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AFHSB Surveillance Case Definitions
FINAL October 2016
Case Definition and Incidence Rules - Appendicitis
For surveillance purposes, a case of appendicitis is defined as:
One hospitalization with a case defining diagnosis of appendicitis (see ICD9 and ICD10
code lists below) in any diagnostic position; or
One outpatient medical encounter with a case defining diagnosis of appendicitis (see
ICD9 and ICD10 code lists below) in the primary or secondary diagnostic position;
AND one case defining Current Procedure Terminology (CPT) indicative of an
appendectomy or other surgical procedure involving the appendix (see code list below)
in any diagnostic position.
Incidence rules:
For individuals who meet the case definition:
The incidence date is considered the date of the first hospitalization or outpatient
medical encounter that includes a defining diagnosis of appendicitis
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APPENDICITIS
Includes Appendectomy
Background
This case definition was developed by the Armed Forces Health Surveillance Branch (AFHSB) for the
purpose of epidemiological surveillance of appendicitis and appendectomies among the active and
reserve components of the U.S. Armed Forces.
1
The burden of appendicitis on the Military Health
System is significant. Between 2002 and 2011 there were 31,610 cases of appendicitis and 30,183
appendectomies. Onset of the condition is unpredictable and often sudden, so its occurrence in
members of the U.S. Armed Forces can be disruptive, particularly in the deployed setting.1
Clinical Description
The appendix is a small, blind-ended tube connected to the large intestine near its junction with the
small intestine. Inflammation of the appendix, or appendicitis, can occur as a result of obstruction (i.e.,
by fecal material, a foreign object, or swelling of lymphoid tissue) or from infection; however, in most
cases, the etiology is unknown. Typical symptoms include mild, central abdominal pain that progresses
to sharp, severe pain in the lower right quadrant of the abdomen. The pain is often accompanied by
nausea, vomiting, diarrhea, and fever. Left untreated, an inflamed appendix can rupture leading to
peritonitis and sepsis. As such, appendicitis is a potentially life threatening condition that requires
immediate medical intervention. Treatment is prompt surgical removal of the appendix, a procedure
known as appendectomy.1,
2
1
Armed Forces Health Surveillance Center. Appendicitis and Appendectomies, Active and Reserve
Components, U.S. Armed Forces, 2002-2011. Medical Surveillance Monthly Report (MSMR). 2012
Dec; 19(12): 7-12.
2
Detmer DE, Nevers LE, Sikes ED Jr. Regional results of acute appendicitis care. JAMA.
1981;246:1318-1320.
