CPT (Current Procedural Terminology) codes are five-digit numeric codes used to describe medical, surgical, and diagnostic services. They are maintained by the American Medical Association and used by healthcare providers, insurers, and Medicare for billing and reimbursement.

What is the difference between facility and non-facility rates?

Non-facility (office) rates are what Medicare pays when a service is performed in a physician's office. Facility rates are lower because when a service is performed in a hospital or ambulatory surgery center, the facility bills separately for overhead costs like equipment and supplies.

RVU stands for Relative Value Unit. Medicare uses RVUs to measure the value of physician services based on three components: physician work, practice expense, and malpractice cost. Total RVUs are multiplied by the conversion factor ($33.40 in 2026) to calculate the Medicare payment amount.

Is K59.31 a billable ICD-10-CM code?

Yes. K59.31 (Toxic megacolon) is a billable/specific ICD-10-CM code and can be reported on a claim when the documentation supports it.

What HCC does K59.31 map to?

K59.31 maps to HCC78 (Intestinal Obstruction/Perforation) in the CMS-HCC V28 risk-adjustment model (Medicare Advantage / Part C) for payment year 2026. Risk-adjustable diagnoses must be documented and resubmitted each year — and survive the CMS-HCC hierarchy and edits — to count toward a member's risk score.

ICD-10-CM · K00–K95BillableHCC78

ICD-10-CM Code K59.31

Toxic megacolon

Source: CMS ICD-10-CM FY2026Effective October 1, 2025Reviewed by the D3rx Clinical Billing Team

Diagnosis information

Billable

Yes

Valid for claim submission

Chapter

K00–K95

Diseases of the digestive system

Risk adjustment

HCC

HCC78

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HCC risk adjustment (CMS-HCC V28)

HCC78Intestinal Obstruction/Perforation

Model CMS-HCC V28Payment year 2026

In CMS's Hierarchical Condition Category (HCC) model — the risk-adjustment model for Medicare Advantage (Part C) — a documented and submitted K59.31 may contribute to a member's risk score (subject to the CMS-HCC hierarchy and edits), which helps drive the plan's capitated payment for that patient. To count, the diagnosis must be supported to the MEAT standard (Monitored, Evaluated, Assessed, Treated) and reported on an eligible face-to-face encounter at least once each calendar year — risk scores reset annually.

More codes in the K59 category

Other billable ICD-10-CM codes in the same category as K59.31. Coding to the highest specificity the documentation supports is what keeps a claim clean — pick the child code that most precisely matches the diagnosis.

K59.00Constipation, unspecified
K59.01Slow transit constipation
K59.02Outlet dysfunction constipation
K59.03Drug induced constipation
K59.04Chronic idiopathic constipation
K59.09Other constipation
K59.1Functional diarrhea
K59.2Neurogenic bowel, not elsewhere classified
K59.39Other megacolon
K59.4Anal spasm
K59.81Ogilvie syndrome
K59.89Other specified functional intestinal disorders

Documentation & coding notes

K59.31 is a billable/specific ICD-10-CM code — it can be reported as a primary or secondary diagnosis when the documentation supports it. Code to the highest level of specificity the record allows.
K59.31 is risk-adjustable: it maps to HCC78 in the CMS-HCC V28 model (payment year 2026), the risk-adjustment model for Medicare Advantage (Part C). For the diagnosis to contribute to a member's risk score it must survive the CMS-HCC hierarchy and edits, be documented to the MEAT standard (Monitored, Evaluated, Assessed, Treated), and be submitted on an eligible face-to-face encounter at least once per calendar year.
Always verify the code against the current ICD-10-CM Official Guidelines and the payer's coverage policy before submitting — coverage, medical necessity edits, and sequencing rules vary by payer.

Related K00–K95 codes

K21.9 K59.00

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Medical coding disclaimer

ICD-10-CM codes and descriptions shown are from the CMS FY2026 official code set and HCC mappings from the CMS-HCC V28 model (payment year 2026), shown for educational reference. Official Guidelines, payer coverage, medical-necessity edits, and sequencing rules vary. Always verify with the current ICD-10-CM Official Guidelines and the payer before submitting claims. D3rx is not responsible for coding or billing outcomes.