The aim of the present study was to estimate the sensitivity of indirect radionuclide cystography (IRC) performed with technetium-99m mercaptoacetyltriglycine (MAG3), in comparison with the micturition cystourethrography (MCUG) and direct radionuclide cystography (DRC), for the diagnosis of vesicoureteric reflux. Two groups of patients were selected: group I comprised 40 children who underwent IRC during the acute phase of urinary tract infection and an MCUG 6 weeks later; group II comprised 42 (other) children with known reflux, who underwent IRC and DRC during follow-up. Taking as the reference the total number of refluxing kidneys detected by means of any cystographic technique, 99mTc-MAG3 ICR missed two-thirds of the refluxing kidneys. Most of the small refluxes were missed, but so too were 50% of the major refluxes. Taking as the reference 99mTc dimercaptosuccinic acid (DMSA) scintigraphy, MCUG detected 91% of the patients with DM-SA abnormalities on at least one kidney, DRC detected 95%, and IRC detected 46% and 43% respectively, in groups I and II. The use of 99mTc-MAG3 IRC as the sole technique for the detection of vesicoureteric reflux gives rise to an unacceptable number of false-negative results.

Background: Chronic kidney failure is frequently seen in middle-aged and elderly cats.

99Tcm-DMSA planar images of 49 randomly selected patients (10 adults, 39 children) were sent to 15 physicians at various centres in Belgium. They were asked to calculate, using their own routine program, the relative uptake (expressed as a percentage) of each kidney. The data were sent on disks formatted so that they could be read by all participants, using their own computer systems. For each scan, the inter-observer variability was expressed using the maximum difference and the standard deviation of left renal uptake. Left renal uptake measured by the 15 observers in the 49 patients was 29.0-72.0% (mean +/- s = 49.8 +/- 6.4%). The maximum differences in left renal uptake ranged between 1.7% and 12.0% (4.5 +/- 2.6%); however, the maximum difference did not exceed 8% in about 90% of the patients. The standard deviations of the individual left renal uptake were between 0.6 and 3.9 (1.3 +/- 0.8). The standard deviations were significantly higher in adults (mean standard deviation = 2.05) than in children (mean standard deviation = 1.12) (P < 0.001); this was probably related to the high background observed in three adults with severe renal impairment. Indeed there was a significant correlation (P < 0.001) between the standard deviation and both the signal-to-noise ratio and the degree of asymmetry between the right and left kidneys. The differences between right and left kidney uptake were systematically lower for some observers, suggesting an influence of the calculation programs.

Estimation of the glomerular filtration rate (GFR) is a useful tool in the evaluation of kidney function in feline medicine. GFR can be determined by measuring the rate of tracer disappearance from the blood, and although these measurements are generally performed by multi-sampling techniques, simplified methods are more convenient in clinical practice. The optimal times for a simplified sampling strategy with two blood samples (2BS) for GFR measurement in cats using plasma (51)chromium ethylene diamine tetra-acetic acid ((51)Cr-EDTA) clearance were investigated. After intravenous administration of (51)Cr-EDTA, seven blood samples were obtained in 46 cats (19 euthyroid and 27 hyperthyroid cats, none with previously diagnosed chronic kidney disease (CKD)). The plasma clearance was then calculated from the seven point blood kinetics (7BS) and used for comparison to define the optimal sampling strategy by correlating different pairs of time points to the reference method. Mean GFR estimation for the reference method was 3.7+/-2.5 ml/min/kg (mean+/-standard deviation (SD)). Several pairs of sampling times were highly correlated with this reference method (r(2) > or = 0.980), with the best results when the first sample was taken 30 min after tracer injection and the second sample between 198 and 222 min after injection; or with the first sample at 36 min and the second at 234 or 240 min (r(2) for both combinations=0.984). Because of the similarity of GFR values obtained with the 2BS method in comparison to the values obtained with the 7BS reference method, the simplified method may offer an alternative for GFR estimation. Although a wide range of GFR values was found in the included group of cats, the applicability should be confirmed in cats suspected of renal disease and with confirmed CKD. Furthermore, although no indications of age-related effect were found in this study, a possible influence of age should be included in future studies.

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