What is the significance of multiple air-fluid levels seen on an abdominal X-ray (abdominal radiograph)?

From the Guidelines

Multiple air-fluid levels seen on an abdominal X-ray are highly suggestive of a small bowel obstruction, which is a serious condition that requires prompt medical evaluation and treatment. This finding is characterized by the presence of multiple horizontal lines on the X-ray, indicating the separation of gas and liquid in the bowel 1. The sensitivity of plain X-rays for detecting small bowel obstruction is approximately 70%, with a triad of multiple air-fluid levels, distention of small bowel loops, and absence of gas in the colon being pathognomonic for this condition 1.

Key Considerations

• The presence of multiple air-fluid levels increases the likelihood of a mechanical obstruction rather than a functional ileus
• Patients with this finding should undergo further assessment with CT imaging, and may require hospital admission for treatment with IV fluids, nasogastric tube placement, and possibly surgery
• Pain management may include opioids initially, though these can sometimes worsen functional bowel problems
• The definitive treatment depends on identifying and addressing the underlying cause of the obstruction, which can include adhesions from previous surgery, hernias, tumors, inflammatory bowel disease, or volvulus (bowel twisting)

Important Findings

• A large volume pneumoperitoneum secondary to bowel perforation can also be detected on plain X-rays, preferably by an erect chest X-ray 1
• Plain X-rays do not detect early signs of peritonitis or strangulation, highlighting the need for prompt further evaluation and treatment 1
• The absence of gas in the colon can help differentiate small bowel obstruction from other causes of bowel obstruction 1

From the Research

Multiple Air Fluid Levels on Abdominal X-Ray

• The presence of multiple air fluid levels on an abdominal X-ray can be an indicator of bowel obstruction, with a study published in 1993 2 finding that differential air-fluid levels were present in 52% of mechanical obstructions and 29% of adynamic obstructions.
• The same study found that the sensitivity of differential air-fluid levels for mechanical obstruction was 0.52, while the specificity was 0.71, and that the positive predictive value increased as the height of the differential air-fluid levels increased.
• A later study published in 2007 3 found that the presence of two or more air-fluid levels, air-fluid levels wider than 2.5 cm, and air-fluid levels differing more than 5 mm from one another in the same loop of small bowel were highly significant indicators of small-bowel obstruction.
• The 2007 study also found that more experienced radiologists were more accurate in detecting acute small-bowel obstruction, with senior staff members having a higher sensitivity and specificity than junior staff and radiology residents 3.
• The presence of multiple air fluid levels can be used as a diagnostic tool, but should be interpreted in conjunction with other clinical findings and imaging results, as the sensitivity and specificity of this sign can vary depending on the population and the experience of the reviewer 2, 3.