Unusual diffuse [(131)I]MIBG accumulation in a kidney with renal artery stenosis.

Keywords: false-positive result; [131I ]MIBG scan; renal neuroblastomas, and has had only limited success in other tumour types [1,2]. In our patient, the topo-artery stenosis graphic appearance of the MIBG accumulation corresponded exactly to the entire left kidney, as defined by diffuse homogeneously decreased MAG3 perfusion and uptake. Horne et al. supposed this accumulation to Renal history imply an increased sympathetic innervation or activity in severe renal artery stenosis [3]. A 16-year-old woman was admitted for evaluation of A false-positive MIBG scan is very rare [1,4]. hypertension. A CAT-scan study showed an abnormal Misleading focal [131I ]MIBG accumulation in the area in the upper pole of the right kidney or right renal area has been reported in the presence of a suprarenal region. Technetium-99m mercaptoacetyltri-dilated renal pelvis [5,6 ] and acute pyelonephritis [7]. glycine (Tc-99m MAG3) renogram was then per-To our knowledge, only two false-positive results due formed. The right kidney showed no abnormalities, to unilateral renal artery stenosis have been reported but in the entire left kidney there was a diffuse decrease but in both the topographic location of [131I ]MIBG of radiotracer perfusion and uptake, which was consid-accumulation was focal and imprecise [2,3]. In con-ered highly suggestive of left renal artery stenosis trast, [131I ]MIBG was diffusely and homogeneously (Fig. 1). 131-Iodine metaiodobenzylguanidine concentrated throughout the left kidney of our ([131I ]MIBG scan was also performed because of clin-patient. ical and radiographic suspicion of a pheochromocy-[131I ]MIBG is largely (90%) excreted unchanged in toma in the right suprarenal region. The MIBG scan the urine over the 4 days after intravenous administra-revealed abnormal tracer accumulation homogen-tion. Free radioactive iodide is eliminated primarily in eously distributed in the whole left kidney at 48 and the urine. In our patient, the left kidney had diminished 96 h but no abnormalities in the right renal or supra-and delayed excretion (as shown in Fig. 1). renal area (Fig. 2). On the basis of Tc-99m MAG3 [131I ]MIBG scanning at 48 h post-injection allowed for and [131I ]MIBG findings, this patient underwent select-visualization of both the entire left kidney and the ive angiography which confirmed an 80% stenosis of bladder (images not shown); however, the kidney, but the lumen of the left renal artery. not the bladder, was clearly observed on the 96-h images (as shown in Fig. 2). We believe that delayed, physiological urinary excretion of either [131I ]MIBG or free radioiodide cannot …