C18.5 ICD-10-CM Code: Malignant neoplasm of splenic flexure
C18.5 maps to CMS-HCC V28 22 (RAF 0.363). Documentation must support MEAT. MEAT criteria · RAF calculator · HCC coding software
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FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of digestive organs (C15-C26)
C18.5
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceMalignant neoplasm of splenic flexure
Cancer that develops at the splenic flexure, which is the bend in the colon near the spleen where the transverse colon turns downward.
Buddy Insight
Malignant neoplasm of the splenic flexure occurs at the bend where the transverse colon turns downward to become the descending colon, near the spleen.
CMS-HCC V28
MappedHCC 22
RAF 0.363
CMS-HCC V24
MappedHCC 11
RAF 0.307
ACA/HHS
MappedHCC 11
Varies by metal level
ESRD/PACE
MappedHCC 11
RAF 0.059
RXHCC
N/A—
Not mapped
Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for C18.5 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for C18.5 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for C18.5 in this effective period.
Excludes 1
Official- malignant carcinoid tumors of the colon (C7A.02-)
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for C18.5 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for C18.5 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for C18.5 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
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 C18.5 an HCC code?
Yes. C18.5 (Malignant neoplasm of splenic flexure) maps to Bladder, Colorectal, and Other Cancers under the CMS-HCC V28 risk adjustment model (and Colorectal, Bladder, and Other Cancers under V24), with a community non-dual aged RAF of 0.363. It is billable for payment year 2026.
Coder answer: C18.5 is billable and maps to V28 HCC 22, Bladder, Colorectal, and Other Cancers. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- C18.5
- Description
- Malignant neoplasm of splenic flexure
- HCC (V28)
- HCC 22 — Bladder, Colorectal, and Other Cancers
- RAF
- 0.363
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
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 C18.5 in the Code Book — tabular path, V28 RAF, and MEAT checklist →
MEAT Criteria for C18.5
For C18.5 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 C18.5 during that encounter, not just copy-forwarded from a problem list.
Coder workflow notes
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What This Code Means
C18.5 is the ICD-10-CM diagnosis code for malignant neoplasm of splenic flexure. Cancer that develops at the splenic flexure, which is the bend in the colon near the spleen where the transverse colon turns downward. C18.5 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of digestive organs (c15-c26).
Under the CMS-HCC V28 risk adjustment model, C18.5 maps to Bladder, Colorectal, and Other Cancers (HCC 22) with a community, non-dual, aged base RAF weight of 0.363. Under the older CMS-HCC V24 model, C18.5 maps to Colorectal, Bladder, and Other Cancers (HCC 11) with a community, non-dual, aged base RAF weight of 0.307. 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.
The splenic flexure is a specific anatomical landmark; confirm documentation specifies this location rather than adjacent colon segments. Because C18.5 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 C18.5 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •The splenic flexure is a specific anatomical landmark; confirm documentation specifies this location rather than adjacent colon segments
- •This location may require different surgical approaches than other colon cancers
Clinical Significance
Malignant neoplasm of the splenic flexure occurs at the bend where the transverse colon turns downward to become the descending colon, near the spleen. This is one of the less common colorectal cancer sites and has unique surgical considerations due to its proximity to the spleen, left kidney, and pancreatic tail. Splenic flexure cancers may require mobilization of the spleen and distal pancreas during resection.
Documentation Requirements
- ✓Documentation specifying splenic flexure as the tumor location
- ✓Histological type and grade
- ✓Stage of disease
- ✓Relationship to spleen and adjacent structures
- ✓Colonoscopy or surgical confirmation
Commonly Confused Codes
- •C18.4: Transverse colon: the splenic flexure is the bend at the end of the transverse colon, not the straight transverse segment
- •C18.6: Descending colon: the descending colon begins after the splenic flexure going downward
- •C18.8: Overlapping sites: use when tumor spans from transverse colon through splenic flexure into descending colon