Patient should be will hydrated. 7 cc/kg (body weight) of H2O is given 15 minutes prior to scanning in adult patients. The patient should void before beginning the study.
RADIOPHARMACEUTICALS:
1. Combined dynamic study and tubular function.
Tc-99m-MAG-3, 5 - 10 mCi I.V., Critical organ = bladder 0.48 rad/mCi.
2. Dynamic renal scans using Tc-99m DTPA for GFR determination, 15 mCi I.V.
Critical organ = bladder, 0.07-0,6 rad/mCi.
Scan time is variable. Scanning begins with injection and is carried out to about 30 minutes. Delayed views may be necessary. If renal collecting system obstruction is present, Lasix may be given to differentiate functional from anatomic obstruction (up to 40 mg Lasix I.V.). Data is then acquired for at least 20 more minutes.
Tc-99m-DTPA is excreted by glomerular filtration (small amount is plasma bound) and is used to access renal perfusion and excretion. Captopril, an inhibitor of angiotensin converting enzyme, may significantly decrease the glomerular filtration rate in a kidney with renovascular disease. Call the Nuclear Medicine department (6-3966) for a consultation regarding the use of captopril in evaluating renovascular hypertension. Radiolabeled iodohippurate and Tc-99m-MAG-3, are mainly eliminated by tubular secretion and are, therefore, used to assess renal tubular function. Clearance measurements with I-123 O-Hippurate and MAG reflect effective renal plasma flow. Tc-99m glucoheptonate and DMSA are retained for relatively long periods in the renal cortex and are usually used when morphology rather than function is of major concern.
Tc-99m-MAG-3 is used in renal transplant patients to differentiate rejection from ATN.