Crystal's Coder Hub🧬 ICD-10 CM N18.2 — Chronic Kidney Disease, Stage 2 (Mild)
Billable Code Confirmed
ICD-10-CM N18.2 is a valid, billable 5-character ICD-10-CM code for FY2026. Characters 1-3 (N18) identify the category of chronic kidney disease; the 5th character (.2) specifies Stage 2, defined by kidney damage with a mildly decreased eGFR of 60-89 mL/min/1.73 m². No additional characters are required — the code is complete as written.
Non-Billable Parent Codes — Never Submit These
- ❌
N18— 3-character header — lacks stage specificity; not a valid billable codeAlways submit N18.2 (all 5 characters) when CKD, Stage 2 is documented. Verify the underlying cause is coded first per the mandatory “Code First” instruction at the N18 category heading.
Clinical Context: Code First the Underlying Cause
ICD-10-CM N18.2 must be sequenced as a secondary code whenever CKD is caused by or associated with hypertension (I12.-, I13.-) or diabetes mellitus (E08.22, E09.22, E10.22, E11.22, E13.22). The “Code First” instruction at the N18 category heading is mandatory — submitting N18.2 before the causative hypertensive or diabetic combination code is a sequencing compliance violation. Use additional code Z94.0 for kidney transplant status or E88.A for associated cachexia when documented.
Code Classification
ICD-10-CM Diagnosis Code — wRVU, assistant-at-surgery payable, and global period fields are not applicable to ICD-10-CM diagnosis codes. For procedure-level reference, see the CPT Procedural Crosswalk and ICD-10-PCS Crosswalk sections below.
🔍 Code Description
ICD-10-CM N18.2 classifies Chronic kidney disease, Stage 2 (mild) — defined by the presence of kidney damage markers (e.g., proteinuria, microalbuminuria, hematuria, structural abnormalities on imaging) sustained for more than 3 months, accompanied by a mildly decreased estimated glomerular filtration rate of 60-89 mL/min/1.73 m². Like Stage 1, Stage 2 requires both a damage marker and a reduced GFR to be properly classified — an eGFR of 60-89 without any identifiable damage marker does not meet KDIGO criteria for CKD and should not be coded as such absent provider confirmation.
Patients with Stage 2 CKD are frequently asymptomatic or have only subtle signs such as mild proteinuria or early hypertension-related renal changes. The most common underlying etiologies are hypertensive nephropathy and diabetic nephropathy, both of which drive the “Code First” sequencing requirement. Ongoing monitoring focuses on slowing disease progression through blood pressure control, RAAS blockade, and optimization of glycemic control to prevent advancement to Stage 3 and the HCC-weighted code range.
🌳 Code Tree / Hierarchy
N17-N19 Acute kidney failure and chronic kidney disease ❌ Non-billable block
│
├── N17 Acute kidney failure ❌ Non-billable category header
├── N18 Chronic kidney disease (CKD) ❌ Non-billable category header
│ │
│ ├── N18.1 Chronic kidney disease, stage 1 ✅ Billable
│ ├── N18.2 Chronic kidney disease, stage 2 (mild) ◀ THIS CODE ✅ Billable
│ ├── N18.30 Chronic kidney disease, stage 3 unspecified ✅ Billable
│ ├── N18.31 Chronic kidney disease, stage 3a ✅ Billable
│ ├── N18.32 Chronic kidney disease, stage 3b ✅ Billable
│ ├── N18.4 Chronic kidney disease, stage 4 (severe) ✅ Billable
│ ├── N18.5 Chronic kidney disease, stage 5 ✅ Billable
│ ├── N18.6 End stage renal disease ✅ Billable
│ └── N18.9 Chronic kidney disease, unspecified ✅ Billable
│
└── N19 Unspecified kidney failure ✅ Billable
Stage 2 Is the Last Stage Before HCC Credit Begins
N18.2 and N18.1 are the only CKD-stage codes that carry no HCC weight under CMS-HCC v28. Once a patient advances to Stage 3a (N18.31 → HCC 329, RAF ~0.127) or higher, every subsequent year’s risk-adjustment submission benefits from accurate CKD staging. Establishing precise Stage 2 documentation now creates a documented baseline that supports CDI continuity and HCC capture at the moment of progression — making accurate coding at this stage a long-term revenue integrity investment.
✅ Includes
The following clinical terms and scenarios map to N18.2 when documented:
- Chronic kidney disease, Stage 2 (mild) with eGFR 60-89 mL/min/1.73 m²
- Kidney damage with mildly decreased GFR and confirmed damage markers present >3 months
- CKD Stage 2 in the setting of documented hypertension — sequence I12.9 or I13.10 first
- CKD Stage 2 in the setting of documented diabetes — sequence applicable DM combination code (E08.22-E13.22) first
- CKD Stage 2 with kidney transplant status (append Z94.0)
- CKD Stage 2 with associated cachexia (append E88.A)
❌ Excludes
Excludes 1 — Cannot Be Coded Simultaneously with N18.2
| Code | Description | Note |
|---|---|---|
| N/A | No Excludes 1 notations at the N18.2 code level | Review category N18 header for “Code First” instructions before submitting any N18.x code |
Excludes 1 Violation Risk
There are no direct Excludes 1 notations specific to N18.2. The most common compliance error is sequencing N18.2 before the hypertensive or diabetic combination code — this is a “Code First” sequencing violation, not technically an Excludes 1 issue, but it carries the same audit and claim-denial risk. Always query the category N18 header in the tabular before sequencing.
Excludes 2 — May Be Coded in Addition if Separately Present
| Code | Description | Note |
|---|---|---|
| N/A | No Excludes 2 notations at the N18.2 code level | AKI (N17.x) may be coded simultaneously with CKD per AKI-on-CKD dual-coding guidelines; these conditions are not mutually exclusive |
📋 Clinical Overview
CKD Stage Comparison — Staging, HCC Weight, and Coding Status
CKD staging under KDIGO 2024 guidelines is based on both eGFR value and the presence of kidney damage markers sustained for >3 months. The table below places Stage 2 in context across the full CKD spectrum, including the pivot point at which HCC mapping begins.
| Feature | N18.2 — Stage 2 | N18.31 — Stage 3a | N18.4 — Stage 4 | N18.6 — ESRD |
|---|---|---|---|---|
| eGFR (mL/min/1.73m²) | 60-89 | 45-59 | 15-29 | Dialysis-dependent |
| Clinical description | Mild GFR reduction | Mild-to-moderate reduction | Severe reduction | Kidney failure |
| HCC Mapping (v28) | ❌ None | ✅ HCC 329 (RAF ~0.127) | ✅ HCC 327 (RAF ~0.514) | ✅ HCC 326 (RAF ~0.815) |
| CC/MCC Status (MS-DRG) | Neither | Neither | CC | MCC |
| Symptom burden | Subclinical; fatigue, mild proteinuria | Early metabolic changes | Uremic symptoms emerge | Dialysis-dependent |
| Code First instruction | ✅ Required (HTN/DM) | ✅ Required (HTN/DM) | ✅ Required (HTN/DM) | ✅ Required (HTN/DM) |
CDI Query Trigger — eGFR Trending Toward Stage 3
When inpatient or outpatient documentation shows an eGFR trending between 60-65 mL/min and the provider has previously documented Stage 2, a CDI query is appropriate to confirm whether the patient should now be staged as Stage 3a. Coders may not reclassify the CKD stage based on labs alone — provider confirmation is required. The query should present the current and prior eGFR values and ask the provider to confirm the current CKD stage.
Manifestations & Symptom Burden
CKD Stage 2 is frequently subclinical but may be associated with early manifestations that should each be coded separately when documented:
- Proteinuria / microalbuminuria: Ongoing damage marker; UACR 30-300 mg/g (microalbuminuria) or >300 mg/g (macroalbuminuria/proteinuria) should be documented and coded separately when discrete diagnosis is confirmed
- Hypertension: The most common comorbidity and causative factor; drives the I12.- or I13.- “Code First” sequencing requirement
- diabetic nephropathy: When DM is the documented cause, use DM combination code (**E08.22-E13.2**2) first, then N18.2
- Anemia of chronic kidney disease: Less prevalent at Stage 2 than later stages, but document and code D63.1 when confirmed by the provider
- Hyperlipidemia: Cardiovascular risk management is a standard component of Stage 2 CKD care; code E78.x when documented
Coding Manifestations
Always code documented manifestations and comorbidities to fully capture patient complexity. Key examples for Stage 2 CKD:
- D63.1 — Anemia in chronic kidney disease (when confirmed)
- E11.22 — Type 2 diabetes mellitus with diabetic chronic kidney disease, stage 2 (sequence before N18.2)
- I12.9 — Hypertensive chronic kidney disease with stage 1-2 CKD or unspecified CKD (sequence before N18.2)
💰 HCC Risk Adjustment (CMS-HCC v28)
| Field | Detail |
|---|---|
| CMS-HCC Model Version | v28 (2024-2026 Implementation) |
| HCC Assignment | ❌ Not HCC-Mapped |
| HCC Category | N/A |
| RAF Coefficient | N/A — No RAF contribution |
N18.2 does not map to any HCC category under CMS-HCC v28. CMS-HCC v28 reserves CKD risk-adjustment weight for Stage 3 and above, reflecting the higher expected resource utilization that begins at the moderate-CKD threshold.
Capture Annually — Stage 2 Is the Last Unmapped Stage
Although N18.2 carries no RAF weight, annual documentation of the CKD stage protects against a sudden unexplained jump from “no CKD documented” to “HCC-mapped Stage 3” upon progression. Payers and auditors may scrutinize gaps in CKD staging history. Ensure the causative code (I12.-, I13.-, or DM combination code) is captured annually, as these may independently contribute to the patient’s risk score. Per CMS-HCC v28 transition rules, both the v24 and v28 models are blended during the transition period — accurate diagnosis coding each year directly impacts blended RAF score calculations.
🏥 MS-DRG Assignment
MDC 11 — Diseases and Disorders of the Kidney and Urinary Tract
| DRG | Title | Est. Relative Weight* |
|---|---|---|
| DRG 682 | Renal Failure with MCC | ~1.80 - 2.10 |
| DRG 683 | Renal Failure with CC | ~1.00 - 1.20 |
| DRG 684 | Renal Failure without CC/MCC | ~0.60 - 0.75 |
Approximate. Verify against IPPS FY2026 Final Rule tables.
Sequencing and CC/MCC Status
N18.2 is neither a CC nor an MCC under the MS-DRG system and does not independently elevate DRG weight when sequenced as a secondary diagnosis. The most important DRG optimization opportunity in CKD Stage 2 admissions lies in accurate documentation of comorbidities: heart failure, anemia, metabolic acidosis, or AKI superimposed on CKD may function as CCs or MCCs and substantially change the DRG. When an attending documents CKD Stage 2 in the context of a deteriorating eGFR, query whether Stage 3 is more appropriate — the difference between N18.2 (no CC/MCC status) and N18.4 (CC status) can materially impact DRG reimbursement.
🔗 Related ICD-10-CM Codes
CKD Stage Variants — N18 Category
| Code | Description |
|---|---|
| N18.1 | Chronic kidney disease, stage 1 |
| N18.2 | Chronic kidney disease, stage 2 (mild) ← This Code |
| N18.30 | Chronic kidney disease, stage 3 unspecified |
| N18.31 | Chronic kidney disease, stage 3a |
| N18.32 | Chronic kidney disease, stage 3b |
| N18.4 | Chronic kidney disease, stage 4 (severe) |
| N18.5 | Chronic kidney disease, stage 5 |
| N18.6 | End stage renal disease |
| N18.9 | Chronic kidney disease, unspecified |
Causative / Combination Codes — Must Sequence Before N18.2
| Code | Description |
|---|---|
| I12.9 | Hypertensive chronic kidney disease with stage 1-2 CKD or unspecified CKD |
| I13.10 | Hypertensive heart and chronic kidney disease without heart failure, with stage 1-4 or unspecified CKD |
| E11.22 | Type 2 diabetes mellitus with diabetic chronic kidney disease, stage 2 |
| E10.22 | Type 1 diabetes mellitus with diabetic chronic kidney disease, stage 2 |
| E08.22 | Diabetes mellitus due to underlying condition with diabetic CKD, stage 2 |
| E09.22 | Drug or chemical induced diabetes mellitus with diabetic CKD, stage 2 |
| E13.22 | Other specified diabetes mellitus with diabetic CKD, stage 2 |
Related Renal and Associated Conditions — Code Separately When Documented
| Code | Description |
|---|---|
| N17.9 | Acute kidney failure, unspecified (code both when AKI superimposed on CKD Stage 2) |
| D63.1 | Anemia in chronic kidney disease |
| Z94.0 | Kidney transplant status (append when applicable) |
| E88.A | Cachexia associated with CKD (append when documented) |
🛠️ Commonly Associated CPT Codes (Nephrology / Primary Care)
Outpatient and Profee Setting Context
These CPT codes are commonly associated with the evaluation, management, and monitoring of CKD Stage 2 in nephrology and primary care settings. Most are E/M, laboratory, or diagnostic imaging codes. CKD Stage 2 management at this level rarely involves procedural intervention. Modifier -26 applies for provider interpretation-only billing when the facility owns the imaging equipment.
| CPT Code | Description | Profee Coding Notes (Modifier 26) |
|---|---|---|
| 99213 - 99215 | Office/outpatient E/M, established patient | Bill based on MDM or total time; CKD Stage 2 with hypertension and/or DM typically supports moderate MDM (99214); multiple comorbidities may support 99215 |
| 80053 | Comprehensive metabolic panel | BUN, creatinine, eGFR, electrolytes — bill as panel to avoid NCCI component bundling edits |
| 82043 | Microalbumin, urine (quantitative) | Key damage-marker test; NOT included in 80053; bill separately for UACR monitoring |
| 82570 | Creatinine, urine | Ordered with 82043 to calculate UACR; billable separately from 80053 |
| 76770 | Ultrasound, retroperitoneal (renal ultrasound) | Modifier -26 for interpretation only; evaluates renal size, cortical echogenicity, structural damage, and obstruction |
| 93306 | Echocardiography, complete with Doppler (TTE) | Associated when hypertensive CKD Stage 2 with suspected LVH or diastolic dysfunction |
NCCI Bundling Considerations
- Comprehensive metabolic panel (80053) includes creatinine (82565) — billing 80053 and 82565 together on the same date triggers an NCCI edit; submit only the panel.
- Microalbumin (82043) is not a component of 80053 and may be billed separately on the same date without a modifier.
- E/M (99213-99215) billed same-day as in-office lab interpretation requires Modifier -25 on the E/M to confirm a separately identifiable service beyond routine lab review.
🔬 ICD-10-PCS Crosswalk (Inpatient Procedures)
When N18.2 is an inpatient diagnosis, these PCS codes are relevant for associated inpatient procedures.
| PCS Section | Body System | Root Operation | Clinical Application |
|---|---|---|---|
| 0 (Medical and Surgical) | T (Urinary System) | B (Excision) | Renal biopsy to confirm CKD staging histologically — e.g., 0TB03ZX (Excision of Right Kidney, Percutaneous, Diagnostic) |
| B (Imaging) | T (Urinary System) | 5 (Ultrasonography) | Renal ultrasound to assess kidney size and structural damage — e.g., BT453ZZ (Ultrasonography of Bilateral Kidneys) |
| 4 (Measurement and Monitoring) | A (Physiological Systems) | 1 (Monitoring) | Urinary output and pressure monitoring during inpatient stay — e.g., 4A1D70Z (Monitoring of Urinary Pressure, Via Natural/Artificial Opening) |
💊 Coding Scenarios and Examples
Scenario 1 — Outpatient / Nephrology: Hypertensive CKD Stage 2, Established Patient Follow-Up
Clinical Vignette: A 62-year-old female with a documented 8-year history of hypertension presents to nephrology follow-up. Lab results show an eGFR of 72 mL/min/1.73 m² (stable over the past 6 months) and a UACR of 68 mg/g on repeat testing. The nephrologist documents: “Hypertensive chronic kidney disease, Stage 2 — mild GFR reduction, microalbuminuria. Continue lisinopril, low-sodium diet counseling provided. Recheck labs and UACR in 3 months.” Moderate MDM documented supporting a level 4 E/M.
CPT (Profee):
- 99214 — Office visit, established patient, moderate MDM (management of hypertensive CKD Stage 2 with data review, independent interpretation of labs, and medication management)
ICD-10-CM Primary Diagnosis:
- I12.9 — Hypertensive chronic kidney disease with stage 1-2 CKD or unspecified CKD (Code First per category N18 instruction)
ICD-10-CM Secondary Diagnoses:
- N18.2 — Chronic kidney disease, stage 2 (required per I12.- “Use Additional Code” instruction to specify the CKD stage)
Scenario 2 — Inpatient: Hypertensive Urgency with CKD Stage 2 as Comorbidity
Clinical Vignette: A 70-year-old male is admitted for hypertensive urgency (BP 210/118 mmHg) requiring IV labetalol titration. Past medical history includes hypertensive CKD documented at Stage 2 (eGFR 74, UACR 55 mg/g confirmed on prior outpatient labs). No acute change in renal function is noted during admission; BMP on admission shows creatinine at baseline. CKD Stage 2 is documented by the attending in the H&P as an active comorbidity.
Principal Diagnosis:
- I10 — Essential (primary) hypertension (Reason for admission — acute hypertensive urgency requiring IV management)
Secondary Diagnoses:
- I12.9 — Hypertensive chronic kidney disease with stage 1-2 CKD (documented comorbidity; sequence as secondary per Code First hierarchy)
- N18.2 — Chronic kidney disease, stage 2 (required additional code per “Use Additional Code” instruction with I12.-)
MS-DRG Assignment: The principal diagnosis of hypertension groups to MDC 05 (Diseases and Disorders of the Circulatory System). N18.2 is neither a CC nor MCC and does not affect DRG assignment. If heart failure or AKI were superimposed, those codes would function as CCs or MCCs and shift the DRG. A CDI query should be sent if eGFR dipped during the admission to confirm whether AKI on CKD should also be coded (N17.x).
Scenario 3 — CDI Query: CKD Documented Without Stage, eGFR in Stage 2 Range
Clinical Vignette: A 65-year-old male with Type 2 diabetes and hypertension is admitted for uncontrolled hyperglycemia. The H&P includes the problem list entry “chronic kidney disease” and a BMP showing eGFR of 77 mL/min/1.73 m² with a prior outpatient UACR of 95 mg/g. The coder notes the eGFR value and prior albuminuria documentation but finds no provider documentation confirming “Stage 2.” The attending’s note reads only “CKD — continue monitoring.”
Action / Outcome: The coder cannot assign N18.2 without explicit provider confirmation of the stage. A CDI query should be generated presenting the eGFR value (77) and UACR (95 mg/g) and asking the provider to confirm the diagnosis and stage of chronic kidney disease and identify the primary etiology (diabetic vs. hypertensive vs. combined). Without this query, the only defensible code is N18.9 (CKD, unspecified) — a less specific code that carries no HCC weight and represents an undercoding risk.
Query Response: Attending updates the assessment: “Type 2 diabetes mellitus with diabetic chronic kidney disease, Stage 2 — eGFR 77, confirmed microalbuminuria on two prior outpatient measurements. CKD is attributable to longstanding T2DM and hypertension; diabetes is the primary driver.”
Corrected ICD-10-CM Coding:
- E11.22 — Type 2 diabetes mellitus with diabetic chronic kidney disease, stage 2 (Code First per category N18 instruction — DM confirmed as primary cause)
- N18.2 — Chronic kidney disease, stage 2 (required additional code per E11.22 tabular instruction)
- I10 — Essential (primary) hypertension (code separately; hypertension documented as contributing factor)
⚠️ Coding Pitfalls and Tips
| Pitfall or Tip | |
|---|---|
| ❌ | Sequencing N18.2 Before the Causative Code. When CKD is caused by hypertension or diabetes, those combination codes (I12.-, I13.-, or E08.22-E13.22) must be sequenced first. Submitting N18.2 as the first-listed or principal diagnosis in the presence of a documented causative condition is a “Code First” sequencing violation that can trigger claim denial and audit exposure. |
| ❌ | Using N18.9 When Stage 2 Is Documented. If the provider has explicitly documented “CKD, Stage 2” anywhere in the record, N18.9 (unspecified) is incorrect and constitutes undercoding. N18.9 also carries no HCC weight, and while N18.2 itself doesn’t either, accurate staging is essential for longitudinal compliance and future progression capture. |
| ❌ | Inferring CKD Stage From Lab Values Alone. An eGFR of 60-89 with microalbuminuria does not automatically allow a coder to assign N18.2 — the provider must document the CKD diagnosis and stage. Send a CDI query if only lab values are present without a confirmed provider diagnosis per ICD-10-CM Official Guidelines. |
| ✅ | Always Append N18.2 After I12.-, I13.-, or DM Combination Codes. The “Use Additional Code” instruction at I12.-, I13.-, and the DM combination codes requires the coder to add N18.2 — it is not optional. Missing this secondary code creates incomplete staging documentation and disrupts longitudinal CKD tracking. |
| ✅ | Send a CDI Query When CKD Is Documented Without a Stage. Any chart showing “CKD” without a stage, especially with eGFR values in the 60-89 range and albuminuria, is a CDI query opportunity. Resolving vague CKD documentation to a specific stage supports accurate HCC tracking, DRG accuracy, and quality reporting. |
| ✅ | Code AKI and CKD Stage 2 Simultaneously When Both Present. Per ICD-10-CM guidelines, AKI (N17.x) and CKD (N18.2) may and should both be reported when AKI is superimposed on CKD. AKI typically sequences as the higher-acuity principal or secondary diagnosis, and the pairing is clinically significant for DRG weight and patient complexity capture. |