What are the X-ray findings in intestinal obstruction?

From the Guidelines

X-ray findings in intestinal obstruction are typically characterized by dilated bowel loops, air-fluid levels, and a transition point, but CT scans are the preferred diagnostic tool due to their high sensitivity and specificity in establishing the underlying cause of obstruction. The diagnosis of intestinal obstruction can be made using plain radiographs, which may show dilated bowel loops proximal to the obstruction, with a paucity of gas in the distal bowel 1. The small bowel is considered dilated when its diameter exceeds 3 cm, while the large bowel is dilated when greater than 6 cm. Air-fluid levels arranged in a stepladder pattern are commonly seen on upright or decubitus films, representing stagnant intestinal contents. However, the accuracy of abdominal radiographs in detecting intestinal obstruction can be limited, with some studies reporting a success rate of only 30% to 70% 1.

Some key findings on X-ray that may indicate intestinal obstruction include:

• Dilated bowel loops proximal to the obstruction
• Air-fluid levels arranged in a stepladder pattern
• Transition point where dilated bowel abruptly changes to decompressed bowel
• "Coffee bean" sign in sigmoid volvulus or a "bent inner tube" appearance in cecal volvulus
• Pneumoperitoneum (free air) suggesting bowel perforation

However, CT scans are the preferred diagnostic tool for intestinal obstruction due to their high sensitivity and specificity in establishing the underlying cause of obstruction 1. CT scans can provide detailed information about the cause and complications of obstruction, including the location of the obstruction, the grade of the obstruction, and the presence of bowel ischemia or other complications. The use of water-soluble contrast can optimize the diagnostic value of CT scans, and findings on CT scans can help predict the need for operative management 1.

In terms of management, CT scans play a key role in guiding management decisions, including the need for emergency surgery 1. Findings on CT scans that predict the need for operative management include a closed-loop obstruction, markers of bowel ischemia, and the "small bowel feces sign". Overall, while X-ray findings can be useful in diagnosing intestinal obstruction, CT scans are the preferred diagnostic tool due to their high sensitivity and specificity in establishing the underlying cause of obstruction 1.

From the Research

X-ray Findings in Intestinal Obstruction

• The presence of air-fluid levels of differential height in the same small-bowel loop and the presence of a mean air-fluid level width greater than or equal to 25 mm on upright abdominal radiographs are strongly associated with the severity of obstruction 2
• Upright abdominal radiographs are important in the examination of patients with suspected small-bowel obstruction and may contribute to the imaging triage of these patients 2
• Abdominal radiography findings can confirm the diagnosis of intestinal obstruction, but may not be sufficient to distinguish obstruction from other causes of colonic dilatation 3
• Computed tomography (CT) is the imaging method of choice for establishing the diagnosis and cause of large-bowel obstruction 3
• CT can also be used to evaluate small bowel obstruction, including determining the transition point, cause, and presence of ischemia 4

Radiologic Imaging

• Radiologic imaging can confirm the diagnosis of intestinal obstruction and serve as a useful adjunctive investigation when the diagnosis is less certain 5
• Non-contrast computed tomography is recommended if the index of suspicion is high or if suspicion persists despite negative radiography 5
• CT is currently used as a complementary imaging study, in direct competition with the more traditional gastrointestinal contrast-enhanced examinations generally used 6

Diagnostic Criteria

• The diagnosis of intestinal obstruction is established or suspected on clinical grounds, and is usually confirmed with plain abdominal radiography 6
• The clinical presentation of intestinal obstruction generally includes nausea and emesis, colicky abdominal pain, and a failure to pass flatus or bowel movements 5
• The classic physical examination findings of abdominal distension, tympany to percussion, and high-pitched bowel sounds suggest the diagnosis of intestinal obstruction 5