9 Basic Renal Scintigraphy Patient Preparation Patient must be well hydratedGive 5-10 ml/kg water (2-4 cups) min. pre-injectionCan measure U - specific gravity (<1.015)Void before injectionend of studyInt’l Consens. Comm.Semin NM ‘99:
10 Basic Renal Scintigraphy Acquisition Supine position preferredDo not inject by straight stickFlow (angiogram) : 2-3 sec / fr x 1 minDynamic: sec / frame x min1-3 min/frame)
11 Basic Renal Scintigraphy Acquisition (cont’d) Obtain a sec. image over injection end of studyif infiltration >0.5% dose do not report clearanceObtain post-void supine image of kidneys @ end of studyTaylor, SeminNM 4/99:
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 ROINormal 50/ /44Borderline 57/ /41Abnormal > 60/40Taylor, SeminNM Apr 99
17 Basic Renal Scintigraphy Processing Time to peakBest from cortical ROINormal < 5 minResidual Cortical Activity (RCA20 or 30)Ratio of 20 or 30 min / peak ctsUse cortical ROINormal RCA20 for MAG3 < 0.3Residual Urine Volume(post-void cts x void. vol) (pre-void cts - post void cts)
23 Evaluation of Hydronephrosis Diuretic (Lasix) Renal Scan
24 ObstructionObstruction 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 pelvisLasix induces increased urine flowIf obstructed >>> will not wash outIf dilated, non-obstructed >>> will wash outCan quantitate rate of washout (T1/2)
26 Diuretic Renal Scan Indications Evaluate functional significance of hydronephrosisDetermine need for surgeryobstructive hydronephrosis - surgical Rxnon-obstructive hydronephrosis - medical RxMonitor effect of therapy
28 Diuretic Renal Scan Procedure Pt. preparation:prehydration adults - oral or 360ml/m2 iv over 30’ peds ml/kg D %NSvoid before injectionbladder 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 minDynamic: sec / frame x min
30 Diuretic Renal Scan Procedure (cont’d) Void before LasixLasix: 40mg adult, 1mg/kg child iv @ ~10-20 min (when pelvis full) -15min (“F-15” method)Acquisition for 30 min post LasixAssess adequacy of diuresisMeasure voided volumeAdults produce ~ ml urine post-Lasix
31 Diuretic Renal Scan Procedure (cont’d) Don’t give Lasix ifCollecting system still fillingCollecting system not full by 60 minCollecting system drains spontaneouslyPoor ipsilateral fct (< 20%)
43 Diuretic Renal Scan Processing ROI placementaround whole kidney oraround dilated renal collecting systemT/A curveT1/2from Lasix injection vs. from diuretic responselinear 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 fallto 50% of peak
46 T1/2 value Variables influencing T1/2 value: Tracer State of hydration Volume of dilated pelvisBladder catheterizationDose of LasixRenal 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 minBest to obtain own normals for each institution, depending on protocol used
48 Diuretic Renal Scan Interpretation Interpret whole study, not T1/2 aloneVisual (dynamic images)Washout curve shape (concave vs. convex)T1/2
49 Diuretic Renal Scan Pitfalls False positive for obstructionDistended bladderGross hydronephrosisT(transit time) = V (volume) F (flow)Poorly functioning / immature kidneyDehydrationFalse negativeLow 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 catheterwith catheter
53 “F minus 15” Diuretic Renogram Furosemide (Lasix) injected 15 min before radiopharmaceuticalRationale: kidney in maximal diuresis, under maximal stressSome equivocals will become clearly positive, some clearly negativeEnglish, Br JUrol 1987:10-14 Upsdell, Br JUrol 1992:
54 Evaluation of Renovascular Hypertension Captopril Renal Scan (ACEI Renography)
56 Renovascular Hypertension Caused by renal hypoperfusionAtherosclerosisFibromuscular dysplasiaMediated by renin - AT - aldosterone systemPotentially curable by renal revascularization
57 Renovascular Hypertension Prevalence<1% unselected population with HTNClinical featuresAbrupt onset HTN in child, adult < 30 or > 50ySevere HTN resistant to medical RxUnexplained or post-ACEI impairment in ren fctHTN + abdominal bruitsIf these present - moderate risk of RVH (20-30%)
58 Renin-Angiotensin System AngiotensinogenRASReninAngiotensin ICaptoprilACEAngiotensin IIAldosterone VasoconstrictionHTN
62 ACEI Renography Patient Preparation Off ACEI & ATII receptor blockers x 3-7 daysOff diuretics x 5-7dNo solid food x 4 hrsPatient well hydrated10 ml/kg water min pre- and during testACEICaptopril mg po (crushed), 1 hr pre-scanEnalaprilat 40 µg/kg iv (2.5 mg max), 15 min pre-scanMonitor BP q 15 min
63 ACEI Renography Procedure Tracer: Tc-99m MAG3 (or DTPA)Protocol: 1 day vs. 2 day test1 day test: baseline scan (1-2 mCi) followed by post-Capto scan (8-10 mCi)2 day test: post-Capto scan, only if abnormal >> baselineAcquisition: flow & dynamic x min.
64 ACEI Renography Processing Relative renal uptake (bkg corrected)Time to peak (Tp) - from cortical ROInormal < 5 minRCA20 (20 min/peak ratio) - from cortical ROInormal < 0.3
67 ACEI Renography Diagnostic Criteria MAG3: ipsilateral parenchymal retention p.C.change in renogram curve by 1 gradeRCA20 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 uptakeDecrease in relative uptake 10% (e.g.from 50/50 to 40/60), change of 5-9% - intermediatechange in renogram curve by 2 gradesConsens. report JNM ‘96:1876 Semin NM 4/99:
68 ACEI Renography Interpretation High probability RVH (>90%)Marked C-induced changeLow probability RVH (<10%)Normal Captopril scanAbnormal baseline, improved p-C.Type I curve - pre- and post-C.Intermediate probability RVHAbnl baseline, no change p-C.
79 UTI VUR PN may lead to scarring >>> ESRD, HTN risk factor for PN,not all pts w PN have VURPN may lead to scarring >>> ESRD, HTNearly Dx and Rx necessaryClinical & 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 TracersTc-99m DMSATc-99m GHAAcquisition2-4 hrs post-injectionparallel hole posteriorpinhole post. + post. oblique (or SPECT)Processing: relative fct
82 Renal Cortical Scintigraphy Interpretation Acute PNsingle or multiple “cold” defectsrenal contour not distorteddiffuse decreased uptakediffusely enlarged kidney or focal bulgingChronic PNvolume loss, cortical thinningdefects with sharp edgesDifferentiation of AcPN vs. ChPN unreliable
94 Indications Evaluation of children with recurrent UTI 30-50% have VURF/U after initial VCUGAssess effect of therapy / surgeryScreening 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 catheterinfo on kidneysneed pt cooperationneed good renal fctTc-99m S.C. or TcO4via Foleycan do at any ageVUR during fillingcatheterizationAdvant.Disadv.
96 Direct Cystography 1 mCi S.C. in saline via Foley Fill bladder until reversal of flow(bladder capacity = (age+2) x 30Continuous imaging during filling & voidingPost void imageRecordvolume instilledvolume voidedpre- and post- void cts
97 RN Cystogram vs. VCUG Advantages Disadvantages Lower radiation dose (5 vs 300 mrad to ovary)Smaller amount of reflux detectableQuantitation of post-void residual volumeCannot detect distal ureteral refluxNo anatomic detailGrading difficult