Dr. Pixel mascot
Dr Pixel 2.0Women's imaging diagnosis

PLATFORM FOR EDUCATION AND DECISION SUPPORT IN WOMEN'S IMAGING

Start here

Interactive Checklist

Fill in the findings in order. The checklist applies UTD criteria and displays the classification automatically.

Understand the classification

How UTD classification works

The UTD (Urinary Tract Dilation) classification uses 6 ultrasound findings to stratify the risk of significant uropathy, with different criteria depending on the phase (prenatal or postnatal) and, prenatally, on gestational age.

Do baixo ao alto risco

Escalas de risco UTD

Pré-natal
UTD A1
Baixo risco
UTD A2
Risco intermediário
UTD A3
Alto risco
Pós-natal
UTD P1
Baixo risco
UTD P2
Risco intermediário
UTD P3
Alto risco

APRPD thresholds (anteroposterior renal pelvis diameter)

FaseLeveModeradoGrave
Prenatal, 16–27 weeks≥ 4 mm≥ 7 mm≥ 10 mm
Prenatal, ≥ 28 weeks≥ 7 mm≥ 10 mm≥ 15 mm
Postnatal≥ 10 mm (abnormal)≥ 15 mm—

Criteria by category

UTD A1 / P1 (low risk)

Mild/abnormal APRPD, no peripheral dilation (or central, postnatally), normal parenchyma and bladder.

UTD A2 / P2 (intermediate risk)

Moderate APRPD, or peripheral dilation, or dilated ureter — without parenchymal or bladder changes.

UTD A3 / P3 (high risk)

Any parenchymal or bladder change, or (prenatally) severe APRPD or unexplained oligohydramnios — regardless of other findings.

Common questions

Frequently asked questions about UTD classification

Why does the APRPD threshold change with gestational age?+
Because the fetal renal pelvis grows throughout pregnancy — between 16 and 27 weeks the thresholds are 4/7/10 mm (mild/moderate/severe); from 28 weeks they rise to 7/10/15 mm.
What APRPD is considered abnormal postnatally?+
From 10 mm, postnatal APRPD is considered abnormal, and from 15 mm it becomes a UTD P2 criterion.
What makes a finding classify as UTD A3 or P3 (high risk) regardless of APRPD?+
Any renal parenchymal or bladder change already classifies as high risk (A3/P3), even if APRPD alone would suggest a lower category. Prenatally, unexplained oligohydramnios also raises it to A3.
Does peripheral (caliceal) dilation always indicate high risk?+
Not necessarily: peripheral dilation without parenchymal or bladder changes is an intermediate-risk criterion (A2/P2). A dilated ureter prenatally, however, is already a high-risk criterion (A3).
Is the UTD classification the same before and after birth?+
No — criteria differ: prenatally, APRPD thresholds vary with gestational age; postnatally, the exam is usually repeated at ≥ 48h of life to reduce the effect of the newborn’s relative dehydration in the first hours.