Intestinal obstruction Definition : arrest of downward propulsion of intestinal content Classification : according to : A)pathological cause: 1)simple intestinal obstruction 2) strangulated intestinal obstruction B)level of obstruction: 1) high small intestinal obstruction 2) low small intestinal obstruction 3) large intestinal obstruction C)onset and course of obstruction 1) acute 2)chronic D) mechanical Vs Adynamic E) complete Vs incomplete ;
Transcript
Slide 1
Definition : arrest of downward propulsion of intestinal
content Classification : according to : A)pathological cause:
1)simple intestinal obstruction 2) strangulated intestinal
obstruction B)level of obstruction: 1) high small intestinal
obstruction 2) low small intestinal obstruction 3) large intestinal
obstruction C)onset and course of obstruction 1) acute 2)chronic D)
mechanical Vs Adynamic E) complete Vs incomplete ;
Small intestinal ileus is the most common form of intestinal
obstruction; it occurs after most abdominal operations and is a
common response to acute intra abdominal inflammatory conditions
Mechanical small bowel obstruction is somewhat less common; such
obstruction is secondary to intra-abdominal adhesions, hernias, or
cancer Mechanical colonic obstruction most often develops in
response to obstructing carcinoma, diverticulitis,or volvulus.
Acute colonic pseudo-obstruction occurs most frequently in the
postoperative period or in response to another acute medical
illness.
Slide 4
When the bowel is occluded at a single point along the
intestinal tract, simple obstruction is present. When a segment of
bowel is occluded at two points along its course by a single
constrictive lesion that occludes both the proximal and the distal
end of the intestinal loop as well as traps the bowels mesentery,
closed-loop obstruction is present. When the blood supply to a
closed-loop segment of bowel becomes compromised, leading to
ischemia and eventually to bowel wall necrosis and perforation,
strangulation is present. The most common causes of simple
obstruction are intra- abdominal adhesions, tumors, and strictures.
The most common causes of closed-loop obstruction are hernias,
adhesions, and volvulus.
Simple distal to obstruction proximal peristalsis blind loop
Strangulation General effect fluid and electrolyte loss
septicaemia
Slide 7
Early in the course of an obstruction, intestinal motility and
contractile activity increase in an effort to propel luminal
contents past the obstructing point. Later in the course of
obstruction, the intestine becomes fatigued and dilates, 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.
Slide 8
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 a twist of the bowel, can progress to arterial
occlusion and ischemia if left untreated and may potentially lead
to bowel perforation and peritonitis. Bacteria translocating to
mesenteric lymph nodes and even systemic organs.However, the
overall importance of this bacterial translocation on the clinical
course has not been entirely defined.
Slide 9
Cardinal symptom Pain, Distention, Vomiting, Absolute
constipation The nature of the presentation will be influenced by
the site In high small bowel obstruction, vomiting occurs early and
is profuse with rapid dehydration. Distension is minimal with
little evidence of fluid levels on abdominal radiography In low
small bowel obstruction, pain is predominant with central
distension. Vomiting is delayed. Multiple central fluid levels are
seen on radiography In large bowel obstruction, distension is early
and pronounced. Pain is mild and vomiting and dehydration are late.
The proximal colon and caecum are distended on abdominal
radiography The nature of the presentation will also be influenced
by whether the obstruction is: acute; chronic; acute on chronic;
subacute. Acute obstruction usually occurs in small bowel
obstruction, with sudden onset of severe colicky central abdominal
pain, distensionand early vomiting and constipation Chronic
obstruction is usually seen in large bowel obstruction, with lower
abdominal colic and absolute constipation followed by distension.
In acute on chronic obstruction there is a short history of
distension and vomiting against a background of pain and
constipation. Subacute obstruction implies an incomplete
obstruction. Presentation will be further influenced by whether the
obstruction is: simple in which the blood supply is intact;
strangulating/strangulated Examination General, Abdominal
inspection, palpation,percussion, auscultation
Slide 10
The typical crampy abdominal pain associated with intestinal
obstruction occurs in paroxysms at 4- to 5-minute intervals and
occurs less frequently with distal obstruction. It is usually
centred on the umbilicus (small bowel) or lower abdomen (large
bowel). With increasing distension, the colicky pain is replaced by
a mild constant diffuse pain. The development of severe persistant
pain is indicative of the presence of strangulation. Pain may not
be a significant feature in postoperative simple mechanical
obstruction and does not usually occur in paralytic ileus. Nausea
and vomiting are more common with a higher obstruction and may be
the only symptoms in patients with gastric outlet or high
intestinal obstruction. An obstruction located distally is
associated with less emesis, and the initial and most prominent
symptom is the cramping abdominal pain. As obstruction progresses
the character of the vomitus alters from digested food to faeculent
material, as a result of the presence of enteric bacterial
overgrowth. In the small bowel the degree of distension is
dependent on the site of the obstruction and is greater the more
distal the lesion. Visible peristalsis may be present. Distension
is delayed in colonic obstruction and may be minimal or absent in
the presence of mesenteric vascular occlusion. Constipation may be
classified as absolute (i.e. neither faeces nor flatus is passed)
or relative (where only flatus is passed). Absolute constipation is
a cardinal feature of complete intestinal obstruction. Some
patients may pass flatus or faeces after the onset of obstruction
as a result of the evacuation of the distal bowel contents. The
rule that constipation is present in intestinal obstruction does
not apply in: Richters hernia; gallstone obturation; mesenteric
vascular occlusion; obstruction associated with pelvic abscess;
partial obstruction (faecal impaction/colonic neoplasm) in which
diarrhoea may often occur.
Slide 11
The patient with intestinal obstruction may present with
tachycardia and hypotension, demonstrating the severe dehydration
that is present. Fever suggests the possibility of strangulation.
Abdominal examination demonstrates a distended abdomen, with the
amount of distention some what dependent on the level of
obstruction. Previous surgical scars should be noted. Early in the
course of bowel obstruction, peristaltic waves can be observed,
particularly in thin patients, and auscultation of the abdomen may
demonstrate hyperactive bowel sounds with audible rushes associated
with vigorous peristalsis (i.e., borborygmi). Late in the
obstructive course, minimal or no bowel sounds are noted. Mild
abdominal tenderness may be present with or without a palpable
mass; however, localized tenderness, rebound, and guarding suggest
peritonitis and the likelihood of strangulation. A careful
examination must be performed to rule out incarcerated hernias in
the groin, the femoral triangle, and the obturator foramen. A
rectal examination should be performed to assess for intraluminal
masses and to examine the stool for occult blood, which may be an
indication of malignancy, intussusception, or infarction.
Slide 12
Classic picture of strangulation include tachycardia, fever,
leukocytosis, and a constant, noncramping abdominal pain.
Tenderness with rigidity, Shock,With the cardinal signs of
intestinal obstruction In cases of intestinal obstruction in which
pain persists despite conservative management, even in the absence
of the above signs, strangulation should be diagnosed. When
strangulation occurs in an external hernia, the lump is tense,
tender and irreducible, there is no expansile cough impulse and it
has recently increased in size. Pathology The venous return is
compromised before the arterial supply. The resultant increase in
capillary pressure leads to local mural distension with loss of
intravascular fluid and red blood cells intramurally and
extraluminally. Once the arterial supply is impaired, haemorrhagic
infarction occurs. As the viability of the bowel is compromised
there is marked translocation and systemic exposure to anaerobic
organisms with their associated toxins. The morbidity of
intraperitoneal strangulation is far greater than with an external
hernia, which has a smaller absorptive surface. Causes of
strangulation External: Hernial orifices Adhesions/bands
Interrupted blood flow Volvulus Intussusception Increased
intraluminal pressure Closed-loop obstruction Primary Mesenteric
infarction
Slide 13
This occurs when the bowel is obstructed at both the proximal
and distal points. It is present in many cases of intestinal
strangulation. Unlike cases of non-strangulating obstruction, there
is no early distension of the proximal intestine. When gangrene of
the strangulated segment is imminent, retrograde thrombosis of the
mesenteric veins results in distension on both sides of the
strangulated segment. A classic form of closed-loop obstruction is
seen in the presence of a malignant stricture of the right colon
with a competent ileocaecal valve (present in up to one-third of
individuals). The inability of the distended colon to decompress
itself into the small bowel results in an increase in luminal
pressure, which is greatest at the caecum, with subsequent
impairment of blood supply. Unrelieved, this results in necrosis
and perforation
Slide 14
Plain X ray of the abdomen: Radiological features of
obstruction The obstructed small bowel is characterised by straight
segments that are generally central and lie transversely. No gas is
seen in the colon The jejunum is characterised by its valvulae
conniventes, which completely pass across the width of the bowel
and are regularly spaced, giving a concertina or ladder effect
Ileum the distal ileum has been described as featureless Caecum a
distended caecum is shown by a rounded gas shadow in the right
iliac fossa Large bowel, except for the caecum, shows haustral
folds, which, unlike valvulae conniventes, are spaced irregularly,
do not cross the whole diameter of the bowel and do not have
indentations placed opposite one another Blood urea and electrolyte
Blood picture U.S. CT scan Endoscopy
Slide 15
The treatment is urgent relief of obstruction after preparation
Preoperative preparation ( fluid and electrolyte
replacement,antibiotics and Tube Decompression ) Operation
:exploration Immediate operation indicated in peritonitis,
incarcerated hernia, suspected or confirmed strangulation, sigmoid
volvulus with systemic toxicity or peritoneal irritation, small
bowel volvulus, colonic volvulus above sigmoid, Conservative (with
exeption) indication 1)Adhesive 2)Ileocaecal itussusception
3)Sigmoid volvuls 4)feacal impaction Reassess patient every 4 hr.
Look for changes in pain, abdominal findings, and volume and
character of NG aspirate. Repeat abdominal x-rays, and look for
changes in gas distribution, pneumatosis cystoides intestinalis,
and free intraperitoneal air. Classify patients condition as
improved, unchanged, or worse. Decide whether operative treatment
is necessary and, if so, whether it should be done on urgent or
elective basis. Urgent operation Indications include: Lack of
response to 2448 hr of nonoperative therapy (increasing abdominal
pain, distention, or tenderness; NG aspirate changing from
nonfeculent to feculent; proximal small bowel distention with
distal gas).
Slide 16
Patients with intestinal obstruction are usually dehydrated and
depleted of sodium, chloride, and potassium, requiring aggressive
intravenous replacement with an isotonic saline solution such as
lactated Ringers. Urine output should be monitored by the placement
of a Foley catheter. After the patient has formed adequate urine,
potassium chloride should be added to the infusion if needed.
Serial electrolyte measurements, as well as hematocrit and white
blood cell count, are performed to assess the adequacy of fluid
repletion. Because of large fluid requirements, patients,
particularly the elderly, may require central venous assessment
and, in some cases, the placement of a Swan-Ganz catheter.
Broad-spectrum antibiotics are given prophylactically by some
surgeons based on the reported findings of bacterial translocation
occurring even in simple mechanical obstructions. In addition,
antibiotics are administered as a prophylaxis for possible
resection or inadvertent enterotomy at surgery.
Slide 17
Nasogastric suction empties the stomach, reducing the hazard of
pulmonary aspiration of vomitus and minimizing further intestinal
distention from preoperatively swallowed air. Patients with
adhesive simple intestinal obstruction may be treated
conservatively with resuscitation and tube decompression alone.
Resolution of symptoms and discharge without the need for surgery
have been reported in 60% to 85% of patients with an adhesive
simple intestinal obstruction. Although an initial trial of
nonoperative management of most patients with partial small bowel
obstruction is warranted, it should be emphasized that clinical
deterioration of the patient or increasing small bowel distention
on abdominal radiographs during tube decompression warrants prompt
operative intervention. The decision to continue to treat a patient
nonoperatively with a presumed bowel obstruction is based on
clinical judgment and requires constant vigilance to ensure that
the clinical course has not changed.
Causes of Ileus Post laparotomy Metabolic and electrolyte
derangements (e.g., hypokalemia, hyponatremia, hypomagnesemia,
uremia, diabetic coma) Drugs (e.g., opiates, psychotropic agents,
anticholinergic agents) Intra-abdominal inflammation
Retroperitoneal hemorrhage or inflammation Intestinal ischemia
Systemic sepsis
Slide 20
Abdominal distention, usually without the colicky abdominal
pain, is the typical and most notable finding. Nausea and vomiting
may occur. Plain abdominal radiographs may reveal distended small
bowel as well as large bowel loops. The treatment of an ileus is
entirely supportive with nasogastric decompression and intravenous
fluids. The most effective treatment to correct the underlying
condition may be aggressive treatment of the sepsis, correction of
any metabolic or electrolyte abnormalities, and discontinuation of
medications that may produce an ileus. Pharmacologic agents have
been used but for the most part have been ineffective. Drugs that
block syinput (e.g., guanethidine) or stimulate parasympathetic
activity (e.g., bethanechol or neostigmine) have been tried. In
addition, hormonal manipulation, using cholecystokinin or motilin,
has been evaluated, but the results have been inconsistent.
Slide 21
Factors associated with pseudo-obstruction Idiopathic Metabolic
Diabetes, intermittent porphyria,Acute hypokalaemia,
Uraemia,Myxodoema Severe trauma (especially to the lumbar spine and
pelvis) Shock Burns Myocardial infarction Stroke Septicaemia
Retroperitoneal irritation by : Blood,Urine,nzymes
(pancreatitis),Tumour Drugs,Tricyclic
antidepressants,Phenothiazines,Laxatives Secondary gastrointestinal
involvement, Scleroderma,Chagas disease
Slide 22
Mesenteric vascular disease may be classified as acute
intestinal ischaemia with or without occlusion venous, chronic
arterial, central or peripheral. The superior mesenteric vessels
are the visceral vessels most likely to be affected by embolisation
or thrombosis, with the former being most common. Occlusion at the
origin of the superior mesenteric artery (SMA) is almost invariably
the result of thrombosis, whereas emboli lodge at the origin of the
middle colic artery. Inferior mesenteric involvement is usually
clinically silent because of a better collateral circulation.
Possible sources for the embolisation of the SMA include a left
atrium associated with fibrillation, a mural myocardial infarction,
an atheromatous plaque from an aortic aneurysm and a mitral valve
vegetation associated with endocarditis. Primary thrombosis is
associated with atherosclerosis and thromboangitis obliterans.
Primary thrombosis of the superior mesenteric veins may occur in
association with factor V Leiden, portal hypertension, portal
pyaemia and sickle cell disease and in women taking the
contraceptive pill. Irrespective of whether the occlusion is
arterial or venous, haemorrhagic infarction occurs. The intestine
and its mesentery become swollen and oedematous. Blood- stained
fluid exudes into the peritoneal cavity and bowel lumen. If the
main trunk of the SMA is involved, the infarction covers an area
from just distal to the duodenojejunal flexure to the splenic
flexure. Usually, a branch of the main trunk is implicated and the
area of infarction is less.
Slide 23
The most important clue to an early diagnosis of acute
mesenteric ischaemia is the sudden onset of severe abdominal pain
in a patient with atrial fibrillation or atherosclerosis. The pain
is typically central and out of all proportion to physical
findings. Persistent vomiting and defaecation occur early, with the
subsequent passage of altered blood. Hypovolaemic shock rapidly
ensues. Abdominal tenderness may be mild initially with rigidity
being a late feature. Investigation will usually reveal a profound
neutrophil leucocytosis with an absence of gas in the thickened
small intestine on abdominal radiographs. The presence of gas
bubbles in the mesenteric veins is rare but pathognomonic.
Slide 24
Treatment needs to be tailored to the individual. In
conjunction with full resuscitation, embolectomy via the ileocolic
artery or revascularisation of the SMA may be considered in early
embolic cases. The majority of cases, however, are diagnosed late.
All affected bowel should be resected. Anti-coagulation should be
implemented early in the postoperative period. After extensive
enterectomy it is usual for patients to require intravenous
alimentation. The young, however, may sometimes develop sufficient
intestinal digestive and absorptive function to lead relatively
normal lives. In selected cases consideration may be given to small
bowel transplantation.
Slide 25
Infarction of the large intestine alone is relatively rare.
Involvement of the middle colic artery territory should be treated
by transverse colectomy and exteriorisation of both ends, with an
extended right hemicolectomy in selected cases. Ischaemic colitis
describes the structural changes that occur in the colon as a
result of the deprivation of blood. They are most common in the
splenic flexure, whose blood supply is particularly tenuous. They
have been classified by Marston into gangrenous, transient and
stricturing forms; only stricturing forms cause obstruction and
only a few such patients require resection.