Photo Credit: iStock.com/Ege Pamukcu
Gastric bypass surgery has proven to be a highly effective treatment for obesity, offering substantial weight loss and improvements in obesity-related conditions. However, like any major surgical intervention, it carries a range of potential risks and complications that must be considered when determining its appropriateness for a given patient.
One significant concern is malnutrition. The surgery alters both the quantity and quality of food intake by limiting stomach capacity and nutrient absorption. As a result, patients are at risk for deficiencies in essential vitamins and minerals, such as iron, calcium, and vitamins B1 and B12. Ongoing nutritional monitoring and supplementation, ideally under the guidance of a registered dietitian, are essential to prevent long-term complications.
Another potential complication is stomal stenosis, a narrowing of the connection between the stomach and intestine created during the Roux-en-Y procedure. This can lead to symptoms such as vomiting after eating or drinking. Prompt medical attention is required, as early intervention can typically resolve the issue with minimal invasiveness.
Dumping syndrome is also a relatively common postoperative issue. It occurs when undigested food rapidly passes into the small intestine, leading to a cascade of symptoms. Early dumping happens within 15–20 minutes after eating and is characterized by nausea, bloating, and palpitations, while late dumping occurs 1–3 hours post-meal and may involve hypoglycemic-like symptoms such as fatigue, confusion, and fainting. Dietary adjustments often help alleviate these symptoms.
The most severe risk is peritonitis, resulting from a gastric leak post-surgery. This potentially life-threatening condition manifests as fever, severe abdominal pain, and signs of systemic infection. Immediate medical evaluation is critical if these symptoms arise.
Understanding these risks helps ensure that patients undergoing gastric bypass are well-informed and equipped to manage complications promptly and effectively.
A Look Into Rare Complications
In one case report presented at AACE 2025, Sacoto et al. present a 63-year-old woman with a history of Roux-en-Y gastric bypass (RYGB) who experienced recurrent symptomatic hypoglycemia—both fasting and post-prandial. During a mixed meal test, her glucose level dropped precipitously from 51 mg/dL to 25 mg/dL within an hour, leading to seizures. A 72-hour fasting test was poorly tolerated. Despite trials of acarbose, diazoxide, and phenytoin, her symptoms persisted. Multiple imaging modalities, including MRI, endoscopic ultrasound, and PET/CT with Ga-68 dotatate, failed to identify a discrete lesion. A selective arterial calcium stimulation test (SACST) showed elevated insulin levels in the splanchnic circulation but did not localize a clear source.
With gastric bypass reversal deferred, a subtotal pancreatectomy is planned.
The case underscored the diagnostic complexity of differentiating nesidioblastosis from insulinoma in post-RYGB patients. Nesidioblastosis, a rare complication after RYGB, results from exaggerated secretion of incretin hormones such as GLP-1, GIP, and ghrelin, leading to diffuse beta-cell hyperplasia and hyperinsulinemic hypoglycemia. While insulinomas are focal neoplasms, they may also be radiographically occult. In this patient, biochemical testing, imaging, and SACST failed to clearly distinguish between the two.
Ultimately, histopathological examination following pancreatectomy will be definitive.
The authors emphasized that, although rare, nesidioblastosis and insulinoma must be considered in patients presenting with hypoglycemia after bariatric surgery.
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