N20 vs N27

N20 (Calculus of kidney and ureter) compared with N27 (Small kidney of unknown cause), from the official CMS tabular data. Both may be reported when both conditions are documented (Excludes2).

Can these codes be reported together?

Yes, when both are documented. N27 carries an Excludes2 note covering N20: “disorders of kidney and ureter with urolithiasis (N20-N23)”

Excludes2 marks distinct conditions — both may be reported when both are documented.

Side by side

	N20Calculus of kidney and ureter	N27Small kidney of unknown cause
Billing status	Non-billable header Report instead: N20.0, N20.1, N20.2, N20.9	Non-billable header Report instead: N27.0, N27.1, N27.9
Classification	N00-N99 — Diseases of the Genitourinary System (N00-N99)	N00-N99 — Diseases of the Genitourinary System (N00-N99)
Definition	Calculus of kidney and ureter is a non-billable ICD-10-CM category code (N20).	Small kidney of unknown cause is a non-billable ICD-10-CM category code (N27).
Includes	Calculous pyelonephritis	oligonephronia

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Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources