Posterior Urethral Valves in Boys: Ultrasound Features in Megacystis and Hydronephrosis
Ultrasound Findings
According to the Textbook of Diagnostic Sonography (Hagen-Ansert, 2023), posterior urethral valves demonstrate the following complex of changes:
- Dilated urinary bladder, dilated ureter, and dilated prostatic urethra.
- Dilation of the renal pelvis.
- Dilation of the central calyces, possibly with involvement of peripheral calyces.
- The ureter is dilated in the presence of vesicoureteral reflux or primary megaureter.
Clinical Features
According to the source, PUV may be clinically accompanied by decreased urine output, pulmonary hypoplasia, and Potter facies. Association with Prune-Belly Syndrome is possible: absence of abdominal wall muscles and undescended testes.
Differential Diagnosis
Within the differential diagnosis of obstructive uropathy and hydronephrosis (UTD/Hydronephrosis) per Hagen-Ansert (2023), the following conditions are considered:
| Condition | Comment |
|---|---|
| Multicystic Dysplastic Kidney | Multicystic Dysplastic Kidney |
| Prune-Belly Syndrome | Absence of abdominal wall muscles, cryptorchidism |
| Congenital Mesoblastic Nephroma | Children under 1 year, palpable mass |
| Adrenal Hemorrhage | Jaundice, anemia, mass lesion |
In megaureter (ExpertDDx, 2023), massive bilateral dilation of the distal ureter is noted; with ureterocele, a cystic outpouching is visualized at the ureteropelvic junction (cobra head sign). [clarification needed] — exact threshold values for bladder diameter and degree of hydronephrosis are not provided in the fragments.
Frequently asked questions
What ultrasound triad is characteristic of PUV?
Dilated urinary bladder, dilated ureter and prostatic urethra, as well as dilation of the renal pelvis and central calyces (Hagen-Ansert, 2023).
When is the ureter dilated in PUV?
The ureter is dilated in the presence of vesicoureteral reflux or primary megaureter (Hagen-Ansert, 2023).
What conditions should be differentiated from hydronephrosis when PUV is suspected?
Multicystic dysplastic kidney, Prune-Belly syndrome, congenital mesoblastic nephroma, and adrenal hemorrhage (Hagen-Ansert, 2023).
What clinical features accompany PUV?
Decreased urine output, pulmonary hypoplasia, Potter facies; with Prune-Belly — absence of abdominal wall muscles and undescended testes (Hagen-Ansert, 2023).
How can ureterocele be differentiated on ultrasound?
A cystic outpouching at the ureteropelvic junction—cobra head sign (ExpertDDx, 2023).