Most common forms of congenital hydronephrosis
- • Ureteropelvic junction (UPJ) obstruction.
- • UVJ obstruction, commonly referred to as primary megaureter.
- • VUR.
- • Renal and ureteral duplication anomalies.
- • Posterior urethral valves.
- • Prune-belly syndrome.
When should a postnatal renal and bladder Ultrasound examination be obtained in a patient with congenital hydronephrosis?
A postnatal renal and bladder US examination should be performed on any infant with dilation of the renal pelvis that is detected prenatally on US, if the renal pelvis measures 4 mm or greater before 33 weeks of gestation and 7 mm or greater after 33 weeks of gestation. A renal pelvic diameter less than 4 mm seen on US at birth has been shown to normalize spontaneously within 1 year. In boys with bilateral hydroureteronephrosis, US should be obtained soon after birth to assess for presence of posterior urethral valves. Otherwise, the initial US examination should be performed at 5 to 7 days after birth (when the glomerular filtration rate is greater than it is immediately after birth).
What are the roles of renal scintigraphy, VCUG, intravenous urography (IVU), and magnetic resonance urography (MRU) in congenital hydronephrosis?
VCUG is performed to assess for VUR and to determine whether posterior urethral valves are present (in boys). Use of renal scintigraphy and IVU varies from patient to patient and from institution to institution. Renal scintigraphy provides quantitative information regarding the effects of obstruction upon renal function; the function of the obstructed kidney can be compared with the opposite kidney before and after surgical treatment. IVU provides less quantitative information but provides better anatomic detail. It serves best as a road map for the surgeon and gives information about anatomy and function after surgery. MRU is a static and dynamic technique that provides both morphologic and functional information of the dilated urinary tract in a single scan session without the use of ionizing radiation