A 10-year-old male mixed-breed dog was admitted for recurrent signs of urinary tract infection (UTI). Urinary bladder ultrasonography revealed decreased thickness of its wall with floating hyperopic particles within its lumen. Ultrasonography revealed a structure invading the dorsal wall of the penile urethral lumen, located in a segment distal to the bladder. Radiographies showed bone resorption with proliferation at the caudal aspect of the penile bone, stricture of the final aspect of the penile urethra, and no radiopaque images compatible with a urethrolith. Computed tomography showed bone proliferation causing stricture of the urethral lumen at two different sites. Presumptive diagnosis of penile neoplasia was considered more likely and the dog underwent penectomy along with orchiectomy and scrotal urethrostomy. Enterobacter spp. was cultured from the urine sample and antibiotic sensitivity tests revealed that the bacterium was susceptible to amikacin, imipenem, and meropenem. Histopathology revealed severe suppurative urethritis, bone resorption, and hyperostosis, suggestive of osteomyelitis of the penile bone. Neoplastic cells were not observed at any part of the examined tissue. The findings in the present case suggest that osteomyelitis of the penile bone should be included in differential diagnosis for partial and complete urethral obstruction in dogs with recurrent UTI.
