The primary ICD-10-CM code for nephrolithiasis (kidney stones) is N20.0 (Calculus of kidney), a billable code reported when a calculus is documented within the kidney itself, excluding stones located in the ureter or bladder.
Primary codes
Billable
Billable
Extension
—
7th character
—
POA exempt
No
Inclusion terms
- Nephrolithiasis NOS
- Renal calculus
- Renal stone
- Staghorn calculus
- Stone in kidney
Coding risks
- Missing a required companion or status code
Hierarchy
Code comparison
Compare key differences between related codes to select the most specific option.
| Code | Description | Scenario |
|---|---|---|
| N20.0 | Calculus of kidney | Patient with stone documented in the kidney only, no ureteral involvement noted. |
| N20.1 | Calculus of ureter | Patient with calculus documented in the ureter only, no kidney stone present. |
| N20.2 | Calculus of kidney with calculus of ureter | Patient with documented stones in both the kidney and the ureter concurrently. |
| N20.9 | Urinary calculus, unspecified | Urinary calculus documented without specifying kidney, ureter, or both as the location. |
Select the most specific code supported by the encounter documentation. More specific codes improve reimbursement accuracy and reduce audit risk.
Code ranges
Calculus of kidney and ureter
Category for stones located in the kidney, ureter, or both, classified by anatomic site rather than composition or size.
Urolithiasis
Sub-chapter covering calculi throughout the urinary tract, including kidney, ureter, bladder, lower tract, and unspecified renal colic.
Calculus of lower urinary tract
Category for calculi located in the bladder or urethra, distinct from upper tract stones in the kidney or ureter.
Obstructive and reflux uropathy
Category covering hydronephrosis and urinary tract obstruction from various causes, including obstruction produced by calculi.
Abdominal and pelvic pain
Category for symptomatic abdominal or flank pain without a confirmed underlying diagnosis documented by the provider.
Coding risks
Avoid these common coding issues when reporting Nephrolithiasis.
Impact
Assigning N20.0 without explicit location may miscode ureteral or combined calculi as isolated kidney stones.
Mitigation
Consider querying the provider when location is absent rather than inferring from imaging findings alone.
Related codes
Ancillary and co-coding
Codes commonly reported with the primary diagnosis on the same claim.
Z-code variants
Family history, personal history, or screening encounter codes related to this condition.
In pregnancy
Pregnancy-specific O-code adaptations used in place of the primary when the condition occurs during or complicates pregnancy.
Differential codes
Alternative or commonly confused codes to consider when documentation suggests a different condition than the primary diagnosis.
Frequently asked questions
Use N20.9 only when documentation does not specify the calculus location. If the kidney or ureter is identified, code to N20.0 or N20.1 instead.
References
Compiled from the following authoritative coding references. Last updated 2026-08-04.