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Infaction and idiopathic inflammation of intraperitoneal fat. Implications of diagnostic imagingof the acute abdomen

van Breda Vriesman, A.C.

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Citation for published version (APA):van Breda Vriesman, A. C. (2004). Infaction and idiopathic inflammation of intraperitoneal fat. Implications ofdiagnostic imaging of the acute abdomen.

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Download date: 18 Oct 2020

CHAPTERR I

Generall introduction

100 CHAPTER 1

Background d

Thee term "acute abdomen" defines a pathologic abdominal condition mainly character-

izedd by severe abdominal pain of less than one week duration, requiring the clinician to

makee an urgent therapeutic decision (1). This maybe a challenging task, as the differen-

tiall diagnosis of acute abdominal pain includes an enormous spectrum of disorders,

rangingg from life-threatening diseases to benign self-limiting conditions (2). The indi-

catedd management may vary from emergency surgery, e.g. in a patient with a ruptured

abdominall aortic aneurysm, to reassurance of a patient with abdominal pain from

gastroenteritis.. Clinical misjudgement of serious conditions may result in increased

morbidityy and mortality, if the necessary surgery or medical treatment is delayed. On

thee other hand, misdiagnosis in a patient with a nonsurgical or a self-limiting disease

mayy lead to an unwarranted laparotomy, unnecessary medical treatment or hospitaliza-

tion.. A timely and accurate diagnosis is essential to avoid these unfortunate conse-

quencess (2).

Clinicall assessment of patients with acute abdominal pain can be notoriously difficult,

becausee the history, physical examination and laboratory findings in these patiens are

oftenn nonspecific and nondiagnostic. Various acute abdominal conditions may present

withh identical findings at clinical presentation; while self-limiting diseases may simulate

surgicall emergencies, inversely, surgical conditions may occasionally mimic a benign ill -

ness.. An accurate clinical diagnosis can be made in only about 50% of patients with acute

abdominall pain (3).

Inn search of means to increase the diagnostic accuracy in patients with acute abdom-

inall pain, ultrasonography (US) and computed tomography (CT) have proven to be use-

full and cost-effective tools, enabling a rapid triage of patients towards optimal therapy

(2-5).. With US or CT, a clinically presumed diagnosis can both be confirmed or exclud-

ed,, and the full extent of the disease and the presence or absence of possible complica-

tionss can be established. Furthermore, follow-up US or CT enables a close monitor of

diseasee activity, allowing the natural course of a disease to be followed. Today, in many

hospitalss US and CT are routinely used in the evaluation of patients with abdominal

painn of unknown cause.

Thiss increased use of abdominal US and CT has brought new insights concerning the

incidencee and nature of several disorders that were rarely diagnosed in the era before

modernn imaging (5). In former days, these disorders would typically be diagnosed only

iff an exploratory laparotomy would be performed, and as a result their true frequency

andd natural history were not known. Now, due to modern diagnostic imaging, these dis-

Lig.. falciforme (hepatis)

Parss pylorica

Lobuss hepatis sin.

Lobuss hepatis dexter

Lig.. teres hepatis (V.. umbilicalis)

Fundus s vesicaee biliaris

M.M. transv.abdominis

Taeniaa omentalis

Taeniaa libera. Colonn ascendens

Curvaturaa gastnca (ventriculi] major

Corpuss gastncum (ventriculare]

MM rectus abdominis

/ /

vvv ! w p / « f f ' y

Ligg gastrocohcum

Omentumm majus

transv.. abdominis

M.. obliquus int. abdominis s

M.. obliquus ext. abdominis s

Colonn sigmoideum

Peritoneun n parietale e

Plicaa umbilicalis lat. (A.,, V.epigastrica inf.)

Lineaa arcuata

Plicaa umbilicalis med. (A.. umbilicalis, Pars occlusa)

Plicaa umbilicalis mediana (Urachus)

Fig.. 1 The greater omentum, and abdominal viscera (from Ref. 6).

Liver r (rightt lobe)

Falciform m ligament t

Gallbladder r

Transverse e colon n

Epiploic c appendage e

Ascending g colon n

Liver r (leftt lobe)

Greater r omentum m

Fig.. 2 Ventral abdominal view at obduction. The omentum, an epiploic appendix

(appendage),, and viscera.

IntroductionIntroduction 13

easess are more frequently encountered, and it has become possible to estimate their inci-

dencee and assess their clinical characteristics. Prominent examples of these 'rediscovered'

diseasess are omental infarction, epiploic appendagitis, and mesenteric panniculitis. These

disorderss further have in common that all three comprise an aseptic inflammation of

intraperitoneall fat, due to infarction or idiopathic, with an imaging diagnosis that is

essentiallyy based on the detection of inflamed fat without any primary intestinal inflam-

matoryy focus (such as the appendix or a colonic diverticulum).

Anatomy Anatomy

Thee omentum, epiploic appendices, and the mesentery are all composed of peritoneum,

andd represent the three main sites of fat deposition within the peritoneal cavity.

Omentum Omentum

Thee greater omentum is a large peritoneal fold, hanging down from the greater curvature

off the stomach sometimes as low as the pelvis, lying in front of the intestines {Fig 1, 2)

(6).. The posterior aspect of the omentum is attached to the transverse colon. The omen-

tumm is composed of a double sheet of peritoneum, which is partly folded on itself to

makee four layers (Fig 3). It contains gastroepiploic vessels, lymphatics, and adipose tis-

suee which may be massive in amount in obese individuals.

Thee omentum serves mainly as a fat storage, for energy consumption during periods

off malnourishment. Furthermore, it appears to have an ability to move toward areas of

inflammationn or perforation of the intestinal tract. By taking part in the inflammatory

process,, it helps to seal off and limit intra-abdominal disease. Because of this remarkable

property,, the omentum has once been nicknamed 'policeman of the abdomen' (7).

EpiploicEpiploic appendices

Epiploicc appendices are small pedunculated pouches of visceral peritoneum filled with

fat,, protruding from the external surface of the colon into the peritoneal cavity (Fig 2,4,

5)) (6). Most are about 1-2 cm thick and 2-5 em long, and normally approximately 50-100

epiploicc appendices are present, distributed from the rectosigmoid junction to the

LesserLesser omentum in fissure forfor ligamentum venosum

CaudateCaudate lobe of liver

LesserLesser omentum

EpiploicEpiploic foramen

HepaticHepatic artery

NeckNeck of pancreas

Stomach Stomach

UncinateUncinate process of headhead of pancreas

Duodenum,Duodenum, horizontal part

TransverseTransverse mesocolon adher-entent to posterior layers of greatergreater omentum

TransverseTransverse colon

Mesentery Mesentery

GreaterGreater omentum

Fig.. 3 Diagrammatic median sagittal section of the abdomen.

{ { A.,, V colica media

Recessus s ileocaecaliss mf

i i

'ancreas.. Facies inf.

Fexuraa coli sin.

Recessus s duodenales s supp et inf.

Ren.. Extremitas inf., Ureter r

Sulcii paracolici

Colonn sigmoideum. Mesocolonn sigmoideum

Resessus s intersigmoideus s

Meso-appendix.. Appendix vermiformis

Epiploicc appendices

Fig.. 4 Epiploic appendices, the mesentery, and abdominal viscera (from Ref. 6).

M M

Fig.. 5 Norma] epiploic appendices, on a resected part ol the colon.

IntroductionIntroduction 17

cecum.. Each epiploic appendix is supplied by one or two small eödarteries branching

fromfrom the vasa recta longa of the colon, and is drained by a vein twisting around the artery,

bothh passing through its narrow pedicle (8).

Epiploicc appendices are absent in many animal species, including dogs and cats, and

theirr exact function is unknown. Similar to the omentum, they mainly serve as a fat stor-

age,, however, it has been been postulated that epiploic appendices might also act as pro-

tectivee cushions for the large intestine, facilitating bowel peristaltis. They probably also

providee some local defense agains inflammation, similar to the protective actions of the

omentumm (8).

Mesentery Mesentery

Thee mesentery is a fen-shaped» double peritoneal fold that suspends ileal and jejunal

smalll bowel loops from the posterior abdominal wall (Fig 3,4) (6). It contains fatty tis-

sue,, nerves, vascular and lymphatic structures, and encases the bowel loops that it sup-

ports,, forming the visceral peritoneal coat.

Pathology Pathology

OmentalOmental infarction

Bush,, in 1896, was the first to describe infarction of the greater omentum (9). Omental

infarctionn can be caused by mechanical torsion of an omental segment, or it may be pri-

maryy idiopathic, i.e. without known etiology, occurring spontaneously. Because omental

infarctionn is primarily venous and characteristically right-sided, it has been suggested

thatt some anatomical malformation involving the right portion of the omental venous

drainagee may predispose to kinking and thrombus formation (10).

Variouss authors have attempted to differentiate omental torsion from idiopathic seg-

mentall infarction, implying a different pathological concept, but these disorders are now

consideredd to be variants of the same disease (7). In either case, obstruction or throm-

bosiss of the omental venous drainage results in congestion with hemorrhagic extravasa-

tion,, fat necrosis, and a secondary inflammatory response (7,10).

188 CHAPTER 1

EpiploicEpiploic appendagitis

Thee pathological significance of epiploic appendices was first described by Virchow, in

18633 (11). He rightly suggested that a loose foreign body, which he had found in the peri-

toneall cavity at autopsy, was a calcified and detached epiploic appendix, representing the

sequelaa of infarction. In 1908, the first description of a surgically proven case of an

infarctedd epiploic appendix appeared in the English literature, by Briggs (11).

Infarctionn may occur when an epiploic appendix twists along its narrow pedicle,

strangulatingg its own blood supply. Although the actual twist of an epiploic appendix has

beenn demonstrated at surgery in only a minority of cases (31%), and infarction may also

occurr due to spontaneous venous thrombosis, it is generally accepted that torsion or

kinkingg of the pedicle is the most important cause of infarction (12).

Afterr the blood supply of an epiploic appendix has been compromised, a cascade of

eventsevents takes place similar to that in omental infarction; leading from venous congestion,

hemorrhagee and necrosis, to secondary inflammatory changes (12). In view of this sec-

ondaryy inflammation, and in order to avoid confusion with appendicitis, infarction of an

epiploicc appendix has been renamed 'epiploic appendagitis'. In a later phase, necrotic tis-

suee is replaced by fibrosis and calcification, and the infarcted epiploic appendix may

detachh forming an intraperitoneal loose body mentioned above, which some have com-

paredd to a 'hard boiled egg' (13) or referred to as a 'peritoneal mouse' (14).

MesentericMesenteric panniculitis

Mesentericc panniculitis is a relatively new entity, first described by Ogden in 1960 (15).

Itt is defined as a nonspecific aseptic inflammation of the adipose tissue of the mesentery,

andd its exact cause is unknown. It has been suggested that mesenteric panniculitis prob-

ablyy does not represent one specific disease, but rather the result of injury to the mesen-

tericc fat which may be inflicted in various ways (.16). In this respect it may somewhat be

comparedd to retroperitoneal fibrosis, which may also occur as a response to various pri-

maryy causes.

Inn rare instances the inflammation in mesenteric panniculitis may proceed to fibrosis

withh retraction of the mesenteric fat, which is then termed fibrosing -, sclerosing -, or

retractilee mesenteritis.

IntroductionIntroduction 19

Thee objectives of this thesis are

-- To asses the clinical features of omental infarction and epiploic appendagitis, and

too determine their natural history.

-- To report diagnostic imaging findings of omental infarction and epiploic

appendagitis,, and to provide an imaging-based differential diagnosis.

-- To assess clinical findings in patients with mesenteric panniculitis while reporting

itss US and CT features, and to record possible associated conditions.

-- To evaluate the use of US with complementary CT in patients with presumed

appendicitis. .

Outlinee of the thesis

Inn chapter 2 the clinical characteristics and natural history of omental infarction and epi-

ploicc appendagitis are studied. This chapter also provides a literature-based review of the

USS and CT features of both disorders. In chapter 3 a general review of omental infarc-

tionn and epiploic appendagitis is presented. Chapter 4 provides an imaging based differ-

entiall diagnosis of omental infarction and epiploic appendagitis. A characteristic imag-

ingg sign of epiploic appendagitis is presented in chapter 5. Chapter 6 comprises two case

reports;; part A reporting an imaging pitfall, due to an old and new infarction of an epi-

ploicc appendix, and part B reporting the features of epiploic appendagitis at MR. In

chapterr 7 the clinical findings and natural course of epiploic appendagitis are studied,

fromfrom a patientgroup much larger than in chapter 2. In chapter 8 clinical findings in

patientss with US and CT features of mesenteric panniculitis are evaluated, and possible

associatedd diseases are recorded.

Right-sidedd epiploic appendagitis or omental infarction clinically often simulates

appendicitis.. In chapter 9 the value of routine diagnostic imaging in patients clinically

suspectedd of having appendicitis is investigated, using a tandem US and CT technique.

Chapterr 10 presents the summary and conclusions.

References s

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200 CHAPTER 1

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5.. Puylaert JBCM. When in doubt, sound it out. Radiology 1994;191:320-321

6.. Stauhesand J. Sóbotta Atlas of human anatomy, 11th ed. Baltimore: Urban & Schwartzenberg* 1989

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