K35.80 Unspecified acute appendicitis

Billable ICD-10-CM code, FY2026. Acts as a Complication or Comorbidity (CC) as a secondary diagnosis.

Applicable to

• Acute appendicitis NOS
• Acute appendicitis without (localized) (generalized) peritonitis

MS-DRG index

Defines the logic of DRG(s) 393-395 in MDC 06.

Approximate ICD-9-CM (GEMs)

• 540.9 Acute appendicitis without mention of peritonitis (approximate)

Code annotations containing back-references to K35.80

Back-references to K35

• Type 1 Excludes: K65 Peritonitis ("peritonitis with or following appendicitis (K35.-)")

Diagnosis Index entries for K35.80

• Appendicitis (pneumococcal) (retrocecal) › acute (catarrhal) (fulminating) (obstructive) (retrocecal) (suppurative)
• Gangrene, gangrenous (connective tissue) (dropsical) (dry) (moist) (skin) (ulcer) › appendix

Nearby codes

• K35.30 Acute appendicitis with localized peritonitis, without perforation or gangrene
• K35.31 Acute appendicitis with localized peritonitis and gangrene, without perforation
• K35.32 Acute appendicitis with perforation, localized peritonitis, and gangrene, without abscess
• K35.33 Acute appendicitis with perforation, localized peritonitis, and gangrene, with abscess
• K35.8 Other and unspecified acute appendicitis
• K35.80 Unspecified acute appendicitis (this code)
• K35.89 Other acute appendicitis
• K35.890 Other acute appendicitis without perforation or gangrene
• K35.891 Other acute appendicitis without perforation, with gangrene