Question

A dense nephrogram is obtained by:

• A. Dehydrating the patient
• B. Increasing the dose of contrast media
• C. Rapid (bolus) injection of dye
• D. Using non-ionic media

Hint:

Density depends on peak arterial contrast concentration, so push it fast.

Answer 1

The Correct Option is C

Step 1: The nephrogram is the renal parenchymal blush seen after contrast is injected and filtered by the glomeruli. Its density depends on how high a concentration of contrast reaches the kidney at once.
Step 2: A rapid bolus injection delivers a large amount of contrast into the renal arteries over a very short time. This produces a high peak plasma concentration of iodine reaching the glomeruli together, giving a dense, intense nephrogram.
Step 3: Why the other options are weaker or wrong. Dehydration concentrates contrast within the tubules and improves later pelvicalyceal opacification on a urogram, but it does not by itself create the dense parenchymal nephrogram the way a bolus does. Simply increasing the total dose given slowly does not raise the instantaneous peak concentration the way a fast bolus does. Choosing ionic versus non-ionic media affects safety and tolerability, not nephrogram density.
Step 4: So the dense nephrogram is best produced by a rapid bolus injection of the contrast dye.
Step 5: Answer: Option C, Rapid (bolus) injection of dye.