K65.0 ICD-10-CM Code: Generalized (acute) peritonitis
HCC Buddy Code Card
Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.
FY 2026 Apr update / Diseases of the digestive system (K00-K95) / Diseases of peritoneum and retroperitoneum (K65-K68)
K65.0
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceGeneralized (acute) peritonitis
Generalized acute peritonitis is a serious infection and inflammation of the peritoneum, the membrane lining the abdominal cavity, affecting the entire abdomen.
Buddy Insight
K65.
CMS-HCC V28
MappedHCC 78
RAF 0.0
CMS-HCC V24
MappedHCC 33
RAF 0.226
ACA/HHS
00
RAF 0
ESRD/PACE
MappedHCC 33
RAF 0.0
RXHCC
00
RAF 0
Code Trumping
Basket needed
Code Book Path
Inclusion Terms
Official- Pelvic peritonitis (acute), male
- Subphrenic peritonitis (acute)
- Suppurative peritonitis (acute)
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for K65.0 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for K65.0 in this effective period.
Excludes 1
Official- acute appendicitis with generalized peritonitis (K35.2-)
- aseptic peritonitis (T81.6)
- benign paroxysmal peritonitis (E85.0)
- chemical peritonitis (T81.6)
- gonococcal peritonitis (A54.85)
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for K65.0 in this effective period.
Use Additional
Official- code (B95-B97), to identify infectious agent, if known
Code Also
Official- if applicable diverticular disease of intestine (K57.-)
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is K65.0 an HCC code?
Yes. K65.0 maps to Intestinal Obstruction/Perforation under the CMS-HCC V28 risk adjustment model (and Intestinal Obstruction/Perforation under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for K65.0
For K65.0to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed K65.0 during that encounter, not just copy-forwarded from a problem list.
What This Code Means
K65.0 is the ICD-10-CM diagnosis code for generalized (acute) peritonitis. Generalized acute peritonitis is a serious infection and inflammation of the peritoneum, the membrane lining the abdominal cavity, affecting the entire abdomen. K65.0 sits in the ICD-10-CM chapter for diseases of the digestive system (k00-k95), within the section covering diseases of peritoneum and retroperitoneum (k65-k68).
Under the CMS-HCC V28 risk adjustment model, K65.0 maps to Intestinal Obstruction/Perforation (HCC 78) with a community, non-dual, aged base RAF weight of 0.000. Under the older V24 model, K65.0 mapped to the same category but with a base RAF weight of 0.226, V28 recalibrated weights across the entire model. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
This is a medical emergency; document the cause (perforation, infection source) if known for complete coding. Because K65.0 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for K65.0 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This is a medical emergency; document the cause (perforation, infection source) if known for complete coding
- •Distinguish from localized peritonitis by confirming the infection is generalized throughout the peritoneal cavity
Clinical Significance
K65.0 represents generalized acute peritonitis, a serious infection and inflammation of the peritoneum affecting the entire abdominal cavity. This condition is often life-threatening, requiring immediate antibiotic therapy, source control, and often surgical intervention to prevent septic shock and multi-organ failure.
Documentation Requirements
- ✓Clinical signs of generalized peritonitis (rebound tenderness, rigidity)
- ✓Evidence of acute onset and systemic involvement
- ✓Documentation of generalized rather than localized involvement
- ✓Laboratory findings supporting infection and inflammation
- ✓Imaging studies showing peritoneal inflammation or fluid
- ✓Source control measures and antibiotic therapy
- ✓Surgical intervention when indicated for source control
- ✓Intensive monitoring for sepsis and organ dysfunction
Commonly Confused Codes
- •K65.1 — Peritoneal abscess (localized collection rather than generalized inflammation)
- •K65.2 — Spontaneous bacterial peritonitis (specific type in cirrhotic patients)
- •K65.8 — Other peritonitis (when specific type is documented)
- •K63.1 — Perforation of intestine (underlying cause rather than peritonitis)
- •R10.0 — Acute abdomen (symptom rather than specific diagnosis)