Mild left hydronephrosis due to an obstructing small left upper third ureteric stone measuring 6 mm.
Water attenuation fluid (10 - 15 HU) confined in the left perirenal space, more evident around its lower pole, is compatible with a rupture of a calyceal fornix in the kidney and urine extravasation / leak.
There is an additional lower calyceal stone measuring 12 mm.