2026 ICD-10-CM Diagnosis Code S31.10AAUnspecified open wound of abdominal wall, unspecified flank without penetration into peritoneal cavity, initial encounter

ICD-10-CM Codes›S00–T88›S30-S39›S31

ICD-10-CM S31.10AA
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

S31.10AA is a billable ICD-10-CM diagnosis code for unspecified open wound of abdominal wall, unspecified flank without penetration into peritoneal cavity, initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 604 through 605, 963 through 965.

Code Identity

ICD-10-CM Code
S31.10AA
Billable Status
Yes — Valid for Submission
Code Describes
Unspecified open wound of abdominal wall, unspecified flank without penetration into peritoneal cavity, initial encounter
Short Description
Unsp opn wnd abd wall, unsp flank w/o penet perit cav, init
Parent Code
S31.10A
Unspecified open wound of abdominal wall, unspecified flank without penetration into peritoneal cavity

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionS30-S39Injuries to the abdomen, lower back, lumbar spine, pelvis and external genitals
CategoryS31Open wound of abdomen, lower back, pelvis and external genitals
This CodeS31.10AAUnspecified open wound of abdominal wall, unspecified flank without penetration into peritoneal cavity, initial encounter

Coding GuidelinesGuidance

The appropriate 7th character is to be added to each code from block Open wound of abdomen, lower back, pelvis and external genitals (S31). Use the following options for the applicable episode of care:

  • A - initial encounter
  • D - subsequent encounter
  • S - sequela

Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2026, published by CMS and the National Center for Health Statistics.

Code History & ChangesHistory

New Code S31.10AA was added to the ICD-10-CM code set for FY 2026, effective October 1, 2025.

Replacement S31.10AA replaces the following previously assigned code(s):

  • S31.109A - Unsp opn wnd abd wall, unsp q w/o penet perit cav, init
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 S31.10AAOverview

Is S31.10AA a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report unspecified open wound of abdominal wall, unspecified flank without penetration into peritoneal cavity, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What does the 7th character A in S31.10AA mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for unspecified open wound of abdominal wall, unspecified flank without penetration into peritoneal cavity, such as an emergency visit or first evaluation.

What MS-DRG does S31.10AA group to?

When unspecified open wound of abdominal wall, unspecified flank without penetration into peritoneal cavity, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 604, 605, 963, 964, 965, with relative weights from 0.9160 to 2.7338 depending on complications. Higher weights mean higher Medicare reimbursement.