Acute kidney injury (AKI) is coded in ICD-10-CM to category N17, Acute kidney failure. When a provider documents “acute kidney injury,” “acute kidney failure” or “acute renal failure” with no further detail, the code is N17.9. When the provider documents a more specific type, such as acute tubular necrosis (ATN), the code changes to N17.0 or another N17 subcode, and the severity weighting of an inpatient claim can change with it.
This guide explains what each N17 code means, how to code AKI on CKD, sepsis-related and contrast-related AKI, how to handle prerenal and resolved AKI, and what documentation a coder needs before reporting anything more specific than N17.9.
Short Answer – AKI ICD10
AKI, acute kidney failure and acute renal failure = N17.9 by default. N17.0 requires documented ATN. N17.1 = cortical necrosis. N17.2 = medullary necrosis. N17.8 = other specified acute kidney failure. Add an N18 code when CKD is also present.
| Code | Official descriptor | Use when | MS-DRG status |
| N17.0 | Acute kidney failure with tubular necrosis | Provider documents ATN (ischemic, septic or toxic) | MCC |
| N17.1 | Acute kidney failure with acute cortical necrosis | Provider documents acute cortical necrosis (rare) | MCC |
| N17.2 | Acute kidney failure with medullary necrosis | Provider documents medullary necrosis (rare) | MCC |
| N17.8 | Other acute kidney failure | Provider documents a specified type not captured by N17.0–N17.2 | CC |
| N17.9 | Acute kidney failure, unspecified | AKI, acute kidney failure or acute renal failure with no further specification | CC |
Why N17.9 vs N17.0 Matters for Billing
Under MS-DRG, N17.9 and N17.8 are CC (complication or comorbidity) codes, while N17.0, N17.1 and N17.2 are MCC (major complication or comorbidity) codes. A secondary diagnosis of ATN can move an inpatient stay into a higher-weighted DRG, which is why payers review these claims closely.
Code ATN only when the provider documents it and the record supports it. Supporting findings typically include a sustained creatinine rise that does not correct with fluid resuscitation, urine microscopy findings and a documented precipitating event such as hypotension, sepsis or nephrotoxin exposure. A coder cannot assign N17.0 from lab values alone. If the indicators are present but ATN is not documented, send a compliant provider query (template below).
How to Code AKI Based on Documentation
AKI with no type or cause documented: N17.9
The Alphabetic Index entry for acute, nontraumatic kidney injury leads to N17.9. Descriptors such as “mild,” “oliguric,” “nonoliguric” or a KDIGO stage do not change the code.
Acute tubular necrosis: N17.0
Report N17.0 when the provider documents ATN, including ischemic, septic or toxic ATN. Also code the underlying cause (for example sepsis, hypotension or a nephrotoxic drug) according to the guidelines for that condition.
Cortical and medullary necrosis: N17.1 and N17.2
These are uncommon and need explicit provider documentation, usually supported by imaging or biopsy. Do not infer them from the clinical picture.
Prerenal and postrenal AKI
“Prerenal” and “postrenal” describe the cause of the AKI (reduced kidney perfusion or urinary obstruction), not a separate diagnosis. Code the underlying condition as well, for example hypovolemia, heart failure or an obstructive uropathy (N13.-). Prerenal azotemia alone is not the same as documented kidney failure and indexes separately (R39.2).
AKI on chronic kidney disease
Report both the N17 code for the AKI and the N18 code for the CKD stage (N18.1–N18.6; stage 3 is split into N18.30, N18.31 and N18.32). If the patient also has hypertension, use the hypertensive CKD combination code (I12.- or I13.-) with the N18 code, then add N17. Sequencing of the N17 code follows the circumstances of the encounter.
AKI with sepsis or hypotension
For AKI due to sepsis, the underlying infection (for example A41.9) is sequenced first, followed by R65.20 or R65.21 when severe sepsis is documented, then N17.x as the associated organ dysfunction. If the provider documents septic ATN, report N17.0. Do not assume AKI is caused by sepsis; if the relationship is unclear, query the provider. For AKI due to hypotension, code the hypotension per documentation and N17.9, or N17.0 if ATN is documented.
Contrast-induced and drug-induced AKI
Contrast-induced nephropathy has its own code, N14.11. When AKI or ATN is also documented, add the N17 code that matches the documentation and the adverse-effect code for the agent (for example T50.8X5A for diagnostic agents). For other nephrotoxic drugs, add the adverse-effect code for the specific drug.
Postpartum and newborn AKI
Postpartum acute kidney failure is reported with O90.49, and the tabular instruction at O90.4- directs an additional N17 code to specify the type. For newborns, renal failure in the perinatal period indexes to the P96 category (P96.0); confirm with the provider documentation and the P96 notes.
Resolved AKI and history of AKI
If the AKI has resolved and is no longer evaluated, monitored or treated, do not report N17.x. When the history affects current care, personal history of other diseases of the urinary system (Z87.448) may apply.
AKI stages 1, 2 and 3
KDIGO staging describes severity but has no matching ICD-10-CM code. The stage belongs in the clinical documentation and does not change N17.
|
KDIGO stage |
Serum creatinine |
Urine output |
| Stage 1 | 1.5–1.9 × baseline, or rise ≥ 0.3 mg/dL | < 0.5 mL/kg/h for 6–12 hours |
| Stage 2 | 2.0–2.9 × baseline | < 0.5 mL/kg/h for ≥ 12 hours |
| Stage 3 | ≥ 3.0 × baseline, or ≥ 4.0 mg/dL, or start of renal replacement therapy | < 0.3 mL/kg/h for ≥ 24 hours, or anuria for ≥ 12 hours |
AKI Documentation Checklist for Providers
AKI is defined by KDIGO as a creatinine rise of at least 0.3 mg/dL within 48 hours, a rise to at least 1.5 times baseline known or presumed to have occurred within the prior 7 days, or urine output below 0.5 mL/kg/h for 6 hours. Strong documentation includes:
- The diagnosis in clear terms: AKI, acute kidney failure or ATN, not only “elevated creatinine”
- Baseline and peak creatinine with dates, and urine output where relevant
- The type or etiology: prerenal, intrinsic (including ATN) or postrenal
- The cause and the provider’s statement linking it to the AKI (sepsis, hypotension, contrast, medication, obstruction)
- Presence and stage of CKD, if any
- Evaluation and treatment: IV fluids, holding nephrotoxic drugs, nephrology consult, dialysis
- Status: ongoing, improving or resolved
Common AKI Coding Mistakes
- Reporting N17.0 from lab values alone. ATN must be documented by the provider.
- Using N17.9 when ATN is documented. This under-reports severity.
- Omitting the N18 code on acute-on-chronic cases. Both conditions need to be captured.
- Coding resolved AKI as active. Use history codes only when relevant.
- Assuming AKI is due to sepsis. The provider must link them, or you query.
- Treating prerenal azotemia as AKI. They are different diagnoses.
- Adding modifiers to diagnosis codes. Modifiers apply to CPT and HCPCS procedure codes, not ICD-10-CM codes.
Why Correct AKI ICD10 Coding is Important
Proper coding ensures:
- Accurate reimbursement for services rendered
- Compliance with CMS and insurance requirements
- Reduced claim denial risk
- Clear medical records for continuity of care
AKI ICD10 Based on Type and Cause
- Pre-renal AKI ICD10 codes: Caused by decreased renal perfusion (e.g., hypovolemia, heart failure)
- Intrinsic renal AKI ICD10 codes: Due to damage within the kidney (e.g., ATN, cortical necrosis)
- Post-renal AKI ICD10 codes: Caused by obstruction of urinary flow (e.g., stones, tumors)
AKI ICD10 Codes by Classification
N17.0 – Acute Kidney Failure with Tubular Necrosis
- Most common form of AKI
- Often results from ischemia or nephrotoxins
- Billable for reimbursement purposes
N17.1 – Acute Kidney Failure with Acute Cortical Necrosis
- Rare, severe AKI type
- Frequently post-infection or postpartum
- Requires detailed clinical documentation
N17.2 – Acute Kidney Failure with Medullary Necrosis
- Often associated with infection or sickle cell disease
- Must confirm via lab and imaging
N17.8 – Other Specified Acute Kidney Failure
- Covers miscellaneous or rare causes not captured by N17.0–N17.2
N17.9 – Acute Kidney Failure, Unspecified
- Use when type or cause of AKI is unknown
AKI ICD10 Comparison Table
| ICD-10 Code | Description | Billable | Clinical Notes | Common Synonyms |
| N17.0 | Acute kidney failure with tubular necrosis | Yes | Most common type | Acute tubular necrosis, ATN |
| N17.1 | Acute kidney failure with cortical necrosis | Yes | Rare, severe | Acute cortical necrosis |
| N17.2 | Acute kidney failure with medullary necrosis | Yes | Often post-infection | Medullary necrosis |
| N17.8 | Other specified acute kidney failure | Yes | Miscellaneous causes | AKI other specified |
| N17.9 | Acute kidney failure, unspecified | Yes | Default when type unknown | AKI unspecified |
Step-by-Step Guide to Coding AKI ICD10
Step 1 – Identify the Type of AKI
- Determine pre-renal, intrinsic, or post-renal
- Review lab results: serum creatinine, BUN, urine output
Step 2 – Verify Clinical Documentation
- Confirm onset, cause, severity
- Check for associated conditions (e.g., sepsis, obstruction)
Step 3 – Select the Correct ICD-10 Code
- Map the clinical diagnosis to ICD-10 codes (N17.0–N17.9)
Step 4 – Consider Additional Coding
- Use additional codes for underlying conditions (e.g., B33.4 for viral infections)
Step 5 – Check Billable vs Non-Billable Codes
- Ensure only billable codes are used for reimbursement
Step 6 – Apply Modifiers if Needed
- When AKI is secondary to procedures or trauma
AKI ICD10 vs Chronic Kidney Disease Codes
| Condition | ICD-10 Range | Key Notes |
| AKI | N17.0–N17.9 | Sudden onset, often reversible |
| CKD | N18.1–N18.9 | Chronic, progressive kidney damage |
| Acute-on-chronic | N17.0–N17.9 + N18.x | Use both codes to capture acute worsening |
AKI ICD10 vs Chronic Kidney Disease Codes
| Condition | ICD-10 Range | Key Notes |
| AKI | N17.0–N17.9 | Sudden onset, often reversible |
| CKD | N18.1–N18.9 | Chronic, progressive kidney damage |
| Acute-on-chronic | N17.0–N17.9 + N18.x | Use both codes to capture acute worsening |
People Also Ask – AKI ICD10
What is the ICD-10 code for acute kidney injury?
- Typically 0–N17.9, depending on type
What is the difference between N17.0 and N17.9?
- 0: Tubular necrosis, specific cause
- 9: Unspecified AKI, unknown cause
Can AKI and CKD be coded together?
- Yes, especially for acute-on-chronic cases
Is N17.9 billable?
- Yes, but only when type is unknown
What additional codes should be used with AKI ICD10?
- Codes for sepsis, nephrotoxins, infections
How to code AKI due to contrast agents?
- Use N17.0 or N17.8 depending on documentation
- Add T codes for contrast-induced injury if required
Does Medicare cover AKI treatment based on ICD10 coding?
- Yes, provided accurate coding and documentation are submitted
What is the clinical significance of each AKI ICD10 code?
- Helps guide treatment, prognosis, and reimbursement
Frequently Asked Questions About AKI ICD-10 Coding
What is the ICD-10 code for acute kidney injury (AKI)?
AKI is reported with N17.9, Acute kidney failure, unspecified, unless the provider documents a more specific type such as acute tubular necrosis (N17.0), cortical necrosis (N17.1), medullary necrosis (N17.2) or another specified type (N17.8).
Is acute renal failure coded the same as AKI?
Yes. In the ICD-10-CM Alphabetic Index, acute kidney injury, acute kidney failure and acute renal failure without further specification all lead to N17.9.
What is the difference between N17.0 and N17.9?
N17.0 is acute kidney failure with tubular necrosis and requires the provider to document ATN. N17.9 is used when AKI is documented without a specified type. N17.0 is an MCC and N17.9 is a CC under MS-DRG, so the choice can affect inpatient reimbursement.
Can AKI and CKD be coded together?
Yes. For acute kidney injury on chronic kidney disease, report the N17 code for the AKI and the N18 code for the CKD stage. If hypertension is also present, use the hypertensive CKD combination code (I12.- or I13.-) with the N18 code.
Is there an ICD-10 code for AKI stage 1, 2 or 3?
No. KDIGO stages describe severity, but ICD-10-CM has no stage-specific AKI codes. Stage, mild, oliguric or nonoliguric descriptors do not change the N17 code.
What code do I use for resolved AKI?
Do not report N17 for AKI that has resolved and is no longer evaluated, monitored or treated. If the history is relevant to the current encounter, Z87.448 (personal history of other diseases of the urinary system) may apply.
Is N17.9 billable?
Yes, N17.9 is a valid billable code. Payers may still expect more specificity when the medical record supports a specific type of AKI.
How do I code AKI due to sepsis?
Follow the sepsis sequencing guidelines: the underlying infection first, R65.20 or R65.21 when severe sepsis is documented, then N17 as the acute organ dysfunction, provided the provider links the AKI to sepsis. Query the provider if the relationship is unclear.
Get Help With AKI and Nephrology Coding
Under-specified AKI documentation is a common reason for DRG downgrades and payer denials. Our medical coding services team can audit your AKI and CKD claims, and our denial management services team works on the denials that follow. For a wider look at how diagnosis coding affects billing, read our guide to the role of ICD-10 coding in medical billing.
Conclusion – AKI ICD10
Accurate coding of AKI ICD10 is critical for billing, compliance, and patient care. The key codes are N17.0–N17.9, with proper selection based on clinical documentation. By following step-by-step guidance and using tables and cheat sheets, clinicians and coders can ensure accuracy, reimbursement, and quality care.
