2026 ICD-10-CM Diagnosis Code K66.8Other specified disorders of peritoneum

ICD-10-CM Codes›K00–K95›K65-K68›K66

ICD-10-CM K66.8
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

K66.8 is a billable ICD-10-CM diagnosis code for other specified disorders of peritoneum. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 393 through 395. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified and unspecified gastrointestinal disorders.

Code Identity

ICD-10-CM Code
K66.8
Billable Status
Yes — Valid for Submission
Code Describes
Other specified disorders of peritoneum
Short Description
Other specified disorders of peritoneum
Same as the full description in the CMS dataset.
Parent Code
K66
Other disorders of peritoneum

Code Classification

ChapterK00–K95Diseases of the digestive system
SectionK65-K68Diseases of peritoneum and retroperitoneum
CategoryK66Other disorders of peritoneum
This CodeK66.8Other specified disorders of peritoneum

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Congenital mesocolic hernia
  • Fibrosis of mesentery
  • Fibrosis of pelvic cavity
  • Frozen pelvis syndrome
  • Hydrocele of canal of Nuck
  • Intraperitoneal fibrosis
  • Male frozen pelvis
  • Male pelvic adhesions
  • Malignant frozen pelvis
  • Mesenteric cyst
  • Mesenteric hernia
  • Mesenteric pseudocyst
  • Non-malignant frozen pelvis
  • Non-malignant male frozen pelvis
  • Omental cyst
  • Omental hematoma
  • Omental hemorrhage
  • Omental pseudocyst
  • Omental wrapping around peritoneal dialysis catheter
  • Perirenal pseudocyst
  • Peritoneal cyst
  • Peritoneal fibrosis
  • Peritoneal granuloma
  • Peritoneal mouse
  • Peritoneal pseudocyst
  • Pneumoperitoneum
  • Poor drainage of peritoneal dialysis catheter

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.

    • Cyst(colloid) (mucous) (simple) (retention)
      • mesentery, mesenteric
    • Cyst(colloid) (mucous) (simple) (retention)
      • omentum (lesser)
    • Cyst(colloid) (mucous) (simple) (retention)
      • peritoneum
    • Disease, diseased
      • peritoneum
        • specified NEC
    • Frozen
      • pelvis (female)
        • male
    • Granuloma
      • abdomen
    • Granuloma
      • peritoneum
    • Pneumatosis
      • peritonei
    • Rupture, ruptured
      • mesentery (nontraumatic)

Clinical ClassificationClinical

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

CCSR DIG025
Other specified and unspecified gastrointestinal disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Pneumoperitoneum

    a condition with trapped gas or air in the peritoneal cavity, usually secondary to perforation of the internal organs such as the lung and the gastrointestinal tract, or to recent surgery. pneumoperitoneum may be purposely introduced to aid radiological examination.

  • Pneumoperitoneum, Artificial

    deliberate introduction of air into the peritoneal cavity.

  • Mesenteric Cyst

    a rare intra-abdominal tumor in the mesentery. mesenteric cysts are usually benign and can be very large fluid-filled (2000 ml) lesions.

  • Peritoneal Fibrosis

    disorder characterized by a wide range of structural changes in peritoneum, resulting from fibrogenic or inflammatory processes. peritoneal fibrosis is a common complication in patients receiving peritoneal dialysis and contributes to its gradual decrease in efficiency.

  • Pneumoperitoneum

    free air within the peritoneal cavity.

Patient EducationClinical

Peritoneal Disorders

Your peritoneum is the tissue that lines your abdominal wall and covers most of the organs in your abdomen. A liquid, peritoneal fluid, lubricates the surface of this tissue.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert K66.8 to ICD-9-CMHistory

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

ICD-9-CM
568.89 Peritoneal disorder NEC
Approximate The match is approximate rather than exact.

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 K66.8Overview

Is K66.8 (Other disorders of peritoneum) a billable code?

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

What MS-DRG does K66.8 group to?

When other specified disorders of peritoneum is the principal diagnosis on an inpatient stay, it groups to MS-DRG 393, 394, 395, with relative weights from 0.6490 to 1.5993 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of K66.8?

Under the General Equivalence Mappings, other specified disorders of peritoneum converts to ICD-9-CM 568.89 (peritoneal disorder 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.