Dr. Vivek M. Rege
Pediatric Surgeon & Pediatric Urologist, B J Wadia Hospital For Children, Hurkisondas Hospital, Wockhardt Hospital, Mumbai, India
First Created: 01/10/2001  Last Updated: 08/01/2015

Patient Education

This is a condition in which one or both sides' kidneys in a child get enlarged due to excessive accumulation of urine. The cause of the accumulation is an obstruction to the onward passage of urine to the bladder. To get a better idea of what I am trying to say - let us get the basics right.

There are normally 2 kidneys in each human and are situated in the back of the abdominal cavity. The kidneys are responsible for producing urine. The kidney is made up of 2 parts - the solid part called parenchyma that is the place where the formation of urine occurs. The second part is the collecting system - the pelvis of the kidney where the urine is excreted. From the pelvis of the kidney, the urine then flows into a tubular structure called the ureter that connects the pelvis to the urinary bladder below. The bladder is the storehouse for urine before it is evacuated by the child through the urethra.



Accumulation of urine in the pelvis is abnormal and usually occurs if there is an obstruction to the flow from the pelvis into the ureter and bladder, or, to put it another way, if the volume of urine exceeds the volume that can normally be accommodated in the pelvis - the latter will stretch and expand to allow the urine build up within. This dilatation of the pelvis is called Hydronephrosis. The commonest cause of hydronephrosis in children is due to obstruction to the flow of urine from the kidney pelvis to the ureter and bladder. The urine accumulates in the pelvis; more urine is formed every minute and this accumulation continues to cause the pelvis to stretch like a balloon filled with water. If the obstruction is very severe gradually this will cause back pressure on the substance or parenchyma of the kidney that produces the urine. If the obstruction is not relieved, the function of the kidney will progressively decrease. The recoverability of the kidney function after relief of the obstruction depends on how long and how severe it was. The commonest site of obstruction is at the junction of the pelvis and the ureter, and this is usually present since birth. The narrowing is at the junction which may be adequate to allow minimal quantities of urine to pass in the newborn and infant stage - if it is not severe; as the child grows, the kidney and the volume of urine produced per minute will also increase but the junction may not increase by the same proportion and hence accumulation of urine will now cause dilatation of the pelvis. When the limit of stretching of the pelvis is reached, the pressure will now fall on the renal substance and with time this will begin to thin out due to pressure of the urine. This then affects the function of that kidney. Other reasons for pelvic dilatation could be a stone in the kidney that may obstruct the flow of urine.

Figure 2: Site of obstruction at junction of pelvis & ureter

Site of obstruction at junction of pelvis & ureter

How does one suspect and diagnose this condition?

This may be very easy if the child presents with a mass in the abdomen that can be seen and felt. This will lead to investigations and diagnosis. However, some children may present with recurrent abdominal pain or episodes of urinary infection. This child must be shown to a doctor who may suspect a renal problem and ask for some basic investigations after a detailed examination of the child.


The first investigation is an Ultrasound of the abdomen. The kidney on the affected side will show a dilated pelvis, the thickness of the parenchyma of that kidney will be remarkably thinned out. The ureter may not be seen, or, if seen will be normal. This will show that the obstruction is proximal to the ureter.

Figure 3: Sonography shows large dilated(dark) pelvis

Sonography shows large dilated (dark) pelvis

However, a dilated pelvis does not always mean obstruction, so a second investigation to confirm obstruction is required. A Radio Nuclear Scan DTPA is a must. This investigation gives a lot of information useful for knowing the individual function of the 2 kidneys, also after therapy, the Scan should show that the function of that kidney has improved. This will be a clear indication that the treatment has helped and the function has recovered. Thus, this investigation will show how less the function has come down, how severe is the obstruction and based on these the decision to operate or not is taken. Routine investigations for any major surgery are carried out before posting the child for surgery.



Surgery for the obstruction is done thru an anterior approach and the kidney and pelvis are approached to reveal the site of obstruction. Part of the dilated pelvis and upper part of the narrowed ureter is removed and the remaining pelvis and the ureter are joined together with fine sutures to allow the urine to pass easily into the bladder. The back pressure on the kidney substance is taken away and now the kidney function can start recovering. The time taken for recovery may vary and a follow up of at least 3 years is necessary to determine the recoverability of the renal function.



Complications of this surgery are the common wound infection, rupture, and leakage of urine from the junction where the pelvis and ureter have been newly joined. The child will have tubes across the anastomosis to prevent this and can be removed later. The hospital stay will be about 8 days only. A renal DTPA Scan must be done after a year to know the difference caused by the surgery and must be repeated every year to confirm the betterment of function.

Figure:Child who was operated at 2 months of age - barely visible scar

Child who was operated at 2 months of age - barely visible scar

Hydronephrosis Hydronephrosis https://www.pediatriconcall.com/show_article/default.aspx?main_cat=pediatric-nephrology&sub_cat=hydronephrosis&url=hydronephrosis-patient-education 2015-08-01
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