Urinary tract dilatation classification

Urinary tract dilatation (UTD) classification was a proposed unified classification of urinary tract dilatation for prenatal and postnatal care. This classification was formed with the collaborations from 8 societies (The American College of Radiology (ACR), the American Institute of Ultrasound in Medicine (AIUM), the American Society of Pediatric Nephrology (ASPN), the Society for Fetal Urology (SFU), the Society for Maternal-Fetal Medicine (SMFM), the Society for Pediatric Urology (SPU), the Society for Pediatric Radiology (SPR), and the Society of Radiologists in Ultrasounds (SRU)) ¹. 

Classification

The UTD classification system uses 6 ultrasound findings to describe the urinary tracts: 

• anterior-posterior renal pelvic diameter (APRPD)
• calyceal dilation with distinction between central and peripheral calyces postnatally
• renal parenchymal thickness 
• renal parenchymal appearance
• bladder abnormalities 
• ureteral abnormalities

Antenatal

Applicable after 16 weeks gestation:

UTD A1

• anteroposterior renal pelvic diameter
  • 16 to 27 weeks: 4 mm to <7 mm
  • ≥ 28 weeks: 7 mm to <10 mm
• with or without central calyceal dilatation

UTD A2-3

• anteroposterior renal pelvic diameter
  • 16 to 27 weeks: ≥7 mm
  • ≥28 weeks: ≥10 mm
• peripheral calyceal dilatation
• abnormal parenchyma thickness or appearance
• abnormal ureter or bladder
• unexplained oligohydramnios

Postnatal

Applicable after 48 hours of life:

UTD P1 (low risk)

• anteroposterior renal pelvic diameter 10 mm to <15 mm
• central calyceal dilatation

UTD P2 (intermediate risk)

• anteroposterior renal pelvic diameter ≥15 mm
• peripheral calyceal dilatation
• abnormal ureter

UTD P3 (high risk)

• anteroposterior renal pelvic diameter ≥15 mm
• peripheral calyceal dilatation
• abnormal parenchymal thickness or appearance
• abnormal ureter
• abnormal bladder

See also

• hydronephrosis grading
• fetal hydronephrosis
• fetal pyelectasis
• neonatal hydronephrosis