Radiology Coding Alert

'Without peritonitis' will lead you to an unspecified code.

When patients present with abdominal pain, your radiologist's finding may be "acute appendicitis." Here's how to handle coding this diagnosis under ICD-9-CM and ICD-10-CM.

ICD-9 code: 540.9 (Acute appendicitis; without mention of peritonitis)

ICD-10 codes: K35.80 (Unspecified acute appendicitis), K35.89 (Other acute appendicitis)

Acute appendicitis refers to an inflammation of the appendix, a small, one-ended, tube-like structure attached to the large intestine. Additional diagnosis coding options reference peritonitis, an inflammation of the abdominal cavity's lining (the peritoneum). Peritonitis can be fatal unless treated quickly with antibiotics.

ICD-9 coding rules: Under ICD-9 2012, you report 540.9 for acute appendicitis when the physician does not indicate the presence of peritonitis.

ICD-10 changes: ICD-10 offers two codes that cross to 540.9: K35.80 (unspecified) and K35.89 (other). Notes under K35.80 tell you the code is appropriate for "Acute appendicitis without (localized) (generalized) peritonitis" and "Acute appendicitis NOS [not otherwise specified]."

Coder Tips: Check the index and tabular list before choosing your final code. For example, if documentation shows the appendix has ruptured, you'll need to choose between K35.2 (Acute appendicitis with generalized peritonitis) and K35.3 (Acute appendicitis with localized peritonitis).

Remember: When ICD-10 goes into effect on Oct. 1, 2013, you should apply the code set and official guidelines in effect for the date of service reported. Learn more at www.cms.gov/ICD10/ and www.cdc.gov/nchs/icd/icd10cm.htm#10update.