What is a spontaneous spleno(renal) shunt?

Spontaneous Splenorenal Shunt: Definition and Clinical Significance

A spontaneous splenorenal shunt is a portosystemic connection that forms between the splenic vein and the left renal vein, typically developing in patients with portal hypertension as a natural decompression pathway for the portal venous system. 1

Anatomical and Pathophysiological Features

• Spontaneous splenorenal shunts (SSRSs) develop as portosystemic connections that divert blood from the high-pressure portal system (splenic vein) to the lower-pressure systemic circulation (left renal vein) 2
• They occur in approximately 18-19% of patients evaluated for liver transplantation 2
• These shunts can vary in size, with larger shunts (>10mm at the transition into the left renal vein) more likely to cause significant hemodynamic effects 2
• SSRSs represent one type of spontaneous pressurized portosystemic shunt that can develop around portal and splenic veins in patients with portal hypertension 1

Clinical Significance and Complications

• Large SSRSs can cause a "steal phenomenon" where blood is diverted from the liver to the systemic circulation, potentially leading to:

  • Portal flow reduction to the liver 2, 3
  • Increased risk of portal vein thrombosis 3
  • Hepatic hypoperfusion in transplant recipients 2, 3
  • Hepatic encephalopathy due to ammonia and other toxins bypassing hepatic metabolism 1

• In liver transplant recipients, undetected large shunts may contribute to:

  • Allograft dysfunction 2
  • Portal vein thrombosis 3
  • Potential graft failure 2

• Hemodynamic consequences can include:

  • Dilation of the inferior vena cava with hyperkinetic systemic flow 4
  • Secondary hypertrophy of the liver caudal lobe in some cases 4

Diagnostic Considerations

• SSRSs are typically identified through cross-sectional imaging:

  • Contrast-enhanced CT or MRI is recommended for diagnosis and classification 1
  • Doppler ultrasonography can demonstrate flow characteristics and hemodynamic effects 4
  • Indirect splenoportography may show splenomegaly, dilated splenic and portal veins, and the shunt itself 4

• While most commonly associated with cirrhosis and portal hypertension, SSRSs can rarely occur as congenital anomalies in patients without liver disease 5

Management Approaches

• Management depends on clinical context and associated complications:

  • Small shunts often involute spontaneously after liver transplantation when portal pressure normalizes 2
  • Large shunts may require intervention to prevent portal steal syndrome 3

• Interventional options include:

  • Surgical or laparoscopic ligation of the shunt 5, 3
  • Left renal vein ligation during liver transplantation to improve portal venous flow 3
  • Radiological embolization in selected cases 1

• For patients with hepatic encephalopathy due to SSRSs:

  • Medical management with rifaximin and lactulose 6
  • Consideration of shunt closure in refractory cases 6
  • Liver transplantation for intractable portosystemic encephalopathy 1, 6

Special Considerations

• Preoperative identification of SSRSs is crucial before any abdominal surgery to avoid accidental injury and excessive bleeding 5
• In liver transplant candidates, careful evaluation of shunt size and hemodynamics is essential for surgical planning 2, 3
• The presence of SSRSs should be investigated in patients with unexplained hyperammonemia or encephalopathy symptoms in the absence of significant liver disease 1, 6