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Figure 11. Non-obstructive hydronephrosis. Sequential 1 mintue images (A) show relatively diminished function on the left with hold-up of tracer in both renal collecting systems. Furosemide was given at 12 minutes with rapid emptying of the renal pelves. Time activity curves (B) were generated from regions of interest placed over the renal pelves and exponential curves fitted to the excretion portion of the curves. The half times are normal (<5 minutes) bilaterally.

the collecting systems by backpressure. Bladder emptying may need to be assured by catheterization, especially in cases of bladder dysfunction and known vesicoureteric reflux.

Because of its rapid excretion, 99mTc-MAG3 is preferred over 99mTc-DTPA. Activity in the renal pelvis and calyces will be greater before furosemide is given and will be washed out with urine of lesser activity, thus maximizing contrast between the pre and post diuretic images.

Furosemide is given intravenously at a dose of 40 mg for age > 16 years and 0.51 mg/kg for children. It is given if significant activity remains in the collecting system after a post-void view following a standard 20-minute renogram ("F+20" protocol). A further 15-20 minute study is then acquired.

Figure 12. Flow-related obstruction. Sequential 1 minute images (A) and pelvic emptying curves (B) show rapid emptying from the right renal pelvis. On the left, there is an initial good response to furosemide but the clearance curve reaches a plateau (arrow) indicating flow-related obstruction (Homesy's sign).

Figure 12. Flow-related obstruction. Sequential 1 minute images (A) and pelvic emptying curves (B) show rapid emptying from the right renal pelvis. On the left, there is an initial good response to furosemide but the clearance curve reaches a plateau (arrow) indicating flow-related obstruction (Homesy's sign).

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