2027 ICD-10-CM Diagnosis Code K66.9Disorder of peritoneum, unspecified
ICD-10-CM Codes›K00–K95›K65-K6A›K66
- Billable — Valid for Submission
- Not Chronic
K66.9 is a billable ICD-10-CM diagnosis code for disorder of peritoneum, unspecified. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 393 through 395. Coders also document this condition as disorder of pelvic peritoneum. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified and unspecified gastrointestinal disorders.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Disorder of pelvic peritoneum
- Disorder of peritoneum
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to K66.9: its own notes plus those printed at K66 and Chapter 11. A note printed at a category, block or chapter applies to every code under it.
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
- certain conditions originating in the perinatal period (P04-P96)
- certain infectious and parasitic diseases (A00-B99)
- complications of pregnancy, childbirth and the puerperium (O00-O9A)
- congenital malformations, deformations and chromosomal abnormalities (Q00-Q99)
- endocrine, nutritional and metabolic diseases (E00-E88)
- injury, poisoning and certain other consequences of external causes (S00-T88)
- neoplasms (C00-D49)
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Disease, diseased See Also: Syndrome;
peritoneum K66.9
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
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 K66.9 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About K66.9Overview
What is the ICD-10 code for disorder of peritoneum, unspecified?
The ICD-10-CM code for disorder of peritoneum, unspecified is K66.9 (sometimes written as K669). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is K66.9 (Other disorders of peritoneum) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report disorder of peritoneum, unspecified on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does K66.9 group to?
When disorder of peritoneum, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 394, 395, 393, with relative weights from 0.6379 to 1.5877 depending on complications. Higher weights mean higher Medicare reimbursement.
What is the ICD-9 equivalent of K66.9?
Under the General Equivalence Mappings, disorder of peritoneum, unspecified converts to ICD-9-CM 568.9 (peritoneal disorder NOS). The mapping is a direct match.
