ICD-10 Code L03.31A – Cellulitis of flank (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code L03.31A – Cellulitis of flank
What it is
L03.31A identifies cellulitis affecting the flank, the side of the trunk between the ribs and hip. Use it when documentation states cellulitis in this specific body area.
Clinical signs
Typical findings include localized redness, warmth, swelling, and tenderness of the flank. Clinical features vary; refer to documentation for whether the infection is superficial, spreading, or associated with abscess.
When to use this code
Use this code when the provider documents cellulitis of the flank or an infection of the flank skin and subcutaneous tissue. It is appropriate when the site is clearly the flank, not the abdomen, back, or hip. If the record is unclear, check documentation before coding.
Do not use for
Do not use this code for cellulitis in another body site, generalized skin infection, or a deeper soft tissue infection. Do not assume flank cellulitis from nonspecific trunk documentation.
Coding tip
Verify the anatomic site in the note and code the most specific location documented.