Teaching Case

A 76-year-old male patient was hospitalized for sepsis following fever, vomiting, confusion, and hypotension. Blood tests revealed leukocytosis (16,60 WBC x 10³/µl) and elevated CRP levels (14.26 mg/dl). Past medical history included arterial hypertension, benign prostatic hyperplasia, diverticulosis, previous surgical interventions for intersphincteric anal fistula and appendicectomy. A chest-abdomen CT scan showed uncomplicated diverticulitis. After 7 days a clinical deterioration prompted to perform ultrasound (US) followed by contrast-enhanced CT.

Baseline CT showed uncomplicated diverticulitis with sigmoid mural thickening and minimal paracolic fat inflammation, with no signs of perforation or free fluid in the pelvis (Figure 1).

After clinical deterioration, US showed gas in the liver, not clearly distinguishable if at the level of the portal branches or in the biliary tract (Figure 2); the Doppler signal in the portal vein (PV) was discontinuous (Figure 3). Also, abundant free fluid in the pelvis was detected.

US was followed by a second contrast-enhanced CT scan, which detected increased inflammation of the sigmoid tract, with multiple diverticula, paracolic fat inflammation, and abundant free fluid (Figure 4).

CT also confirmed gas and thrombus in the portal-mesenteric system, extending from the inflamed diverticulum to the inferior mesenteric vein, the superior mesenteric vein (anatomical variant Thomson 3), and the portal branches, compatible with septic thrombophlebitis of the portal vein also known as pylephlebitis (Figures 5-8). Pleural effusion was also present on CT.

The patient underwent left hemicolectomy.

Pylephlebitis refers to septic thrombophlebitis that affects the PV and its tributaries. It is usually the consequence of infective processes involving abdominal organs drained by the porto-mesenteric venous system – most commonly diverticulitis and appendicitis – and it may lead to systemic sepsis, liver abscesses, and other life-threatening complications [1].

The incidence is estimated to range from 0.37 to 2.7 cases per 100,000 individuals per year [2].

Diagnosis can be challenging due to its rare occurrence and the non-specific nature of its symptoms, which can include fever, abdominal pain, nausea, and vomiting [3]; these symptoms are not different from the ones seen in conditions causing pylephlebitis itself.

CT allows in most cases prompt detection, evaluation of the extent of thrombosis, and localization of the source of the infective process; however, in most cases, the detection is incidental without a clinical suspicion of pylephlebitis.

The demonstration of gas and thrombus in the PV and its tributaries is the key finding that leads to the diagnosis of pylephlebitis. US can detect the presence of gas in the intrahepatic branches of the PV (hyperechoic spots) and thrombus (echogenic material in the PV lumen). In addition, Doppler can confirm alterations in PV flow. CT scan in the venous phase is the best imaging technique for detecting key findings with high precision and for localizing septic foci [4]. Gas in the intrahepatic portal branches must be distinguished from pneumobilia. The key difference between these two findings is that gas in portal vein branches is usually peripherally distributed, whereas pneumobilia is more centrally distributed.

Pylephlebitis can either be caused by a single pathogen or a polymicrobial infection (E. coli, Streptococcus, Bacterioides spp.) [2], thus requiring the use of broad-spectrum antibiotics. Anticoagulation can be used, although no clear indications are provided [5]. The septic foci are often treated surgically or percutaneously. Interventional vascular procedures such as thrombectomy can be considered [2]. The latest reviews have observed a reduction in mortality, which reached up to 19% before 2010 and subsequently decreased to less than 10%; this data could indicate an improvement in the diagnosis and treatment of this condition [5].

Pylephlebitis is a rare but potentially life-threatening condition, which can complicate any abdominal or pelvic infection drained by the portal system. Imaging, in particular CT scan, is critical for the diagnosis to establish rapid treatment.

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