Quantitative renal [^99mTc]DMSA imaging predicts urinary [^99mTc]DMSA excretion in patients with chronic kidney disease

^99mTc-labelled Dimercaptosuccinic acid ([^99mTc]DMSA) is a radiopharmaceutical commonly used to evaluate renal perfusion, structure, and morphology. However, the renal handling of [^99mTc]DMSA in humans remains unclear. Studies in humans with renal tubular dysfunction and animal experiments suggest that renal uptake of [^99mTc]DMSA occurs by glomerular filtration and subsequent proximal tubule reabsorption. The main aim of this study was to examine renal handling of [^99mTc]DMSA and the pathophysiological implications of [^99mTc]DMSA-based imaging in patients with chronic kidney disease (CKD) compared to healthy controls (HC).

Urinary excretion of [^99mTc]DMSA was 1.5-fold higher and more variable in CKD patients compared to HC. While [^99mTc]DMSA plasma clearance was only 1.1-fold higher in HC, the [^99mTc]DMSA uptake in the kidneys was 2.6-fold higher in HC compared to CKD patients and correlated inversely with the 24-hour urine excretion of [^99mTc]DMSA independent of GFR.

Kidney [^99mTc]DMSA accumulation is consistent with tubular uptake following glomerular filtration. The relative DMSA uptake is lower in CKD patients, pointing to defective proximal tubular function in this patient group. Furthermore, the results suggest that [^99mTc]DMSA uptake could serve as a marker for tubule-interstitial function.