Chu, KW

Peh, WCG

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Title Radiological conference. Colonic obstruction due to sigmoidtumourAuthor(s) Peh, WCG; Chu, KWCitation Hong Kong Practitioner, 1997, v. 19 n. 3, p. 149-152Issued Date 1997URL http://hdl.handle.net/10722/44658Rights Creative Commons: Attribution 3.0 Hong Kong LicenseRADIOLOGICAL CONFERENCEClinical History:A 68-year-old man presented with a three-week history of abdominal pain and increasing constipation. He noticedweight loss of 10 pounds over this period and occasional bleeding per rectum. On examination, his abdomen wasdistended and diffusely tender, hyperactive bowel sounds were auscultated and blood staining was noted on rectalexamination. Supine (Figure 1) and erect (Figure 2) abdominal radiographs were performed.Figure 1: Supine abdominal x-ray Figure 2: Erect abdominal x-rayWhat is the diagnosis?a) Colonic obstruction due to sigmoid tumourb) Paralytic ileusc) Toxic megacolond) Sigmoid volvuluse) Small bowel obstruction secondary to adhesionsThis radiology case was prepared by: Dr. W.C.G. Peh, Associate Professor,Department of Diagnostic Radiology.Dr. K.W. Chu, Consultant,Department of Surgery,The University of Hong Kong,Queen Mary Hospital.149Radiological ConferenceRADIOLOGICAL CONFERENCEAnswer:a) Colonic obstruction due to sigmoid tumourRadiological findingsThe supine radiograph (Figure 3) shows loops ofair-filled dilated bowel distributed mainly around theperiphery of the abdomen. The bowel loops have ahaustral pattern. On the erect radiograph (Figure 4),air-fluid levels are seen within the dilated colon. Inboth radiographs, there is paucity of gas in the left iliacfossa, distal to the dilated descending and proximalsigmoid colon.Figure 3: Figure is identical to Figure 1 withaddition of arrows. Loops of dilatedcolon are distributed in the periphery ofthe abdomen (arrowheads). There is apaucity of gas at the site of obstruction(star)Figure 4: Figure is identical to Figure 2 withaddition of arrows. Air-fluid levels aredemonstrated within the bowel loops(arrows), indicative of obstructionDiscussionUrgent fibre-optic sigmoidoscopy confirmed thepresence of an obstructing tumour 15 cm from the analorifice. At laparotomy, a large rectosigmoid carcinomacausing gross colonic distension and obstruction wasfound. Tumour resection (Figure 5) and primaryanastomosis were performed. The patient made anuneventful recovery.The radiographic diagnosis of intestinal obstructiondepends on demonstration of dilated bowel loopsproximally, and collapsed or non-dilated bowel distal tothe point of obstruction. It is important to determinewhether the obstructed intestine is small or large bowel,or both types. Differentiating features includedistribution, size, number and markings of the bowel150Hong Kong Practitioner 19 (3) March 1997RADIOLOGICAL CONFERENCEloops. The dilated colon is usually distributed in theperiphery of the abdomen, exceeds 5 cm in width, andconsists of a few loops with a relatively large radius.Large bowel has haustra which often produces a thick,incomplete transverse band shadow across the bowel.1Figure 5: Resected specimen shows a largefungating tumour at the rectosigmoidjunction"•'*?!There are three recognized patterns of colonicobstruction, depending on the competency of theileocaecal valve.2 In type IA obstruction, the ileocaecalvalve is competent, with dilatation being confined to thelarge bowel. With time, the small bowel distendsprogressively against the closed ileocaecal valve, givingthe type IB appearance. The significance of both thesetype I obstructions is the massive caecal distensionproduced, with risk of ischaemia and perforation. Intype II obstruction, the ileocaecal valve is incompetent,hence back pressure from the colon leads to small boweldistension.2 The commonest cause of large bowelobstruction is carcinoma, 60% of which are situated inthe sigmoid colon.1Paralytic ileusParalytic ileus may be difficult to distinguish fromlarge bowel obstruction as fluid and gas alsoaccumulates in dilated small and large bowel in thiscondition. The pathogenesis is however due to cessationof peristalsis, which may be caused by a variety ofconditions. Common causes include post-operation,peritonitis and electrolyte imbalance.1 In our patient,this diagnosis can be excluded from the clinical historyand auscultatory findings.Toxic megacolonToxic megacolon is a fulminant form of colitiswhich carries an increased risk of morbidity andmortality. Radiographically, the bowel is grossly dilatedwith mucosal islands due to oedema and sloughing. Thepresence of intra-mural gas indicates imminentperforation.3 These changes are most often seen in thetransverse colon and were not present in our patient.Sigmoid volvulusSigmoid volvulus is classically caused by twistingof the sigmoid loop around its mesenteric axis, andusually occurs in an acute-on-chronic fashion.Radiographically, it forms a huge inverted U-shapedloop, with its apex being located under the lefthemidiaphragm or at the level of the 10th thoracicvertebra. The two limbs of the gas-filled ahaustral loopconverge inferiorly to the left iliac fossa. None of thesefeatures were present in this case.Small bowel obstruction secondary to adhesionsRadiographic changes usually develop within 3-5hours following small bowel obstruction. In contrast tocolonic obstruction, dilated loops of small bowel areusually distributed centrally in the abdomen, are 3-5 cmin diameter, consist of several loops with each having arelatively small radius, and have valvulae conniventes.1The erect radiograph shows hoop-shaped loops with151Radiological ConferenceOLOGICAL CONFERENCEmultiple air-fluid levels at various heights. A 'string-of-beads' appearance may be seen on the supine film, asa result of pockets of air trapped between the valvulaeconniventes in largely fluid-filled bowel. Mostobstructions in the small bowel are due to eitheradhesions or strangulated hernia.4 In our patient, thisdiagnosis can be excluded on clinical and radiographicgrounds. •ReferencesField S. The acute abdomen. In: Sutton D (ed). Textbook of Radiologyand Imaging. 4th ed. Churchil l Livingstone, Edinburgh. 1987; pp929-957.Love L. Large bowel obstruction. Semin. Roentgenol. 1973; 8: 299-322.Chapman S, Nakielny R. Aids to Radiological Differential Diagnosis.3rd ed. W.B. Saunders, London. 1995; pp 247.Bartram CI, Kumar P. The acute abdomen. In: Clinical Radiology inGastroenterology. Blackwell Scientific, Oxford. 1981; pp 217-220.CUMULATIVE HIV/AIDS STATISTICS IN HONG KONGSEX .|±J5i]ETHNICITY &ROUTES OF TRANSMISSIONUpdated 31 December, 1996Male gFemale -ChineseNon-ChineseSexual Contacts -|±ff •&PerinatalUndetermined ;f ifTOTAL &&Enquiries may be directed to the AIDS Unit (Telephone: 2780 8622)TOTALft*68393534242630462776(AIDS)j Ali(225)(20)(183)(62)(214)- Heterosexual $-44- Homosexual [5] 44- Bisexual ^44Injecting Drug Users :<iJftfi-&,^\±Blood/Blood Products Recipients389195461466(127)(67)(20)(4)(14)(2)(11)(245)152

Radiological conference. Colonic obstruction due to sigmoid tumour

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Radiological conference. Colonic obstruction due to sigmoid tumour

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