Objective: Prostaglandin inhibitors, mostly diclofenac, are currently first-choice therapy for ureteral colic, their main action being reduction of intrapelvic pressure and diuresis. We hypothesized that diclofenac, by increasing tubular reabsorption, can delay excretion of contrast medium and give a false impression of severe obstruction.
Methods: Gamma camera renography was performed with 50 MBq (99)Tc(m)-MAG3 before and with 150 MBq 30 min after intramuscular injection of 75 mg diclofenac in 10 patients with acute ureteral colic. The time to maximum isotope activity in each kidney, T(max), was compared with T(max) in 10 control patients, who did not receive diclofenac but underwent two identical renographies.
Results: T(max) was significantly delayed after diclofenac, from 353 s at baseline to >1,200 s on the stone side, and from 225 to 465 s on the healthy side. Without diclofenac there was no T(max) retardation between the two renographies.
Conclusion: Diclofenac treatment can lead to overestimation in ureteral stone disease, by delaying renal excretion bilaterally, but predominantly on the side of calculus.