Filling phase images are normal. During the voiding phase, left sided vesicoureteral reflux is seen to the level of the left kidney. There is blunting of several renal calyces (for example in the upper pole), compatible with grade 4 reflux.

The patient next underwent renal ultrasound imaging:

Grayscale (top), color Doppler (middle), and power Doppler (bottom) images of the right kidney are normal. Images of the left kidney demonstrate mild pelviectasis as well as thickening of the renal pelvis itself (arrowhead). There is questionable decreased blood flow to the left upper pole on the color Doppler image (asterisk), and this area appears to  be incompletely included in the power Doppler image.

Finally this patient underwent a Tc99m DMSA study:

This patient was diagnosed with pyelonephritis associated with vesicoureteral reflux. DMSA images demonstrate decreased cortical radiotracer uptake in the upper pole and anterior interpolar region of the left kidney. Cortical scarring (due to prior pyelonephritis) is also in the differential, though in this patient a followup study demonstrated resolution of the radiotracer defect. Cortical scarring is usually associated with a greater degree of volume loss than pyelonephritis.

Renal cortical imaging with technetium-99m dimercaptosuccinic acid (DMSA) is more sensitive for diagnosis of acute pyelonephritis compared to Doppler ultrasound and is considered the gold standard, though the latter offers the benefit of no ionizing radiation. Majd M, et al. Radiology 2001;218:101-8. Bykov S, et al. Clin Nucl Med 2003;28:198-203. Imaging with a pinhole collimator has been shown to be equivalent to SPECT imaging. Majd M, et al. J Nucl Med 1996;37:1731-4. Followup imaging in 6 months after the acute episode is recommended to identify scarring (non-resolution of cortical defects), although some defects may resolve even later. Agras K, et al. Pediatr Radiol 2007;37:153-8.