Ultrasound screening for renal and urinary tract anomalies in healthy infants.

BACKGROUND: Nearly 30% of childhood cases of chronic renal failure in Japan are attributed to congenital anomalies of the kidney and urinary tract (CAKUT), and the number is increasing. Urine screening at school facilitates early diagnosis and treatment of glomerulonephritis, but early screening for anomalies is currently not in practice. The authors evaluated the value of early abdominal ultrasonography screening in 1-month-old infants. METHODS: The following characteristics of kidneys were assessed: presence versus absence, size, symmetry of size, position, separation of the central echo complex (CEC), abnormal echogenicity, and other abnormal findings. The bladder and ureter were checked for abnormalities in bladder shape and wall, as well as retrovesical ureteral dilation. Criteria for abnormalities included kidney length of or=60 mm; a difference in length of left and right kidneys of 10 mm or more; and CEC separation of Society for Fetal Urology (SFU) grade 2 or higher. RESULTS: Beginning in April 1994 and continuing until September 2001, screening of 5700 1-month-old infants yielded 198 positive cases (3.5%) of CAKUT. Most frequent was abnormal CEC separation (approximately 60% of all abnormalities), followed by abnormal renal size or size asymmetry (30%). Further investigation yielded a specific diagnosis in 32 cases (0.6%) of all subjects. Most prevalent was obstructive uropathy (15 cases); 8 children underwent surgery. Small kidneys and vesicoureteral reflux were next in frequency. CONCLUSIONS: Ultrasonograpy was effective for early detection of renal and urinary tract anomalies. Ultrasound screening in early infancy may permit early treatment, that can prevent renal dysfunction.

Mass screening for early detection of congenital kidney and urinary tract abnormalities in infancy.

BACKGROUND: Recent widespread use of ultrasound has led to new efforts at screening for congenital kidney and urinary tract abnormalities. However, a standard screening methodology, criteria defining abnormalities, and follow-up procedures remain to be established. In order to establish screening criteria for these abnormalities, we performed a preliminary study in 800 1-month-old infants using provisional methods and criteria. METHODS: Based on the results of preliminary study, we screened 2700 1-month-old infants in a prospective study using the criteria of renal size (longitudinal diameter or=60 mm, or a difference between sides of >or=10 mm), and of pelvic dilatation (Society for Fetal Urology [SFU] grade 2 or higher) as positive at the first ultrasound screening. We used the SFU grading system instead of anteroposterior pelvic diameter measurements for pelvic dilatation. RESULTS: One hundred and twelve (4.1%) of the 2700 infants had abnormalities at the first ultrasound screening, while 18 (0.67%) had congenital kidney and urinary tract abnormalities on further examination. Use of the SFU grading system enabled us to reduce the false-positive rate at first screening, while maintaining a high diagnostic rate. The abnormalities consisted of ureteropelvic junction obstruction in seven infants, megaureter in two, hypoplastic kidney in four, vesicoureteral reflux in six (three were accompanied by hypoplastic kidneys or multicystic dysplastic kidney), multicystic dysplastic kidney in one, and horseshoe kidney in one. CONCLUSION: These results indicate that our screening methods and criteria are useful variables for detecting congenital kidney and urinary tract abnormalities.