Invited Commentary • Authors' Response

Abstract

Acute pain due to an obstructing ureteral calculus is a very common problem, with a lifetime prevalence in the United States of up to 12%. Renal colic is therefore one of the most common conditions treated in emergency departments (1,2). An obstructing ureteral calculus may mimic, and be mimicked by, innumerable abdominal and pelvic conditions. Patient history, physical examination, and laboratory tests cannot help confirm or exclude the diagnosis with high enough accuracy (1,2). In particular, hematuria testing has a sensitivity of 81%–84% (3,4) and a specificity and negative predictive value of 48% and 65%, respectively (4), and numerous alternative conditions commonly produce hematuria as well. First introduced in 1995 by Smith et al (5), unenhanced CT (followed by unenhanced helical CT and unenhanced multi–detector row CT) has become the imaging modality of choice for the evaluation of patients with flank pain. Unenhanced CT is faster, safer, and more accurate than excretory urography and does not carry the risk of a contrast material reaction. As a result, excretory urography is almost never performed for this indication nowadays. Other advantages of unenhanced helical CT include more precise sizing and localizing of stones, determination of overall stone burden, and a comparable or reduced radiation dose (1,2,5–7). The examination can also be used to guide subsequent patient treatment based on the size and location of a ureteral stone. The most important advantage of unenhanced helical CT may be its capacity to reveal alternative diagnoses, both within and outside the genitourinary tract. Many of these diagnoses would not be evident at radiography or excretory urography (8–10). Rucker et al (11) beautifully document a broad spectrum of alternative diagnoses discovered at unenhanced helical CT over a 2-year period in patients who were initially suspected of having an obstructing ureteral stone. These alternative diagnoses include common disorders such as pyelonephritis, appendicitis, and ovarian lesions, uncommon diagnoses such as renal lymphoma and ascending colonic diverticulitis, and rare diagnoses such as acute spontaneous splenic rupture and hemorrhage due to a renal arteriovenous malformation. Some relatively recent cases from our S28 October 2004 RG f Volume 24 ● Special Issue