ABSTRACTS PRESENTADOS AL 11th INTERNATIONAL SYMPOSIUM "RADIONUCLIDES IN NEPHRO-UROLOGY", REALIZADO EN MONTEREY, CALIFORNIA, 13-17 MAYO 2001.
27. TWO YEARS' EXPERIENCE WITH OUTPUT EFFICIENCY IN ASSESSING EQUIVOCAL OUTFLOW TRACT OBSTRUCTION.
P.S. Cosgriff, O. Morrish, D.T.L. Turner. Departments of Medical Physics & Urology, Pilgrim Hospital, Boston, UK
We
report our first 2 years experience with the output efficiency (OE)
parameter as a means of reducing equivocal results obtained from conventional
diuresis renography. Following injection of 80 MBq Tc99m MAG3, ninety
20-second frames are acquires with frusemide (0.5mg/kg) given at 15
minutes (F+15). Static pre-and post micturition views are obtained
at the completion of the dynamic study.
Initially,
100 consecutive adult renograms (from archive) were retrospectively
analyzed. A single software package was used to calculate both output
efficiency and relative renal function. Objective criteria used for
OE interpretation were as follows: no obstruction: >78%, obstruction:
< 70%, equivocal 70-78%. Using conventional subjective assessment,
15 frusemide responses were deemed equivocal, of which OE converted
8 to negative, 5 to positive, and 2 remained equivocal. The functional
contribution of these 15 kidneys ranged from 9-57% (mean=40%). In
addition, 1 positive result was converted to negative. The remainder
of the results (181/197 kidneys) were concordant. Seven of the 8 'equivocal-to-negative'
studies were adjudged true negative and 4 of the 5 'equivocal-to-positive'
studies were deemed true positive. No false results were obtained
when the OE and subjective assessment were concordant. From this initial
assessment we concluded that OE is a reliable parameter for assessing
the kidney's response to frusemide, allowing the equivocal rate for
F+15 renography to be reduced from about 15% to about 2%. At this
point, OE measurement was formally adopted into routine practice.
For the subsequent 31 (adult) F+15 renograms, concordancy (subjective vs objective assessment) was found in 5/5 positive studies and 22/23 negative studies. The 3 equivocals were resolved using OE. Follow-up for 20 of these patients is available, and outcome analysis will be presented. Early results tend to confirm our initial conclusions regarding the accuracy of OE.
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