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Materials for medical students

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1 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

2 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)

3 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

4 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

5 Renal Radiopharmaceuticals
Extract. fraction Clearance Tc-99m DTPA 20% ml/min Tc-99m MAG % ~ 300 ml/min I-131 OIH ~100% ml/min

6 Renal Radiopharmaceuticals Dosimetry
DTPA MAG3 GHA DMSA I-131OIH rad/10 mCi rad/5mCi rad/300µCi Kidney Bladder EDE (rem)

7 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

8 Basic Renal Scan Procedure

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

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

11 Basic Renal Scintigraphy Acquisition (cont’d)
Obtain a sec. image over injection 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:

12 International Consensus Committee Recommendations for Basic Renogram
Tracer: MAG3, (DTPA) Dose: 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:

13 DTPA normal

14 DTPA normal

15 Relative (split) function ROI’s

16 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/ /44 Borderline 57/ /41 Abnormal > 60/40 Taylor, SeminNM Apr 99

17 Basic Renal Scintigraphy Processing
Time to peak Best from cortical ROI Normal < 5 min Residual Cortical Activity (RCA20 or 30) Ratio of 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)

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

19 Renal artery occlusion

20 Rt renal infarct

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

22 Renogram curves

23 Evaluation of Hydronephrosis
Diuretic (Lasix) Renal Scan

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

25 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)

26 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

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

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

29 Diuretic Renal Scan Procedure (cont’d)
Tracers: Tc-99m MAG 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: sec / frame x min

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

31 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%)

32 pre-Lasix

33 post-Lasix

34 No UPJ obstruction T1/2 R = 6’ L = 2’

35 Post-Lasix curve

36 Pre-Lasix 10 y/o M

37 Post-Lasix

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

39 Lt hydronephrosis 3-wk old baby

40 Lt UPJ obstruction

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

42 Lt UPJ obstruction

43 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

44 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

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

46 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)

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

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

49 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

50 Effect of catheterization (1)
full bladder, no catheter

51 Effect of catheterization (2)
with catheter in bladder

52 Effect of catheterization (3)
without catheter with catheter

53 “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:

54 Evaluation of Renovascular Hypertension
Captopril Renal Scan (ACEI Renography)

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

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

57 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%)

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

59 Effect of RAS on GFR

60 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

61 ACEI Renography

62 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 min pre- and during test ACEI Captopril 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

63 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 min.

64 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


66 ACEI Renography Grading renogram curves

67 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:

68 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.

69 Captopril Renal Scan MAG 3

70 Captopril Renal Scan MAG3

71 Captopril Renal Scan MAG 3


73 Captopril Renal Scan MAG 3




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

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

79 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

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

81 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

82 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

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

84 DMSA parallel hole collimator

85 Normal DMSA pinhole LPO RPO


87 Acute pyelonephritis DMSA
post L post R LEAP LPO pinhole RPO

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

89 DMSA horseshoe kidney parallel pinhole

90 DMSA Lt Agenesis parallel

91 GHA Crossed ectopia 74% %


93 Radionuclide Cystogram

94 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.

95 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.

96 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

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

98 Normal cystogram filling voiding post-void

99 VUR - filling phase A

100 VUR - voiding phase & post-void

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

102 Reflux nephropathy 16% 84%

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