2.5 Clinical Features

The Society of Fetal Ultrasound (SFU) grading of hydronephrosis

•The old system classify hydronephrosis in infants and children into three grades:

–Mild

–Moderate

–Severe

•Obstructed hydronephrosis is also classified according to the level of obstruction:

–Infravesical obstruction:

•Posterior urethral valves

•Severe meatal stenosis and phimosis

•Severe urethral stricture

–Supravesical obstruction:

•Ureteropelvic junction obstruction

•Primary megaureter

•Uretrovesical obstruction

2.5Clinical Features

•The majority of hydronephrosis cases are now diagnosed antenattaly as a result of the wide-

spread and routine use of antenatal ultrasound.

•Most cases of hydronephrosis in infants are incidentally detected by routine screening ultrasounds.

•Hydronephrosis diagnosed prenatally:

–50% are transient and resolve spontaneously.

–15 % have hydronephrosis that persists but is not associated with urinary tract obstruction (non-refluxing, non-obstructive hydronephrosis). For these children, regression of the hydronephrosis occurs spontaneously, usually by age 3.

–35 % have a definite pathological cause for hydronephrosis. These include:

•Vesicoureteral reflux (9 %)

•Megaureter (4 %)

•Multicystic dysplastic kidney (2 %)

•Ureterocele (2 %)

•Posterior urethral valves (1 %)

•Hydronephrosis may be asymptomatic discovered on ultrasound ordered for some other reason.

•Another presentation of hydronephrosis is urinary tract infection.

•Acute hydronephrosis secondary to a stone will cause severe flak pain.

•Chronic hydronephrosis is usually asymptomatic or cause dull aching pain.

•Other clinical presentations of hydronephrosis include:

–Nausea and vomiting

–Urinary tract infection with abdominal pain, fever, dysuria, nausea and vomiting.

–Hydronephrosis secondary to obstruction at the bladder neck or urethra will lead to distension of the urinary bladder. This can cause lower abdominal pain and a palpable mass.

–The enlarged kidney may be palpable.

Hydronephrosis Diagnosed Prenatally

•Fifty percent are transient and resolve spontaneously.

•Fifteen percent have hydronephrosis that persists but is not associated with urinary tract obstruction (non-refluxing, non-obstructive hydronephrosis).

•Thirty five percent have a definite pathological cause for hydronephrosis. These include:

–Pelvi-ureteric junction obstruction (11 %)

–Vesicoureteral reflux (9 %)

–Megaureter (4 %)

–Multicystic dysplastic kidney (2 %)

–Ureterocele (2 %)

–Posterior urethral valves (1 %)

2.6Investigations and Diagnosis

•Complete blood count and differential

•Serum electrolytes

•Blood urea and creatinine

•Urine analysis and culture

•Abdominal x-ray (Figs. 2.43 and 2.44):

–This may show a soft tissue density on the left or right lumbar regions representing the enlarged kidney.

–Urolithiasis may cause hydronephrosis and radiopaque stones may be seen on plain abdominal x-rays.

•Abdominal and pelvic ultrasound (Figs. 2.45, 2.46, and 2.47):

–This is important in the detection of hydronephrosis and whether it is unilateral or bilateral.

–Ultrasound is also valuable in defining the degree of hydronephrosis.

–The size of the renal pelvis as measured by ultrasound is an estimate of the degree of hydronephrosis in those with obstructive hydronephrosis.

–It is also important to evaluate the ureter as dilatation of the ureter is seen in those with vesicoureteral reflux (VUR) or

obstructive uropathy distal to the ureteropelvic junction.

–An isolated hydronephrosis without dilatation of the ureter is suggestive of pelviureteric junction obstruction.

–The ultrasound is also valuable in evaluating the renal parenchymal thickness. Sever hydronephrosis will lead thinning of the renal cortex thickness.

–Ultrasonographic findings of posterior urethral valves are:

•Bilateral hydrouretero-nephrosis

•Dilated, thick walled bladder that fails to empty

•Dilated posterior urethra

•Intravenous urogram (IVU) (Figs. 2.48 and 2.49):

–Intravenous urography is a useful investigation to outline the anatomy of the renal system and locate the site of obstruction.

–This is rarely used nowadays as there are other more valuable and less invasive investigations.

–Add to this, the radiation exposure in children.

•A micturating cystourethrogram (MCU) (Figs. 2.50, 2.51, and 2.52):

–This is performed in patients with unilateral or bilateral hydronephrosis to exclude the possibility of vesicoureteral reflux or anatomical abnormalities such as posterior urethral valves.

–Vesicoureteral reflux is present in 8–38 % of patients with unilateral or bilateral antenatal hydronephrosis, as compared to <1 % in the general population.

–MCU is indicated in the following conditions:

•Infants with moderate to severe hydronephrosis (SFU grade 3–4, or renal APD >10 mm)

•Dilated ureter(s)

•Bladder or urethral abnormalities

•Patients with history of milder grades of antenatal hydronephrosis who show worsening hydronephrosis, progressive parenchymal thinning or occurrence of UTI.

Fig. 2.46 Abdominal ultrasound showing a right hydronephrotic kidney

•Diuretic renography (Fig. 2.53):

–Pelviureteric junction obstruction should be considered in infants with hydronephrosis, where dilating VUR is excluded.

–The likelihood of detecting obstruction is considerably higher in patients with SFU grade 4 or renal APD exceeding 20–30 mm.

–The possibility of vesicoureteric junction obstruction or megaureter is considered in patients with hydronephrosis and dilated ureter where MCU is normal.

–Patients with VUR and worsening hydronephrosis also require evaluation for pelvi-

Fig. 2.52 A micturating cystourethrogram showing right vesicoureteral reflux. Note also the dilated posterior urethra diagnostic of posterior urethral valve. Note also the small bladder diverticulae

ureteric junction obstruction, since the two may coexist in 7–18 % of patients.

–Diuretic renography allows differentiation between obstructive and non-obstructive hydronephrosis and estimating relative renal function.

–Radiopharmaceuticals such as 99mtechnetium mercaptoacetyltriglycine (MAG3) or ethylenedicysteine (EC) are preferred,

since they show greater renal extraction and higher kidney to background ratio compared to diethylenetriaminepentaacetic acid (DTPA).

•Renal urography includes the following two phases:

–First, radioisotope is injected intravenously and renal parenchymal (cortical) uptake is measured during the first 2–3 min. The rela-

tive contribution of each kidney to overall renal function (called the split renal function) is assessed quantitatively and is useful as a baseline study.

–Second, at peak renal uptake, intravenous furosemide is administered and the excretion of isotope from the kidney is measured, referred to as the washout curve. This phase indicates the extent of obstruction, if present.

–The washout curve:

•In a healthy kidney, furosemide administration results in a prompt washout.

•In a dilated system, if washout occurs rapidly after diuretic administration (<15 min), the system is not obstructed.

•If washout is delayed beyond 20 min, the pattern is consistent with obstructive uropathy.

•However, a delayed washout must be interpreted with caution. If washout is from 15 to 20 min, the study is indeterminate.

–The split renal function:

•Split renal function results are the most useful criteria to evaluate a decrease in renal function.

•In patients with unilateral hydronephrosis, if the normal nonhydronephrotic kidney and hydronephrotic kidney both have equal function, conservative management without surgery is a safe option.

•A significant decrease in renal function of one kidney is defined as 35 % or less differential renal function.

•A decrease in differential renal function was associated with severe antenatal hydronephrosis (i.e., renal pelvic diameter >10 mm at 20–24 week gestation and >16 mm at 33 week gestation).

–A normal renogram curve is characterized by:

•An early peak (2–5 min), rapidly descending phase and almost complete renal emptying by 20 min.

frusemide and micturition excludes significant obstruction.

•An obstructive pattern is defined by an ascending or plateau phase over 20 min that fails to empty following diuretic administration and on post-micturition views.

•Estimated differential renal function values between 45 % and 55 % are considered normal.

•An initial differential function below 35–40 % in the kidney with obstructed drainage signifies impaired renal function.

•Other features that suggest obstruction include ipsilateral supranormal differential renal function (55 %) and prolonged time to clear 50 % of the radionuclide (t1/2 >20 min).

•Abdominal CT-scan (Figs. 2.54 and 2.55)

–Abdominal CT-scan is valuable in outlining the extent of hydronephrosis and site of obstruction.

–It is also useful in measuring the renal parenchyma thickness.

•Magnetic resonance urography (MRU) (Figs. 2.56, 2.57, 2.58, and 2.59):

–MRU in children is becoming more commonly used in the diagnosis and management of congenital uropathies such as PUJ obstruction.

–MRU is especially useful in the management of obstructed kidneys that have rotation or ascent anomalies, or are solitary.

–MRU can more clearly define the anatomy and delineate the proper surgical approach.

–The disadvantage of MRU is that the study often requires general anesthesia or heavy conscious sedation in children.

–Furthermore, the contrast agent can only be used if renal function is normal because of reports of irreversible renal fibrosis in patients with renal insufficiency.

•Antegrade or retrograde pyelography is usu-