Pediatric Surgery - DMSA and DTPA Scan mainly for PUJO and VUR

1. Renal Isotope Scan
Dr Bhanumurthy Kaushik M.
Senior Resident – Pediatric Surgery
Institute of Medical Sciences
Banaras Hindu University, Varanasi

2. Renal Evaluation
• History and Examination (decreased urine output / facial puffiness /
anasarca)
• Urine routine microscopy
• Albumin
• Casts
• Blood Urea
• Serum Creatinine

3. • Ultrasound
• Size (length / width)
• Thickness (cortical / parenchymal)
• Pelvis (size and AP diameter)
• Corticomedullary differentiation
• CT Scan
• CT KUB
• CTU or CT IVU or CT IVP
• Plain Xray KUB
• Xray dye studies
• Intravenous Urogram / Pyelogram
(IVU/IVP)
• Retrograde Pyelography /
Pyeloureterography
• Urethra Study
• Ascending or Retrograde
Urethrography
• Descending or Voiding or Micturating
Cystourethrography

4. All the mentioned imaging modalities can show the anatomy of the kidneys and KUB
only
The function of the kidneys (GFR) and the differential function of the kidneys cannot
be assessed by these routine imaging modalities
Furthermore, the non-functional regions of the kidneys cannot be assessed as well

5. Renal Isotope Scan – Renal Scintigraphy
• Department of Nuclear Medicine – Diagnostic / Therapeutic
• Isotopes = Same element with different mass (difference in the
number of neutrons – Hence additional properties)
• Unstable nucleus – results in decay – alpha, beta or gamma rays emitted
• Scintillation = Flash or Sparkle of light (because of rays emitted)
• Carrier molecule directs the isotope to the tissue which is desired to
be studied i.e. target organ
• Radiopharmaceutical = Radio-isotope + Carrier molecule
• Radio-Isotope produces the sparkle
• Gamma Camera – identifies the sparkle of the isotope

6. • Iodine is element
• Iodine 131 = Radio-isotope
• Radio Pharmaceutical for renal
study
• OIH = ortho Iodo hippuric acid
Technetium-99 is preferred
because of its shorter half life for
gamma emission (6 hours) and
approximately 94% of it decays in
24 hours

7. • Technetium is element
• Technetium 99 = Radio-isotope
• Carrier molecule or Ligand (for
Renal Study)
• DMSA = Dimercapto Succinic
Acid
• DTPA = Diethylene Triamine
Penta-acetic acid
• MAG3 = Mercapto Acetyl
Triglycine

8. Mechanism of Carrier molecule

9. Mechanism of Carrier molecule (contd.)
Pharmaceutical Property Renal Handling Application
DMSA Tightly binds to renal tubular cells
and only small amount is excreted
into urine
Localizes and binds to
Proximal convoluted tubules
Excellent visualization of renal
parenchyma – Renal
Parenchymal imaging
DTPA Little plasma protein binding and
cleared ‘almost’ exclusively by
glomerular filtration
GFR dependent for clearance
(hence results are suboptimal
in immature kidneys or in low
GFR or in patients with
compromised renal function)
Excellent visualization of PCS,
Ureter and bladder –
Renography
MAG3 90% bound to plasma protein and
principally cleared by tubular
secretion. Shows both parenchyma
and collecting system
Principally cleared by tubular
secretion
Renography –
1. Requires comparatively low
radiation dose
2. Can be used in low GFR /
immature kidneys
3. Both parenchyma and
collecting system visualized

10. Procedure
• Pre-requisite, Patient has to be adequately hydrated before the
procedure
• Radiopharmaceutical is initially taken (in desired dilution)
• Before injecting – the pharmaceutical is placed in front of Gamma
camera to identify the number of Radioisotopes being injected into
the patient
• Once injected, (during) the camera which is already placed behind the
patient is used to identify and quantify the pharmaceutical reaching
the tissue of interest

11. Procedure (continued)
• The target organ here is the Kidney
• The isotopes reaching both the kidneys can be identified separately
• Lasix might be or might not be injected (to let the pharmaceutical be filtered
out fast) – as per the protocol being used
• After the required images are captured, the residual pharmaceutical
left in the syringe is calculated by placing Infront of gamma camera
• Images are generated and computed by the computer

12. Administration of Pharmaceutical
Distribution
Emission
Detection
Image formation (by computer)
Overview of Procedure

13. Phases of Renal Scintigraphy
Perfusion Phase or
Vascular Transit
Phase
(One)
First passage of
radioactive bolus into
kidney
Blood flow and initial
uptake
Parenchymal Phase
or Tubular
concentration Phase
or Extraction Phase
(Two)
Filtration and/or secretion
of the RP from the blood
into the nephron – Before
any excretion
Tissue function
Excretory phase
(Three)
Passage of dye into
collecting system
Noted by downslope
Drainage
Is there a Phase Zero?

14. Time Activity Curve =
Graphical Representation of the Phases

17. Time To Peak – TTP or Tmax
• The time to peak refers to the time from radiopharmaceutical
injection to the peak height of the renogram curve.
• 99mTc-MAG3 and 99mTc-DTPA renograms normally peak by 5 min
• Delayed Tmax indicated ?Renal perfusion issues

18. Concept of ‘t’ half (t1/2)
• The time taken for half of the radionucleotide to be cleared from the
renal pelvis is termed as (t half) T1/2
• Usually in the absence of obstruction – half of the radionucleotide is
cleared from the renal pelvis within 10 to 15 minutes i.e. t1/2= 10 to
15 min.
• t1/2 > 20 minutes indicates obstruction
• t1/2 < 15 min. generally considered to be normal
• t1/2 between 15 to 20 minutes is indeterminate

19. Residual Cortical Activity – RCA
• To determine the activity remaining at the cortical region 20 minutes
post injection of radiopharmaceutical
• RCA is calculated by 𝐶𝑜𝑟𝑡𝑖𝑐𝑎𝑙 𝐶𝑜𝑢𝑛𝑡𝑠 𝑎𝑡 20 𝑚𝑖𝑛𝑢𝑡𝑒𝑠 ÷

20. Furosemide (Lasix) Protocol
• To hasten the process of renal excretion a diuretic = Furosemide is
injected to the patient
• Dose = max of 1mg/kg
• F + 20 protocol = Lasix is injected after 20 minutes of administering
the radiopharmaceutical. This is conventionally performed.
(corresponding with the t1/2 as previously discussed)
• F 0 protocol = Lasix is injected at the same time as
radiopharmaceutical
• F - 15 protocol = Lasix is injected 15 minutes before the
radiopharmaceutical
• F + 10, F + 15 protocols are also followed in some regions

21. Variations in TAC
F + 20 Protocol was followed

22. O’Reilly Classification of MAG3 TAC:
Type A = Normal
Type B = Obstructed
Type C = Dilated, Non Obstructed
Type D = Partially Obstructed

23. Variations in TAC (contd.)

24. Color Coding – Lt and Rt Kidneys

25. Differential Renal Function = Simple math
• Sparkles noted before injection – (minus) Sparkles left over in syringe
after injection = Actual amount of Radiopharmaceutical injected into
the patient (say x)
• Sparkles noted in Left kidney (say a) and Sparkled noted in Right
kidney (say b) are identified by the gamma camera separately
• Hence Differential Renal Function (DRF) is easily calculated
• Left Kidney function = a/x
• Right Kidney function = b/x

26. Patient 1

30. Patient 2

35. PCN was placed

40. Indication for Surgical intervention in PUJO
• Differential Renal Function <35 to 40%
and
• t1/2 of > 20 minutes
and
• Ultrasound finding consistent with Anatomical obstruction