ICD code S31.644D – Puncture wound with foreign body of abdominal wall

Key takeaways

ICD-10 code S31.644D covers a puncture wound of the abdominal wall with a foreign body, left lower quadrant, with peritoneal penetration, subsequent encounter.

S31.644 is the non-billable parent code. Only the three 7th-character codes bill: S31.644A, S31.644D and S31.644S.

The 6th character 4 means left lower quadrant. The S31.6 subcategory is what signals penetration into the peritoneal cavity.

S31.644D is not a new code. It has been valid since ICD-10-CM took effect on October 1, 2015, and it stays active in FY2026.

Documentation must confirm the puncture mechanism, the foreign body, the left lower quadrant site, peritoneal penetration, and that active treatment has ended.

ICD-10 code S31.644D: Definition, billability, and effective date

S31.644D is a valid, billable ICD-10-CM diagnosis code. It carries all seven characters the code set requires, so payers accept it for reimbursement without a further qualifier. It is the American ICD-10-CM version of the code. The Centers for Medicare and Medicaid Services and the National Center for Health Statistics maintain the code set jointly.

The full official description is: Puncture wound with foreign body of abdominal wall, left lower quadrant with penetration into peritoneal cavity, subsequent encounter. Every word carries a clinical and a billing implication, and the next section breaks each one down.

On the effective date, one point is worth stating plainly. S31.644D is not a recent addition to ICD-10-CM. It was part of the original code set that took effect on October 1, 2015, and it has carried the same description ever since. The FY2026 edition, which governs encounters from October 1, 2025 through September 30, 2026, leaves it unchanged. You can confirm the current status in the CDC/NCHS ICD-10-CM web tool.

Full code description and clinical meaning

Each component of the S31.644D description has a distinct clinical meaning. Each one also has to be verifiable in the patient record before the code is assigned. The table below breaks down every descriptor and the documentation it requires.

In practice the code shows up most often in outpatient surgical follow-up. The acute episode is over by then, and the wound is being monitored rather than treated.

What does D mean in S31.644D?

The 7th character D means subsequent encounter. On injury codes, that character reports the phase of care, not the severity of the wound. Getting it wrong is a common reason trauma and wound-care claims are denied.

A key distinction: subsequent encounter does not mean a second hospital admission for the same injury. It means the active treatment phase is over and the patient is receiving routine healing care. A patient can move from A to D inside the same week. All it takes is for the surgery or closure to be complete and the next visit to be monitoring.

When sequela applies instead: use S31.644S only once the patient develops a new condition caused directly by the original injury. A post-operative adhesion or a scar contracture would qualify. The sequela character attaches to that resulting condition. It does not describe ongoing care of the wound itself.

The S31.644 family: Parent and sibling codes

S31.644 is the non-billable parent code. It groups the encounter-type variants for a puncture wound of the abdominal wall with a foreign body, left lower quadrant, with peritoneal penetration. It cannot be submitted on its own, because ICD-10-CM requires a 7th character here. Coders pick one of the three billable children below.

The 6th character carries the site. S31.64 gives you ten to choose from:

• 0 — right upper quadrant
• 1 — left upper quadrant
• 2 — epigastric region
• 3 — right lower quadrant
• 4 — left lower quadrant
• 5 — periumbilic region
• 6 — right flank
• 7 — left flank
• 9 — unspecified quadrant
• A — unspecified flank

Left lower quadrant is always 4. It is never A, which is the placeholder for a flank wound with no documented side.

Code hierarchy for S31.644D

Knowing where S31.644D sits in the tabular list makes navigation faster. It also shows which adjacent code to reach for when the record does not support the most specific level.

The AAPC ICD-10-CM lookup tool lets you walk this hierarchy interactively and check the codes either side of the one you have chosen.

Two codes that get mistaken for S31.644D

Two lookalike codes are the usual source of error on this wound. Each one changes part of the description while staying a valid ICD-10-CM code. That is why a claim scrubber will not flag either of them.

S31.144D swaps the depth. Its description is identical apart from four words: without penetration into peritoneal cavity. The S31.1 subcategory covers abdominal wall wounds that stopped short of the peritoneum. S31.6 covers the wounds that went through it.

So the depth is decided by the digit after the decimal point, before you ever reach the site character. If your operative note or CT report confirms a peritoneal breach, the code has to start S31.6.

S31.14AD swaps both the depth and the site. It reads: puncture wound of abdominal wall with foreign body, unspecified flank without penetration into peritoneal cavity, subsequent encounter.

The A in that code is a 6th character, and it means unspecified flank, not left lower quadrant. Submitting S31.14AD for an LLQ wound with peritoneal penetration understates the injury on two axes at once.

Both errors come down to two characters sitting in different places. The diagram below shows which part of S31.644D fixes the depth and which one fixes the site.

Documentation requirements at a follow-up visit

Denials on S31.644D usually trace back to notes that are clinically accurate but incomplete for coding. A clinician can observe the peritoneal breach without recording the words a coder needs to cite. That distance between the note and the code is where revenue leaks. Work through this checklist before the encounter is closed.

1. Confirm the wound mechanism. The note has to say puncture or stab wound. Wound on its own does not separate a puncture from a laceration or a bite, and each maps to a different subcategory.
2. Name the foreign body. Specify the object type, such as a glass fragment, a metal shard or a wood splinter. Many payers treat foreign body with no description as unsupported. Also record whether it was removed or remains in situ.
3. Specify the anatomical quadrant. Left lower quadrant or LLQ has to appear. Periumbilical, left flank and lower abdomen are separate 6th characters, not synonyms.
4. Evidence the peritoneal penetration. Cite the source: an operative or procedure note, a CT report describing intraperitoneal air or fluid, or an attending attestation. Clinical suspicion on its own does not support the S31.6 subcategory.
5. Establish the encounter context. Show that initial treatment was completed earlier. Give the date of that visit, or reference the inpatient discharge summary.
6. Select the 7th character last. D is right only once active treatment has ended. If the wound is still being debrided or irrigated, the encounter is still A.

Practice management software like Pabau submits claims through the Claim.MD clearinghouse, which reaches thousands of US payers. Complete documentation at the code level is still the most reliable route to a clean claim on the first pass.

Finish the note before the encounter closes. A late addendum that introduces a new clinical finding after the claim went out carries audit risk.

Excludes notes and common coding pitfalls

Excludes notes in ICD-10-CM are binding instructions that block incorrect code combinations. Ignoring one is the fastest route to a medical necessity denial or an audit finding. These are the notes and restrictions that apply to S31.644D.

• Excludes1, so never coded together: traumatic amputation of part of the abdomen, lower back and pelvis (S38.2-, S38.3). Where an amputation is documented, the open wound code is subsumed into it.
• Excludes2, so coded separately if present: open wound of hip (S71.00-S71.02) and open fracture of pelvis (S32.1- to S32.9 with 7th character B).
• Code also: any associated spinal cord injury and any wound infection. Both are reported with their own codes alongside S31.644D.
• Never pair two 7th characters for one visit: S31.644A and S31.644D are mutually exclusive. A visit is initial or subsequent, never both.
• Drop to S31.1 when the peritoneum held: if the record confirms only abdominal wall injury, the correct family is S31.14 rather than S31.64. For an LLQ follow-up, that is S31.144D.
• Do not default to unspecified: S31.649D exists for an undocumented quadrant. Reaching for it when the note says LLQ breaches the ICD-10-CM specificity rules.

The recurring coder mistakes on this family are worth naming too:

• Carrying 7th character A through every wound-related visit, whether or not initial treatment has finished.
• Coding from the chief complaint without opening the operative note to confirm the peritoneal breach.
• Reaching for the S31.1 series out of habit, because it appears first in the tabular list.
• Leaving the 7th character unchanged across an episode. A third post-operative wound check billed with A will usually trip a payer edit.

Our guide to claim denial codes shows which reason codes tend to accompany specificity errors on open wound diagnoses. An excludes violation that surfaces after submission is worth appealing differently from a standard underpayment dispute.

Approximate synonyms and alternate clinical descriptions

EHR search fields and note templates often use wording that differs from the official description. The phrases below map to S31.644D for documentation matching. Searching any of them in the ICD List free lookup tool usually returns S31.644D or one of its siblings.

• Puncture wound of the left lower abdominal quadrant with a foreign object, penetrating the peritoneum, follow-up visit
• Stab wound, LLQ abdominal wall, retained foreign body, intraperitoneal penetration, subsequent encounter
• Penetrating abdominal wound with foreign body, left lower quadrant, peritoneal cavity involved, routine follow-up
• Open wound of the left iliac region with foreign body and peritoneal penetration, subsequent care
• Foreign body puncture wound, left lower abdomen, intraperitoneal extension, post-acute encounter

When you write free-text notes, stay as close to the official ICD-10-CM wording as the clinical picture allows. That reduces the chance of an auto-coding tool settling on a less specific code. It also keeps the diagnosis clean for the claims management software that submits it.

How Pabau supports abdominal wound coding and documentation

A penetrating abdominal wound generates a long tail of encounters. The operative note lives with the initial visit, and the imaging that confirmed the breach sits somewhere else. The wound checks then arrive weeks after both. Coders assigning S31.644D at visit four often have to request the original chart just to confirm the depth and the quadrant.

Pabau keeps the S31.644A encounter, every S31.644D follow-up, and any later sequela visit inside one patient record. A coder can open the wound check and read the operative note behind it without leaving the chart. Pabau’s claims management also catches a six-character parent code submitted without its 7th character, before the claim leaves the practice.

The result is fewer denials tied to encounter-type mismatches, and faster coding when the provider who treated the original wound has moved on.

Manage wound care follow-ups and billing in one system

Pabau links clinical documentation to claims submission through Claim.MD. A subsequent-encounter visit like an S31.644D wound check is then coded from the original operative note, not from memory.

Book a demo

Conclusion

A puncture wound that reaches the peritoneal cavity produces several follow-up encounters, and each one needs the right 7th character to be paid. S31.644D is the code for those visits, but only where the record confirms the foreign body, the left lower quadrant site, and the peritoneal breach.

Miss the breach and you are in the S31.1 series. Miss the quadrant and you are on an unspecified code that invites a specificity denial.

Pabau’s Claim.MD partnership gives practices a direct path from the clinical note to an electronic claim. That reaches thousands of US payers. Coding accurately at the source means fewer denials and fewer retrospective addenda. To see how Pabau handles trauma and surgical follow-up documentation, book a demo.

Continue your research

Need a framework for managing claim denials on injury codes? Denial codes in medical billing explains the most common reason codes and how to respond to each.

Want to understand how clearinghouses process ICD-10 claims? Medical claims clearinghouse guide covers how claims flow from practice to payer and where ICD-10 specificity errors are caught.

Looking for guidance on ERA and remittance reconciliation for wound care claims? Electronic remittance advice (ERA) explains how to read 835 files and identify denial patterns by diagnosis code.

Frequently asked questions