Pylethrombosis is thrombosis of the portal vein or any of its branches. Five cases have been serendipitously detected, four by computed tomography and one by ultrasonography. Two patients had abdominal sepsis. A third patient had apparent acute cholecystitis with choledocholithiasis. The last two patients had a hypercoagulable state, mesenteric venous thrombosis, and enteric infarction that required resection. The newer diagnostic modalities of computed tomography and ultrasound may document unsuspected pylethrombosis. Surgery may be required because of signs of peritonitis, enteric ischemia, or unresolved sepsis. Anticoagulation is indicated for acute thrombosis of the portal or superior mesenteric veins to prevent further extension and enteric ischemia.