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Objective: Since the approval of mercaptoacetyltriglycine (MAG3) for routine clinical use, reports have appeared about hepatobiliary excretion deleteriously affecting available diagnostic and quantitative information. The purpose of this study was to evaluate gallbladder (GB) uptake of MAG3 in the clinical setting and its effect on the evaluation of relative renal function and imaging.
Methods: Sixty patients with varying degrees of renal impairment were studied. Routine renal function imaging was followed with anterior and right lateral 3-min abdominal images. Factors such as photolytic degradation, reconstitution steps, ^sup 99m^99-Tc O^sub 4^ solution, age, and concentration are discussed. In addition, patient fasting state and radiochemical purity are evaluated. The GB uptake was determined as a percentage of the injected dose.
Results: The MAG3 quality control ranged from 90.9% to 99.0%. The GB uptake ranged from 0.0% (not visualized) to 0.71 %. The effective renal plasma flow ranged from 88 to 743 mUmin. There was no correlation between the QC and the percentage of GB uptake (r = 0.12). The majority of patients in the nonfasting state showed minimal or reduced GB uptake when compared with the majority of patients in the fasting state.
Conclusion: Our data suggest that GB uptake of MAG3 is minimal, with no adverse effects on the diagnostic and quantitative analysis of renal function.
Key Words: hepatobiliary; ^sup 99m^Tc-MAG3; excretion J Nucl Med Technol 2003; 31:18-20
The elimination of nuclear medicine imaging agents from the body occurs primarily by 2 major routes of excretion: gastrointestinal (hepatobiliary) and renal (glomerular filtration and tubular secretion). In the early 1990s, 99-Tc-mercaptoacetyltriglycine (MAG3), a renal tubular agent, was introduced to replace ^sup 131^I-o-iodohippurate (OIH). Since the approval of MAG3 for routine clinical use, conflicting reports about the amount of hepatobililiary excretion have appeared in the literature. Marked excretion would affect the diagnostic and quantitative information available in the investigation of relative renal function and quantitative analysis. The findings of hepatobiliary excretion, as seen in Figures 1 and 2, have been reported (1), and the majority of such reports have been associated with the utilization of the commercial kit formulation.
Because the plasma clearance of an agent reflects clearance by all elimination pathways, hepatocyte uptake and hepatobiliary excretion must be considered. If significant uptake occurs, the...