Adult bowel obstruction with acute abdomen: spectrum of CT findings

Adult bowel obstruction with acute abdomen: spectrum of CT findings Poster No.: C-1571 Congress: ECR 2013 Type: Educational Exhibit Authors: L. Turturici, G. Gherarducci, F. Bianchi, R. Pascale, M. Tonerini, E. Orsitto; Pisa/IT Keywords: Emergency, Abdomen, CT, Conventional radiography, Contrast agent-intravenous, Image verification, Obstruction / Occlusion, Volvulus DOI: 10.1594/ecr2013/C-1571 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. www.myesr.org Page 1 of 32

Learning objectives To describe a tailored imaging work-up for the diagnosis of bowel obstruction in adult patients with acute abdomen, admitted to the Emergency Department. To report and discuss the computed tomography (CT) findings in bowel obstruction with reference to the site of occlusion, the causing factors and vascular complications or other conditions that require immediate surgical intervention. Background Bowel obstruction (BO) is a common clinical condition that occurs secondary to mechanical or functional obstruction of the bowel. It is a frequent cause of hospitalization and surgical consultation, representing 20% of all surgical admissions for acute abdominal pain. Bowel obstruction is defined as the obstacle to distal progression of intestinal contents and may be located in the small bowel (80%) or large bowel (20%). Causes of Obstruction The causes of bowel obstruction include extrinsic lesions, intrinsic lesions and intraluminal lesions. -Extrinsic causes include: adhesions, internal and external hernias, small bowel volvulus, colon volvulus, peritoneal carcinomatosis, carcinoid tumor, mesenteric lymphoma, endometriosis, inflammation of the surrounding structures as appendicitis and abscesses. -Parietal intrinsic causes include: intestinal neoplasms, intussusception, infectiousinflammatory disease, radiation enteritis, diverticulitis and intramural hematoma. -Intraluminal causes are: gallstone ileus, foreign bodies, fecal impaction and bezoars. The most common cause of small bowel obstruction are adhesions, while in large bowel is colon cancer followed by diverticulitis and sigma volvulus. Grade of Obstruction Page 2 of 32

Intestinal obstruction is defined as partial or complete depending on permitting the luminal passage of gas and intestinal content. Vascular Involvement On the basis of the vascular involvement intestinal obstruction is classified as simple (with an intact blood supply), closed-loop and strangulated. Closed-loop obstruction is a form of mechanical bowel obstruction in which a bowel loop is occluded in two adjacent points along its course (fig 1). It is mostly caused by an adhesive band and occasionally by an internal or external hernia. Because a closed-loop obstruction tends to involve the mesentery and to produce a volvulus, it represents the most common cause of strangulation. A strangulating obstruction is defined as a mechanical obstruction associated with bowel ischemia. This condition is seen in approximately 10% of patients with bowel obstruction and has a mortality rate of 20%-37%, compared with a rate of 5%-8% for a simple obstruction. Diagnosis of Bowel Obstruction The diagnosis is based on clinical signs, patient history, and radiographic findings. Clinical examination and laboratory values are often non-specific; symptoms can include crampy abdominal pain, vomiting, constipation, abdominal distension. The standard diagnostic work-up includes plain abdominal radiography, ultrasound and CT. Typically, conventional radiography is the first imaging procedure used in patients with bowel obstruction due to its wide availability and relatively low cost. However, radiographs are diagnostic in only 50%-60% of cases, equivocal in about 20%-30%, and normal, nonspecific, or misleading in 10%-20%. The abdominal radiographic signs that suggest bowel obstruction are the presence of air-fluid levels on upright or decubitus abdominal radiographs (fig2-4) and bowel distension (small with maximal dilated loops over 3 cm in diameter, the diameter of the transverse over 6 cm or the diameter of the cecum more than 9 cm). On ultrasound, BO is suspected if multiple dilated (>3 cm), fluid-filled loops are seen. The severity of the obstruction can also be assessed: presence of free fluid between dilated small bowel loops, aperistalsis, and wall thickening in a fluid-filled distended bowel segment suggests bowel infarction (fig 6). Bowel wall perfusion can also be assessed by Color-Doppler. However, with recent technologic developments, CT has been established as the modality of choice for imaging in suspected acute bowel obstruction. CT is recommended when clinical and initial radiographic findings remain indeterminate or strangulation is suspected. This modality clearly demonstrates the abdominal viscera and lesions of the Page 3 of 32

bowel as well as the pathologic processes around the bowel (involving the mesentery, vessels and peritoneal cavity) which cause obstruction. Management of Bowel Obstruction The treatment of choice depends on several factors: it is generally accepted that acute and complete obstruction requires immediate surgery, whereas partial obstruction can initially be managed conservatively unless there is an accompanying lesion that requires surgery (e.g. perforation, peritonitis). The risk of strangulation increases over time in patients with acute and complete obstruction. Strangulation constitutes an emergency and has a high mortality rate, particularly if surgery is delayed 36 hours or more from onset. Therefore radiology assumes considerable relevance in assisting the therapeutic decision of the surgeon in the early and accurate diagnosis of BO and influence the treatment selection, the morbidity and mortality rates. Bowel obstruction is a dynamic and ever-changing process. It can rapidly evolve into a catastrophic condition with ischemia or resolve by itself. In those cases, where surgical treatment is not immediate or advocated, it is necessary to maintain close communication between the surgeon and radiologist in order to guarantee the appropriate imaging and clinical follow-up. Images for this section: Page 4 of 32

Fig. 1: Closed-loop obstruction secondary to internal hernia: CT scan shows a radial distribution of small bowel loops with a C/U-shaped configuration and stretched mesenteric vessels converging toward torsion. Page 5 of 32

Fig. 2: Plain abdominal radiograph shows distension of colon and an air-fluid level with volvulus aspect. Page 6 of 32

Fig. 3: Plain abdominal radiograph shows distension of colon and an air-fluid level with volvulus aspect. Page 7 of 32

Fig. 4: Plain abdominal radiograph shows distension of small bowel loops and multiple air-fluid levels. Page 8 of 32

Fig. 5: Lateral abdominal radiograph shows distension of small bowel loops and multiple air-fluid levels. Page 9 of 32

Fig. 6: Ileal obstruction secondary to Crohn disease. Ultrasound of the ileum shows a dilated fluid-filled bowel loop with thickened bowel wall. Page 10 of 32

Imaging findings OR Procedure details CT plays a primary role in the evaluation of patients with acute BO for several reasons. CT is a fast, widely available and non invasive technique with a high sensitivity (81%-93%) and specificity (90%- 94%) for the diagnosis of intestinal obstruction. CT is superior to other imaging techniques (plain radiography, ultrasound)in identifying the site, level, cause, severity of bowel obstruction and any associated complications. CT can also demonstrate findings that indicate the presence of closed-loop obstruction or strangulation and so it is considered the best modality for determining which patients would benefit from conservative management and close follow-up and which patients would benefit from immediate surgical intervention. Finally CT can provide an alternative diagnosis for the patient with signs and symptoms of acute abdomen. CT Technique CT should be performed with intravenous injection of contrast material, because it highlights the abdominal viscera and lesions of the bowel as well as the pathologic process around the bowel, which causes obstruction. In addition bowel wall enhancement patterns are quite helpful in diagnosing bowel ischemia associated with obstruction. Intraluminal administration of contrast material may not be necessary because the fluid and gas retained in the dilated bowel loops provide negative contrast enhancement. Furthermore ischemic complications are more easily evaluated in the absence of oral contrast material. The acquisition of thinner slices and multiplanar reconstructions (sagittal, coronal, curved multiplanar reformatted images) may help to identify the site, level and cause of obstruction, improving CT sensitivity and specificity when axial findings are indeterminate. CT Findings of Bowel Obstruction CT criteria for the diagnosis of BO are the presence of dilated and air-fluid filled bowel loops proximally to collapsed bowel distally and the presence of a transition zone: a calibre change between the dilated proximal and collapsed distal bowel loops that identifies the level of obstruction. Complete versus partial obstruction of the small bowel is determined by the grade of distal collapse, proximal bowel dilatation and the amount of the residual contents in the portion of the bowel distal to the obstructed site. Other reliable features can include "beak sign" (fig 7), "whirl sign" (fig 8) and "small-bowel feces sign"(fig 9). CT findings indicating bowel ischemia include specific features of venous occlusion as thickening and increased enhancement of the affected bowel wall, engorged and Page 11 of 32

distended mesenteric vessels and intraperitoneal fluid; CT aspect of a vanished intestinal wall and pneumatosis intestinal in case of complete arterial occlusion. Other complications, such as perforation, can be identified on CT by the presence of extraluminal air. Results (fig 10-25) The exhibit shows the most relevant CT findings identified in one-hundred patients with clinical signs and symptoms of bowel obstruction. The site of obstruction was identified in the small bowel in 67 cases and in the large bowel in 33 cases (tab.1). Variable causes were recognized by CT and confirmed at surgery (tab.2): small bowel adhesions (n=39), volvulus (n=18), peritoneal carcinosis (n=13), occlusive colon cancer (n=12), gallstones (n=3), external hernia (n=3), diverticulitis (n=3), foreign bodies (n=2), intussusception (n=2), internal hernia (n=2), fecal impaction (n=1), carcinoid tumor (n=1) and complicated Crohn's disease (n=1). In 9 patients bowel obstruction was complicated by bowel ischemia. Images for this section: Page 12 of 32

Fig. 7: Beak sign: a fusiform tapering bowel loop at the point of torsion. Page 13 of 32

Fig. 8: Whirl sign: CT shows twisted and engorged mesenteric vessels and collapsed bowel. Page 14 of 32

Fig. 9: Small bowel-feces sign: gas bubbles mixed with particulate matter are observed in dilated small bowel loops proximal to an obstruction. Page 15 of 32

Fig. 10: Adhesive small bowel obstruction. Abdominal CT scan shows the transition zone, distended proximal bowel loops, and collapsed distal bowel loops. Multiplanar reformatted images clearly depict the site of obstruction: clustered small bowel loops with lumen stenosis. Page 16 of 32

Fig. 11: CT scan shows sigmoid volvulus. Page 17 of 32

Fig. 12: Coronal reconstruction shows sigmoid volvulus and the point of torsion. Page 18 of 32

Fig. 13: Coronal reconstraction shows volvulus of the small bowel and the exact point of torsion. Page 19 of 32

Fig. 14: CT scan shows small bowel obstruction associated with intestinal volvulus. Page 20 of 32

Fig. 15: Mechanical bowel obstruction caused by ovaric tumor disseminated in the peritoneal cavity. CT scans demonstrate dilated bowel loops and a tumor relapse in the pelvic cavity. Fig. 16: Large bowel obstruction caused by adenocarcinoma of the sigma-rectum. CT scan demonstrates dilatation of large bowel loops proximal to a stenotic mass lesion of the sigma-rectum. Page 21 of 32

Fig. 17: Gallstone ileus. Abdominal CT scan demonstrates dilated proximal bowel and a gallstone at the distal ileum. CT scans of the upper abdomen demonstrate gas in the biliary system and air-distended gallbladder, findings that are diagnostic for gallstone ileus. Page 22 of 32

Fig. 18: Esternal hernia. CT scan obtained at the inguinal level demonstrates herniated colon with diverticola and fluid in the left inguinal canal; proximal bowel loops are dilated. Fig. 19: CT scans show stenosis of the sigma with multi-diverticula aspect and distended proximal colon. Page 23 of 32

Fig. 20: Small bowel obstruction caused by intussusception produced by a calcified foreign body at the distal ileum. CT scans demonstrate intussuscepted distal ileum with a target-like appearance. Page 24 of 32

Fig. 21: Internal hernia. CT scans demonstrate a cluster of dilated and fluid-filled proximal ileum bowel loops with thickened oedematous wall and central displacement of the colon. A small amount of ascites is also present. Page 25 of 32

Fig. 22: Feacal impaction: CT MPR coronal view shows a voluminous fecolith at the level of the ascending colon with collapsed distal colon. Page 26 of 32

Fig. 23: Feacal impaction: CT scans show a voluminous fecolith at the level of the ascending colon with collapsed distal colon. Page 27 of 32

Fig. 24: Small bowel obstruction caused by carcinoid tumor of the distal ileum infiltrating the bowel wall. Fig. 25: Mechanical small bowel obstruction of the ileum in a patient with Crohn disease. CT scan shows dilated proximal loops and a transition zone, where the bowel wall is thickened and enhanced that indicate an active lesion. Page 28 of 32

Table 1 Page 29 of 32

Table 2 Page 30 of 32

Conclusion The practicing radiologists should be aware of the causes, location and complications of bowel obstruction, to render an effective and prompt CT diagnosis in the Emergency Department. CT is highly sensitive and specific in determining the presence of bowel obstruction and clearly demonstrates the site and cause of obstruction. The possibility of associated strangulation can be assessed with CT findings of bowel ischemia, particularly with intravenous contrast material use. CT is recommended for the evaluation of patients with suspected bowel obstruction, especially when clinical and initial conventional radiographic findings remain indeterminate or strangulation is suspected. References CT Evaluation of Small Bowel Obstruction. Mourad Boudiaf, Philippe Soyer,Carine Terem, Jean Pierre Pelage, Emmanuelle Maissiat and Roland Rymer. RadioGraphics 2001; 21:613-624 Small-Bowel Obstruction: Optimiziong Radiologic Investigation and Nonsurgical management. Dean D. T. Maglinte, Frederick M. Kelvin, Michael G. Rowe, Greg N. Bender, Dale M. Rouc. Radiology 2001; 218:39-46 Small-bowel obstruction: state-of the-art imaging and its role in clinical management. Maglinte DD, Howard TJ, Lillemoe KD, Sandrasegaran K, Rex DK Clin Gastroenterol Hepatol 2008;6(2):130-139 Multidetector row CT of small bowel obstruction. Qalbani A, Paushter D, Dachman AH Radiol Clin North Am 2007;45(3):499-512 Imaging of acute small-bowel obstruction. Page 31 of 32

Nicolaou S, Kai B, Ho S, Su J, Ahamed K. AJR Am J Roentgenol 2005;185(4):1036-1044 Abdominal wall hernias: MDCT findings. Aguirre DA, Casola G, Sirlin C. AJR Am J Roentgenol 2004;183(3):681-690 Personal Information Page 32 of 32