Role of Nuclear medicine in genitourinary system

1. RENAL SCINTIGRAPHY Dr. Lubaina Omer

2. INDICATIONS
Renal cortex : Scarring , acute pyelonephritis
Renal obstruction : Hydronephrosis –diuretic administered scan.
Renal Transplant
Renovascular hypertension: ACE- inhibitor administered scan.
VUR
Calculation of GFR

3. RADIOTRACERS
Cortically bound: DMSA (Tc-99m dimercaptosuccinic acid), Tc- 99m glucoheptonate.
Secreted by tubules : MAG-3 (Tc-99m mercaptoacetyltriglycine)
Filtered : DTPA ( Tc- 99m diethylene triamine pentaacetic acid), I- 131 hippuran

4. RENAL SCAR AND PYELONEPHRITIS – RENAL
MORPHOLOGY SCAN
Protocol- DMSA
Scan taken 2 hours post injection- 40- 65 % bound to cortex.
Dose: 0.04-0.05 mCi /kg
Acquisitions: Posterior and anterior supine image , pinhole posterior or SPECT.

5. Imaging findings
Pyelonephritis induced scar:
Acute pyelonephritis: Striated appearance , extends toward hilum.
Post pyelonephritis : Cortical defects present which resolve by 6 weeks ( diff from scar)
VUR induced scar
Recommendation : VUR > Grade III . Recurrent UTI
Found in >58 % with first time acute pyelonephritis.
High grade VUR without UTI – scars seen in 65%

6. DIFFERENTIAL DIAGNOSIS
Pyelonephritis – Photopenic defects extending to hilum.
Cortical scar – Photopenic defects are more superficial.
Renal masses – Focal region of absent uptake and mass effect.
Renal cyst – Discrete round rounded focus with absent uptake.
PAN – Striated appears – mimcs AP
Fetal lobulation – may mimic scar.
Splenic impression- may mimic a scar along the anterior aspect of left renal upper
pole.

10. HYDRONEPHROSIS-
Protocol- Tc 99m MAG 3
Patient preparation- Hydrate with IV Fluids, Furosemide to be avoided on day of exam, Void
prior to study.
Dose: Adults – 10 mCi
Children- 0.05 mCi / kg
Acquistions: Supine
Angiographic phase : 1-2 sec images for 1-2 min
Dynamic sequence : 15- 60 sec images for 20- 30 min
Diuresis sequence : after furosemide additional 15-60 sec images taken for 20- 30 min.
Post Void images.

11. IMAGING FINDINGS , DD AND RENOGRAM CURVES

15. VESICOURETERAL REFLUX
Protocol – Tc 99m pertechnetate
Void prior procedure, bladder catheterised.
Dose : bladder volume – [age in years + 2] x 30 cc
Bolus administered into the bladder.
Acquisitions :
Posterior images of pelvis and abdomen
Anterior images included if residual volume needs to be calculated.
Dynamic images on filling and voiding.
Static images of pre and posterior void .

16. IMAGING FINDINGS
Reflux of Tc-99m pertechnetate from bladder intoureter &/or renal collecting system
on filling or voiding
Dynamic images during filling and voiding increases detection of VUR, including
transient reflux
Difficult to grade VUR on nuclear cystogram due to lack of anatomic resolution
– Qualitatively reported as mild, moderate, or severe

17. DIFFERENTIAL DIAGNOSIS
Radiotracer Contamination
Contamination may occur with urination, radiotracer activity on skin or in diaper-
May mimic VUR on nuclear cystography
Bladder Diverticulum
Primary (congenital defect, protrusion through bladder wall) or secondary
(obstruction, neurogenic dysfunction)- May mimic VUR on nuclear cystography

21. RENAL TRANSPLANT EVALUATION
Protocol-
Radiotracer
Tc- 99m MAG3: Adults-10 mCi
Pediatrics- 0.05-0.1 mCi /kg–
Tc-99m DTPA( 2nd line)
Tc-99m DMSA: Adults- 5 mCi
pediatrics- 0.05-0.1 mCi/kg
Positioning arm at 90° angle to body will minimize axillary retention of tracer
Diuretic: Furosemide (0.5 mg/kg, max 40 mg in adults, 1
mg/kg in pediatrics) if obstruction suspected; administer 20-30 min after radiotracer injection.

22. IMAGING FINDINGS AND INTERPRETATION
Perfusion to allograft: Normally within 4 sec of radiotracer bolus passing through iliac
artery
Normal peak cortical activity 3-5 min post injection
Normal renal transit: Tracer in collecting system, bladder by 6 min
By end of exam, cortex should clear or be significantly less than early in exam if no cortical
retention
Cortical retention seen in ATN, Acute and Chroic Rejection.
Cortical loss and dilated pelvis helpful identifiers in Chronic Rejection

23. DIFFERENTIAL DIAGNOSIS
Vascular complications
Renal vein thrombosis (RVT):
Transplant RVT: Lack of draining collaterals, overall perfusion ↓ causing absent or
photopenic transplant.
Native kidney RVT: Large, hot kidney as activity accumulates in but does not clear
Renal artery thrombosis: Absent function.
Patchy if distal; Tc-99m DMSA renal scan can be useful
RAS: Typically late complication

24. Acute Tubular Necrosis
Classically presents with relatively preserved perfusion and delayed
uptake/excretion (tubular agents)
Abnormal baseline renal scan at 24 hr (AR typically occurs
later)
Bladder activity classically absent-background activity increases over time (e.g.,
gallbladder with MAG3)

25. Acute Rejection
Perfusion in AR generally worse than function:
↑ cortical retention compared with baseline from 1 week to < 1 year: Sensitive, fairly specific
for AR
Chronic Rejection
Rare in transplant < 1 year unless prior episodes of severely compromised function
1st sign: ↓ blood flow, relatively spared function
Over time, cortical thinning with worsening uptake and clearance develop, along with ↑
cortical dilation
Furosemide may help differentiate from obstruction

26. Drug Toxicity
Calcineurin inhibitors (cyclosporine and tacrolimus) cause nephrotoxicity through
arteriolar vasoconstriction and tubulointerstitial injury
Imaging appearance is similar to and difficult to distinguish from ATN ○
Typically presents later than ATN

27. Surgical Complications
Obstruction: May occur from days to years postoperatively
○ Activity in bladder from native kidneys may mask obstruction
○ Full bladder or reflux may mimic obstruction: Empty bladder critical for renal
scan
Urinoma/urine leak: Days to weeks postoperatively
Lymphocele: Typically 2-4 months postoperatively

31. RENOVASCULAR HYPERTENSION
Protocol- MAG-3 with ACE inhibitor
Patient preparation
Stop ACEI 3-7 days prior to exam
Also stop angiotensin II receptor blockers
Stop diuretics and calcium channel blockers, if safe
Hydrate before study
Empty bladder immediately before exam
Patient supine with camera posterior for native kidneys and anterior for renal
transplant.

32. Dose: MAG3 adult 1-10 mCi/kg
child 0.1 mCi/kg
DTPA adult 1-10 mCi/kg
child 0.1 mCi/kg
1-day or 2-day protocol depending on clinical suspicion or patient population
2-day protocol (low probability of disease): ACEI scan 1st; if abnormal, baseline scan 1-2
days later; routine
radiotracer dose used for each exam
1-day protocol (high probability of disease): low-dose baseline followed by high-dose
ACEI scan

33. ACEI
Captopril: 25-50 mg p.o. - monitor
blood pressure every 5-15 min for 1 hr
Wait 60 min to administer radiopharmaceutical
Enalapril: 40 μg/kg IV up to 2.5 mg given over 3-5 min
Wait 15 min to administer radiopharmaceutical
Diuretic: Furosemide (20 mg) during imaging may improve accuracy of exam

34. IMAGING FINDINGS
Baseline Tc-99m mercaptoacetyltriglycine (MAG3) renogram (without ACEI)
Blood flow usually not perceptibly altered; nonspecific
small kidney or ↓ function could be seen but scan often normal
• ACEI renogram: Excellent detection of clinically significant RAS; sensitivity > 90%
and specificity 95% in those withgood renal function
Patients without RVHT show no significant change from baseline
Functional deterioration after ACEI compared with baseline identifies patients with
reversible RVHT

35. Time-activity curves and renal-function images will vary depending on
radiopharmaceutical agents
Renogram using Tc-99m DTPA: Shows overall decrease in uptake and function of
kidney with RAS after ACEI
Renal excretion of DTPA exclusively by glomerular filtration and directly reflects
glomerular filtration rate
Renogram using Tc-99m MAG-3: Shows significant cortical retention of radiotracer
in kidney with RAS after ACEI
MAG-3 excreted by tubular secretion, so drop in GFR does not affect uptake

38. THANKYOU ☺