Revenue Cycle Insider

Question: A surgeon documents “acute appendicitis” and explicitly states that the patient does not have peritonitis. The patient’s CT scan shows an enlarged, inflamed appendix with no evidence of perforation, abscess, or rupture. Which ICD-10-CM code is most appropriate?

Answer: To properly code acute appendicitis, pay attention to both what the provider rules out and what they confirm.

You may be tempted to default to K35.80 (Unspecified acute appendicitis) because the provider does not describe complications, but this code applies only when the medical record lacks sufficient clinical detail. In this case, the provider clearly states that the appendicitis is acute and uncomplicated, which supports assignment of a more specific diagnosis code.

Appendicitis code sets that include peritonitis, such as K35.20- (Acute appendicitis with generalized peritonitis, without abscess) or K35.21- (Acute appendicitis with generalized peritonitis, with abscess), are inappropriate because the provider explicitly excluded peritoneal involvement.

In this case, refer to the K35.3- (Acute appendicitis with localized peritonitis) code set in accordance with the imaging results and the provider’s assessment. Since the patient’s record confirms inflammation of the appendix without rupture, abscess, or peritoneal involvement, K35.30 (Acute appendicitis with localized peritonitis, without perforation or gangrene) is the best applicable code.

Keep in mind: Appendicitis codes are highly dependent on documented complications. Coders should verify whether the provider explicitly identifies or excludes peritonitis, perforation, gangrene, or abscess before finalizing code selection.

For future claims: If subsequent documentation describes disease progression, such as perforation or development of localized or generalized peritonitis, revisit the K35.- code set to determine whether a different code better reflects the patient’s condition.

Michelle Falci, BA, M Falci Communications LLC