ICD-10 code K67: Disorders of peritoneum in infectious diseases

Key Takeaways

ICD-10 code K67 is a single, billable ICD-10-CM diagnosis code covering disorders of peritoneum in infectious diseases classified elsewhere, valid for FY2026 (effective October 1, 2025). It has no decimal subcodes.

K67 is a manifestation code that only pairs with two etiologies: congenital syphilis (A50.0) or helminthiasis (B65.0-B83.9). Sequence that etiology code first, then add K67 as the secondary diagnosis.

Chlamydial, gonococcal, late syphilitic, and tuberculous peritonitis are Excludes1 to K67. They each have their own combination code (A74.81, A54.85, A52.74, A18.31) and must never be reported alongside K67.

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ICD-10 code K67 is a single, billable ICD-10-CM diagnosis code for disorders of peritoneum in infectious diseases classified elsewhere. It has no decimal subcodes, even though many reference sources still list K67.0 through K67.8, subcodes carried over from the World Health Organization’s global ICD-10 that don’t exist in the US ICD-10-CM.

Notably, several peritonitis types that look like natural K67 cases have their own combination code instead. In short, this reference covers K67’s code-first rule, the Excludes1 codes that must never be paired with it, recordkeeping requirements, and how K67 differs from adjacent peritoneum codes K65, K66, and K68.

Currently, the FY2026 ICD-10-CM code set is in effect as of October 1, 2025, the same annual update cycle that revised codes like T86.892. Meanwhile, K67 remains valid through September 30, 2026 and is accepted for payment submission by Medicare, Medicaid, and most commercial payers when correctly sequenced with its code-first etiology.

ICD-10 code K67: Definition, billable status, and code details

Specifically, K67 is assigned when a patient has peritoneal involvement that is a direct consequence of congenital syphilis or a helminth (parasitic worm) infection. In fact, these are the only two conditions ICD-10-CM names in its code-first note for this code.

Here, the peritoneal disorder is the manifestation, and the etiology, A50.0 or the applicable B65-B83 code, must be sequenced first on the claim. K67 itself has no decimal subcodes, so every case is reported with the same three-character code.

In practice, congenital syphilis is usually caught through prenatal screening or diagnosed in sexual health practices, while helminthiasis more often surfaces in general practice after travel-related parasitic exposure.

K67 code details at a glance

According to the CMS ICD-10 codes page, K67 falls within the diseases of the digestive system chapter but is driven by an infectious process coded elsewhere. Because of this cross-chapter link, correct sequencing matters. In fact, several infections that look like natural K67 cases are excluded from it instead.

K67’s code-first and Excludes1 codes: How they differ

K67 is not divided into subcodes for specific infectious agents. Namely, that decimal structure covers K67.0 chlamydial, K67.1 gonococcal, K67.2 syphilitic, K67.3 tuberculous, and K67.8 other. Instead, it belongs to the World Health Organization’s global ICD-10, not the US ICD-10-CM used for billing. However, some older reference pages and coding tools carry the WHO structure over by mistake.

In ICD-10-CM, K67 is a single, standalone code with two very different sets of related codes: a short code-first list and a longer Excludes1 list. In fact, confusing the two is the most common K67 sequencing error.

Put simply, an Excludes1 note means “not coded here”: the excluded code and K67 can never appear together on the same claim, because the excluded code is already the complete, standalone diagnosis.

If a patient has tuberculous, chlamydial, gonococcal, or late syphilitic peritonitis, don’t reach for K67 at all. Bill the single combination code instead. In other words, that’s the opposite convention from the code-first pairing above.

ICD-10-CM coding guidelines for ICD-10 code K67: Manifestation sequencing rules

Formally, K67 is classified as a manifestation code under the ICD-10-CM Official Guidelines for Coding and Reporting. Indeed, the CDC/NCHS ICD-10-CM official tool confirms K67 carries a “code first” instruction for congenital syphilis (A50.0) and helminthiasis (B65.0-B83.9) only, meaning one of those two etiology codes must always appear before K67 on the claim when it applies.

Importantly, reversing the order, or using K67 without either etiology code present, gets the principal diagnosis wrong and can trigger a payer audit.

The same etiology-manifestation sequencing convention shows up elsewhere in ICD-10-CM. For example, G30.1 requires its own secondary code in a similar way. For K67, the structure is simply: A50.0 or a B65-B83 helminthiasis code first, K67 second, and nothing else.

How to sequence K67: Step-by-step coding workflow

1. First, confirm the documented underlying condition is congenital syphilis or a helminth (parasitic worm) infection. Indeed, these are the only two etiologies K67 pairs with.
2. Next, locate the etiology code, A50.0 for congenital syphilis, or the specific B65-B83 code for the documented parasite (e.g. B65.1 for intestinal schistosomiasis).
3. Then, confirm peritoneal involvement is clearly documented as a consequence of that etiology.
4. After that, sequence the etiology code first. In other words, A50.0 or the applicable B65-B83 code is the principal or first-listed diagnosis.
5. Now, add K67 as the secondary diagnosis. Remember, K67 has no subcodes, so it’s reported at the three-character level regardless of the underlying organism.
6. Finally, stop before adding K67 to an Excludes1 diagnosis. If the documented infection is chlamydial, gonococcal, late syphilitic, or tuberculous peritonitis instead, don’t use K67 at all. Instead, report the single combination code (A74.81, A54.85, A52.74, or A18.31) by itself.

This sequence reflects the required ICD-10-CM code-first convention, but it applies only to the two etiologies above. Submitting K67 without one of those paired etiology codes present will result in claim rejection, and submitting K67 alongside A74.81, A54.85, A52.74, or A18.31 is an Excludes1 conflict, not a valid code pair.

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K67 recordkeeping requirements for billing and payment

Overall, poor records are the leading reason K67 claims fail on review. In fact, payers require the clinical record to support both the etiology code and the K67 manifestation code separately.

For instance, a general infectious disease diagnosis without a clear peritoneal involvement note will not support K67 on appeal. Likewise, a documented diagnosis of chlamydial, gonococcal, late syphilitic, or tuberculous peritonitis will support a different, standalone code, not K67.

What the clinical note must include

For this reason, good medical recordkeeping and clinical recordkeeping compliance both depend on complete, specific physician notes that tie the peritoneal findings to the underlying infection.

• Confirmed etiology diagnosis: The physician note must document one of the two conditions that trigger K67 (e.g. “early congenital syphilis with peritoneal involvement” or “intestinal schistosomiasis with peritoneal extension”). By contrast, a note that documents tuberculous, chlamydial, or gonococcal peritonitis points to a different, standalone combination code, not K67.
• Peritoneal involvement clearly stated: A generic reference to “abdominal symptoms” isn’t enough. Instead, the note must use specific language: “peritonitis,” “peritoneal involvement,” or “peritoneal inflammation secondary to [infectious disease].”
• Causal linkage between infection and peritoneal disorder: The provider must establish that the peritoneal condition is caused by the infectious disease, not just a coincidence. For example, phrases like “peritonitis due to,” “secondary to,” or “as a complication of” support the coding linkage.
• How the diagnosis was confirmed: Document the method used (culture, serology, imaging, biopsy). After all, coders cannot add detail that isn’t in the record.
• Code pairing in the record: The clinical note should reflect both diagnoses so the coder can assign them without querying the provider. To support this, use digital clinical forms with structured fields to confirm the infection and record the peritoneal findings.

Recordkeeping and compliance requirements

In addition, supporting HIPAA compliance in billing workflows means retaining complete records for the required audit retention period. Beyond that, the clinical record management system should capture and archive the full encounter note, not just the billed codes.

K67 vs adjacent peritoneum codes: K65, K66, and K68

The K65-K68 code block covers all disorders of the peritoneum and retroperitoneum. Selecting the wrong code from this block is one of the most common peritoneal coding errors. Namely, the key difference for K67 is that the peritoneal disorder is a manifestation of congenital syphilis or helminthiasis only. However, other infectious peritonitis types have their own codes instead of K67.

The decision tree is simple. First, code the etiology; then add K67 as the second code, whenever the peritoneal disorder is a manifestation of congenital syphilis or helminthiasis.

If the peritonitis is chlamydial, gonococcal, late syphilitic, or tuberculous, use the single combination code (A74.81, A54.85, A52.74, or A18.31) alone. In other words, these are Excludes1 to K67, not code-first pairings.

K65 applies when the peritonitis is primary or caused by a local event such as bowel perforation or a surgical complication. In contrast, K68 applies when the condition affects the retroperitoneum rather than the peritoneum.

Common clinical scenarios for ICD-10 code K67

These coding vignettes illustrate K67’s two coding patterns: the code-first pairing it requires, and the Excludes1 codes it’s often confused with.

Code-first pairing scenarios

• Scenario 1 (code-first pairing): Patient with confirmed intestinal schistosomiasis and imaging showing peritoneal thickening and ascites, documented as a consequence of the parasitic infection. Correct code sequence: B65.1 (Schistosomiasis due to Schistosoma mansoni) as principal diagnosis, K67 as secondary. Again, K67 cannot be sequenced first.
• Scenario 2 (code-first pairing): Infant with early congenital syphilis and peritoneal involvement documented by the treating physician. Correct sequence: A50.0 (Early congenital syphilis, symptomatic) as principal diagnosis, K67 as secondary.

Excludes1 scenarios

• Scenario 3 (Excludes1, not a K67 pairing): Patient with active pulmonary tuberculosis presenting with ascites and peritoneal thickening on imaging, documented as tuberculous peritonitis. Correct code: A18.31 (Tuberculous peritonitis) reported alone. Here, K67 is not added. Peritonitis in tuberculosis is Excludes1 to K67, and A18.31 is already the complete diagnosis.
• Scenario 4 (Excludes1, not a K67 pairing): Patient with confirmed disseminated gonococcal infection and peritonitis documented as a complication, with features consistent with Fitz-Hugh-Curtis syndrome. Correct code: A54.85 (Gonococcal peritonitis) reported alone. Again, K67 is never added alongside A54.85. Excludes1 codes replace K67 instead of pairing with it.

In scenarios 1 and 2, the AAPC ICD-10-CM code lookup confirms the code-first pairing rule. Meanwhile, in scenarios 3 and 4, the same source confirms the Excludes1 relationship. In short, K67 is never billed alongside those combination codes.

What’s captured in the encounter record drives which pattern applies. As a result, coders cannot assign K67 without one of its two valid etiology codes present, and cannot add it to a claim that already carries an Excludes1 code.

Overall, using claims management software that validates code pairs, and flags Excludes1 conflicts at submission, reduces the risk of denials from either error.

K67 code history and ICD-10-CM category context

K67 sits within Chapter XI (Diseases of the digestive system, K00-K95) of ICD-10-CM, in the K65-K68 block that covers diseases of the peritoneum and retroperitoneum.

The code is maintained by the WHO ICD-10 classification system at the global level and adapted by the National Center for Health Statistics (NCHS) and CMS for use as ICD-10-CM in the United States. In doing so, that adaptation dropped the WHO version’s K67.0-K67.8 decimal subcodes. As a result, in ICD-10-CM, K67 stands alone.

The ICD-10 code structure places K67 after K65 (peritonitis) and K66 (other peritoneal disorders) and before K68 (retroperitoneal disorders). In turn, this hierarchy reflects the anatomical and etiological groupings used by the coding system.

In practice, the tabular list framework works the same way across ICD-10-CM. For example, the same structure is used in our guide to O71.9. A “code first” instruction reflects a manifestation-etiology relationship that must be preserved in sequencing, while an “Excludes1” instruction means the two codes must never be reported together.

In this way, practices can use practice management software to build these ICD-10 code-pair rules into their clinical recordkeeping workflows, reducing the risk of sequencing errors at the point of note completion.

Continue your research

Coding a different manifestation-etiology pair? Our guide to M34.9 covers its billable status, Excludes1 rule, and recordkeeping requirements.

Working through another combination code? Our guide to N85.3 covers billable status and the records payers expect.

Need a refresher on a different ICD-10-CM code? Our guide to T31.85 breaks down billable status and recordkeeping requirements.

Conclusion

You can avoid K67 sequencing errors once you know K67 has no subcodes and pairs with just two etiologies. Code first is non-negotiable, but only for congenital syphilis (A50.0) and helminthiasis (B65.0-B83.9). Simply put, sequence the etiology first, K67 second, and make sure the clinical note clearly links both.

Just as important: chlamydial, gonococcal, late syphilitic, and tuberculous peritonitis are Excludes1 to K67 and use their own codes (A74.81, A54.85, A52.74, A18.31) instead. Again, never pair any of those with K67. As a result, practices that build both rules into their coding workflow catch errors before submission rather than after a denial.

Pabau’s claims management tools support ICD-10-CM code pair entry and claim validation, helping gastroenterology and infectious disease practices submit K67 encounters correctly the first time. To see how Pabau handles complex diagnosis code workflows, book a demo.

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