ICD code S21.141S – Open thoracic wall wound with foreign body, sequela

Key takeaways

S21.141S is the billable ICD-10-CM code for the sequela of a right front chest wall puncture wound with foreign body, without thoracic cavity penetration.

The seventh character ‘S’ applies only after the original wound has healed. Assigning it during active treatment can draw a payer query.

A companion code for the sequela condition (e.g. chronic chest wall pain, scarring, foreign body granuloma) is listed first, with S21.141S second.

If the wound entered the thoracic cavity, the correct sequela code is S21.341S, not S21.141S.

Pabau’s claims management software supports ICD-10-CM code submission and integrates with Claim.MD for US claim clearinghouse processing.

ICD-10 Code S21.141S: Definition and clinical description

ICD-10 Code S21.141S has the official descriptor “Puncture wound with foreign body of right front wall of thorax without penetration into thoracic cavity, sequela.” Each element of that descriptor must be supported by documentation before the code can be reported.

• Puncture wound: a narrow, deep wound made by a pointed object, as opposed to a laceration or a surgical incision.
• With foreign body: an object such as a glass shard, splinter, nail or metal fragment entered the wound. It may have been removed since, or it may still be embedded.
• Right front wall of thorax: the right side of the anterior chest wall. That covers the skin, subcutaneous tissue and muscle over the anterior ribs and sternum.
• Without penetration into thoracic cavity: the wound stayed within the chest wall. It did not enter the pleural space or the mediastinum.
• Sequela: the patient is presenting for a late effect of the healed injury, not for the wound itself.

If the original wound did enter the thoracic cavity, S21.141S is the wrong code. The penetrating equivalent is S21.341S, which sits in subcategory S21.3 rather than S21.1.

Every element must appear in both the original injury record and the current encounter note. Missing even one pushes the code toward a less specific alternative in the S21 category, which affects coding accuracy and reimbursement.

Code structure and category breakdown

S21.141S sits in ICD-10-CM Chapter 19 (S00–T88, Injury, poisoning and certain other consequences of external causes). Breaking the code down character by character shows which clinical element each position encodes.

The sixth character carries laterality. S21.141S specifies the right anterior chest wall, and a left-side wound takes S21.142S instead. Confirm the side in the original injury record before reporting.

Understanding the seventh character ‘S’ — sequela

The seventh character “S” denotes a sequela encounter. The original injury has healed, and the patient now presents for a condition that exists as a direct result of it. This is distinct from active treatment (seventh character “A”) and routine healing follow-up (seventh character “D”).

Section I.B.10 of the ICD-10-CM Official Guidelines for Coding and Reporting covers sequela coding. It defines a sequela as the residual effect left once the acute phase of an injury has ended. It also sets the order: the sequela condition is coded first, and the injury code with “S” is sequenced second. Section I.C.19.a confirms that “S” is for complications or conditions arising as a direct result of an injury.

One sequela coding mistake to check for is assigning “S” while the wound is still under active treatment. If the record still references wound care, debridement or open-wound management, use “A.” Assign “S” only when the documentation states the wound has resolved.

Clinical scenario: When to use S21.141S for a healed chest wall puncture wound

S21.141S applies when a patient with a healed, non-penetrating puncture wound of the right anterior chest wall returns for a condition caused by that injury. The foreign body may have been removed at the time, or it may still sit in the chest wall soft tissue.

Common late-effect presentations that warrant this code:

• Chronic chest wall pain localized to the healed puncture site, with no open wound present.
• Scarring or fibrosis at the entry site that is tender, tethered or restricts movement of the chest or shoulder.
• Retained foreign body effects, such as a foreign body granuloma or recurring inflammation around a fragment left in the subcutaneous tissue.
• Delayed removal of a retained fragment once the wound has healed and the fragment starts causing symptoms.

Here is a worked example. Eight months after a glass shard punctured the right anterior chest wall, a patient reports a firm, painful nodule at the healed site. Imaging shows a small fragment in the subcutaneous tissue and no intrathoracic involvement.

The clinician documents a foreign body granuloma as a sequela of the injury. The coder reports L92.3 (foreign body granuloma of the skin and subcutaneous tissue) first, then S21.141S. Z18.81 (retained glass fragments) identifies the fragment still in place.

In every case, sequence the condition being treated today first and S21.141S second. The current condition drives the first-listed diagnosis, and S21.141S explains its origin.

Documentation requirements for S21.141S

Documentation decides whether a sequela claim holds up. For clean claim submission, the current encounter note must establish five specific elements:

1. Confirmed prior injury: explicit reference to a previous puncture wound of the right front chest wall, with the date or approximate timeframe of the injury.
2. Healed wound status: documentation that the original wound has closed and the active healing phase is complete. This is the trigger for the “S” seventh character.
3. Foreign body involvement: confirmation that a foreign body entered the wound, and whether it was removed or remains in situ.
4. No thoracic cavity penetration: confirmation that the wound did NOT penetrate the thoracic cavity and stayed within the chest wall soft tissue. If the record shows penetration, code S21.341S instead.
5. Causal link: an explicit statement by the treating clinician that connects the current condition to the prior chest wall injury.

If any of these five elements is absent, the coder should query the clinician before assigning S21.141S. Submitting without that support can draw a payer query or a request for records.

Codes commonly confused with S21.141S

Several codes in the S21 category share most of the S21.141S descriptor but differ on one element. Picking the wrong one is a coding specificity error.

Two assignment errors are worth checking for. One is using S21.141S when the correct encounter type is “A” or “D.” The other is reaching for S21.101S when the record supports the full specificity of S21.141S.

The costliest mix-up is between subcategories S21.1 and S21.3. A wound that entered the pleural space or mediastinum belongs in S21.34-, so confirm penetration status before choosing. The four checks below run in the order a coder should apply them.

Excludes notes, inclusions, and code also instructions

S21.141S inherits instructional notes from category S21 and from the S20–S29 block. Review each level in the current tabular list before assigning the code.

• Code also at category S21: any associated injury, reported in addition to the wound code. Examples include rib fracture (S22.3-, S22.4-), injury of intrathoracic organs (S27.-) and wound infection. Traumatic hemothorax (S27.1), hemopneumothorax (S27.2) and pneumothorax (S27.0) are listed too.
• Excludes1 at category S21: traumatic amputation (partial) of thorax (S28.1). No separate Excludes1 note appears at the S21.141S code level, but the category note still applies.
• Excludes2 at block S20–S29: burns and corrosions, frostbite, and injuries of the shoulder and clavicle region. Effects of a foreign body in the bronchus, esophagus, lung or trachea are excluded as well.
• Retained foreign body: Chapter 19 instructs coders to add a Z18.- code to identify any retained foreign body, where applicable.
• Sequela companion code: report an additional code for the condition treated at this encounter. Examples include R07.89 (other chest pain), L90.5 (scar conditions and fibrosis of skin) and L92.3 (foreign body granuloma of skin and subcutaneous tissue). M54.6 (pain in thoracic spine) fits only when the pain is spinal.
• Sequencing: per Section I.B.10, the sequela condition is listed first and S21.141S second, unless a payer instruction for the encounter specifically requires otherwise.

The Z18 retained foreign body codes deserve particular attention. If the foreign body is documented as still present at the current encounter, a Z18.- code adds precision and supports any related removal procedure.

External cause codes need the same S ending

When a practice reports external cause codes, Section I.C.20 asks for the same seventh character as the injury code. For a glass injury at the sequela stage, that means W25.XXXS (contact with sharp glass, sequela) alongside S21.141S.

Place of occurrence (Y92) and activity (Y93) codes work differently. They are reported once, at the initial encounter, so they do not return on a sequela claim. There is no national mandate for external cause reporting, but some states and payers require it.

Payer requirements and billing guidelines for S21.141S

S21.141S is a valid billable code in the FY2027 ICD-10-CM code set, effective October 1, 2026. Confirm it against the CMS ICD-10-CM coding files each year. Submitting it correctly depends on code sequencing, companion codes and payer-specific documentation expectations.

Key payer requirements:

• Companion code required: a sequela code is not listed first. Report the late-effect condition first, with S21.141S second to explain the causal injury. Some claim edits flag a sequela injury code that arrives without a condition code.
• Medicare and Medicaid: these payers follow the ICD-10-CM Official Guidelines. If a claim is reviewed, the record must support the sequela determination.
• Commercial payers: coverage policies vary by carrier. Check whether prior authorization applies if the sequela visit includes a procedure, such as foreign body removal or scar revision.
• MS-DRG mapping: on inpatient claims, DRG assignment depends on the principal diagnosis and any procedures reported. Verify against the CMS MS-DRG v44 Definitions Manual for FY2027, since groupings and weights update annually.

Practices using claims management software with built-in ICD-10 validation can catch a missing companion code before submission. Pabau, the practice management platform we build, sends electronic claims through Claim.MD, its US clearinghouse partner. Claim.MD processes CMS-1500 claims across thousands of US payers and returns eligibility checks and ERA remittances. Building medical billing compliance into the claim itself costs less than appealing a denial later.

Common claim denial reasons for S21.141S

A sequela claim depends on a chain of causation that the record has to show. The patterns below are the likeliest reasons an S21.141S claim stalls, and each maps to a step in denial management in healthcare:

1. Wrong seventh character: using “S” when the wound is still in active treatment. If the encounter note includes wound care, debridement or irrigation, the correct character is “A,” not “S.”
2. Missing companion code: submitting S21.141S on its own, with no code for the sequela condition. Many payer claim edits will reject or query this.
3. Insufficient causal documentation: the note does not connect today’s condition to the prior chest wall injury. “History of chest wound” alone is not enough; the note should state the condition is “a sequela of” the injury.
4. Penetration mismatch: reporting S21.141S when the record shows the wound entered the thoracic cavity. That wound belongs under S21.341S.
5. Laterality error: using S21.141S (right side) when the original wound was on the left, where S21.142S applies.
6. Specificity downgrade: reporting S21.101S (unspecified) when documentation supports S21.141S, which can prompt a request for more documentation.
7. No healed-wound documentation: the active healing phase must be documented as complete before “S” applies. Without a record of wound closure, the note cannot link the injury to the sequela determination.

Reviewing the denial codes returned on S21.141S claims shows which of these patterns applies in a specific practice. CARC reason codes on the 835 remittance indicate whether the denial is a specificity issue, a missing code or a documentation deficiency.

ICD-10-CM code history and annual updates

S21.141S took effect with the US implementation of ICD-10-CM on October 1, 2015. It remains a billable code, with the same descriptor, in the FY2027 code set that took effect on October 1, 2026.

To verify current validity, coders can cross-reference the code against the CDC/NCHS ICD-10-CM web tool, which is updated each October. The AAPC Codify ICD-10-CM lookup and Check ICD-10 are commercial tools that mirror the official CMS and NCHS data.

Understanding medical billing fundamentals, including the annual update cycle, helps coders avoid submitting a revised or deleted code. Check the current tabular list at the start of each fiscal year, as the S21 category can gain specificity when the code set is updated.

How Pabau keeps the injury history in one record

Coding S21.141S correctly depends on facts recorded months apart. The coder needs the original wound type, the foreign body, the side, the penetration status and the date the wound healed. In many practices those details sit in separate notes, scanned letters and old claims.

Pabau keeps clinical notes, past diagnoses and claims on one patient record. A coder reviewing a sequela visit can open the original injury note next to today’s encounter.

Code validation and Claim.MD submission then flag a missing companion code before the claim goes out. Your team then spends less time rebuilding the injury story after a denial.

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Pabau integrates scheduling, clinical notes and billing in one system, so coders and clinicians have the documentation they need before a claim is submitted.

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Conclusion

S21.141S rests on one distinction above the others. The puncture stayed in the chest wall and never entered the thoracic cavity. When the record cannot show that, query the clinician before coding, because S21.341S may be the correct code.

Once penetration status is settled, the rest is a short sequence. Confirm the right side and the healed wound, then list the late-effect condition ahead of S21.141S. To see how Pabau handles ICD-10-CM claim submission end to end, book a demo with the team.

Continue your research

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