The ICD-9 code range APPENDICITIS for 540-543 is medical classification list by the World Health Organization (WHO).
Acute appendicitis
Acute appendicitis with generalized peritonitis
Acute appendicitis with peritoneal abscess
Acute appendicitis without mention of peritonitis
Appendicitis, unqualified
Other appendicitis
Other diseases of appendix
Hyperplasia of appendix (lymphoid)
Other and unspecified diseases of appendix