ICD-10-CM 2027
ICD-10 code for peritonitis
From the official ICD-10-CM alphabetic index entry “Peritonitis (adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion)”. Page updated September 29, 2026.
About coding peritonitis
The ICD-10-CM code for peritonitis is K65.9 (Peritonitis, unspecified). The official index lists 64 more specific codes, so check the documentation for details such as type, cause, site or severity before settling on K65.9.
Within K65, choose K65.9 (unspecified) only when documentation doesn't support a more specific option: generalized (acute) peritonitis (K65.0), peritoneal abscess (K65.1), spontaneous bacterial peritonitis (K65.2), Choleperitonitis (K65.3), sclerosing mesenteritis (K65.4) and other peritonitis (K65.8).
Use an additional code (B95-B97), to identify infectious agent, if known.
As a secondary diagnosis it is an MCC (major complication or comorbidity), which can move an inpatient stay into the highest-paying "with MCC" MS-DRG of its family, unless the principal diagnosis excludes it.
More specific peritonitis codes (official index)
- with or following
- abscess K65.1 — Peritoneal abscess
- appendicitis
- with perforation or rupture K35.32 — Acute appendicitis with perforation, localized peritonitis, and gangrene, without abscess
- generalized K35.209 — Acute appendicitis with generalized peritonitis, without abscess, unspecified as to perforation
- localized K35.30 — Acute appendicitis with localized peritonitis, without perforation or gangrene
- diverticular disease (intestine) K57.80 — Diverticulitis of intestine, part unspecified, with perforation and abscess without bleeding
- with bleeding K57.81 — Diverticulitis of intestine, part unspecified, with perforation and abscess with bleeding
- large intestine K57.20 — Diverticulitis of large intestine with perforation and abscess without bleeding
- with
- bleeding K57.21 — Diverticulitis of large intestine with perforation and abscess with bleeding
- small intestine K57.40 — Diverticulitis of both small and large intestine with perforation and abscess without bleeding
- with bleeding K57.41 — Diverticulitis of both small and large intestine with perforation and abscess with bleeding
- small intestine K57.00 — Diverticulitis of small intestine with perforation and abscess without bleeding
- with
- bleeding K57.01 — Diverticulitis of small intestine with perforation and abscess with bleeding
- large intestine K57.40 — Diverticulitis of both small and large intestine with perforation and abscess without bleeding
- with bleeding K57.41 — Diverticulitis of both small and large intestine with perforation and abscess with bleeding
- ectopic or molar pregnancy O08.0 — Genital tract and pelvic infection following ectopic and molar pregnancy
- acute (generalized) K65.0 — Generalized (acute) peritonitis
- aseptic T81.61 — Aseptic peritonitis due to foreign substance accidentally left during a procedure
- bile, biliary K65.3 — Choleperitonitis
- chemical T81.61 — Aseptic peritonitis due to foreign substance accidentally left during a procedure
- chlamydial A74.81 — Chlamydial peritonitis
- complicating abortion
- congenital P78.1 — Other neonatal peritonitis
- chronic proliferative K65.8 — Other peritonitis
- diaphragmatic K65.0 — Generalized (acute) peritonitis
- diffuse K65.0 — Generalized (acute) peritonitis
- diphtheritic A36.89 — Other diphtheritic complications
- disseminated K65.0 — Generalized (acute) peritonitis
- due to
- bile K65.3 — Choleperitonitis
- foreign
- body or object accidentally left during a procedure (instrument) (sponge) (swab) T81.599 — Other complications of foreign body accidentally left in body following unspecified procedure
- substance accidentally left during a procedure (chemical) (powder) (talc) T81.61 — Aseptic peritonitis due to foreign substance accidentally left during a procedure
- talc T81.61 — Aseptic peritonitis due to foreign substance accidentally left during a procedure
- urine K65.8 — Other peritonitis
- eosinophilic K65.8 — Other peritonitis
- acute K65.0 — Generalized (acute) peritonitis
- fibrocaseous (tuberculous) A18.31 — Tuberculous peritonitis
- fibropurulent K65.0 — Generalized (acute) peritonitis
- following ectopic or molar pregnancy O08.0 — Genital tract and pelvic infection following ectopic and molar pregnancy
- general (ized) K65.0 — Generalized (acute) peritonitis
- gonococcal A54.85 — Gonococcal peritonitis
- meconium (newborn) P78.0 — Perinatal intestinal perforation
- neonatal P78.1 — Other neonatal peritonitis
- meconium P78.0 — Perinatal intestinal perforation
- pancreatic K65.0 — Generalized (acute) peritonitis
- paroxysmal, familial E85.0 — Non-neuropathic heredofamilial amyloidosis
- benign E85.0 — Non-neuropathic heredofamilial amyloidosis
- pelvic (see also, if applicable, Abscess, abdominopelvic)
- female N73.5 — Female pelvic peritonitis, unspecified
- acute N73.3 — Female acute pelvic peritonitis
- chronic N73.4 — Female chronic pelvic peritonitis
- with adhesions N73.6 — Female pelvic peritoneal adhesions (postinfective)
- male K65.0 — Generalized (acute) peritonitis
- periodic, familial E85.0 — Non-neuropathic heredofamilial amyloidosis
- proliferative, chronic K65.8 — Other peritonitis
- puerperal, postpartum, childbirth O85 — Puerperal sepsis
- purulent K65.0 — Generalized (acute) peritonitis
- septic K65.0 — Generalized (acute) peritonitis
- specified NEC K65.8 — Other peritonitis
- spontaneous bacterial K65.2 — Spontaneous bacterial peritonitis
- subdiaphragmatic K65.0 — Generalized (acute) peritonitis
- subphrenic K65.0 — Generalized (acute) peritonitis
- suppurative K65.0 — Generalized (acute) peritonitis
- syphilitic A52.74 — Syphilis of liver and other viscera
- congenital (early) A50.08 — Early visceral congenital syphilis
- talc T81.61 — Aseptic peritonitis due to foreign substance accidentally left during a procedure
- tuberculous A18.31 — Tuberculous peritonitis
- urine K65.8 — Other peritonitis
Common questions about peritonitis ICD-10 codes
What is the ICD-10 code for peritonitis?
- K65.9 — Peritonitis, unspecified. More specific codes apply when the documentation supports them: K65.1, K35.32, K35.209, K35.30 and others below.
What is the ICD-10 code for acute peritonitis?
- K65.0 — Generalized (acute) peritonitis.
What is the ICD-10 code for aseptic peritonitis?
- T81.61 — Aseptic peritonitis due to foreign substance accidentally left during a procedure (header code; choose a more specific subcode).
What is the ICD-10 code for chemical peritonitis?
- T81.61 — Aseptic peritonitis due to foreign substance accidentally left during a procedure (header code; choose a more specific subcode).
What is the ICD-10 code for chlamydial peritonitis?
- A74.81 — Chlamydial peritonitis.
What is the ICD-10 code for congenital peritonitis?
- P78.1 — Other neonatal peritonitis.
What is the ICD-10 code for chronic proliferative peritonitis?
- K65.8 — Other peritonitis.
Is K65.9 billable?
- Yes. K65.9 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can K65.9 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict K65.9 as a principal diagnosis.
Is K65.9 a CC or MCC?
- K65.9 is an MCC (major complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.