Low-Dose CT Used Evaluate Flank Pain in Pregnant Women

Fetal irradiation concerns have traditionally prohibited the use of computed tomography (CT) imaging in this population. Researchers recently reported their findings using low-dose CT in the evaluation of pregnant patients with refractory flank pain.

In a recent study by researchers from the University of Tennessee Medical Center (Knoxville, TN, USA) of patients who underwent low-dose CT, an evaluation of the urinary tract for suspected urinary tract stones was performed. The diagnosis and treatment of the pregnant patient presenting with acute renal colic remain a troublesome problem for the urologist. Traditionally, this has led to an ultrasound study, which if nondiagnostic, led to a three-shot intravenous urogram. If a stone was present, then one of three approaches was most commonly selected: watchful waiting, ureteral stent placement, or percutaneous nephrostomy.

Neither the diagnosis of the condition nor the treatment was truly satisfactory. Ultrasound failed to show a stone in upwards of 50% of patients who had a stone; the subsequent intravenous urogram was also often nondiagnostic. Similarly, treatment with ureteral stent or nephrostomy tube was less than optimal as this approach required changing of the stent or tube every six to eight weeks during the pregnancy to prevent at times, massive encrustation.

Currently, this has all changed for the better given the development of low-dose CT scanning and ureteroscopy. In this study, the investigators, using low dose CT imaging, averaging 0.7 rads (i.e., similar to a three-shot intravenous urogram) were able to diagnose urolithiasis in 13 of 20 pregnant patients presenting with acute flank pain. This radiation dose is one-third to one-fourth the dose of a standard CT scan. The seven patients without stones were managed with analgesics and anti-emetic therapy; none were later found to have a stone. Among the 13 with stones, the researchers most commonly selected either expectant therapy (four of six passed their stone) or ureteroscopic extraction (five cases), which was successful in all cases. Of note, in the two patients managed with a ureteral stent, the aggregate number of subsequent stent exchanges before delivery was five. In retrospect, the investigators believed that both of these patients should also have been managed ureteroscopically.

All of their patients were in the second and third trimester. For patients in the far more radiosensitive first trimester, the researchers reported that they would recommend ultrasonography first before considering low-dose CT scanning, and even then they would recommend that the individual would ask her radiologist to calculate the estimated dose to the fetus before proceeding, as this should be < 1 rad.

The study was published in the November 2007 issue of the Journal of Endourology.


Related Links:
University of Tennessee Medical Center