☢️ Scintigrafie Renală cu Captopril pentru Hipertensiune Renovasculară

Updated Renovascular HTN Renogram 9/8/2024 ●Indications  To assess for renovascular HTN in the setting of abrupt onset or severe HTN, HTN resistant to 3-drug therapy, onset of HTN before age 30 or after age 55, abdominal/flank bruits, unexplained azotemia or recurrent pulmonary edema in an elderly HTN patient, worsening renal function during therapy with an ACE inhibitor or grade 3 or 4 hypertensive retinopathy. ●Radiopharmaceutical: 1 mCi Tc-99m MAG3 administered IV for the first routine renogram portion 5-10 mCi Tc-99m MAG3 administered IV for the second ACE inhibitor renogram portion ●ACE Inhibitor: Option 1 - 25 mg Captopril administered by mouth 1 hr prior to radionuclide administration Option 2 - 40 mgm/kg Enalaprilat (max 2.5 mg) administered IV over 3-5 mins 15 mins prior to radionuclide administration Leave the IV line in the patient until after the exam in case of symptomatic hypotension requiring IV fluids. Blood pressure must measure at least 120/80 mmHg prior to administering the ACE inhibitor. Blood pressure must be measured every 15 mins for 1 hr after ACE inhibitor administration.  ACE inhibitor use is contraindicated in pregnant women. A negative urine pregnancy test is required in potentially-pregnant patients prior to administration. ●Patient Preparation:  Patients receiving an oral ACE inhibitor for the exam should be instructed to not eat a solid meal for at least 4 hrs before receiving the ACE inhibitor. Have the patient drink 16-20 oz of water 30-60 mins prior to exam to ensure adequate hydration.  Have the patient empty his/her bladder immediately prior to imaging. Instruct the patient to void frequently for a day following the exam. ●Conflicting Examinations/Medications:  Patients taking an ACE inhibitor or angiotensin II receptor blockers should hold the medication for 3-7 days prior to the exam (if possible).  Patients taking diuretics should hold the medication for 3-5 days prior to the exam (if possible) to reduce volume depletion and decrease the risk of hypotension after receiving ACE inhibitor. No Nuclear Medicine exams within the previous 24 hrs. No barium GI exams within the previous 48 hrs. ●Pregnancy/Lactation:  ACE inhibitor use is contraindicated in pregnant women. A negative urine pregnancy test is required in potentially pregnant patients prior to administration. See Pregnant, Potentially Pregnant and Lactating Patients policy for specifics. Breast feeding mothers should discard breast milk for 4-24 hrs following Tc-99m MAG3 administration. ●Imaging Technique: Collimator - LEAP preferred over LEHR Photopeak - 140 keV 20% window for Tc-99m Image Preset Counts ◦Flow Images - 2 secs/image for 1 mins (30 images) ◦Dynamic Images - 60 secs/image for 34 mins (34 images) ◦Static Images - 60 secs/image Matrix Size - 128 x 128 (flow and dynamic), 256 x 256 (static) Zoom - none Patient Positioning - supine

●Baseline Renogram Images/Views: Perform a routine MAG3 exam (without ACE inhibitor or Lasix). Administer 1 mCi Tc-99m MAG3 IV Flow Images ◦Begin imaging immediately before radionuclide administration. ◦Obtain posterior images of the abdomen and pelvis for 60 secs. Dynamic Images ◦Begin imaging immediately after flow imaging ◦Obtain posterior images of the abdomen and pelvis for 29 mins. Static Images ◦Obtain posterior pre and post void images of the abdomen and pelvis after dynamic images. Obtain anterior images rather than posterior images if imaging a renal transplants. ●ACE Inhibitor Renogram Images/Views: Perform a MAG3 exam following ACE inhibitor administration (without Lasix).  When a 1 mCi dose of Tc-99m MAG3 is used for the baseline renogram, the ACE inhibitor portion can begin immediately after the baseline renogram is finished. Administer 5-10 mCi Tc-99m MAG3 IV Flow Images ◦Begin imaging immediately before radionuclide administration. ◦Obtain posterior images of the abdomen and pelvis for 60 secs. Dynamic Images ◦Begin imaging immediately after flow imaging ◦Obtain posterior images of the abdomen and pelvis for 29 mins. Static Images ◦Obtain posterior pre and post void images of the abdomen and pelvis after dynamic images. Obtain anterior images rather than posterior images if imaging a renal transplants. ●Image Post Processing:  Use the appropriate software to generate flow and time-activity curves and calculate the Tmax, T1/2, 20 min/max ratio and
split renal function percents.  Calculation of split renal function is most accurate when ROIs are drawn around each kidney (to include both the renal parenchyma and the collecting system / renal pelvis).  Assessment of response to diuretic is most accurate when ROIs are drawn around each renal collecting system / pelvis (excluding the renal parenchyma).  The most accurate method of measuring background activity is to draw C-shaped ROIs around the upper, lateral and lower aspects of each kidney rather than an ROI. See practice guideline for additional image processing guidelines. ●Notes:  Renovascular disease includes renal artery stenosis, renovascular HTN and azotemic renovascular disease (ischemic nephropathy).  Renovascular HTN is defined as an elevated blood pressure caused by renal hypoperfusion, usually resulting from renal artery stenosis and activation of the renin–angiotensin system.  Azotemic renovascular disease (ischemic nephropathy) refers to renal functional impairment associated with renal atrophy, intrarenal vascular lesions and interstitial nephritis and fibrosis in the presence of severe renal artery stenosis.  Renovascular HTN is estimated to affect less than 1%–3% of the unselected hypertensive population and up to 15%–30% of patients referred to a subspecialty center because of refractory HTN.

 Criteria associated with renovascular HTN include worsening of the renogram curve, reduction in relative uptake (>10% decrease from baseline), delay in the excretion of the radionuclide into the renal pelvis (≥2 min from baseline), prolongation of the renal and parenchymal transit time, an increase in the 20 min/max ratio (≥0.15 from baseline) and prolongation of the Tmax (>2–3 min or 40% from baseline). Unilateral parenchymal retention after ACE inhibition is the most important criterion for diagnosis renovascular HTN.  It is important to distinguish parenchymal (significant) from pelvic (insignificant) retention. Cortical ROIs are often used to evaluate parenchymal retention, but cortical renogram curves may be noisy when a low dose ofTc-99m MAG3 is administered for a baseline exam and renal function is poor. In this setting the whole-kidney renogram will provide a better index of parenchymal function if there is no tracer retention in the renal pelvis or calyces.  Bilateral symmetrical changes after ACE inhibition usually do not represent renovascular HTN and may be associated with hypotension, salt depletion, the use of calcium channel blockers and/or a low urine flow rate. Interpretation Categories ◦ Low Probability (<10%) - normal findings on ACE inhibitor renogram (pattern 0), abnormal baseline renogram
(pattern 1 or 2) that improves after ACE inhibition. Intermediate Probability - abnormal baseline renogram that is unchanged following ACE inhibition High Probability (>90%) - a renogram that changes markedly more abnormal after ACE inhibition ◦ ◦  Sources of error include ingestion of food within 4 hrs of administering ACE inhibitor, radionuclide infiltration, retention of radionuclide in the renal pelvis, dehydration, hypotension and a full bladder impairing drainage. Pelvic retention is likely to be related to the patient’s state of hydration but will result in an abnormal whole-kidney renogram curve, which may be incorrectly interpreted as representing renovascular HTN. Dehydration and hypotension may lead to bilateral parenchymal retention and bilateral renogram curve abnormalities.