MET found safe, efficacious in pregnant stone patients

July 1, 2015

New study data suggest an answer to the problem of managing stones in pregnant women.

New Orleans-Managing stones in pregnant women can be challenging because many of the imaging technologies used to localize the stones, and the primary therapies to remove them or ease symptoms, may carry risks and/or side effects that might be amplified by the pregnancy. 

A retrospective study of 28 patients conducted by Mayo Clinic researchers suggests that medical expulsive therapy employing tamsulosin (Flomax), an alpha-1-adrenergic receptor antagonist, can benefit pregnant women with minimal risk to either mother or child, as reported at the AUA annual meeting in New Orleans. 

"Our study suggests that tamsulosin as medical expulsive therapy for symptomatic stones in pregnant patients is safe and may increase stone passage rates," George Bailey, MD, a urology resident at Mayo Clinic, Rochester, MN, told Urology Times.

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"Larger cohorts will be helpful in further defining the role of tamsulosin for pregnant stone formers, but our initial experience indicates that the option of tamsulosin medical expulsive therapy should be part of the discussion when physicians counsel symptomatic pregnant stone formers, especially when symptoms are severe enough that they are considering things like stent placement, ureteroscopy, or percutaneous nephrostomy tube," said Dr. Bailey, who worked on the study with Amy Krambeck, MD, and colleagues.

To arrive at these conclusions, the Mayo team retrospectively identified 28 pregnant women with documented tamsulosin therapy for symptomatic urolithiasis. Of these women, 20 (71%) had urolithiasis documented by imaging and 23 (82%) had documented hydronephrosis. The median treatment period tamsulosin was 3 days (range, 1 to 110). Three patients (11%) were treated in their first trimester, 10 (36%) in their second, and 18 (67%) in their third trimester. Several patients had more than one course of therapy.

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Dr. Bailey observed that the pattern of symptomatic stone formation in pregnant women seen in the study was somewhat typical.

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"Pregnant women have the same risk of stone formation as their non-pregnant peers. Most pregnant women who present with symptomatic nephrolithiasis will do so in the second or third trimester. That trend was seen in our patient population," he said.

He said that one of the challenges in treating stones in pregnant women is that the gold standard for imaging and localizing stones is computed tomography.

"Obviously, radiation exposure is something we try to avoid in pregnant women. Often pregnant women with flank pain will undergo ultrasound imaging, which, unfortunately, has low sensitivity and specificity for stones. Women in our series were treated with tamsulosin, 0.4 mg/d, until the stone passed or their pain resolved," said Dr. Bailey. The study reported that the median duration of in-utero exposure to the agent was 3 days.

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Refractory renal colic requiring surgical intervention presented in eight patients (29%). This included one who required ureteral stent placement, one who required ureteroscopy without stent placement, five who required ureteroscopy with stent placement, and one who required a nephrostomy tube.

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The study matched the treatment cohort 2:1 with a group of pregnant women with symptomatic urolithiasis who did not get tamsulosin and found no significant differences between the two groups. The mean maternal age of the study group was 28.4 (SD, 4.15) years with the mean gestational age of the child being 38.1 weeks. Six infants (22%) were born preterm. All infants were considered appropriate for gestational age, and there were no cases of spontaneous abortion, intrauterine demise, or congenital anomalies.

Dr. Bailey responded to a question about the size of the study, saying that it was not unusual.

"Practitioners are understandably hesitant to give medications without a proven safety record to pregnant women, which makes even retrospective studies difficult to conduct,” he said. “Many investigations of medication exposure in pregnant women start with small, retrospective studies. The sample size of this study reflects those challenges and is on par with other initial single institution investigations into medication exposure risk during pregnancy.”

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