Prenatal Detection of Fetal Cystinuria by Fetal Hyperechoic Colon in Ultrasonography: A Case Report

• Published in: PERINATOLOGY (구 대한주산의학회잡지) Vol. 33; no. 2; pp. 116 - 120
• Main Authors: Yoon Suk Choi, Yoon Young Jeong, Jin Young Bae, Ji Eun Jeong, Seong Yeon Hong, Hyun Jin Ko
• Format: Journal Article
• Language: Korean
• Published: 대한주산의학회 30.06.2022
• Subjects: Cystinuria; Echogenic bowel; Prenatal diagnosis; SLC3A1
• ISSN: 2508-4887

Cystinuria is an inherited disorder that causes urolithiasis owing to a defect in the reabsorption of cystine in the kidneys. A fetal hyperechoic colon revealed on ultrasound before 36 weeks of gestation may suggest cystinuria, and a high positive predictive rate of 89% has been reported. A 31-year-old female patient was referred to Daegu Catholic University Hospital at 30 weeks of gestation for a fetal echogenic bowel. The fetal colon had homogenously increased echogenicity as much as that of the fetal iliac bone, upon prenatal ultrasonography; otherwise, there was no evidence of fetal structural anomalies. The baby was born at 37 weeks and 3 days of gestation. Postnatal urinary amino acid analysis revealed 4,425 mol/g cystine (normal range, 212-668 μmol/g). Diagnostic exome- sequencing revealed a c.1976A>C mutation in the SLC3A1 gene. From the time of weaning, sodium intake or animal protein diet can be restricted; however, since it is not consumed during the newborn period, the progress was observed at the outpatient clinic without any other restrictions. The baby visited an outpatient clinic at 1 month of age with no urolithiasis. Since cystine urolithiasis generally appears in the first 2 decades, there is an advantage in receiving preventive treatment if diagnosed in advance using prenatal ultrasound findings. Therefore, if hyperechoic colon findings are found on prenatal ultrasonography, it is desirable to conduct postnatal examinations for cystinuria.