The European Rare Kidney Disease Reference Network


    Thematic Area: Urinary Tract Dilatation


    The following guidance document has been adopted based on standardized reviews and is followed in all ERKNet centers:

    Multidisciplinary Consensus on the Classification of Prenatal and Postnatal Urinary Tract Dilation
    J Pediatr Urol 2014; 10:982-98

    Core Recommendations:
    1. The anterior-posterior renal pelvic diameter (APRPD) is the preferred measure to characterize the severity of urinary tract (UT) dilatation. The likelihood of resolution of a urinary tract dilation is related to the APRPD at initial diagnosis.

    2. The term “UT dilatation” should be used consistently.  The use of non-specific terms (e.g. hydronephrosis, pyelectasis, pelviectasis, uronephrosis, UT fullness or prominence, and pelvic fullness) should be avoided.  

    3. Prenatal risk stratification:  
      Low risk (UTD A1): APRPD 4 to <7 mm at <28 weeks, 7 to <10 mm at >28 weeks,
      ± central calyceal dilation, renal parenchyma of normal thickness and appearance, ureter not visible, normal bladder, no oligohydramnios
      Increased risk (UTD A2-3):  APRPD >7 mm at <28 weeks, >10 mm at >28 weeks,
      or any one of the following: dilation of peripheral calyces, abnormal parenchymal thickness or appearance, visibly dilated ureter, abnormal bladder, oligohydramnios

    4.  Postnatal risk stratification: 
      Low risk (UTD P1):  APRPD 10 to <15 mm (examined >48 h after birth)
      ± central calyceal dilation (with APRPD <10mm), renal parenchyma of normal thickness and appearance, ureter not visible, normal bladder.
      Intermediate risk (UTD P2):  APRPD >15 mm + central or peripheral calyceal dilation (with APRPD<15 mm), ± dilated ureter. Normal renal parenchymal thickness and appearance
      High risk (UTD P3): UT sonographhic findings as in UTD P2, with renal parenchymal thinning, increased echogenicity and/or decreased corticomedullary differentiation (even if APRPD <15 mm), or abnormal bladder (wall thickening, ureterocele, posterior urethral dilatation).


    Comments by Evaluators:
  • Consensus document with recommendations based on literature evidence.
  • Recommendations were made by a panel of specialists, without external review.
  • There are future research directions that will help to improve the evidence for recommendations.