Small Bowel Obstruction

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1 Residents Section Pattern of the Month Small owel Obstruction Residents Section Pattern of the Month Downloaded from by on 12/16/17 from IP address Copyright RRS. For personal use only; all rights reserved Residents inradiology Charles P. Mullan 1 ettina Siewert Ronald L. Eisenberg Mullan CP, Siewert, Eisenberg RL Keywords: bowel, obstruction, small bowel DOI: /JR Received May 25, 2010; accepted after revision May 16, ll authors: Department of Radiology, eth Israel Deaconess Medical Center, Harvard Medical School, 330 rookline ve, oston, M ddress correspondence to R. L. Eisenberg (rleisenb@bidmc.harvard.edu). WE This is a Web exclusive article. JR 2012; 198:W105 W X/12/1982 W105 merican Roentgen Ray Society Small owel Obstruction S mall bowel obstruction remains an important cause of morbidity, accounting for up to 15% of surgical admissions for acute nontraumatic abdominal pain. Clinical evidence of complete small-bowel obstruction or complications such as strangulation necessitates emergent surgical management. Traditional medical teaching advocated early operative management of small-bowel obstruction ( Never let the sun rise or set on an obstructed abdomen. ) because clinical features were often unreliable in determining whether complications were present. Radiologic imaging has assumed a paramount role in directing the management of small bowel obstruction, promoted by the widespread availability of MDCT. The key question for a clinician managing a case of suspected small bowel obstruction is how to optimally treat the patient. MDCT accurately answers this question by determining if small bowel obstruction is present, identifying the site and cause of mechanical obstruction, and detecting complications. The sensitivity and specificity of MDCT in this clinical setting is more than 95%, with high accuracy reported in distinguishing small bowel obstruction from adynamic ileus in postoperative patients. Imaging is therefore pivotal in determining whether the patient can be managed conservatively and in guiding the operative approach if surgical management is required. Imaging Modalities Radiography Most patients presenting with clinical features suggestive of small bowel obstruction will first undergo abdominal radiography. Radiographs have accuracy of 67 83% in the diagnosis of small bowel obstruction, with reported sensitivity of 64 82% and specificity of 79 83% [1, 2]. The radiologic hallmark of mechanical small bowel obstruction is dilatation of the proximal small bowel (transverse diameter > 3 cm from outer wall to outer wall) with nondilated distal bowel loops. ssociated findings in a patient with small bowel obstruction include dilatation of the stomach, absence of colonic dilatation (normal caliber or collapsed colon), and the presence of multiple gas-fluid levels on upright or decubitus abdominal radiographs (Fig. 1). The presence of air-fluid levels greater than 2.5 cm in width and air-fluid levels differing more than 5 mm from each other within the same loop of small bowel are additional findings indicative of small bowel obstruction on erect radiographs [2]. Free intraperitoneal gas may be visualized on radiographs in complicated small bowel obstruction. However, it is not always possible to reliably distinguish adynamic ileus and other causes of small bowel dilatation (Table 1) from mechanical obstruction on radiography. This is particularly problematic in the postoperative setting when electrolyte imbalance and the administration of medication are frequent causes of adynamic ileus. The transition point between dilated and nondilated small bowel is not usually visualized on radiography, making it difficult to determine the site or cause of obstruction (Fig. 1). TLE 1: Nonobstructive Causes of Small owel Dilatation dynamic ileus Recent surgery or trauma Shock Electrolyte abnormality Medications (opiates, anticholinergics) Celiac disease Scleroderma Ischemia JR:198, February 2012 W105

2 Downloaded from by on 12/16/17 from IP address Copyright RRS. For personal use only; all rights reserved Fig. 1 Small bowel obstruction., Supine abdominal radiograph shows dilated loops of small bowel., Erect abdominal radiograph shows small bowel dilatation with multiple air-fluid levels. ir-fluid level wider than 2.5 cm (horizontal line) and differential air-fluid levels within same small bowel loop (vertical line) are identified. C, xial CT image shows transition point in mid ileum (arrows), confirming mechanical obstruction due to ileal stricture. The severity of small bowel obstruction may be underestimated on abdominal radiography if the dilated bowel loops are predominantly fluid-filled (Fig. 2). The presence of a gasless abdomen on radiography in a patient with suggestive clinical features should raise the possibility of small bowel obstruction. The string of pearls sign may be seen in predominantly fluid-filled loops of small bowel on erect or decubitus radiographs as small amounts of intraluminal gas collecting along the superior wall separated by the valvulae conniventes (Fig. 3). Fluoroscopy and Follow-Through Examination Fluoroscopy and follow-through examination with oral contrast agents have a limited role in the diagnosis of small bowel obstruction but may be useful in determining the severity of obstruction. Patients with acute small bowel obstruction often tolerate oral contrast material poorly because of nausea and vomiting. Surgeons prefer not to have large quantities of barium in the small bowel lumen if emergent surgery is a possibility. Water-soluble contrast agents become diluted as they pass through dilated fluid-filled bowel loops. Consequently, the degree of opacification may be insufficient to identify the transition point at the site of obstruction. The prolonged transit of contrast material through obstructed bowel means that followthrough radiographs may have to be obtained for several hours, delaying diagnosis. Figure 4 shows the expected fluoroscopic findings in small bowel obstruction, with dilated loops of proximal small bowel opacified with contrast material and a change in the caliber of the small bowel at the transition zone. If high-grade obstruction is present, minimal or no contrast material will opacify small bowel loops distal to the transition zone on delayed radiographs. C MDCT MDCT has been established as the modality of choice for imaging suspected acute small bowel obstruction and is widely available. Isotropic imaging facilitates reconstruction in multiple planes, W106 JR:198, February 2012

3 Small owel Obstruction Downloaded from by on 12/16/17 from IP address Copyright RRS. For personal use only; all rights reserved C Fig. 2 Small bowel obstruction. and, Supine () and erect () abdominal radiographs show loop of dilated small bowel in left lower quadrant, with paucity of bowel gas elsewhere in abdomen. C, Coronal CT image shows multiple loops of dilated small bowel filled with intraluminal fluid, which are not visible on radiographs. This 35-year-old patient had small bowel obstruction due to adhesions from prior laparotomy. enabling tortuous small bowel to be followed in the search for a transition point. The reported accuracy of CT for high-grade small bowel obstruction is 95%, with sensitivity of 90 94% and specificity of 96% [3, 4]. Other published data indicate that the accuracy of CT is reduced for lowgrade obstruction [5]. The diagnosis of small bowel obstruction requires the presence of small bowel dilatation (transverse diameter > 2.5 cm) and the presence of a discrete transition zone between dilated proximal and nondilated distal bowel. The transition zone may be a sharply defined point as with band adhesions (Fig. 5) or a longer segment as with matted adhesions or radiation enteritis (Fig. 6). The administration of oral and IV contrast material optimizes the data provided by CT in assessing small bowel obstruction. However, diagnostic information can be obtained in patients who cannot tolerate oral or IV contrast material and many centers do not routinely administer oral agents to patients undergoing CT for this indication. Retained intraluminal fluid provides negative contrast enhancement within dilated small bowel loops and may be preferable in evaluating ischemic complications of small bowel obstruction. Lack of bowel wall enhancement, an early sign of ischemia, is easier to visualize in the absence of oral contrast material. Other complications, such as perforation, can be identified on CT by the presence of extraluminal air (Fig. 7). However, the relatively high radiation dose of MDCT in comparison with other modalities raises concern for its use in patients requiring repeated imaging studies. JR:198, February 2012 W107

4 Downloaded from by on 12/16/17 from IP address Copyright RRS. For personal use only; all rights reserved Ultrasound Ultrasound has a limited role in the assessment of small bowel obstruction because of poor visualization of gas-filled structures. It is usually restricted to assessment of abdominal wall hernias that may be the site of incarcerated small bowel. Enteroclysis In the setting of chronic or intermittent small bowel obstruction, enteroclysis enables the small bowel to be distended adequately to highlight areas of luminal stenosis. This technique requires the placement of a nasojejunal tube for instillation of a large amount of oral contrast material. Traditionally, enteroclysis has been performed with barium and methylcellulose using fluoroscopy. The volume challenge caused by methylcellulose administration accentuates the effect of low-grade obstruction. The transition zone at the site of obstruction can be missed Fig. 3 Upright abdominal radiograph shows stringof-beads sign. (Reprinted with permission from Eisenberg RL. Gastrointestinal radiology: a pattern approach. Philadelphia, P: Lippincott, 2002) using enterography or CT without volume challenge but is readily identified after enteroclysis. CT and MRI are increasingly used in conjunction with enteroclysis. Cross-sectional imaging provides additional data that can identify extraintestinal manifestations of Crohn disease. MR Enterography MR enterography is an increasingly attractive option for the assessment of small bowel obstruction. However, the increased time of image acquisition and the need for repeated breath-holds to obtain high-quality images limits the application of MRI in patients with acute small bowel obstruction. Therefore, it is most useful in the setting of chronic small bowel abnormality and lowgrade obstruction. This is particularly true in Crohn disease, where reducing the accumulated dose of ionizing radiation in young patients is desired. Multiplanar MRI can be used in the same way as MDCT to look for evidence of a transition point and features indicative of complications. Causes of Small bowel Obstruction There are numerous causes of mechanical small bowel obstruction (Table 2). In developed countries, up to 70% of cases of small bowel obstruction are caused by adhesions within the Fig. 4 Small bowel obstruction., Supine abdominal radiograph shows dilated small bowel loops throughout abdomen., Follow-through radiograph obtained after oral administration of barium shows dilated jejunum on left flank. Tapering of lumen in proximal ileum (arrow) without distal passage of contrast material indicates site of obstruction, which was due to adhesion. W108 JR:198, February 2012

5 Small owel Obstruction Downloaded from by on 12/16/17 from IP address Copyright RRS. For personal use only; all rights reserved TLE 2: Causes of Small owel Obstruction dhesions Previous surgery Peritonitis Idiopathic Crohn disease bdominal hernias Inguinal Ventral Femoral Internal Neoplasms Metastases to small bowel and peritoneum Primary small bowel neoplasms Carcinoid, lymphoma, adenocarcinoma, gastrointestinal stromal tumor Intussusception Intraluminal causes ezoar Gallstone ileus Radiation enteritis Small bowel hematoma Endometriosis abdomen or pelvis. Historically, abdominal hernias were the major cause of small bowel obstruction but now account for less than 10% of cases. The elective repair of inguinal and ventral hernias is the main reason for the decline in hernia-related small bowel obstruction. Crohn disease and intraabdominal neoplasms are other causes of small bowel obstruction. dhesions dhesions are not visible on radiologic imaging. Therefore, this is a diagnosis of exclusion if no other cause can be identified at the site of abrupt transition between dilated proximal small bowel and nondilated distal loops (Fig. 5). pproximately 80% of patients with small bowel obstruction due to adhesions have a history of prior intraabdominal surgery; the remainder have prior peritonitis or no precipitating cause. and adhesions are more likely than matted adhesions to cause complete small bowel obstruction or other complications requiring operative management. ppendectomy and gynecologic surgery predispose to band adhesion formation more than colorectal surgery. Fig. 5 dhesion causing small-bowel obstruction in 50-year-old woman with prior surgery for Crohn disease. xial CT image shows sharp transition point (arrows) at site of band adhesion, which required surgical repair. Small bowel feces sign, presence of particulate material visible in proximal dilated segment of intestine, is useful in identifying site of obstruction because particulate matter tends to be most prominent just proximal to transition zone. Crohn Disease Small bowel obstruction may occur in Crohn disease by the direct effect of strictured and inflamed segments of bowel or by adhesions caused by prior surgical procedures. Obstruction caused by Crohn disease is usually chronic and low grade in nature. The long-standing nature of disease symptoms may mean that small JR:198, February 2012 W109

6 Downloaded from by on 12/16/17 from IP address Copyright RRS. For personal use only; all rights reserved Fig. 6 Radiation enteritis in 53-year-old man who underwent radiation therapy for colorectal neoplasm. and, xial () and sagittal () CT images show segment of small bowel with mural thickening (arrows) containing intraluminal contrast material. This finding corresponds to radiation enteritis, producing zone of transition in small bowel rather than discrete transition point. Fig. 7 Ischemic small bowel in 74-year-old woman presenting with acute abdominal pain., Supine abdominal radiograph obtained at admission shows no small bowel dilatation, with fecal material visible in large bowel., xial IV contrast-enhanced CT image shows small bowel with generalized mural thickening (white arrows) and hypoenhancement relative to normal small intestine (black arrows). C, xial CT image shows whirled appearance in left hemipelvis, with twisting of mesentery (white arrows) and collapsed segment of small bowel (black arrowheads) at site of volvulus. Edematous bowel is noted (black arrows) There is edema in adjacent mesenteric fat. t surgery, internal hernia caused by prior gynecologic surgery was indentified, and necrotic small bowel required extensive resection and end-to-end anastomosis. C bowel obstruction is not suspected clinically. lthough CT is accurate in depicting small bowel abnormality due to Crohn disease (Fig. 8), radiation dose is a consideration in this group of patients, who often require multiple imaging studies over a lifetime. MR enterography may therefore be suitable for selected patients with Crohn disease who have acute small bowel obstruction, provided they can tolerate the longer imaging time and need for breath-holding (Fig. 9). W110 JR:198, February 2012

7 Small owel Obstruction Downloaded from by on 12/16/17 from IP address Copyright RRS. For personal use only; all rights reserved Fig. 8 Crohn disease in 22-year-old man., Coronal CT image shows grossly dilated segment of small bowel in lower left flank., xial CT image shows long segment of ileum with circumferential wall thickening from wall edema, and discrete transition point is seen between this segment and dilated proximal bowel (arrow). C, xial image shows stranding in mesenteric fat immediately superior to thickened segment of small bowel (arrows), consistent with active inflammatory disease. Fig. 9 MR enterography in Crohn disease in 31-yearold woman., Coronal T2-weighted image shows fluid with high signal intensity in dilated loops of jejunum in left flank. and C, xial T2-weighted () and axial contrastenhanced T1-weighted fat-suppressed (C) images show discrete mid ileal segment with circumferential mural thickening and enhancement (arrows), consistent with active Crohn disease. There is transition point between inflamed segment of ileum and dilated proximal bowel. C C JR:198, February 2012 W111

8 Fig. 10 Femoral hernia in elderly woman with acute abdominal pain. and, xial () and coronal () abdominal CT images show loop of small bowel (white arrow) protruding into right groin. There is dilatation of proximal small bowel. Orifice of hernia arises inferior in relation to inguinal ligament and lateral to pubic tubercle (black arrow, ), consistent with femoral hernia. Downloaded from by on 12/16/17 from IP address Copyright RRS. For personal use only; all rights reserved Fig. 11 Richter s hernia with strangulated small bowel in 54-year-old patient with no prior surgical history. and, Sagittal () and axial () CT images show small defect in musculature of right anterior abdominal wall that developed spontaneously. ntimesenteric wall of segment of small bowel protrudes into hernial sac (arrows, ). Proximal small bowel is only mildly dilated because luminal obstruction is not complete; herniated portion of small bowel, however, was strangulated and required surgical resection. bdominal Hernias Hernias occur at sites of muscular or ligamentous weakness in the abdominal wall. Inguinal, femoral, and ventral hernias usually can be detected on clinical examination. Internal hernias occur though acquired or congenital defects in the mesentery, through which bowel may traverse. lthough in some cases only fat may protrude into the hernia sac, at times small or large bowel may become incarcerated within the hernia, leading to obstruction (Fig. 10) and possible strangulation. Elective repair is therefore commonly performed for these defects. Richter hernia occurs when only the antimesenteric portion of a segment of small bowel protrudes through a narrow defect in the abdominal wall (Fig. 11). lthough Richter hernias do not usually cause small bowel obstruction, they are associated with a high rate of ischemic complications. The vascular supply to the herniated portion of bowel wall often becomes compromised by the narrow orifice, leading to strangulation. W112 JR:198, February 2012

9 Small owel Obstruction Downloaded from by on 12/16/17 from IP address Copyright RRS. For personal use only; all rights reserved Fig year-old woman with ovarian carcinoma., Sagittal IV contrast-enhanced CT image shows transition point (arrows) between markedly dilated small bowel and distal bowel, without luminal dilatation. Widespread peritoneal metastases are present in abdomen and pelvis., xial IV contrast-enhanced CT image shows segment of ileum with relative luminal narrowing (arrows) in left hemipelvis surrounded by enhancing soft tissue (arrowheads), consistent with confluent serosal metastatic implants. Fig. 13 Intussusception in 35-year-old man with melanoma., xial CT image shows mass in right lower quadrant of abdomen with target-like appearance due to multiple adjacent bowel wall layers (arrows). Findings were due to ileocolic intussusception, with small bowel metastasis acting as lead point., Coronal image shows intussusception in longitudinal axis. There is clear transition point between intussusception and proximal dilated small bowel (arrows). Neoplastic Disease Metastatic disease is the most frequent neoplastic cause of small bowel obstruction. Tumors with a propensity to cause widespread peritoneal metastases include ovarian, colonic, pancreatic, and gastric neoplasms. This may lead to multiple serosal metastases of the small bowel, forming confluent soft-tissue masses that surround the bowel. Obstruction occurs by extrinsic compression of the small bowel lumen (Fig. 12) or tethering of bowel loops by the JR:198, February 2012 W113

10 Downloaded from by on 12/16/17 from IP address Copyright RRS. For personal use only; all rights reserved Fig. 14 Gallstone ileus in elderly woman with small bowel obstruction due to gallstone ileus., xial CT image of pelvis shows large laminated calculus within dilated loop of distal ileum in midline (arrow)., xial CT image through liver shows pneumobilia (arrows), consistent with biliary-enteric fistula. Fig. 15 Phytobezoar in 65-year-old diabetic patient who consumed vegetarian diet composed predominantly of chickpeas., xial CT image shows intraluminal particulate material within dilated segment of bowel in right lower quadrant (arrow). Other proximal loops of distended small bowel contain gas-fluid levels., Sagittal CT image shows transition point in mid ileum with collapsed small bowel distally (arrows). Operative findings confirmed presence of phytobezoar. serosal deposits. Metastases to the wall of the small bowel in tumors, such as melanoma, can cause endoluminal obstruction. Primary neoplasms of the small bowel are a less frequent cause of mechanical obstruction but include adenocarcinoma, lymphoma, and gastrointestinal stromal tumors. These lesions may cause luminal narrowing or intussusception. Intussusception Intussusception refers to telescoping of a segment of bowel within another portion of bowel. This results in a target-like appearance on CT or ultrasound because of multiple layers of bowel wall adjacent to one another and the interposition of mesenteric fat between the telescoped layers of bowel (Fig. 13). Ileocolic intussusception is a common cause of acute abdomen during infancy. ecause most childhood cases are idiopathic, air enema may be sufficient for reduction. In adults, intussusception is most frequently a transient finding identified on CT, without significant clinical features. Intussusception length of 3.5 cm or less predicts a self-limiting lesion that will resolve spontaneously, and follow-up imaging is not required W114 JR:198, February 2012

11 Small owel Obstruction Downloaded from by on 12/16/17 from IP address Copyright RRS. For personal use only; all rights reserved Fig. 16 Closed-loop obstruction due to internal hernia in contiguous axial images in 75-year-old woman with no significant medical history who presented with acute abdominal pain. and, There is whorled appearance of mesentery containing blood vessels (arrows, ), situated just above U-shaped loop of dilated small bowel (line, ). lthough vascular supply was compromised at laparotomy, segment of small bowel reperfused normally when hernia was reduced, and small bowel resection was not required. Fig. 17 Closed-loop obstruction with bowel infarction in 49-year-old man., xial contrast-enhanced image shows jejunoileal intussusception, with interposition of mesenteric fat between telescoped portions of bowel., Coronal CT image shows dilated C-shaped portion of bowel (line) centered on area of mesentery containing blood vessels (white arrow). t time of surgery, lead point of intussusception was found to be submucosal jejunal neoplasm, later confirmed as gastrointestinal stromal tumor. Torsion of mesentery at site of intussusception led to closed-loop obstruction, resulting in infarction of segment of small bowel. lack arrows show focal areas of hypoenhancement in liver due to hepatic metastases from small bowel tumor. for these patients. For intussusception greater than 3.5 cm in length, further CT after 30 minutes may be considered to confirm resolution. Small bowel obstruction because of intussusception is rare in adults and is usually due to an underlying bowel lesion acting as a lead point. Causes include benign and malignant neoplasms, Meckel diverticulum, and inflammatory lesions. Symptomatic adult patients with intussusception that does not resolve spontaneously will require operative management to identify and resect the underlying lesion. Intraluminal Obstruction Small bowel obstruction is rarely caused by intraluminal material. The site of obstruction is usually at the ileocecal valve, where the lumen of the bowel is smallest. Gallstone ileus occurs when a large gallbladder calculus passes into the small bowel via a biliary-enteric JR:198, February 2012 W115

12 Downloaded from by on 12/16/17 from IP address Copyright RRS. For personal use only; all rights reserved Fig year-old woman with 2-day history of left flank pain and no previous abdominal surgery., xial CT image shows vascular engorgement (white arrows) and edema in mesentery of left flank (black arrow), with ascites identified in right flank., Coronal CT image shows luminal narrowing at site of internal hernia in anterior aspect of left lower abdomen (arrow) and presence of ascites. C, Sagittal CT image through left side of abdomen shows hypoenhancement and mural thickening of loop of small bowel (black arrows) consistent with ischemia. There is edema of adjacent mesenteric fat and engorgement of mesenteric veins (white arrows). t surgery, transomental internal hernia was reduced, and resection of long segment of infracted small bowel was performed. TLE 3: CT Findings of Small owel Ischemia owel wall Poor or absent enhancement Delayed hyperenhancement Mural thickening Pneumatosis Mesentery Engorgement of mesenteric vessels Mesenteric edema Mesenteric hemorrhage Other findings Portal and mesenteric venous gas scites fistula (Fig. 14). Other imaging findings of gallstone ileus are the usually large gallstone and biliary air. bezoar is composed of ingested material that is not digested within the gastrointestinal tract and causes an obstructing intraluminal mass. phytobezoar is formed by undigested plant or vegetable matter (Fig. 15); a trichobezoar is caused by ingestion of hair. Management Strategies The ultimate role of radiologic imaging in small bowel obstruction is to determine whether the patient can be managed with conservative measures or surgery is required. Indications for emergency surgery include evidence of complete obstruction with absence of C W116 JR:198, February 2012

13 Small owel Obstruction Downloaded from by on 12/16/17 from IP address Copyright RRS. For personal use only; all rights reserved gas or fluid in the distal gastrointestinal tract and signs of strangulation or bowel perforation. closed-loop obstruction occurs when a segment of small bowel becomes obstructed at two adjacent points. Strangulation is defined as bowel ischemia occurring due to torsion of the mesentery providing vascular supply to the closed loop. Early identification and surgical reduction of a closed-loop obstruction will restore vascular supply to the ischemic segment of small bowel (Fig. 16). However, delayed intervention may result in infarction of the affected small bowel, requiring resection of the nonviable segment (Figs. 7, 17, and 18). It is often difficult to confidently diagnose small bowel ischemia on CT. Table 3 illustrates the findings of small bowel ischemia on CT examination [6, 7]. The presence of a combination of these signs increases the reliability of diagnosing ischemia. Conclusion Small bowel obstruction remains an important cause of acute abdominal pain in patients presenting to the emergency department. MDCT is the modality of choice for identifying the cause of small bowel obstruction and determining whether emergent surgery is required. dhesions are by far the most common cause of small bowel obstruction. Other less frequent causes include Crohn disease, neoplasms, and abdominal hernias. Identifying the transition point between dilated and nondilated small bowel, although not required to make the diagnosis of obstruction, is the key to establishing the site and cause of small bowel obstruction. References 1. Maglinte DD, Reyes L, Harmon H, et al. Reliability and role of plain film radiography and CT in the diagnosis of small-bowel obstruction. JR 1996; 167: Thompson WM, Kilani RK, Smith, et al. ccuracy of abdominal radiography in acute smallbowel obstruction: does reviewer experience matter? JR 2007; 188:757; [web]w233 W Megibow J, althazar EJ, Cho KC, Medwid SW, irnbaum, Noz ME. owel obstruction: evaluation with CT. Radiology 1991; 180: Fukuya T, Hawes DR, Lu CC, Chang PJ, arloon TJ. CT diagnosis of small-bowel obstruction: efficacy in 60 patients. JR 1992; 158: Maglinte DD, Gage SN, Harmon H, et al. Obstruction of the small intestine: accuracy and role of CT in diagnosis. Radiology 1993; 188: Ha HK, Kim JS, Lee MS, et al. Differentiation of simple and strangulated small-bowel obstructions: usefulness of known CT criteria. Radiology 1997; 204: Sheedy SP, Earnest F, Fletcher JG, Fidler JL, Hoskin TL. CT of small-bowel ischemia associated with obstruction in emergency department patients: diagnostic performance evaluation. Radiology 2006; 241: Suggested Reading 1. DiSantis DJ, Oliphant M, Leyendecker JR. Gastrointestinal tract. In: Dalrymple NC, Leyendecker JR, Oliphant M, eds. Problem solving in abdominal imaging. Philadelphia, P: Mosby Elsevier, Fidler JL, Guimaraes L, Einstein DM. MR imaging of the small bowel. RadioGraphics 2009; 29: Frager DH, aer JW, Rothpearl, ossart P. Distinction between postoperative ileus and mechanical small bowel obstruction: value of CT compared with clinical and other radiographic findings. JR 1995; 164: Lazarus DE, Slywotsky C, ennett GL, Megibow J, Macari M. Frequency and relevance of the small bowel feces sign on CT in patients with small-bowel obstruction. JR 2004; 183: Lvoff N, reiman RS, Coakley FV, Lu Y, Warren RS. Distinguishing features of self-limiting adult small-bowel intussusception identified at CT. Radiology 2003; 227: Sailer J, Peloschek P, Schober E, et al. Diagnostic value of CT enteroclysis compared with conventional enteroclysis in patients with Crohn s disease. JR 2005; 185: Taourel PG, Fabre JM, Pradel J, Seneterre EJ, Megibow J, ruel JM. Value of CT in the diagnosis and management of patients with suspected acute small-bowel obstruction. JR 1995; 165: JR:198, February 2012 W117