Background: The roux en Y gastric bypass (RYGB) has potent antidiabetic effects, increasing its efficacy in controlling morbidity associated with obesity. There have been several reports of profound hypoglycemia resulting from gastric bypass in non-diabetic patients. The authors reviewed their experience with managing hypoglycemia in the gastric bypass population.
Methods: We performed RYGB in 401 patients between Dec 1, 2000 and Dec 1, 2005 and have prospectively followed all patients by an approved protocol. Thirteen patients have complained of recurrent hypoglycemic symptoms at a median time period of 6 months after RYGB (range 3-33). Median age at operation was 39 years (range 18-62). Mean (SD) preoperative BMI was 45.5 (4.8) and reached nadir at 26.1 (3.4) before a weight plateau at 27.5 (3.5). One patient is male and one patient had non-insulin dependent diabetes preoperatively. Hyperinsulinemic hypoglycemia was confirmed by a mixed meal test in six patients. Two female patients from our center, and two women operated on elsewhere (in 1979 and 2002 respectively), were observed to have recurrent critical hypoglycemic episodes unresponsive to dietary and medical management, and underwent evaluation for pancreatogenous hyperinsulinemic hypoglycemia. This consisted of high resolution CT scan of the pancreas, and intra-arterial calcium stimulated measurement of hepatic venous insulin. In two patients, insulin levels doubled with gastroduodenal and splenic arterial infusion, and both underwent pancreatic resection distal to the pancreatic neck. In two patients, insulin levels doubled only with splenic artery infusion, and one patient underwent pancreatic resection distal to the mid-body - where the roux limb crossed the pancreas. One patient has declined operation.
Results: In 21 cumulative months after pancreatic resection (range 3-12) one patient has had two hypoglycemic episodes related to late dumping of sweets, and one patient requires low dose insulin. Pathology of pancreatic specimens fulfilled diagnostic criteria for nesidioblastosis in all cases.
Conclusions: Recurrent hypoglycemic episodes are infrequent after RYGB, and most can be managed conservatively. Pancreatogenous hyperinsulinemic hypoglycemia is rarely seen after RYGB and can result in life-threatening hypoglycemia, but responds to pancreatic resection, at a level determined by intra-arterial calcium stimulated measurement of hepatic venous insulin.