Acute pyelnephritis with a tiny calculus

This was a 45-years old lady who presented with fever and renal tenderness. Her urine showed pus cells.
The CT scan showed a calculus in the upper pole of the right kidney without obstruction (Figs. 1-3 - red arrow). More importantly, the right kidney showed heterogeneous enhancement with wedge-shaped areas of altered enhancement - this pattern is highly suggestive of multifocal acute bacterial nephritis / acute pyelonephritis.