Almost always seen as part of medical compounds: 泌尿科 (urology department), 泌尿系统 (urinary system), 泌尿外科 (urological surgery). On its own as a verb it is clinical and rare in everyday speech - 小便 is the common word.
mistakes
泌 has two readings: mì (to secrete, as in 分泌 'to secrete') but bì in the place name 泌阳 (in Henan). In 泌尿 it is always mì.
