3.6 Diagnosis and Investigations

•Only renal pelvis visualized, dilated pelvis on ultrasonography, no caliectasis

–Grade 2:

•Moderately dilated renal pelvis and a few calyces

–Grade 3:

•Hydronephrosis with nearly all calyces seen, large renal pelvis without parenchymal thinning

–Grade 4:

•Severe dilatation of renal pelvis and calyces with accompanying parenchymal atrophy or thinning

•Approximately 20 % of antenatally diagnosed hydronephroses are not found on postnatal ultrasound.

•PUJ obstruction is known to be associated with other types of congenital abnormality. This is seen in almost 50 % of patients.

•PUJ obstruction is bilateral in about 10 % of patients (Figs. 3.16, 3.17 and 3.18).

•About 10 % of patients with PUJ obstruction have ipsilateral vesicoureteral reflux and to detect this, a voiding cystourethrogram should be part of the work-up of these patients.

•There are also reports of coexisting PUJ obstruction and uretero-vesical junction obstruction. In these cases, the uretero-vesical obstruction is usually mild and PUJ obstruction should be treated first.

•Duplication anomalies usually cause PUJ obstruction at the lower poles and the possibility of vesicoureteral reflux should be rolled out.

•Rarely, the PUJ may be so severe leading to massive dilation of the renal collecting system and these patients may present with a palpable flank mass. This however is a rare and unusual presentation of PUJ at present.

•PUJ obstruction is often associated with other congenital anomalies, including:

–Anorectal malformations

–Contralateral multicystic kidney

–Congenital heart disease

–VATER (vertebra, anus, trachea, esophageal, renal) syndrome

–Esophageal atresia

The SFU Grading System for

Hydronephrosis

•Grade 0:

–No hydronephrosis, intact central renal complex seen on ultrasonography

•Grade 1:

–Only renal pelvis visualized, dilated pelvis on ultrasonography, no caliectasis

•Grade 2:

–Moderately dilated renal pelvis and a few calyces

•Grade 3:

–Hydronephrosis with nearly all calyces seen, large renal pelvis without parenchymal thinning

•Grade 4:

–Severe dilatation of renal pelvis and calyces with accompanying parenchymal atrophy or thinning

3.6Diagnosis and Investigations

•Prenatal evaluation:

–Prenatal ultrasound is widely used to diagnose fetal abnormalities.

–Among these abnormalities is PUJ obstruction.

–Prenatal ultrasound evaluation should include the followings:

•Amniotic fluid volume to rule out oligohydramnios

•Bladder volume

•Kidney size

•Anteroposterior diameter of the renal pelvis

•Other associated abnormalities

–Functionally significant hydronephrosis can be determined when:

•The anteroposterior diameter of the renal pelvis is more than 10 mm.

•The ratio of the renal pelvis to the anteroposterior kidney size is more than 0.3.

•There is evidence of caliectasis after 24 weeks of gestation.

•Patients with PUJ obstruction diagnosed by prenatal ultrasound should have a postnatal ultrasound. The timing of ultrasound is variable and depends on the severity of the PUJ obstruction.

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

that will underestimate the degree of hydronephrosis.

•Therefore, in unilateral disease, ultrasonography should be performed at least after 48 h of life.

•These patients should also be placed on prophylactic antibiotics (amoxicillin 15 mg/kg) to prevent urinary tract infections.

•Other investigations include:

– Complete blood count

–Urine analysis and culture

–Serum electrolytes, BUN and creatinine

–Plain abdominal radiograph

–Abdominal ultrasound

–Abdominal CT-scan

–Abdominal MRI

–A nuclear renal scan can

–Intravenous urography

–Voiding cystourethrography

–Percutaneous nephrostography

–Cystoscopy and retrograde pyelography

–A Whitaker antegrade pressure-flow study

•Serum electrolytes, BUN and creatinine are important to measure renal function especially in those with bilateral disease.

•Urine analysis and culture are important to roll out associated urinary tract infection especially in asymptomatic patients.

•Abdominal radiograph (Fig. 3.19):

–A plain abdominal x-ray may show a soft tissue density secondary to a hydronephrotic kidney.

Fig. 3.19 Abdominal radiograph showing a soft tissue density on the left side in a child with severe left PUJ obstruction

–A plain abdominal x-ray may also show radiopaque stones complicating PUJ obstruction.

•Abdominal ultrasound (Figs. 3.20 and 3.21):

–Renal ultrasound will show a dilated renal pelvis with a collapsed non-dilated ureter.

–Renal ultrasound is also important to measure the size of the renal pelvis and it is useful for follow-p to monitor changes in the size of the renal pelvis.

–Ultrasound can also help determine the size of the kidney, the size of renal and the thickness of renal parenchyma.

–Ultrasound is also important to detect other associated urological abnormalities.

–Duplex Doppler ultrasonography can be used to assess intrarenal vasculature and determine the resistive index.

•Normal kidneys reliably demonstrate resistive indices less than 0.7, and obstructed kidneys show higher values.

•This is especially reliable in the preoperative diagnosis of aberrant-accessory blood vessels associated with PUJ obstruction.

–Renal ultrasound is a relatively cheap investigation, devoid of radiation and can easily be repeated.

•Intravenous urography (Figs. 3.22, 3.23 and 3.24):

–Historically, intravenous pyelography (IVU) was used to evaluate patients with possible PUJ obstruction.

–The administration of frusemide helps exclude a ‘baggy pelvis’.

–Currently, intravenous urography is replaced by other less invasive and more informative investigations.

–Intravenous urography has the risk of radiation exposure and contrast media including nephrotoxicity and anaphylactic reactions.

•The diagnosis of intermittent UPJ obstruction is confirmed if hydronephrosis is present when the child is symptomatic, and resolves when the child is well. A diuretic renal scan will document baseline renal function and may also provoke symptoms during the diuretic phase of the study, which confirms the diagnosis.

brane to the renal tubules, and excreted into the renal pelvis and urinary tract.

–MAG3 is another tracer that is mainly intravascular and secreted by proximal renal tubules, with a small fraction being filtered by the glomeruli.

–Another widely used tracer is technetium 99m diethylenetriamine penta-acetic acid

(99m Tc-DTPA), which, owing to the small size of molecule, diffuses within both intravascular and extravascular spaces, resulting in significant background activity.

–The diuretic renography measures the drainage time from the renal pelvis (referred to as washout) and assesses total and each individual kidney’s renal function.

Figs. 3.25, 3.26, and 3.27 Abdominal CT-scans showing hydronephrosis secondary to PUJ obstruction (Note the very severe obstruction in the middle picture with

almost complete renal atrophy where there is only a small rim of renal parenchyma remaining while in the lower one the renal parenchyma is still preserved)

–The washout measurement correlates with the degree of obstruction.

–The patency of the PUJ is determined by measuring the T1/2 (the time required for 50% of the isotope to be excreted) on the wash-out curve. Rapid drainage (low T1/2)

indicates no obstruction, while impaired drainage or slow or no washout (T1/2 >20 min) indicates obstruction.

–Another important measurements in diuretic renography is the estimate of differential renal function. This is considered

significant when it is less than 40 %. Diuretic (Furosemide) Renogram is performed to differentiate obstructive from nonobstructive hydronephrosis.

–Sometimes an unusually high differential renal function can be seen on the affected kidney. This is attributed to an increase in single-nephron filtration or nephron volume.

–Currently, a diuretic renal scan is important

to diagnose those with functionally significant PUJ obstruction. The Reno graphic criteria include:

• A flat or rising washout curve after diuretic with T 1/2 of greater than 20 min and differential function of less than 40.

•The differential function is important in determining the need for intervention, especially in asymptomatic patients, and in selecting the appropriate treatment (pyeloplasty vs nephrectomy).

•Poorly functioning kidneys (<10 %) are often best treated with nephrectomy.

–In general, a half-life greater than 20 min to clear the isotope from the kidney is considered indicative of obstruction, although

other urologists use split function, comparing the function of the two kidneys, as a means to identify patients for surgery.

–Renal isotope scan is also used to assess outcomes after surgical correction of PUJ obstruction.

•A voiding cystourethrography (VCUG) (Figs. 3.33 and 3.34):

–A voiding cystourethrography (VCUG) is part of the work up of these patients.

–This is to rule out vesicoureteral reflux.

–Vesicoureteral reflux (VUR) has been found in as many as 40% of children with PUJ obstruction but the reported incidence of VUR in association with PUJ obstruction is about 10%.

–The VUR is usually mild and usually resolve spontaneously.

•Retrograde/antegrade pyelography:

–Retrograde pyelography was used to assess the upper ureter and renal pelvis.

–Retrograde or antegrade pyelography requires general anesthesia.

–It is now mostly performed at the time of surgical correction of the PUJ obstruction to establish the exact site of obstruction.

–A percutaneous nephrograohy (Figs. 3.35, 3.36, 3.37 and 3.38):

Figs. 3.35, 3.36, 3.37, 3.38, and 3.39 Nephrostograms showing unilateral and bilateral PUJ obstructions. Percutaneous nephrostograms are useful especially in newborns with severe hydronephrosis (Note only they

confirm the diagnosis and severity of PUJ but they are useful for temporary drainage of the obstructed kidney to refive the pressure from the renal parenchyma)

•This can be diagnostic and also used to temporary drain the kidney to decompress the renal pelvis and relive the pressure on the renal parenchyma.

•This is valuable especially in newborns with severe obstruction. The ureter is small in these patients which makes it difficult to reconstruct the PUJ and a temporary nephrostomy will drain the obstructing kidney and buy time.

•Pressure flow studies:

–When the radiological investigations are equivocal, a Whitaker antegrade pressureflow study may be performed to further evaluate for PUJ obstruction.

–This is done as follows:

•A small-diameter nephrostomy tube is inserted percutaneously into the kidney.

•Dilute contrast medium is instilled, and the intrarenal collecting system is pressure-monitored.