Rectal ammonia tolerance test in the evaluation of portal circulation in dogs with liver disease.

An ammonia tolerance test (ATT) is described in control dogs and in patients affected by liver disease with or without portosystemic collateral circulation. The administration of a 5 per cent ammonium chloride solution rectally proved to be preferable to oral administration. A statistically significant difference was shown between the results of the ATT in patients with and those without portal shunts, but not between control dogs and patients without portal collateral circulation. A simplified ATT is proposed in which venous ammonia determinations are made before and 20 and 40 minutes after rectal administration of 5 per cent ammonium chloride solution at a dose of 2 ml/kg bodyweight.