The Rex Block, also known as the Meso-Rex Bypass or Rex Shunt, is a specialized surgical procedure developed primarily for children. Its purpose is to correct abnormal blood flow to the liver caused by a blockage in the main vein leading into the organ. This reconstruction aims to restore the natural, forward-flowing supply of blood to the liver tissue (hepatopetal flow). By establishing this new pathway, the procedure effectively resolves high blood pressure in the portal system. The Rex Block is considered a restorative treatment because it addresses the underlying circulation problem.
Understanding Portal Hypertension in Children
The Rex Block is typically necessitated by Extrahepatic Portal Vein Obstruction (EHPVO), the most common cause of high blood pressure in the portal vein system in children. The portal vein collects nutrient-rich blood from the stomach, intestines, spleen, and pancreas, delivering it directly to the liver. When the main trunk of this vein is blocked, blood backs up into surrounding veins.
This back-up is called portal hypertension. The body attempts to compensate by forming a network of small veins, known as a cavernoma, around the blocked area. Since this network is insufficient, the high pressure forces blood into alternative, thin-walled vessels, particularly those lining the stomach and esophagus. These swollen vessels, called varices, are prone to rupture and can cause life-threatening internal bleeding, the most serious symptom of EHPVO. High pressure also causes the spleen to enlarge (splenomegaly), which may lead to low blood cell and platelet counts.
The Surgical Mechanism of the Rex Block
The Rex Block procedure bypasses the obstructed segment of the main portal vein to restore proper blood flow to the liver. Surgeons create a new conduit using a segment of the patient’s own vein, often the internal jugular vein harvested from the neck. This vein graft connects the superior mesenteric vein in the abdomen to a specific remnant of the left portal vein within the liver.
This intrahepatic remnant is called the Rex Recess, located deep within the liver. Creating this shunt reroutes the nutrient-rich blood supply around the blockage and directly into the liver’s internal circulation. The successful bypass immediately lowers the portal pressure outside the liver. This ensures the liver receives necessary blood flow, allowing the organ to function normally and preventing long-term complications.
Post-Operative Care and Long-Term Prognosis
Following Rex Block surgery, patients typically require about one week of hospitalization for initial recovery and monitoring. Post-operative anticoagulant medication is prescribed temporarily to prevent blood clots and support the patency of the newly created shunt.
The long-term outlook after a successful Rex Block is positive, with reported shunt patency rates exceeding 90% in specialized centers. Once the shunt remains functional, portal hypertension symptoms resolve quickly. This includes eliminating varices and the risk of bleeding, along with a significant reduction in spleen size. Lifelong monitoring, usually via regular ultrasounds, is necessary to ensure the shunt remains open. While complications like shunt stenosis (narrowing) or thrombosis (clotting) can occur, they are often manageable with early detection.