Introduction: Recently, One anastomosis gastric bypass (OAGB) or mini-gastric bypass has a widespread acceptance internationally. This may be attributed to its technical simplicity and effective weight loss. However, this is associated with emerging new complications. We here in presenting a case of an incarcerated Petersen's hernia after laparoscopic one anastomosis (Mini) Gastric Bypass that was emergently managed laparoscopically with a positive outcome.

Presentation: A 35-year-old female presented to ED with recurrent cramping umbilical pain that became intense and associated with nausea and vomiting in the last 24 hours. She had a one-anastomosis gastric bypass 2 years ago. She lost 80 pounds since surgery with her current weight is 164 pounds. She was tachycardic 110/min with abdomen tenderness. Labs were unremarkable. Abdominal CT scan showed a rotation of mesenteric vessels suggestive of internal hernia.

Procedure: Diagnostic laparoscopic confirmed the herniation of cecum and terminal ileum through the Petersen's space. The space between the mesentery of small bowel loops of gastrojejunostomy and the transverse colon mesentery. The incarcerated bowel was successfully reduced by being pushed carefully from left to right under both afferent and efferent limbs. The bowel found to be viable and therefore no resection was required. The Petersen's defect was closed with nonabsorbable running suture. The patient did well. Went home on POD# 2.

Conclusion: Petersen hernia is a potential complication after one anastomosis gastric bypass. When suspected, emergent laparoscopy is mandatory for diagnosis and treatment to avoid bowel necrosis from close loop obstruction.