Pylephlebitis, or infective suppurative thrombosis of the portal vein, is a serious condition with significant morbidity and mortality, which can complicate intraabdominal sepsis of any etiology. Although universally fatal in the preantibiotic era , the outcome of this infection has improved somewhat with modern diagnostic and therapeutic modalities. Curiously, however, reports of the diagnosis have increased in the last 15 years, possibly as a result of newer, more sensitive imaging techniques .
The portal vein is formed by the union of the superior mesenteric vein with the splenic veins. The portal system drains blood from the abdominal section of the gastrointestinal tract, with the exception of the lower part of the rectum.
Pylephlebitis begins with thrombophlebitis of small veins draining an area of infection. Extension of the thrombophlebitis into larger veins leads to septic thrombophlebitis of the portal vein, which can extend further to involve the mesenteric veins . In a review of case reports, the superior mesenteric vein was involved in 42 percent . Thrombus involved the splenic vein and intrahepatic branches of the portal vein in 12 and 39 percent of cases, respectively. Mesenteric vein involvement can lead to bowel ischemia, infarction and death.
An associated hypercoagulable state is found in some cases of pylephlebitis. As an example, in one series of 44 cases, 18 were hypercoagulable due to clotting factor deficiencies, malignant conditions, or AIDS .
Pylephlebitis can complicate any intraabdominal or pelvic infection that occurs in the region drained by the portal venous system, especially diverticulitis and appendicitis (figure 1) [2,5-7]. Contiguous infection (eg, cholangitis or infected choledocholithiasis) can also lead to this complication [2,8]. In addition, pylephlebitis has been associated with inflammatory bowel disease [6,9,10], pancreatitis , hemorrhoidal banding , and has occurred as a complication of the intragastric migration of a silicone gastric band  and following a CT-guided liver biopsy . A precipitating focus was identified in 13 of 18 cases (68 percent) in one report .