Fetal Lower Urinary Tract Obstruction (LUTO)

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.

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Full pathway

1. [Decision] Bladder/kidney/fluid + renal function prognosis
   Bladder/kidney/amniotic fluid signs + renal function prognosis? (LUTO = bladder outlet obstruction, most commonly posterior urethral valves (PUV, males only, 63%); the rest urethral atresia (10%, M/F), etc. Typical: megacystis, thickened bladder wall, dilated posterior urethra keyhole sign (PUV), bilateral hydronephrosis, oligohydramnios; echogenic/cystic renal cortex = dysplasia. Oligohydramnios → pulmonary hypoplasia (lethal). Megacystis = bladder longitudinal diameter >7 mm in the first trimester or not emptying over 45 minutes.)
   • Megacystis ± hydronephrosis, normal fluid, normal renal parenchyma → Early/normal fluid · monitor
   • Oligohydramnios/anhydramnios, echogenic or cystic cortex (dysplasia), isolated lesion → Oligohydramnios + renal dysplasia → assess shunt
   • Megacystis + associated anomalies/chromosomal abnormality or complex female fetus (cloacal/MMIHS) → Complex/non-isolated · genetics first
2. [End] Early/normal fluid · monitor
   Megacystis ± hydronephrosis, fluid still normal, normal renal parenchyma: detailed survey for associated anomalies + karyotype/microarray; serial monitoring of fluid and renal parenchyma (echogenicity/cysts); for male, isolated, good renal-function prognosis, assess intervention timing; note ~23% false positives.
3. [End] Oligohydramnios + renal dysplasia → assess shunt
   Oligohydramnios/anhydramnios + echogenic or cystic renal cortex (dysplasia), isolated lesion: high risk of pulmonary hypoplasia and renal failure (PUV mortality 30–50%, up to 77% with oligohydramnios); serial fetal urine biochemistry to assess renal function (sodium <100, chloride <90, osmolality <200, beta-2 microglobulin <6 are favorable); favorable → vesicoamniotic shunt or fetal cystoscopy (PUV valve ablation) to restore fluid and protect the lungs; multidisciplinary counselling.
4. [End] Complex/non-isolated · genetics first
   Megacystis + associated anomalies/chromosomal abnormality or complex female fetus (cloacal malformation/MMIHS/prune belly): karyotype/microarray + detailed anatomy first; shunting has limited benefit for non-isolated obstruction or MMIHS; multidisciplinary + genetic counselling, individualized decision.

Source guidelines & references

• Fetal lower urinary tract obstruction diagnosis and intervention (UOG 2024 Delphi consensus; PLUTO)

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.

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