Kidney stones are one of the most common urological complaints seen in outpatient clinics, emergency rooms, and urology practices across the United States. For physicians, urologists, and medical coders, choosing the correct ICD-10 code for kidney stones is not just a documentation formality it directly affects claim approval, reimbursement speed, and audit compliance. A single wrong digit in a kidney stone diagnosis code can lead to denied claims, delayed payments, or compliance flags during payer review.
This guide breaks down every commonly used kidney stone ICD-10 code, explains how nephrolithiasis ICD-10 classifications work, and gives doctors and billing teams a practical, easy-to-reference resource. Whether you are searching for the ICD-10 code for nephrolithiasis, trying to confirm the correct N20.0 ICD-10 code, or looking for how to document a history of kidney stones ICD-10, this article covers it all in one place.
This guide is brought to you by Revex Square, a medical billing and coding company that helps urology and primary care practices reduce claim denials and get paid faster through accurate, audit-ready documentation.
What Is Nephrolithiasis?
Nephrolithiasis, more commonly known as kidney stones, is a condition in which hard mineral and salt deposits form inside the kidneys. These stones can remain in the kidney or move into the ureter, causing severe pain, blood in the urine, nausea, and in some cases, urinary obstruction. According to the National Kidney Foundation, roughly 1 in 10 people will develop a kidney stone at some point in their lives, making accurate diagnosis and coding a routine part of urology and primary care billing. Because the clinical presentation varies so widely from a silent stone found incidentally on imaging to an emergency ureteral obstruction accurate diagnosis coding is essential for every visit type.
When a physician documents nephrolithiasis, the coding team needs to translate that diagnosis into the correct ICD-10 code for kidney stone classification. This is where confusion often starts, because there are several closely related codes depending on stone location, whether it is a first occurrence or history of the condition, and whether obstruction or infection is present.
Common Symptoms That Lead to a Kidney Stone Diagnosis
Before a physician ever assigns an ICD-10 code for kidney stones, the patient usually presents with a recognizable pattern of symptoms. Understanding these symptoms helps front-desk staff, triage nurses, and billing teams anticipate which diagnosis category a visit is likely to fall under.
- Sudden, severe flank pain that radiates toward the groin, often described as one of the worst pains a patient has ever felt
- Blood in the urine (hematuria), which may be visible or detected only through a urinalysis
- Nausea and vomiting associated with the intensity of the pain
- Frequent urination or a persistent urge to urinate, especially as a stone nears the bladder
- Fever and chills, which may indicate an infected stone requiring urgent intervention
When a patient presents with sudden flank pain, many emergency department notes will initially reference “renal colic” before imaging confirms a stone. Renal colic itself is captured separately in ICD-10-CM (under category N23, unspecified renal colic) and should only be used when imaging has not yet confirmed a calculus. Once imaging confirms a stone, the diagnosis should be updated to the specific kidney stone ICD-10 code rather than left coded as renal colic, since renal colic is a symptom code, not a definitive diagnosis code.
Risk Factors and Causes Doctors Should Document
Documentation that includes risk factors can strengthen medical necessity for imaging, lab work, and specialist referrals, all of which are billed alongside the primary nephrolithiasis ICD-10 diagnosis. Common contributing factors include:
- Chronic dehydration or low fluid intake
- Diets high in sodium, animal protein, or oxalate-rich foods
- A personal or family history of kidney stones
- Underlying metabolic conditions such as hyperparathyroidism or gout
- Certain medications and supplements that increase stone-forming mineral concentration in urine
Noting these risk factors in the chart not only supports clinical decision-making but also provides context that justifies follow-up testing, which is frequently bundled with the primary stone diagnosis code during claims review.
How Kidney Stones Are Diagnosed and Treated
Confirming a diagnosis before finalizing the ICD-10 code for kidney stone typically involves imaging and lab work. A non-contrast CT scan of the abdomen and pelvis remains the gold standard for detecting stones, though renal ultrasound is often used first in pregnant patients or when minimizing radiation exposure is a priority. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) outlines urinalysis, blood tests for kidney function, and, in recurrent cases, 24-hour urine collection as standard steps for identifying the underlying metabolic cause.
Treatment depends heavily on stone size and location. Small stones under 4-5mm often pass on their own with hydration and pain management, while larger stones may require:
- Extracorporeal shock wave lithotripsy (ESWL) to break the stone into smaller fragments
- Ureteroscopy with laser lithotripsy for stones lodged in the ureter
- Percutaneous nephrolithotomy (PCNL) for very large or staghorn calculi
- Temporary stent placement to relieve obstruction while a stone passes or awaits removal
Each of these procedures is billed with its own CPT code, but the underlying diagnosis justifying the procedure still traces back to the correct ICD-10 code for kidney stones, which is why accurate diagnosis coding at the very first visit matters for the entire treatment episode.
Understanding N20.0 and the Core ICD-10 Codes for Kidney Stones
The foundation of kidney stone coding in the ICD-10-CM system is category N20, which covers calculus of the kidney and ureter. The N20.0 ICD-10 code specifically refers to “Calculus of kidney,” and it is the code most frequently used for a standard diagnosis of nephrolithiasis without ureteral involvement. The full, current code set is maintained by CMS and the CDC’s National Center for Health Statistics, which publishes the official ICD-10-CM guidelines that every US practice should reference each fiscal year for updates.
Here is an important clarification that many doctors and coders search for: ICD-10-CM does not assign separate codes for left kidney stone or right kidney stone. Despite frequent searches for “left nephrolithiasis ICD-10” or “right renal stone ICD-10,” there is no laterality component built into the N20 category. The correct approach is to document the affected side in the clinical notes for medical necessity purposes, while still assigning N20.0 as the diagnosis code itself, regardless of whether the stone is on the left, right, or bilateral side.
Table 1: Primary ICD-10 Codes for Kidney and Ureteral Stones
| ICD-10 Code | Description | Common Search Term |
|---|---|---|
| N20.0 | Calculus of kidney (nephrolithiasis, renal stone) | icd 10 code for kidney stone |
| N20.1 | Calculus of ureter (ureterolithiasis) | ureteral stone icd 10 |
| N20.2 | Calculus of kidney with calculus of ureter | kidney stone with ureteral stone icd 10 |
| N20.9 | Urinary calculus, unspecified (urolithiasis) | urolithiasis icd 10 |
| N21.0 | Calculus in bladder | bladder stones icd 10 |
| N13.2 | Hydronephrosis with renal and ureteral calculous obstruction | kidney stone with hydronephrosis icd 10 |
This table answers many of the most frequently searched queries at once, including kidney stone ICD-10, icd 10 kidney stone, icd 10 code for kidney stones unspecified, and icd 10 ureteral stone.
Nephrolithiasis ICD-10 vs. Ureterolithiasis ICD-10: Knowing the Difference
A common point of confusion for both new coders and clinicians is the difference between nephrolithiasis and ureterolithiasis. While both terms describe urinary stone disease, they refer to different anatomical locations:
- Nephrolithiasis refers to stones located in the kidney itself, coded as N20.0.
- Ureterolithiasis refers to stones that have moved into the ureter, coded as N20.1.
- When a patient has stones in both the kidney and the ureter simultaneously, the correct code is N20.2.
If a physician documents “staghorn calculus,” which is a large, branching stone that fills the renal pelvis and calyces, this is still coded under N20.0, since staghorn calculus is a subtype of kidney stone rather than a separate diagnosis category. Searches for staghorn calculus ICD-10 should therefore be directed to N20.0 with supporting clinical documentation noting the staghorn morphology.
Documenting History of Kidney Stones: The Codes Doctors Often Miss
One of the most searched — and most frequently miscoded categories relates to a patient’s history of kidney stones ICD-10. This applies to patients who have had kidney stones in the past but do not have an active stone at the time of the current visit. Coding an active stone diagnosis for a patient who is simply being monitored after stone passage is a common billing error that can trigger payer audits.
For a resolved case, the correct code is Z87.442 Personal history of urinary (tract) calculi. This applies whether the patient had one episode or is prone to recurrent kidney stones, and it should replace, not accompany, an active N20 code once the stone has passed or been surgically removed.
Table 2: History, Recurrent, and Family History Kidney Stone Codes
| ICD-10 Code | Description | Common Search Term |
|---|---|---|
| Z87.442 | Personal history of urinary (tract) calculi | history of kidney stones icd 10 |
| Z87.442 | Also used for | hx of kidney stones icd 10 |
| N20.0 (with recurrence noted in documentation) | Recurrent nephrolithiasis, active stone | recurrent nephrolithiasis icd 10 |
| Z83.51 | Family history of diseases of the kidney and ureter | family history of kidney stones icd 10 |
| N20.0 | Bilateral nephrolithiasis (documented in clinical notes, single code used) | bilateral nephrolithiasis icd 10 |
Notice that “hx of kidney stones ICD-10” and “history of nephrolithiasis ICD-10” both point to the same underlying code, Z87.442, since ICD-10-CM does not distinguish between the phrasing “history of” and “hx of” — both describe a resolved, past condition rather than an active diagnosis.
Why Accurate ICD-10 Coding for Kidney Stones Matters for Billing
For medical billing teams, getting the ICD-10 code for kidney stones right the first time has a direct financial impact. Payers increasingly cross-reference diagnosis codes against imaging reports, procedure codes, and clinical notes. If a claim lists an active nephrolithiasis code (N20.0) but the visit note describes a follow-up for a stone that already passed, the mismatch can result in claim denial or a request for additional documentation. Practices that outsource this review to a dedicated team, such as Revex Square’s urology billing services, typically see fewer denials because every claim is checked against documentation before submission.
Similarly, using N20.9 (urolithiasis, unspecified) when the physician’s notes clearly specify kidney versus ureter involvement is considered under-coding, which can undervalue the complexity of the visit and reduce appropriate reimbursement. Coders should always default to the most specific code supported by the documentation rather than defaulting to an unspecified code out of convenience.
Table 3: Common Kidney Stone Coding Errors and How to Fix Them
| Coding Error | Why It’s a Problem | Correct Approach |
|---|---|---|
| Using N20.0 for a resolved stone at a follow-up visit | Signals an active condition that no longer exists | Use Z87.442 for history of kidney stones |
| Coding N20.9 when kidney vs. ureter location is documented | Under-specifies the diagnosis | Use N20.0 or N20.1 based on documented location |
| Searching for a laterality-specific code (left/right) | ICD-10-CM has no laterality option for N20 | Use N20.0 and document laterality in clinical notes only |
| Omitting N13.2 when hydronephrosis is present with obstruction | Misses a clinically significant complication | Code N13.2 in addition to the stone code when obstruction is documented |
| Coding staghorn calculus as a separate diagnosis | Staghorn calculus is not a distinct ICD-10 category | Use N20.0 with documentation describing the staghorn morphology |
Coding for Ureteral Stones by Location
Because so many claims involve stones lodged specifically in the ureter, it’s worth addressing left ureteral stone ICD-10 and right ureteral stone ICD-10 searches directly. As with kidney stones, ICD-10-CM does not offer laterality-specific codes for ureteral calculi. The applicable code remains N20.1 for any ureteral stone, whether left, right, or bilateral, with the specific side documented in the physician’s clinical note rather than reflected in the diagnosis code itself.
This is a frequent source of confusion for practices transitioning from older coding systems or for coders new to urology billing, since many other ICD-10 categories do include laterality (such as fracture codes). Urinary calculus codes are a notable exception.
International Coding Variations
Outside the United States, related searches such as kode diagnosis nefrolitiasis (Indonesian) and kode ICD 10 batu saluran kemih reflect the same underlying clinical question asked in different languages and regions. While the WHO’s international ICD-10 base classification is broadly similar across countries, US-based practices should always confirm they are using the ICD-10-CM (Clinical Modification) version maintained by the CDC and CMS, since this is the version required for US insurance billing and differs slightly in structure from the base international ICD-10 codes used elsewhere.
CPT Codes Commonly Paired with Kidney Stone ICD-10 Codes
For billing teams, the ICD-10 code for kidney stone diagnosis is only half of a clean claim — it must also pair logically with the CPT procedure code being billed. Payers frequently check that the diagnosis code supports the medical necessity of the procedure. Some of the most common pairings include:
- CT abdomen/pelvis without contrast, paired with an active N20.0, N20.1, or N20.2 diagnosis
- Ureteroscopy with stone removal, paired with N20.1 or N20.2 depending on stone location
- ESWL procedures, paired with N20.0 for kidney-based stones
- Stent placement, often paired with N13.2 when obstruction is documented alongside the stone
Billing teams that routinely handle urology claims should build a standing reference that maps each common procedure to its supporting kidney stone ICD-10 code, since mismatched pairings are one of the leading causes of avoidable claim rejections in urology billing. For practices that would rather hand this off entirely, Revex Square offers specialty-specific coding audits that catch these mismatches before claims are submitted.
Best Practices for Doctors Documenting Kidney Stone Diagnoses
To help billing teams assign the correct ICD-10 code for kidney stone diagnoses without back-and-forth queries, physicians should aim to document the following details clearly in every visit note:
- Location of the stone: kidney, ureter, or both
- Whether the stone is a new, active finding or a resolved/past episode
- Presence of obstruction, hydronephrosis, or infection
- Whether the case is recurrent or the patient’s first episode
- Any relevant family history, since this can affect risk stratification and future coding
When this information is documented clearly, coders can confidently select between N20.0, N20.1, N20.2, N20.9, Z87.442, or the appropriate combination code, without guessing or defaulting to unspecified categories that may reduce claim accuracy.
Special Considerations: Pregnancy, Pediatrics, and Prior Authorization
Kidney stone coding requires extra attention in certain patient populations and billing scenarios.
Pregnant patients: Nephrolithiasis during pregnancy still uses the standard N20 category codes, but many practices choose to add a secondary code from the pregnancy complications chapter (O26.83-) to reflect that the condition is being managed in the context of pregnancy. This additional context can matter for both clinical coordination and payer review, since imaging choices are often modified to protect the fetus.
Pediatric patients: Kidney stones are less common in children but are increasingly diagnosed due to dietary and hydration factors. The same N20 codes apply regardless of age, though pediatric urology visits often carry additional documentation requirements around growth, hydration counseling, and dietary referrals that should be reflected in the visit note to support the billed level of service.
Prior authorization: Many payers require prior authorization before approving lithotripsy, ureteroscopy, or PCNL procedures. Since the authorization request is built around the diagnosis code, an imprecise or unspecified code such as defaulting to N20.9 when the stone location is actually known can slow down or even derail the authorization process. Billing teams should confirm the most specific code available before submitting any prior authorization request tied to a kidney stone procedure.
Building a Kidney Stone Coding Reference for Your Practice
Practices that see a steady volume of urology patients benefit from creating an internal quick-reference guide built around the tables in this article. A simple laminated sheet or shared digital document listing the core nephrolithiasis ICD-10 codes, the history codes, and the common CPT pairings can dramatically cut down on coding queries between physicians and billing staff. This is particularly valuable for multi-specialty clinics where kidney stone visits may be handled by primary care, emergency medicine, and urology providers who each have varying familiarity with urology-specific coding nuances.
Regularly auditing a sample of kidney stone claims checking that the diagnosis code matches the documented stone location, that history codes are used appropriately for resolved cases, and that obstruction codes are added when clinically relevant — can catch small errors before they accumulate into a pattern that draws payer scrutiny.
Conclusion
Correctly applying the ICD-10 code for kidney stones is essential for both clinical accuracy and financial health of a medical practice. From the foundational N20.0 ICD-10 code for active kidney stones, to N20.1 for ureteral stones, Z87.442 for history of kidney stones, and N13.2 for obstructive complications, each code tells a specific part of the patient’s clinical story. Doctors and coding teams who understand these distinctions — including the fact that laterality is documented clinically rather than coded separately — will see fewer denials, cleaner audits, and faster reimbursement cycles.
For practices handling a high volume of urology claims, building a quick-reference sheet based on the tables above can save significant time during chart review and claims submission, while also reducing the risk of costly coding errors.
If your practice wants expert help keeping kidney stone claims accurate and denial-free, get in touch with Revex Square for a free billing audit.
Frequently Asked Questions (FAQs)
1. What is the ICD-10 code for kidney stones?
The primary ICD-10 code for kidney stones is N20.0, which stands for “Calculus of kidney.”
2. What is the ICD-10 code for nephrolithiasis?
Nephrolithiasis is coded as N20.0, the same code used for kidney stones in general.
3. Is there a separate ICD-10 code for left or right kidney stones?
No, ICD-10-CM does not include laterality for kidney stone codes; N20.0 is used regardless of side, with laterality noted in clinical documentation.
4. What is the ICD-10 code for a history of kidney stones?
Z87.442, “Personal history of urinary (tract) calculi,” is used when a patient has had kidney stones in the past but has no active stone currently.
5. What is the ICD-10 code for a ureteral stone?
N20.1 is used for calculus of the ureter, commonly referred to as a ureteral stone.
6. What is the N20.0 ICD-10 code used for?
N20.0 specifically refers to calculus of the kidney and is the standard code for active nephrolithiasis.
7. What is the ICD-10 code for urolithiasis?
N20.9 is used for urinary calculus, unspecified, when the exact location of the stone is not documented.
8. What ICD-10 code is used for a staghorn calculus?
Staghorn calculus is coded as N20.0, since it is a subtype of kidney stone rather than a distinct diagnosis category.
9. What is the ICD-10 code for kidney stones with hydronephrosis?
N13.2 is used when hydronephrosis with obstruction is documented alongside a renal or ureteral calculus.
10. What is the ICD-10 code for bilateral nephrolithiasis?
Bilateral kidney stones are still coded as N20.0, with the bilateral nature documented in the clinical notes rather than reflected in a separate code.
