Can a pressure-limited vesico-amniotic shunt tube preserve normal bladder function?

Development and in-vitro characterization of a novel fetal vesicoamniotic shunt - the Vortex Shunt

OBJECTIVES

To develop and test a novel vesicoamniotic shunt (VAS) to treat fetal lower urinary tract obstruction (LUTO), decrease dislodgement and optimize shunt deployment in-vitro.

METHODS

VAS design objectives included: 1) robust and atraumatic fixation elements, 2) kink resistant conduit to adjust to fetal movement and growth, 3) one-way pressure valve to facilitate bladder cycling, and 4) echogenic deployment visualization aids. The force to dislodge the novel Vortex shunt was compared with existing commercially available shunts in a bench-top porcine bladder model. Sonographic echogenicity was evaluated with ultrasound-guided deployment, and the shunt valve pressure measured.

RESULTS

A prototype novel Vortex shunt was developed using braided nitinol "umbrella-type" ends with a kink-resistant stem incorporating an internal one-way valve. The peak force required to dislodge the Vortex shunt was significantly higher than commercially available shunts (p<0.01). Shunt deployment in the bench-top model was easily confirmed with ultrasound guidance and the brisk decompression of the inflated porcine bladder thereafter. In-vitro valve gauge pressure testing mirrored bladder pressures in human LUTO cases.

CONCLUSION

In-vitro testing shows that the Vortex shunt may improve deployment, sonographic visualization, kink resistance, and dynamic size adjustment. Validation in preclinical animal models are warranted and currently underway. This article is protected by copyright. All rights reserved.

Fetal bladder outlet obstruction: Embryopathology, in utero intervention and outcome

Fetal bladder outlet obstruction (BOO), most commonly caused by posterior urethral valves (PUV), remains a challenging and multi-faceted condition. Evolving techniques, and refinement in ultrasound, optics and instrumentation, have increased our rate of prenatal diagnosis, and enabled valve ablation not only in smaller newborns, but also in fetuses. Long-term outcome studies have raised our awareness of the silent damage caused by bladder dysfunction and polyuria and encouraged their proactive management. In spite of our best efforts, the proportion of boys with PUV who progress to chronic and end-stage renal disease (ESRD) has not changed in the last 25 years. Evidence suggests a reduction in perinatal mortality following prenatal intervention, probably resulting from amelioration of oligohydramnios at the crucial time of lung development between 16 and 28 weeks' gestation, but no improvement in postnatal renal outcome. There are no bladder functional outcome studies in patients who have undergone prenatal intervention and hence the long-term effect of in utero defunctionalisation of the bladder is not known. This aim of this review is to revisit the embryopathology of fetal BOO, in particular the renal and bladder structural and functional changes that occur with in utero obstruction. The effect of earlier prenatal diagnosis, and therapy, on postnatal outcome is also explored and compared with outcomes published for traditional postnatal treatment.

Pressure limited vesico-amniotic shunt allows normal lung growth in a fetal lamb model of obstructive uropathy

BACKGROUND

In our fetal lamb model of lower urinary tract obstruction, a pressure limited shunt preserves bladder function and renal development. This study investigates the effects on pulmonary histology.

METHODS

We created obstructive uropathy (OU) in 60-day gestation fetal lambs, ligating the urethra and urachus, and delivering them at term (130-145days). We compared pulmonary histology in 4 groups: group A, OU without shunt; group B, pressure limited shunt; group C, non-valved shunt. Shunts were inserted 3weeks post-obstruction. Group D were normal controls.

RESULTS

We compared 27 fetuses: 7 fetuses in group A, 4 fetuses in group B, 2 fetuses in group C, and 14 fetuses in group D. There was no significant difference in lung volume in any group. In group A, there were some areas of atelectasis and incomplete alveolar formation histologically. The alveoli in group A lambs lungs had a predominance of type II cells, whereas group B lambs lungs were lined by type I epithelial cells and were essentially indistinguishable from controls.

CONCLUSIONS

This study suggests that using a pressure-limited vesico-amniotic shunt in OU may preserve the renal tract and the lungs.

Can a pressure-limited V-A shunt for obstructive uropathy really protect the kidney?

BACKGROUND

In our fetal lamb model of lower urinary tract obstruction, a valved shunt preserves bladder function. This study investigates the effects on renal histology.

METHODS

We created obstructive uropathy (OU) in 60-day gestation fetal lambs, ligating the urethra and urachus, and delivering them at term (130-145days). We compared renal histology in 4 groups: group A-OU without shunt, group B-low-pressure shunt (15-54mmH2O), group C-high-pressure shunt (95-150mmH2O). Shunts were inserted 3weeks post-obstruction. Group D were normal controls.

RESULTS

We delivered 32 fetuses from 23 ewes: 13 fetuses in group A (9 survived), 6 fetuses in group B (5 survived), 7 fetuses in group C (5 survived), and 6 fetuses in group D. Histologically, we found renal tubular distention, vacuolated degeneration of tubular epithelial cells in 7 lambs, and cyst formation in 4 lambs in group A. There was renal tubular distention in two lambs, and cyst formation in one lamb in both groups B and C, with vacuolated degeneration of tubular epithelial cells observed in all but 1 lamb in each group.

CONCLUSIONS

V-A shunting prevents multicystic dysplastic kidney (MCDK). Some lambs have renal tubular distention and vacuolated degeneration of renal tubular epithelial cells.

Development of an animal model to study congenital urinary obstruction

PURPOSE

We outline the development of a reliable model of obstructive uropathy in fetal lambs highlighting our understanding of the critical time points for interventions and the variability of any such model. We identify some discoveries that may have clinical implications.

METHODS

The model requires 60-day-gestation fetal lambs. In lambs, glomerulogenesis is complete by 90 days gestation. (Term is 145 days.) The ability to develop a reliable method of creating bladder outlet obstruction in females, ligating both the urethra and urachus was critical. The lambs are bred to an accuracy of ±24 h.

RESULTS

Creating the model at 50-60 days gestation, produces different expressions of renal dysplasia in groups of lambs undergoing identical interventions at the same stage of gestation. Early complete urethral obstruction can produce the Potter phenotype. An appropriately timed vesico-amniotic shunt preserves renal development, producing a shrunken, non-compliant bladder. Shunting the normal fetal bladder at 80 days gestation produces a similar bladder. Provision of a low-pressure valve in the shunt preserves bladder development and compliance. Using a high-pressure shunt produces results similar to non-shunted lambs.

DISCUSSION

We developed a reliable animal model for obstructive uropathy. Being alert to peripheral results can lead to new findings.

Valved shunt as a treatment for obstructive uropathy: does pressure make a difference?

PURPOSE

A valved ventriculo-peritoneal shunt (V-P shunt) as a vesico-amniotic shunt (V-A shunt) preserves the filling/emptying cycle and normal bladder development in fetal lambs with bladder outlet obstruction. The optimal pressure for such shunts is unknown.

MATERIALS AND METHODS

We created obstructive uropathy in 60-day gestation fetal lambs. A V-A shunt was placed 3 weeks later, using a low-pressure (Group L: 15-54 mmH2O) or a high-pressure (Group H: 95-150 mmH2O) V-P shunt. We included non-shunted (obstructive uropathy, Group O) and control lambs (Group C). All were delivered at 130 days. Bladder volumes, bladder thickness, renal and bladder histology were compared.

RESULTS

Seventeen lambs had an obstructive uropathy created. Five Group L (four survived), four Group H (three survived) and five Group O survived. Body weight and crown-to-rump lengths of the three groups were not significantly different. Group H lambs had a dilated urachus, urinary ascites and severe ureteral dilatation similar to Group O lambs. There were four Group C lambs. Bladder volume was 10, 15 and 1,150 ml in Group H, 115 ± 67.9 ml in Group L, 128 ± 99.8 ml in Group O and 24.5 ± 3.84 ml in Group C. Unlike Group O lambs, Group L did not have urinary ascites, urinomas or renal dysplasia.

CONCLUSION

Low-pressure shunts preserved both bladder volume and renal development. High-pressure shunts did neither.

Adult male health risks associated with congenital abnormalities

Congenital abnormalities of the genitourinary system have a definable durable impact on the adult lives of those individuals affected, despite prompt and appropriate surgical and medical intervention during infancy and childhood. Three abnormalities are described, including relatively common problems of the newborn male, such as hypospadias and cryptorchidism, as well as a less common issue, posterior urethral valves. An understanding and awareness of the consequences of these 3 congenital abnormalities is paramount for the long-term care of the pediatric patient as he transitions to adolescence and adulthood.

Effectiveness of fetal cystoscopy as a diagnostic and therapeutic intervention for lower urinary tract obstruction: a systematic review

OBJECTIVE

To determine the effectiveness of fetal cystoscopy in the prenatal diagnosis of and intervention for congenital lower urinary tract obstruction.

METHODS

This study was a literature search using MEDLINE, Embase, Cochrane Library, MEDION, Web of Science reference lists and contact with experts. All studies reporting on fetal cystoscopy in lower urinary tract obstruction with data for a 2 × 2 table were selected for review. No language restrictions were applied. There was independent selection of studies, data extraction and quality assessment by two reviewers. Peto odds ratios were calculated as a summary measure of effect.

RESULTS

A total of 2071 citations were identified and 66 papers selected for detailed evaluation, from which four papers with a total of 63 patients were selected for inclusion. Two papers had results for the use of cystoscopy in diagnosis, showing that fetal cystoscopy altered the ultrasound diagnosis of the underlying pathology in 36.4 and 25.0% of fetuses, respectively. Compared to no treatment, fetal cystoscopic intervention demonstrated an odds ratio for improved perinatal survival of 20.51 (95% CI, 3.87-108.69). However, comparing vesicoamniotic shunt (VAS) with fetal cystoscopy there appeared to be no significant improvement in the perinatal survival odds ratio of 1.49 (95% CI, 0.13-16.97). These results had wide CIs and for cystoscopy vs. VAS, all results crossed the line of no effect.

CONCLUSION

There is little published evidence for the effectiveness of therapeutic fetal cystoscopy as an intervention for congenital lower urinary tract obstruction and the quality of this evidence is poor. It should thus be considered to be an 'experimental intervention' and subjected to further investigation.

Fetal surgery for severe lower urinary tract obstruction

Fetal interventions have been proposed for treatment of severe lower urinary tract obstruction (LUTO), as this condition is associated with high rates of perinatal mortality and postnatal renal impairment. The rationale for in utero treatment for those cases is based on the possibility of relieving the obstruction, improving the amniotic fluid volume, and preventing renal and bladder damage. Candidates for fetal intervention should be rigorously selected based on the confirmation of severe LUTO (dilated bladder and bilateral hydronephrosis), oligohydramnios or anyhydramnios and 'favorable' fetal urinalysis (dependent on gestational age). Nowadays there are two different therapeutic options with specific technical approaches. Vesico-amniotic shunting is an easier procedure, but with a higher frequency of related complications. Fetal cystoscopy can be used for diagnostic purpose and for treatment of posterior urethral valves, with suggestive advantage of allowing a more physiological release of the obstruction. According to the literature, estimated survival rates and postnatal normal renal function frequencies are approximately 40 and 50% after vesico-amniotic shunting and 75 and 65% after fetal cystoscopy, respectively.

Bladder development following bladder outlet obstruction in fetal lambs: optimal timing of fetal therapy

BACKGROUND

Lower urinary tract obstruction causes both renal failure and bladder dysfunction after birth. This study examined the early bladder wall changes after creating an obstructive uropathy focusing on bladder wall thickness and muscle integrity.

METHODS

We created obstructive uropathy in fetal lambs at 60 days' gestation, ligating the urethra and urachus. The fetuses (n = 28) were delivered at 48 hours and 3, 4, 5, 7, and 14 days after obstruction and at term (145 days' gestation). Sham-operated lambs were used as controls (n = 20). Histology samples were stained using α-smooth muscle actin) immunohistochemistry and also hematoxylin-eosin, Masson trichrome, and colloidal Fe stain.

RESULTS

The bladder wall initially expanded and stretched. By day 4, the bladder wall became thicker. Histologically, the bladder in obstructed lambs demonstrated a prominent submucosal fibrotic change by 7 days. The mean bladder wall thickness at 14 days after obstruction was thicker than controls, and fibrosis was prominent.

CONCLUSION

The initial changes in the bladder wall were expansion of the muscle component followed by fibrosis. The bladder wall thickness dramatically increased 4 to 7 days after obstruction. We conclude that shunting operations to preserve bladder function may be needed earlier than expected.