K51.9Ulcerative colitis, unspecified

K51.9 is the ICD-10-CM diagnosis code for ulcerative colitis, unspecified. It belongs to category K51 (ulcerative colitis), block K50-K52 (noninfective enteritis and colitis) and chapter 11 (diseases of the digestive system). It is a header code, so it can't be reported by itself; one of its 2 subcodes must be used instead.

Within K51, choose K51.9 (unspecified) only when documentation doesn't support a more specific option: ulcerative (chronic) pancolitis (K51.0), ulcerative (chronic) proctitis (K51.2), ulcerative (chronic) rectosigmoiditis (K51.3), inflammatory polyps of colon (K51.4), left sided colitis (K51.5) and other ulcerative colitis (K51.8).

To report this condition, pick the subcode that matches the documentation: K51.90 (without complications) and K51.91 (with complications).

Use an additional code to identify any associated fistulas, if applicable: anal fistula (K60.3-), anorectal fistula (K60.5-) and rectal fistula (K60.4-). Use an additional code to identify manifestations, such as: pyoderma gangrenosum (L88).

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.