Key imaging findings in posterior urethral valves. From Merrow AC Jr. Diagnostic Imaging: Pediatrics. 3rd ed. Elsevier; 2017.

1. Posterior urethral valves
– imaging findings

2. fold / membrane just distal to prostatic urethra
exclusively in males
requires urgent endoscopic valve ablation

3. Best imaging tools
prenatally
fetal US
fetal MRI
postnatally
voiding cystourethrogram – VCUG
cystosonography – CSG

4. VCUG
dilated posterior urethra with abrupt transition
to anterior urethra at level of valve
valve sometimes not seen
 does not preclude diagnosis

5. VCUG
signs of chronic bladder obstruction
dilation
wall trabeculation
diverticula
patent urachus

6. VCUG
vesicoureteral reflux
 hydroureteronephrosis
 urinoma

7. CSG
filling of bladder with US contrast
imaging during voiding
remove urethral catheter while voiding +/-
transperineal approach
or across pubic symphysis

8. CSG
keyhole sign
dilated bladder and posterior urethra
chronic bladder obstruction
thick trabeculated wall with diverticula
kidneys
hydroureteronephrosis
cystic dysplasia
urinoma

9. Remember
VCUG – dilated posterior urethra with abrupt
transition to anterior urethra
CSG – key hole sign