Appendicitis-Associated Pylephlebitis With Superior Mesenteric Vein Thrombosis and Portal Vein Extension: A Case Report.

Appendicitis-associated suppurative pylephlebitis with superior mesenteric vein (SMV) thrombosis is an uncommon but clinically important complication that can be identified on contrast-enhanced computed tomography. A 47-year-old man presented with seven days of right lower quadrant abdominal pain, leukocytosis, and elevated inflammatory markers. Contrast-enhanced abdominopelvic CT demonstrated acute appendicitis without CT signs of perforation or bowel ischemia, together with occlusive thrombosis of the superior mesenteric vein extending into mesenteric venous branches. The patient underwent diagnostic laparoscopy with conversion to open appendectomy for source control, followed by broad-spectrum antibiotics and anticoagulation. Follow-up CT 10 days later demonstrated persistent SMV thrombosis and a new postoperative abscess in the appendiceal bed. A subsequent CT five days later showed an interval decrease in the abscess size but progression of thrombus to the origin of the portal vein. This case highlights the importance of systematic evaluation of the portomesenteric venous system on CT in patients with appendicitis and the value of serial imaging for detecting thrombus progression and postoperative septic complications that may directly affect management and prognosis.