Teaching Case

A 71-year-old man with multinodular HCC with peritoneal carcinomatosis secondary to alcoholic cirrhosis under treatment with Atezoluzumab-Bevacizumab was previously diagnosed varicose veins and gastropathy secondary to portal hypertension. He is smoker of 20 cigarettes/day, and heavy drinker, with abstinence periods.

A follow-up abdominal multiplanar CT scan was performed. Apart from the progression of the primary tumour, signs of portal hypertension with onset of moderate ascites were found. Development of paraesophageal and oesophagal varices, perisplenic collateral circulation, and large pericardiophrenic varices from the left portal vein (Fig. 2-4)

Portal hypertension (PHTN) is characterized by a pathological increase in portal venous pressure. Due to this excessive intrahepatic pressure (in this case, related to advanced cirrhosis) the portal blood flow becomes hepatofugal, being redirected to alternative low-pressure systemic veins, leading to the formation of portosystemic collateral vessels (PSCV) [1].

The most common PSCVs described are gastro-oesophageal and paraesophageal collaterals, gastrorenal, splenorenal, and periumbilical shunts (Fig. 1) [2].

Since the implementation of multiplanar CT, unusual pathways of portosystemic anastomoses have been described. The detection of typical and atypical portosystemic shunts is vital for the patient's prognosis due to their relation with variceal bleeding and hepatic encephalopathy. 

Embryological portosystemic anastomosis between the portal and systemic circulation exists at various sites in normal healthy humans. In pathological situations, these large shunts can be divided into intrahepatic, transhepatic (for example: enlarged paraumbilical vein, right and left infradiaphragmatic) and extrahepatic (for example gastrorenal, splenorenal, and gastrocaval) [3].

In this case, we focus on the left infradiaphragmatic shunt (also described as left triangular ligament shunt) [4]. In this unusual entity, the left lateral branches of the portal vein communicate with the left inferior phrenic vein at the left triangular ligament. This shunt drains into the inferior vena cava (IVC) or the left renal vein through intercostal veins or the left pericardiophrenic veins. In patients with portal hypertension, hepatofugal flow through this communication is observed (Fig. 2-4).

Multiplanar CT is a very useful tool for the diagnosis of these unusual shunts. It is possible to increase the diagnostic accuracy using the MipPR and multiplanar reconstructions.

Unusual portosystemic shunts can be seen in CT examinations in patients with or without clinical symptoms. Radiologists should be aware of the imaging findings of these unusual portosystemic shunts. Description of unusual portosystemic shunts is essential for transplant surgeons in the surgical approach. Their accurate identification is imperative in therapeutic decision-making. In addition, understanding their anatomy may help to avoid potential complications related to interventional radiological procedures and surgery.