Radiographic Diagnosis of Ileus

Classic Radiographic Findings

The World Journal of Emergency Surgery recommends that ileus is characterized by multiple air-fluid levels, diffuse dilatation of both small and large bowel loops, and absence of a clear transition point, distinguishing it from mechanical obstruction 1
Multiple air-fluid levels throughout the abdomen, representing stagnant intestinal contents, are a key feature of ileus, as reported by the World Journal of Emergency Surgery and Gut 1, 2
Gas is distributed throughout small and large bowel in ileus, unlike mechanical obstruction where gas is typically absent distal to the obstruction, according to the World Journal of Emergency Surgery 1

The key differentiating feature between ileus and mechanical obstruction is that ileus shows gas throughout the entire bowel without a clear transition point, while mechanical obstruction demonstrates a triad of multiple air-fluid levels, distended small bowel loops proximal to obstruction, and absence of gas in the colon distal to the blockage, as stated by the World Journal of Emergency Surgery 1
Mechanical small bowel obstruction shows dilated loops proximal to obstruction with collapsed bowel distally and absent colonic gas, as reported by the World Journal of Emergency Surgery 1

Plain x-rays have only approximately 70% sensitivity for detecting bowel obstruction and are even less reliable for ileus, according to the World Journal of Emergency Surgery 1
The reported plain abdominal x-ray findings in ileus are unreliable and non-specific, making them insufficient for definitive diagnosis, as stated by Gut 2
CT scanning is the preferred imaging modality when there is diagnostic uncertainty, with approximately 90% accuracy in predicting the need for surgery, as recommended by the World Journal of Emergency Surgery 1

Absence of peritoneal signs on physical examination supports ileus over ischemia or perforation, according to the World Journal of Emergency Surgery 1
Laboratory values, including elevated inflammatory markers and white blood cell count, may suggest peritonitis or strangulation, though sensitivity is low, as reported by the World Journal of Emergency Surgery 1
Electrolyte abnormalities, particularly hypokalemia, are frequently found and contribute to ileus, as stated by the World Journal of Emergency Surgery 1
Suspected strangulation or ischemia requires CT scan, as plain films cannot detect early signs, according to the World Journal of Emergency Surgery 1
Postoperative patients, elderly or unconscious patients, require advanced imaging due to obscured clinical examination, as recommended by the World Journal of Emergency Surgery 4