We report a case of a large inguino-scrotal bladder hernia presenting with obstructive lower urinary symptoms and causing massive unilateral uretero-hydronephrosis with ipsilateral renal function deterioration. Careful anamnesis and computer tomography (CT) scan of the abdomen and pelvis were important for the diagnosis. Open surgery with mesh hernia repair was successful. The obstructive lower tract symptoms subsided following surgery while the deteriorated renal unit regained only part of its function.