The urine dipstick was positive for leukocytes, and the patient was treated for pyelonephritis with an uneventful recovery. The study shows the value of diffusion-weighted imaging in identifying foci of inflammation that may be more difficult to identify on other sequences. Physiologic hydronephrosis is a common finding, with smooth tapering of the dilated ureter between the gravid uterus and the psoas muscle being the key sign.