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C18.3 ICD-10-CM Code: Malignant neoplasm of hepatic flexure

C18.3 maps to CMS-HCC V28 22. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · free HCC coding tools

ICD-10-CM Code View

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Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupC18.3

FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of digestive organs (C15-C26)

C18.3

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

Malignant neoplasm of hepatic flexure

Cancer that develops at the hepatic flexure, which is the bend in the colon where the ascending colon turns to become the transverse colon, located near the liver.

Buddy the Bee presenting code insight

Buddy Insight

Malignant neoplasm of the hepatic flexure occurs at the bend where the ascending colon turns to become the transverse colon, located near the liver.

OverviewRisk ModelsCode BookDocumentationAuditNotesEdition comparison

CMS-HCC V28

HCC 22

Coefficient HCC 22: 0.363 (Community Non-Dual Aged (CNA))

CMS-HCC V24

Historical

Historical

Not used for CY2026 payment

ACA/HHS

HCC 011

Code-level coefficient reference

ESRD/PACE

HCC 11

Code-level coefficient reference

RXHCC

N/A

—

Not mapped

Code Book Path

Official
C18Malignant neoplasm of colonC18.3Malignant neoplasm of hepatic flexure

Inclusion Terms

Official

No inclusion terms are included in this display for C18.3. Check the code and parent instructions in the Code Book.

Excludes 2

Official
  • gastrointestinal stromal tumors (C49.A-)Inherited from C15-C26

Related Codes

Official
C18.0Malignant neoplasm of cecumC18.1Malignant neoplasm of appendixC18.2Malignant neoplasm of ascending colonC18.4Malignant neoplasm of transverse colonC18.5Malignant neoplasm of splenic flexure

Includes

Official

No Includes notes are included in this display for C18.3. Check the code and parent instructions in the Code Book.

Excludes 1

Official
  • Kaposi's sarcoma of gastrointestinal sites (C46.4)Inherited from C15-C26, C18
  • malignant carcinoid tumors of the colon (C7A.02-)Inherited from C15-C26, C18

Code First

Official

No Code First sequencing instructions are included in this display for C18.3. Check the code and parent instructions in the Code Book.

Use Additional

Official

No Use Additional Code instructions are included in this display for C18.3. Check the code and parent instructions in the Code Book.

Code Also

Official

No Code Also instructions are included in this display for C18.3. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance
Documentation specifying hepatic flexure as the tumor location
Histological type confirmed by pathology
Stage of disease
Relationship to adjacent structures (liver, duodenum, kidney)

MEAT Support

HCC Buddy guidance
Documentation specifying hepatic flexure as the tumor location
Histological type confirmed by pathology
Stage of disease
Relationship to adjacent structures (liver, duodenum, kidney)

Audit Caution

HCC Buddy guidance
Coding ascending colon cancer as hepatic flexure or vice versa — the flexure is specifically the bend near the liver
Confusing 'hepatic flexure' with liver involvement — hepatic flexure is a colon structure, not a liver structure
Using C18.9 when the surgical or colonoscopy report specifies hepatic flexure

Common Mistakes

HCC Buddy guidance
C18.2 — Ascending colon: the ascending colon is below the hepatic flexure; confirm documentation specifies the flexure, not just the ascending segment
C18.4 — Transverse colon: the transverse colon begins after the hepatic flexure; ensure the tumor is at the turn, not in the straight transverse portion
C78.7 — Secondary malignant neoplasm of liver: do not confuse liver metastasis with hepatic flexure primary cancer

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 C18.3 an HCC code?

Yes. C18.3 (Malignant neoplasm of hepatic flexure) maps to HCC 22, Bladder, Colorectal, and Other Cancers under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.363. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.

Coder answer: C18.3 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
C18.3
Description
Malignant neoplasm of hepatic flexure
HCC (V28)
HCC 22 — Bladder, Colorectal, and Other Cancers
RAF reference coefficient
0.363
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 22, Bladder, Colorectal, and Other Cancers
0.363
ESRDHCC 11, Colorectal/Bladder/and Other Cancers
Not separately weighted

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. 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 context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work C18.3 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for C18.3

For C18.3, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

  • 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

Coder workflow notes

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What This Code Means

C18.3 is the ICD-10-CM diagnosis code for malignant neoplasm of hepatic flexure. Cancer that develops at the hepatic flexure, which is the bend in the colon where the ascending colon turns to become the transverse colon, located near the liver. C18.3 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, C18.3 maps to Bladder, Colorectal, and Other Cancers (HCC 22) with a source-labeled community, non-dual, aged reference coefficient of 0.363. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.

Hepatic flexure tumors are anatomically challenging for surgical resection; document surgical approach if available. For C18.3, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, and MEAT documentation criteria for C18.3 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Hepatic flexure tumors are anatomically challenging for surgical resection; document surgical approach if available
  • •This location is sometimes classified with right-sided colon cancers for treatment purposes

Clinical Significance

Malignant neoplasm of the hepatic flexure occurs at the bend where the ascending colon turns to become the transverse colon, located near the liver. This location presents unique surgical challenges due to proximity to the hepatic vessels, duodenum, and right kidney. Hepatic flexure cancers are classified with right-sided cancers but require distinct surgical approaches, often needing extended right hemicolectomy.

Documentation Requirements

  • ✓Documentation specifying hepatic flexure as the tumor location
  • ✓Histological type confirmed by pathology
  • ✓Stage of disease
  • ✓Relationship to adjacent structures (liver, duodenum, kidney)
  • ✓Surgical approach and extent of resection

Commonly Confused Codes

  • •C18.2: Ascending colon: the ascending colon is below the hepatic flexure; confirm documentation specifies the flexure, not just the ascending segment
  • •C18.4: Transverse colon: the transverse colon begins after the hepatic flexure; ensure the tumor is at the turn, not in the straight transverse portion
  • •C78.7: Secondary malignant neoplasm of liver: do not confuse liver metastasis with hepatic flexure primary cancer

Child Codes

C18.0Malignant neoplasm of cecum
HCC 22
C18.1Malignant neoplasm of appendix
HCC 22
C18.2Malignant neoplasm of ascending colon
HCC 22
C18.3Malignant neoplasm of hepatic flexure
HCC 22
C18.4Malignant neoplasm of transverse colon
HCC 22
C18.5Malignant neoplasm of splenic flexure
HCC 22
C18.6Malignant neoplasm of descending colon
HCC 22
C18.7Malignant neoplasm of sigmoid colon
HCC 22
C18.8Malignant neoplasm of overlapping sites of colon
HCC 22
C18.9Malignant neoplasm of colon, unspecified
HCC 22

Code Hierarchy

└C18Malignant neoplasm of colon└C18.3Malignant neoplasm of hepatic flexure
└C18.3Malignant neoplasm of hepatic flexure

Also searched as

  • C18 3
  • C183

For C18.3, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

C18.3 maps to CMS-HCC V28 category 22, Bladder, Colorectal, and Other Cancers. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. The mapping identifies a payment HCC category for C18.3. Review its source-labeled HCC coefficient above, check the RAF Calculator with complete member context for CMS-HCC V28 PY2026, and confirm the documentation the chart needs before the code is submitted. HCC Buddy shows no RAF score unless every required source and calculation check passes.

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