The recently published study by Wang et al revealed that medical expulsive therapy is highly effective for patients with large, distal ureteral stones. The study was well conducted and overcame limitations of the previous randomized trial (Spontaneous Urinary Stone Passage Enabled by Drugs [SUSPEND]) by Pickard et al, which was underpowered to show an effect in this population. However, as an unintended consequence, the study by Wang et al may lead more providers to choose a computed tomography (CT)–first approach for flank pain to identify stone size and location and guide treatment decisions to include tamsulosin. Here, we discuss an alternative: using ultrasonography in lieu of CT and prescribing medical expulsive therapy for hydronephrosis when stone size and location are unknown.

An ultrasonography-first approach to the diagnosis of symptomatic kidney stones has been proposed by multiple thought leaders, as well as the American College of Emergency Physicians’ Choosing Wisely campaign, after the success of diagnostic ultrasonography in the multicenter randomized trial by Smith-Bindman et al, in which diagnosis of nephrolithiasis often relied on detection of hydronephrosis without direct stone visualization.

In the context of medical expulsive therapy, the outstanding issue in regard to an ultrasonography-first approach is whether to treat hydronephrosis patients without visualized stones. Extending the treatment of medical expulsive therapy to all stones would dilute the strong effect demonstrated in the study by Wang et al, in which the number needed to treat to provide a benefit was 5 patients among those with large, distal stones. To estimate the effectiveness of medical expulsive therapy among all cases of hydronephrosis, we estimate number needed to treat with the following back-of-the envelope calculation: If we conservatively assume half of stones are distal (our local data show that approximately 60% are distal) and 10% to 20% are larger than 5 mm, consistent with previous literature, approximately 5% to 10% of all stones would benefit from medical expulsive therapy. With this estimate, a number needed to treat for medical expulsive therapy to provide benefit in patients with hydronephrosis on ultrasonography would be in the range of 50 to 100. Although hydronephrosis can also be caused by tumors, strictures, or pregnancy, these instances are rare enough that they should not substantially affect the number needed to treat.

The range of the number needed to treat, 50 to 100, approaches the effectiveness of other common medications such as aspirin for cardiovascular protection in patients with previous cerebrovascular or cardiovascular events. Effectiveness of medical expulsive therapy is likely even higher in patients with moderate or severe hydronephrosis, who are approximately 2.5 times more likely to have stones larger than 5 mm. Because tamsulosin has relatively few adverse effects (namely, dizziness and orthostatic hypotension) and is now a generic drug, it should be strongly considered for patients who receive a diagnosis of hydronephrosis on ultrasonography, especially among the nonelderly, for whom adverse effects are limited.

Thus, we are in favor of an ultrasonographic approach and incorporation of medical expulsive therapy as part of standard conservative therapy, especially when moderate or severe hydronephrosis is observed on ultrasonography.