2.7 Treatment

Figs. 2.54 and 2.55 Abdominal CT-scan showing hydronephrosis secondary to PUJ obstruction. Note the difference in the renal parenchyma thickness between the

two patients. I the second picture, there is hardly any renal tissue remaining

2.7Treatment

•The aim of treatment is to remove the obstructive cause and allow free drainage of the urine.

•The specific treatment of patients with hydronephrosis depends on the etiology and site of obstruction.

•The presence of infection should be treated aggressively as infection with hydronephrosis may progress rapidly to sepsis.

•The presence of bilateral hydronephrosis or hydronephrosis in a solitary kidney calls for urgent evaluation and management.

• A nephrostomy tube is a very valuable procedure to relieve acute hydronephrosis (Figs. 2.60, 2.61, 2.62, and 2.63).

•The use of ureteral stent can bypass an obstruction and temporarily relieve the pressure on the affected kidney.

•Lower urinary tract obstruction can be relieved by insertion of a urinary catheter or a suprapubic catheter.

•Fetal surgery:

–Fetal surgery is indicated in those with antenatal severe hydronephrosis in an attempt to preserve renal function and improve the clinical outcome.

–It is however not readily available and require expertise.

•Indication of surgical interventions in those with PUJ obstruction:

–Conservative management is appropriate for infants with an obstructive pattern on diuretic renography and differential function exceeding 40 %.

–While most experts suggest that pyeloplasty be considered in patients showing obstructed drainage and differential function below 40 %, others propose surgery at differential function below 35 %, or an obstructed renogram with prolonged t1/2 >20 min.

–In those with PUJ, a reduction of differential renal function by more than 5–10 % correlates with declining renal function, and the need for pyeloplasty.

–The presence of symptoms including pain, palpable renal mass or recurrent febrile UTI.

–The presence of large anteroposterior

diameter of renal pelvis exceeding 20–30 mm predicts the need for surgery in 50–55 % patients.

–Surgery allows preservation of renal function in the majority of patients.

–Predictors of unsatisfactory outcome include baseline renal differential function <30 % and anteroposterior diameter of renal pelvis >50 mm with dilated calyces.

•Antibiotic Prophylaxis

–While there is increased risk of UTI, there is lack of evidence that antibiotic prophylaxis

in patients with mild VUR confers clinical benefit.

–Multiple studies and a systematic review suggest that the severity of antenatal hydronephrosis does not correlate with the grade of reflux, and that patients with VUR may have normal postnatal ultrasound.

–Infants with postnatally confirmed moderate or severe hydronephrosis (SFU 3–4; renal APD >10 mm) or dilated ureter receive antibiotic prophylaxis while awaiting evaluation.

•There are those who recommend that all patients detected to have VUR receive antibiotic prophylaxis through the first year of life.

•Antibiotics that are preferred include cephalexin (10 mg/kg/day) during the first 3 months of life, and cotrimoxazole (1–2 mg/kg/day) or nitrofurantoin (1 mg/kg/day) later.

•Patients with moderate or severe hydronephrosis and/or dilated ureter should receive antibiotic prophylaxis while awaiting investigations.

•Since the risk of UTI is low with mild hydronephrosis, antibiotic prophylaxis is not necessary in these infants.

2.8Antenatal Hydronephrosis

•The widespread use of antenatal ultrasound has resulted in an increase in the early detection of antenatal hydronephrosis.

•Fetal hydronephrosis (dilatation of the renal pelvis with or without dilation of the renal calyces) is a common, readily diagnosed finding on antenatal ultrasound examination and can be detected as early as the 12th–14th week of gestation.

•Although antenatal hydronephrosis is most often transient or clinically insignificant, urinary tract obstruction or vesicoureteral reflux (VUR) are important causes that should be diagnosed soon after birth because they may result in renal impairment or cause further renal damage.

•The risk of significant renal and urinary tract abnormality in those with hydronephrosis increases with:

–The severity of hydronephrosis

–Persistence of hydronephrosis into the third trimester

–Bilateral involvement

–The presence of oligohydramnios

•Once fetal hydronephrosis is detected, the following parameters need to be evaluated using ultrasonography:

–Severity of hydronephrosis

–Whether hydronephrosis is unilateral or bilateral

–Dilatation of the ureter

•The risk of postnatal renal pathological changes correlates with the degree of antenatal hydronephrosis as follows:

–The risk for those with mild hydronephrosis is 12 %

–The risk for those with moderate hydronephrosis is 45 %

–The risk for those with severe hydronephrosis is 88 %

•The severity of antenatal hydronephrosis correlates positively with:

–Persistent postnatal hydronephrosis

–The need for surgical intervention

–The risk of UTI

•Grading the severity of antenatal hydronephrosis is important as this enables identification of infants that require close follow-up.

•About 88 % of mild antenatal hydronephrosis resolve in utero or in the neonatal period.

•It has been estimated that one in three neonates with moderate to severe hydronephrosis persisting in the third trimester required postnatal surgery.

•Hence, an ultrasound in the third trimester is valuable for identifying fetuses that require postnatal evaluation, follow up and possibly surgery.

•A systematic review concluded that:

–98 % of patients with SFU grade 1–2 or antero-posterior diameter (APD) of the renal pelvis <12 mm resolved.

–51 % of patients with APD >12 mm or SFU 3–4 resolved.

•All newborns with history of antenatal hydronephrosis should have postnatal ultrasound examination within the first week of life.

•Ultrasonography should be performed early, within 24–48 h of birth for neonates with:

–Suspected posterior urethral valves

–Oligohydramnios

–Severe bilateral hydronephrosis

–Severe hydronephrosis in a solitary kidney

Pathological Causes of Antenatally

Diagnosed Hydronephrosis

•Isolated Unilateral hydronephrosis

–PUJ

•Unilateral hydronephrosis with hydroureter

–Uretro-esical junction obstruction

–Uretrocele

–Vesicoueteric reflux

–Posterior urethral valve

•Isolated bilateral hydronephrosis

–Bilateral PUJ

•Bilateral hydronephrosis with hydroureter

–Bilateral uretro-vesical obstruction

–Bilateral vesicoureteric reflux

–Posterior urethral valve

–Bilateral uretrocele

–Urethral stricture

•In all other cases, the ultrasound should be performed preferably within 3–7 days, or before hospital discharge.

•A single ultrasound in the first few days of life might not detect all abnormalities of the kidneys or urinary tract, due to low urine flow secondary to dehydration and low glomerular filtration rate. An ultrasound at 6 weeks is more sensitive and specific for obstruction, than that in the first week of life.

•Postnatal radiologic studies:

–Postnatal radiologic evaluation of a newborn with antenatal hydronephrosis begins with an ultrasonography examination.

–The timing of ultrasonography and the need for other studies depend on the severity of postnatal hydronephrosis and whether

there is bilateral involvement or an affected solitary kidney.

–The timing of the study depends on the severity of the antenatal hydronephrosis.

•In general, examination should be avoided in the first 2 days after birth because hydronephrosis may not be detected because of extracellular fluid shifts that underestimate the degree of hydronephrosis.

•However, infants with bilateral hydronephrosis and those with a severe hydronephrotic solitary kidney require urgent evaluation on the first or second postnatal day because of the increased likelihood of significant disease and a possible need for early surgical intervention.

•For those with unilateral hydronephrosis without antenatal bladder pathology,

performing postnatal sonography 1–4 weeks after birth is recommended.

–A voiding cystourethrography (VCUG) is performed to detect VUR and, in boys, to evaluate the posterior urethra.

Postnatal Hydronephrosisultrasound

Evaluation

•The severity of hydronephrosis postnatally is determined by a renal ultrasound performed after 48 h of life in a full term infant and is based on anterior posterior pelvic diameter as follows:

–<7 mm should be considered normal

–7–8 mm: Mild hydronephrosis

–9–15 mm: Moderate hydronephrosis

–>15 mm: Severe hydronephrosis. These infants are at the greatest risk for significant renal disease, which requires surgical correction.

–Diuretic renography:

•This is used to diagnose urinary tract obstruction in infants with persistent hydronephrosis.

•It is usually ordered after a VCUG has demonstrated no vesicoureteral reflux.

•It measures the drainage time from the renal pelvis and assesses total and individual kidney function.

•The preferred radioisotope is technetium Tc 99m-mercaptoacetyltriglycine (Tc99m MAG3), which is taken up by the renal cortex, filtered across the glomerular basement membrane to the renal tubules, and excreted into the renal pelvis and urinary tract.

•The management of infants with antenatal hydronephrosis depends on:

– Confirmation of persistent postnatal hydronephrosis

– The severity of hydronephrosis: Fetuses with a renal pelvic diameter greater than 15 mm during the third trimester are at the greatest risk for significant renal disease

– Whether hydronephrosis is bilateral or unilateral

– Whether hydronephrosis is in a solitary kidney or not

•Bilateral hydronephrosis:

– Infants with severe bilateral antenatal hydronephrosis and/or bladder distension are at increased likelihood of having significant disease.

– These infants and those with a severe hydronephrotic solitary kidney should be evaluated initially by ultrasonography on the first postnatal day.

– Bilateral hydronephrosis suggests an obstructive process at the level of or distal to the bladder, such as uretrovesical obstruction, ureterocele or posterior urethral valves (PUV) in a male infant, which can be associated with impaired renal function and ongoing renal injury.

– If postnatal ultrasonography demonstrates persistent hydronephrosis, voiding cystourethrography (VCUG) should be performed. In male infants, the posterior urethra should be fully evaluated to detect possible PUVs.