Campbell-Walsh Urology, 11th Edition

PART XV

Pediatric Urology

SECTION B

Basic Principles

126

Pediatric Urogenital Imaging

Hans G. Pohl; Aaron D. Martin

Questions

1. Areas of renal scarring on dimercaptosuccinic acid (DMSA) scan have the following characteristic appearance:
2. photon-intense lesion with normal reniform shape preserved.
3. photon-deficient lesion without preservation of reniform shape.
4. photon-deficient lesion with normal reniform shape preserved.
5. photon-intense lesion without preservation of reniform shape.
6. photon-deficient lesion located centrally.
7. A 6-year-old child with grade 4 hydronephrosis found on ultrasound after a urinary tract infection (UTI) is referred for evaluation. No stones are seen on the study, and there is no hydoureter. The following test should be performed:
8. MAG-3 diuretic renography.
9. computed tomographic (CT) urogram.
10. intravenous pyelogram (IVP).
11. retrograde pyelogram.
12. repeat ultrasonography.
13. A 14-year-old presents to the emergency department at 1 amwith sudden-onset, severe left testicular pain, swelling, and nausea with one episode of emesis. He has been in pain for 7 hours at the time you evaluate him, and no imaging has yet been performed. The next step is:
14. call for ultrasonography to come in to confirm torsion.
15. reassure the patient this is likely epididymitis and give a trial of nonsteroidal anti-inflammatory drugs (NSAIDs).
16. obtain urinalysis, treat empirically with antibiotics, and send home with narcotic pain meds.
17. take him immediately for surgical exploration.
18. obtain testicular scintigraphy to differentiate between torsion and an inflammatory process.
19. Technetium-99 m (^99mTc)-dimercaptosuccinic acid is taken up by which renal cells?
20. Thin segment loop of Henle
21. Glomerulus
22. Proximal tubule
23. Distal tubule
24. Collecting tubule
25. A 1-year-old boy is referred to your office for a right undescended testicle. The examination reveals a normal left descended testicle and a nonpalpable right testicle. The next step is:
26. obtain a scrotal/pelvic ultrasound to determine the presence and/or location of the nonpalpable gonad.
27. obtain pelvic magnetic resonance imaging (MRI) to determine the presence and/or location of the nonpalpable gonad.
28. obtain testicular scintigraphy to determine the presence and/or location of the nonpalpable gonad.
29. proceed to surgical exploration for cryptorchidism without further imaging.
30. have the child return in 6 months for repeat examination and consider hormonal therapy to encourage spontaneous descent.

Answers

1. b. Photon-deficient lesion without preservation of reniform shape. A scar on DMSA scan will create a defect in the reniform shape, whereas acute pyelonephritis will simply be a photon-deficient area with preserved reniform borders.
2. a. MAG-3 diuretic renography.This child's sonogram is concerning for ureteropelvic junction obstruction. MAG-3 diuretic renography will provide quantitative functional and descriptive anatomic information that cannot be ascertained in full by the other modalities.
3. d. Take him immediately for surgical exploration.Testicular torsion is a clinical diagnosis and does not require imaging unless the exam and symptoms are equivocal. Surgical therapy should not be delayed for imaging if the clinical picture is indicative for torsion.
4. c. Proximal tubule.DMSA is taken up and bound to the proximal tubules allowing for the best and most reliable imaging of the renal cortex. MAG-3 is filtered and also taken up by the proximal tubules but not bound, allowing rapid clearance to assess drainage of the collecting system.
5. d. Proceed to surgical exploration for cryptorchidism without further imaging.Per American Urological Association cryptorchidism guidelines, imaging rarely assists in decision making in these cases because of poor sensitivity and specificity, and therefore should not be obtained. Hormonal therapy has low response rates and little evidence of long-term efficacy. If the 6-month examination does not reveal spontaneous descent, it is recommended that an orchiopexy be performed within 1 year.

Chapter review

1. The benign nature of MRI exposure in the child has been questioned based on changes in gene expression that occur related to the magnetic field.
2. On renal ultrasound in the newborn, the renal cortex is slightly hypoechoic with discrete interfaces between cortex and medulla.
3. In cystic disease of the kidney, the cysts do not communicate, unlike the "cysts"(dilated calyces) in a hydronephrotic kidney, which do communicate.
4. Ultrasound for the evaluation of the routine cryptorchid testis is not indicated.
5. A DMSA scan that reveals an area of photon deficiency in the acute setting is consistent with acute pyelonephritis, whereas a photopenic area that lasts more than 6 months is likely a renal scar. Also, a scar on DMSA will create a defect in the reniform shape, whereas acute pyelonephritis will simply be a photon-deficient area with preserved reniform borders.
6. Diuretic renography may be falsely positive due to dehydration or lack of bladder drainage; there are no established T_1/2values in young children, and it is the character of the curve that suggests the diagnosis.