N20.1

Here is a detailed reference note for N20.1, formatted for your guide.

N20.1: Calculus of ureter

Description

Definition: Presence of a calculus (stone) located in the ureter (the tube connecting the kidney to the bladder).
Common Terms: Ureteric stone, ureteral lithiasis, stone in the ureteropelvic junction (UPJ) if obstructing the ureter.
Code Structure: This code does not specify laterality (Right vs. Left). You report N20.1 regardless of which side is affected. You must use CPT modifiers (RT/LT) to indicate the side for the procedure.

Body system / area

Chapter: Diseases of the genitourinary system (N00-N99).[2]
Block: urolithiasis (N20-N23).[2]
Anatomic focus: ureter (upper urinary tract).[1]

Tabular context, Includes / Excludes

From the N20 “Calculus of kidney and ureter” block:

N20 - Calculus of kidney and ureter
- N20.0 Calculus of kidney (nephrolithiasis, renal calculus, staghorn calculus).
- N20.1 Calculus of ureter (calculus of the ureteropelvic junction, ureteric stone).
- N20.2 Calculus of kidney with calculus of ureter.
- N20.9 Urinary calculus, unspecified.

Specific Includes/Excludes around this block:

N22 Calculus of urinary tract in diseases classified elsewhere - “Code first underlying disease, such as gout, schistosomiasis.”[2]
Excludes1 at N21.9: “calculus of urinary tract NOS N20.9” (so if only “urinary calculus” is stated, N20.9, not N21.9).[2]
N20-N23 block notes: “urolithiasis,” separate from other kidney/ureter disorders N25-N29.[2]

There are no code‑specific Excludes1/2 notes listed directly under N20.1 itself in the 2026 tabular; the block‑level conventions above apply.

Risk Adjustment (HCC) Status

HCC Weight: No.
Clinical Note: Urinary stones generally do not map to a Hierarchical Condition Category (HCC) for risk adjustment. They are typically treated as acute episodic conditions unless they lead to chronic kidney failure.

Critical Coding Rule: The “Hydronephrosis” Override

The Rule: Do not report N20.1 if the stone is causing obstruction or swelling (hydronephrosis/hydroureter).
The Correction: If the documentation states “Ureteral stone with hydronephrosis” or “Obstructing stone,” you must code N13.2 (Hydronephrosis with renal and ureteral calculous obstruction) instead.
Why: N13.2 is a combination code that captures both the stone and the resulting complication. Reporting N20.1 (stone alone) with N13.30 (unspecified hydronephrosis) is incorrect because it violates ICD-10 “Excludes” notes and unbundles the condition.

Common Associated CPT Codes

1. ureteroscopy (URS) - Most Common

52356: Cystourethroscopy, with ureteroscopy and/or pyeloscopy; with lithotripsy (e.g., laser) including insertion of indwelling ureteral stent.
- Note: This is the “gold standard” code when a stent is placed. Do not bill 52332 separately.
52353: Cystourethroscopy, with ureteroscopy… with lithotripsy.
- Use: If laser is used but no stent is left indwelling.
52352: Cystourethroscopy, with ureteroscopy… with removal or manipulation of calculus.
- Use: If the stone is “basketed” and removed intact without fragmenting it first.
52351: cystourethroscopy, with ureteroscopy… diagnostic.
- Use: If the surgeon looks but cannot reach/treat the stone, or if the stone has already passed.

2. Shock Wave Lithotripsy (ESWL)

50590: Lithotripsy, extracorporeal shock wave.
- Use: Non-invasive fragmentation of the stone.

Compliance & Billing Tips

Stent Bundling:
- If billing 52356 (lithotripsy + Stent), the stent is built into the code. Do not unbundle 52332.
- If billing 52352 or 52353 (older codes), you might be able to bill 52332 (stent insertion) separately with Modifier 59/X{EPSU}, but payer policies vary significantly. Medicare NCCI edits usually bundle the stent insertion into the treatment of the stone in the same ureter.
“Separate Procedure” Warning:
- 52310 (cystoscopy with removal of stone from bladder/urethra) is a “separate procedure.” If you perform ureteroscopy (5235x) to get a stone in the ureter, you generally cannot bill 52310 for removing fragments from the bladder, as it is considered part of the completion of the main surgery.
Unit of Service:
- The unit of service is one per ureter, not per stone. If a patient has three stones in the right ureter and you treat all three, you bill the CPT code only once with 1 unit.

Documentation Checklist

Obstruction Status: Does the note say “hydronephrosis,” “hydroureter,” or “obstruction”? If yes, code N13.2. If no, code N20.1.
Technique: Did they basket the stone (52352) or laser/fragment it (52353/52356)?
Stent: Was a stent left in place at the end of the case? (Supports 52356).

Commonly associated CPT codes

Typical services when N20.1 is the primary diagnosis include (actual selection must follow op note and payer rules):

Scenario	Example CPT code(s)*	Notes
Non‑contrast CT abdomen/pelvis for stone	74176-74178	CT without/with contrast variants, payer‑specific. [3]
Limited renal/urinary ultrasound	76775	Often for hydronephrosis/stone evaluation. [3]
Cystoscopy, ureteral catheterization	52005	Diagnostic. [3]
Cystoscopy with ureteroscopy and stone removal	52352-52356	Range depending on with/without lithotripsy, stent, etc. [3]
ESWL (extracorporeal shock wave lithotripsy)	50590	Kidney/ureter stone lithotripsy. [3]

*Always confirm current year CPT, NCCI edits, and payer policy.

24 - Unrelated E/M by same physician during postop period.[3]
25 - Significant, separately identifiable E/M on same day as procedure.[3]
50 - Bilateral procedure (uncommon for unilateral ureteral stone procedures; use only if documentation supports).[3]
51 - Multiple procedures (e.g., stone removal plus stent).[3]
52 - Reduced services (partial procedure).[3]
59 / X{EPSU} - Distinct procedural service where allowed.[3]
LT / RT - Side‑specific ureter/kidney procedures.[3]
76 / 77 - Repeat procedure by same/different physician.[3]

Example coding scenarios

ED visit, ureteral stone confirmed on CT

ICD‑10‑CM: N20.1 Calculus of ureter.[1]
Possible additional diagnoses:
- R10.9 Abdominal pain, unspecified site (if separately documented and significant).[1]
- R31.9 hematuria, unspecified, if documented.[1]
CPT: 9928X or 9928X‑25 for ED E/M, CT abdomen/pelvis 74176.[3]

ureteroscopy with stone extraction and stent

ICD‑10‑CM: N20.1 as primary.[1]
CPT: cystoscopy with ureteroscopy and stone removal (e.g., 52352 or 52356) plus modifier RT or LT as appropriate.[3]

Kidney and ureter stones

If documentation shows both renal and ureteral calculi, use N20.2 “Calculus of kidney with calculus of ureter” instead of N20.0 + N20.1.[1]

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N20.1

N20.1: Calculus of ureter

Description

Body system / area

Tabular context, Includes / Excludes

Risk Adjustment (HCC) Status

Critical Coding Rule: The “Hydronephrosis” Override

Common Associated CPT Codes

Compliance & Billing Tips

Documentation Checklist

Commonly associated CPT codes

Example coding scenarios

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Table of Contents

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Explorer

N20.1

N20.1: Calculus of ureter

Description

Body system / area

Tabular context, Includes / Excludes

Risk Adjustment (HCC) Status

Critical Coding Rule: The “Hydronephrosis” Override

Common Associated CPT Codes

Compliance & Billing Tips

Documentation Checklist

Commonly associated CPT codes

Common modifiers (for use with related CPT)

Example coding scenarios

Graph View

Table of Contents

Recent Notes