MCMCB Pro
R18.0

R18.0Malignant ascites

Billable / specific codeICD-10-CM

R18.0 is a billable, specific ICD-10-CM code for malignant ascites. It is valid for submission on a claim.

Code first

The underlying condition must be sequenced before this code.

  • malignancy, such as:
  • malignant neoplasm of ovary (C56.-)
  • secondary malignant neoplasm of retroperitoneum and peritoneum (C78.6)

Risk adjustment

R18.0 risk-adjusts. Under the CMS-HCC V28 model it maps to this category:

  • HCC 17 Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic4.209 RAF

Coefficient shown for the Community Non-dual Aged segment. A higher HCC in the same hierarchy will suppress this one, so capturing it does not always add score.

Medicare coverage

R18.0 is named in 7 Medicare coverage policies 7 listing it as supporting medical necessity. Which of them applies to you depends on your Medicare contractor, and coverage genuinely differs by state.

  • A56421Billing and Coding: CT of the Abdomen and Pelvis
  • A56464Billing and Coding: Flow Cytometry
  • A56697Billing and Coding: Non-Invasive Vascular Studies
  • A56758Billing and Coding: Non-Invasive Vascular Studies

How R18.0 is indexed

Coders do not find codes by browsing the tabular list — they look them up in the alphabetic index, under the word the physician wrote. These are the index entries that lead here, so you can see which chart wordings map to R18.0.

  • Ascitesmalignant

Related codes at this level

Codes that share R18. If R18.0 is not quite right, the correct code is usually one of these.

Questions about R18.0

Is R18.0 a billable ICD-10-CM code?
Yes. R18.0 is a billable, specific ICD-10-CM code and is valid for submission on a claim.
Where does R18.0 sit in the tabular list?
Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R99), in the block Symptoms and signs involving the digestive system and abdomen (R10-R19).
ICD-10-CMFY2026-Apr· effective April 1, 2026

Loaded directly from the CMS/NCHS ICD-10-CM public-domain release — see data sources and our editorial policy. If this page disagrees with the CMS tabular list, this page is wrong. Reference information for professional coders; not medical or billing advice.