ICD-10 Code for Kidney Stones
The ICD-10 code for kidney stones (renal calculus) is N20.0 for calculus of kidney, with additional codes available based on anatomic location: N20.1 for calculus of ureter, N20.2 for calculus of kidney with calculus of ureter, and N20.9 for urinary calculus, unspecified.
Code Structure and Clinical Application
The ICD-10 coding system provides specific codes for urolithiasis based on stone location 1:
- N20.0: Calculus of kidney (renal pelvis, upper/middle/lower calyx)
- N20.1: Calculus of ureter (upper, middle, or distal)
- N20.2: Calculus of kidney with calculus of ureter
- N20.9: Urinary calculus, unspecified location
Coding Accuracy Considerations
When using these codes, be aware that ICD-9 validation studies showed a positive predictive value of 95.9% for upper tract calculi overall, though distinguishing between renal (85% PPV) and ureteral stones (100% PPV) was less reliable 2. Specifically, 76% of patients with ureteral stones were not appropriately coded with the ureteral-specific code 2.
Key Coding Pitfalls
- Location specificity matters: While N20.1 (ureteral calculus) has high accuracy when used, most ureteral stones are miscoded as general renal calculi
- Use the most specific code available: Based on imaging findings (ultrasound, CT, or KUB radiography), code to the exact anatomic location 1
- Document stone characteristics: Size (<5mm, 5-10mm, 10-20mm, >20mm), laterality, and whether obstruction is present should be documented separately to support medical necessity and risk stratification 1
Clinical Context for Proper Coding
The 2025 European Association of Urology guidelines emphasize that stones should be classified by anatomic position (upper/middle/lower calyx, renal pelvis, or ureter location) 1. This anatomic classification directly corresponds to the ICD-10 code structure and impacts treatment algorithms.
For billing and epidemiological purposes, these codes have sufficient validity for identifying stone disease patients in administrative databases, though they should not be relied upon as the sole method to distinguish renal from ureteral location in research studies 2.