As most ED providers know, the term “kidney stone” is often inaccurate. Symptomatic patients typically present with stones not in the kidney itself but stuck at nature’s bottlenecks, i.e. the pelvic brim, ureteropelvic junction (UPJ), or most commonly the ureterovesical junction (UVJ)
Controversy exists regarding the optimal evaluation of nephroureterolithiasis. A non-contrast CT is often employed to diagnose stones, their size, location and associated ureterohydronephrosis, as well as to rule out other causes of pain. Finding the stone is crucial to prognosis, as stones that have passed into the bladder are passed nearly 100% of the time. In contrast, more proximally impacted stones may take longer to pass or may cause obstruction, infection, or intractable pain necessitating intervention.
The modern diagnostic approach is a prone noncontrast CT. Prone scanning helps delineate impacted UVJ stones from those layering posteriorly in the bladder near the UVJ. Pictured above is an impacted left UVJ stone, just adjacent to the bladder.
Pitfalls in locating stones in the distal ureters and bladder include phleboliths in pelvic veins and calcified seminal vesicles (seen above - calcified structure on the patient's right just posterior to the bladder).
References
Vaswani K, El-dieb A, Vitellas K, Bennett W, Bova J. Ureterolithiasis: classic and atypical findings on unenhanced helical computed tomography. Emergency Radiology 2002; 9: 60– 66.
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This "EM Lightbox" case was authored by guest blogger, Dr. Eric Silman.
