Renal Scintigraphy

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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

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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)

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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

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Renal RadiotracersExcretion Mechanisms
GF TS TFTc-99m DTPA gt95 Tc-99m
MAG3 lt5 95 I-131 OIH 20 80 Tc-99m
GHA 40-60 20 Tc-99m DMSA some 60
Semin NM Apr.92
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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
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Renal RadiopharmaceuticalsDosimetry

• 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

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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

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Basic Renal ScanProcedure
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Basic Renal ScintigraphyPatient 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 (lt1.015)
• Void before injection
• Void _at_ end of study

Intl Consens. Comm. Semin NM 99146-159
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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 _at_ 1-3 min/frame)

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Basic Renal Scintigraphy Acquisition (contd)

• Obtain a 30-60 sec. image over injection site _at_
  end of study
• if infiltration gt0.5 dose do not report
  clearance
• Obtain post-void supine image of kidneys _at_ end
  of study

Taylor, SeminNM 4/99102-127
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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

Intl Consens. Comm. Semin NM 99146-159
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DTPA normal
14
DTPA normal
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Relative (split) functionROIs
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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 gt 60/40

Taylor, SeminNM Apr 99
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Basic Renal Scintigraphy Processing

• Time to peak
• Best from cortical ROI
• Normal lt 5 min
• Residual Cortical Activity (RCA20 or 30)
• Ratio of cts _at_ 20 or 30 min / peak cts
• Use cortical ROI
• Normal RCA20 for MAG3 lt 0.3
• Residual Urine Volume
• (post-void cts x void. vol) ? (pre-void cts -
  post void cts)

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DTPA flow scan
GFR 29 ml/ Creat 2.0 L 33 R 67
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Renal artery occlusion
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Rt renal infarct
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Renogram Phases

• I. Vascular phase (flow study) Ao-to-Kid 3
• II. Parenchymal phase (kidney-to-bkg) Tpeak lt 5
• III. Washout (excretory) phase

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Renogram curves
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Evaluation of Hydronephrosis

• Diuretic (Lasix) Renal Scan

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Obstruction

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

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Diuretic Renal ScanPrinciple

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

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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

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Diuretic Renal Scan Requirements

• Rapidly cleared tracer
• Well hydrated patient
• Good renal function

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Diuretic Renal Scan Procedure

• Pt. preparation
• prehydration adults - oral or 360ml/m2 iv
  over 30 peds - 10-15 ml/kg D5 0.3-0.45NS
• void before injection
• bladder catheterization ?

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Diuretic Renal Scan Procedure (contd)

• 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

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Diuretic Renal Scan Procedure (contd)

• Void before Lasix
• Lasix 40mg adult, 1mg/kg child iv _at_ 10-20
  min (when pelvis full) or _at_ -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

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Diuretic Renal Scan Procedure (contd)

• Dont give Lasix if
• Collecting system still filling
• Collecting system not full by 60 min
• Collecting system drains spontaneously
• Poor ipsilateral fct (lt 20)

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pre-Lasix
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post-Lasix
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No UPJ obstruction
T1/2 R 6 L 2
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Post-Lasix curve
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Pre-Lasix
10 y/o M
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Post-Lasix
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Rt UPJ obstruction
T1/2 R N/A
F/U - nephrostomy tube placed
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Lt hydronephrosis
3164897
3-wk old baby
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Lt UPJ obstruction
3164897
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Rt UPJ obstruction
T1/2 R N/A
F/U - nephrostomy tube placed
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Lt UPJ obstruction
3164897
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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

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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

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

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T1/2

• Normal lt 10 min
• Obstructed gt 20 min
• Indeterminate 10 - 20 min
• Best to obtain own normals for each institution,
  depending on protocol used

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Diuretic Renal Scan Interpretation

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

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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
• Poorly functioning / immature kidney

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Effect of catheterization (1)
full bladder,no catheter
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Effect of catheterization (2)
with catheter in bladder
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Effect of catheterization (3)
without catheter
with catheter
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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 198710-14Upsdell, Br JUrol
1992126-132
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Evaluation of Renovascular Hypertension
Captopril Renal Scan (ACEI Renography)
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Renovascular Disease

• Renal artery stenosis (RAS)
• Ischemic nephropathy
• Renovascular hypertension (RVH)
• RAS ? RVH

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Renovascular Hypertension

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

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Renovascular Hypertension

• Prevalence
• lt1 unselected population with HTN
• Clinical features
• Abrupt onset HTN in child, adult lt 30 or gt 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)

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Renin-Angiotensin System
RAS
Angiotensinogen
Renin
Angiotensin I
Captopril
ACE
Angiotensin II
Aldosterone Vasoconstriction
HTN
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Effect of RAS on GFR
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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

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ACEI Renography
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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

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ACEI RenographyProcedure

• 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 gtgt baseline
• Acquisition flow dynamic x 20-30 min.

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ACEI RenographyProcessing

• Relative renal uptake (bkg corrected)
• Time to peak (Tp) - from cortical ROI
• normal lt 5 min
• RCA20 (20 min/peak ratio) - from cortical ROI
• normal lt 0.3

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ACEI RenographyGrading renogram curves
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ACEI RenographyDiagnostic 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 961876Semin NM 4/99128-145
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ACEI RenographyInterpretation

• High probability RVH (gt90)
• Marked C-induced change
• Low probability RVH (lt10)
• Normal Captopril scan
• Abnormal baseline, improved p-C.
• Type I curve - pre- and post-C.
• Intermediate probability RVH
• Abnl baseline, no change p-C.

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Captopril Renal ScanMAG 3
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Captopril Renal Scan MAG3
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Captopril Renal ScanMAG 3
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Captopril Renal ScanMAG 3
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ACEI Renography

• In normal renal function - sens/spec 90
• In poor renal fct / ischemic nephropathy, ACEI
  renography often indeterminate gtgtgt do MRA,
  Duplex US, angio

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

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

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Renal Cortical ScintigraphyIndications

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

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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

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Renal Cortical ScintigraphyInterpretation

• 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

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Renal Cortical ScintigraphyCold Defect

• Acute or chronic PN
• Hydronephrosis
• Cyst
• Tumors
• Trauma (contusion, laceration, rupture,
  hematoma)
• Infarct

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DMSA parallel hole collimator
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Normal DMSA
pinhole
LPO RPO
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DMSA
87
Acute pyelonephritisDMSA
post L
post R
LEAP
LPO pinhole
RPO
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Renal Cortical ScintigraphyCongenital Anomalies

• Agenesis
• Ectopy
• Fusion (horseshoe, crossed fused ectopia)
• Polycystic kidney
• Multicystic dysplastic kidney
• Pseudomasses (fetal lobulation, hypertrophic
  column of Bertin)

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DMSAhorseshoe kidney
parallel pinhole
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DMSALt Agenesis
parallel
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GHACrossed ectopia
7426
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Radionuclide Cystogram
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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.

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Methods
Direct Indirect

• Tc-99m DTPA or Tc-99m MAG3
• 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.
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Direct Cystography

• 1 mCi S.C. in saline via Foley
• Fill bladder until reversal of flow
• (bladder capacity (age2) x 30
• Continuous imaging during filling voiding
• Post void image
• Record
• volume instilled
• volume voided
• pre- and post- void cts

97
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

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Normal cystogram
filling
voiding post-void
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VUR - filling phase
A
100
VUR - voiding phase post-void
B
101
Post void residual volume
voided vol x post-void cts pre-void cts -
post void cts
RV
102
Reflux nephropathy
16
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