Fetal Hydronephrosis (UTD Classification)

Step-by-step decision

Choose step by step as prompted; reaching an endpoint gives the management recommendation. You can go back a step or restart anytime.

🎓 Want to practice? Do a case challenge with this pathway → (get a case, choose management step by step, scored).

Full pathway

1. [Decision] APRPD + risk parameters (UTD classification)
   APRPD + risk parameters (UTD classification)? (The most common prenatal urinary abnormality. APRPD (anteroposterior renal pelvic diameter, measured at the maximal transverse plane). Abnormal thresholds (NICHD): mid-trimester ≥4 mm, ≥32 weeks ≥7 mm. Increased-risk parameters: peripheral calyceal dilation, ureteric dilation, renal parenchymal abnormality (thin/echogenic), bladder abnormality, oligohydramnios.)
   • UTD A1 low-risk (APRPD 4–<7 mm <28 weeks / 7–<10 mm ≥28 weeks, central calyces only) → UTD A1 low-risk · mostly self-limited
   • UTD A2–3 increased-risk (APRPD ≥7/≥10 mm or peripheral calyces/ureteric dilation/parenchymal abnormality/bladder abnormality) → UTD A2–3 increased-risk · monitor the cause
   • Bilateral severe + thick bladder wall/posterior urethral dilation/oligohydramnios → Bilateral severe → LUTO
2. [End] UTD A1 low-risk · mostly self-limited
   UTD A1 low-risk: mostly transient/physiologic (usually self-resolves); routine antenatal serial ultrasound (mid-trimester + third-trimester recheck), postnatal ultrasound follow-up; good prognosis.
3. [End] UTD A2–3 increased-risk · monitor the cause
   UTD A2–3 increased-risk: serial ultrasound close monitoring (APRPD, calyces, ureter, parenchyma, fluid); causes mostly UPJ obstruction (most common pathology), VUR, UVJ/megaureter, duplex kidney/ureterocele; postnatal ultrasound + VCUG/MAG3 assessment; APD ≥15 mm predicts need for surgery.
4. [End] Bilateral severe → LUTO
   Bilateral severe + thick bladder wall/posterior urethral dilation keyhole sign/oligohydramnios: suggests lower urinary tract obstruction (LUTO) → see the LUTO pathway; pulmonary hypoplasia and renal failure risk; urine biochemistry to assess renal function, vesicoamniotic shunt if needed; multidisciplinary.

Source guidelines & references

• Fetal/prenatal urinary tract dilation UTD classification consensus (J Pediatr Urol 2014; NICHD)

This pathway is our own synthesis of the decision logic in the guidelines above (not the guideline verbatim); thresholds and workflows change as guidelines update — in practice follow the latest guideline, your institution's protocol and the individual patient.

Other pathways