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AFHSC Surveillance Case Definitions
FINAL July 2015
Case Definition and Incidence Rules
For surveillance purposes, a case of urolithiasis or “urinary stones” is defined as:
One hospitalization with any of the defining diagnoses of urolithiasis (see ICD9 and ICD10
code lists below) in the primary diagnostic position; or
One outpatient medical encounter with any of the defining diagnoses of urolithiasis (see
ICD9 and ICD10 code lists below) in the primary diagnostic position.
Incidence rules:
For individuals who meet the case definition:
The incidence date is considered the date of the first inpatient or outpatient medical
encounter that includes a case defining diagnoses of urolithiasis. (continued on next page)
UROLITHIASIS (URINARY STONES)
Includes Nephrolithiasis (Renal Calculi, Kidney Stones), Ureterolithiasis (Ureter Calculi)
and Cystolithiasis (Bladder Calculi)
Background
This case definition was developed by the Armed Forces Health Surveillance Center (AFHSC) for the
purpose of epidemiological surveillance of a condition important to military-associated populations.
Urinary stones can decrease operational effectiveness (e.g., lost duty days, medical evacuation) and
may be precipitated by environmental stressors common to military training and operational settings.
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This case definition includes criteria for incident and recurrent case identification.
Clinical Description
Urolithiasis is the formation of urinary calculi (“stones”) in the urinary system. Nephrolithiasis or
“kidney stones” refers to calculi or stones in the kidney and is the most common form of urinary tract
stone disease. Ureter and bladder calculi almost always originate in the kidneys. Urinary stones are
most often caused by decreased urine volume or by increased excretion of stone-forming components
such as calcium, oxalate, urate, cystine, xanthine, and phosphate. Factors predisposing an individual to
stone formation include reduction in fluid intake, increased exercise with dehydration, medications that
cause hyperuricemia and a history of gout.
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The colic-type pain associated with the transit of kidney
stones through the ureter is often severe radiating to the back and groin. The majority of stones pass in
48 hours. Treatment requires a combined medical and surgical approach and depends upon the
location of the stone, the extent of obstruction, and the function of the affected kidney.
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,
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1
Armed Forces Health Surveillance Center. Urinary Stones, Active Component, U.S. Armed Forces,
2001-2010. Medical Surveillance Monthly Report (MSMR). 2011December; Vol 18(No12):6-9.
2
Kidney stones in adults. National Institute of Diabetes and Digestive and Kidney Diseases.
http://kidney.niddk.nih.gov/kudiseases/pubs/stonesadults/index.htm. Accessed Jan. 5, 2010.
3
Braunwald, E., Fauci, A., Longo, D. et al. 2008. Harrison’s Principles of Internal Medicine. 17th ed.
United States: McGraw-Hill Professional.
4
Worcester EM, et al. Nephrolithiasis. Primary Care: Clinics in Office Practice. 2008; 35:369.
