Is K51.21 a billable ICD-10-CM code?

No. K51.21 is a non-billable header code. Code to a higher level of specificity using one of its child codes.

Where does K51.21 sit in the tabular list?

Diseases of the digestive system (K00-K95), in the block Noninfective enteritis and colitis (K50-K52).

What cannot be coded together with K51.21?

K51.21 carries Excludes1 notes, which means the conditions they list can never be coded together with it on the same encounter. Some are written on the categories above K51.21 (K51) and apply to it just the same.

K51.21

K51.21 — Ulcerative (chronic) proctitis with complications

Non-billable headerICD-10-CM

K51.21 is a non-billable header ICD-10-CM code for ulcerative (chronic) proctitis with complications. It cannot be billed on its own: choose one of the more specific child codes below.

Excludes1 inherited from the categories above K51.21

These are not written on K51.21, but they bind it: a note on a category applies to every code beneath it. Billing K51.21 with anything listed here is a denial.

Written on K51 — Ulcerative colitis

Crohn's disease [regional enteritis] (K50.-)

Other codes that can never be billed with K51.21

These codes carry an Excludes1 note pointing at K51.21. The conflict binds both ways, but ICD-10-CM only writes it down on one side — so you would not find this by reading K51.21 alone.

K62.6Ulcer of anus and rectum
K63.0Abscess of intestine
K63.2Fistula of intestine
K63.3Ulcer of intestine
K50Crohn's disease [regional enteritis]

Risk adjustment

K51.21 does not map to an HCC and does not risk-adjust under CMS-HCC V28. That is normal — most ICD-10 codes do not. It still needs to be coded correctly; it just will not move a RAF score.

Code history

K51.21 has not changed since FY2024 — no addition, revision or deletion across the three most recent ICD-10-CM releases.

Code to one of these instead K51.21

6 child codes. Green means billable.

Related codes at this level

Codes that share K51.2. If K51.21 is not quite right, the correct code is usually one of these.

K51.20Ulcerative (chronic) proctitis without complications

Questions about K51.21

Is K51.21 a billable ICD-10-CM code?: No. K51.21 is a non-billable header code. Code to a higher level of specificity using one of its child codes.
Where does K51.21 sit in the tabular list?: Diseases of the digestive system (K00-K95), in the block Noninfective enteritis and colitis (K50-K52).
What cannot be coded together with K51.21?: K51.21 carries Excludes1 notes, which means the conditions they list can never be coded together with it on the same encounter. Some are written on the categories above K51.21 (K51) and apply to it just the same.