Elliot K. Fishman M.D.
Johns Hopkins Hospital

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“The main complication of SBO is intestinal ischemia. In the emergency setting, CT imaging is the modality of choice for SBO because of its ability to assess the bowel wall, the supporting mesentery and peritoneal cavity all in one. On the other hand, the radiologist who documents an intestinal ischemia should think about SBO as possible cause. In this case, the mainfinding which helps the radiologist in the identification of SBO is the presence of multiple and packed valvulae conniventes in the dilated bowel wall and the “transition zone” that indicates the passage between compressed and decompressed small bowel, otherwise the localization of the obstruction cause. Once the site of obstruction has been recognized, the other issue is to assess the cause of obstruction, considering that the most common cause of SBO remains “unidentified” and related to intra-abdominal adhesions. After that, the following most important point is to rule out the presence of an ischemic bowel and mesenteric changes associated to SBO. CT signs of bowel ischemia include reduced or increased bowel wall enhancement, mesenteric edema or engorgement, fluid or free air in the peritoneal cavity. This condition usually leads to an urgentlaparotomy and, in some cases, to a surgical resection.”
Small bowel obstruction and intestinal ischemia: emphasizing the roleof MDCT in the management decision process
Mariano Scaglione et al.
Abdominal Radiology (2022) 47:1541–1555

“The main complication of SBO is intestinal ischemia. In the emergency setting, CT imaging is the modality of choice for SBO because of its ability to assess the bowel wall, the supporting mesentery and peritoneal cavity all in one. On the other hand, the radiologist who documents an intestinal ischemia should think about SBO as possible cause. In this case, the main finding which helps the radiologist in the identification of SBO is the presence of multiple and packed valvulae conniventes in the dilated bowel wall and the “transition zone” that indicates the passage between compressed and decompressed small bowel, otherwise the localization of the obstruction cause. Once the site of obstruction has been recognized, the other issue is to assess the cause of obstruction, considering that the most common cause of SBO remains “unidentified” and related to intra-abdominal adhesions. After that, the following most important point is to rule out the presence of an ischemic bowel and mesenteric changes associated to SBO.”
Small bowel obstruction and intestinal ischemia: emphasizing the roleof MDCT in the management decision process
Mariano Scaglione et al.
Abdominal Radiology (2022) 47:1541–1555

”The most important criterion consists of dilatation of small bowel loops with thickened/packed valvulae conniventes and air–fluid stasis. The second major criterion for SBO diagnosis is the transition point identification. The “transition point” corresponds to the passage from dilated to decompressed distal small bowel loops and identifies the place where the obstructing process is located. However, the transition point identification is not always easy, and the reported accuracy of detection may vary significantly, ranging from 63 to 93%, depending essentially on the degree of bowel dilatation from one side and the adjacent collapsed loops on the other.”
Small bowel obstruction and intestinal ischemia: emphasizing the roleof MDCT in the management decision process
Mariano Scaglione et al.
Abdominal Radiology (2022) 47:1541–1555

Oral contrast

• Water
• Omnipaque-350

Intravenous contrast

• 100-120 cc of Omnipaque -350
• Injection rate of 4-5 cc/sec

Scan Protocol Selection

• Arterial phase imaging
• Venous phase imaging
• Role of non-contrast CT
• Role of delayed phase imaging

Data Analysis Tools

• Axial
• MPR (coronal/sagittal)
• Curved planar reconstruction (CPR)
• Volume rendering technique (VRT)
• Cinematic Rendering (CR)
• Maximum intensity projection (MIP)

“Small-bowel obstruction (SBO) continues to be a substantial cause of morbidity and mortality, accounting for 12%–16% of hospital admissions for the evaluation of acute abdominal pain in the United States. Most patients with SBO are treated successfully with nasogastric tube decompression. However, the mortality of SBO ranges from 2% to 8% and may increase to as high as 25% if bowel ischemia is present and there is a delay in surgical management.” 
Review of Small-Bowel Obstruction: The Diagnosis and When to Worry
Paulson EK, Thompson WM
Radiology. 2015 May;275(2):332-42.

“Multidetector CT has been proven to be the single best imaging tool for evaluating patients suspected of having SBO, with sensitivity and specificity of 95%; it is also highly accurate in detecting the complications of SBO.” 
Review of Small-Bowel Obstruction: The Diagnosis and When to Worry
Paulson EK, Thompson WM
Radiology. 2015 May;275(2):332-42.

Extrinsic

• Adhesions
• Hernias (internal and external)
• Endometriosis
• Neoplasms (extraintestinal)

Intrinsic

• Inflammatory/infectious diseases
• Neoplasms of the small bowel (primary and secondary)
• Vascular causes (mesenteric ischemia)
• Intramural hematoma
• Radiation enteritis
• Intussusception

Intraluminal

• Gallstone ileus
• Bezoars
• Foreign bodies

Simple

• Intermittent or partial obstruction
• Prolonged, complete or high grade obstruction

Complicated

• Closed loop or incarcerated obstruction
• Strangulation

“Time to surgery” is the most important prognostic factor as mortality significantly increases with the duration of symptoms. Ritz et al. determined that the survival rate in the first 12 h was 84.3%, compared with only 11.6% after 24 h and2% after 48 h. In response to this serious emergency condition, all patients with a high index of clinical suspicion of ASBI should be assessed via contrast-enhanced CT.”
Comprehensive review of acute small bowel ischemia: CT imagingfindings, pearls, and pitfalls
Sitthipong Srisajjakul · Patcharin Prapaisilp · Sirikan Bangchokdee
Emergency Radiology (2022) 29:531–544

”In high grade or in chronic obstructions, endoluminal stasis and gas create an appearance rather similar to feces in colon, the “small-bowel feces” sign. The prevalence of this sign ranges from 6 to 37%. This feature is usually evident just proximal to the transition point and can help localize it. However, it has shown a poor correlation in patients requiring a surgical approach for SBO.”
Small bowel obstruction and intestinal ischemia: emphasizing the roleof MDCT in the management decision process
Mariano Scaglione et al.
Abdominal Radiology (2022) 47:1541–1555

“The most common cause ofclosed loop to search for is a single adhesive band, and theincidence is high particularly in patients after Roux-en-Ygastric bypass or simply after previous laparotomies for anyother reason. Other causes include internal hernias, congenitalor iatrogenic defects in the mesentery or omentum thatmay lead to catch a part of the bowel causing a closed-loopobstruction. The classic appearance of a closed-loop obstruction is the “C”- or “U”-shaped configuration with the mesenteric vessels converging toward the site of obstruction. This appearance also named “spoke-wheel sign” is related to bowel ischemia in up to 46% of patients. The supporting vessels radially converge on a single central point.”
Small bowel obstruction and intestinal ischemia: emphasizing the roleof MDCT in the management decision process
Mariano Scaglione et al.
Abdominal Radiology (2022) 47:1541–1555