Mercapto-acetyltriglycine (MAG 3) renography and indirect radionuclide cystography in posterior urethral valves.
OBJECTIVE
To assess dynamic isotope renography with 99mTc-labelled mercapto-acetyltriglycine (MAG 3) in conjunction with indirect radionucleide cystography (IRC) in the follow-up of boys with posterior urethral valves.


METHODS
Fifty-one boys (95 renal units; mean age = 89 months, range 65-118) with previously treated posterior urethral vales underwent MAG 3 renography followed by IRC. Glomerular filtration rate (GFR) was estimated from the plasma clearance of 51Cr-ethylenediamine tetra-acetic acid following single intravenous injection. Renographic parameters noted were renal function based on the quality of renal visualization and background activity as well as renal drainage and the appearance of isotope in ureter and bladder. Following the dynamic 20 min MAG 3 renogram the child was allowed to leave the department and to return when he wished to void. IRC was then performed. Diuretics were not administered.


RESULTS
Initial drainage from 30 kidneys was normal, in 36 drainage was delayed and in 25 drainage did not occur during the renogram phase. In four kidneys function was so poor as to preclude assessment. After the IRC, drainage was noted in 17 of 25 units which had not drained during the renogram, six units did not drain and in two drainage was equivocal due to the presence of vesico-ureteric reflux. The quality of the scan was good or very good in 42 patients (mean GFR = 92 ml/min/1.73 m2 SA) and moderate or poor in nine patients (median GFR = 20 ml/min/1.73 m2 SA) (P < 0.001). A residual urine was noted following micturition in 35 boys; this was due to incomplete bladder emptying in 14 and to immediate secondary refilling from dilated upper tracts in the remainder.


CONCLUSIONS
IRC in conjunction with traditional dynamic renography using MAG 3 provides valuable additional information about upper tract drainage. The necessity for diuresis renography is obviated in the majority of patients. IRC also allows an excellent non-invasive, physiological assessment of both upper and lower urinary tract function which is superior to conventional single examination techniques. We recommend the use of MAG 3 with IRC in the routine follow-up of boys with posterior urethral valves.
Dinneen
M D
MD
Department of Urology, Hospitals for Sick Children, London, UK.
Duffy
P G
PG
Lythgoe
M F
MF
Ransley
P G
PG
Gordon
I
I
D002648:Child; D002675:Child, Preschool; D005919:Glomerular Filtration Rate; D006801:Humans; D007678:Kidney Glomerulus / Q000503:physiopathology; D008297:Male; D011866:Radioisotope Renography; D017263:Technetium Tc 99m Mertiatide; D014521:Urethra / Q000002:abnormalities* / Q000000981:diagnostic imaging; D014524:Urethral Obstruction / Q000000981:diagnostic imaging / Q000209:etiology; D014554:Urination
D017263:Technetium Tc 99m Mertiatide