Inherited congenital extrahepatic portosystemic shunts in Cairn terriers

The pathogenesis of congenital portosystemic shunt (CPSS) in dogs still is incompletely understood. In Irish Wolfhounds and Yorkshire Terriers, CPSS is reported to be hereditary. The aim of this study was to investigate a possible genetic basis and the mode of inheritance of CPSS in Cairn Terriers. Between July 1990 and July 2001, 6-week-old pups of the Dutch Cairn Terrier population were screened by measuring venous ammonia concentrations and in the presence of hyperammonemia by ultrasonography, autopsy, portal vein angiography, or exploratory celiotomy. The same successfully operated female was used 3 times in test matings with an unrelated affected male, her unaffected sire, and an affected offspring. The prevalence of CPSS in the general Cairn Terrier population, the direct progeny of frequently used males, and the offspring of the test matings were tested for significant differences. In total, 6,367 Cairn Terriers were screened; 32 males and 26 females had CPSS. In 3 large family groups, significantly higher prevalences were found compared with the general population (P < .0001, P < .0001, and P < .044). The prevalence of CPSS in the offspring of the test matings was significantly higher (P < .002) than in the general population. No sex predisposition occurred among the affected dogs. The higher prevalence of CPSS in the test matings and the 3 family groups compared with the general population indicates that CPSS in Cairn Terriers is a genetic disease. The inheritance is autosomal and most likely polygenic or monogenic with variable expression.