Fetal interventions for obstructive uropathy

Congenital urinary tract obstruction

Congenital bladder neck obstruction (or lower urinary tract obstruction [LUTO]) describes a heterogeneous group of congenital anomalies presenting with similar prenatal ultrasonographic findings of dilated posterior urethra, megacystis, hydronephrosis, oligohydramnios and often with associated renal dysplasia. Untreated LUTO has high rate of perinatal morbidity and mortality from associated pulmonary hypoplasia and early-onset renal failure in infancy. Ultrasonographic features and prospective fetal urinalysis may help in predicting the overall prognosis of congenital LUTO. Currently, fetal vesicoamniotic shunt (of various designs), and fetal cystoscopy and fulguration of the obstruction are potential prenatal interventions. Retrospective and prospective cohort studies and a relatively small randomized controlled trial have demonstrated these treatments may possibly improve perinatal survival. Despite this, concerns remain as to the high rates of renal impairment observed in paediatric survivors. A clinical prospective scoring/staging system may improve prenatal diagnostic criteria and case selection for fetal therapy.

Advances in Fetal Surgery

Advances in prenatal screening and diagnosis, combined with an understanding of the pathophysiology of congenital anomalies, have brought incredible impetus to the field of fetal surgery. Identification of fetal anomalies can lead to counseling of the affected family so that informed decisions can be made on how to proceed with the pregnancy. Counseling may lead to pregnancy termination, changes in the timing or mode of delivery, and, in select cases, prenatal intervention. Open fetal surgery may be considered in severe cases of congenital diaphragmatic hernia, congenital chest lesions, sacrococcygeal teratoma, urinary tract obstruction, and myelomeningocele. The ex utero intrapartum treatment procedure may be lifesaving for fetuses with giant neck masses. Finally, fetoscopic surgery may be offered for select cases of twin-twin transfusion syndrome and twin reversed arterial perfusion sequence. Fetal intervention in all of these cases depends on a team approach to the patient and on the objective comparison of outcomes with and without fetal therapy. In the future, further understanding of the genetic basis of congenital diseases may enable minimally invasive treatments such as stem cell transplantation or gene therapy.

Current applications of in utero intervention for lower urinary tract obstruction

PURPOSE

Since the early 1980s with the inception of fetal intervention for obstructive uropathy, there have been creative attempts to improve both perinatal and long-term outcomes. Despite advances in technology and an improved understanding of lower urinary tract obstruction (LUTO) in the fetus, the results for these therapeutic interventions remain guarded and the long-term renal morbidity among survivors remains problematic.

RECENT FINDINGS

Fetal LUTO represents a range of disorders but the most common of these is posterior urethral valves (PUVs). Selection criteria for candidates of possible intervention have improved with our understanding of fetal renal physiology. Serial urinalysis has marginally improved our ability to predict those that may ultimately respond to treatment [1,2], but the potential in the development of biomarkers for renal development or maldevelopment holds greater promise [3]. Advancements in fetal surgery may result in less fetal and maternal morbidity, but limited long-term improvement in outcomes highlights the controversial nature of the various interventions [4-10]. We must counsel families that fetal surgery offers hope but we cannot allow them to hold unrealistic expectations for cure.

SUMMARY

In appropriately selected fetuses, intervention may improve perinatal survival but not without risk to mother and fetus. Long-term renal outcomes remain problematic amongst survivors. In the case of PUV, postnatal primary valve ablation remains the cornerstone of treatment for nephron preservation; however, our ability to mimic these results in the prenatal population remains poor [11]. Disease severity has likely predetermined those that will survive through the perinatal period with or without intervention. Nonetheless, our drive to assess and manage fetal obstructive uropathy perseveres so that we may ultimately relieve obstruction and preserve renal and lung function. We must maintain optimism that continued advances will ultimately improve outcomes, but also be realistic with our current expectations. This paper reviews the status of current in utero interventions and outcomes.

Fetal counselling for surgical conditions

Foetal counselling is best achieved by a multidisciplinary team that can favourably influence the perinatal management of prenatally diagnosed anomalies and provide this information to prospective parents. Prenatal diagnosis has remarkably improved our understanding of surgically correctable congenital malformations. It has allowed us to influence the delivery of the baby, offer prenatal surgical management and discuss the options of termination of pregnancy for seriously handicapping or lethal conditions. Antenatal diagnosis has also defined an in utero mortality for some lesions such as diaphragmatic hernia and sacrococcygeal teratoma so that true outcomes can be measured. The limitation of in-utero diagnosis cannot be ignored. The aim of prenatal counselling is to provide information to prospective parents on foetal outcomes, possible interventions, appropriate setting, time and route of delivery and expected postnatal outcomes, immediate and long term.

Prenatal ultrasound guided percutaneous shunts for obstructive uropathy and thoracic disease

The authors reviewed the status of closed ultrasound-guided fetal therapy using a pigtail shunt to create vesicoamniotic or thoracoamniotic decompression of the fluid-filled space. This review includes published and textbook reports of in utero therapy for bladder obstruction, pleural effusion, and macrocystic adenomatoid malformation from 1985 through 2002. For fetuses affected by lower urinary tract obstruction, the key component is identifying those fetuses that have retained renal function and are most likely to benefit from in utero shunting. This good prognosis group has been shown to have improved survival rate and a lower incidence of renal failure. Complications of fetal loss are estimated at 5% owing to the shunt procedure, and the risk of shunt displacement varies from 30% to 50%. Hydrops secondary to primary PE has been shown to be associated with low fetal and neonatal survival at 21% to 23%. Treatment by thoracoamniotic shunting increases survival rate to 75%. The fetus with a macrocystic CCAM and secondary hydrops should be considered a candidate for thoracoamniotic shunt to decrease CCAM volume, reverse hydrops, and improve survival rate. Thoracoamniotic shunt and thoracocentesis pregnancy loss risks for pleural effusion (PE) and macrocystic adenomatoid malformation of the lung (CCAM) are 5% and 0.5% to 1.0%, respectively.

Minimal access fetal surgery

The development of fetal surgery has led to promising therapeutic options for a number of congenital malformations. However, preterm labor (PTL) and premature rupture of membranes continue to be ubiquitous risks for both mother and fetus. To reduce maternal morbidity and the risk of prematurity, minimal access surgical techniques were developed and are increasingly employed. Congenital diaphragmatic hernia (CDH), obstructive uropathy, twin-to-twin transfusion syndrome (TTTS), and sacrococcygeal teratoma have already been successfully treated using minimal access fetal surgical procedures. Other life-threatening diseases as well as severely disabling but not life-threatening conditions are potentially amenable to treatment. The wider application of minimal access fetal surgery depends on a continued improvement in technology and a better understanding of complications associated with fetal intervention.