ICD-10 Code for Peritonitis

The default ICD-10-CM 2027 code for peritonitis (adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion) is K65.9 – Peritonitis, unspecified. More specific codes depend on the details documented, as listed in the official index (35 codes, 33 billable).

Main code: K65.9 – Peritonitis, unspecified
Billable: Yes

Index entries for Peritonitis

with or following
- abscess – K65.1
- appendicitis
  - with perforation or rupture – K35.32
  - generalized – K35.209 – see also Appendicitis
  - localized – K35.30 – see also Appendicitis
- diverticular disease (intestine) – K57.80
  - with bleeding – K57.81
  - large intestine – K57.20
    - with
      - bleeding – K57.21
      - small intestine – K57.40
        with bleeding – K57.41
  - small intestine – K57.00
    - with
      - bleeding – K57.01
      - large intestine – K57.40
        with bleeding – K57.41
  - ectopic or molar pregnancy – O08.0
acute (generalized) – K65.0
aseptic – T81.61 (header)
bile, biliary – K65.3
chemical – T81.61 (header)
chlamydial – A74.81
complicating abortion – see Abortion, by type, complicated by, pelvic peritonitis
congenital – P78.1
chronic proliferative – K65.8
diaphragmatic – K65.0
diffuse – K65.0
diphtheritic – A36.89
disseminated – K65.0
due to
- bile – K65.3
- foreign
  - body or object accidentally left during a procedure (instrument) (sponge) (swab) – T81.599 (header)
  - substance accidentally left during a procedure (chemical) (powder) (talc) – T81.61 (header)
- talc – T81.61 (header)
- urine – K65.8
eosinophilic – K65.8
- acute – K65.0
fibrocaseous (tuberculous) – A18.31
fibropurulent – K65.0
following ectopic or molar pregnancy – O08.0
general (ized) – K65.0
gonococcal – A54.85
meconium (newborn) – P78.0
neonatal – P78.1
- meconium – P78.0
pancreatic – K65.0
paroxysmal, familial – E85.0
- benign – E85.0
pelvic (see also, if applicable, Abscess, abdominopelvic)
- female – N73.5
  - acute – N73.3
  - chronic – N73.4
    - with adhesions – N73.6
- male – K65.0
periodic, familial – E85.0
proliferative, chronic – K65.8
puerperal, postpartum, childbirth – O85
purulent – K65.0
septic – K65.0
specified NEC – K65.8
spontaneous bacterial – K65.2
subdiaphragmatic – K65.0
subphrenic – K65.0
suppurative – K65.0
syphilitic – A52.74
- congenital (early) – A50.08 – K67 [manifestation]
talc – T81.61 (header)
tuberculous – A18.31
urine – K65.8

How to choose the right code

Start with the main term, then pick the indented subterm that matches the documentation (type, cause, site, laterality, episode of care). Always confirm the code in the tabular list: follow its Excludes1/Excludes2, “code first” and “use additional code” notes, and add a 7th character where required.

Source: CDC/NCHS ICD-10-CM FY2027 alphabetic index.