Transient metabolic hyperammonaemia in young Irish wolfhounds

Abstract

Inherited portosystemic shunts occur in 2 to 3 per cent of Irish wolfhounds and are associated with high venous ammonia concentrations and signs of hepatic encephalopathy. Moreover, the vast majority of Irish wolfhound pups without signs of hepatic encephalopathy have moderate hyperammonaemia. The aim of this study was to investigate whether the increased ammonia levels in these clinically healthy dogs are caused by low-grade portosystemic shunting, and whether the hyperammonaemia persists in adulthood. The fasting venous ammonia concentration and the fraction of portal blood by-passing the liver, expressed as the shunt index (SI) were measured in 42 Irish wolfhound pups, and the dogs with high SI values were examined post mortem. The ammonia concentration was also measured in 25 adult Irish wolfhounds in which it had been measured when they were seven to eight weeks old. Eleven of the 42 pups had a portosystemic shunt, as evidenced by a high SI (mean 0.82, range 0.12 to 1.00, normal range 0.01 to 0.05) and by post mortem examination. Their mean ammonia concentration was 249 mumol/litre (range 121 to 350). The 31 pups with a normal SI (mean 0.025, range 0.00 to 0.05) had a mean ammonia concentration of 93 mumol/litre (range 51 to 125). In the 25 dogs in which the ammonia concentration was measured twice, the mean concentration at seven to eight weeks of age was 77 mumol/litre (range 47 to 115) and in the adults it was 17 mumol/litre (range 6 to 27) at a mean age of 3.1 years (range 1.0 to 8.9). These results show that Irish wolfhounds with ammonia concentrations > 125 mumol/litre had a portosystemic shunt, whereas the hyperammonaemia in dogs with ammonia concentrations < 120 mumol/litre was transient and of metabolic origin.

Putative intestinal hyperammonaemia in horses: 36 cases

“…1996). Transient HA has been reported in Irish wolfhound pups and a similar syndrome has been observed in a mature German Shepherd dog (Meyer et al . 1996; Lobetti et al .…”

Transient Hyperammonemia Due to Urea Cycle Enzyme Deficiency in Irish Wolfhounds

“…However, it has been noted that a proportion of the screened dogs reveal a transient hyperammonemia phase of up to several months, in the absence of portosystemic shunting. 6 It was suggested that this might imply a breed-associated metabolic cause for hyperammonemia. The aim of the current study was to further characterize the previously observed transient hyperammonemia in Irish Wolfhounds and elucidate the responsible inborn error of metabolism.…”

Ultrasonographic findings in dogs with hyperammonemia: 90 cases (2000–2002)

“…5 The etiopathogenesis of CPSSs is obscure, except that left-sided intrahepatic CPSSs are believed to represent persistence of the ductus venosus. 11,12 Less common causes of hyperammonemia in dogs include transient physiologic hyperammonemia in healthy Irish Wolfhound pups 13 and conditions in which urine that contains ammonia as a result of the activity of urea-splitting microorganisms is absorbed into the systemic circulation. This could happen in dogs with a ruptured urinary bladder or urethra 14 or after surgical ureterocolonic anastomosis.…”

“…26 In addition, ultrasound-guided core biopsy of the liver was performed, and specimens were submitted for histologic examination.…”