Kidney Failure ICD-10 Coding Guide: The Complete Reference for Medical Coders in 2026

 Why Accurate Kidney Failure ICD-10 Coding Matters

Medical billing errors cost the U.S. healthcare system billions of dollars annually — and kidney failure coding is one of the most error-prone areas in ICD-10-CM documentation. For hospitals, nephrology practices, and outpatient dialysis centers, mastering the kidney failure ICD-10 coding guide is not optional. It directly impacts reimbursement accuracy, compliance audits, and patient care quality metrics.

Whether you are a certified professional coder (CPC), a clinical documentation improvement (CDI) specialist, or a nephrologist reviewing your own charts, this comprehensive guide will walk you through every critical ICD-10 code for kidney failure  from acute kidney injury (AKI) to end-stage renal disease (ESRD) and explain how to apply them correctly in real-world clinical scenarios.

Understanding the ICD-10-CM Structure for Kidney Failure

The ICD-10-CM (International Classification of Diseases, 10th Revision, Clinical Modification) organizes kidney and urinary tract diseases under Chapter 14: Diseases of the Genitourinary System (N00–N99). Within this chapter, kidney failure and renal disease codes fall primarily between N17 and N19.

Before diving into specific codes, every medical coder must understand the fundamental distinction between the two major categories:

• Acute Kidney Failure (AKF/AKI): A sudden loss of kidney function, typically reversible, coded under N17.x
• Chronic Kidney Disease (CKD): A progressive, long-term deterioration of kidney function, coded under N18.x

This distinction is the foundation of any kidney failure ICD-10 coding guide. Misclassifying acute as chronic or vice versa  leads to claim denials and compliance risk.

Section 1: Acute Kidney Failure ICD-10 Codes (N17)

Acute kidney failure ICD-10 coding requires coders to identify the specific type of structural damage involved. The N17 category breaks down as follows:

N17.0 – Acute Kidney Failure with Tubular Necrosis

This code applies when there is documented acute tubular necrosis (ATN), the most common cause of intrinsic AKI. ATN occurs when the renal tubules are damaged, usually from ischemia or nephrotoxic agents such as aminoglycoside antibiotics, contrast dye, or NSAIDs.

Coding tip: When the physician documents "ATN" in the setting of AKI, assign N17.0. Do not default to N17.9 if a more specific etiology is documented.

N17.1 – Acute Kidney Failure with Acute Cortical Necrosis

This is a rare but severe form of AKI characterized by necrosis of the renal cortex. It is associated with obstetric complications, septic shock, and hemolytic uremic syndrome (HUS).

N17.2 – Acute Kidney Failure with Medullary Necrosis

Also known as renal papillary necrosis in the acute setting, this code covers necrosis involving the medullary tissue. It may be linked to analgesic nephropathy, diabetes, or sickle cell disease.

N17.8 – Other Acute Kidney Failure

Use this code when the physician documents acute kidney failure with a specific type that does not fit into the above subcategories. Always query the treating physician if the documentation is unclear.

N17.9 – Acute Kidney Failure, Unspecified

This is the default code when the type of acute kidney failure is not further specified in the clinical documentation. Coders should make every effort to obtain more specific documentation before defaulting to N17.9, as it may trigger additional documentation requests during audits.

Key Coding Guideline: When AKI is present with CKD, assign codes for both conditions. According to ICD-10-CM Official Guidelines, acute kidney failure superimposed on chronic kidney disease requires dual coding.

Section 2: Chronic Kidney Disease ICD-10 Codes (N18)

The chronic kidney disease ICD-10 codes under N18 are staged according to the GFR (Glomerular Filtration Rate) classification system developed by the National Kidney Foundation's KDIGO guidelines. The staging ranges from Stage 1 (kidney damage with normal or high GFR) to Stage 5 (kidney failure/ESRD).

N18.1 – Chronic Kidney Disease, Stage 1

GFR ≥ 90 mL/min/1.73m², with evidence of kidney damage (e.g., proteinuria, hematuria, structural abnormalities).

N18.2 – Chronic Kidney Disease, Stage 2 (Mild)

GFR 60–89 mL/min/1.73m². Often asymptomatic. Commonly detected incidentally on lab work.

N18.3 – Chronic Kidney Disease, Stage 3 (Moderate)

GFR 30–59 mL/min/1.73m². This is further subdivided:

• N18.31 – CKD Stage 3a: GFR 45–59 mL/min/1.73m²
• N18.32 – CKD Stage 3b: GFR 30–44 mL/min/1.73m²

Coding note: The subdivision of Stage 3 into 3a and 3b was added in ICD-10-CM FY2022 updates. Coders must ensure their encoder software is updated to reflect this change.

N18.4 – Chronic Kidney Disease, Stage 4 (Severe)

GFR 15–29 mL/min/1.73m². At this stage, patients typically require nephrologist management and preparation for renal replacement therapy.

N18.5 – Chronic Kidney Disease, Stage 5

GFR < 15 mL/min/1.73m². This stage indicates kidney failure. Use this code when ESRD is not present and the patient is not on dialysis.

N18.6 – End-Stage Renal Disease (ESRD)

This is one of the most clinically significant codes in the kidney failure ICD-10 coding guide. N18.6 is assigned when the patient has CKD Stage 5 AND requires chronic dialysis (hemodialysis or peritoneal dialysis) or has received a kidney transplant.

Critical distinction: Do not confuse N18.5 (CKD Stage 5 without dialysis) with N18.6 (ESRD/CKD Stage 5 with dialysis). This is one of the most audited code pairs in nephrology billing.

N18.9 – Chronic Kidney Disease, Unspecified

Use only when the stage is not documented. CDI specialists should flag charts with N18.9 for physician query opportunities to obtain staging specificity.

Section 3: Unspecified Kidney Failure – N19

N19 – Unspecified Kidney Failure is used when the physician documents kidney failure but does not specify whether it is acute or chronic, and CKD is not documented anywhere in the record. This is a code of last resort in the kidney failure ICD-10 coding framework.

Coding guidance: If uremia is present without further specification, N19 may be appropriate. However, coders should always review the full record including lab trends, problem lists, and past medical history before assigning N19. A thorough query to the treating physician is strongly recommended.

Section 4: Key ICD-10 Coding Scenarios for Kidney Failure

Understanding isolated codes is not enough. Real-world medical coding requires the ability to sequence codes accurately in complex clinical scenarios. Here are the most common situations encountered in nephrology coding.

Scenario 1: AKI on Top of CKD

A patient is admitted with AKI. The history shows pre-existing CKD Stage 3b.

Correct coding: N17.9 (AKI, unspecified) + N18.32 (CKD Stage 3b)

Per ICD-10-CM guidelines, when AKI is superimposed on CKD, assign a code from both N17 and N18. The sequencing (which is principal) depends on the circumstance of admission.

Scenario 2: ESRD on Dialysis

A patient with ESRD presents for routine hemodialysis.

Correct coding: N18.6 (ESRD) + Z99.2 (Dependence on renal dialysis)

Always assign Z99.2 as an additional code when the patient is on chronic dialysis. This is a standard ICD-10-CM coding guideline requirement for ESRD patients.

Scenario 3: Post-Kidney Transplant with CKD

A patient had a kidney transplant five years ago and now has CKD Stage 2.

Correct coding: N18.2 (CKD Stage 2) + Z94.0 (Kidney transplant status)

The presence of a functioning transplant does not eliminate the CKD code. CKD in transplant recipients is common and must be coded separately.

Scenario 4: Diabetic Nephropathy with CKD

A Type 2 diabetic patient presents with CKD Stage 4 due to diabetic nephropathy.

Correct coding: E11.65 (Type 2 diabetes mellitus with hyperglycemia and CKD) + N18.4 (CKD Stage 4)

ICD-10-CM includes combination codes for diabetes with CKD. The diabetic nephropathy etiology code E11.65 already implies the CKD relationship, but a secondary code from N18 is still required to identify the stage.

Section 5: Common ICD-10 Kidney Failure Coding Errors to Avoid

Even experienced coders fall into predictable traps. Based on CMS audit findings and OIG (Office of Inspector General) reports, these are the most frequent kidney failure ICD-10 coding errors:

1. Assigning N18.9 instead of a staged CKD code Lab values and nephrology consult notes almost always contain GFR data that supports staging. Use them.

2. Failing to code Z99.2 with N18.6 Omitting the dialysis dependence code is a consistent audit finding in ESRD patient encounters.

3. Confusing N18.5 and N18.6 CKD Stage 5 without dialysis (N18.5) is coded differently than ESRD (N18.6). Always verify dialysis status.

4. Not querying for AKI vs. CKD distinction Documentation that says "renal insufficiency" or "elevated creatinine" is insufficient. A physician query is required.

5. Ignoring the underlying cause of AKI If ATN, cortical necrosis, or medullary necrosis is documented, assign the appropriate N17.0, N17.1, or N17.2  not the default N17.9.

Section 6: Additional Codes Frequently Used with Kidney Failure

A comprehensive kidney failure ICD-10 coding guide must also cover the additional codes commonly reported alongside the primary kidney failure codes:

Code	Description
Z99.2	Dependence on renal dialysis
Z94.0	Kidney transplant status
Z49.01	Encounter for fitting of extracorporeal dialysis
Z49.31	Encounter for adequacy testing of hemodialysis
E11.65	Type 2 DM with hyperglycemia and CKD
I12.9	Hypertensive CKD with CKD Stage 1–4
I13.10	Hypertensive heart and CKD, unspecified
N04.9	Nephrotic syndrome, unspecified
R80.9	Proteinuria, unspecified

Hypertension and CKD combination codes (I12/I13) deserve special mention. When hypertension and CKD are both documented, ICD-10-CM assumes a causal relationship. Do not code them separately as N18.x + I10. Instead, use the hypertensive CKD combination code from category I12 or I13, then add the appropriate N18 stage code.

Section 7: Tips for CDI Specialists Working on Kidney Failure Cases

Clinical Documentation Improvement (CDI) specialists play a critical role in the kidney failure ICD-10 coding ecosystem. Here are targeted recommendations:

Query opportunity triggers:

• Creatinine elevation of  1.5x baseline without a documented diagnosis of AKI
• GFR  60 without a documented CKD stage
• Dialysis orders without an ESRD or CKD diagnosis
• "Renal insufficiency" or "renal impairment" without further specification

Physician query best practices:

• Reference the specific lab values (GFR, BUN, creatinine) that prompted the query
• Offer compliant, non-leading query formats with multiple options (AKI, CKD, ESRD, or clinically undetermined)
• Always document the physician's response before the coder assigns the final code

Conclusion: Mastering the Kidney Failure ICD-10 Coding Guide

Kidney failure ICD-10 coding is one of the most nuanced areas in nephrology medical billing. From N17 acute kidney failure codes to N18 chronic kidney disease staging and the clinically critical N18.6 ESRD designation, each code carries significant implications for reimbursement, compliance, and quality reporting.

The bottom line for coders and CDI teams: never accept vague documentation when specific staging is available, always assign required additional codes like Z99.2 for dialysis-dependent patients, and leverage every appropriate physician query opportunity to capture the full clinical picture.

Staying current with annual ICD-10-CM updates  such as the FY2022 addition of N18.31 and N18.32 is equally essential. Bookmark this kidney failure ICD-10 coding guide, share it with your coding team, and revisit it each October when CMS releases new code updates.