S31.65AA — Open bite of abdominal wall, unspecified flank with penetration into peritoneal cavity, initial encounter
Is S31.65AA billable?
Yes, but S31.65AA will trip a Medicare edit. S31.65AA is a valid, billable ICD-10-CM code for encounters from October 1, 2026 through September 30, 2027. However, CMS lists S31.65AA under Medicare Code Editor edit 20, “Unspecified code” — meaning a code specifying laterality (right, left or bilateral) exists in the same family. On an inpatient claim this triggers the edit, because CMS holds that there are very limited circumstances in which laterality cannot be documented.
More specific alternatives
- S31.650AOpen bite of abdominal wall, right upper quadrant with penetration into peritoneal cavity, initial encounter
- S31.651AOpen bite of abdominal wall, left upper quadrant with penetration into peritoneal cavity, initial encounter
- S31.652AOpen bite of abdominal wall, epigastric region with penetration into peritoneal cavity, initial encounter
- S31.653AOpen bite of abdominal wall, right lower quadrant with penetration into peritoneal cavity, initial encounter
- S31.654AOpen bite of abdominal wall, left lower quadrant with penetration into peritoneal cavity, initial encounter
- S31.655AOpen bite of abdominal wall, periumbilic region with penetration into peritoneal cavity, initial encounter
- S31.656AOpen bite of abdominal wall, right flank with penetration into peritoneal cavity, initial encounter
- S31.657AOpen bite of abdominal wall, left flank with penetration into peritoneal cavity, initial encounter
S31.65AA at a glance
| Code | S31.65AA |
|---|---|
| Description | Open bite of abdominal wall, unspecified flank with penetration into peritoneal cavity, initial encounter |
| Billable | Yes |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
| 7th character "A" | initial encounter |
What does the 7th character "A" mean in S31.65AA?
In S31.65AA, the 7th character A means initial encounter. The 7th character is required for S31.65AA to be a valid, complete code.
Same condition, different episode of care — switch the 7th character:
What Medicare edits apply to S31.65AA?
The Medicare Code Editor screens inpatient claims before they are grouped. These edits name S31.65AA directly.
A code specifying laterality (right, left or bilateral) exists in the same family. CMS holds that there are very limited circumstances in which laterality cannot be documented.
Which MS-DRGs does S31.65AA group to?
S31.65AA sits in MDC 06 and helps define the logic of 3 MS-DRGs (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.
- 393Other Digestive System Diagnoses with MCCmedical
- 394Other Digestive System Diagnoses with CCmedical
- 395Other Digestive System Diagnoses without CC/MCCmedical
As a secondary diagnosis, S31.65AA is a major complication or comorbidity (MCC), which can move a stay into a higher-paying DRG.
How is S31.65AA listed in the Alphabetic Index?
The Alphabetic Index lists these routes under S31.65A, the nearest indexed parent of S31.65AA. Use them to find the family, then select the specific code.
- Bite › flank › with penetration into peritoneal cavity (s) (animal) (human)
Inclusion terms
Alternative wording in documentation that is classified to S31.65AA.
- Open bite of abdominal wall, flank NOS, with penetration into peritoneal cavity
Excludes1 — never code together — inherited from S31
The conditions below can never be reported together with S31.65AA on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.
Excludes1 — never code together — inherited from S31.65
The conditions below can never be reported together with S31.65AA on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.
Use additional code — inherited from Chapter 19
Report an additional code alongside S31.65AA to fully describe the condition. S31.65AA is sequenced first.
- code to identify any retained foreign body, if applicable (Z18.-)
Excludes2 — not included here — inherited from Chapter 19
The conditions below are not part of S31.65AA, but a patient may have both at the same time. When documentation supports it, S31.65AA and the excluded code may both be reported.
Excludes2 — not included here — inherited from S30-S39
The conditions below are not part of S31.65AA, but a patient may have both at the same time. When documentation supports it, S31.65AA and the excluded code may both be reported.
Excludes2 — not included here — inherited from S31
The conditions below are not part of S31.65AA, but a patient may have both at the same time. When documentation supports it, S31.65AA and the excluded code may both be reported.
Code also — inherited from S31
Two codes may be needed to describe the condition fully. Whether S31.65AA is sequenced first depends on the reason for the encounter.
How long has S31.65AA existed?
S31.65AA first appears in FY2026.
Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.