The American Society for Metabolic and Bariatric Surgery (ASMBS) endorses sleeve gastrectomy (SG), Roux‐en‐Y gastric bypass (RYGB), adjustable gastric banding (AGB), and biliopancreatic diversion with duodenal switch (BPD‐DS) as primary bariatric operations in the United States. More recently, the ASMBS endorsed single anastomosis duodenoileal bypass with sleeve gastrectomy (SADI‐S) as well. While SG and RYGB continue to be the most commonly performed bariatric operations, AGB has experienced a sharp decline in the last decade. BPD‐DS remains the least common procedure performed in the US, accounting for only 1–2% of cases. Nonetheless, it is gaining popularity as a revisional bariatric surgery for weight regain, particularly after failed SG. Although technical variations exist depending on the region and surgeon preference, the theoretical concept, postinterventional anatomy, and potential complications are grossly similar.

Gastroenterologists are increasingly encountering bariatric patients in their daily practice and should be able to recognize and address the most common surgical complications that might arise following bariatric surgery. Common endoscopic and radiographic findings are presented below, including normal views for orientation and anatomical illustration (Figures 66.1–66.26). While not exhaustive, this selection is made with an emphasis on the most frequently encountered surgical complications.

Sleeve gastrectomy has recently become the most popular bariatric operation both in the US and worldwide. An effective restrictive operation with favorable neurohormonal effects, SG avoids intestinal surgery and the associated complications such as internal herniation and small bowel obstruction. Leaks, although uncommon, are the most feared complication and these most frequently arise along the upper third of the staple line, mainly just below the gastroesophageal junction. Fistulization is another complication, most commonly occurring along the angle of His at the proximal staple line. Stenosis or stricture formation, which usually occurs at the level of the gastric incisura, can lead to pouch dilation.

Roux‐en‐Y gastric bypass, arguably still considered the “gold standard” of weight loss surgery, is an extremely effective restrictive operation that additionally has a small malabsorptive component and potent neurohormonal effects. Leakage is a significant cause of morbidity after RYGB and most commonly occurs at the level of the gastrojejunal anastomosis (GJA). Another noteworthy complication is anastomotic stricture, also most commonly occurring at the GJA. Anastomotic strictures are thought to be the natural evolution of chronic inflammation and marginal ulcerations resulting in fibrosis and consequent stomal narrowing. Since alteration of intestinal anatomy is a component of the RYGB by design, internal herniation and small bowel obstruction (SBO) can occur. The small intestine can herniate through defects necessarily created during bowel reconstruction, leading to partial or complete SBO.

Adjustable gastric banding, a purely restrictive procedure and once the most popular bariatric operation, is now one of the least performed. However, it is still performed by some, and a brief discussion of the most common complications is warranted. Several device‐related complications are associated with AGB including band prolapse or slippage, band erosion, and tubing and port problems.

Biliopancreatic diversion with duodenal switch has been proven to be the most effective bariatric operation in terms of excess weight loss and comorbidity resolution. However, the technical challenges and slightly higher perioperative morbidity make primary use of BPD‐DS less popular than RYGB and SG, and it is more often used as a revisional operation. As with all bariatric operations, leaks are the most feared complications. Enteric leaks can occur at the anastomosis and at any of the suture or staple lines. However, as with SG, the staple line of the gastric sleeve at the level of the angle of His is the most common location. Stricturing of the sleeve gastrectomy or duodenoileostomy can also occur, which may lead to obstruction. Internal herniation through iatrogenic mesenteric defects can lead to bowel incarceration and SBO. Another variant of BPD‐DS, SADI‐S has a comparable complication profile, with possibly a lower rate of internal herniation and malnutrition risk.