The causes of LUTD found in cats in this study are similar to those that have been previously documented, and idiopathic LUTD is the most frequent diagnosis. However, the rate of urethral obstruction, particularly in cats with idiopathic LUTD, was higher than in other reports. The cause of this difference is unknown.

BackgroundSome dogs with primary hypoadrenocorticism (HA) have normal sodium and potassium concentrations, a phenomenon called atypical Addison's disease. The assumption that the zona glomerulosa and aldosterone secretion in these dogs are normal seems widely accepted; however, aldosterone measurements are missing in most published cases.ObjectivesTo measure aldosterone in dogs with HA with and without electrolyte abnormalities and to determine the time point of aldosterone peak concentrations during ACTH stimulation.AnimalsSeventy dogs with HA, 22 dogs with diseases mimicking HA, and 19 healthy dogs.MethodsProspective study. Blood samples were taken before and 60 minutes after injection of 250 μg ACTH in all dogs. Additional blood samples were taken 15, 30, and 45 minutes after ACTH in 7 dogs with HA and in 22 with diseases mimicking HA.ResultsBaseline and ACTH‐stimulated aldosterone was significantly lower in dogs with HA than in the other groups. Aldosterone was low or undetectable in 67/70 dogs with HA independently of sodium and potassium levels. In 3 dogs, sodium/potassium concentrations were normal; in 1 dog, sodium was normal and potassium decreased. In all 4, ACTH‐stimulated aldosterone concentrations were below the detection limit of the assay. Aldosterone concentrations were not different at 30, 45, or 60 minutes after ACTH administration.Conclusion and Clinical ImportanceCortisol and aldosterone secretion is compromised in dogs with HA with and without electrolyte abnormalities. The term atypical Addison's disease, used for dogs with primary HA and normal electrolytes, must be reconsidered; other mechanisms allowing normal electrolyte balance without aldosterone should be evaluated in these dogs.

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The adrenal glands of 30 dogs with primary adrenal insufficiency (hypoadrenocorticism) were measured ultrasonographically and compared with those of 14 healthy dogs and those of 10 dogs with diseases mimicking hypoadrenocorticism. Thickness and length of the adrenals were measured on abdominal ultrasonography and the results for each group were compared. Dogs with primary hypoadrenocorticism had significantly thinner adrenals compared with the other two groups, and their left adrenal glands were also significantly shorter than those of healthy dogs. Adrenal ultrasonography may be of diagnostic value in dogs with clinical signs suggestive of primary hypoadrenocorticism, as a left adrenal gland measuring less than 3.2 mm in thickness is strongly suggestive of the disease.

Treatment with trilostane resulted in a reduction in serum cortisol and aldosterone concentrations in dogs with PDH, although the decrease for serum aldosterone concentration was smaller than that for serum cortisol concentration. There was no correlation between serum concentrations of aldosterone and potassium during treatment.