Canine diabetes mellitus: can old dogs teach us new tricks?

BACKGROUND: Diabetes is common in dogs, with an estimated prevalence of 0.32% in the UK. Clinical signs, as in man, include polydipsia, polyuria and weight loss, associated with hyperglycaemia and glucosuria. Diabetes typically occurs in dogs between 5 and 12 years of age, and is uncommon under 3 years of age. Breeds predisposed to diabetes include the Samoyed, Tibetan Terrier and Cairn Terrier, while others such as the Boxer and German Shepherd Dog seem less susceptible. These breed differences suggest a genetic component, and at least one dog leucocyte antigen haplotype (DLA DRB1*009, DQA1*001, DQB1*008) appears to be associated with susceptibility to diabetes. METHODS: Canine diabetes can be classified into insulin deficiency diabetes (IDD), resulting from a congenital deficiency or acquired loss of pancreatic beta cells, or insulin resistance diabetes resulting mainly from hormonal antagonism of insulin function. RESULTS: There is no evidence for a canine equivalent of human type 2 diabetes. Adult-onset IDD, requiring insulin therapy, is the most common form, with pancreatitis and/or immune-mediated beta cell destruction considered to be the major underlying causes of the disease. DISCUSSION: Autoantibodies to insulin, recombinant canine GAD65 and/or canine islet antigen-2 have been identified in a proportion of newly diagnosed diabetic dogs, suggesting that autoimmunity is involved in the pathogenesis of disease in some patients. CONCLUSION: The late onset and slow progression of beta cell dysfunction in canine diabetes resembles latent autoimmune diabetes of the adult in man.

Evaluation of a continuous glucose monitoring system in diabetic dogs.

The generation of a blood glucose curve is important for assessing the response to insulin therapy in diabetic dogs. Disadvantages of this technique include patient discomfort and the potential for missing transient hypo- or hyperglycaemic episodes. The aim of the current study was to evaluate a continuous glucose monitoring system (CGMS) for use in diabetic dogs. Interstitial fluid glucose concentrations were recorded in 10 diabetic dogs, every five minutes for up to 48 hours, using a subcutaneous sensor attached to the CGMS device. Blood glucose concentrations were measured simultaneously using a glucometer. The correlation between interstitial fluid and blood glucose values was 0.81 (P < 0.01). The largest discrepancies between the two sets of data were seen during the one- to three-hour period following feeding, suggesting that postprandial hyperglycaemia might not be reflected in the interstitial fluid. The authors conclude that the CGMS is a potentially valuable tool in the management of canine diabetic patients.

Evaluation of two point-of-care analysers for measurement of fructosamine or haemoglobin A1c in dogs.

Measurement of glycosylated proteins such as fructosamine and haemoglobin A1c (HbA1c) can be used to assess glycaemic control in canine diabetic patients. Two point-of-care analysers, designed for human diabetics, were evaluated for use in dogs. Blood samples were collected from 50 normoglycaemic dogs, 100 diabetic patients and five dogs with insulinoma and tested using the In Charge fructosamine meter and the Haemaquant/Glycosal HbA1c meter. Readings were obtained in all cases except for 21 of 50 diabetics, which were above the upper limit of the In Charge meter. Diabetic dogs had higher fructosamine and HbA1c concentrations compared to controls. However, there was poor agreement between the In Charge meter readings and serum fructosamine concentrations, suggesting that there are problems associated with the use of this device in dogs. HbA1c concentrations showed a high degree of correlation with glycosylated haemoglobin measured at an external laboratory, suggesting that the Haemaquant/Glycosal meter warrants further evaluation for veterinary use.

The use of 17-hydroxyprogesterone in the diagnosis of canine hyperadrenocorticism.

A number of dogs are seen with clinical signs consistent with hyperadrenocorticism (HAC), supporting CBC and biochemical findings, but the disease cannot be confirmed with either the ACTH stimulation test or the low-dose dexamethasone suppression test (LDDST). Therefore, another screening test is required to aid diagnosis in these atypical cases of HAC. The aim of this study was to investigate whether measuring 17-hydroxyprogesterone (OHP) concentrations could be used in this role. Plasma cortisol and OHP concentrations were measured in dogs with clinical signs suggestive of HAC before and after administration of exogenous ACTH. In dogs with HAC, plasma OHP showed an exaggerated response to ACTH stimulation. This was seen in both typical cases of HAC with a positive cortisol response to ACTH administration and in atypical cases with negative screening test results. The test can be performed on plasma already taken for a conventional ACTH stimulation test. Post-ACTH OHP concentrations decreased after treatment with mitotane or adrenalectomy. These results suggest that OHP measurements can be used as an aid to diagnose and manage canine HAC.

Two cases of severe iron-deficiency anaemia due to inflammatory bowel disease in the dog.

Two dogs were referred for investigation of lethargy and anaemia. Preliminary examinations by the referring veterinary surgeons had revealed severe anaemia, which was poorly regenerative. In one case, the anaemia was microcytic and, in the other, it was hypochromic. These findings were suggestive of chronic blood loss anaemia. Neither dog had external signs of gastrointestinal disease, although one had vomited on a single occasion during the two weeks preceding referral. Although both dogs were producing grossly normal faeces, further investigations detected faecal occult blood. Multiple full thickness gastrointestinal biopsies were taken at laparotomy. These showed segmental eosinophilic enteritis of the duodenum and proximal jejunum in one case, and marked chronic lymphocytic gastritis in the other. Both cases illustrate the fact that severe systemic disease can result from gastrointestinal pathology in the absence of clinical signs of gastrointestinal disease.

Congenital Pulmonic Stenosis a Retrospective study of 24 cases seen between 1990-1999.

BACKGROUND: PBV is the treatment of choice for humans with pulmonic stenosis and whilst this procedure has been used in dogs the longer term benefits remain to be evaluated. OBJECTIVES: The purpose of this study was to evaluate the long term effects of pulmonary balloon valvuloplasty (PBV) in dogs with congenital pulmonic stenosis, with respect to clinical signs, echocardiographic parameters and survival time. Methods - Pulmonic stenosis was diagnosed in 24 dogs between 1990-1999. Eighteen cases were treated with PBV, six were not treated. RESULTS: Twelve of the treated cases were alive and asymptomatic at the time of writing. Follow up periods ranged from six months to nine years post PBV. Prior to treatment the mean Doppler pressure gradient across the pulmonic valve was 98mmHg, 24 hours post treatment the mean was 65mmHg and in the long term this was maintained at 64mmHg. Three of the dogs (17 per cent) treated with PBV restenosed during the follow up period. Four of the six untreated dogs were alive at the time of writing, two to four and a half years after presentation. The mean Doppler gradient for this group was 89 mm Hg on presentation. CONCLUSION: At this stage in the follow up period there is no significant difference in survival times between the treated and untreated groups. However, symptomatic dogs with pulmonic stenosis treated with PBV have experienced a reduction in clinical signs and therefore an improved quality of life.