What is the difference between central and proximal splenorenal (spleen to renal vein) shunts?

Differences Between Central and Proximal Splenorenal Shunts

The central splenorenal shunt connects the splenic vein directly to the renal vein with complete division of the splenic vein, while the proximal splenorenal shunt creates a side-to-side anastomosis between the splenic vein and renal vein without dividing the splenic vein.

Anatomical Differences

• Central Splenorenal Shunt:

  • Involves complete division of the splenic vein
  • End-to-side anastomosis between splenic vein and renal vein
  • Considered a nonselective shunt (total portal decompression)
  • Diverts all splenic and portal blood flow to the systemic circulation

• Proximal Splenorenal Shunt:

  • Side-to-side anastomosis between splenic vein and renal vein
  • Splenic vein remains intact
  • Also considered a nonselective shunt
  • Creates a wider communication between portal and systemic circulation

Hemodynamic Effects

• Central Splenorenal Shunt:

  • Results in complete portal decompression
  • Significantly reduces portal pressure 1
  • May lead to loss of hepatopetal portal flow in most patients
  • Associated with higher risk of hepatic encephalopathy due to complete portal diversion

• Proximal Splenorenal Shunt:

  • Also provides significant portal decompression
  • May maintain some degree of portal flow to the liver
  • Similar hemodynamic effects to central shunts in most cases 2, 3

Clinical Outcomes

Research comparing these shunt types has shown:

• Survival Rates: No significant difference in survival between central and proximal splenorenal shunts (52% 5-year survival for both) 3

• Encephalopathy: Similar rates of post-operative encephalopathy (28% for proximal vs. 26% for distal splenorenal shunts) 3

• Rebleeding Rates: Comparable rebleeding rates (34% for proximal vs. 32% for distal) 3

• Shunt Occlusion: Similar rates of shunt occlusion (7% for proximal vs. 11% for distal) 3

Important Distinctions from Distal Splenorenal Shunt

It's important to note that both central and proximal splenorenal shunts differ significantly from the distal splenorenal shunt:

• The distal splenorenal shunt is a selective shunt that connects the distal splenic vein to the left renal vein while preserving portal flow to the liver
• Distal splenorenal shunts have been shown to better preserve hepatopetal portal flow (88% vs. 5% in nonselective shunts) 4
• Early studies suggested distal splenorenal shunts had lower encephalopathy rates (12% vs. 52% for nonselective shunts) 4

Clinical Implications

When considering these shunts for management of gastric varices:

• Both central and proximal splenorenal shunts are effective at reducing portal pressure and controlling variceal bleeding
• The American College of Radiology notes that surgical portosystemic shunt creation can be effective in managing gastric variceal hemorrhage, with long-term control of hemorrhage achieved in 97-100% of patients 1
• However, these shunts should only be considered at centers with substantial experience operating in the setting of pressurized varices, such as liver transplant centers 1

Pitfalls and Caveats

• Both shunt types carry significant risks of encephalopathy due to their nonselective nature
• Neither should be first-line therapy in most cases of variceal bleeding given the availability of less invasive options (TIPS, BRTO)
• Surgical management should be reserved for patients who have failed other therapies or have specific anatomical considerations
• Careful patient selection is crucial to avoid complications such as portal vein thrombosis 5

In modern practice, these traditional surgical shunts have largely been replaced by TIPS (transjugular intrahepatic portosystemic shunt) procedures, which are less invasive and have similar efficacy for controlling variceal bleeding.