
scanners have gone through a number of design changes since the
technology was first introduced in 1971.They can be conveniently classified
under five categories.
They are-
1. First generation (translate-rotate, one detector.)
2. Second generation (translate-rotate, multiple detectors.)
3. Third generation (rotate-rotate)
4. Fourth generation (rotate-fixed.)
5. Other geometries.
Time reduction is the predominant reason for introducing new
configurations. Scan time has been reduced in newer configurations by the
reduction or simplification of mechanical motion. For example, the stop-start
motion in the first two generations has been replaced by continuous rotation.
Devices that have no moving parts and an extremely short scan time have
come. Initial research papers reported by Alec Megibow and his colleagues 2
in the evaluation of bowel obstruction with computed tomography (CT)
came in the year 1991 and since then CT has emerged as a versatile &
invaluable modality for the diagnosis and evaluation of Small Bowel
Obstruction.
Four important basic questions should be answered in any case of
suspected Small Bowel Obstruction.
a. Is the bowel obstructed?
b. What is the level, cause and degree of obstruction?
c. Is strangulation present?
d. Is conservative therapy sufficient or surgery needed?
Helical CT answers all these questions comfortably most of the times
and more superior to conventional radiographs and contrast studies. Recent
innovations like multi-detector CT has really revolutionized the imaging of
abdominal pathologies and CT is useful in evaluate the site and type of
hernia and its content3,4,5, especially the diagnosis of internal hernia, always
require radiological findings6,7.
Multiplanar reformatted imaging at a work station is a new technology
in a Multi Detector Computed Tomography (MDCT)8, its gaining more
importance and promising in the diagnosis of small bowel obstruction.
Volume data of the abdomen are acquired with helical technique during a
single breath- hold, usually with a collimation of 5-7 mm. Thinner
collimation for better spatial resolution is possible with a multi detector CT
scanner. Axial, sagittal, coronal and curved multiplanar reformatted images
are created at a work station from the acquired volume data. These
multiplanar views may help to identify the site and cause of obstruction
when axial findings are indeterminate.
AIM OF THE STUDY
* A study on efficacy of helical computed tomography in determination of
cause, site of high grade small bowel obstruction, bowel viability and
correlation with intraoperative findings.
Objectives
1. Confirm the high grade Small Bowel Obstruction
2. To assess Cause, Site of Small Bowel Obstruction
3. To assess the Viability of Bowel loops
4. Correlation of CT findings with Intraoperative findings.
5. To assess the Sensitivity, Specificity, Accuracy of Spiral CT with
Intraoperative findings.
NORMAL ANATOMY
The small intestine is a convoluted tube, extending form the pylorus to
the ileocaecal valve, where it ends in the large intestine. It is about 7meters
long, and gradually diminishes in size from its commencement to its
termination. It is contained in the central and lower part of the abdominal
cavity. It is in relation, in front, with the greater omentum and abdominal
parieties, and is connected to the posterior abdominal wall by a fold of
peritoneum, the mesentery. The small intestine is divisible into three portions
: the duodenum, the jejunum, and the ileum.
Duodenum:
The duodenum has received its name from being about equal in length to
the breadth of twelve fingers (25cm). It is the shortest, the widest, and the
most fixed part of the small intestine, and has no mesentery, being only
partially covered by peritoneum. It is divided into 4 parts. i.e, superior,
descending, horizontal and ascending. As it unites with the jejunum it turns
abruptly forward, forming the duodeno-jejunal flexure.
The common bile duct and pancreatic duct together perforate the medial
side of 2nd part of duodenum, obliquely 7 to 10cm below the pylorus, the
accessory pancreatic duct sometimes pierces it about 2cm above and slightly
in front of these.
Vessels and nerves :
The arteries supplying the duodenum are the right gastric and superior
pancreatico- duodenal branches of the hepatic, and the inferior pancreatico-
duodenal branch of the superior mesenteric arteries. The veins end in
superior mesenteric vein & others. The nerves are derived from the celiac
plexus.
Jejunum and ileum :
The remainder of the small intestine from the end of the duodenum is
named jejunum and ileum, the former term being given to the upper two-
fifths and the latter to the lower three-fifths. There is no morphological line
of distinction between the two, and the division is arbitrary, but at the same
time the character of the intestine gradually undergoes a change from the
commencement of the jejunum to the end of the ileum, so that a portion of
bowel taken form these two situations would present characteristic and
marked differences. These are briefly as follows.
The jejunum is wider, thicker, more vascular, and of a deeper color than
the ileum, so that a given length weighs more. The circular folds (valvulae
conniventes) of its mucous membrane are large and thickly set and its villi
are larger than in the ileum, The aggregated lymph nodules are almost absent
in the upper part of the jejunum, and in the lower part are less frequently
found than in the ileum, and are smaller and tend to assume a circular form.
By grasping the jejunum between the finger and thumb the circular folds
can be felt through the walls of the gut, these being absent in the lower part
of the ileum, it is possible in this way to distinguish the upper from the lower
part of the small intestine.
The ileum is narrow, thinner and less vascular than those of the jejunum.
It possesses but few circular folds, and they are small and disappear entirely
towards its lower end, but aggregated lymph nodules (peyer's patches) and
larger and more numerous. The jejunum for the most part occupies the,
umbilical and left iliac regions, while the ileum occupies chiefly the
umbilical, hypogastric, right iliac and pelvic regions. The terminal part of
the ileum usually lies in the pelvis, from which it ascends over the right
psoas and right iliac vessels; it ends in the right iliac fossa by opening into
the medial side of the commencement of the large intestine. The jejunum
and ileum are attached to the posterior abdominal wall by an extensive fold
of peritoneum, the mesentery, which allows the free motion, so that each coil
can accommodate itself to changes in form and position.
The root of the small bowel mesentery (SBM) is located in the central
portion of the abdomen, connecting the intraperitoneal structures and is
contiguous to other peritoneal ligaments. The small bowel mesentery is a
voluminous, fat laden peritoneal reflection that fixes the jejunum and ileum
to the posterior abdominal wall. The attached parietal border which is
approximately 15cm long runs obliquely down from the deudenojejunal
flexure to the ileocaecal region. The root of the small bowel mesentery
contains two major vessels, the superior mesenteric artery (SMA) and
superior mesenteric vein (SMV)
Meckels diverticulum
This consists of a pouch which projects from the lower end of ileum in
about 2 percent of subjects. Its average position is about 1 meter from
ileocaecal valve, and its average length about 5cm.Its caliber is generally
similar to that of ileum, and its blind extremity may be free or may be
connected with the abdominal wall or with some other portion of the
intestine by a fibrous band. It represents the remains of the proximal end of
the vitelline duct, the duct of communication between the yolk-sac and the
primitive digestive tube in early fetal life.
Vessels and nerves:
The jejunum and ileum are supplied by the superior mesenteric artery,
the intestinal branches of which, having reaches the attached border of the
bowel, run between the serous and muscular coats, with frequent
inosculations to the free border, where they also anastomose with other
branches running around the opposite surface of the gut. Form these vessels
numerous branches are given off, which submucous tissue. From this plexus
minute vessels pass to the glands and villi of the mucous membrane.
The veins have a similar course and arrangement to the arteries. The
lymphatics of the small intestine (lacteals) are arranged in two sets, those of
the mucous membrane and those of the muscular coat. The lymphatics of the
villi commence in these structures in the manner described above. They
form an intricate plexus in the mucous and submucous tissue, being joined
by the lymphatics from the lymph spaces at the bases of the solitary nodules,
and from this pass to larger vessels at the mesenteric border of the gut. The
lymphatics of muscular coat are situated to a great extent between the two
layers of muscular fibers, where they form a close plexus, throughout their
course they communicate freely with the lymphatics from the mucous
membrane, and empty themselves in the same manner as these into the
origins of the lacteal vessels at the attached border of the gut.
Image 1-Small intestine with arterial blood supply.
(Image taken from Netters Atlas of Human anatomy-4 th edition)
The nerves of the small intestines are derived from the plexuses of
sympathetic nerves around the superior mesenteric artery. From this source
they run to the myenteric plexus (Auerbach's plexus) of nerves and ganglia
situated between the circular and longitudinal muscular fibers from which
the nervous branches are distributed to the muscular coats of the intestine.
From this a secondary plexus, the plexus of the submucosa (Meissner's
plexus) is derived, and is formed by branches which have perforated the
circular muscular fibers. This plexus lies in the submucous coat of the
intestine, it also contains ganglia from which nerve fibers pass to the
muscularis mucosa and to the mucous membrane. The nerve bundles of the
submucous plexus are finer than those of the myenteric plexus.
SMALL BOWEL OBSTRUCTION - AN OVERVIEW
Small bowel obstruction (SBO) can be partial or complete, simple (i.e.,
non- strangulated) or strangulated. Strangulated obstructions are surgically
emergencies. If not diagnosed and properly treated, vascular compromise
leads to bowel ischemia and further increase morbidity and mortality rates.
History
Abdominal pain
Pain, often described as crampy and intermittent, is more
prevalent in simple obstruction.
Often, the presentation may provide clues to the approximate
location and nature of the obstruction. Usually, pain that occurs
for a shorter duration of time and is colicky and accompanied by
bilious vomiting may be more proximal. Pain lasting as many as
several days, which is progressive in nature and with abdominal
distention, may be typical of a more distal obstruction.
Changes in the character of the pain may indicate the
development of a more serious complication (i.e., continuous
pain of strangulated or ischemic bowel)
Nausea
Vomiting, which is associated more with proximal obstructions.
Diarrhoea (an early finding)
Consitpation (a late finding) as evidenced by the absence of flatus or
bowel movements.
Fever and tachycardia - occur late and may be associate with
strangulation.
Previous abdominal or pelvic surgery, previous radiation therapy, or both
(may be part of patient's medical history).
History of malignancy (particularly ovarian and colonic)
Clinical examination
Radiologist before imaging, being primarily a clinician should look for
the following features.
Abdominal distension.
Hyperactive bowel sounds occur early as GI contents attempt to
overcome the obstruction.
Hypoactive bowel sounds occur late.
Exclude incarcerated hernias of the groin, femoral triangle and obturator
foramina.
Proper genitourinary and pelvic examinations are essential.
Look for the following during rectal examination
Gross or occult blood, which suggest late strangulation or
malignancy.
Masses, which suggest obturator hernia.
Check for symptoms commonly believed to be more diagnostic of
intestinal ischemia, including the following
Fever (temperature >100F )
Tachycardia (>100beats /min).
Peritoneal signs.
No reliable way exists to differentiate simple from early strangulated
obstruction on physical examination. Serial abdominal examinations are
important and may detect changes early.
A small bowel obstruction (SBO) is caused by a variety of pathologic
processes. They can be broadly classified into congenital and acquired
(Gore's classification)
Congenital causes of SBO
Duodenal atresia
Jejunal atresia
Ileal atresia/stenosis
Midgut volvulus
Meckels diverticulum
Inspissated meconium
Acquired causes of SBO
Extrinsic lesions Intrinsic lesions
Adhesions
Hernias
External
Inguinal
Femoral
Obturator
Umbilical
Sciatic
Perineal
Supravesical
Spigelian
Lumbar
Incisional
Internal
Paraduodenal
Epiploic foramen
Diaphragmatic (traumatic)
Transomental
Tumors infiltrating wall of small
intestine
Adenocarcinoma
Carcinoid tumor
Lymphoma
Leiomysarcoma
Inflammatory conditions
Crohn's disease
Tuberculosis.
Potassium chloride stricture
Eosinophilic gastroenteritis
Radiation enteropathy
Hematoma
Post- traumatic hematoma
Thrombocytopenia
Anticoagulants
Henoch-schonlein purpura.
Transmesenteric
Masses
Extrinsic tumors in mesentery
Lymphoma
Peritoneal metastasis
Carcinoid
Desmoid
Inflammations / Abscess
Diverticulitis
Appendicitis
Pelvic inflammatory disease
Crohn's disease
Hematoma
Aneurysm
Endometriosis
Insussusception
Polyps, lipoma
Tumor
Duplication
Intraluminal causes
Gall stone
Bezoar
Foreign body
Ascariasis
PATHOPHYSIOLOGY
Early in the course of an obstruction, intestinal motility and contractile
activity increase in an effort to propel luminal contents past the obstructing
point. The increase in peristalsis that occur early in the course of bowel
obstruction is present both above and below the point of obstruction, thus
accounting for the diarrhea that may accompany partial or even complete
small bowel obstruction in the early period.
Obstruction of the small bowel leads to proximal dilatation of the
intestine due to accumulation of gastrointestinal secretions and swallowed
air. This bowel dilatation, stimulates increased cell secretory activity
resulting in more fluid accumulations, leading to increased peristalsis both
above and below the obstruction with fragment loose stools and flatus early
in its course.
Increased small bowel distension leads to increased intraluminal
pressures. This can cause compression of mucosal lymphatics leading to
bowel wall lymphedema. Later in the course of obstruction, the intestine
becomes fatigued and dilated, with contractions becoming less frequent and
less intense.
As the bowel dilates, water and electrolytes accumulate both
intraluminally and in the bowel wall itself. This massive third -space fluid
loss accounts for the dehydration and hypovolemia. The metabolic effects of
fluid loss depend on the site and duration of the obstruction. With a proximal
obstruction, dehydration may be accompanied by hypochloremia,
hypokalemia, and metabolic alkalosis associated with increased vomiting.
Distal obstruction of the small bowel may result in large quantities of
intestinal fluid into the bowel; however, abnormalities in serum electrolytes
are usually less dramatic. Oliguria, azotemia, and hemoconcentration can
accompany the dehydration. Hypotension and shock can ensue. Other
consequences of bowel obstruction include increased intra abdominal
pressure, decreased venous return and elevation of the diaphragm,
compromising ventilation. These factors can serve to further potentiate the
effects of hypovolemia.
As the intraluminal pressure increases in the bowel, a decrease in
mucosal blood flow can occur. These alterations are particularly noted in
patients with a closed - loop obstruction in which greater intraluminal
pressures are attained. A closed - loop obstruction, produced commonly by
twist of the bowel, can progress to arterial occlusion and ischemia if left
untreated and may potentially lead to bowel perforation and peritonitis.
In the absence of intestinal obstruction, the jejunum and proximal ileum
of the human are virtually sterile. With obstruction, however, the flora of the
small intestine changes dramatically, in both the type of organism (most
commonly Escherichia coli, streptococcus faecalis, and klebsiella) and the
quantity with organisms reaching concentrations of 109 to 10 10per ml
studies have shown an increase in the number of indigenous bacteria
translocating to mesenteric lymph nodes and even systemic organs.
Imaging studies
Plain radiography
* Obtain plain radiographs first for patients in whom SBO is suspected
* At least 2 views, supine or flat and upright, are required.
* Plain radiographs are diagnostically more accurate in cases of simple
obstruction; however, diagnostic failure rates of as much 30% have
been reported. In one small study, the sensitivity of plain radiographs was
reported as 75% and specificity was reported to be 53%.Similar findings
were reported in a second study.
* In one study, plain films were more accurate in the detection of an
acute SBO and the accuracy was higher if interpreted by more experienced
radiologists.
* Plain radiography is of little assistance in differentiating strangulation
from simple obstruction. Some have used abdominal radiography to
distinguish between complete obstruction and partial or no SBO. A study by
Lappas et al9 proposed that two findings were more predictive of a higher
grade of complete SBO: present of air-fluid differentiation height in the
same small- bowel loop and presence of a mean level width greater than
25mm. The study found that when the two findings are present, the
obstruction is most likely high grade or complete. When both are absent, the
authors proposed that a low grade (partial) SBO is likely or nonexistent.
* Fixed, dilated U or C shaped bowel loops may suggest closed loop
obstruction.
* Small amounts of air trapped between the plicae circularis in an
upright films produce a " string of beads or pearls" appearance (most
specific sign). Multiple Air- Fluid levels, Step ladder configuration, Gasless
abdomen are the other specific signs.
Ultrasonography
Ultrasonography is less costly and less invasive than CT scanning.
It may reliably exclude SBO in as may as 89% of patients.
Specificity is reportedly 100%.
Enteroclysis
Enteroclysis is valuable in detecting the present of obstruction and in
differentiating partial from complete blockage.
This study is useful when plain radiographic findings are normal in
the presence of clinical signs of SBO or if plain radiographic findings
are nonspecific.
It distinguishes adhesions form metastases, tumor recurrence, and
radiation damage.
Enteroclysis offers a high negative predictive valve and can be
performed with 2 types of contrast..
Barium is the classic contrast agent used in this study. It is safe and
useful when diagnosing obstructions provided no evidence of bowel
ischemia or perforation exists. Barium has been associated with
peritonitis and should be avoided if perforation is suspected.
Enteroclysis with multiplanar CT is being used to overcome the
limitations of use of either modality (enteroclysis or CT individually)
and may ultimately simplify the understanding of the obstructive
process and assist with management.
CT enteroclysis can be performed by using positive enteral material
without I.V. contrast material (or) neutral enteral contrast material with
I.V.contrast10.
Computed tomography (CT).
Routine CT is good in diagnosing high grade small bowel
obstruction,with accuracy of more than 90%2,11 , however it is less
accurate in cases of low grade small bowel obstruction with
sensitivity of 50% &specificity of 94%1,12.
CT is useful in making an early diagnosis of strangulated obstruction
and in delineating the myriad other causes of acute abdominal pain,
particularly when clinical and radiographic findings are inconclusive.
It also has proved useful in distinguishing the etiologies of SBO,
that is extrinsic causes such as adhesions and hernia from intrinsic
causes.
It is capable of revealing abscess, inflammatory process, extra
luminal pathology resulting in obstruction, and mesenteric ischemia.
CT enables the clinicians to distinguish between ileus and
mechanical small bowel obstruction in post-operative patients.
CT does not require oral contrast for the diagnosis of SBO because
the retained intraluminal fluid severe as a natural contrast agent.
Obstruction is present if the small bowel loop is greater than 2.5cm
in diameter dilated proximal to a distinct transition zone of collapsed
bowel.
Following patterns of entero-enteric intussusception namely target
sign, reniform mass and a sausage shaped mass with alternating
layers of low and high attenuation can be visualized13.
U or C - shaped dilated loops, radial distribution of mesenteric
vessels, beak sign and whirl sign suggest closed loop obstruction.
A smooth beak indicates simple obstruction without vascular
compromise; a serrated beak may indicate strangulation.
Pneumatosis, portal venous gas indicates early strangulation.
REVIEW OF LITERATURE
There are several studies have been published in evaluating the role of CT in
detecting the site and cause of high grade small bowel obstruction.Computed
Tomography has emerged as a premier modality and has a tremendous
impact in the evaluation and management of high grade small bowel
obstruction.A brief review of literature will be discussed below.
Omair Shakil et al 14 retrospectively studied the spiral CT in cases of
small bowel obstruction over a period of 5 years in adult Pakistani
population, who underwent exploratory laparotomy. He studied the
accuracy of spiral CT in identification & cause of bowel obstruction, and
calculated the sensitivity, specificity, positive and negative predictive values.
A total of 271 patients were studied, 104 cases had intestinal obstruction
intra operatively but CT has diagnosed 97 cases with sensitivity of 93%,
specificity of 93% and positive predictive value of 89% . Spiral CT
identified cause in 72 cases(74%) .This study concluding that spiral CT
scans shows high sensitivity and specificity in diagnosing intestinal
obstruction, but less efficacy in determining the cause of the obstruction.
David Frager et al 15 evaluated the value of spiral CT in establishing
the diagnosis and determining the degree, cause of small bowel obstruction
as compared with traditional clinical-radiographic assessment. A total of 90
examinations were evaluated over a period of 11 months. On the basis of the
combined clinical-radiographic findings, the diagnosis was complete
obstruction in 21 of 46 cases with sensitivity, 46%. When CT was used, the
diagnosis was established in all 46 cases with sensitivity 100%. In the 25
cases in which the traditional assessment failed, the early CT able to identify
complete obstruction, so that reduces delay in surgery. On the basis of the
combined clinical-radiographic findings, partial obstruction of the small
bowel was diagnosed in 6 of 20 cases with sensitivity of 30% , whereas all
cases were detected with CT. Thus this study concluded that CT is highly
sensitive and superior to combined clinic-radiographic findings.
Marc Zalcman et al 16 prospectively evaluated the reliability and
usefulness of helical CT in diagnosing ischemic signs in cases of small
bowel obstruction. He studied a total of 144 examinations over a period of 3
years with correlation with intraoperative findings. The following signs of
strangulation and ischemia taken into consideration: reduced enhancement
of the small-bowel wall, mural thickening, mesenteric fluid, congestion of
small mesenteric veins, and ascites. If enhancement of the bowel wall was
reduced or if at least two of the other signs were noticed, are the criteria for
ischemia on spiral CT. Intraoperatively ischemic bowel loops were noted in
24 cases. CT correctly identified ischemia in 23 cases ,with sensitivity of
96%, 9 false positives with specificity of 93% &The negative predictive
value of CT was 99%.Coming to individual parameters, reduced
enhancement of the bowel wall had a sensitivity of 48% and specificity of
100%, mural thickening had a sensitivity of 38% and specificity of 78%,
mesenteric fluid had a sensitivity of 88% and specificity of 90%, congestion
of mesenteric veins had a sensitivity of 58% and specificity of 79%, and
ascites had a sensitivity of 75% and specificity of 76%.This study highlights
the role of spiral CT in diagnosing ischemia in cases of small bowel
obstruction.
Alec J. Megibow and his colleagues2 retrospectively evaluated the
role of spiral CT in intestinal obstruction (included large bowel also in his
study) over a period of 2 years. A total of 167 cases were studied, in this 84
cases referred as intestinal obstruction, remaining 83 cases are control group.
CT evaluation done by two radiologists, who un aware of patient history,
confirmation of bowel obstruction by intraoperative findings ,clinical course
and barium studies and the results were analyzed .Among 84 cases, which
referred as intestinal obstruction, 64 cases only having intestinal obstruction
and 20 cases does not have obstruction. In this 64 cases of confirmed
intestinal obstruction, CT able to identify 60 cases correctly and 4 cases
were missed with false negative of 4 cases. Among 20 cases of not having
obstruction, CT showed 4 cases having obstruction and 16 cases not having
obstruction with a false positive of 4 cases. In 83 control group, none of
them was diagnosed as obstruction by CT. analysis showed the spiral CT has
a sensitivity of 94%, specificity of 96% and accuracy of 95% in this study.
In 64 cases of intestinal obstruction 55 cases were small bowel obstruction
and 9 cases were large bowel obstruction. The etiology was correctly
identified in 47 of 64 cases (73%).The cause of the obstruction was correctly
predicted in 47 of 64 cases (73%). Adhesions were correctly diagnosed as
the cause of the obstruction in 27 of 37 cases (73%). In this study adhesions
are the most common cause of intestinal obstruction. This study concludes
that spiral CT has role in identification and etiology of bowel obstruction.
Funda Obuz et al 17prospectively studied the ability of helical CT
(computed tomography) in determining the cause & viability in 41 patients
who presented with small bowel obstruction, he found that there is high
correlation, helical CT has sensitivity of 84% and specificity of 90% in
demonstrating the cause of obstruction, all 6 cases with no bowel
enhancement in CT were confirmed with intra operative findings. Thus he
concluded helical CT has a role in determining the etiology and vascular
complications in cases of small bowel obstruction.
Emil J. Balthazar et al 18 prospectively studied100 consecutive spiral
CT examinations, who suspected small bowel obstruction clinically over a
period of 2 years. He studied accuracy of spiral CT in confirming the small
bowel obstruction and diagnosing the viability of bowel loops. Among 100
cases, 60 were men, 40 women and age group ranging from 19 to 90 years
with mean of 52 years. The CT features compared with operative findings in
77 patients and clinical follow-up in 23 patients. The interval between CT
and surgical exploration in patients with ischemic bowel was mean duration
of 13 hours. Criteria for bowel ischemia taken consideration in this study
were -slight circumferential thickening of the bowel wall, increased
attenuation, target or halo sign, pneumatosis intestinalis, lack of
enhancement of the wall on I.V. contrast and haziness of the mesenteric
vessels, or mesenteric hemorrhage obscuring mesenteric vessels. Spiral CT
diagnosed small bowel obstruction in 90 cases, and ileus in 10 cases with
two false negatives & no false positives. Correlation of CT findings of
strangulation with surgical findings showed 72 cases true-negative, 19 true-
positive, five false-positive, and four false-negative CT results with
sensitivity of 83%, specificity of 93%, accuracy was 91%, positive
predictive value was 79%, and negative predictive value was 95%.This
study showed spiral CT help in accurate diagnosis of bowel ischemia in
cases of small bowel obstruction. Exploratory laparotomy should be done,
when disparity between equivocal CT findings and a deteriorating clinical
condition.
Scaglione M et al 19 retrospectively reviewed 120 cases of small
intestine closed loop obstruction over a period of 3 years. All these cases are
operated, with in a period of 6 hours after doing spiral CT. These 120 cases
of closed loop obstruction were evaluated for bowel ischemia and results
were analyzed. CT signs taken into consideration for diagnosing ischemia
were: submucosal edema, increased, reduced, or no enhancement of the loop
walls, edema of the mesenteric vessels, fluid within the loops or in the
intraperitoneal spaces. 120 cases were thoroughly evaluated, Spiral CT
diagnosed ischemia in 26 cases, but in reality there are 51 cases showed non-
viable bowel loops intraoperatively. In this study of 120 cases they missed
bowel ischemia in 25 cases preoperatively. In 26 cases which were
diagnosed ischemia by CT ,all were came as non-viable intraoperatively,
thus in this study they showed Spiral CT had 100% positive predictive value
in bowel viability. In this study CT showed 94 cases have viable bowel
loops, but 25 cases had non-viable bowel loops intraoperatively with
negative predictive value of 73%. Thus he concluded that even though Spiral
CT had good positive predictive value for diagnosing bowel ischemia ,
depending up on CT we cant say confidently, which dont show bowel
ischemia on CT ,cant be viable in reality, there is a chance of missing
ischemia on CT. So if any change in trophic status of bowel loops or its
mesentery may imply ischemic changes, and need for emergency
laparotomy.
Catel L et al 20 retrospectively reviewed 43 cases of Adhesive small
bowel obstruction for evaluation of bowel ischemia. All cases were
evaluated by three experienced radiologists. Signs for complicated small
bowel obstruction in this study were reduced enhancement of the small
bowel wall, mural thickening, congestion of small mesenteric veins, and
ascites. In this study 15 patients had ischemic signs on CT, 28 patients does
not have. Coming to individual parameters in diagnosing bowel ischemia a
sensitivity of 57% and a specificity of 100% noted with reduced bowel wall
enhancement and sensitivity of 35% and a specificity of 100% noted with
bowel wall thickness greater than 3 mm, and sensitivity of 35% and a
specificity of 93%noted if bowel wall thickness less than 1 mm taken as
criteria. In this study ascites and congestion of small mesenteric veins were
not much useful in diagnosing bowel ischemia. If u consider bowel-wall
thickening and reduced bowel wall enhancement ,the sensitivity of 71%,
specificity 100%, and accuracy 90%. So this study concluding that in
evaluation of bowel ischemia, enhancement of small bowel wall, mural wall
thickening & thinning of bowel wall were have significant role.
E J Balthazar et al 21 retrospectively collected data of 19 cases of
small bowel closed loop intestinal obstruction. Spiral CT films were
examined by two radiologists. In this study they are examining for signs of
bowel ischemia in spiral CT in cases of small bowel closed loop obstruction
and comparing with intraoperative findings. Signs of strangulation taken
consideration in this study were wall thickening, high attenuation and target
sign and abnormalities in attached mesentery. Among 19 cases, spiral CT
showed 10 cases had signs of ischemia but intraoperatively16 cases showed
ischemic bowel loops. In this study Spiral CT had missed 6 cases of
strangulation. Among 10 cases CT showed ischemic signs were came as
non-viable intraoperatively with 100% positive predictive value. This study
highlights that absence of ischemic signs in CT, bowel ischemia & necrosis
in closed loop obstruction cant be ruled out.
Michael H. Fuchsjager et al 22studied the Small bowel feces sign in
cases of small bowel obstruction. It is the appearance of feces like matter in
small bowel loops. This sign because of increased water absorption in the
small bowel loops, in cases of small bowel obstruction because of more
transit time, making the intestinal content to be hard and mixing with gas
bubbles, look like feces. The chance of forming this appearance ,more with
prolonged periods of obstruction, so more incidence in sub-acute or low
grade small bowel obstruction. Similar mimicking appearance noted in
conditions like cystic fibrosis, infectious or metabolic Bowel disease,
bezoars and sometimes it can be normal finding because of reflux of fecal
content from cecum to distal ileum. This study suggesting that in a clinical
setting of suspected small bowel obstruction, finding this sign, adding extra
weight age to obstruction. Usually this sign noted in distal portion of dilated
bowel loops. This study summarized that in cases of not much dilated bowel
loops ,especially in low grade obstruction and borderline cases, finding this
sign, may help in diagnosis & these cases frequently requires surgical
treatment .
Another study on small bowel feces sign by J SINGH et al 23, shown
that because of this sign is visualized in distal part of dilated bowel loops,
help in identification of site of obstruction, and more chance of diagnosing
cause of obstruction. Thus he concluded that role of Small bowel feces sign,
in identification of site and cause of obstruction.
Dawn E. Lazarus et al 24 prospectively studied cases of small bowel
obstruction over a period of 5 months. A total of 34 cases with age ranging
from 21-82 years (mean age of 52 years) were included in the study. Among
34 cases 20men and 14 women. His main aim to identify the occurrence of
small bowel feces sign and its capability in demonstrating transition zone.
He divided cases into mild, moderate and high grade small bowel
obstruction on the basis of caliber of proximal and distal bowel loops. A
single experienced radiologist studied the all 34 cases. In this study they
calculated the incidence of this sign in cases of mild, moderate, severe small
bowel obstruction. Among 34 cases, small bowel obstruction was high grade
in 17 cases, moderate in 11 cases, mild in 6 cases. In 34 cases, this sign
noted in 19 cases (55.9%).This sign was demonstrated in 10 cases of high
grade (58.8%), 8 cases of moderate (72.7%), one case(16.6%) of mild small
bowel obstruction. In patients with feces sign, this appearance can be
identified up to transition point. And the extent of this appearance lengthier
in moderate and high grade than mild obstruction. Thus this study highlights
the role of feces sign in identifying transition zone in patients with SBO and
this sign more frequently associated with moderate, severe SBO than mild
SBO.
Usually adhesions as a cause of small-bowel obstruction (SBO) is
diagnosis of exclusion. Bojan Petrovic et al 25 retrospectively studied CT
scans of 142 patients with surgically proven SBO due to adhesions .This
study mainly to evaluate the findings suggestive of an extra luminal band
can be used in diagnosis of adhesive SBO. An extraluminal band was
suggested if any change in the conformation at the transition zone. In 142
patients, the study identified 73 cases having bands, in that 73 cases,
adhesions as cause of obstruction in 52 cases with a positive predictive value
of 71% and a p value of 0.008. This study demonstrated extraluminal band
was sensitivity of 61% and specificity of 63% in diagnosing SBO due to
adhesions. So this study summarized the role of bands in helping the
diagnosis of adhesions in cases of small bowel obstruction.
Diego A. Aguirre et al4 summarizes the role of multidetector CT in
diagnosis of abdominal hernias in problematic situations like scarred tissues,
severe abdominal pain, and obesity. In obese cases, it demonstrates the
location, shape, size and content of abdominal hernias. With 3D imaging and
multiplanar reformations, CT much more helpful in these cases. MDCT
help in identification of signs of strangulation .This study highlights the
importance of MDCT in unrepaired and surgically repaired hernias and thus
help in planning further management.
Akira Furukawa et al 26 confirms that with recent technological
developments, now CT is highly sensitive and specific in determining the
presence of bowel obstruction and clearly demonstrates the site, cause of
obstruction and also recommends CT for evaluation of patients with
suspected bowel obstruction, particularly in the cases, where clinical &
conventional radiographic findings were indeterminate and suspicion of
viability of bowel loops.
MATERIALS AND METHODS
The present prospective study was conducted at Meenakshi Mission
Hospital & Research Centre, Madurai during the period from October 2011
to October 2013.83 patients in the age group between 2 months to 79 years
with strong suspicion of Small Bowel Obstruction on the basis of clinical
grounds, plain radiographs and ultrasonography findings were subjected to
Helical CT evaluation of the abdomen. More importantly all of the above
patients were hemodynamically stable at the time of CT scan.
Several reports have shown the accuracy of CT in the diagnosis of
Small Bowel Obstruction. However, these studies were mostly retrospective
,the effective role & impact of CT in the diagnosis and management of
Small Bowel Obstruction remains to be explored. The aim of our
prospective study was to evaluate the role of CT in determining the cause
and level of high grade obstruction, bowel viability and correlation with
intraoperative findings.
Inclusion criteria:
All the patients with strong clinical suspicion (vomiting, abdominal
pain,distension, malena, constipation, obstipation) and plain radiographic,
sonographic evidence of Small Bowel Obstruction were included in the
study.
Exclusion criteria:
Patient in early post operative period, generalized septicemia,
electrolyte disturbances i.e., hypokalemia and history of trauma were
excluded from study.
CT protocols:
All patients were scanned with GE optima 660- 64 slice multidetector
CT scanner. Initially, plain helical acquisition from the dome of diaphragm
to the inferior edge of the ischium was taken.
Depending up on the plain CT findings ,oral contrast was given to the
patients. All the patients were not administered oral contrast because most of
the patients had severe vomiting and more importantly positive contrast in
the bowel can obscure the etiology of the obstruction & enhancement of the
mucosa of the bowel lumen. The inherent fluid in the dilated bowel acts as a
contrast in most cases of high grade Small bowel Obstruction. Oral contrast
if given, it was given in the form of 30 ml of Gastroscan+ M
(Diatrizoatemeglumine and Diatrizoate sodium solution-370 mg /ml iodine)
mixed in 1200 to 1500 ml of mineral water or flavoured drinks and
administered orally over a period of 45-60 minutes. Around 150-200 ml of
oral contrast is administered just before the I.V.( Intravenous)contrast study
as a table dose. We advocated oral contrast only in few patients who had
previous history of abdominal surgeries suspecting adhesive intestinal
obstruction and in other patients fluid in the dilated bowel acts as inherent
contrast. Venous access was obtained in the preparation room using the 16
or 18G venflon in the antecubital vein or any other large vein in the forearm.
The subjects were trained to hold their breath for at least 20 seconds if
possible, with special intention to avoid diaphragmatic motion.
With the help of pressure injector about 70-90 ml of Non-ionic
contrast, injected intravenously at flow rate of 2-3 ml /sec. Volume scans of
the abdomen and pelvis usually obtained with 5 mm collimation ,512x512
matrix, a pitch of 1.5 and 40-50 sec scan delay. Region of interest was from
the domes of diaphragm to the inferior edge of the ischium. Closer
reconstructions were done and viewed on the work station under wide
window setting namely soft tissue, bone and lung windows.
Thorax was also included in the study when needed (pulmonary
tuberculosis),in which case the region of interest was extended above up to
the sternal notch. Filming was done in soft tissue window. Thin
reconstructed axial sections were used to create sagittal, coronal and curved
multiplanar reformatted images from the acquired volume data, they have
more diagnostic value.27 The CT findings were correlated with intraoperative
findings on case to case basis. The following criteria were studied.
The CT criteria
Bowel Dilatation-Small bowel with a caliber greater than 2.5 cm
is considered dilated.
High grade obstruction is greater than 50% difference in caliber
of proximal dilated small bowel and collapsed distal small bowel.
Bowel wall thickening because of difficulties related to the
precision of this measurement, we have elected to use the 3mm
threshold suggested by Bartnicke.28
Delayed wall enhancement29 of the involved loop compared to
the homogenous enhancement of adjacent normal bowel.
Congestion of small mesenteric veins30,31 characterized by
enlargement of small serpentine vessels in the mesenteric fat.
Peritoneal fluid32,33
Bowel wall pneumatosis34 (intramural air) characterized by gas
bubbles within the bowel wall.
Statistical tools
The information collected regarding all the selected cases were
recorded in a master chart. Data analysis was done with the help of computer
using epidemiological information package (EPI 2002). Using this software,
frequencies, percentage, range, mean and strandard deviation were
calculated.
Sensitivity, specificity,. Accuracy, positive predictive valve and
negative predictive values were calculated using the following formulae and
taking surgical findings as the golden standard.
Sensitivity = True positive x 100
True positive + False negative
Specificity = True positive x 100
False positive + True negative
Accuracy = True positive x True negative
N
Positive predictive value = True positive x 100
True positive + False positive
Negative predictive value = True negative x 100
True negative + False negative
RESULTS AND ANALYSIS
Table 1 Age distribution
Frequency and percentage wise distribution of cases according to their
age:
Age group No. %
Table 2
Sex distribution
Frequency and percentage wise distribution of cases according to their
sex
Sex No. %
Male 37 44.6
Female 46 55.4
Total 83 100
Out of total 83 patients, 37 were males who constitute of about 44.6%
and 46 were females, that is around 55.4%.
Table 3
Frequency and percentage wise distribution of cases according to their
CT level of obstruction
CT-level No %
Proximal Jejunum 6 7.2
Distal jejunum 8 9.6
Proximal ileum 18 21.7
Distal ileum 50 60.2
Not clearly made out 1 1.2
Total 83 100
In among 83 cases, according to CT findings, distal ileum constitutes
(60.2%) the most common site of Small bowel Obstruction, 2nd commonest
site is proximal ileum (21.7%). Interestingly in one case, we could not made
out the site of obstruction , but intra operatively distal jejunum is the site of
obstruction.
Table 4
Frequency and percentage wise distribution of cases according to their
surgical level of obstruction
Surgical -level No %
Proximal Jejunum 5 6.0
Distal jejunum 11 13.3
Proximal ileum 18 21.7
Distal ileum 49 59.0
Total 83 100
According to Surgical findings, in 83 cases distal ileum constitutes
(59.0%) is the most common site of Small bowel Obstruction, 2nd
commonest site is proximal ileum (21.7%).
Table 5
Association between surgical and CT level of obstruction
Surgical_level
CT-Level
Proximal
jejunum
Distal
jejunum
Proximal
ileum
distal
ileum
Total p-value
Proximal
jejunum
5 1 0 0 6
p
Table 6
Frequency and percentage wise distribution of cases according to their
causes (surgical findings)
Causes No %
Adhesions 32 38.5
Stricture 14 16.8
Closed loop obstruction 24 28.9
Intussusception 1 1.2
Congenital iliac stenosis 1 1.2
Tumors 8 9.6
Radiation enteropathy 1 1.2
Meckels diverticulum 1 1.2
Foreign body 1 1.2
Total 83 100
In 83 cases, Adhesions (38.5%) are the most common cause of SBO. The
other causes are (in the descending order of frequency ) Closed loop
obstruction (28.9%), Stricture(16.8%), Neoplasms(9.6%).
Table 7
Frequency and percentage wise distribution of cases according to their
CT- ISCHAMIC Parameter of bowel wall enhancement
Bowel wall enhancement No %
Present 76 91.6
Absent 7 8.4
Total 83 100
In 83 patients, CT shows normal bowel enhancement in 76 cases, No
enhancement noted in 7 cases. One case showed poor enhancement, for
statistical purpose it was included in No enhancement category.
Table-8
Frequency and percentage wise distribution of cases according to their
bowel viability
Viability No %
Present 75 90.4
Absent 8 9.6
Total 83 100
Among 83 patients, intra operatively bowel was viable in 75 cases,
gangrenous bowel loops noted in 8 cases.
Table 9-
Bowel viability comparison of CT findings with surgical findings.
CT-
Finding
Surgical finding
p-value Viable Gangrene
f % f %
p
Table 10
Frequency and percentage wise distribution of cases according to their
confirmation of CT finding by surgical finding:
CT- Finding Confirmation with CT finding with Surgical
finding
Same as CT Not correlated with CT
f % f %
Level 78 93.9 5 6.1
Cause 77 92.8 6 7.2
Viability 80 96.4 3 3.6
There is a good correlation of CT findings with surgical findings in
respective of level, etiology and viability in cases of small bowel
obstruction.
DISCUSSION
Experience accumulated mainly in the past decade showing that CT
is a valuable diagnostic tool in cases of small bowel obstruction ,in its
diagnosis and evaluation of etiology.35,36,37 In our current study we want to
evaluate cases of small bowel obstruction , answering the following
clinical questions: Where is the Site of obstruction ,What is cause of the
obstruction, Is this bowel viable ?
In our prospective study of 83 cases of small bowel obstruction, most
common age group presented with small bowel obstruction is 50-60 years
with mean of 46.24 15.61 years, similar retrospective study of Omair
Shakil et al14 found mean age of 46 19 years which is more or less
co- inciding with our study.
In our study of 83 cases, 46 cases of female population which comprise 55.4
% of study population and 37 cases of male population, which comprise of
44.6%. Study by of Omair Shakil et al14 found to be males are affected
more, who comprise the 64% of study population.
In our study population of 83 patients the most frequent site of
obstruction is the distal ileum which comprise the 59% of study group (49
cases), next common (in descending order) are proximal ileum (21.7%),
distal jejunum (13.3%).The site of obstruction is correctly diagnosed in 78
cases with accuracy of 93.9%.
In 83 cases, most common cause of small bowel obstruction is adhesions,
comprise of 38.5% (32 cases)of study population, next common causes (in
descending order ) are closed loop obstruction 28.9% (24 cases),stricture due
to infection and inflammatory causes 16.8%(14 cases), Neoplasms 9.6%(8
cases).
The cause of small bowel obstruction is correctly identified in 77 cases with
accuracy of 92.8% , which is more accuracy than study by Omair Shakil et
al14 showed accuracy of 74% .Similar prospective study by Funda Obuz et
al17 showed helical CT has a sensitivity of 84% and specificity of 90% in
demonstrating the cause of obstruction.
In 32casese (38.5%)of adhesive small bowel obstruction , 29 patients
have history of abdominal surgery for various reasons and 2 patients have
recurrent appendicitis with inflammatory omental adhesions. Interestingly 1
patient have a thick encasing membrane with most of the small bowel loops
as its contents for which cause was not known and we included this case
under adhesions .Adhesions are commonly seen in people who undergone
laparotomy.38 The rates of adhesions varies with different studies .39,40 > 80%
adhesions occur after surgery,15% are due to inflammatory and remaining
few are due to congenital (or) unexplained causes.41 Adhesions are
responsible for more than half (50-75%) cases of small bowel
obstruction.42,43
We have 8 cases of neoplasms ( adenocarcinoma-6 cases,carcinoid-2
cases)present as small bowel obstruction. Among 6 cases of adenocarcinoma
three cases of adenocarcinoma present as growth with wall thickening,
another three cases of adenocarcinoma present as wall thickening with
narrowing ,these 3 cases pre-operative diagnosis is stricture, but
histopathology came as adenocarcinoma. We have one interesting case of
radiation enteropathy causing small bowel obstruction ,which is pre-
operatively diagnosed ,due to its characteristic appearance. We missed one
case of meckel s diverticulitis with band formation.
Closed loop obstruction is a form of mechanical bowel obstruction in
which two points along the course of the bowel are obstructed at a single
site.44 Closed loop obstruction is most often caused by an internal or external
hernia. In our study we found that closed loop obstruction is one of the
common cause for high grade small bowel obstruction, comprise of 28.9%
(24 cases)of study population.
Small bowel intussusception may because of various extrinsic,
intrinsic or intraluminal processes.45 Some times intussusception may cause
small bowel obstruction. We have one case of intussusception causing small
bowel obstruction and CT showed Jejuno-jejunal intussusception with
lymph nodes as lead point, histopathology came as chronic reactive lymph
nodes .
Foreign body usually seen in oesophagus, another sites are stomach, colon,
rarely can lodged in small intestine.46 Some times we can see small bowel
obstruction by foreign body, especially in children or mentally disturbed
patients.47 we have seen a case of foreign body (Jelly ball) Obstruction in 6
month old child after accidental swallowing jelly ball becomes swollen and
impacted in distal ileal loops.
A strangulating obstruction is defined as a mechanical obstruction
associated with bowel ischemia. This condition is seen in approximately
10% of patients with small bowel obstruction.Various CT findings are
described in cases of strangulation.48
In evaluation of bowel viability, our study correctly demonstrated
viability in 96.4%(80 cases) of study population with sensitivity of 98.7%,
specificity of 75%,positive predictive value of 97.4% and negative
predictive value of 85.7%. A similar prospective study by
Marc Zalcman et al16 showed CT correctly identified bowel ischemia in 23
cases with sensitivity of 96%, specificity of 93% in determining the bowel
viability. Another prospective study by Funda Obuz et al 17 6 cases with no
bowel enhancement in CT were confirmed with intraoperative findings .
In our case series three cases related to bowel viability was not
consistent with surgical findings. Two cases of bowel ischemia has been
missed ,one patient had a history of laparotomy for blunt injury abdomen 4
years back and we reported as closed loop obstruction with absence of
ischemic changes but preoperatively it turned to be a trans mesenteric hernia
with gangrenous changes. Since this patient was not responding to
conservative treatment and also showed clinical signs of strangulation he
was taken up for surgery i.e. Nearly 48 hours after the CT so, we presume
that he might have developed ischemic changes in his last few hours before
the surgery as closed loop obstruction is very notorious to go for acute
ischemic changes. Another case where we missed ischemia, is a case of
recurrent appendicitis with adhesions, initially conservatively management
tried in this case, likely delay in surgery or inflammatory changes may cause
ischemia in the meantime. In the third case we reported as small bowel
obstruction with ischemic changes because in our perception some of the
bowel loops shows inadequate enhancement but on contrary these bowel
loops were viable during surgery.
A study by Scaglione M et al 19 on bowel viability in cases of closed
loop small intestinal obstruction ,bowel ischemia was identified in 26 cases
with positive predictive value of 100%, negative predictive value of 73%.
Another study by Catel L et al20 on bowel viability in adhesive small bowel
obstruction, In 43 cases, CT identified strangulated bowel loops in 15
patients with accuracy of 90%, sensitivity of 71% and specificity of 100%.
A systematic review of many studies, CT for ischemia in SBO were
sensitivity of 83% (range, 63-100%), specificity of 92% (range, 61-100%),
PPV of 79% (range, 69-100%), and NPV of 93% (range, 33.3-100%).49
Some times, bowel ischemia can missed in spiral CT, patients with
obvious discrepancy between CT and clinical findings and ischemia of
bowel loops were suspected must undergo immediate surgery.50
In the present study, we conclude that the accuracy of helical CT in
the evaluation of level and cause of small bowel obstruction is 93.9% and
92.8% respectively. For evaluation of bowel viability with sensitivity of
98.7%, specificity of 75%,accuracy of 96.4%,positive predictive value of
97.4% and negative predictive value of 85.7%.
CONCLUSION
Helical CT is useful imaging modality to characterize the cause, site
and possible complications of small bowel obstruction .Reformatting
helical CT scans in multiple planes provides a new perspective for the
evaluation of small bowel obstruction and may be useful in defining and
characterizing obstruction. However, in most patients, the multiplanar
reconstructions simply confirm and complement the information revealed on
axial source images. Helical CT is a highly sensitive method to diagnose or
rule out intestinal ischemia in the context of acute small- bowel obstruction.
CT can also demonstrate findings that indicate the presence of closed loop
obstruction or strangulation, both of which necessitate emergency
exploratory laparotomy.
In our study population we found out that Helical CT has good
accuracy in determining the level, cause of obstruction, viability of bowel
loops ,and also absence of bowel wall enhancement is the most important
specific parameter to diagnose ischemic changes. Historically acute Small
bowel obstruction was surgically operated relatively early, because of
difficulty of identification severity, strangulation on clinical and
conventional imaging grounds. Today with improved diagnostic modalities
and resolution, some obstructions can resolve with conservative
management.51,52 We also strongly believe that Helical CT should be the first
imaging modality of choice in any case of acute small bowel obstruction
with clinical deterioration, because significant percentage of laparotomies
can be avoided if a reliable diagnosis of ischemia was possible
preoperatively.
Chart No .1
0
5
10
15
20
25
Chart No .2- Distribution of cases according to their sex.
0
5
10
15
20
25
30
35
40
45
50
No
.
Distribution of cases according to their sex.
Male Female
37
46
Sex
Distribution of cases according to their sex.
Chart No .3- Distribution of cases according to CT level of obstruction.
0
5
10
15
20
25
30
35
40
45
50
Proximal jejunum
6
No
.
Distribution of cases according to CT level of obstruction.
Proximal jejunum
Distal Jejunum
Proximal ileum
Distal ileum
Not clearly madeout
8
18
50
Distribution of cases according to CT level of obstruction.
Not clearly madeout
1
Chart No .4- Distribution of cases according to surgical level of
obstruction.
5
11
18
49
0
5
10
15
20
25
30
35
40
45
50
freq
uen
cy
Proximal
jejunum
Distal Jejunum Proximal ileum Distal ileum
Chart No.5- Distribution of cases according to their causes(Surgical
findings)
32
14
24
1 1 8
1 1 1
Adhesions
Stricture
Closed loop obstruction
Intussception
Congenital
Tumors
Radiation enteopathy
Meckel's diverticulum
Foreign body
Chart No .6- Distribution of cases according to CT ischemia
parameter of bowel wall enhancement.
0
10
20
30
40
50
60
70
80
Present
No
.
Distribution of cases according to CT ischemia
parameter of bowel wall enhancement.
Present Absent
76
7
Bowel wall Enhancement
Distribution of cases according to CT ischemia
Chart No .7- Distribution of cases according to their bowel viability .
0
10
20
30
40
50
60
70
80
No
.
Distribution of cases according to their bowel viability .
Present Absent
75
8
Distribution of cases according to their bowel viability .
Chart No .8 -Bowel viability
0
20
40
60
80
CT-
fin
din
gs f
req
uen
cy
Bowel viability -comparison of CT and surgical findings .
Viable Gangrene
74
21 6
Surgical findings
Viable
Gangrene
comparison of CT and surgical findings .
Viable
Gangrene
Chart No .9- Comparison of CT findings with surgical findings in terms
of level, cause of small bowel obstruction and bowel viability
0
10
20
30
40
50
60
70
80
Level
78
No
.
Comparison of CT findings with surgical findings in terms
of level, cause of small bowel obstruction and bowel viability
Level Cause Viability
78 77 80
5 6
Parameters
Comparison of CT findings with surgical findings in terms
of level, cause of small bowel obstruction and bowel viability
Viability
3
Same as CT
Not confirmation with CT
IMAGE 2- SCANOGRAM SHOWING THE DILATED SMALL BOWEL LOOPS.
Image 2
IMAGE 3- DILATED SMALL BOWEL LOOPS IN
CROSS SECTIONAL IMAGING
Image 3
IMAGES 4 A& B: 40 Year old gentle man , case of Ca. rectum -
post abdominoperineal resection(APR) , presented with small
bowel obstruction because of adhesions ( Arrow pointing to the
adhesions of bowel loops to pelvic side walls)
Image 4a
Image 4b
IMAGES 5a & 5b - 26 years old woman history of hysterectomy
presenting with small bowel obstruction because of adhesions (
Arrow pointing to adhesions to lower anterior abdominal wall
Image 5a
Image 5b
IMAGES 6a & 6b Adhesions with fat notch sign cross sectional
view (6a), coronal view (6b)
Image 6a
Image 6b
IMAGES 7a & 7b 46 year old gentle man presented with small
bowel obstruction showing Cocoon with encasing membranes &
adhesions ( arrows pointing to cocoon)
Image 7a
Image 7b
IMAGES 8a , 8b & 8c 36 year old gentle man presented with
small bowel obstruction showing Jejuno-jejunal intussusception
(arrows in image 8a pointing to sausage shaped mass , see fat and
vessels are surrounded by two layers of bowel loops ., Image 8b
showing target sign , Image 8c arrow pointing to lymph nodes
which act as lead point
Image 8a
Image 8b
Image 8c
IMAGES 9a , 9b & 9c 28 year old gentle man presented with small bowel obstruction showing Left femoral hernia with dilated bowel loops (Image 9c showing bowel loops in femoral triangle)
Image 9a
Image 9b
Image 9c
IMAGES 10a & 10b - 47 year old woman presented with small bowel obstruction showing Stricture as cause ( arrows pointing to
stricture)
Image 10a
Image 10b
IMAGES 11a & 11b - 69 year old male patients presented with small bowel obstruction showing Stricture as cause ( arrows
pointing to stricture)
Image-11a
Image-11b
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PROFORMA
NAME : AGE/SEX :
DATE : HOSP.NO :
ADDRESS :
COMPLAINTS & H/O PRESENT ILLNESS :
CO-MORBID FACTORS :
PREVIOUS SURGICAL HISTORY :
PLAIN RADIOGRAPHIC FINDINGS :
HELICAL CT FINDINGS :
Parameters for SBO :
Bowel dilatation
Level of SBO
Cause of SBO
Parameters for Associated Ischemia :
Bowel wall thickening
Bowel wall enhancement
Mesenteric congestion
Peritoneal fluid
Bowel wall pneumatosis
SURGICAL FINDINGS :
RECOMMENDATIONS
1. Helical CT should be the first imaging modality of choice in any case
of acute small bowel obstruction .
2. Always use I.V.Contrast studies to rule out bowel ischemia
3. If there is a disparity between CT findings and clinical situation,
deterioration of clinical condition always go for exploratory
laparotomy
4. Try to reduce radiation dosage to patient, by using new techniques&
different softwares.Try to get adequate information at a lower dose of
exposure.
5. Training doctors &CT technicians in management of contrast induced
side effects & emergencies.