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Introduction
Clinical presentation
Clin. aproach to ivestig. and menag. of UTI
Cortical scintigraphy in urinary tract infection
Cystigraphy in urinary tract infection
Vesicourethral reflux (VUR)
The grading systems for vesicourethral eflux
Detection of vesicourethral reflux
Micturating cystourethrography (MCUG)
Radionucleotide cystography (RNC)
Direct radionuclide cystography (DRC)
Indirect radionuclide cystography (IRC)
Dynamic renal scintigraphy in UTI
Practical problems in pediatric nucl.med.
Preparation
Dose schedule
Injection
Imobilisation/ sedation
Conclusion

4.2.2.1. DIRECT RADIONUCLIDE CYSTOGRAPHY (DRC)

DRC involves bladder catheterization, draining off the urine and instilling 99mTc perthechnetate (20MBq) in normal saline until the bladder is full, when spontaneous micturing occur [5]. Conway et al reported systemic absorption 99mTc pertechnetate across the urinary tract mucosa in 50% of refluxing patients and 20% of patients without reflux. It is theoretically possible to visualize renal excretion and make a false-positive diagnosis of reflux. Similar theoretical concern exist for diethylene triamine pentaacetic acid. Therefore, 99mTc sulfur colloid is widely used [2,9].
The entire procedure is carried out on the top of a gamma camera linked to a computer system.

The advantages are mainly the high sensitivity of technique in the detection of renal reflux and the possibility of combining this with pressure measurement so that a full urodynamic assessment of the bladder is made. The bladder is visualized during the filling as well as during the voiding and postvoid phase continuously. A urine specimen obtained by catheterization is available for culture. It is now widely accepted that direct redionuclide cystography is at least sensitive and probably more sensitive than contrast cysthography. Low radiation burden to the child compared with conventional MCUG, the dose being reduced by factor 20, must also be kept in mind [2,5]. The gonadal absorbed radiation dose is 0.01 to 0.02 mSv, which is 50 to 100 times less than with conventional MCUG [9].

The disadvantages are the need to catheterize the bladder, with the attendant small risk (0.2%) of catheter-induced infection, no anatomical details of the urethra is provided and the presence of catheter and rapid filling of the bladder do not reproduce normal filling and voiding dynamics [5]. The disadvantage is, like for the X-ray technique , the invasive character: no child will ) accept the procedure without a strong negative reaction [9].

The DRC is indicated in all girls under 3 years of age in whom renal reflux should be excluded, e.g. UTI or prenatal diagnosis of hydrourethei-onephro.sis and in all boys under 3 years of age in whom VUR has been established on MCUG and in whom follow up is required.

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