To investigate the prenatal ultrasound image characteristics of fetal horseshoe kidney.

From January 2010 to December 2013, prenatal ultrasound examinations were performed on 12 021 cases at the Chongqing Population and Family Planning Science and Technology Research Institute through fetal multi-slice scanning and dynamic observation. Among these cases, 15 cases were diagnosed with horseshoe kidney (0.12%, 15/12 121). The postpartum ultrasound or MRI reviews, autopsy and clinical follow-up results of these 15 horseshoe kidney cases were compared with their fetal prenatal sonographic characteristics.

Among the 15 horseshoe kidney cases, six horseshoe kidney cases were initially detected through fetal scanning. After an interval of 4-6 weeks, the remaining nine horseshoe kidney cases were detected by supplemental review. In the 15 horseshoe kidney cases, fetal kidney sagittal scans revealed that the renal locations were lower than those of normal fetal kidneys in 10 cases, and the lower border of the kidneys were fuzzy. In these 15 cases, cross-section continuous scans revealed a "horseshoe" shape characteristic of fusion kidneys in front of the spine. Coronal section scans revealed fusion kidneys at the front of the spine. Among the 15 horseshoe kidney cases, 11 cases were born after fetal ultrasound examination; in which seven cases were male (one case was associated with cryptorchidism) and four cases were female. Postpartum ultrasound (six cases) and MRI review (five cases) confirmed the horseshoe kidney, and no renal abnormalities were found. Furthermore, one horseshoe kidney case had trisomy 18 syndrome. Pregnancy was terminated for the three remaining cases associated with extra-renal malformations detected by ultrasound examination. One case had a ventricular septal defect and chromosome examination revealed trisomy 21 syndrome. Two cases had renal abnormalities (open spina bifida and foot varus diagnosed by ultrasound and horizontal liver confirmed by autopsy in one case, and genital deformity in the other case), and chromosome examination did not reveal any abnormalities.

Prenatal ultrasound multi-slice scanning and dynamic observation combined with chromosome examination and the early detection of fetal horseshoe kidney and its merger deformity can reduce multiple birth defects of the fetus.