Expulsive therapy less costly than surgery for renal colic

Ann Arbor, MI-Medical expulsive therapy for the initial management of uncomplicated acute renal colic, with eventual uretereoscopy if needed, is associated with less resource utilization and lower 6-week costs than early surgery, say researchers from the University of Michigan, Ann Arbor.

Although numerous randomized controlled trials have shown that medical expulsive therapy facilitates renal stone transport, little has been published about health care resource use among patients on medical expulsive therapy, said first author Robert Matthew Smith, MD, a fourth-year house officer in the department of urology at the University of Michigan.

If patients offered a trial of medical expulsive therapy have more frequent encounters with the health care system, would it mitigate the benefits of medical expulsive therapy; namely, sparing them from the risks of active stone removal? To help answer this question, Dr. Smith and colleagues compared the resource utilization and costs per episode of early surgical intervention with a strategy of medical expulsive therapy for patients with urinary stone disease.

As reported at the 2012 AUA annual meeting in Atlanta, the authors used medical claims data obtained from MarketScan to identify a cohort of 9,820 adults with incident emergency department (ED) claims for urinary stone disease between 2002 and 2006. They determined whether each patient received ureteroscopy within 3 days of presentation or a trial of medical expulsive therapy.

Patients were followed for 6 weeks, during which time their frequency of ED revisits and hospital admissions were measured, and the total and component episode payments made on their behalf were assessed.

In all, 7,404 patients had early surgery and 2,416 underwent initial medical expulsive therapy. Twenty-four percent of the group that underwent initial medical expulsive therapy subsequently required surgery.

Costs higher with surgery group

“The overall 6-week health care expenditures were significantly higher in the surgery group, both in our unadjusted and adjusted analysis,” said Dr. Smith, who worked on the study with John Hollingsworth, MD, MS, and colleagues. After adjustment for age, gender, socioeconomic status, and region of residence, 6-week expenditures were $9,897 in the surgery group versus $4,052 in the medical expulsive therapy group.

One limitation to this observational analysis is that only known confounders can be used to adjust for patient differences.

“It’s entirely possible that there are unmeasured patient characteristics, like stone size and location within the ureter, that could be significantly different within our groups,” he said. “To the extent that these characteristics are different, the true association between treatment and outcome could be distorted.”

To address the potential for confounding, the authors performed an instrumental variable analysis, which allows for pseudorandomization within observational data, balancing measured and unmeasured confounders and estimation of the treatment effect in the marginal patient.

The marginal patient is one whose treatment choice is not influenced by patient characteristics, explained Dr. Smith.

“The marginal patient is not the patient with a large proximal stone who will likely get surgery nor is a patient with a small distal stone who will more likely be treated conservatively,” he said. “The marginal patient is the patient whose treatment choice is less clear; for example, a patient with a mid-size ureteral stone.”

The day of the week that the patient presented to the ED was identified as the candidate instrumental variable, as the number of ED visits did not vary by day of the week and patient characteristics were unaffected by the day of presentation to the ED. However, patients who presented over the weekend were significantly more likely to be offered medical expulsive therapy than those who presented earlier in the week.

The instrumental variable analysis showed no difference in the rate of hospitalization between the two groups, but medical expulsive therapy increased the likelihood of ED revisits by 29% (p<.0001).

“The overall 6-week expenditures were actually 10 times lower for those patients offered medical expulsive therapy versus surgery,” Dr. Smith said.