Pictorial Review of Urinary Tract Obstruction in Tc-99m MAG3 Renograms with Diuretic Kushal Joshi, University Hospitals of Leicester Tauseef Ashraf, Pilgrim Hospital, Boston MAG3 Renogram • Tc-99m MAG3 renograms are commonly used to assess renal outflow tract obstruction. • The radiopharmaceutical (Tc-99m MAG3) is administered intravenously. • Its arrival into the kidneys and excretion is monitored. • Time activity curves provide graphical representation of renal uptake and excretion. Relative renal function can also be quantified. • Post diuresis imaging, after administration of furosemide, can distinguish between complete obstruction, partial obstruction or dilated but non-obstructed systems. Normal Renogram: 3 Phases 1. Flow Phase - Sharp upslope - Slow upslope suggest reduced perfusion 2. Cortical Phase - Peak of the renogram (1-3 minutes) - Decreased renal function produces delayed cortical uptake 3. Clearance Phase - Rapid excretion (after 3 minutes) A normal MAG3 renogram. The tracer clears from the collecting system without need for diuretic. Case 2b: Partially Obstructed Left Kidney The patient from Case 2a, went on to have an open left pyeloplasty. A repeat MAG3 renogram demonstrates retained activity in the left kidney. However, it now responds to IV furosemide which indicates a partially obstructed system. References 1. Mandell, J. (2018). Core radiology. Cambridge: Cambridge Unversity Press, p.582. 2. Eskild-Jensen A, Gordon I, Piepsz A, Frøkiaer J. Interpretation of the renogram: problems and pitfalls in hydronephrosis in children. BJU Int. 2004 Oct;94(6):887-92. Case 1: Bilateral Renal Outflow Obstruction - There is asymmetric uptake in the two kidneys, R<L. - Causes of asymmetric, decreased uptake in one kidney, could be due to renal artery or venous thrombosis, chronic obstruction or infections. - Both kidneys show reduced upslope of the flow phase suggestive of reduced renal perfusion. - Delayed cortical uptake implies impaired renal function - Retention of activity in both kidneys in the clearance phase with no significant response to IV frusemide suggests bilateral outflow tract obstruction - Below, CT of the same patient shows gross right PUJ dilatation and there is also left hydronephrosis Case 2a: Obstructed Left Kidney - The flow phase and cortical phase are normal. - Left kidney shows retention of activity in the clearance phase which does not respond to IV furosemide - The left kidney is obstructed as can also be seen in the dynamic planar images. Case 3: Dilated But Unobstructed Left Kidney - Normal flow and cortical phases in both kidneys - There is slow clearance in the left kidney which continues post furosemide in keeping with a dilated but unobstructed system. R L L L L R R R R R L L L R Flow Cortical Clearance

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Page 1: Pictorial Review of Urinary Tract Obstruction in Tc-99m ... · Pictorial Review of Urinary Tract Obstruction in Tc-99m MAG3 Renograms with Diuretic Kushal Joshi, University Hospitals

PictorialReviewofUrinaryTractObstructioninTc-99mMAG3Renograms withDiureticKushal Joshi,UniversityHospitalsofLeicester

Tauseef Ashraf,PilgrimHospital,Boston

MAG3Renogram

• Tc-99mMAG3renograms arecommonlyusedtoassessrenaloutflowtractobstruction.

• Theradiopharmaceutical(Tc-99mMAG3)isadministeredintravenously.

• Itsarrivalintothekidneysandexcretionismonitored.• Timeactivitycurvesprovidegraphicalrepresentationofrenal

uptakeandexcretion.Relativerenalfunctioncanalsobequantified.

• Postdiuresisimaging,afteradministrationoffurosemide,candistinguishbetweencompleteobstruction,partialobstructionordilatedbutnon-obstructedsystems.

NormalRenogram:3Phases

1. FlowPhase- Sharpupslope- Slowupslopesuggestreducedperfusion

2. CorticalPhase- Peakoftherenogram (1-3minutes)- Decreasedrenalfunctionproducesdelayedcorticaluptake

3. ClearancePhase- Rapidexcretion(after3minutes)

AnormalMAG3renogram.Thetracerclearsfromthecollectingsystemwithoutneedfordiuretic.

Case2b:PartiallyObstructedLeftKidney

ThepatientfromCase2a,wentontohaveanopenleftpyeloplasty.ArepeatMAG3renogram demonstratesretainedactivity intheleftkidney.However,itnowrespondstoIVfurosemidewhichindicatesapartiallyobstructedsystem.

References1. Mandell,J.(2018). Coreradiology.Cambridge:CambridgeUnversity Press,p.582.2. Eskild-JensenA,GordonI,Piepsz A,Frøkiaer J.Interpretationoftherenogram:problemsandpitfallsinhydronephrosis inchildren.BJUInt.2004Oct;94(6):887-92.

Case1:BilateralRenalOutflowObstruction

- Thereisasymmetricuptakeinthetwokidneys,R<L.- Causesofasymmetric,decreaseduptakeinonekidney,couldbe

duetorenalarteryorvenousthrombosis,chronicobstructionorinfections.

- Bothkidneysshowreducedupslopeoftheflowphasesuggestiveofreducedrenalperfusion.

- Delayedcorticaluptakeimpliesimpairedrenalfunction- Retentionofactivityinbothkidneysintheclearancephasewith

nosignificantresponsetoIVfrusemidesuggestsbilateraloutflowtractobstruction

- Below,CTofthesamepatientshowsgrossrightPUJdilatationandthereisalsolefthydronephrosis

Case2a:ObstructedLeftKidney

- Theflowphaseandcorticalphasearenormal.- Leftkidneyshowsretentionofactivityintheclearancephase

whichdoesnotrespondtoIVfurosemide- Theleftkidneyisobstructedascanalsobeseeninthedynamic

planarimages.

Case3:DilatedButUnobstructedLeftKidney