Which imaging study is recommended first for suspected small bowel obstruction (SBO)?

For suspected small bowel obstruction (SBO), the first recommended imaging study is typically an abdominal plain film radiograph (also known as a KUB - kidneys, ureters, and bladder film). This initial imaging method is favored because it is widely available, cost-effective, and can quickly help identify key signs of SBO, such as air-fluid levels and distended bowel loops.

Plain films can provide immediate information about the presence of obstruction and whether any significant complications, such as perforation or free air due to perforated bowel, are present. This can guide further management decisions and the need for additional imaging or intervention.

While CT scans are highly sensitive and specific for diagnosing small bowel obstruction and can provide a more detailed evaluation of the cause of the obstruction, they are generally not the first step due to considerations like radiation exposure and the availability of CT in all settings. Ultrasound can also be used, especially in certain populations like children or pregnant women, but it is not the first line in adults. MRI is used even less frequently for SBO, as it is not usually the first-line imaging modality in acute settings and is limited by availability and time constraints.