C18.6
BillableMalignant neoplasm of descending colon
HCC Category Mapping
V28HCC 22 — Colorectal, Bladder, and Other Cancers
0.000V24HCC 11 — Colorectal, Bladder, and Other Cancers
0.306ESRDHCC 11 — Colorectal, Bladder, and Other Cancers
0.000What This Code Means
Cancer that occurs in the descending colon, which is the portion of the large intestine that runs downward on the left side of the abdomen.
Coding Tips
- •Distinguish between descending colon (C18.6) and sigmoid colon (C18.7) based on anatomical documentation
- •Confirm the tumor does not extend into the sigmoid colon, which would require a different code
Clinical Significance
Malignant neoplasm of the descending colon occurs in the left-sided portion of the large intestine running vertically from the splenic flexure to the sigmoid colon. Left-sided colon cancers have distinct molecular profiles compared to right-sided cancers, with different responses to targeted therapies. These tumors are more likely to present with obstructive symptoms due to the narrower lumen of the descending colon compared to the right colon.
Documentation Requirements
- ✓Documentation confirming descending colon as the tumor location
- ✓Histological type and grade
- ✓Stage of disease with lymph node status
- ✓KRAS/NRAS/BRAF mutation status if tested (affects targeted therapy eligibility)
- ✓Colonoscopy or surgical pathology confirmation
Commonly Confused Codes
C18.5 — Splenic flexure: the splenic flexure is above the descending colon; confirm documentation specifies the straight descending segmentC18.7 — Sigmoid colon: the sigmoid begins where the descending colon curves into the S-shape; verify anatomical boundaryC18.9 — Colon, unspecified: use C18.6 when descending colon is documented
Code Hierarchy
└C18Malignant neoplasm of colon└C18.6Malignant neoplasm of descending colon
└C18.6Malignant neoplasm of descending colon