The clinical and pathological findings in 45 shih tzu dogs with progressive nephropathy due to renal dysplasia are described. There was no sex dependence and the age at death/euthanasia varied from seven weeks to nine years, with a mean age of two years. The most common clinical signs were depression, polydipsia and vomiting. All dogs showed elevated blood urea levels and most passed dilute urine. Proteinuria and anaemia were the most common findings. At necropsy all dogs had small, lobulated, pale kidneys with capsular adhesion. Multiple cysts in the cortex and in the intermediary zone were found in most cases. The morphological changes were three different types based on microscopic examination: 1 Primary dysplastic lesions; where fetal glomeruli were the most consistent finding.2 Compensatory changes; where hypertrophy and hyperplasia of the glomerular tufts and tubules were most frequently observed.3 Inflammatory lesions and fibrosis were found in all cases.A genetic study of 37 dogs suggests a simple recessive mode of inheritance. Based on this information a control scheme against renal dysplasia has been instigated.

Puppies from two litters of dogs were found to have severe polyuria and polydipsia. Four of the dogs were investigated by means of clinical examination, haematological and biochemical analysis, and urinalysis. A modified water deprivation response test was also performed in two of the dogs. Renal changes on postmortem examination in three of the dogs were found to be consistent with renal dysplasia. A possible explanation for the finding of hyposthenuria and the extreme polyuria and polydipsia in association with renal dysplasia may be lack of response to antidiuretic hormone owing to anomalous maturation of the renal tubules. Six other puppies from the two litters of dogs did not show any clinical signs of polyuria and polydipsia, although postmortem examination in one of them also revealed renal dysplasia. The clinical features of renal dysplasia may therefore vary greatly between individuals.

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Glomerular filtration rate (GFR) normalized to body fluid volumes to adjust for differing body size and conformation is more physiologically correct than a relationship with body weight (BW). GFR can be normalized to plasma volume by a renographic method that uses the Rutland-Patlak plot with plasma activity and kidney activity inputs. A plasma time-activity curve is obtained from a region of interest (ROI) of the left ventricle (LV), the size of which is in theory not critical. The aims of the study were to evaluate the effect of different LV ROI sizes, the effect of extravascular activity in the thorax over the LV ROI, and different time intervals for the semilogarithmic LV plot. Seventy-two scintigrams were used, with three different-sized automatic and a manual LV ROI, all with and without subtracting extravascular activity, and with LV curve time intervals of 30-120 s and 60-240 s. GFR/plasma volume was not affected by LV ROI sizes but significantly affected by extravascular activity subtraction and different time intervals. Subtracting extravascular activity from the LV ROI did not improve precision, but increased variability caused by different LV ROI sizes and time intervals chosen for the LV plot. The ROI for measuring extravascular activity apparently contained a considerable and variable intravascular component, which when subtracted, created noisy and unreliable LV curves. Manual LV ROI, without extravascular subtraction, and a time interval for LV input between 1 and 4 min are recommended as they gave the least variability determined by statistical analysis. With these methods, normal individual GFR/plasma volume in normal beagle dogs was 29.2 +/- 6.5 ml/min/l.

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