ISSN 2398-2950      

Congenital portosystemic shunt (CPSS)


Ed Hall

Mickey Tivers

Synonym(s): Portocaval shunt, PSS


  • Cause: congenital vascular anomaly connecting the portal blood system to the systemic circulation. This allows blood from the gastrointestinal tract to bypass the liver. 
  • Primarily young cats.
  • Signs:
    • Variable and non-specific, can be intermittent.
    • Central nervous system - depression/hyperactivity, head pressing, pacing/circling, stupor, ataxia, blindess, seizures, coma, ptyalism.
    • Gastrointestinal - vomiting, diarrhea, anorexia.
    • Other - small or stunted, poor body condition score,  polyuria/polydipsia, intolerance to sedatives and anesthetic drugs, urolithiasis.
  • Diagnosis: history, age, clinical signs, pre and postprandial bile acids, ultrasonography, intra-operative mesenteric portovenography, CT angiography, MRI angiography.
  • Treatment: surgical attenutation of shunt (ligation, ameroid constrictor placement, cellophane banding). Medical management prior to surgery or, in long-term cases where surgery impossible/failed/declined by owners.
  • Prognosis: good if surgery successful.
    Print off the owner factsheet on Congential portosystemic shunt  Congenital portosystemic shunt  to give to your client.



  • Congenital anomalies that can take two forms:
    • Extrahepatic:
      • More common.
      • Abnormal vessel branches from portal vein or tributary before it enters the liver.
      • Left gastric vein to vena cava most common in cats. Other forms include portocaval and porto-azygous.
      • Represents an abnormal functional communication between the vitelline and cardinal venous systems.
    • Intrahepatic:
      • Arises from an intrahepatic portal vein branch and thus lies wholly or partly within the liver parenchyma.
      • Classified according to division of the liver that is affected - left, right or central.
      • Left is most common and takes the form of a patent ductus venous (PDV) which results from failure of the ductus venosus to close following birth.
      • The origin of other forms of intrahepatic shunts is unclear.


  • Abnormal communication between portal and systemic blood systems allows blood containing toxic or harmful substances to bypass liver where they would normally be metabolized. This results in increased levels of toxins in the systemic circulation leading to hepatic encephalopathy:
    • Clinical signs relating to central nervous system.
    • Multifactorial - factors act synergistically.
    • Ammonia is major factor in hepatic encephalopathy. Produced from urea by anaerobic bacterial in gastrointestinal tract (colon).
    • Other factors include aromatic amino acids (phenylalanine, tyrosine, tryptophan and methionine), central nervous system inhibitors (GABA and GABA receptors), mercaptans and short chain fatty acids.
    • Signs of hepatic encephalopathy can be triggered by a high protein meal, gastrointestinal bleeding or the use of sedative or anesthetic drugs.
  • Reduced hepatic blood supply results in a failure of normal liver growth and development and results in functional hepatic insufficiency:
    • Ability to metabolize uric acid reduced. This results in increased serum ammonia and uric acid which is excreted in the urine. Ammonium biurate crystals form and can cause lower urinary tract signs.
    • Hypoalbuminemia Hypoproteinemia.
    • Intermittent hypoglycemia.
    • Electrolyte abnormalities.
    • Stunted growth.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Cabassu J, Seim H B 3rd, Macphail C M et al (2011) Outcomes of cats undergoing surgical attenuation of congenital extrahepatic portosystemic shunts through cellophane banding: 9 cases (2000-2007). JAVMA 238 (1), 89-93 PubMed.
  • Tivers M & Lipscomb V (2011) Congenital portosystemic shunts in cats. Investigation, diagnosis and stabilisation. J Fel Med Surg 13 (3), 173-184 PubMed.
  • Tivers M & Lipscomb V (2011) Congenital portosystemic shunts in cats. Surgical management and prognosis. J Fel Med Surg 13 (3), 185-194 PubMed.
  • Brown J C Jr., Chanoit G & Reeder J (2010) Complex extrahepatic portocaval shunt with unusual caval features in a cat: computed tomographic characterisation. JSAP 51 (4), 227-230 PubMed.
  • Lipscomb V J, Lee K C, Lamb C R et al (2009) Association of mesenteric portovenographic findings with outcome in cats receiving surgical treatment for single congenital portosystemic shunts. JAVMA 234 (2), 221-228 PubMed.
  • Lipscomb V J, Jones H J & Brockman D J (2007) Complications and long-term outcomes of the ligation of congenital portosystemic shunts in 49 cats. Vet Rec 160 (14), 465-470 PubMed.
  • Hunt G B, Kummeling A, Tisdall P L et al (2004) Outcomes of cellophane banding for congenital portosystemic shunts in 106 dogs and 5 cats. Vet Surg 33 (1), 25-31 PubMed.
  • Havig M & Tobias K M (2002) Outcome of ameroid constrictor occlusion of single congenital extrahepatic portosystemic shunts in cats: 12 cases (1993-2000). JAVMA 220 (3), 337-341 PubMed.
  • Kyles A E, Hardie E M, Mehl M et al (2002) Evaluation of ameroid ring constrictors for the management of single extrahepatic portosystemic shunts in cats: 23 cases (1996-2001). JAVMA 220 (9), 1341-1347 PubMed.
  • Tillson D M & Winkler J T (2002) Diagnosis and treatment of portosystemic shunts in the cat. Vet Clin North Am Small Anim Pract 32 (4), 881-899 PubMed.
  • Weisse C, Schwartz K, Stronger R et al (2002) Transjugular coil embolization of an intrahepatic portosystemic shunt in a cat. JAVMA 221 (9), 1287-1291 PubMed.
  • White R N & Burton C A (2001) Anatomy of the patent ductus venosus in the cat. J Fel Med Surg (4), 229-233 PubMed.
  • Wolschrijn C F, Mahapokai W, Rothuizen J et al (2000) Gauged attenuation of congenital portosystemic shunts: Results in 160 dogs and 15 cats. Vet Q 22 (2), 94-98 PubMed.
  • Forster-van Hijfte M A, McEvoy F J, White R N et al (1996) Per rectal portal scintigraphy in the diagnosis and management of feline congenital portosystemic shunts. JSAP 37 (1), 7-11 PubMed.
  • Lamb C R, Forster-van Hijfte M A, White R N et al (1996) Ultrasonographic diagnosis of congenital portosystemic shunt in 14 cats. JSAP 37 (5), 205-209 PubMed.
  • Vogt J C, Krahwinkel D J, Bright R M et al (1996) Gradual occlusion of extrahepatic portosystemic shunts in dogs and cats using the ameroid constrictor. Vet Surg 25 (6), 495-502 PubMed.
  • White R N, Forster-van Hijfte M A, Petrie G et al (1996) Surgical treatment of intrahepatic portosystemic shunts in six cats. Vet Rec 139 (13), 314-317 PubMed.
  • VanGundy T E, Boothe H W & Wolf A (1990) Results of Surgical-Management of Feline Portosystemic Shunts. JAAHA 26 (1), 55-62 VetMedResource.
  • Blaxter A C, Holt P E, Pearson G R et al (1988) Congenital Portosystemic Shunts in the Cat - a Report of 9 Cases. JSAP 29 (10), 631-645 Wiley Online Library.

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