Percutaneous Shunting For Fetal Lower Urinary Tract Obstruction: A Case-Series Study

Abstract

Lower urinary tract obstructions (LUTO) are caused by a narrowing at some point in the urinary tract that slows or stops the flow of urine. They are one of the most commonly identified abnormalities at the antenatal ultrasound scan with an estimated incidence of 1:250 to 1:1000 pregnant women. The majority of these abnormalities are because of obstruction, obstructive uropathy, which may occur at the uretero-pelvic junction or uretero-vesical junction or at the level of bladder neck. The most common identifiable causes of LUTO are urethral atresia and posterior urethral valves (PUVs). Other less common causes of lower urinary tract obstructions include urethral atresia (the second most common cause of lower urinary tract obstructions), anterior urethral valves, meatal stenosis, epispadias, and hypospadias(Ruano, 2011). The idea of the vesico-amniotic shunting or the PLUTO trial is the insertion of catheter with its proximal end in the amniotic fluid and its distal end in fetal urinary bladder to relieve the fetal urinary obstruction in an attempt to avoid renal parenchymal damage and chronic oligohydramnios that in turn adversely affect the pulmonary development. The indicator for immediate success of the procedure is the immediate de-compression of the distended fetal bladder. The mother is to be followed every two weeks till delivery, recording the fetal bladder dimensions, amniotic fluid volume and any observed fetal renal cystic or dysplastic changes till the baby is delivered and the obstruction is relieved surgically in post-natal life (Morris and Kilby, 2006). This observational case series study was conducted on 14 pregnant females diagnosed by antenatal ultrasound as having fetal lower urinary tract obstruction. The cases were recruited from the out-patients clinics and referred for full anomaly scan or already diagnosed with PUV (enlarged fetal bladder, key-hole sign of the urinary bladder, bilateral fetal hydronephrosis,…etc.) and came for further assessment at the Ultrasound Special Care Unit of the Fetus, Ain-Shams University Maternity Hospital. After exclusion of 2 patients, the remaining 12 patients with primary LUTO were divided into 3 groups as follows: Group 1: 4 women with singleton pregnancies underwent repeated ultrasound-guided vesicocentesis every 2 weeks for fetal bladder tapping. Group 2: Another 4 women with singleton pregnancies underwent ultrasonographic follow up every 2 weeks of the amniotic fluid volume, fetal bladder refilling, signs of fetal kidney dysplasia and fetal hydroureter and/or hydronephrosis. Group 3: A last group of 4 women with singleton pregnancies underwent-under sedation- ultrasound-guided vesicoamniotic shunt insertion between the fetal bladder and amniotic cavity for continuous drainage of the accumulated urine in the fetal bladder. All the cases were subjected to the following: Careful history taking including: The personal history (name, age, obstetric history including gravidity, parity, miscarriages, gestational age determination at time of diagnosis and the expected due date). Ultrasound examination:Detailed full fetal anomaly scan and confirmation of the diagnosis were performed (the gestational age of the fetus (via BPD, HC, AC and FL in the 2nd trimester), fetal sex, exclusion of any other gross congenital fetal malformations, amniotic fluid volume measurement and well visualization and estimation of the enlarged fetal bladder (normal diameter is < 7mm in the 1st trimester and < 30mm in the 2nd trimester) and the dilated proximal urethra (giving together the characteristic key-hole sign of PUV). Amniocentesis and Karyotyping: All the patients were subjected to amniocentesis and chromosomal karyotyping to exclude any associated syndromes of chromosomal abnormalities after well-informed written consent given to the mother. All the patients underwent initial vesicocentesis at the time of amniocentesis done to monitor the fetal bladder refilling in the next scan till results of karyotyping appear and the choice of treatment to be done determined. All the allocated fetuses were male, showing the characteristic “key-hole” sign suggestive for PUV with normal amniotic fluid volume and bladder refilling after initial tapping done at same session of amniocentesis and karyotyping. The mean gestational age at time of diagnosis was 25weeks and 17weeks for conservative and intervention group (8 patients) respectively. Chorioamnionitis and ruptured fetal bladder was reported as procedure-related adverse effect in one of the eight patients allocated for the intervention insertion (12.5%). Oligohydramnios occurred in 25% of the conservative group and 62.5% of the interventional group despite a reported shunt in position. Renal dysplasia was observed 50% of the intervention group. No cases showed any signs of maternal injury in both groups. The mean gestational age at time of termination of pregnancy was 35weeks and 25weeks for the conservative group and intervention group respectively. Among the intervention group, the mortality rate was 100% in the first 28days due to extreme prematurity and lung hypoplasia making the benefits of the shunt again questionable. The mortality rate in the conservative group –on the other hand- was 50%, with two babies surviving beyond 28days yet died later due to hidden congenital heart defect and repeated chest infection and NICU admission at 2 months age and 35days respectively giving the overall Hazard ratio of 5.910, 95% CI of 1.671-20.904 and p-value of 0.002 showing that the shunt adds a burden of fetal morbidity and mortality 5 times more than conservative watchful follow up of the fetus and a statistically significant relation between the conservative management and improved perinatal mortality rates compared to previous studies.