Antenatal (before birth) Hydronephrosis is a condition in which the outflow of urine from the kidney is obstructed, resulting in fluid-filled enlargement. The condition is usually detected by ultrasound, as early as the first trimester of pregnancy.
Antenatal Hydronephrosis can be mild, moderate, or severe and it requires monitoring before birth and during infancy and childhood. Occasionally, the kidney appears enlarged (dilated) during antenatal ultrasound yet functions normally after birth.
Prenatal (before birth) hydronephrosis (fluid-filled enlargement of the kidney) can be detected by ultrasound studies performed as early as the first trimester of pregnancy.
What happens before birth?
In most cases a routine normal delivery can be performed. Rarely, in a fetus with severe obstruction and insufficient amniotic fluid, early delivery or in utero intervention may be indicated.
What happens after the baby is born?
Good decisions are based on good information. Often more than one test is required to obtain the pertinent information. All infants should have a renal ultrasound in the postnatal period. A voiding cystourethrogram (a bladder X-ray, required to rule out reflux and posterior urethral valves) is essential. Many infants will require a diuretic (lasix) renal scan to evaluate kidney function and drainage.
What are the possible causes of the hydronephrosis?
Reflux: vesicoureteral reflux occurs when the valve between the bladder and the ureter does not function properly. This anatomic abnormality allows urine to flow back up to the kidney. The presence of reflux can lead to infection and kidney damage. Treatment with small doses of antibiotics usually prevents infection and kidney damage. Most children will eventually outgrow vesicoureteral reflux. Surgery is reserved for patients with persistent reflux or recurrent infection.
Obstruction: A relative blockage of the urine flow may occur at the level kidney (ureteropelvic junction , at the level of the bladder (ureterovesical junction), or in the urethra (posterior urethral valve).
A ureterocele is a balloon-like obstruction located at the level of the bladder. Sequential renal scans are often required to determine which patients require surgery and which patients do not.
Multicystic Dysplastic Kidney: A nonfunctioning cystic kidney. The management of multicystic dysplastic kidneys is controversial. Some urologists recommend surgery, whereas others do not routinely remove the dysplastic kidney. Close follow up is important as there is a small risk of hypertension or tumor.
Nonobstructive, Nonrefluxing Hydronephrosis: The system looks abnormal but has no significant physiologic abnormality.
UPJ obstruction: blockage at the left ureteropelvic junction (where ureter joins to the kidney)
Posterior urethral valves: blockage at the outlet of the bladder Vesicoureteral reflux on the left: flow of urine back up ureter causing dilated ureter and kidney.