March 2003 JOURNAL ROUNDUP

Two papers in March described findings in that commonly presented patient, the obese cat. Hoenig et al¹ compared the lipid profiles of obese and lean cats. The obese cats demonstrated insulin resistance as assessed by intravenous glucose tolerance tests. Plasma triglyceride and cholesterol concentrations were significantly increased in obese cats, as were very low density lipoprotein (VLDL) concentrations. The authors postulate that the increase in VLDL may contribute to insulin resistance. Szabo et al² examined the effects of dietary protein quality and dietary lipids on fatty acid composition in liver and adipose tissue after weight loss in overweight cats. The results showed that following weight loss, the fatty acid composition of these tissues was affected by dietary protein quality. This has implication for the development of hepatic lipidosis in obese cats on weight reducing diets.

            On the subject of liver disease, Trainor et al³ evaluated the use of a urine test for bile acids as a diagnostic test for liver disease in cats. They postulated that urine bile acid reflects an average value of serum bile acid concentrations, and therefore may have more utility than pre and post prandial serum bile acid concentrations. A ratio with urine creatinine was used to allow for different concentrations of urine. High sensitivity and specificity was found with this test for liver disease in cats, and the authors conclude it should be of use for practitioners in the future.

            Amitriptyline has been recommended for the treatment of recurrent idiopathic cystitis in cats. Kruger et al⁴ postulated that because of the rapid onset of anti-inflammatory effects of amitryptyline, a 7 day treatment may be beneficial in cats with actue non-obstructive idiopathic LUTD. However, in the sample studied, there was no difference in the probability or speed of recovery of amitryptyline treated cats compared with controls, and in fact the amitryptyline group suffered a recurrence of clinical signs faster. Although the sample size was small, the authors caution against the use of amitryptiline for a short term with a sudden withdrawal, as this may precipitate further clinical signs.

            An ACE inhibitor, benazapril is licensed in the UK for treatment of chronic renal insufficiency in cats. Brown et al⁵ examined the effect of a different ACE inhibitor, enalapril, in dogs with induced chronic renal insufficiency. Compared with controls, treated dogs had a lower systemic mean arterial blood pressure and reduced urine protein:creatinine rations. Treated animals also had a lower incidence of structural renal lesions. The authors conclude that ACE inhibition may be effective for reducing the progression of renal disease in dogs.

            Corneal endothelial dysfunction is seen in older dogs and middle-aged dogs of some breeds, leading to ulcerative keratitis and bullous keratopathy. Treatment with hypertonic saline has been advocated, but results are inconsistent. Penetrating keratoplasty is the definitive treatment, but is expensive and technically difficult.   Michau et al⁶ evaluated the use of thermokeratoplasty for treatment of this condition. This procedure shortened the mean duration of topical treatment required for resolution of the ulceration. The authors note that it may be necessary to perform thermokeratoplasty over the entire surface of the cornea to prevent recurrence of ulceration.

            The treatment of choice for acute immune-mediated haemolytic anaemia is immuno-suppressive doses of prednisolone. Other immuno-suppressive drugs may be added in those cases that fail to respond to prednisolone alone. Mason et al⁷ investigated the use of cyclophosphamide with prednisone compared to prednisone alone, in a prospective randomized trial. The mortality rate was higher in dogs treated with prednisone and cyclophosphamide compared to those just receiving prednisone. It was also noted that reticulocytosis was suppressed in those dogs treated with the combination, and spherocytosis resolved more quickly in dogs treated with prednisone alone. The authors conclude that there seems to be no advantage to the addition of cyclophosphamide to the treatment regime of acute immune-mediated haemolytic anaemia in dogs.

            Serological testing for allergen-specific IgE antibodies is widely available commercially, and is used to assist in the diagnosis of atopy and to develop hyposensitisation treatments. Saevik et al⁸ evaluated the use of an ELISA for IgE antibodies in dogs and compared the results to the “gold-standard” method of intra-dermal testing. They found that for this particular ELISA, the sensitivity was only 54% and the specificity 84%. The authors question the significance of a positive ELISA test result and suggest that the test was not measuring functional allergen-specific IgE.

            Olby et al⁹ reviewed the outcome over a prolonged period of 87 dogs suffering severe thoracolumbar spinal injuries causing paraplegia and loss of deep pain perception. 58% regained deep pain perception and the ability to walk. 11% regained the ability to walk without recovering deep pain perception, but all of these were incontinent. 14% of dogs which underwent surgery for intervertebral disc herniation were euthanased within 3 weeks of surgery, most of these because of ascending myelomalacia. Traumatic injuries were associated with a poorer prognosis than intervertebral disc herniation.

            Finally, for those seeing the increasing number of dogs coming from the USA, bear in mind Leishmaniasis in your differential diagnosis list. Grosjean et al¹⁰ report that serological evidence suggests that exposure to Leishmania while uncommon, is seen in this country.

1. Hoenig et al, AJVR 2003; 64, 299

2. Szabo et al, AJVR 2003; 64, 319

3. Trainor et al, J Vet Int Med 2003; 17, 145

4. Kruger et al, JAVMA 2003; 222, 749

5. Brown et al, AJVR 2003; 64, 321

6. Michau et al, JAVMA 2003; 222, 607

7. Mason et al, J Vet Int Med 2003; 17, 206

8. Saevik et al, Res Vet Sci 2003; 74, 37

9. Olby et al, JAVMA 2003; 222, 762

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Last modified: December 08, 2003