ICD-10-CM > N00-N99 > N20-N23 > N21 N21 Calculus of lower urinary tract Non-Billable/Non-Specific Includes calculus of lower urinary tract with cystitis and urethritis Codes N21.0Calculus in bladderN21.1Calculus in urethraN21.8Other lower urinary tract calculusN21.9Calculus of lower urinary tract, unspecified