Different uptake of 123I-MIBG in the two main liver lobes: A persistant unsolved mistery

Purpose: After radiopharmaceutical injection, a heightened 123I-MIBG concentration is frequently observed in the left hepatic lobe compared to the right one, but the reason of this finding remains unknown. Our aim was to retrospectively analyze the different 123I-MIBG uptake pattern between the two hepatic lobes and correlate our results with some epidemiological/clinical features. Material and methods: Ninety-four 123I-MIBG scintigraphies from 71 patients were selected. Regions of interest were drawn in the right and left lobes using transverse tomographic sections and left to right activity ratios (L/R ratio) were calculated at 6 and 24 h after radiotracer administration. Results: Twenty-seven examinations were positive for hypermetabolic lesions while the remaining 67 were negative. In all cases mean early and delayed L/R ratios were greater than 1.00; average early L/R ratio was 1.37 and delayed L/R ratio 1.52. The delayed L/R ratio was significantly higher than the early one. There was no difference in the L/R ratios with regard to age, gender, primary disease and result of scintigraphy. Conclusions: 123I-MIBG uptake was higher in left hepatic lobe compared to right and this ratio did not correlate with any epidemiological or clinical feature. The reason of this metabolic is not yet explained and some biomolecular hypotheses could be tested in 3 D dynamic in vitro models.