Hospitals & Services
The most widely used radiopharmaceutical is 99mTc-MAG3. It is excreted by both glomerular filtration and tubular secretion and can be used in patients with renal failure and in patients allergic to IVU contrast agent. The Renogram can be used to evaluate renal perfusion and renal obstruction. Differentiation of obstructive vs nonobstructive hydronephrosis can be made by initiating a brisk diuresis with Frusemide (Lasix). In an obstructed hydronephrosis, washout of activity does not occur, while washout of activity occurs if obstruction is not present. Similarly, in a nonobstructive system cortical transit times should be essentially normal.
Differential diagnosis of obstructive vs. non-obstructive collecting system (with Frusemide provocation and measurement of transit times).
Evaluation and follow up of renal obstruction
Screening for renovascular disease (with ACE inhibitor). Limited role.
The patient should be off diuretics for at least 24 hours if possible, and should be well hydrated.
On arrival, adults are given 1 litre of water to drink over 30 minutes.
An IV injection is given and continuous images are recorded for the next 30 minutes. A diuretic is administered during the scan.
On completion of the 30-minute scan a further image may be taken after bladder emptying. The entire procedure takes about one hour.