2026 ICD-10-CM Diagnosis Code L03.31ACellulitis of flank

ICD-10-CM Codes›L00–L99›L00-L08›L03

ICD-10-CM L03.31A
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

L03.31A is a billable ICD-10-CM diagnosis code for cellulitis of flank. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 573 through 575, 602 through 603, 791, 793. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 68 closely related codes.

Code Identity

ICD-10-CM Code
L03.31A
Billable Status
Yes — Valid for Submission
Code Describes
Cellulitis of flank
Short Description
Cellulitis of flank
Same as the full description in the CMS dataset.
Parent Code
L03.31
Cellulitis of trunk

Code Classification

ChapterL00–L99Diseases of the skin and subcutaneous tissue
SectionL00-L08Infections of the skin and subcutaneous tissue
CategoryL03Cellulitis and acute lymphangitis
This CodeL03.31ACellulitis of flank

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Code History & ChangesHistory

New Code L03.31A was added to the ICD-10-CM code set for FY 2026, effective October 1, 2025.

Replacement L03.31A replaces the following previously assigned code(s):

  • L03.312 - Cellulitis of back [any part except buttock]
FY 2026AddedAdded to the ICD-10-CM code setEffective October 1, 2025.
FY 2026CurrentRevised in the current code setEffective October 1, 2025 through September 30, 2026.

Questions About L03.31AOverview

What is the ICD-10 code for cellulitis of flank?

The ICD-10-CM code for cellulitis of flank is L03.31A (sometimes written as L0331A). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is L03.31A (Cellulitis of trunk) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report cellulitis of flank on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does L03.31A group to?

When cellulitis of flank is the principal diagnosis on an inpatient stay, it groups to MS-DRG 573, 574, 575, 602, 603, 791, 793, with relative weights from 0.8709 to 6.5514 depending on complications. Higher weights mean higher Medicare reimbursement.

Is L03.31A a CC or MCC?

CMS lists L03.31A as a CC (complication or comorbidity) for FY 2026. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 68 closely related codes in its exclusion list.