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

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Presentation on theme: "Renal Scintigraphy Helena Balon, MD Wm. Beaumont Hospital Royal Oak, Michigan Charles University 3rd School of Medicine Dept Nucl Med, Prague Materials."— Presentation transcript:

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

2 Indications  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) Evaluation of:

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 OIH20%80% Tc-99m GHA40%-60%20% Tc-99m DMSAsome 60% Semin NM Apr.92

5 Renal Radiopharmaceuticals Extract. fractionClearance Tc-99m DTPA20% ml/min Tc-99m MAG340-50% ~ 300 ml/min I-131 OIH~100% ml/min

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

7 Choosing Renal Radiotracers PerfusionMAG3, DTPA, GHA MorphologyDMSA, GHA Obstruction MAG3, DTPA, OIH Relative functionAll GFR quantitationI-125 iothalamate, Cr-51 EDTA, DTPA ERPF quantitationMAG3, OIH Clin. QuestionAgent

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) 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 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

15 Relative (split) function ROI’s

16 Relative uptake 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 net cts Lt + net cts Rt ROI  Normal50/ /44  Borderline57/ /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 (RCA 20 or 30 )  Ratio of 20 or 30 min / peak cts  Use cortical ROI  Normal RCA 20 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): T peak < 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 (T 1/2 )

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/m 2 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 ~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 wk old baby Lt hydronephrosis

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  T 1/2  from Lasix injection vs. from diuretic response  linear vs. exponential fit of washout curve

44 Diuretic Renal Scan Washout (diuretic response) T 1/2 time required for 50% tracer to leave the dilated unit i.e. time required for activity to fall to 50% of peak

45 T 1/2 washout cts 100% 50% T 1/2 min

46 T 1/2 value  Variables influencing T 1/2 value:  Tracer  State of hydration  Volume of dilated pelvis  Bladder catheterization  Dose of Lasix  Renal function (response to Lasix)  ROI (kidney vs. pelvis)  T 1/2 calculation (from inj. vs. response, curve fit)

47 T 1/2  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 T 1/2 alone  Visual (dynamic images)  Washout curve shape (concave vs. convex)  T 1/2

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

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

51 with catheter in bladder Effect of catheterization (2)

52 Effect of catheterization (3) with catheter without 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 Captopril Renal Scan (ACEI Renography) Evaluation of Renovascular Hypertension

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 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 RAS Captopril Angiotensinogen Angiotensin I Angiotensin II AldosteroneVasoconstriction HTN Renin ACE

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  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 ACEI Renography Patient Preparation

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 (T p ) - from cortical ROI  normal < 5 min  RCA 20 (20 min/peak ratio) - from cortical ROI  normal < 0.3

65

66 ACEI Renography Grading renogram curves

67 ACEI Renography Diagnostic Criteria  MAG3: ipsilateral parenchymal retention p.C.  change in renogram curve by  1 grade  RCA 20 increase by  15% (e.g. from 30% to 45%)  T p 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 MAG 3 Captopril Renal Scan MAG 3

70 Captopril Renal Scan MAG3

71 MAG 3 Captopril Renal Scan MAG 3

72

73

74

75

76

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

79 UTI  VUR  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

86 DMSA

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

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 parallelpinhole

90 DMSA Lt Agenesis parallel

91 GHA Crossed ectopia 74% 26%

92

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

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  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 Advantages Disadvantages

98 Normal cystogram filling voiding post-void

99 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% 84%


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