Fetal Lower Urinary Tract Obstruction (LUTO): a practical review for providers

Treatment

As mentioned earlier, elective termination of the pregnancy should be discussed with couples facing a child with LUTO. Those that elect to continue the pregnancy should meet with a Pediatric Nephrologist and Urologist to review the possible postnatal courses including short and long-term outcomes (e.g. dialysis, transplantation) so that realistic expectations are set.

For fetuses with a favorable prognostic indicators (Table 1) and oligohydramnios, treatment is predominantly aimed at restoration of amniotic fluid volume for prevention of pulmonary hypoplasia, and urinary decompression for attenuation of on-going renal damage [20, 24]. Treatment options for this subset of fetuses includes vesicoamniotic shunting (most commonly used), valve ablation via cystoscopy, and vesicostomy.

Vesicoamniotic shunting is a percutaneous procedure performed under ultrasound guidance, using local anesthesia for maternal pain relief [7]. Prior to placement of the shunt, an amnioinfusion (e.g. warm sterile saline infused with Nafcillin) is routinely required to allow space for deployment of the proximal end of the catheter. Fentanyl (15 ?gLKg) and pancuronium (0.5–2 mg/Kg) injection into the umbilical vein or into the fetal arm muscle may be used for fetal anesthesia. A double pig tailed catheter (Rodeck/Rocket or Harrison shunts) is then placed with the distal end in the fetal bladder, and proximal end within the amniotic cavity (Fig. 3) [2]. It must be noted that due to the small caliber and long length of the shunts, complete decompression of the bladder or the urinary tract may not be seen in all cases, especially those with a high-grade obstruction. The outcomes associated with vesicoamniotic shunting are not clear [28]. Data to date have not proven reliable due to heterogenous patient populations. Furthermore, the most recent randomized trial aimed at examining the utility of vesicoamniotic shunting (PLUTO Trial) ended prematurely without answering this important question due to poor recruitment, although anecdotal evidence appears to point to improved outcomes with this intervention [5, 28].

Ultrasound image of a vesicoamniotic shunt with the two catheter ends (S) in the fetal bladder (B) and amniotic cavity (A)

Fetal cystoscopy, which is technically more difficult than vesicoamniotic shunt placement, is an emerging treatment option for LUTO [29–31]. This option holds several advantages over shunting in that it allows for direct visualization of the obstruction to ascertain specific diagnosis (Fig. 4), and does not require an amnioinfusion [2]. Given the need for minimal maternal movement, as well as the longer procedure duration, consideration should be given for maternal regional (epidural or spinal) anesthesia, rather than local analgesia. Similar to vesicoamniotic shunting, fetal anesthesia may be accomplished by injecting fenatnyl (15 ?gLKg) and pancuronium (0.5–2 mg/Kg) into the umbilical vein or into the fetal arm muscle. Using a larger trocar (2.2 mm) than used for vesicoamniotic shunting (1.6 mm), a 1.0 mm fetoscope in a curved sheath and at least a 70° field of view is used for cystoscopy [2, 5, 17, 32, 33]. After confirming that the trochar is inside the fetal bladder, the fetoscope is introduced into the sheath, and advanced toward the bladder neck and the dilated posterior urethra. If a membrane-like obstruction of the urethral lumen is seen, the diagnosis of PUV is confirmed and the valves can be treated using hydroablation, guide-wire or laser fulguration [2, 5, 17, 32, 33]. However, if a non-membrane-like structure is found, even with the fluid injection, the UA is diagnosed and no attempt to perforate this structure is performed, and a vesicoamniotic shunt is placed [2, 5, 17, 32, 33]. The main complication of fetal cystoscopic laser ablation of PUV is urological fistula, which seems to be associated with less operator experience, elevated laser power/energy and less curved instruments [34]. Therefore, percutaneous fetal cystoscopy is useful for diagnostic as well as therapeutic purposes in LUTO, however it is necessary to have adequate experience and instruments to perform this challenging procedure. Lastly, given that this procedure remains experimental, it should be performed under institutional review board approval.

Fetal cystoscopy image within the bladder (B) demonstrating the point of obstruction at the urethra (U)

Fetal vesicostomy, via open fetal surgery, is yet another treatment option for LUTO [35, 36]. However, despite its promising neonatal results, the associated maternal and perinatal morbidity, along with the paucity of large scale data preclude it’s widespread use for the treatment of LUTO at this time. In addition, this technique does not improve the bladder function [35]. Despite the promising results for each of the above interventions, there remains a paucity of high quality data supporting the use of fetal intervention in cases of LUTO with a favorable prognostic profile and oligohydramnios.

With respect to outcomes for the abovementioned intervention, a recent review by Morris and Kilby provided a useful overview [7]. Vesicoamniotic shunting improved perinatal survival when compared with no treatment (odds ratio (OR) 3.86; 95 % confidence intervals (CI) 2.00–7.45), albeit at the expense of residual risk of poor long-term postnatal renal function (OR 0.67, 95 % CI 0.22–2.00). Similarly, cystoscopy appears to improve perinatal survival by an OR of 20.51 (95 % CI 3.87–106.89); however, when compared to shunting, there appears to be no significant improvement in perinatal survival OR 1.49 (0.13–16.97). Appropriately, they concluded that while prenatal intervention appears to improve perinatal survival, there might be a trend towards increased childhood morbidity (associated with chronically poor renal function) in the survivors, a point which should be made clear to the parents at the time of diagnosis [7].

Expectant management is yet another option for couples facing this serious problem in their child. In cases of LUTO with preserved normal amniotic fluid levels, favorable pulmonary function should be expected. The parents should meet with pediatric subspecialists to prepare for the postnatal course, which may include surgery and dialysis. In cases of LUTO with oligohydramnios, palliative care should be offered. In the event the parents decline palliative care, consultation with pediatric subspecialists, especially Neonatology should be undertaken to prepare the parents for expected complications especially pulmonary hypoplasia. Furthermore, discussions between the obstetric team and the parents should be held to review parental wishes for intervention in the event of non-reassuring fetal status considering the poor prognosis.

Lastly, consideration for intervention should be given for those fetuses with a poor prognostic profile, or end-stage fetal renal disease, which are not candidates for the above interventions [2]. While termination of the pregnancy or palliative care is the uniformly accepted recommendation for these cases, they may not be an option for some parents due to personal or religious beliefs. In such instances, under an experimental and case-by-case basis, some groups (including the author) have offered serial amnioinfusions(Fig. 5) for pulmonary palliation [37, 38]. The couple is asked to meet with Neonatology, Pediatric Urology, and Pediatric Nephrology to thoroughly review the expected outcomes (including morbidity and mortality) of a neonate with end-stage renal disease requiring dialysis and transplantation. If still interested, serial amnioinfusions are performed for oligohydramnios until 28–30 weeks, and delivery for fetal distress reserved until an estimated fetal weight of 2–2.5 kg to allow for peritoneal dialysis cathether placement candidacy. It must be noted that this intervention is experimental, and large-scale studies are needed to assess its utility and safety.