ICD-10 code T86.31: Heart-lung transplant rejection

Key Takeaways

T86.31 is a billable ICD-10-CM code for heart-lung transplant rejection, valid for claims with a date of service on or after October 1, 2015

Rejection type matters: acute, chronic, and hyperacute rejection all fall under T86.31, but clinical documentation must specify the rejection mechanism to support the diagnosis

T86.31 sits within the T86.3 subcategory and must not be confused with T86.32 (failure) or T86.33 (infection), each of which describes a distinct complication requiring separate coding

Pabau’s claims management software supports ICD-10-CM code entry and documentation workflows for transplant follow-up billing

Transplant rejection claims are among the most scrutinized in post-surgical billing. When a patient presents with signs of heart-lung graft rejection, coders and transplant coordinators must document the correct complication code precisely or face claim denials, audit flags, and delayed reimbursement. ICD-10 code T86.31 is the specific, billable designation for heart-lung transplant rejection under the ICD-10-CM classification system, maintained by the Centers for Medicare and Medicaid Services (CMS) and the National Center for Health Statistics (NCHS).

This reference guide covers T86.31’s billable status, clinical context, sequencing rules, adjacent codes within the T86.3 subcategory, and documentation requirements for transplant teams billing follow-up care.

ICD-10 code T86.31: Definition and billable status

Heart-lung transplant rejection occurs when the recipient’s immune system identifies the transplanted organ as foreign and mounts a response against it. This rejection can affect either the cardiac or pulmonary component of the graft, or both simultaneously. The ICD-10-CM code T86.31 captures this complication at the highest level of specificity available within the T86.3 subcategory.

T86.31 is a fully billable diagnosis code. It has been valid for reimbursement claims with a date of service on or after October 1, 2015, aligning with the United States’ transition to ICD-10-CM. The ICD List diagnostic code database confirms T86.31 as billable for FY2026, with no restrictions on the patient encounter type.

Billing teams using claims management software should map T86.31 at the encounter level rather than defaulting to the parent code T86.3, which is non-billable and will trigger a claim rejection.

The code sits within the broader ICD-10-CM chapter structure as follows: Chapter 19 (Injury, poisoning and certain other consequences of external causes) > Section T80-T88 (Complications of surgical and medical care) > T86 (Complications of transplanted organs and tissue) > T86.3 (Complications of heart-lung transplant) > T86.31 (Heart-lung transplant rejection).

Approximate synonyms and clinical terminology

Clinical documentation may use several equivalent terms that map to T86.31:

• Heart-lung allograft rejection
• Combined cardiopulmonary transplant rejection
• Graft rejection following heart-lung transplantation
• Immune-mediated rejection, heart-lung transplant

All of these are clinically acceptable documentation terms. Any of them in a physician’s note supports assignment of T86.31, provided they clearly indicate rejection rather than failure or infection.

Rejection types and clinical presentation under T86.31

A single ICD-10-CM code covers all three immunological rejection subtypes. The distinction matters clinically because each type drives a different therapeutic approach, but T86.31 does not differentiate between them in the coding hierarchy. Documentation should clarify the rejection type to support clinical decision-making even when the code remains the same.

Acute rejection

Acute rejection typically occurs within the first year post-transplant. Diagnosis involves endomyocardial biopsy for cardiac rejection and transbronchial biopsy for pulmonary rejection. Pathology reports from either procedure provide the documentation basis for T86.31 assignment.

Chronic rejection

Chronic rejection develops over months to years. In heart-lung recipients, it manifests as cardiac allograft vasculopathy on the cardiac side and bronchiolitis obliterans syndrome on the pulmonary side. Both remain coded under T86.31 when rejection is the confirmed mechanism.

Hyperacute rejection

Hyperacute rejection occurs within minutes to hours of transplant. It is antibody-mediated and typically identified in the surgical or immediate post-operative setting. This is the least common subtype in modern transplantation due to pre-transplant crossmatch protocols, but it still codes to T86.31 when documented.

For a comparison of how ICD-10-CM handles diagnosis coding across complex clinical scenarios, see our guide to ICD-10 coding for cerebrovascular diagnoses.

T86.31 vs T86.32 vs T86.33: Choosing the right code

The most consequential coding distinction within the T86.3 subcategory is between rejection (T86.31), failure (T86.32), and infection (T86.33). Miscoding between these three is a common source of claim denials and audit flags. Each describes a mechanistically different complication requiring different clinical management and, from a payer’s perspective, different clinical justification.

When a patient presents with both rejection and infection simultaneously, coders may assign both T86.31 and T86.33. The principal diagnosis should reflect the condition primarily responsible for the encounter, per CMS inpatient sequencing guidelines.

Standardized digital clinical documentation forms help transplant teams capture the distinction between rejection types at the point of care, reducing the risk of defaulting to T86.30 (unspecified) when more specific coding is supported by the clinical record. This approach also mirrors best practices for neurodevelopmental ICD-10 diagnosis coding, where specificity in documentation directly determines billable status.

Streamline transplant follow-up billing with Pabau

Pabau's integrated claims management and documentation tools help transplant coordinators capture the right ICD-10-CM codes at the point of care, reducing denials and supporting accurate billing for complex post-transplant encounters.

Book a demo

Sequencing rules for ICD-10 code T86.31 in inpatient and outpatient settings

Sequencing T86.31 correctly depends on whether the encounter is inpatient or outpatient, and whether rejection is the primary reason for the visit or an incidental finding during a scheduled transplant follow-up.

Inpatient sequencing

For inpatient admissions, the principal diagnosis is the condition established after study to be chiefly responsible for the admission. When a heart-lung transplant recipient is admitted specifically for suspected or confirmed rejection, T86.31 is the principal diagnosis. Supporting conditions (such as immunosuppressive therapy complications or secondary infections) are coded as additional diagnoses.

Per the WHO ICD-10 classification framework, external cause codes in the T-range are inherently supplemental context codes. T86.31 does not require an additional external cause code for the transplant procedure itself when rejection is the established complication.

Outpatient sequencing

In outpatient transplant follow-up clinics, T86.31 is coded when rejection has been confirmed or when the physician documents it as the primary management concern for that visit. If the visit is routine surveillance with no active rejection, coders should use the appropriate transplant status code (Z94.3 for heart-lung transplant status) rather than T86.31.

Practices managing complex post-transplant follow-up schedules benefit from structured approaches to ICD-10 coding for complex diagnoses and from practice management software that supports multi-code encounter documentation without requiring manual cross-referencing at the time of billing.

7th character and additional coding notes

T86.31 does not require a 7th character extension. Unlike many Chapter 19 injury codes (which require initial encounter, subsequent encounter, or sequela designations), the T86 complication subcategory does not use 7th character extensions. This is a frequent point of confusion for coders transitioning from other Chapter 19 code families.

If immunosuppressive therapy is active at the time of the encounter, coders should also add a code for long-term use of immunosuppressant (Z79.899) as an additional code. This supports medical necessity documentation and is particularly relevant for payer review of transplant maintenance claims.

Documentation requirements for T86.31 claims

Transplant rejection claims face above-average scrutiny from Medicare, Medicaid, and private payers. The documentation standard for T86.31 is higher than for routine outpatient diagnosis coding because rejection is a high-cost complication with significant downstream treatment implications.

• Physician attestation: A physician (not just a nurse or coordinator) must document the rejection diagnosis. The note must state “rejection” explicitly, not simply “graft dysfunction” or “transplant complication.”
• Biopsy results: Pathology reports from endomyocardial or transbronchial biopsy confirming lymphocytic infiltration, fibrosis, or other rejection-pattern changes are the gold-standard supporting documentation.
• Functional testing: Clinicians should document pulmonary function test results (declining FEV1 or FVC) or echocardiographic findings (reduced ejection fraction) and link them to the rejection diagnosis in the clinical note.
• Immunosuppression management: Documentation of adjustments to calcineurin inhibitor dosing, addition of pulse steroids, or initiation of rescue therapy (such as anti-thymocyte globulin) supports the clinical picture and ties the management plan directly to the T86.31 diagnosis.
• Timeframe and rejection history: Note whether this is a first rejection episode or a recurrence. Chronic rejection in particular benefits from documentation of the temporal relationship to the transplant date.

Practices with HIPAA-compliant documentation workflows are better positioned to retain and produce this supporting evidence during payer audits. The patient record management system used should allow transplant teams to attach biopsy reports, PFT results, and physician attestations directly to the encounter record without relying on external document stores.

Adjacent codes and crosswalk reference for T86.31

Transplant follow-up billing rarely involves T86.31 in isolation. Understanding the adjacent code landscape helps coders select additional diagnoses accurately and avoid undercoding complex post-transplant encounters.

For crosswalk verification between ICD-10-CM codes and CPT procedure codes used in transplant follow-up (such as bronchoscopy or endomyocardial biopsy CPT codes), the CMS Physician Fee Schedule lookup tool allows coders to verify that the diagnosis code supports medical necessity for the paired procedure code at the payer level.

Practices that manage both transplant and non-transplant patient populations benefit from EHR integration for clinical coding that connects the diagnostic code set to procedure order workflows, reducing the manual effort required to pair T86.31 with the correct CPT code for the clinical service rendered.

Conclusion

Heart-lung transplant rejection billing hinges on one critical distinction: documentation that confirms immune-mediated rejection (T86.31), not failure (T86.32) or infection (T86.33). Biopsy confirmation, physician attestation, and functional test results are the three documentation pillars that separate a clean claim from one destined for denial or audit.

Pabau’s compliance management workflows help transplant and specialty clinic teams maintain documentation standards that support accurate ICD-10-CM code assignment across complex post-surgical encounters. To see how Pabau supports clinical documentation and billing for specialty practices, book a demo.

Expert picks

Continue your research

Need a structured approach to clinical compliance documentation? Compliance management software helps specialty practices maintain audit-ready records across complex post-surgical encounters.

Want to reduce claim errors across your billing workflow? Medical forms at your healthcare practice covers how structured intake and clinical forms reduce coding ambiguity at the point of care.

Looking for guidance on managing complex patient records in specialty settings? Why you should keep client records up to date outlines the clinical and compliance rationale for current, complete patient documentation.

Frequently Asked Questions