Hydronephrosis in children

What is it?

Dilatation of the collecting system of the kidney observed in the standard transverse view of the abdomen. Ureters and bladder are normal.
On the basis of the anteroposterior diameter of the pelvis the condition is divided into:
Mild (only renal pelvis): 4-7 mm in the 2nd trimester; 7-9 mm in the 3rd.
Moderate (pelvis and calyces): 8-10 mm in the 2nd trimester; 10-15 mm in the 3rd.
Severe (cortical thinning): >10 mm in the 2nd trimester; >15 mm in the 3rd. Associated abnormalities:
Chromosomal defects: low risk in isolated forms.
Abnormalities of the contralateral kidney: multicystic kidney, ectopia, renal agenesis.
Associated syndromes are found in 5% of cases. 

Causes and risk factors

Pyeloectasis may be a paraphysiologic enlargement, that is neither normal nor pathologic, which can resolve spontaneously without damage to the kidney.

In other cases, this may be a sign of some malformation of the urinary system, such as:

  • stenosis of the pylor-ureteral junction: narrowing of the junction between the renal pelvis and the ureter, which causes urine to accumulate in the renal pelvis and dilate it;
  • vesicoureteral reflux: urine flows from the bladder back into the kidney;
  • megaureter: enlargement of the ureter due to narrowing of the junction between the ureter and the bladder;
  • ureterocele: enlargement of the ureter in the bladder due to narrowing of the urinary outlet to the bladder;
  • problems with the valves of the posterior urethra: mucous membranes in the male urethra that obstruct the flow of urine and can cause urine to accumulate in the bladder, ureters, and renal territories.

Among these, pyeloureteral junction syndrome and vesicoureteral reflux are the most common causes.

Acquired diseases, such as a urinary stone, can also cause pyeloectasia.

Which are the symptoms?

This isolated pathological condition of the fetus is not associated with pathological conditions of the mother.

How is it diagnosed?

Detailed ultrasound examination (especially of the contralateral kidney).
Karyotyping should be offered only if other markers are present. 

Suggested exams

How is it treated?

In the majority of cases, the condition remains stable or resolves in the neonatal period. In about 20% of cases, there may be an underlying ureteropelvic junction obstruction or vesicoureteric reflux that requires postnatal follow-up and possible surgery. Moderate hydronephrosis is usually progressive and in more than 50% of cases surgery is necessary during the first 2 years of life.

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