Captopril Renal Scan

Captopril Renal Scan – Details & Precautions

A Captopril Renal Scan is a nuclear medicine test used to diagnose renal artery stenosis (RAS), a condition where the arteries supplying the kidneys become narrowed, reducing blood flow and affecting kidney function. This test helps determine whether high blood pressure (hypertension) is due to RAS.

Details of a Captopril Renal Scan

Purpose

• Diagnoses renal artery stenosis (narrowing of kidney arteries).
• Determines if high blood pressure (renovascular hypertension) is caused by kidney artery blockage.
• Evaluates kidney function before and after Captopril (an ACE inhibitor).
• Assesses differential function of each kidney.

Procedure

1. Baseline Kidney Scan

   • A small amount of Technetium-99m DTPA or MAG3 is injected into a vein.
   • A gamma camera captures kidney function and blood flow images.

2. Administration of Captopril

   • Captopril (25–50 mg) is given orally to lower blood pressure and test kidney response.
   • You will rest for 30–60 minutes to allow the medication to take effect.

3. Second Kidney Scan

   • Another tracer injection is given, and images are taken again.
   • This allows doctors to compare pre- and post-Captopril kidney function.

4. Completion

   • The doctor analyzes the changes in kidney function, helping determine if renal artery stenosis is causing high blood pressure.

Precautions for a Captopril Renal Scan

Before the Test

✅ Fasting:

• Do not eat for 4 hours before the test.

✅ Hydration:

• Drink plenty of water before the test, unless instructed otherwise.

✅ Medication Restrictions:

• Stop ACE inhibitors (e.g., Lisinopril, Ramipril, Enalapril) and ARBs (e.g., Losartan, Valsartan) 48 hours before the scan (only if instructed by your doctor).
• Stop diuretics (e.g., Furosemide, Hydrochlorothiazide) 24 hours before the test if advised.
• Inform your doctor if you take beta-blockers or calcium channel blockers for blood pressure.

✅ Recent Contrast Studies:

• If you had a CT scan with contrast, inform your doctor, as it may affect results.

✅ Pregnancy/Breastfeeding:

• Inform your doctor if you are pregnant or breastfeeding, as the radioactive tracer may affect the baby.

During the Test

• Lie still to avoid blurry images.
• You may feel dizzy or lightheaded after taking Captopril, as it lowers blood pressure.
• If you experience nausea, sweating, or weakness, inform the medical staff immediately.

After the Test

✅ Drink plenty of water to flush out the radioactive tracer.
✅ Rest for a few minutes if you feel lightheaded.
✅ Resume normal activities and diet unless otherwise instructed.
✅ Avoid sudden movements or standing up quickly if you feel dizzy.