2026 ICD-10-CM Diagnosis Code S31.001AUnspecified open wound of lower back and pelvis with penetration into retroperitoneum, initial encounter
S31.001A is a billable ICD-10-CM diagnosis code for unspecified open wound of lower back and pelvis with penetration into retroperitoneum, 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 698 through 700, 963 through 965. Coders also document this condition as open dislocation of lumbar vertebra. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Open wounds of trunk, initial encounter.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Open dislocation of lumbar vertebra
- Open division lumbosacral ligament
- Open spinal dislocation with anterior lumbar cord lesion
- Open spinal dislocation with complete lumbar cord lesion
- Posterior cord syndrome of lumbar spinal cord
- Posterior cord syndrome of lumbar spinal cord due to open dislocation of lumbar spine
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.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Wounds and Injuries
An injury is damage to your body. It is a general term that refers to harm caused by accidents, falls, hits, weapons, and more. In the U.S., millions of people injure themselves every year. These injuries range from minor to life-threatening.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert S31.001A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About S31.001AOverview
Is S31.001A a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report unspecified open wound of lower back and pelvis with penetration into retroperitoneum, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in S31.001A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for unspecified open wound of lower back and pelvis with penetration into retroperitoneum, such as an emergency visit or first evaluation.
What MS-DRG does S31.001A group to?
When unspecified open wound of lower back and pelvis with penetration into retroperitoneum, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 698, 699, 700, 963, 964, 965, with relative weights from 0.6899 to 2.7338 depending on complications. Higher weights mean higher Medicare reimbursement.
What is the ICD-9 equivalent of S31.001A?
Under the General Equivalence Mappings, unspecified open wound of lower back and pelvis with penetration into retroperitoneum, initial encounter converts to ICD-9-CM 868.14 (retroperitoneum inj-open). The mapping is approximate, so confirm the match fits the documentation.
Footnotes
[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.
