A dense renogram is obtained by:
In a normally functioning kidney, rapid injection of the dye gives an uniform dense nephrogram because of appearance of contrast material in the proximal tubule and peritubular capillaries within 30seconds of injection and approximately 2 minutes later contrast agent begin to appear in the calyces. Ref: Diseases of The Kidney and Urinary Tract By Robe W. Schrier, Page 338, 706
Dehydrating the patient
Increasing the dose of contrast media
Rapid (Bolus) injection of dye
Using non ionic media