Spontaneous mesenteric hematoma mimicking a tumor on PET/CT

Spontaneous mesenteric hematoma (SMH) is a rare and often underrecognized cause of acute abdominal pain, characterized by bleeding within the mesentery without any antecedent trauma, aneurysmal rupture, or prior surgery. Its nonspecific presentation and radiologic resemblance to neoplastic or inflammatory masses make diagnosis particularly challenging. We report the case of a 62-year-old male who presented with a 2-day history of epigastric pain radiating to the right lower quadrant. Initial computed tomography (CT) revealed a soft tissue mass at the root of the mesentery, inseparable from the duodenojejunal junction, with surrounding fat stranding and mesenteric thickening. The differential diagnosis included small bowel adenocarcinoma, lymphoma, and desmoid tumor. Ultrasound-guided biopsy revealed only blood and benign mucosal fragments without malignancy.The patient was not receiving anticoagulant or antiplatelet therapy and had no known coagulopathy. Subsequent magnetic resonance imaging (MRI) demonstrated a slightly hyperintense lesion on T2 STIR, heterogeneous T1 hyperintensity, diffusion restriction, and peripheral capsular enhancement. Positron emission tomography/computed tomography (PET/CT) scan showed peripheral FDG uptake, favoring a benign etiology. Given the absence of malignant features, conservative management was adopted. Follow-up MRI after one week showed a 50% reduction in lesion size, confirming a resolving mesenteric hematoma. This case highlights the diagnostic complexity of SMH, which may closely mimic mesenteric neoplasms on imaging. The use of multimodal imaging particularly MRI and PET/CT was pivotal in avoiding unnecessary surgery and confirming spontaneous resolution. Awareness of this entity is essential to ensure appropriate management, as conservative treatment remains safe and effective in hemodynamically stable patients.