Post‐prandial serum bile acid concentrations and ammonia tolerance in Maltese dogs with and without hepatic vascular anomalies

Abstract

Post-prandial serum bile acid concentrations were measured in 200 Maltese dogs in an attempt to identify those with subclinical portosystemic shunts. Five of these were later shown to have hepatic pathology or abnormal liver function. In the other 195 Maltese, bile acid concentrations ranged from 1 to 362 mumol.L-1 (mean +/- SD, 70 +/- 50 mumol.L-1; median, 65.0 mumol.L-1). Of these, 79% were above the reference range (0 to 31 mumol.L-1) established from 23 mixed-breed control dogs. It was therefore not possible to determine the prevalence of subclinical portosystemic shunts on the basis of bile acid determinations. Further investigation of liver function was performed to investigate why bile acid concentrations were increased in these dogs. Rectal ammonia tolerance tests were normal in 102 of 106 Maltese tested and liver samples (11 dogs) and plasma biochemistry profiles (9 dogs) demonstrated no significant hepatic disease or dysfunction. Of 2 Maltese with hyperammonaemia after administration of ammonium chloride, one had a large congenital portosystemic shunt that was confirmed at surgery. In the other there were no macroscopic portosystemic communications, but a liver biopsy showed histological changes consistent with microscopic portovascular dysplasia. Total serum bile acid concentrations were consistently lower when assessed by high-performance liquid chromatography than by an enzymatic spectrophotometric method. This discrepancy was substantially larger in Maltese than in control dogs, suggesting the presence of an additional reacting substance in the serum of Maltese dogs.

Outcomes of Cellophane Banding for Congenital Portosystemic Shunts in 106 Dogs and 5 Cats

“…14 Portal scintigraphy was not available at our clinic. Unfortunately, the predisposition of Maltese to congenital portosystemic shunts, the difficulty of interpreting results of bile acid determination in this breed 19 and the restricted availability of facilities for determining blood ammonia levels in regional centers impaired our ability to adequately evaluate some cases postoperatively. Nevertheless, readers should note that liver function tests such as ATT and SBA determination are only reliable when they are performed correctly and these tests may not detect small amounts of portosystemic shunting.…”

“…Rectal ammonia tolerance testing (ATT) was performed by preference, especially in terrier-type dogs where serum bile acid (SBA) determination using a routine enzymatic test can be misleading. 19 Portosystemic shunting was considered to have resolved if ATT was normal (o100 mmol/L after ammonia challenge) or postprandial SBA concentration was o40 mmol/L. 19 If ammonia intolerance or elevated SBA concentrations were encountered, results of serum biochemistry (activity of alanine aminotransferase and alkaline phosphatase, concentrations of blood urea nitrogen, cholesterol, and albumin) were compared with preoperative values as an indirect means of assessing improvement in liver function.…”

“…19 Portosystemic shunting was considered to have resolved if ATT was normal (o100 mmol/L after ammonia challenge) or postprandial SBA concentration was o40 mmol/L. 19 If ammonia intolerance or elevated SBA concentrations were encountered, results of serum biochemistry (activity of alanine aminotransferase and alkaline phosphatase, concentrations of blood urea nitrogen, cholesterol, and albumin) were compared with preoperative values as an indirect means of assessing improvement in liver function. In Maltese dogs, whose owners were unwilling to return for ATT, the results of pre and postoperative biochemical panels were compared to provide an indication of changes in hepatic function.…”

The inheritance of extra‐hepatic portosystemic shunts and elevated bile acid concentrations in Maltese dogs

“…Maltese are another breed at increased risk of having EHPSS (Tisdall et al . ). Typical shunt anatomy connects the left gastric or gastrosplenic vein and the left phrenic vein or CVC cranial to the left renal vein, at the level of the epiploic foramen (Tisdall et al .…”

“…Typical shunt anatomy connects the left gastric or gastrosplenic vein and the left phrenic vein or CVC cranial to the left renal vein, at the level of the epiploic foramen (Tisdall et al . , , White & Parry ). Consistent shunt anatomy supports the notion of an inherited condition (van den Bossche et al .…”