K51.313 Ulcerative (chronic) rectosigmoiditis with fistula

Billable ICD-10-CM code, FY2026. Acts as a Complication or Comorbidity (CC) as a secondary diagnosis.

Applies from K51 Ulcerative colitis

Excludes1 (never code together)

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

Use additional code

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

Risk adjustment (HCC)

• CMS-HCC V28: HCC 81 — Ulcerative Colitis
• CMS-HCC V22: HCC 35 — Inflammatory Bowel Disease
• RxHCC V08: HCC 67 — Inflammatory Bowel Disease
• ESRD V24: HCC 35

MS-DRG index

Defines the logic of DRG(s) 385-387 in MDC 06.

Approximate ICD-9-CM (GEMs)

• 556.3 Ulcerative (chronic) proctosigmoiditis (approximate)
• 569.81 Fistula of intestine, excluding rectum and anus (approximate)

Code annotations containing back-references to K51.313

Back-references to K51.313

• Type 1 Excludes: K63.2 Fistula of intestine ("fistula of intestine with ulcerative colitis (K51.013, K51.213, K51.313, K51.413, K51.513, K51.813, K51.913)")

Back-references to K51

• Code First: F54 Psychological and behavioral factors associated with disorders or diseases classified elsewhere ("ulcerative colitis (K51.-)")
• Type 1 Excludes: K50 Crohn's disease [regional enteritis] ("ulcerative colitis (K51.-)")
• Code First: K60.3 Anal fistula ("ulcerative colitis (K51.-)")
• Code First: K60.4 Rectal fistula ("ulcerative colitis (K51.-)")
• Code First: K60.5 Anorectal fistula ("ulcerative colitis (K51.-)")
• Type 1 Excludes: K62.6 Ulcer of anus and rectum ("ulcerative colitis (K51.-)")
• Type 1 Excludes: K63.3 Ulcer of intestine ("ulcerative colitis (K51.-)")
• Code Also: M07 Enteropathic arthropathies ("ulcerative colitis (K51.-)")
• Code Also: M08 Juvenile arthritis ("ulcerative colitis (K51.-)")

Diagnosis Index entries for K51.313

• Rectosigmoiditis › ulcerative (chronic) › with › complication › fistula

Nearby codes

• K51.3 Ulcerative (chronic) rectosigmoiditis
• K51.30 Ulcerative (chronic) rectosigmoiditis without complications
• K51.31 Ulcerative (chronic) rectosigmoiditis with complications
• K51.311 Ulcerative (chronic) rectosigmoiditis with rectal bleeding
• K51.312 Ulcerative (chronic) rectosigmoiditis with intestinal obstruction
• K51.313 Ulcerative (chronic) rectosigmoiditis with fistula (this code)
• K51.314 Ulcerative (chronic) rectosigmoiditis with abscess
• K51.318 Ulcerative (chronic) rectosigmoiditis with other complication
• K51.319 Ulcerative (chronic) rectosigmoiditis with unspecified complications
• K51.4 Inflammatory polyps of colon
• K51.40 Inflammatory polyps of colon without complications