Petersen’s hernia is a complication that occurs after gastric bypass surgery and consists of a protrusion of intestinal loops through a defect formed between the alimentary limb and the transverse mesocolon. It has a low incidence, estimated between 0.2% and 3% of patients undergoing this surgery. Symptoms are very nonspecific (abdominal pain, vomiting, intestinal obstruction) and are often diagnosed during exploratory laparotomy. Treatment is always surgical.

We present the case of a 42-year-old woman with a history of gastric bypass surgery 7 years earlier, who presents to the emergency department with a 5-day history of epigastric pain associated with vomiting of food content and one bowel movement containing fresh blood. Upon arrival at the emergency department, she presents with overt rectal bleeding and associated arterial hypotension (BP 60/40 mmHg). Given the suspicion of a rapid transit source, an urgent gastroscopy is performed, which shows no blood residue or lesions likely to bleed. The following day, a colonoscopy is performed, revealing blood remnants throughout all explored segments, appearing more abundant in the left colon and rectum, where some diverticula are observed, although no active bleeding site is identified. Subsequently, the patient develops new rectal bleeding with hemodynamic instability and increased abdominal pain. A CT angiography is performed, showing enterocolitis (jejunum, ileum, and right hemicolon) of probable ischemic etiology in the context of congestion caused by venous thrombosis (portal vein and the ileocolic, middle colic, and right colic branches of the superior mesenteric vein) secondary to a Petersen’s hernia. The patient ultimately undergoes surgical intervention with adequate reduction of the herniated contents and closure of the Petersen’s space, with good postoperative evolution.

Although presentation as digestive hemorrhage in this condition is rare, in a patient with a history of gastric bypass, inconclusive endoscopic studies, and lack of clinical improvement, this entity must be considered in the differential diagnosis. Delayed diagnosis increases morbidity and mortality in these patients. A multidisciplinary approach with surgeons and radiologists can be useful in guiding management of this condition.