From the Guidelines
Intestinal obstruction on abdominal X-rays is identified by several key radiographic findings, including dilated bowel loops, multiple air-fluid levels, and the absence of gas in the rectum or distal colon, as reported in the most recent study by 1. The most characteristic sign is dilated bowel loops, typically showing a "step-ladder" pattern with multiple air-fluid levels when viewed on an upright film. Small bowel obstruction typically shows dilated loops greater than 3cm in diameter with visible valvulae conniventes (circular folds) crossing the entire lumen. Large bowel obstruction presents with colonic dilatation exceeding 6cm (or >9cm for the cecum) with haustral markings that only partially cross the lumen. Other important signs include:
- differential air-fluid levels (multiple levels at different heights within the same loop)
- the "string of pearls" sign (small bubbles of gas trapped between fluid and valvulae conniventes)
- a transition point may be visible between dilated proximal bowel and collapsed distal segments
- free intraperitoneal air suggests perforation, which is a serious complication
- fecal loading throughout the colon typically indicates functional rather than mechanical obstruction These findings help differentiate between small and large bowel obstruction and determine the need for urgent surgical intervention versus conservative management, as supported by the study 1. It's worth noting that while plain X-rays can be useful in diagnosing intestinal obstruction, their sensitivity and specificity are limited, and CT scans are often necessary to provide more detailed information about the underlying cause of obstruction and to guide management, as stated in the study 1. In cases where CT scans are used, findings such as a closed-loop obstruction, markers of bowel ischemia, and the "small bowel feces sign" can predict the need for operative management, as reported in the study 1. Overall, the diagnosis and management of intestinal obstruction require a combination of clinical evaluation, imaging studies, and surgical intervention, with the goal of minimizing morbidity, mortality, and improving quality of life, as emphasized in the study 1.
From the Research
Signs of Intestinal Obstruction in Abdominal X-ray
- The presence of air-fluid levels of differential height in the same small-bowel loop is a significant finding associated with high-grade or complete small-bowel obstruction 2
- A mean air-fluid level width greater than or equal to 25 mm on upright abdominal radiographs is also a predictive sign of high-grade or complete small-bowel obstruction 2
- Abdominal radiography findings, including bowel dilatation, can indicate intestinal obstruction, but may not be sufficient to distinguish obstruction from other causes of colonic dilatation 3
- 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
Diagnostic Approach
- Abdominal CT with oral and intravenous gastrografin contrast is highly sensitive and specific in detecting and characterizing small-bowel obstruction 4
- The use of Gastrografin can help discriminate between partial and complete small-bowel obstruction, and can expedite resolution of partial obstructions 5, 6
- CT-scans can be useful in evaluating patients with suspected small-bowel obstruction, but may not be necessary in all cases, especially when clinical history, physical examination, and plain film are conclusive for diagnosis 5
Key Findings
- Air-fluid levels and bowel dilatation are key findings in abdominal X-rays that can indicate intestinal obstruction 2, 3
- Clinical signs, such as abdominal pain, nausea, and vomiting, can also suggest intestinal obstruction 4
- The presence of signs of strangulation, such as severe direct tenderness, involuntary guarding, and abdominal rigidity, can indicate the need for urgent operative intervention 4, 6