Ureterolithiasis and hydronephrosis in pregnancy on ultrasound and noncontrast CT

22-year-old patient, 8 weeks pregnant, with E. coli urosepsis and left flank pain. Longitudinal ultrasound images of the left kidney (A, B) show moderate hydronephrosis. Transverse color Doppler image of the bladder (C) shows a strong right ureteral jet with a weaker left jet. No stone could be identified by ultrasound. Given persistent symptoms, a low-dose noncontrast CT was performed. Axial image at the level of the kidneys (D) shows left hydronephrosis. Axial image at the level of the bladder (E) shows a stone at the left ureterovesical junction. The patient was treated with percutaneous stent placement (not shown).