2027 ICD-10-CM Diagnosis Code K66.1Hemoperitoneum

ICD-10-CM Codes›K00–K95›K65-K6A›K66

ICD-10-CM K66.1
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

K66.1 is a billable ICD-10-CM diagnosis code for hemoperitoneum. 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, 791, 793. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 1 closely related codes. Coders also document this condition as hematoma of extraperitoneal space. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified and unspecified gastrointestinal disorders.

Code Identity

ICD-10-CM Code
K66.1
Billable Status
Yes — Valid for Submission
Code Describes
Hemoperitoneum
Short Description
Hemoperitoneum
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-K6ADiseases of peritoneum and retroperitoneum
CategoryK66Other disorders of peritoneum
This CodeK66.1Hemoperitoneum

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Hematoma of extraperitoneal space
  • Hemoperitoneum as complication of peritoneal dialysis
  • Hemorrhage into peritoneal cavity
  • Intra-abdominal hematoma
  • Intraperitoneal hematoma
  • Nontraumatic hemoperitoneum
  • Omental hemorrhage
  • Perinephric hematoma
  • Retroperitoneal hematoma
  • Retroperitoneal hemorrhage

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to K66.1: 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.

Applicable To

Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.

  • Peritoneal hematoma
  • Peritoneal hemorrhage

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

  • traumatic hemoperitoneum (S36.8-)

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.

On K66.1 itself
  • retroperitoneal hematoma (K68.3)
  • retroperitoneal hemorrhage (K68.3)
From K66 Other disorders of peritoneum applies to 4 codes
  • ascites (R18.-)
  • peritoneal effusion (chronic) (R18.8)
From Chapter 11 (K00-K95) Diseases of the digestive system applies to 863 codes
  • 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.

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

  • Hemoperitoneum

    accumulations of blood in the peritoneal cavity due to internal hemorrhage.

Patient EducationClinical

Gastrointestinal Bleeding

Your digestive or gastrointestinal (GI) tract includes the esophagus, stomach, small intestine, large intestine or colon, rectum, and anus. Bleeding can come from any of these areas. The amount of bleeding can be so small that only a lab test can find it.

Read the full article at MedlinePlus

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

Convert K66.1 to ICD-9-CMHistory

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

ICD-9-CM
568.81 Hemoperitoneum
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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About K66.1Overview

What is the ICD-10 code for hemoperitoneum?

The ICD-10-CM code for hemoperitoneum is K66.1 (sometimes written as K661). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is K66.1 (Other disorders of peritoneum) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report hemoperitoneum on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does K66.1 group to?

When hemoperitoneum is the principal diagnosis on an inpatient stay, it groups to MS-DRG 793, 791, 394, 395, 393, with relative weights from 0.6379 to 4.2192 depending on complications. Higher weights mean higher Medicare reimbursement.

Is K66.1 a CC or MCC?

CMS lists K66.1 as an MCC (major complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 1 closely related codes in its exclusion list.

Can K66.1 be reported with a code from S36.8?

Not as a rule. The Excludes1 note on K66.1 lists "traumatic hemoperitoneum (S36.8-)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).