Validation of a radioassay for the determination of serum folate and cobalamin concentrations in dogs

Determinations of serum folate and cobalamin concentrations in dogs have proved of considerable value for the identification and characterisation of chronic small intestinal disorders, but the microbiological assays used are time-consuming and technically demanding. Dual isotope radio-assays are more convenient and have been developed for the determination of folate and cobalamin in human beings. This study has evaluated such an assay for the determination of serum folate and cobalamin concentrations in dogs by direct comparison with microbiological assays used previously. Assays were performed on samples from 77 dogs, including controls and animals with confirmed or suspected chronic small intestinal disease. Regression analysis demonstrated a significant relationship between the two assays for serum folate concentrations (R=0–85; P=0–0001) and a definite trend for radioassay to give lower results than bioassay. There was also a significant relationship between bioassay and radioassay data for serum cobalamin (R=0–91; P=0–0001) with comparable absolute values for these two assays. Radioassay of serum samples from 31 clinically healthy dogs gave control ranges of 3–7 to 8-8 4mUg/litre for folate and 205 to 490 ng/litre for cobalamin. These ranges were similar to those calculated by comparison with the established ranges for bioassay using regression analysis, which predicted ranges of 4-4 to 8-4 μg/litre and 217 to 398 ng/litre for radioassay of serum folate and cobalamin, respectively. These data indicate that a dual isotope radioassay of serum folate and cobalamin may be used for dogs, and emphasise the need for laboratories to validate and establish their own control ranges for different assays.     

Plasma amino acid analysis in dogs with experimentally induced hepatocellular and obstructive jaundice

Plasma amino acid concentrations were determined weekly for 4 weeks in 6 sham-operated control dogs, in 6 sham-operated dogs after induction of liver disease with dimethylnitrosamine (DMNA), and in 6 dogs after surgical ligation of the common bile duct. Results were compared with standard biochemical indices of liver function and with histologic changes in serial liver biopsy specimens. Concentrations of most amino acids increased after 2 weeks in DMNA-treated dogs, whereas they were normal or decreased in bile duct-ligated dogs. With increasing severity of the liver disease, the molar ratio (normal mean +/- SEM = 3.48 +/- 0.14) in DMNA-treated dogs decreased to 2.42 +/- 0.19 by 2 weeks and to 1.17 +/- 0.09 by 4 weeks. The ratio remained normal in bile duct-ligated dogs. Molar ratio and aromatic amino acid concentrations correlated better with hepatic necrosis and inflammation than did standard biochemical indices (eg, bilirubin, liver enzymes). Therefore, plasma amino acid analysis and determination of the molar ratio may be useful in the differential diagnosis of hepatocellular and obstructive jaundice in dogs. A decrease in the molar ratio may reflect portal hypertension and hepatocellular disease.     

Ultrasonographic diagnosis of congenital portosystemic shunt in 14 cats

Twenty-four cats with clinical and, or, clinico-pathological signs compatible with portosystemic shunting were examined prospectively using two-dimensional grey-scale, duplex and colourflow Doppler ultrasonography. Diagnosis of congenital portosystemic shunt was subsequently confirmed in 14 cats using operative mesenteric portography and surgery. Of the 14 affected cats, nine were purebred; eight were male and six female. The mean age at the time of diagnosis was nine months (range four to 27 months). Ultrasonographic evidence of a small liver was present in seven cats (50 per cent); visibility of intrahepatic portal vessels was reduced in three (21 per cent). An anomalous blood vessel was identified ultrasonographically in each cat; in 10 cats (71 per cent) the vessel was observed to originate from the portal vein and drain into the caudal vena cava. Abnormally variable portal blood flow waspresent in eight of the 10 cats in which it was measured. At surgery, six shunts were intrahepatic and eight extrahepatic; the ultrasonographic diagnosis of intra- versus extra-hepatic shunt was correct in 13 cats (93 per cent). No anomalous blood vessels or abnormalities affecting the portal vein were detected ultrasonographically in any of the 10 cats that did not have congenital portosystemic shunting. Hence, the accuracy of ultrasonography for diagnosis of congenital portosystemic shunting in this series was 100 per cent.     

Gastroscopic food sensitivity testing in 17 dogs

Seven of 17 dogs with gastrointestinal signs and suspected dietary intolerance had positive responses to gastroscopic food sensitivity testing (GFST). Five of the non-responders and six of the dogs that responded to GFST were successfully treated with dietary control alone. The seventh dog that responded to GFST had an ileal adenocarcinoma and did not survive to follow-up. Local reactions to GFST included mucosal oedema, mucosal hyperaemia and gastric hyperperistalsis and systemic reactions consisted of hyperventilation and retching. The character of the responses to GFST is consistent with a type 1 hypersensitivity reaction to the food antigen, suggesting that IgE may mediate dietary sensitivity in some dogs. Positive responses to GFST may, therefore, demonstrate gastric mucosal hypersensitivity to food antigens and be useful in formulating therapeutic diets; negative responses need to be interpreted with caution. The limitations of the procedure are that it requires a videoendoscopy system, may significantly add to general anaesthetic time and will only detect immediate reactions.     

Serum bile acid analysis in dogs with experimentally induced cholestatic jaundice

Serum bile acid (SBA) concentration was determined weekly for 4 weeks in dogs with experimentally induced hyperbilirubinemic liver disease. Obstructive jaundice was created in 6 dogs by surgical ligation of the common bile duct, and hepatocellular jaundice was created in 6 sham-operated dogs by administration of dimethylnitrosamine; 6 other sham-operated dogs served as controls. Serum bile acid concentration increased rapidly after bile duct ligation (from 0.6 +/- 0.1 to 69.2 +/- 15.3 mumol/L at 3 days), peaked at 14 days (247.8 +/- 54.1 mumol/L), and then gradually decreased (179.9 +/- 27.1 mumol/L at 28 days). Serum bile acid concentration in dimethylnitrosamine-treated dogs increased more gradually to 38.9 +/- 10.7 mumol/L at 28 days, at which time the serum bilirubin concentration was comparable with that of bile duct-ligated dogs. Mean total SBA values in bile duct-ligated dogs were significantly (P less than 0.01) higher than those in control and dimethylnitrosamine-treated dogs at days 3 through 28, with no overlap of individual values. Serum bile acid concentration at day 28 correlated positively (P less than 0.01) with cholestasis and bile duct proliferation observed in liver biopsy specimens, but did not correlate with necrosis or inflammation. Serum bile acid concentration also correlated positively (P less than 0.01) with serum bilirubin and cholesterol concentrations and with serum alkaline phosphatase and alanine transaminase activities. Results of the study reported here indicated a relationship between SBA concentration and cholestasis in dogs; extrahepatic bile duct obstruction resulted in the highest SBA values.(ABSTRACT TRUNCATED AT 250 WORDS)     

Intestinal permeability and function in dogs with small intestinal bacterial overgrowth

Small intestinal bacterial overgrowth (SIBO) has been reported to occur commonly in dogs with signs of chronic intestinal disease. There are usually few intestinal histological changes, and it is uncertain to what extent bacteria cause mucosal damage. The aim of this study was to apply a differential sugar absorption test for intestinal permeability and function to the objective assessment of intestinal damage in dogs with SIBO. Studies were performed on 63 dogs with signs of chronic small and, or, large bowel disease, in which SIBO (greater than 10⁵ total or greater than 10⁴ anaerobic colony forming units/ml) was diagnosed by quantitative culture of duodenal juice obtained endoscopically. None of the dogs had evidence of intestinal pathogens, parasites, systemic disease or pancreatic insufficiency. Differential sugar absorption was performed by determining the ratios of urinary recoveries of lactulose/rhamnose (L/R ratio, which reflects permeability) and D-xylose/3-O-methylglucose (X/G ratio, which reflects intestinal absorptive function) following oral administration. Dogs with SIBO comprised 28 different breeds, including 18 German shepherd dogs. SIBO was aerobic in 18/63 dogs (29 per cent), and anaerobic in 45/63 (71 per cent). Histological examination of duode-nal biopsies showed no abnormalities in 75 per cent, and mild to moderate lymphocytic infiltrates in 25 per cent of the dogs. The L/R ratio was increased (greater than 0–12) in 52 per cent, and the X/G ratio reduced (less than 0–60) in 33 per cent of the dogs. Differential sugar absorption was repeated in 11 dogs after their four weeks of oral antibiotic therapy. The L/R ratio declined in all 11 dogs (mean ± SD pre: 0–24 ± 0–14; post: 0–16 ± 0–11; P<0–05), but changes in the X/G ratio were more variable. These findings show that SIBO is commonly associated with mucosal damage, not detected on histological examination of intestinal biopsies, and that changes in intestinal permeability following oral antibiotics may be used to monitor response to treatment.     

Comparison of the bacterial flora of the duodenum in healthy cats and cats with signs of gastrointestinal tract disease

OBJECTIVE: To determine whether a colony environment predisposes healthy cats to high bacterial counts, including counts of obligate anaerobes, in the duodenum and whether increased numbers of bacteria could be found in the duodenum of cats with signs of chronic gastrointestinal tract disease. DESIGN: Prospective study. ANIMALS: 20 healthy control cats (10 from a colony environment and 10 pet cats) and 19 cats with a history of chronic gastrointestinal tract disease. PROCEDURE: Undiluted duodenal fluid was quantitatively and qualitatively assessed by bacteriologic culture under aerobic and anaerobic conditions. Serum concentrations of cobalamin and folate were also measured. RESULTS: Significant differences were not detected in the numbers of bacteria found in the duodenum of cats housed in a colony environment, compared with pet cats fed an identical diet prior to sampling. All healthy cats were, therefore, combined into 1 control group. Compared with healthy cats, cats with clinical signs of gastrointestinal tract disease had significantly lower counts of microaerophilic bacteria, whereas total, anaerobic, and aerobic bacterial counts were not significantly different. None of the cats with disease had total bacterial counts higher than expected from the range established in the control cats. Differences were not detected in regard to serum folate or cobalamin concentrations between diseased and healthy cats. CONCLUSIONS AND CLINICAL RELEVANCE: These findings indicated that healthy colony cats and pet cats have high numbers of bacteria in the duodenum, including high numbers of obligate anaerobes. Our findings also suggest that bacterial overgrowth in the small intestine is not a common clinical syndrome in cats with chronic nonobstructive gastrointestinal tract disease.     

Gastrointestinal Lymphoma in 20 Dogs

The records of 20 dogs with histopathologically diagnosed gastrointestinal (GI) lymphoma (LSA) evaluated between 1970 and 1984 were reviewed. Fifteen dogs were considered to have primary GI LSA, while five dogs had GI involvement in association with the multicentric form. Most clinical and laboratory findings were nonspecific, but positive-contrast upper GI radiography was suggestive of GI LSA in all of the dogs evaluated. Nine dogs had extensive lymphocytic-plasmacytic inflammatory infiltrates around the neoplastic foci, resulting in difficulty in obtaining a diagnosis of GI LSA when samples were obtained by endoscopy.