K35.80 — Unspecified acute appendicitis
Is K35.80 billable?
Yes, but K35.80 is an unspecified code. K35.80 is a valid, billable ICD-10-CM code for encounters from October 1, 2026 through September 30, 2027. However, K35.80 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 K35.80 — the more specific alternatives are listed below.
More specific alternatives
K35.80 at a glance
| Code | K35.80 |
|---|---|
| Description | Unspecified acute appendicitis |
| Billable | Yes |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
Which MS-DRGs does K35.80 group to?
K35.80 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.
- 393Other Digestive System Diagnoses with MCCmedical
- 394Other Digestive System Diagnoses with CCmedical
- 395Other Digestive System Diagnoses without CC/MCCmedical
As a secondary diagnosis, K35.80 is a complication or comorbidity (CC), which can move a stay into a higher-paying DRG.
How is K35.80 listed in the Alphabetic Index?
These are the routes through the Alphabetic Index that lead to K35.80. They show the wording a clinician may have documented, which often differs from the Tabular description.
- Appendicitis › acute (pneumococcal) (retrocecal)
- Gangrene, gangrenous › appendix (connective tissue) (dropsical) (dry) (moist) (skin) (ulcer)
Inclusion terms
Alternative wording in documentation that is classified to K35.80.
- Acute appendicitis NOS
- Acute appendicitis without (localized) (generalized) peritonitis
Excludes2 — not included here — inherited from Chapter 11
The conditions below are not part of K35.80, but a patient may have both at the same time. When documentation supports it, K35.80 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 K35.80 existed?
K35.80 has been in ICD-10-CM since at least FY2016, the earliest fiscal year on record here.
Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.