[99mTc]Tc-DMSA scanning in children: well beyond urinary tract infections

Introduction: [^99mTc]Tc-DMSA is the radiopharmaceutical of choice to assess global and regional renal parenchymal function. It is extensively used to demonstrate the possible presence of renal scarring following urinary tract infections (UTI) and, in some countries especially, to show renal parenchymal involvement with inflammatory infiltrate during an episode of acute pyelonephritis. Its use in other conditions is generally more limited. The purpose of this educational exhibit is to show examples of our clinical practice with [^99mTc]Tc-DMSA in several other nephro-urological pathologies.

Methods: [^99mTc]Tc-DMSA injected activity was scaled according to body weight following the Administration of Radioactive Substances Advisory Committee (ARSAC) Notes for Guidance, the committee advising the British Government on the use of radioactive medicinal products. Imaging was performed 2-3 hours after tracer injection. A single-head gamma camera (Mediso Anyscan) was used if SPECT was not performed. The patient was placed in supine position on a custom-made table with an insertion area which is the exact same size of the gamma camera detector: this allowed the child to lie on the collimator itself, thus minimising the distance of the kidneys from the detector and significantly improving spatial resolution. 300-500Kcounts were acquired for the posterior view (or an acquisition time of 10 minutes), 200-350 Kcounts for the left/right posterior oblique views; a zoom between 1 and 2 was used, with a matrix of 256 x 256 pixels. A dual head gamma camera (Siemens Symbia T2) was used when SPECT was performed. SPECT images were acquired in selected cases (crossed fused renal ectopia, renal transplants, renal stones, etc); a low dose CT KUB was acquired in patients with complex renal calculi to identify the position and the density of the calculus in the pelvicalyceal system and possibly in the ureter / bladder: this allowed to decide if the calculus was amenable to treatment with percutaneous nephro-lithotomy (PCNL) – in the case of dense calculi in the renal pelvis or proximal calyces - or with extra-corporeal shock wave lithotripsy (ESWL) with less dense, small and more peripheral calculi. Distraction and immobilisation techniques were successfully utilised to keep the child still during the examination, with no need of sedation or anaesthesia in virtually every case.

Results: We present cases illustrating the use of [^99mTc]Tc-DMSA in the following clinical conditions: recurrent and atypical UTI (including in renal transplant recipients), acute pyelonephritis, ectopic kidneys, horseshoe kidneys, crossed fused renal ectopias of several types, duplex kidneys, multi-cystic dysplastic kidneys, complex renal calculi before and after intervention, renal vein thrombosis, renal laceration after trauma, renovascular hypertension before and after revascularisation procedures with interventional radiology techniques, severe unilateral pelvicalyceal dilatation (especially when nephrectomy is considered), bilateral Wilms’ tumours (to quantify the bulk of functioning renal tissue in the kidney where nephron-sparing surgery is considered).

Conclusions: [^99mTc]Tc-DMSA scanning offers valuable information on renal parenchymal function, relevant for the clinical management of multiple nephro-urological conditions. The indications for [^99mTc]Tc-DMSA scanning are much broader than the assessment of renal scarring following UTIs.