N18.9 Does Not Map in V28. Stage 3a N18.31 Is HCC 329. Stage 3b N18.32 Is HCC 328.

If you searched N18.9, CKD unspecified, or chronic kidney disease next to HCC or V28, you are looking at one of the most common renal leftovers under CMS-HCC V28 for payment year 2026. N18.9 (Chronic kidney disease, unspecified) is billable. On the live FY2026 card it has no payable CMS-HCC V28 mapping. Look up the N18.9 card.

Do not confuse N18.9 with N18.30 (Chronic kidney disease, stage 3 unspecified). N18.30 does map to V28 HCC 329. Unspecified CKD (N18.9) and stage 3 unspecified (N18.30) are different codes with different payment results.

The stage-specific CKD codes that pay under community V28 in this desk are stage 3a, stage 3b, stage 4, stage 5, and ESRD. N18.31 (stage 3a) maps to V28 HCC 329 (Chronic Kidney Disease, Moderate (Stage 3, Except 3B)) with a source-labeled community non-dual aged (CNA) reference of 0.127. N18.32 (stage 3b) maps to V28 HCC 328 (Chronic Kidney Disease, Moderate (Stage 3B)) with the same source-labeled CNA 0.127. Same coefficient does not mean the same category: HCC 328 supersedes HCC 329 in hierarchy when both apply. N18.4 (stage 4) maps to V28 HCC 327 with CNA 0.514. N18.5 (stage 5) and N18.6 (ESRD) map to V28 HCC 326 with CNA 0.815.

This page is the leftover-style N18.9 CKD map desk for that leak. It is not a rewrite of the CKD coding guide, the I10 hypertensive leftover desk, or the E11.22 diabetes with CKD desk. Cross-link those when hypertensive CKD or diabetic CKD documentation is also in play.

Desk table: verified maps and no-maps (2026-09-24)

Coefficients are source-labeled CNA references from the live cards and the HCC 329 / HCC 328 / HCC 327 / HCC 326 hubs. Not member totals. Hierarchy still applies: HCC 329 is superseded by HCC 326, 327, and 328 when a more severe category in the same disease group is also present. HCC 328 is superseded by HCC 326 and 327. HCC 327 is superseded by HCC 326.

What N18.9 is (and is not)

N18.9 is Chronic kidney disease, unspecified. It is the catch-all when the provider documents CKD without a stage. It is billable. Billable does not mean risk-adjusted under PY2026 community V28.

Do not treat N18.9 as if it mapped like stage 3a or stage 3b. Do not invent N18.31 or N18.32 from an unspecified CKD label alone. Query when the chart supports a staged CKD diagnosis.

N18.1 (stage 1) and N18.2 (stage 2) are more specific early-stage codes. They still show no payable V28 mapping on the live cards and have no PY2026 V28 CSV rows. Specificity inside early CKD does not create HCC 329.

N18.30 is not N18.9

This is the trap that burns desks. N18.30 is Chronic kidney disease, stage 3 unspecified. It has a PY2026 V28 row (`N1830,329.0,,,`) and maps to HCC 329. N18.9 is CKD with no stage documented. It has no V28 row.

If the provider documents stage 3 without a or b, N18.30 is the code that matches that documentation and it pays under V28 as HCC 329. If the provider only documents "CKD" or "chronic kidney disease" with no stage, N18.9 is correct and it does not pay under V28. Do not auto-upgrade N18.9 to N18.30 to create RAF.

When stage documentation changes the map

If the provider documents CKD stage 3a, use N18.31. That maps to HCC 329 (CNA 0.127).

If the provider documents CKD stage 3b, use N18.32. That maps to HCC 328 (CNA 0.127). Same CNA as 329, different category. HCC 328 supersedes 329 in hierarchy.

If the provider documents CKD stage 3 without a or b, use N18.30. That also maps to HCC 329. Prefer 3a or 3b when the chart supports the split.

If the provider documents CKD stage 4, use N18.4. That maps to HCC 327 (CNA 0.514).

If the provider documents CKD stage 5, use N18.5. That maps to HCC 326 (CNA 0.815).

If the provider documents end stage renal disease, use N18.6. That also maps to HCC 326.

Z99.2 (Dependence on renal dialysis) is billable with no payable CMS-HCC V28 mapping on the live card. Dialysis dependence status does not replace a mapped ESRD or stage 5 code. Code Z99.2 when the status is documented, and code the CKD/ESRD diagnosis that the chart supports. Do not invent N18.6 from a Z99.2 row alone.

Providers document the stage. Coders code what is documented. Do not invent a stage from an eGFR value alone without following the applicable coding, clinical, and program rules for your setting. When the chart has lab context and the provider has not staged CKD, query for the stage rather than guessing N18.31 or N18.32. This desk does not invent Coding Clinic advice.

Pick the path from the documentation:

1. Chart says CKD / chronic kidney disease with no stage -> expect N18.9, no V28 payment map.

2. Chart supports CKD stage 1 or stage 2 -> N18.1 / N18.2, no V28 payment map.

3. Chart supports CKD stage 3 without a/b -> N18.30 -> HCC 329.

4. Chart supports CKD stage 3a -> N18.31 -> HCC 329.

5. Chart supports CKD stage 3b -> N18.32 -> HCC 328.

6. Chart supports CKD stage 4 -> N18.4 -> HCC 327.

7. Chart supports CKD stage 5 -> N18.5 -> HCC 326.

8. Chart supports ESRD -> N18.6 -> HCC 326.

9. Chart supports dialysis dependence as a status -> Z99.2 (no V28 map) plus the CKD/ESRD code that matches the diagnosis documentation.

10. Do not invent stage 3a/3b/4/5 or ESRD for RAF from an N18.9-only note. Query when findings support a staged diagnosis.

Hypertensive CKD and diabetic CKD often travel with these codes. When the chart supports hypertensive heart and CKD or type 2 diabetes with diabetic CKD, walk those desks separately: the I10 hypertensive leftover desk and the E11.22 diabetes with CKD desk. Do not collapse them into this N18.9 leftover.

MEAT for mapped CKD HCCs

A mapped code still needs monitoring, evaluation, assessment, or treatment in the eligible encounter year. A problem-list row that says "CKD" from last year does not carry HCC 329, 328, 327, or 326 forward by itself.

For N18.30 / N18.31 (HCC 329), N18.32 (HCC 328), N18.4 (HCC 327), and N18.5 / N18.6 (HCC 326), the note should support:

MEAT is a review mnemonic, not a universal CMS coding rule. Follow the applicable coding, encounter, program, and payer requirements. See MEAT and problem lists.

Audit and query traps

1. Leaving supported stage 3a CKD on N18.9 because "CKD is CKD." Unspecified does not create HCC 329.

2. Confusing N18.9 (no map) with N18.30 (HCC 329). Stage 3 unspecified pays. CKD unspecified does not.

3. Treating stage 1 (N18.1) or stage 2 (N18.2) as if they mapped like stage 3a. Neither maps under V28.

4. Inventing N18.31 or N18.32 from an eGFR printout alone without provider stage documentation. Query when the chart supports a stage.

5. Coding N18.31 (HCC 329) when the chart clearly supports stage 3b (N18.32, HCC 328), or the reverse. Prefer the documented a/b split.

6. Ignoring hierarchy: when HCC 326, 327, or 328 also applies in the same disease group, HCC 329 can be superseded. When 326 or 327 also applies, HCC 328 can be superseded.

7. Treating Z99.2 (dialysis dependence) as if it created HCC 326. Live card: no payable V28 map. Pair it with the documented ESRD/stage 5 code when supported.

8. Skipping MEAT for a historical CKD label with no current assessment or treatment in the eligible year.

9. Mixing this N18.9 leftover into the full CKD coding guide. Cross-link; keep the leftover walk here.

10. Rewriting the I10 hypertensive leftover or E11.22 diabetes CKD desks into this post. Cross-link those.

11. Inventing V24 payment maps for current-year non-PACE scoring. Select the historical period on the live card when you need V24 context.

12. Assuming same CNA means same HCC. N18.31 and N18.32 both show CNA 0.127 on the hubs, but they map to HCC 329 and HCC 328 respectively, and hierarchy still separates them.

Two-minute check

1. Open the live N18.9 card. Confirm Not mapped / verified no payable CMS-HCC V28 mapping.

2. Confirm N18.30 and N18.31 -> HCC 329 (CNA 0.127). Do not confuse N18.30 with N18.9.

3. Confirm N18.32 -> HCC 328 (CNA 0.127).

4. Confirm N18.4 -> HCC 327 (CNA 0.514); N18.5 / N18.6 -> HCC 326 (CNA 0.815).

5. Confirm MEAT in the eligible encounter year for any mapped code you report.

6. Do not invent staged CKD from an N18.9-only note. Query when documentation supports a stage.

Sources and related desks