Causes of feline inappropriate urination can be medical (eg, feline lower urinary tract disease, feline idiopathic cystitis, urinary calculi), hormonal (eg, intact status, exogenous hormonal therapy, adrenal tumor), or related to litter box aversion or urine marking.1
Because penile spines, which are testosterone-dependent, were noted on physical examination, this case of inappropriate urination was most likely due to hormonal causes. Differential diagnoses for penile spines in a presumably neutered male cat are retained testicle(s), exogenous testosterone exposure, or a sex hormone-producing adrenal tumor.
Access to topical hormonal creams in the household was ruled out, and, because Bandit was an indoor-only cat, exogenous testosterone exposure was unlikely. Adrenal tumors are rarely reported in cats.2 Retained testicular tissue can be diagnosed via imaging, hormone testing, or exploratory laparotomy (see Diagnosing Retained Testicular Tissue).
The owner wanted to ensure testicular tissue was present before surgery was performed, so an anti-Müllerian hormone (AMH) test was submitted to the laboratory, and results confirmed the presence of testicular tissue.