Complication imaging after laparoscopic Roux-en-Y gastric bypass: clues to the diagnosis and pitfalls

Obesity is a complex chronic disease with a rising global prevalence and significant health implications. The laparoscopic Roux-en-Y gastric bypass (LRYGB) is one of the most widely performed bariatric procedures worldwide, ensuring significant weight loss and reducing obesity-related comorbidities. However, the risk of postoperative complications remains considerable. Multidetector computed tomography (MDCT) is regarded as the primary imaging modality for the assessment of suspected complications, due to its high diagnostic accuracy. This review offers a comprehensive overview of early (≤ 30 days) and late (> 30 days) postoperative complications, including anastomotic leak, abscess, hemorrhage, small bowel obstruction (SBO), internal hernia, gastro-gastric fistula, intussusception, and marginal ulcer, with emphasis on characteristic MDCT features. Due to its advantage as a dynamic method, upper gastrointestinal (Gl) studies with oral contrast material may be helpful for the diagnosis of leak and gastro-gastric fistula formation. A comprehensive understanding of the altered postoperative anatomy and the specific radiological signs of complications are essential for accurate MDCT interpretation, minimizing diagnostic errors and enabling timely, targeted clinical intervention. Today, MRI can be considered a problem-solver through its possibility of combining static with dynamic sequences in selected cases. In this narrative review, we highlight the most frequent complications of Roux-en-Y gastric bypass (LRYGB), allowing radiologists to become familiar with the typical radiological features and pitfalls in MDCT, upper GI studies, and MRI, when facing this type of surgery. CRITICAL RELEVANCE STATEMENT: Postoperative complications following laparoscopic LRYGB can pose considerable diagnostic challenges. Although MDCT is the most important modality, upper GI studies (for leakage or suspected gastro-gastric fistula) and increasingly MRI (for pouch problems or in pregnant patients) can improve diagnostic accuracy and support effective clinical decision-making. KEY POINTS: LRYGB complications are challenging due to altered anatomy and distinct imaging features. Postoperative bleeding, leaks with/without abscess, small bowel obstruction, and internal hernia are the most common serious complications. MDCT evaluation and reporting should be structured and focus on characteristic CT signs to support accurate imaging diagnosis.