What imaging is recommended in the Emergency Room (ER) for suspected bowel obstruction?

From the Guidelines

For suspected bowel obstruction in the emergency room, CT abdomen and pelvis with IV contrast is the preferred initial imaging study. This recommendation is based on the American College of Radiology's (ACR) appropriateness criteria for suspected small-bowel obstruction, which suggests that CT abdomen and pelvis with IV contrast is usually appropriate for the initial imaging of a suspected small-bowel obstruction with an acute presentation 1. The ACR panel did not agree on recommending radiographs of the abdomen and pelvis in patients with an acute presentation of suspected small-bowel obstruction, citing insufficient medical literature to conclude whether or not these patients would benefit from this procedure.

The use of CT abdomen and pelvis with IV contrast has been shown to have a high diagnostic accuracy, with sensitivity and specificity exceeding 90% 1. This imaging modality provides excellent visualization of the bowel, potential obstruction points, and complications like ischemia or perforation. Additionally, CT with IV contrast is preferable for routine imaging of suspected small-bowel obstruction, as it demonstrates whether the bowel is perfusing normally or is potentially ischemic, and provides information about the potential etiology, such as Crohn disease and neoplasm.

In comparison, plain abdominal X-rays (supine and upright) may be performed first due to availability and lower cost, but they have limited sensitivity (around 60-70%) and can miss partial obstructions 1. Ultrasound might be considered in pregnant patients or children to avoid radiation exposure, though it's operator-dependent and less reliable for bowel obstruction. Water-soluble contrast studies like Gastrografin can be both diagnostic and potentially therapeutic for partial small bowel obstructions by drawing fluid into the bowel lumen and potentially resolving the obstruction. MRI, while radiation-free, is rarely used in emergency settings due to longer acquisition times and limited availability, though it provides excellent soft tissue detail when available.

Some key points to consider when evaluating suspected bowel obstruction include:

• The importance of identifying ischemia and necrosis, especially in adhesive small bowel obstruction and sigmoid volvulus
• The use of CT to accurately stage neoplastic bowel obstruction and identify superimposed complications such as intestinal perforation and peritonitis
• The potential for internal hernias to evolve into intestinal strangulation, and the importance of accurate preoperative diagnosis using CT 1

Overall, the use of CT abdomen and pelvis with IV contrast as the initial imaging study for suspected bowel obstruction in the emergency room is supported by the ACR's appropriateness criteria and the available evidence, and is likely to provide the most accurate diagnosis and guide appropriate management.

From the Research

Imaging Modalities for Bowel Obstruction in the ER

• Computed Tomography (CT) scans have been proven to be useful in revealing the site, level, and cause of bowel obstruction, as well as displaying signs of threatened bowel viability 2.
• Multidetector computed tomography (MDCT) is currently used to diagnose bowel obstruction, and reports should focus on confirming the obstruction, determining the transition point, establishing the cause, and seeking signs of complications 3.
• CT scans can identify signs of ischemia, which is important in managing patients with bowel obstruction, as it enables early surgical intervention to avoid greater morbidity and mortality associated with strangulation and ischemia of the obstructed bowel loop 3.

Alternative Imaging Modalities

• Plain radiographs are often ordered but cannot exclude the diagnosis of bowel obstruction 4.
• Ultrasound is a reliable diagnostic method for bowel obstruction, although its use may be limited in certain cases 4.
• Unenhanced CT scans may be sufficient for identifying the etiology of bowel obstruction in certain cases, such as adhesions or tumors, but contrast agent is still recommended in most cases 5.

Diagnostic Approach

• Abdominal CT with oral and intravenous gastrografin contrast is highly sensitive and specific in detecting and characterizing bowel obstruction 6.
• A systematic approach to diagnosis and treatment, including medical resuscitation, abdominal CT, and surgical intervention when necessary, is essential for managing bowel obstruction in the ER 6.