Clinical and histopathological features of urine scalding in dogs and cats

Urine irritant contact dermatitis is a clinically well-recognized but poorly documented condition in small animals. This study aims to systematically summarize the clinical and histopathological features of canine and feline urine scalding. Twelve cases, 10 dogs and 2 cats, were identified and included in a retrospective study of medical records and histology samples. All animals had histories of urinary incontinence with urinary problems (ectopic ureters, urolithiasis, urinary tract infection, sphincter mechanism incompetence, etc.) or a genital conformational issue with concurrent urine scalding. Gross lesions varied and included white papules/plaques, discrete nodules, and overt ulcers that localized to perigenital areas and/or involve the abdomen, inguinal areas, and proximal legs. The hallmark histopathological changes were locally extensive epithelial hyperplasia with marked spongiosis (intracellular edema) of the granular and spinous layers, diffuse parakeratosis, and variable degrees of erosion to ulceration with secondary bacterial infection and necrosis. This report summarizes the clinical and histopathological findings in urine scalding and highlights the importance of the clinical history, presentation, and lesion distribution to achieve the correct diagnosis. In the absence of a history or awareness by the pathologist of this unique histopathological pattern, urine scalding could easily be misdiagnosed.