Lower Urinary Tract Obstruction (LUTO)

In a healthy pregnancy, the baby swallows amniotic fluid and then urinates it back out—this 'recycling' is what maintains the fluid levels.

In LUTO, the urine is trapped inside the baby. This causes:

• Bladder Distension: The bladder becomes very large and thin-walled.
• Kidney Damage: The 'back-pressure' of the trapped urine can damage the delicate developing kidneys (nephropathy).
• Lung Hypoplasia: Without the fluid around the baby to breathe in and out, the lungs cannot expand and grow properly.

On ultrasound, we often see the characteristic 'Keyhole Sign', which is the distended bladder and the dilated first part of the urethra.

LUTO is a spontaneous condition affecting approximately 1 in 5,000 to 7,500 births.

It is almost exclusively found in male babies. It can be caused by Posterior Urethral Valves (the most common and treatable form), Urethral Atresia (a more severe blockage), or Triad Syndrome. Diagnosis is usually initiated during the 12-week or 20-week scan when the bladder appears disproportionately large.

The diagnosis of LUTO requires a series of expert assessments to determine if the baby's kidneys can still be saved:

1. Ultrasound Evaluation: Looking for the 'Keyhole Sign' and assessing the appearance of the kidneys. If the kidneys look 'bright' (echogenic) or have cysts, it may indicate irreversible damage.
2. Bladder Taps (Vesicocentesis): We use a fine needle to take a sample of the baby's urine directly from the bladder. We test this urine for electrolytes (sodium, chloride, calcium). If the levels are low, it suggests the kidneys are still functioning well enough to benefit from treatment.
3. Fetal Cystoscopy: In some cases, we use a tiny camera to look inside the baby's bladder to identify the exact cause of the blockage.

Management focuses on bypassing the blockage to save the lungs and kidneys:

• Vesico-amniotic Shunting: We place a small, 'pigtail-shaped' plastic tube (shunt) through the mother's abdomen into the baby's bladder. One end stays in the bladder and the other in the amniotic space, allowing urine to drain freely. This restores the amniotic fluid and allows the lungs to grow.
• Monitoring: We monitor the shunt position and the baby's growth weekly.
• Postnatal Care: Immediately after birth, the baby is cared for by a Pediatric Urologist who will perform a permanent surgical fix to remove the blockage.

The survival and health of babies with LUTO depend on two factors: the timing of the blockage and the health of the kidneys.

• With Treatment: Successful shunting can restore amniotic fluid and lead to a survival rate of approximately 60-70%, though many of these children will face long-term kidney health challenges.
• Without Treatment: If the fluid is completely absent early in pregnancy, the survival rate is very low due to the lungs being too small to function.
• Long-term: Many LUTO survivors require ongoing care from nephrologists and urologists throughout childhood.

If your doctor has mentioned that your 'baby's bladder is too big' or that there is 'very little fluid and it's a boy,' you must be referred to the MFM Unit for a specialized LUTO evaluation.

The decision to place a shunt is time-sensitive and requires expert interpretation of fetal urine biochemistry. Our team, led by Dr. Werner Diehl, is one of the few in the region with the procedural volume and technical expertise to perform fetal shunting and cystoscopy safely.