K51.313Ulcerative (chronic) rectosigmoiditis with fistula

K51.313 is the ICD-10-CM diagnosis code for ulcerative (chronic) rectosigmoiditis with fistula. It belongs to category K51 (ulcerative colitis), block K50-K52 (noninfective enteritis and colitis) and chapter 11 (diseases of the digestive system). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within K51.31 (ulcerative (chronic) rectosigmoiditis with complications), K51.313 is specifically for ulcerative (chronic) rectosigmoiditis with fistula. Related codes cover rectal bleeding (K51.311), intestinal obstruction (K51.312), abscess (K51.314), other complication (K51.318) and unspecified complications (K51.319).

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).

As a secondary diagnosis it is a CC (complication or comorbidity), which can move an inpatient stay into the "with CC" MS-DRG of its family, unless the principal diagnosis excludes it.

In MS-DRG v44.0, it is part of the grouping logic for DRG 385 (Inflammatory Bowel Disease with MCC, relative weight 1.5543), DRG 386 (Inflammatory Bowel Disease with CC, relative weight 0.9647) and DRG 387 (Inflammatory Bowel Disease without CC/MCC, relative weight 0.6464), in MDC 06 (Diseases and Disorders of the Digestive System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

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

Before ICD-10, this condition was coded in ICD-9-CM as 556.3 (ulcerative (chronic) proctosigmoiditis) and 569.81 (fistula of intestine, excluding rectum and anus).