Pylephlebitis Secondary to Proctitis in a Patient With Schizophrenia and Polysubstance Use Disorder.

Pylephlebitis is a rare but potentially life-threatening condition, typically resulting from intra-abdominal infections. We present the case of a 60-year-old woman with schizophrenia and polysubstance use disorder who was admitted for altered mental status and subsequently diagnosed with Bacteroides fragilis bacteremia and pylephlebitis in the setting of severe proctitis. Her diagnostic evaluation was complicated by psychiatric comorbidities, unreliable history, and limited collateral information. Imaging revealed extensive thrombus in the inferior mesenteric and superior rectal veins, with nonocclusive extension into the splenic and superior mesenteric veins. She was treated with prolonged broad-spectrum antibiotics and anticoagulation. This case illustrates the diagnostic challenges of pylephlebitis in patients with complex psychosocial backgrounds and highlights proctitis as a rare but plausible etiology of portal venous thrombosis.