2026 ICD-10-CM Diagnosis Code R18.8Other ascites

ICD-10-CM Codes›R00–R99›R10-R19›R18

ICD-10-CM R18.8
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

R18.8 is a billable ICD-10-CM diagnosis code for other ascites. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 947 through 948. As a symptom code, it should not be used as a principal diagnosis once a related definitive diagnosis has been established. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Abdominal pain and other digestive/abdomen signs and symptoms.

Code Identity

ICD-10-CM Code
R18.8
Billable Status
Yes — Valid for Submission
Code Describes
Other ascites
Short Description
Other ascites
Same as the full description in the CMS dataset.
Parent Code
R18
Ascites

Code Classification

ChapterR00–R99Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified
SectionR10-R19Symptoms and signs involving the digestive system and abdomen
CategoryR18Ascites
This CodeR18.8Other ascites

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Ascites
  • Bile ascites
  • Bloody peritoneal effusion
  • Chronic peritoneal effusion
  • Dialysis-associated ascites
  • Fluid in peritoneal cavity
  • Fluid-filled abdomen
  • Hemorrhage into peritoneal cavity
  • Hemorrhagic ascites
  • Hepatic ascites
  • Infected ascites
  • Leakage of bile
  • Meigs' syndrome
  • Metabolic ascites
  • Pancreatic ascites
  • Refractory ascites
  • Tense ascites
  • Urine ascites
  • Urine ascites of the neonate

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Ascites NOS
  • Peritoneal effusion (chronic)

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Ascites(abdominal)
    • Ascites(abdominal)
      • pseudochylous
    • Dropsy, dropsical
      • abdomen
    • Effusion
      • peritoneal (chronic)
    • Fluid
      • abdomen
    • Fluid
      • peritoneal cavity
    • Hydroperitoneum
    • Hydrops
      • abdominis

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR SYM006
Abdominal pain and other digestive/abdomen signs and symptoms
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Ascites

    accumulation or retention of free fluid within the peritoneal cavity.

  • Carcinoma, Ehrlich Tumor

    a transplantable, poorly differentiated malignant tumor which appeared originally as a spontaneous breast carcinoma in a mouse. it grows in both solid and ascitic forms.

  • Chylous Ascites

    presence of milky lymph (chyle) in the peritoneal cavity, with or without infection.

  • Mucin-4

    a transmembrane mucin that is found in a broad variety of epithelial tissue. mucin-4 may play a role in regulating cellular adhesion and in cell surface signaling from the erbb-2 receptor protein-tyrosine kinase. mucin-4 is a heterodimer of alpha and beta chains. the alpha and beta chains result from the proteolytic cleavage of a precursor protein.

  • Peritoneovenous Shunt

    an operation for the continuous emptying of ascitic fluid into the venous system. fluid removal is based on intraperitoneal and intrathoracic superior vena cava pressure differentials and is performed via a pressure-sensitive one-way valve connected to a tube traversing the subcutaneous tissue of the chest wall to the neck where it enters the internal jugular vein and terminates in the superior vena cava. it is used in the treatment of intractable ascites.

  • Pseudomyxoma Peritonei

    a peritoneal adenocarcinoma characterized by build-up of mucus in the peritoneal cavity. mucus secreting cells may attach to the peritoneal lining and continue to secrete mucus. the majority of cases represent tumor spread from a primary low-grade mucinous neoplasm of the appendix (nci thesaurus).

  • Receptor, ErbB-2

    a cell surface protein-tyrosine kinase receptor that is overexpressed in a variety of adenocarcinomas. it has extensive homology to and heterodimerizes with the egf receptor, the erbb-3 receptor, and the erbb-4 receptor. activation of the erbb-2 receptor occurs through heterodimer formation with a ligand-bound erbb receptor family member.

  • Chronic Peritoneal Effusion

    persistent or recurring accumulation of fluid in the peritoneal cavity.

Patient EducationClinical

Liver Diseases

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Convert R18.8 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
568.82 Peritoneal effusion
Approximate The match is approximate rather than exact.
ICD-9-CM
789.59 Ascites NEC
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About R18.8Overview

Is R18.8 (Ascites) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report other ascites on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does R18.8 group to?

When other ascites is the principal diagnosis on an inpatient stay, it groups to MS-DRG 947, 948, with relative weights from 0.8005 to 1.2694 depending on complications. Higher weights mean higher Medicare reimbursement.

Can R18.8 be a principal diagnosis?

Use it with care. This is a symptom code, so once a definitive diagnosis explaining the other ascites is established, that condition takes the principal position instead.

What is the ICD-9 equivalent of R18.8?

Under the General Equivalence Mappings, other ascites converts to ICD-9-CM 568.82 (peritoneal effusion) and 789.59 (ascites NEC). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.