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ICD-10-CM 2027 diagnosis code

L03.31ACellulitis of flank

✓ Billable / specificCC — complication/comorbidity

L03.31A is a valid, billable ICD-10-CM code for cellulitis of flank. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.

Code last changed in FY2026 (effective October 1, 2025). Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About L03.31A

L03.31A is the ICD-10-CM diagnosis code for cellulitis of flank. It belongs to category L03 (cellulitis and acute lymphangitis), block L00-L08 (infections of the skin and subcutaneous tissue) and chapter 12 (diseases of the skin and subcutaneous tissue). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within L03.31 (cellulitis of trunk), L03.31A is specifically for cellulitis of flank. Related codes cover abdominal wall (L03.311), back [any part except buttock and flank] (L03.312), chest wall (L03.313), groin (L03.314), perineum (L03.315), umbilicus (L03.316), buttock (L03.317) and unspecified (L03.319).

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 573 (Skin Graft for Skin Ulcer or Cellulitis with MCC, relative weight 6.3575), DRG 574 (Skin Graft for Skin Ulcer or Cellulitis with CC, relative weight 3.5674), DRG 575 (Skin Graft for Skin Ulcer or Cellulitis without CC/MCC, relative weight 1.8797), DRG 602 (Cellulitis with MCC, relative weight 1.4273), DRG 603 (Cellulitis without MCC, relative weight 0.8635), DRG 791 (Prematurity with Major Problems, relative weight 4.1075) and 1 more, in MDC 09 (Diseases and Disorders of the Skin, Subcutaneous Tissue and Breast) and MDC 15 (Newborns and Other Neonates with Conditions Originating in the Perinatal Period), 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 was added in FY2026, effective October 1, 2025.

Notes that apply from higher levels

Instructions written at a parent level also apply to L03.31A.

› From L03.31 Cellulitis of trunk
Excludes2
  • cellulitis of anal and rectal regions (K61.-)
  • cellulitis of breast NOS (N61.0)
  • cellulitis of female external genital organs (N76.4)
  • cellulitis of male external genital organs (N48.2, N49.-)
  • omphalitis of newborn (P38.-)
  • puerperal cellulitis of breast (O91.2)
› From L03 Cellulitis and acute lymphangitis
Excludes2
  • cellulitis of anal and rectal region (K61.-)
  • cellulitis of external auditory canal (H60.1)
  • cellulitis of eyelid (H00.0)
  • cellulitis of female external genital organs (N76.4)
  • cellulitis of lacrimal apparatus (H04.3)
  • cellulitis of male external genital organs (N48.2, N49.-)
  • cellulitis of mouth (K12.2)
  • cellulitis of nose (J34.0)
  • eosinophilic cellulitis [Wells] (L98.3)
  • febrile neutrophilic dermatosis [Sweet] (L98.2)
  • lymphangitis (chronic) (subacute) (I89.1)

Broader instructions also apply from L00-L08 Infections of the skin and subcutaneous tissue and Chapter 12: Diseases of the skin and subcutaneous tissue.

Alphabetic index entries

1 entries

Terms in the official ICD-10-CM index that lead to L03.31A.

MS-DRG v44.0 grouping

All DRGs →

Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.

MDC 09 · Diseases and Disorders of the Skin, Subcutaneous Tissue and Breast

MDC 15 · Newborns and Other Neonates with Conditions Originating in the Perinatal Period

MDC 15 · Newborns and Other Neonates with Conditions Originating in the Perinatal Period

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2026 (effective 10/1/2025): Added
  • No changes since FY2026.

Common questions about L03.31A

Is L03.31A billable?

Yes. L03.31A is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can L03.31A be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict L03.31A as a principal diagnosis.

Is L03.31A a CC or MCC?

L03.31A is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.

What DRG does L03.31A group to?

L03.31A is used in the MS-DRG v44.0 logic for MS-DRG 573 (Skin Graft for Skin Ulcer or Cellulitis with MCC), MS-DRG 574 (Skin Graft for Skin Ulcer or Cellulitis with CC), MS-DRG 575 (Skin Graft for Skin Ulcer or Cellulitis without CC/MCC), MS-DRG 602 (Cellulitis with MCC), MS-DRG 603 (Cellulitis without MCC), MS-DRG 791 (Prematurity with Major Problems) and 1 more. Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.