What is ICD-10 code T86.859?

T86.859 is the ICD-10-CM diagnosis code for Unspecified complication of intestine transplant. An unspecified problem or complication that occurs after a patient receives a transplanted intestine, where the specific type of complication is not identified. T86.859 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. T86.859 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. T86.859 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. T86.859 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Which HCC does T86.859 map to under V28?

T86.859 maps to CMS-HCC V28 77 (Intestine Transplant Status/Complications). The category number and label come from the CMS-HCC V28 model file for payment year 2026.

What does T86.859 pay in RAF?

T86.859 carries a community, non-dual, aged (CNA) RAF weight of 1.172 under CMS-HCC V28 for payment year 2026. The weight comes from the CMS V28 relative-factor file, not a hand-typed table.

What is the V28 vs V24 difference for T86.859?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. For T86.859, V28 maps to Intestine Transplant Status/Complications at RAF 1.172 while V24 mapped to Major Organ Transplant or Replacement Status at RAF 0.832. Both models can still appear in legacy data and in payer-specific lookback periods.

What documentation supports T86.859?

Use this code only when the specific complication (rejection, failure, infection) is not documented; query the provider for more specificity Review transplant records and clinical notes to determine if a more specific T86.8x code applies Because T86.859 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score. See the MEAT criteria checklist at /meat-criteria for what Monitor, Evaluate, Assess, or Treat looks like in a note. MEAT is generic documentation evidence, not a payer-specific rule.

2026 ICD-10-CM T86.859: Unspecified

T86.859 maps to CMS-HCC V28 77 (RAF 1.172). Documentation must support MEAT. MEAT criteria · RAF calculator · HCC coding software

ICD-10-CM Code View

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Code lookupT86.859Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Injury, poisoning and certain other consequences of external causes (S00-T88) / Complications of surgical and medical care, not elsewhere classified (T80-T88)

T86.859

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Unspecified complication of intestine transplant

An unspecified problem or complication that occurs after a patient receives a transplanted intestine, where the specific type of complication is not identified.

Buddy Insight

Unspecified intestinal transplant complication indicates a documented transplant-related problem without specific identification.

CMS-HCC V28

Mapped

HCC 77

Intestine Transplant Status/C...

RAF 1.172

CMS-HCC V24

Mapped

HCC 186

Major Organ Transplant or Rep...

RAF 0.832

ACA/HHS

Mapped

HCC 41

HHS-HCC 41

Varies by metal level

ESRD/PACE

Mapped

HCC 186

Major Organ Transplant or Rep...

RAF 0.138

RXHCC

Mapped

HCC 396

Allograft Complications

Not separately weighted

Code Book Path

Official

T86.8Complications of other transplanted organs and tissues

T86.85Complication of intestine transplant

T86.859Unspecified complication of intestine transplant

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for T86.859 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for T86.859 in this effective period.

Related Child Codes

Official

T86.850Intestine transplant rejection

T86.851Intestine transplant failure

T86.852Intestine transplant infection

T86.858Other complications of intestine transplant

Includes

Official

ICD-10-CM does not list Includes notes for T86.859 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for T86.859 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for T86.859 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for T86.859 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for T86.859 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Documentation of intestinal transplant procedure

Evidence of transplant-related complication without specific type

Clinical findings suggesting complication presence

Provider acknowledgment of complication

MEAT Support

HCC Buddy guidance

Documentation of intestinal transplant procedure

Evidence of transplant-related complication without specific type

Clinical findings suggesting complication presence

Provider acknowledgment of complication

Audit Caution

HCC Buddy guidance

Using when specific complications are documented

Applying to routine post-transplant visits without complications

Not querying for more specific complication details

Missing opportunities for more precise coding

Common Mistakes

HCC Buddy guidance

Z94.82 — intestine transplant status (complication vs stable status)

T86.858 — other intestine transplant complications (unspecified vs other specified)

T86.850-852 — specific intestine transplant complications (unspecified vs specific)

K63.9 — disease of intestine unspecified (transplant vs native bowel)

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is T86.859 an HCC code?

Yes. T86.859 (Unspecified complication of intestine transplant) maps to Intestine Transplant Status/Complications under the CMS-HCC V28 risk adjustment model (and Major Organ Transplant or Replacement Status under V24), with a community non-dual aged RAF of 1.172. It is billable for payment year 2026.

Coder answer: T86.859 is billable and maps to V28 HCC 77, Intestine Transplant Status/Complications. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: T86.859
Description: Unspecified complication of intestine transplant
HCC (V28): HCC 77 — Intestine Transplant Status/Complications
RAF: 1.172
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 77, Intestine Transplant Status/Complications

1.172

V24HCC 186, Major Organ Transplant or Replacement Status

0.832

ESRDHCC 186, Major Organ Transplant or Replacement Status

0.138

RxHCCHCC 396, Allograft Complications

Not separately weighted

Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

Work T86.859 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for T86.859

For T86.859 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
EEvaluate: test results, medication response, or physical findings reviewed by the provider
AAssess: explicit mention in the assessment or plan with acknowledgment of status
TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed T86.859 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

T86.859 is the ICD-10-CM diagnosis code for unspecified complication of intestine transplant. An unspecified problem or complication that occurs after a patient receives a transplanted intestine, where the specific type of complication is not identified. T86.859 sits in the ICD-10-CM chapter for injury, poisoning and certain other consequences of external causes (s00-t88), within the section covering complications of surgical and medical care, not elsewhere classified (t80-t88).

Under the CMS-HCC V28 risk adjustment model, T86.859 maps to Intestine Transplant Status/Complications (HCC 77) with a community, non-dual, aged base RAF weight of 1.172. Under the older CMS-HCC V24 model, T86.859 maps to Major Organ Transplant or Replacement Status (HCC 186) with a community, non-dual, aged base RAF weight of 0.832. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.

Use this code only when the specific complication (rejection, failure, infection) is not documented; query the provider for more specificity. Because T86.859 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for T86.859 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Use this code only when the specific complication (rejection, failure, infection) is not documented; query the provider for more specificity
•Review transplant records and clinical notes to determine if a more specific T86.8x code applies

Clinical Significance

Unspecified intestinal transplant complication indicates a documented transplant-related problem without specific identification. Despite lack of specificity, this represents significant risk requiring ongoing specialized monitoring and care.

Documentation Requirements

✓Documentation of intestinal transplant procedure
✓Evidence of transplant-related complication without specific type
✓Clinical findings suggesting complication presence
✓Provider acknowledgment of complication
✓Treatment or monitoring plans
✓Exclusion of normal post-transplant status
✓Rationale for unspecified nature
✓Plans for further evaluation if appropriate

Commonly Confused Codes

•Z94.82: intestine transplant status (complication vs stable status)
•T86.858: other intestine transplant complications (unspecified vs other specified)
•T86.850-852: specific intestine transplant complications (unspecified vs specific)
•K63.9: disease of intestine unspecified (transplant vs native bowel)
•T86.90: unspecified transplant complication (intestine-specific vs general)