Female 34 weeks pregnant with left lower quadrant pain

(A) Transabdominal longitudinal view of the left kidney shows moderate hydronephrosis. Of note there was no hydronephrosis of the right kidney (not shown). Physiologic hydronephrosis of pregnancy is typically greater in the right kidney than the left kidney.
(B) The left ureter was dilated to the level of a 1 cm stone seen in gray scale and in color Doppler. Color in this case is showing a "twinkle" artifact due to the irregular surface of the stone.