Bladder tract or lower urinary tractobstruction (LUTO) represents a prenatal uropathy with a great impact on neonatal and child health . Congenital anomalies of the urinary tract are relatively common, as they affect approximately 1:500 pregnancies, while obstructive uropathies account for the majority of cases [8, 14].
Urinary tract obstruction may present at different levels, unilateral or bilateral. The widespread use of prenatal ultrasonography contributed to an increased awareness of posterior urethral valve (PUV) and early detection of hydronephrosis in almost all fetuses .
The fetal treatment of LUTO may be helpful in avoiding perinatal mortality and morbidity, which are very high because of anyhydramnios and renal damage, and subsequent pulmonary hypoplasia, neonatal death, post renal failure, and renal impairment. Different therapeutic surgical methods have been proposed for severe LUTO, such as vesicocentesis, vesico-amniotic shunting, and fetal cystoscopy .
We present a case series of LUTO treated by intrauterine mechanical perforation of posterior urethral valves using an 18-gauge needle under ultrasound guidance, which might be proposed as a new method for prenatal therapy.
From February 2008 to January 2012, 15 fetuses with magacystis were referred to our tertiary referral center. After a detailed ultrasound scan, six fetuses showed a corresponding fetal biometry, no signs of other morphologic anomalies, oligo-anhydramnios defined as a maximum vertical pocket <50 mm, renal polar lengths within normal limits for fetal gestational age, and the “keyhole sign”. Nine fetuses presented with magacystis, anhydramnios, and dysplastic kidneys. Fetal karyotype was assessed by performing amniocentesis, when possible during the procedure, and a fetal urine sample was taken through vesicocentesis to assess kidney function (sodium <100 mmol/L, chloride <90 mmol/L, osmolarity <200 mOsm/L, calcium <2 mmol/L, and β-2 microglobulin <508 mmol/L). There were five female and ten male fetuses. Nine cases opted for pregnancy termination, as the kidneys were dysplastic showing hiperechoic structure, while six cases were treated as the kidneys showed a normal cortico-medullar differentiation. Among them, five fetuses were male and one was female. All six women gave consent to proceed with fetal therapy using an 18-gauge needle. All women were informed about the risk of the procedure from the Fetal Diagnosis and Therapy Unit at the University of Padua, which consisted of a 0.5% chance of rupture of the membranes and fetal death.
Considering gestational age and the typical ultrasound keyhole sign, an intervention for bladder decompression was decided. The posterior hypertrophic urethral valve was mechanically punctured using an 18-gauge needle. All the procedures lasted a median time of 30 min (range 15–50 min). This time varied according to each fetus as all procedures were performed under ultrasound guidance and the operator waited for the correct position of the fetus in order to reach an angle of 0–20 degrees between the needle and the perineal surface of the fetus lying in a dorsal position. At this moment, the needle was inserted through the dilated posterior ureteral valve.
A follow-up was performed in all fetuses after 2 days and in all fetuses the bladder size was reduced with regular peristaltic activity and correct emptying; a regular cortico-medullar differentiation for both kidneys and average amniotic fluid volume. A transient bilateral pyelectasis defined as presence of fluid in the kidney <4 mm measured in a coronal section of the kidneys was detected at 2 weeks follow-up. All patients underwent a close fetal surveillance, revealing a reduction of the kidney pyelectasis in association with mild ureterocele at the following evaluation of all fetuses. Nevertheless, both kidneys were normal size without any atrophy or dysplasia signs, the amniotic fluid volume remained normal, and the bladder size was further reduced. Ultrasound at mid trimester showed normal amniotic fluid volume, an improvement of upper tract dilatation, and a progressive resolution of the ultrasound signs at follow-up after 2 weeks.
At term, four women delivered by elective cesarean section because of previous surgery and two vaginally. Apgar scores were normal at 1 min and 5 min. Vital signs and respiratory parameters were optimal. Respiratory, cardiac, and musculoskeletal examinations were all within normal limits. Moreover, all newborns presented an appropriate urine output and a normal bowel movement. Renal ultrasonography showed normal echo-texture of both kidneys and absence of hydronephrosis bilaterally, normal renal function was confirmed with blood and urinary exams (sodium <100 mmol/L, chloride <90 mmol/L, osmolarity <200 mOsm/L, calcium <2 mmol/L, and β-2 microglobulin <508 mmol/L). Four neonates underwent cystoscopy and two of them required ablation for residual.
The following pediatric evaluations did not find any other morphologic anomalies and the newborn renal function was considered completely normal as kidney functionality was repeated.
Fetal megacystis is defined as an abnormally enlarged bladder identified at any gestational age, typically appearing after 10 weeks of gestational age, when the fetus starts to produce urine. It has an incidence of 0.06–0.3% of all pregnancies [4, 7].
Megacystis is not a disease per se, but a manifestation of various underlying pathologies. While congenital obstruction of the anterior urethra is rare, PUVs remain the most frequent obstructive lesion of the lower system causing megacystis, especially in male fetuses, with an incidence of 1 in 2500–5000 births [4, 11]. PUV represents 10.7% of all cases, and is the most frequent cause of terminal renal failure in early childhood . The other causes include prune belly syndrome, urethral atresia, megaureter, megacystis-microcolon-hypoperistalsis syndrome, neurogenic bladder, obstructive uropathy, and primary vesicoureteral reflux [1, 10].
The congenital posterior urethral segment occlusion is caused by hypertrophy of the normal prostatic urethral valve because of incomplete differentiation of the terminal part of mesonephric ducts or of persistence of the urogenital membrane, however, the etiology is supposed to be multifactorial . The affected fetus is typically male, while females often have more complex pathologies, such as megacystis microcolon syndrome [8, 10]. Chronic LUTO may lead to abnormal renal development and function, progressive renal dysfunction to severe oligohydramnios, predisposing the fetus to pulmonary hypoplasia, and positional limb abnormalities [7, 8]. Therefore, a high proportion of severe megacystic fetuses are aborted . The mortality rate secondary to PUV ranges from 24% to 54%, even if hemodialysis, excellent broad-spectrum antibiotics, and improvements in neonatal intensive care units have contributed equally to the decline in mortality .
The sonographic evidence of LUTO is the presence of severe oligohydramnios, a grossly distended urinary bladder with increase in bladder wall thickness . Furthermore, PUV is suspected in presence of the so-called “keyhole” sign, a dilatation of the distended posterior urethra, which is considered a sign of posterior urethral valves, together with the wall thickness and dilatation of the bladder . The outcome of pregnancy and long-term prognosis principally depends on the amniotic fluid index  as it reflects the degree of involvement of the fetal kidneys, which can be ascertained ultrasonographically and biochemically .
The most important question is the effectiveness of in utero therapy and the correct timing, as its management constitutes an ongoing challenge in obstetric and pediatric practices. Animal models have suggested that decompressing the obstruction may modify the pathogenesis, and prenatal in utero therapy has been considered in “selected” cases in an attempt to improve survival rate and reduce complications, even if in one third of treated cases still has a renal failure risk .
Obstetric management is influenced by possible associated chromosome abnormalities, amniotic fluid volume, gestational age, and residual renal fetal function, evaluated by vesicocentesis to assess urinary electrolytes and osmolality .
Current therapies include percutaneous vesico-amniotic shunting [5, 6, 8, 9, 13, 16, 19] and in utero fetoscopic ablation of valves by percutaneous fetal cystoscopy that allows laser valve ablation [12, 15] and mechanical disruption of posterior urethral valves [3, 4, 8, 17, 18, 20].
Vesicoamniotic shunting corrects the existing oligohydramnios, although the perinatal mortality and long-term survival after this procedure remains poor, with a 45% complication rate, including shunt blockage or dislocation, preterm delivery, urinary ascites, and infections .
Valve ablation may be advantageous as it allows restoration of normal fetal bladder dynamics, avoiding predisposition to aberrant detrusor contractions and dysfunction in children with PUV. A meta-analysis on the utility of vesicoamniotic drainage showed an improved overall perinatal survival versus the non-drainage group, especially in poor prognosis fetuses . It may be performed by fetal cystoscopy, whose advantage may be a more physiological drainage of the obstructed bladder and an endoscopic examination of the dilated posterior urethra, allowing the direct diagnosis of the cause of the obstructive uropathy. However, this procedure needs maternal and fetal anesthesia and uses a fetoscope, which is a larger instrument and has difficulty in trocar insertion and bladder stabilization [3, 14].
In this study, we report a new procedure using a mechanical puncture of the posterior valve through an 18-gauge needle, with an effective and definitive treatment of the urethral obstruction that caused megacystis. In all cases, the procedure was effective and no complications were observed. The early and reliable diagnosis was fundamental in choosing the correct approach, therefore, the study of fetal morphology, karyotype, the characteristics of the abnormally distended urinary system and the kidneys, in their size and echo structures, the amniotic fluid, and eventually, the keyhole sign, have to be investigated.
The limits of the technique described are the risks linked to an invasive procedure, such as infections and chorioamnionitis, membrane rupture, mistakes in site of fetal puncture, hematomas, and placental abruption. Moreover, the experience of the operator and the difficulty to standardize the procedure should be considered. However, in respect to fetal fetoscopy, this technique shows less invasiveness, a possibility of a successful procedure, a rapid learning curve for the operator, and the possibility to carry out it at any center, as it does not require any special surgical instrumentation. Evaluating all the described aspects and considering the achieved result, our experience confirms that intrauterine intervention, being well codified and in skilled hands, is a possible and good alternative to temporary vesico-amniotic shunting.
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About the article
Published Online: 2014-01-17
Published in Print: 2014-08-01
The authors stated that there are no conflicts of interest regarding the publication of this article.