2027 ICD-10-CM Diagnosis Code K65.0Generalized (acute) peritonitis
ICD-10-CM Codes›K00–K95›K65-K6A›K65
- Billable — Valid for Submission
- MCC — Major Complication or Comorbidity
- Risk Adjusts — HCC 78
- Not Chronic
K65.0 is a billable ICD-10-CM diagnosis code for generalized (acute) peritonitis. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 371 through 373, 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 25 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Peritonitis and intra-abdominal abscess.
For Medicare Advantage risk adjustment, K65.0 maps to CMS-HCC Category 78 (Intestinal Obstruction/Perforation) under the V28 model, adding a risk factor of about 0.326 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
K65.0 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.
Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Acute bacterial peritonitis
- Acute generalized peritonitis
- Acute infectious generalized peritonitis
- Acute infectious peritonitis
- Acute pelvic peritonitis
- Acute peritonitis
- Acute suppurative peritonitis
- Chronic inflammation of pelvic peritoneum
- Chronic peritonitis
- Pelvic peritonitis
- Purulent peritonitis
- Subphrenic peritonitis
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to K65.0: its own notes plus those printed at K65 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.
- Pelvic peritonitis (acute), male
- Subphrenic peritonitis (acute)
- Suppurative peritonitis (acute)
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
- acute appendicitis with generalized peritonitis (K35.2-)
- aseptic peritonitis (T81.6)
- benign paroxysmal peritonitis (E85.0)
- chemical peritonitis (T81.6)
- gonococcal peritonitis (A54.85)
- neonatal peritonitis (P78.0-P78.1)
- pelvic peritonitis, female (N73.3-N73.5)
- periodic familial peritonitis (E85.0)
- peritonitis due to talc or other foreign substance (T81.6)
- peritonitis in chlamydia (A74.81)
- peritonitis in diphtheria (A36.89)
- peritonitis in syphilis (late) (A52.74)
- peritonitis in tuberculosis (A18.31)
- peritonitis with or following abortion or ectopic or molar pregnancy (O00-O07, O08.0)
- peritonitis with or following appendicitis (K35.-)
- puerperal peritonitis (O85)
- retroperitoneal infections (K68.-)
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)
Use Additional Code
Add a second code, after this one, to fully describe the condition.
Code Also
A second code may be needed to fully describe the condition; the note gives no sequencing direction.
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name K65.0, its category, or a range that includes it.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Peritonitis (adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion) K65.9
acute (generalized) K65.0
diaphragmatic K65.0
diffuse K65.0
disseminated K65.0
acute K65.0
fibropurulent K65.0
general (ized) K65.0
pancreatic K65.0
pelvic (see also, if applicable, Abscess, abdominopelvic)
male K65.0
purulent K65.0
septic K65.0
subdiaphragmatic K65.0
subphrenic K65.0
suppurative K65.0
Suppuration, suppurative See Also: condition;
male K65.0
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Peritonitis
inflammation of the peritoneum lining the abdominal cavity as the result of infectious, autoimmune, or chemical processes. primary peritonitis is due to infection of the peritoneal cavity via hematogenous or lymphatic spread and without intra-abdominal source. secondary peritonitis arises from the abdominal cavity itself through rupture or abscess of intra-abdominal organs.
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 K65.0 to ICD-9-CMHistory
Code HistoryHistory
Questions About K65.0Overview
What is the ICD-10 code for generalized (acute) peritonitis?
The ICD-10-CM code for generalized (acute) peritonitis is K65.0 (sometimes written as K650). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is K65.0 (Peritonitis) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report generalized (acute) peritonitis on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does K65.0 group to?
When generalized (acute) peritonitis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 372, 793, 791, 371, 373, with relative weights from 0.6945 to 4.2192 depending on complications. Higher weights mean higher Medicare reimbursement.
Is K65.0 a CC or MCC?
CMS lists K65.0 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 25 closely related codes in its exclusion list.
Can K65.0 be reported with a code from K35.2?
Not as a rule. The Excludes1 note at K65, which applies to K65.0, lists "acute appendicitis with generalized peritonitis (K35.2-)". 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).
What HCC is K65.0?
K65.0 (generalized (acute) peritonitis) maps to CMS-HCC Category 78 (Intestinal Obstruction/Perforation), commonly written as HCC 78, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 33 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. It does not map to any RxHCC in the Part D prescription drug model.
Does K65.0 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, K65.0 adds a risk adjustment factor of about 0.326 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.326 to 0.688 depending on the payment segment). A more severe related category (HCC 77) supersedes it when both are reported. See the full factor table on the HCC 78 category page.
