Low-dose computed tomography for the evaluation of flank pain in the pregnant population

BACKGROUND: Evaluation of the pregnant patient with suspected renal colic is complex. Fetal irradiation concerns have traditionally prohibited the use of CT in this population. We report our institution's experience using low-dose CT in the evaluation of pregnant patients with refractory flank pain. PATIENTS AND METHODS: A retrospective review of all patients who underwent low-dose CT evaluation of the urinary tract for suspected urinary tract stones was performed. Data obtained included gestational age, urinalysis and ultrasonography results, CT findings, and calculated fetal radiation exposure. RESULTS: Between April 2004 and December 2006, 20 patients with an average gestational age of 26.5 weeks presented to our institution with acute, refractory flank pain consistent with a diagnosis of urolithiasis. All patients underwent renal ultrasonographic evaluation before unenhanced CT of the abdomen and pelvis using a low-dose protocol. The average radiation exposure was 705.75 mrads (range 210-1372; SD +/- 338.66 mrads). Of the 20 patients, CT demonstrated urinary stones (1-12 mm) in 13. Of those patients with documented stones, 4 were treated conservatively, 2 underwent intrapartum stent placement, 5 had ureteroscopy with stone extraction, and 2 were treated postpartum. CONCLUSION: Low-dose CT is highly sensitive and specific for the detection of urinary calculi in the pregnant population. CT confers a low risk of fetal harm and can improve patient care when used judiciously.