Hein P. Meyer

Circulatory disorders of the liver in dogs and cats

This paper presents a review of the literature on hepatic circulation and circulatory disorders of the liver in the dog and cat, and also includes a number of our own not previously published data. Circulatory disorders of the liver are frequently observed in dogs and cats. These disorders can be divided into congenital portosystemic shunts, disorders associated with outflow disturbances, and disorders associated with portal hypertension. Outflow disturbances result in passive congestion of the liver and in both species are mainly due to cardiac failure. Portal hypertension with resultant portosystemic collateral circulation and ascites mainly results from chronic liver disease, particularly cirrhosis. The main vascular disorder resulting in portal hypertension and ascites in the dog is primary hypoplasia of the portal vein.

Improvement of chronic hepatic encephalopathy in dogs by the benzodiazepine-receptor partial inverse agonist sarmazenil, but not by the antagonist flumazenil

Therapeutic modulation of the increased GABAergic tone in chronic hepatic encephalopathy (HE) by the benzodiazepine receptor (BR) antagonist flumazenil (F) has led to conflicting results in humans and animal models for HE. The BR inverse agonist sarmazenil (S) has only been used in animal models of acute HE. Therefore we investigated the effects of intravenous injection of F and S in dogs with chronic HE 8 to 12 weeks after placement of a portocaval shunt and 40% hepatectomy (n=7), compared to sham-operated pair-fed controls (n=7). The HE dogs had hyperammonemia (298±48 μM v 33±3 before surgery (mean±SEM)) and signs of HE at the start of the experiments (0.9±0.1 (scale 0-4)). Three (S3) and 8 (S8) mg/kg of S resulted in a significant improvement of encephalopathy (grade 0.9±0.2 immediately before v 0.5±0.1 after injection (S3) and 0.7±0.1 v 0.3±0.1 (S8)) and increase in mean dominant frequency of the EEC (MDF; 9.1±0.7 Hz v 11.1±0.3 (S3) and 8.9±0.5 v 11.0±0.3 (S8)) in HE dogs, whereas 15 mg/kg of S, 3 and 8 mg/kg of F, and the vehicle had no significant effects. The efficacy of S in these dogs is consistent with an increased GABAergic tone in the pathogenesis of chronic HE. The lack of effects of F makes a role for endogenous benzodiazepines herein unlikely.

Effects of an iodine-restricted food on client-owned cats with hyperthyroidism

The objective of this prospective, multicentre, non-controlled, open-label study was to evaluate the effects of an iodine-restricted food on circulating total thyroxine (TT4) concentrations and clinical parameters in client-owned cats with hyperthyroidism. Two hundred and twenty-five cats were enrolled in the study and adapted to the iodine-restricted food. Data from physical examinations, questionnaires completed by veterinarians and owners, and circulating concentrations of TT4, urea and creatinine were recorded at weeks 0, 4 and 8. The study group included 136 female and 89 male cats (median age 15 years, range 4–21 years). Group 1 (n = 113) had been on previous anti-thyroid medication, while group 2 (n = 112) consisted of newly diagnosed cats. No differences were found between the two groups at any time point. Circulating TT4 concentrations had decreased (P <0.0001) at week 4 and did not change significantly from week 4 to week 8. Circulating TT4 concentration was within the reference range in 56/88 cats at week 4 and in 51/68 cats at week 8. Clinical parameters (vomiting, polyuria, polydipsia, hyperactivity, polyphagia, weight loss, hair coat quality, and quality of life) had improved (P <0.0001) by week 4. Circulating creatinine concentration decreased (P = 0.001) from week 0 to week 4. Side effects associated with feeding the iodine-restricted food were not observed. In conclusion, in client-owned cats with hyperthyroidism an iodine-restricted food is a valuable management option to normalise circulating TT4 concentrations, and improve clinical signs of hyperthyroidism within 4 weeks. This applies to newly diagnosed cats, as well as to previously diagnosed cats receiving anti-thyroid drugs.

Effects of a branched-chain amino acid-enriched diet on chronic hepatic encephalopathy in dogs

A decreased ratio of branched-chain amino acids (BCAA) to aromatic amino acids (AAA) is considered an important pathogenetic factor in hepatic encephalopathy (HE). A relationship between the deranged BCAA/AAA ratio and dopaminergic dysfunction through the formation of “false” neurotransmitters has been postulated. The intermediate lobe of the pituitary is more pronounced in dogs than in humans and because it is primarily under dopaminergic inhibitory influence, it may serve as an indicator of alterations in dopaminergic neurotransmission. We investigated the effects of a diet with a high BCAA/AAA ratio (HR) and an isonitrogenous diet with a low BCAA/AAA ratio (LR) on several physical and biochemical parameters including pituitary function in dogs with portocaval shunts and 40% hepatectomy and in sham-operated pair-fed controls, in a double-blind, randomized cross-over study. Portocaval-shunted dogs had hyperammonemia (33±3 μM (mean ± SEM) before and 214±21 after surgery)) and signs of HE. Their BCAA/AAA ratio in plasma and CSF decreased from 4.3±0.3 and 2.3±0.3 before surgery to 1.3±0.1 and 0.5±0.1 after surgery, respectively. These parameters remained unaltered in the control dogs. The consumption of the LR diet was significantly higher than consumption of the HR diet. In the portocaval-shunted dogs, plasma ammonia concentration was higher on the HR diet than on the LR diet (344±52 v 246±45) and the HE grade was worse. The BCAA /AAA ratio remained abnormal in HE dogs during the feeding of both diets. The basal and haloperidol-stimulated release of α-melanotropin and cortisol in plasma were not significantly different between or within groups during any period. In contrast, urinary cortisol excretion was increased in the HE dogs after surgery (urinary cortisol:creatinine ratio (×10−6) 8.5±1.4 before and 30.4±8.9 after surgery). The basal plasma concentration of adrenocorticotropin in HE dogs was decreased after surgery (68.3±10.2 ng/L before and 40.8±4.4 after surgery). This indicates a non-pituitary-dependent hyperresponsiveness of the adrenals. We conclude from these results that chronic HE in dogs is not associated with an abnormal dopaminergic neurotransmission at least at the level of the pituitary, and that it is not the content of the dietary neutral amino acids but rather the total protein intake that may have a beneficial effect on HE.

Renal dysplasia in three young adult dutch kooiker dogs

Chronic renal failure as consequence of renal dysplasia was diagnosed in three young adult Dutch kooiker dogs (Dutch decoy dogs). Two animals were anorectic from an early age and were thinner than healthy dogs of the same breed. All three were presented because of apathy and weakness. Laboratory examination revealed anaemia and uraemia. One dog was presented with severe dehydration and died during emergency treatment. One dog was euthanatised because of a poor prognosis, and one was given a low-protein diet. This dog survived for 7 months after the diagnosis of chronic renal failure. At necropsy all three animals had shrunken, pale, and firm kidneys that showed microscopical lesions characteristic of canine renal dysplasia, such as asynchronous differentiation of nephrons, persistent immature mesenchyme, persistent metanephric ducts, and adenomatoid proliferation of the tubular epithelium. Secondary degenerative and inflammatory changes consisted of interstitial fibrosis and predominantly lymphocytic/plasmacytic inflammation. This is the first report of renal dysplasia in the Dutch kooiker dog. The disease should be included in the differential diagnosis in young Dutch kooiker dogs with signs of chronic renal failure. The presentation of three cases of this rare disease in this breed, which is based on a rather small gene pool, suggests that it is a familial or hereditary nephropathy.

Seven cases of heartworm disease (dirofilariosis) in dogs in the Netherlands

We present here the clinical history, diagnosis, and treatment of seven dogs with dirofilariosis. All dogs were imported into the Netherlands after residing in an area in which dirofilariosis is endemic. In three of these dogs the infection was occult, for the serological test was positive but there was no microfilaraemia. Weight loss, coughing, dyspnoea, and decreased exercise tolerance were the most prominent clinical signs. Two of the dogs had the characteristic electrocardiographic and radiographic signs of enlargement of the right heart. Treatment with thiacetarsamide and ivermectin resulted in complete remission in six dogs. One dog died, presumably as a result of acute renal failure. In the past year (1992-1993) seven cases of canine dirofilariosis were diagnosed, nearly equal to the number in the preceding 10 years (n = 9). This most probably reflects the greater sensitivity of the serological diagnosis of dirofilariosis in comparison with identification of microfilariae in the circulation, but a real increase in the number of dogs with dirofilariosis as a result of growing international traffic of tourists accompanied by pets cannot be excluded.

Polycythaemia vera in a dog treated by repeated phlebotomies

Polycythaemia vera (PV) was diagnosed in a dog by demonstration of an increased red cell mass in association with normal arterial oxygen saturation and the absence of conditions known to be associated with secondary polycythaemia. The dog was treated exclusively by repeated phlebotomies and replacement of the removed volume by colloid and crystalloid solutions. It survived for one year and was generally free of signs.

Effectiveness of a new dietetic weight management food to achieve weight loss in client-owned obese cats.

Objectives The aim of the study was to evaluate weight loss and maintenance parameters in cats fed a novel weight management food and to assess the owner’s perception of the cat’s quality of life. Methods This study was designed as a prospective, uncontrolled/unmasked clinical trial. One hundred and thirty-two overweight/obese, otherwise healthy, client-owned cats were enrolled. Initial evaluation included physical examination, nutritional assessment, ideal body weight determination and weight-loss feeding guidelines development. Follow-up evaluations (monthly for 6 months) encompassed determination of body weight, body condition score, body fat index, muscle condition score and feeding practices. Quality of life assessment by owners included the cat’s level of energy, happiness, appetite, begging behavior, flatulence, stool volume and fecal score. Results Eighty-three percent of the cats lost weight, with an average ± SEM weight loss of 11.0 ± 1.8% over 6 months and an average ± SE weekly weight loss rate of 0.45 ± 0.02%. The mean ± SEM duration of weight loss was 134.0 ± 4.8 days. Fourteen percent of cats achieved an ideal body weight. Seventy-nine percent of cats ate more calories from novel weight management food than the recommended daily energy requirement for weight loss, and the majority of these cats still lost weight. Body condition score and body fat index decreased over time compared with baseline from weeks 12–24 and from weeks 8–24, respectively. Owners perceived an increase in energy and happiness (>week 12) in the cats that lost weight, without changes in appetite or begging behavior. Conclusions and relevance This study confirmed the effectiveness of the novel weight management food in achieving weight loss in overweight/obese client-owned cats. Owners reported significant improvements in their cat’s quality of life without negative side effects.