I’ve seen many patients present to the E.D. in severe pain from kidney stones. Renal colic is a common and recurrent condition; it affects over a million people each year in the U.S. and accounts for approximately 1 percent of admissions.1
Diagnosing kidney stones in patients who present with renal colic is often performed with tomography (CT). In the past, Intravenous Urography (IVU) was used. While CT and IVU are accurate diagnostic tests and define clearly the size, shape, and position of uric acid stones, they also present a number of factors that would discourage use, including the potential risks of exposing patients to repeated doses of ionizing radiation.
In its 2011 Guidelines on Urolithiasis, the European Association of Urology (EAU) calls for ultrasound to be used as the primary imaging procedure. The guidelines state, “it is a safe (no risk of radiation), reproducible and inexpensive method of urinary stone detection.”2 The EAU notes that ultrasonography can detect stones in the calices, pelvis, pyelo-ureteric junction and vesicoureteric junction, and dilatation of the upper urinary tract. For renal stones greater than 5 mm, ultrasound offers a sensitivity of 96% and a specificity of 100%. For location of all stones, ultrasound’s sensitivity and specificity was 78% and 31% respectively.3, 4
We need to correctly diagnose patients as safely and as efficiently as possible. It is for this reason that I turn to ultrasound whenever I suspect a patient is presenting with renal colic. CT scans can be helpful in many scenarios, and there is an ongoing place for this modality. But evidence continues to mount that using ultrasound first for conditions such as renal colic makes good clinical sense without needlessly exposing patients to medical radiation.
1 Wolf JS. Nephrolithiasis: Acute Renal Colic. Medscape Reference, 2011. Available at http://emedicine.medscape.com/article/437096-overview
2 Turk C, Knoll T, Petrik A, et. al. Guidelines on Urolithiasis, European Association of Urology. 2011. Available at http://www.uroweb.org/guidelines/online-guidelines
3 Varma G, Nair N, Salim A, et al. Investigations for Recognizing Urinary Stone. Urol Res. 2009;37(6):349-52. http://www.ncbi.nlm.nih.gov/pubmed/19826802
4 Middleton WD, Dodds WJ, Lawson TL, et al. Renal calculi: sensitivity for detection with US. Radiology.
1988;167(1):239-44. http://www.ncbi.nlm.nih.gov/pubmed/3279456
