Low-dose CT stone detection: Safe during pregnancy

Urinary stone formation is common during pregnancy, and many women spontaneously pass their stones. However, clinicians have been loath to use imaging to confirm stone presence in women with unresolved symptoms for fear of exposing the fetus to radiation.

"You don't know if someone has a stone, and if you condemn them to percutaneous nephrostomy or a stent early in their pregnancy, it can be a huge problem for the rest of the pregnancy," senior author Frederick A. Klein, MD, chief of the division of urology and urologic oncology, told Urology Times. "You have to change the stent every 4 to 6 weeks, and the tube every 4 weeks. Then it turns out they didn't have stones when they came in with renal colic.

Dr. Klein and colleagues performed a retrospective review focusing on the peripartum outcomes of 46 pregnant women (mean age, 26.2 years) who presented with intractable flank pain suggestive of urolithiasis between November 2004 and June 2006. Most of the women were in their second trimester or later, although three were in their first trimester. All demonstrated negative or equivocal findings on renal sonography, and all underwent low-dose computed tomography (LDCT) at a mean calculated fetal radiation dose of 945 mrads (±548 mrads).

LDCT identified renal or ureteral stones in 29 women (63%). Consequently, 11 women were managed conservatively, 14 underwent ureteroscopy, and four were implanted with stents and treated postpartum. None of the 29 patients incurred complications during treatment or experienced preterm labor. The balance of the women were successfully managed antepartum. All delivered babies apparently unaffected by exposure to LDCT.

As a result, use of LDCT is now standard protocol at the University of Tennessee Medical Center for pregnant women presenting with renal colic, said Dr. Klein, who discussed the study data at the AUA annual meeting in Chicago.

"Our radiologist is really tuned in to LDCT," he explained. "In the old days, [these patients would receive] three shots of intravenous pyelogram, 500 mrad; this was 900 mrad. It's not that big a difference, and the risk is minimal. It's all a function of calculating the radiation dose as low as possible to give us the information we need: the sensitivity and specificity was 90-plus percent.

"We recommend LDCT during pregnancy when patients are thought to have ureteral colic," Dr. Klein said. "It determines who goes to the OR-and who doesn't."

ModernMedicine NETWORK

NEWS & UPDATES
Hypertension and obesity have been linked to risk of ureteral calculi. A diet known as DASH can help patients lower their stone risk. Read about it at: http://www.urologytimes.com/DASH

EDUCATION
Stay current with updated AUA-EAU guidelines for managing ureteral calculi. See: http://www.urologytimes.com/calculi