K35.209 — Acute appendicitis with generalized peritonitis, without abscess, unspecified as to perforation
Is K35.209 billable?
Yes, but K35.209 is an unspecified code. K35.209 is a valid, billable ICD-10-CM code for encounters from October 1, 2026 through September 30, 2027. However, K35.209 is an unspecified or catch-all code. Payers apply additional scrutiny to unspecified codes and many deny them when the medical record supports a more specific option, so check the documentation before selecting K35.209 — the more specific alternatives are listed below.
K35.209 at a glance
| Code | K35.209 |
|---|---|
| Description | Acute appendicitis with generalized peritonitis, without abscess, unspecified as to perforation |
| Billable | Yes |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
Which MS-DRGs does K35.209 group to?
K35.209 sits in MDC 06 and helps define the logic of 3 MS-DRGs (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.
- 371Major Gastrointestinal Disorders and Peritoneal Infections with MCCmedical
- 372Major Gastrointestinal Disorders and Peritoneal Infections with CCmedical
- 373Major Gastrointestinal Disorders and Peritoneal Infections without CC/MCCmedical
As a secondary diagnosis, K35.209 is a complication or comorbidity (CC), which can move a stay into a higher-paying DRG.
How is K35.209 listed in the Alphabetic Index?
These are the routes through the Alphabetic Index that lead to K35.209. They show the wording a clinician may have documented, which often differs from the Tabular description.
- Appendicitis › with › peritonitis NEC › generalized (pneumococcal) (retrocecal)
- Peritonitis › with or following › appendicitis › generalized (adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion)
- Appendicitis › acute › with › peritonitis NEC › generalized (pneumococcal) (retrocecal)
Inclusion terms
Alternative wording in documentation that is classified to K35.209.
- (Acute) appendicitis with generalized peritonitis NOS
Excludes2 — not included here — inherited from Chapter 11
The conditions below are not part of K35.209, but a patient may have both at the same time. When documentation supports it, K35.209 and the excluded code may both 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)
How long has K35.209 existed?
K35.209 first appears in FY2024.
Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.