Flank pain due to urolithiasis is a common problem in patients presenting to emergency departments. Radiology plays a vital role in the work-up of these patients. Many modalities can be used, including ultrasonography, nuclear medicine, and the traditionally used techniques of intravenous urography and conventional radiography. The development of nonenhanced computed tomography (CT) (single- or multi- detector row helical) has provided a means to enable detection and characterization of urolithiasis with unprecedented sensitivity, specificity, and accuracy while yielding important information for treatment planning, including the size and location of calculi. This technique can also help detect causes for flank pain outside the genitourinary tract. However, close attention must be paid to all aspects of the CT study to prevent misdiagnoses.
Flank pain due to urolithiasis is a common problem in patients presenting to emergency departments. Radiologic imaging has always had a primary role in the work-up of these patients. Traditionally, evaluation consisted of conventional radiography followed by intravenous urography (IVU). These techniques could be used to help detect calculi and identify the point of obstruction and its severity. With the advent of ultrasonography (US), those patients who could not safely undergo IVU (ie, patients with acute renal failure, pregnant patients) could be evaluated for secondary signs of obstruction (ie, hydronephro-sis). In patients with acute renal failure or severe allergy to iodinated contrast material, nuclear medicine examinations could alternatively be used to provide information on renal function. These techniques have their limitations.
In the past several years, thin-section nonenhanced computed tomography (CT) has evolved, especially with the development of single-detector row helical CT and, later, multi-detector row CT, as a means of rapid examination of patients suspected of having urolithiasis but without the limitations of radiography, IVU, US, or nuclear medicine. In many institutions, nonenhanced CT has largely supplanted IVU as the primary modality for evaluation of these patients. Nonenhanced CT can help identify calculi and their location, determine their size, and guide management. However, questions remain regarding the optimal use of this technique because of concerns about radiation exposure and cost.
In this article, we will review the state of the art in diagnosing flank pain due to suspected urolithiasis. We will summarize the current state of the art on the use of nonenhanced CT and provide information on techniques and relevant findings. The role of the different imaging modalities in various patient subgroups will also be examined. The issues of radiation exposure and cost will be briefly examined.