Materials for medical students Renal Scintigraphy Materials for medical students Helena Balon, MD Wm. Beaumont Hospital Royal Oak, Michigan Charles University 3rd School of Medicine Dept Nucl Med, Prague

Indications Evaluation of: Renal perfusion and function Obstruction (Lasix renal scan) Renovascular HTN (Captopril renal scan) Infection (renal morphology scan) Pre-surgical quantitation (nephrectomy) Renal transplant Congenital anomalies, masses (renal morphology scan)

Renal Function Blood flow - 20% cardiac output to kidneys (1200 ml/min blood, 600 ml/min plasma) Filtration - 20% renal plasma flow filtered by glomeruli (120 ml/min, 170 L/d) Tubular secretion Tubular reabsorption (1% ultrafiltrate - urine) Endocrine functions

Renal Radiotracers Excretion Mechanisms GF TS TF Tc-99m DTPA >95% Tc-99m MAG3 <5% 95% I-131 OIH 20% 80% Tc-99m GHA 40%-60% 20% Tc-99m DMSA some 60% Semin NM Apr.92

Renal Radiopharmaceuticals Extract. fraction Clearance Tc-99m DTPA 20% 100-120 ml/min Tc-99m MAG3 40-50% ~ 300 ml/min I-131 OIH ~100% 500-600 ml/min

Renal Radiopharmaceuticals Dosimetry DTPA MAG3 GHA DMSA I-131OIH rad/10 mCi rad/5mCi rad/300µCi Kidney 0.2 0.15 1.6 3.5 0.01 Bladder 2.8 5.1 2.7 0.3 0.3 EDE (rem) 0.3 0.4 0.4 0.3 0.03

Choosing Renal Radiotracers Clin. Question Agent Perfusion MAG3, DTPA, GHA Morphology DMSA, GHA Obstruction MAG3, DTPA, OIH Relative function All GFR quantitation I-125 iothalamate, Cr-51 EDTA, DTPA ERPF quantitation MAG3, OIH

Basic Renal Scan Procedure

Basic Renal Scintigraphy Patient Preparation Patient must be well hydrated Give 5-10 ml/kg water (2-4 cups) 30-60 min. pre-injection Can measure U - specific gravity (<1.015) Void before injection Void @ end of study Int’l Consens. Comm. Semin NM ‘99:146-159

Basic Renal Scintigraphy Acquisition Supine position preferred Do not inject by straight stick Flow (angiogram) : 2-3 sec / fr x 1 min Dynamic: 15-30 sec / frame x 20-30 min (display @ 1-3 min/frame)

Basic Renal Scintigraphy Acquisition (cont’d) Obtain a 30-60 sec. image over injection site @ end of study if infiltration >0.5% dose do not report clearance Obtain post-void supine image of kidneys @ end of study Taylor, SeminNM 4/99:102-127

International Consensus Committee Recommendations for Basic Renogram Tracer: MAG3, (DTPA) Dose: 2 - 5 mCi adult, minimum 0.5 mCi peds Pt. position: supine (motion, depth issues) Include bladder, heart Collimator: LEAP Image over injection site Int’l Consens. Comm. Semin NM ‘99:146-159

DTPA normal

DTPA normal

Relative (split) function ROI’s

Relative uptake Contribution of each kidney to the total fct net cts in Lt ROI % Lt kid = --------------------------------------- x 100% net cts Lt + net cts Rt ROI Normal 50/50 - 56/44 Borderline 57/43 - 59/41 Abnormal > 60/40 Taylor, SeminNM Apr 99

Basic Renal Scintigraphy Processing Time to peak Best from cortical ROI Normal < 5 min Residual Cortical Activity (RCA20 or 30) Ratio of cts @ 20 or 30 min / peak cts Use cortical ROI Normal RCA20 for MAG3 < 0.3 Residual Urine Volume (post-void cts x void. vol)  (pre-void cts - post void cts)

DTPA flow + scan GFR = 29 ml/’ Creat = 2.0 L= 33% R= 67%

Renal artery occlusion

Rt renal infarct

Renogram Phases I. Vascular phase (flow study): Ao-to-Kid ~ 3” II. Parenchymal phase (kidney-to-bkg): Tpeak < 5’ III. Washout (excretory) phase

Renogram curves

Evaluation of Hydronephrosis Diuretic (Lasix) Renal Scan

Obstruction Obstruction to urine outflow leads to obstructive uropathy (hydronephrosis, hydroureter) and may lead to obstructive nephropathy (loss of renal function)

Diuretic Renal Scan Principle Hydronephrosis - tracer pooling in dilated renal pelvis Lasix induces increased urine flow If obstructed >>> will not wash out If dilated, non-obstructed >>> will wash out Can quantitate rate of washout (T1/2)

Diuretic Renal Scan Indications Evaluate functional significance of hydronephrosis Determine need for surgery obstructive hydronephrosis - surgical Rx non-obstructive hydronephrosis - medical Rx Monitor effect of therapy

Diuretic Renal Scan Requirements Rapidly cleared tracer Well hydrated patient Good renal function

Diuretic Renal Scan Procedure Pt. preparation: prehydration adults - oral or 360ml/m2 iv over 30’ peds - 10-15 ml/kg D5 0.3-0.45%NS void before injection bladder catheterization ?

Diuretic Renal Scan Procedure (cont’d) Tracers: Tc-99m MAG3 5-10 mCi (preferred over DTPA) Acquisition: supine until pelvis full (can switch to sitting post- Lasix) Flow (angiogram) : 2-3 sec / fr x 1 min Dynamic: 15-30 sec / frame x 20-30 min

Diuretic Renal Scan Procedure (cont’d) Void before Lasix Lasix: 40mg adult, 1mg/kg child iv @ ~10-20 min (when pelvis full) or @ -15min (“F-15” method) Acquisition for 30 min post Lasix Assess adequacy of diuresis Measure voided volume Adults produce ~200-300 ml urine post-Lasix

Diuretic Renal Scan Procedure (cont’d) Don’t give Lasix if Collecting system still filling Collecting system not full by 60 min Collecting system drains spontaneously Poor ipsilateral fct (< 20%)

pre-Lasix

post-Lasix

No UPJ obstruction T1/2 R = 6’ L = 2’

Post-Lasix curve

Pre-Lasix 10 y/o M

Post-Lasix

Rt UPJ obstruction T1/2 R = N/A F/U - nephrostomy tube placed

Lt hydronephrosis 3-wk old baby 3164897

Lt UPJ obstruction 3164897

Rt UPJ obstruction T1/2 R = N/A F/U - nephrostomy tube placed

Lt UPJ obstruction 3164897

Diuretic Renal Scan Processing ROI placement around whole kidney or around dilated renal collecting system T/A curve T1/2 from Lasix injection vs. from diuretic response linear vs. exponential fit of washout curve

Diuretic Renal Scan Washout (diuretic response) T1/2 time required for 50% tracer to leave the dilated unit i.e. time required for activity to fall to 50% of peak

T1/2 washout cts 100% 50% T1/2 min

T1/2 value Variables influencing T1/2 value: Tracer State of hydration Volume of dilated pelvis Bladder catheterization Dose of Lasix Renal function (response to Lasix) ROI (kidney vs. pelvis) T1/2 calculation (from inj. vs. response, curve fit)

T1/2 Normal < 10 min Obstructed > 20 min Indeterminate 10 - 20 min Best to obtain own normals for each institution, depending on protocol used

Diuretic Renal Scan Interpretation Interpret whole study, not T1/2 alone Visual (dynamic images) Washout curve shape (concave vs. convex) T1/2

Diuretic Renal Scan Pitfalls False positive for obstruction Distended bladder Gross hydronephrosis T(transit time) = V (volume)  F (flow) Poorly functioning / immature kidney Dehydration False negative Low grade obstruction

Effect of catheterization (1) full bladder, no catheter

Effect of catheterization (2) with catheter in bladder

Effect of catheterization (3) without catheter with catheter

“F minus 15” Diuretic Renogram Furosemide (Lasix) injected 15 min before radiopharmaceutical Rationale: kidney in maximal diuresis, under maximal stress Some equivocals will become clearly positive, some clearly negative English, Br JUrol 1987:10-14 Upsdell, Br JUrol 1992:126-132

Evaluation of Renovascular Hypertension Captopril Renal Scan (ACEI Renography)

Renovascular Disease Renal artery stenosis (RAS) Ischemic nephropathy Renovascular hypertension (RVH) RAS  RVH

Renovascular Hypertension Caused by renal hypoperfusion Atherosclerosis Fibromuscular dysplasia Mediated by renin - AT - aldosterone system Potentially curable by renal revascularization

Renovascular Hypertension Prevalence <1% unselected population with HTN Clinical features Abrupt onset HTN in child, adult < 30 or > 50y Severe HTN resistant to medical Rx Unexplained or post-ACEI impairment in ren fct HTN + abdominal bruits If these present - moderate risk of RVH (20-30%)

Renin-Angiotensin System Angiotensinogen RAS Renin Angiotensin I Captopril ACE Angiotensin II Aldosterone Vasoconstriction HTN

Effect of RAS on GFR

Diagnosis of RAS Gold std: angiography Initial non-invasive tests: ACEI renography Duplex sonography Other tests: MRA - insensitive for distal / segmental RAS Captopril test (PRA post-C.) - low sensitivity Renal vein renin levels

ACEI Renography

ACEI Renography Patient Preparation Off ACEI & ATII receptor blockers x 3-7 days Off diuretics x 5-7d No solid food x 4 hrs Patient well hydrated 10 ml/kg water 30-60 min pre- and during test ACEI Captopril 25-50 mg po (crushed), 1 hr pre-scan Enalaprilat 40 µg/kg iv (2.5 mg max), 15 min pre-scan Monitor BP q 15 min

ACEI Renography Procedure Tracer: Tc-99m MAG3 (or DTPA) Protocol: 1 day vs. 2 day test 1 day test: baseline scan (1-2 mCi) followed by post-Capto scan (8-10 mCi) 2 day test: post-Capto scan, only if abnormal >> baseline Acquisition: flow & dynamic x 20-30 min.

ACEI Renography Processing Relative renal uptake (bkg corrected) Time to peak (Tp) - from cortical ROI normal < 5 min RCA20 (20 min/peak ratio) - from cortical ROI normal < 0.3

ACEI Renography Grading renogram curves

ACEI Renography Diagnostic Criteria MAG3: ipsilateral parenchymal retention p.C. change in renogram curve by  1 grade RCA20 increase by  15% (e.g. from 30% to 45%) Tp increase by  2 min or 40% (e.g. from 5 to 7’) DTPA: ipsilateral decreased uptake Decrease in relative uptake  10% (e.g.from 50/50 to 40/60), change of 5-9% - intermediate change in renogram curve by  2 grades Consens. report JNM ‘96:1876 Semin NM 4/99:128-145

ACEI Renography Interpretation High probability RVH (>90%) Marked C-induced change Low probability RVH (<10%) Normal Captopril scan Abnormal baseline, improved p-C. Type I curve - pre- and post-C. Intermediate probability RVH Abnl baseline, no change p-C.

Captopril Renal Scan MAG 3

Captopril Renal Scan MAG3

Captopril Renal Scan MAG 3

Captopril Renal Scan MAG 3

ACEI Renography In normal renal function - sens/spec ~ 90% In poor renal fct / ischemic nephropathy, ACEI renography often indeterminate >>> do MRA, Duplex US, angio

Evaluation of Renal Infection Renal Morphology Scan (Renal Cortical Scintigraphy)

UTI VUR PN may lead to scarring >>> ESRD, HTN risk factor for PN, not all pts w PN have VUR PN may lead to scarring >>> ESRD, HTN early Dx and Rx necessary Clinical & laboratory Dx of renal involvement in UTI unreliable

Renal Cortical Scintigraphy Indications Determine involvement of upper tract (kidney) in acute UTI (acute pyelonephritis) Detect cortical scarring (chronic pyelonephr.) Follow-up post Rx

Renal Cortical Scintigraphy Procedure Tracers Tc-99m DMSA Tc-99m GHA Acquisition 2-4 hrs post-injection parallel hole posterior pinhole post. + post. oblique (or SPECT) Processing: relative fct

Renal Cortical Scintigraphy Interpretation Acute PN single or multiple “cold” defects renal contour not distorted diffuse decreased uptake diffusely enlarged kidney or focal bulging Chronic PN volume loss, cortical thinning defects with sharp edges Differentiation of AcPN vs. ChPN unreliable

Renal Cortical Scintigraphy “Cold Defect “ Acute or chronic PN Hydronephrosis Cyst Tumors Trauma (contusion, laceration, rupture, hematoma) Infarct

DMSA parallel hole collimator

Normal DMSA pinhole LPO RPO

DMSA

Acute pyelonephritis DMSA post L post R LEAP LPO pinhole RPO

Renal Cortical Scintigraphy Congenital Anomalies Agenesis Ectopy Fusion (horseshoe, crossed fused ectopia) Polycystic kidney Multicystic dysplastic kidney Pseudomasses (fetal lobulation, hypertrophic column of Bertin)

DMSA horseshoe kidney parallel pinhole

DMSA Lt Agenesis parallel

GHA Crossed ectopia 74% 26%

Radionuclide Cystogram

Indications Evaluation of children with recurrent UTI 30-50% have VUR F/U after initial VCUG Assess effect of therapy / surgery Screening of siblings of reflux pts.

Methods Direct Indirect Tc-99m DTPA or Tc-99m MAG3 Tc-99m S.C. or TcO4 i.v. no catheter info on kidneys need pt cooperation need good renal fct Tc-99m S.C. or TcO4 via Foley can do at any age VUR during filling catheterization Advant. Disadv.

Direct Cystography 1 mCi S.C. in saline via Foley Fill bladder until reversal of flow (bladder capacity = (age+2) x 30 Continuous imaging during filling & voiding Post void image Record volume instilled volume voided pre- and post- void cts

RN Cystogram vs. VCUG Advantages Disadvantages Lower radiation dose (5 vs 300 mrad to ovary) Smaller amount of reflux detectable Quantitation of post-void residual volume Cannot detect distal ureteral reflux No anatomic detail Grading difficult

Normal cystogram filling voiding post-void

VUR - filling phase A

VUR - voiding phase & post-void B

Post void residual volume voided vol x post-void cts pre-void cts - post void cts RV =

Reflux nephropathy 16% 84%