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5.2.2 Voiding cystourethrography (vcug)

Of patients with UPJ-stenosis or megaureter, 14% show a vesicorenal reflux (VRR) at the same time. Reflux should be verified or ruled out by conventional VCUG pre-operatively. Isotope VCUG (lower exposure to radiation) is used for follow-up.

5.2.3 Diuresis renography

Because of its low radiation exposure, Tc99m-MAG3 is the radionuclide of choice in diuresis renography. The examination is carried out after standardized hydration with a transurethral catheter in place. Renal arterial perfusion, intrarenal cortical transit and excretion of the tracer into the collecting system are measured. If excretion is impaired, it takes longer for half the maximum activity of the radio-isotope to reach the renal pelvis (T1/2) after application of furosemide. With rapid absorption of the tracer and prompt washing out effect on diuresis (T1/2 < 10 min), obstruction is unlikely. Impaired or deteriorating split renal function in newborns or young infants with upper tract dilatation may be the best indicator of significant obstruction.

5.2.4 Static renal scintigraphy

Renal scintigraphy with di-mercaptosuccinic acid (DMSA) is an ideal method for assessment of renal mor­phology, acute infectious changes, renal scars and functional impairment, for example in multicystic renal dysplasia and reflux nephropathy. This investigation should not usually be used within the first 2 months of life.

5.2.5 Intravenous urogram (ivu)

The IVU is an optional examination method and may be performed pre-operatively and in case of inconclusive findings on sonography. The indication for an IVU in the first year of life is problematical.

5.2.6 Whitaker's test

Whitaker's test is carried out as an optional antegrade pressure flow study if diagnosis of obstruction is obscure. The measurement involves continuous perfusion of the renal pelvis via a percutaneous puncture or, if necessary, nephrostomy. Shortcomings of Whitaker's test are the unphysiologically high perfusion rate, lack of normal ranges in children, dependence on the examiner and the invasiveness of the procedure.

Table 3: Follow-up of prenatally diagnosed dilatation of the upper urinary tract

1.-2.Dayoflife

Ultrasound

No dilatation

1

Dilatation

-+

3. -5. Day of life

repeated ultrasound

I

Bilateral

Unilateral

No dilatation

I

, ultrasound control

3. -5. Day of life VCUG (urethral valves?)

2. -3. Week VCUG (reflux)

r

4. -6. Week Scintigraphy IVP (optional)

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