Effect of the NSAID diclofenac on 99mTc-MAG3 and 99mTc-DTPA renography: A comparison study

Objectives To compare the effect of the NSAID diclofenac, which is the commonly used to relieve renal pain, on renography using 2 radionuclides, 99mTc-MAG3 and 99mTc-DTPA.

Methods Renography studies were performed for 24 New Zealand White rabbits. The studies were performed initially in the control state and then repeated 20 minutes after a single i.v. dose of diclofenac (2mg/kg) two days later. Rabbits were first studied with 48MBq (1.3 mCi) of 99mTc-MAG3. After one week, studies were repeated using 96 MBq (2.6 mCi) 99mTc-DTPA. Animals were given i.v. administrations of 60 ml saline 30 minutes before each study. Studies were acquired using Gamma camera equipped with a low energy high resolution collimator interfaced with a computer. Images were acquired as 2 s frames for the first 1 min and every 30 s for 30 min on a matrix of 64x64. Time-activity curves were generated from regions of interest drawn over the whole kidneys. Time to peak activity (T max), time from peak to 50% activity (T ½) and the uptake slope of each kidney were calculated from the renograms for control and rabbit treated with diclofenac.

Results Diclofenac shifted renogram experimental curves to the right compared to control curves indicating delayed renal uptake and clearance of radioactivity of the two tracers. The calculated average values of Tmax for control & treated rabbits using 99mTc-MAG3 were (1.8±0.5 and 6.35±0.4 min) respectively, while values were (3.4±0.4 and 18.2±2 min) using 99mTc-DTPA. The T ½ for control and treated rabbits were (3.2±0.07 and 6.6±0.07 min) for 99mTc-MAG3 while 99mTc-DTPA values were (10.1±1 and 35±4 min) respectively (p<0.05).

Conclusions Diclofenac delayed both Tmax and T½ for both tracers. However NSAID-induced changes were considerably greater for DTPA. NSAIDs inhibit prostaglandins synthesis therefore their effect is mainly on the glomerular filtration than tubular secretion. We suggest using 99mTc-MAG3 and not 99mTc-DTPA for performing renography studies with the use of NSAIDs.