ICD-10 Code K51.5 – Left Sided Colitis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code K51.5 – Left sided colitis
What it is
K51.5 identifies left sided colitis, a form of ulcerative colitis that affects the colon from the rectum through the left side of the large intestine. Use it when documentation clearly states this distribution.
Clinical signs
Typical findings include chronic or recurrent bloody diarrhea, abdominal pain, urgency, and rectal bleeding. Clinical features vary; refer to documentation, especially endoscopic or pathology reports describing left-sided involvement.
When to use this code
Use K51.5 when the provider documents ulcerative colitis limited to the left colon, including the rectum, sigmoid, and descending colon. It also fits when colonoscopy or imaging supports left-sided disease and the diagnosis is recorded that way. If the extent is unclear, check documentation before coding.
Do not use for
Do not use this code for ulcerative colitis limited to the rectum, pancolitis, or Crohn disease. Check documentation when the record only says “colitis” without specifying left-sided involvement.
Coding tip
Match the code to the documented anatomic extent, not just the word “ulcerative colitis.”