ICD-10 Code for Appendicitis

The default ICD-10-CM 2027 code for appendicitis (pneumococcal) (retrocecal) is K37 – Unspecified appendicitis. More specific codes depend on the details documented, as listed in the official index (17 codes, 17 billable).

Main code: K37 – Unspecified appendicitis
Billable: Yes

Index entries for Appendicitis

with
- gangrene – K35.891
  - with localized peritonitis – K35.31
- perforation NOS – K35.32
- peritoneal abscess – K35.33
- peritonitis NEC – K35.33
  - generalized – K35.209
    - with
      - abscess – K35.219
        with perforation or rupture – K35.211
        following rupture or perforation of appendix NOS – K35.211
        without perforation or rupture – K35.210
      - perforation or rupture – K35.201
    - following rupture or perforation of appendix NOS – K35.201
    - without rupture or perforation of appendix – K35.200
  - localized – K35.30
    - with
      - gangrene – K35.31
      - perforation – K35.32
        and abscess – K35.33
  - rupture (with localized peritonitis) – K35.32
acute (catarrhal) (fulminating) (obstructive) (retrocecal) (suppurative) – K35.80
- with
  - gangrene – K35.891
  - peritoneal abscess – K35.33
  - peritonitis NEC – K35.33
    - generalized – K35.209
      - with
        abscess – K35.219
        with perforation or rupture – K35.211
        following rupture or perforation of appendix NOS – K35.211
        without perforation or rupture – K35.210
        perforation or rupture – K35.201
      - following rupture or perforation of appendix NOS – K35.201
      - without rupture or perforation of appendix – K35.200
    - localized – K35.30
      - with
        gangrene – K35.31
        perforation – K35.32
        and abscess – K35.33
- specified NEC – K35.890
  - with gangrene – K35.891
    - with localized peritonitis – K35.31
amebic – A06.89
chronic (recurrent) – K36
exacerbation – see Appendicitis, with, gangrene
gangrenous – see Appendicitis, acute
healed (obliterative) – K36
interval – K36
neurogenic – K36
obstructive – K36
recurrent – K36
relapsing – K36
ruptured NOS (with localized peritonitis) – K35.32
subacute (adhesive) – K36
subsiding – K36
suppurative – see Appendicitis, acute
tuberculous – A18.32

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.