2. Tc99M-MAG3 DIURETIC RENOGRAPHY IN PEDIATRICS: A PICTORIAL REVIEW
Mahmoud Zahra, MD, FRCR
Children’s Hospital Of Philadelphia
Feraas Jabi, MD
University at Buffalo

3. Disclosures
Authors have no financial disclosures

4. PURPOSE:
Review normal renal physiology as delineated by technetium99m- mercaptoacetyl triglycine (Tc99m-MAG3) scintigraphy.
Present traditional protocol for performing a Tc99m-MAG3 diuretic renogram at our institution.
Review qualitative and quantitative scintigraphic findings of obstructive uropathy on Tc99m-MAG3 renogram before and after diuretic challenge.
Review pertinent findings to be included in a Tc99m-MAG3 diuretic renogram report.
Present sample cases of Tc99m-MAG3 diuretic renograms with sonographic correlations.

5. Introduction
Technetium-99m mercaptoacetyl triglycine (Tc99m- MAG3) is an agent actively secreted by the renal tubules providing qualitative assessment of effective renal plasma flow
Tc99m-MAG3 scintigraphy widely used in pediatrics for evaluation of obstructive uropathy
Other indications include evaluation of acute renal failure and renal transplant function (acute tubular necrosis vs. acute rejection, cyclosporine toxicity, arterial occlusion, urinary obstruction or urinary leak)

6. Dynamic renography with Tc99m-MAG3 allows evaluation of three parameters of renal function:
Blood flow
Tubular function
Clearance into the collecting system

7. Technique 1.Patient Preparation:
Oral hydration is essential before arrival and while in the department
Bladder catheterization recommended but not necessary
Patient must remain still during the examination
Parent encouraged to be present to relieve patient anxiety
2. Radiopharmaceutical:
The recommended administered dose is 1.9 MBq (50 mCi) per kilogram

8. 3. Diuretic injection:
Loop diuretic furosmide (F) most commonly used
Administered intravenous (IV) dose is 1.0 mg/kg up to a maximum of 40 mg. A larger dose may be necessary in obese children, children with unilateral or bilateral renal impairment, or children chronically treated with diuretics
IV Furosemide takes effect within 1 to 3 minutes of administration

9. 3. Diuretic injection (contd):
3 methods for timing of furosemide injection
Furosemide injected 20 minutes or later following Tc99m- MAG3 injection (F + 20 or later); method used at our institution
Furosemide injected 15 minutes prior to Tc99m-MAG3 injection (F-15), common method in Europe
Simultaneous injection of furosemide and Tc99m-MAG3 (F – 0)
No clear advantage of one method over the other

10. 4. Image Acquisition:
Patient in supine position with back to the camera for serial dynamic 60 second images obtained in the posterior projection for 60 minutes
Initial flow images acquired immediately following first pass bolus injection of Tc99m-MAG3 for up to one minute.
This is followed by continuous dynamic imaging for evaluating renal concentration and clearance of Tc99m- MAG3
At our institution’s F+20 approach, the pre-F and post-F images are obtained as two separate acquisitions beginning with early flow images and continued for an additional minutes after furosemide administration

11. Interpretation of Findings
Visualization of Tc99m-MAG3 bolus from the abdominal aorta into the renal arteries required for adequate interpretation of renal blood flow
Delay in transit greater than 2-4 seconds from abdominal aorta to renal arteries indicates decreased renal perfusion
Symmetry of renal perfusion. Is there less blood flow to one kidney compared with the other?
Images of renal parenchymal (ie renogram) phase are used to evaluate tubular and clearance function
Dilated collecting systems (hydronephrosis, hydroureter) identified in excretory portion of renogram phase
Each kidney should take up 40-60% of injected Tc99m-MAG3. Less than 40% uptake indicates poor renal function
Time-activity curves (TACs) for flow and renograms before and after furosemide are generated after drawing regions of interest (ROIs) in the abdominal aorta, kidneys, and renal cortices.
Time to maximum renal cortical activity and time for half of maximum renal cortical activity to clear are important quantitative parameters derived for evaluation of renal cortical obstruction

12. Maximal cortical activity normally achieved within 5 minutes of Tc99m-MAG3 injection
Normal clearance to half of maximal cortical activity seen within 10 minutes of Tc99m-MAG3 injection
Rapid and near complete washout of Tc99m-MAG3 prior to furosemide injection indicates absence of obstruction. In such a situation, furosemide challenge can be waived
In obstruction, increasing activity over time proximal to site of obstruction is usually seen, provided preserved renal function
TAC following furosemide used to differentiate urinary stasis from mechanical obstruction

13. Pre-furosemide clearance time to one-half of maximal cortical activity of greater than 20 minutes diagnostic for obstruction provided prominent collecting systems are present and there is no renal parenchymal dysfunction.
Brisk clearance following furosemide most consistent with urinary stasis
Clearance time values between 10 and 20 minutes nonspecific and could represent partial mechanical obstruction, patulous but nonobstructed collecting systems, or urinary flow abnormality
Presence or absence of obstruction difficult to interpret in patients with renal parenchymal disease

14. Pitfalls
Patient motion degrades image quality in turn making ROI identification problematic for quantitative analysis
Dose infiltration of Tc99m-MAG3 around intravenous injection site results in suboptimal image acquisition
Insufficient hydration can result in delayed Tc99m-MAG3 flow, uptake, and excretion, hindering proper evaluation for obstruction
Large, unobstructed collecting system can exhibit slow clearance of Tc99m-MAG3
Caution must be exercised in interpretation of obstructive uropathy in the presence of significant renal parenchymal disease

15. A
(A)
Tc99m-MAG3 scan in a 9 month old infant with mild dilatation of renal collecting systems bilaterally. Normal symmetric blood flow to both kidneys B
(B)
TAC shows normal renal clearance

16. 6 month old infant with bilateral hydronephrosis on ultrasound (US) images A and B
Dynamic Tc99m-MAG3 scan shows normal symmetric renal perfusion, image C
Pre-furosemide renogram images show absent clearance by both kidneys, with rising activity on the TAC, image D
Post-furosemide TAC shows prompt bilateral renal clearance, image E
Conclusion: Urinary stasis without obstruction A B C D E

17. A B
7 month old infant with left hydronephrosis on US (not shown)
Tc99m-MAG3 scan shows normal symmetric renal perfusion, image A
Pre-furosemide TAC shows persistent elevation of activity in the left kidney
Right renal excretion, image B

18. C
Same patient in the previous slide. Left hydronephrosis, image C
Post diuretic TAC shows left excretion, image D
Conclusion: No obstruction D

19. 25 month old
child with
left hydronephrosis on US, image A
Dynamic Tc99m-MAG 3 shows normal renal perfusion, image B
TAC shows increasing activity
In left kidney without excretion, Image C B A C

20. Same patient in previous slide.
Images show left hydronephrosis, D
Post furosemide TAC shows mild
excretion of Tc99m-MAG3 by left kidney, clearance time to ½ of maximum cortical activity is 21 minutes consistent with
obstruction, image E D E

21. A
8 year old male child with left hydronephrosis, image A
Dynamic Tc99m-MAG3 scan shows split renal function, (41% left and 59% right), images B and C. B C

22. A
Static images show left hydronephrosis, image A
Post furosemide TAC shows elevated activity with minimal excretion, image B B

23. Same patient in previous slide, 2 months status post surgical repair of hydronephrosis.
There is persistent split renal function (40% left kidney and 60% right, image A)
There is improved excretion of activity
by left kidney, image B
US shows partially resolved hydronephrosis, image C A B C

24. B C A
16 year old male with history of single right hydronephrotic kidney shown on US, image A
Tc99m-MAG3 renogram shows increased activity without excretion, image B
Images show right hydronephrosis. Post furosemide TAC shows mild excretion with clearance time to ½ maximal activity of 17 minutes, image C

25. C B A Same patient on previous slide, 3 years later
US shows persistent hydronephrosis, image A
Tc99m-MAG3 images and TAC show increasing activity of right kidney with slight excretion, image B
Post furosemide images and TAC show mild
excretion with clearance time to ½ maximal activity of 32 minutes, indicating worsening obstruction, image C A

26. Conclusion
The vast majority of nuclear medicine imaging studies in the pediatric age group are interpreted by the pediatric radiologist. As such, a thorough knowledge of the underlying instrumentation and technique of nuclear imaging as well as normal renal physiology is essential in the identification of any functional abnormalities on Tc-MAG3 renograms. A concise yet informative Tc99m-MAG3 renal scan report as described here will assist the referring urologist in determining the next best step in managing a child with suspected obstructive uropathy, thereby optimizing patient care.

27. References
Barry L. Shulkin1, Gerald A. Mandell2, Jeffrey A. Cooper3, Joe C. Leonard4, Massoud Majd5, Marguerite T. Parisi6, George N. Sfakianakis7, Helena R. Balon8, and Kevin J. Donohoe9. Procedure Guideline for Diuretic Renography in Children 3.0*
Mohammed N Tantawy, Rosie Jiang, Feng Wang, Keiko Takahashi, Todd E Peterson, Dana Zemel, Chuan-Ming Hao, Hiroki Fujita, Raymond C Harris, Christopher C Quarles and Takamune Takahashi. Assessment of renal function in mice with unilateral ureteral obstruction using 99mTc-MAG3 dynamic scintigraphy
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Taylor A, Manatunga A, Halkar R, Issa MM, Shenvi NV .A 7% decrease in the differential renal uptake of MAG3 implies a loss in renal function
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