Low Dose Computed Tomography For The Evaluation Of Flank Pain In The Pregnant Population

Main Category: Urology / Nephrology
Also Included In: MRI / PET / Ultrasound
Article Date: 25 Jan 2008 - 0:00 PDT

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UroToday.com- The diagnosis and treatment of the pregnant patient presenting with acute renal colic remain a vexing problem for the urologist. Classically, this has led to an ultrasound study, which if nondiagnostic, led to a 3 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 6-8 weeks during the pregnancy in order to prevent at times, massive encrustation. Today, this has all changed for the better given the advent of low dose CT scanning and ureteroscopy. In this article, the authors, using low dose CT imaging, averaging 0.7 rads (i.e. similar to a 3 shot intravenous urogram) were able to diagnose urolithiasis in 13 of 20 pregnant patients presenting with acute flank pain. This radiation dose is 1/3rd to 1/4th 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 authors most commonly selected either expectant therapy (4 of 6 passed their stone) or ureteroscopic extraction (5 cases) which was successful in all cases. Of note, in the 2 patients managed with a ureteral stent, the aggregate number of subsequent stent exchanges prior to delivery was 5! In retrospect, the authors feel that both of these patients should also have been managed ureteroscopically. One caveat: all of their patients were in the 2nd and 3rd trimester. For patients in the far more radiosensitive first trimester, I would recommend ultrasonography first before considering low dose CT scanning and even then I would ask my radiologist to calculate the estimated dose to the fetus before proceeding as this should be < 1 rad.

W. M. White, N. B. Zite, J. Gash, W. B. Waters, W. Thompson, and F. A. Klein

J. Endourol. 21(11):1255- 1260, November 2007
doi:10.1089/end.2007.0017

Reported by UroToday.com Contributing Editor Ralph V. Clayman, M.D

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