Radiotelemetered urodynamics of obstructed ovine fetal bladders: correlations with ex vivo cystometry and renal histopathology

Pressure-volume analysis of rat's micturition cycles in vivo

AIMS

Though the pressure-volume analysis (PVA), a method based on thermodynamics, is broadly used for assaying cardiac functions, its potential application on the physiology/pathophysiology of the urinary bladder, which processes resemble thermodynamic cycles to the heart, has not been established.

METHODS

Cystometry recording intravesical pressure (IVP) and intravesical volume (IVV) of rhythmic voiding contractions caused by a constant saline infusion (0.04 mL/min) were carried out in forty urethane-anesthetized female Sprague-Dawley rats, and the PVA was established by plotting IVP against IVV.

RESULTS

Pressure-volume points shaped coincident enclosed loops, and loop-associated urodynamic parameters kept stable under a constant infusion rate (0.04 mL/min). Enhancing preload (by elevating infusion rates to 0.08 and 0.12 mL/min) increased the area enclosed by the loop (Apv) and shifted loops to the right and slightly upward. Augmenting afterload (by enhancing resistances using 1/4 and 1/2 urethra clamping) increased Apv and shifted loops markedly to the right and upward. Without affecting Apv, muscarine (0.01 and 0.1 mM)-induced inotropic states shifted loop to the left and upward that was as opposed to the atropine (0.01 and 0.1 mM)-induced anti-inotropic state.

CONCLUSIONS

Not only consistently assayed baseline bladder functions, PVA but also validly measured modified bladder functions due to altered extrinsic environment and intrinsic contractility of the bladder itself. In accompanied by cystometry, PVA could provide a clear concept about the relationship between time, pressure, and volume in the voiding activity.

Rare Variants in BNC2 Are Implicated in Autosomal-Dominant Congenital Lower Urinary-Tract Obstruction

Congenital lower urinary-tract obstruction (LUTO) is caused by anatomical blockage of the bladder outflow tract or by functional impairment of urinary voiding. About three out of 10,000 pregnancies are affected. Although several monogenic causes of functional obstruction have been defined, it is unknown whether congenital LUTO caused by anatomical blockage has a monogenic cause. Exome sequencing in a family with four affected individuals with anatomical blockage of the urethra identified a rare nonsense variant (c.2557C>T [p.Arg853^∗]) in BNC2, encoding basonuclin 2, tracking with LUTO over three generations. Re-sequencing BNC2 in 697 individuals with LUTO revealed three further independent missense variants in three unrelated families. In human and mouse embryogenesis, basonuclin 2 was detected in lower urinary-tract rudiments. In zebrafish embryos, bnc2 was expressed in the pronephric duct and cloaca, analogs of the mammalian lower urinary tract. Experimental knockdown of Bnc2 in zebrafish caused pronephric-outlet obstruction and cloacal dilatation, phenocopying human congenital LUTO. Collectively, these results support the conclusion that variants in BNC2 are strongly implicated in LUTO etiology as a result of anatomical blockage.

Current strategies to predict and manage sequelae of posterior urethral valves in children

Posterior urethral valves (PUV) constitute a significant urological cause of chronic kidney disease (CKD) in children. The condition is characterised by the unique pathophysiology of the evolution of bladder dysfunction after relief of obstruction, which contributes to CKD. Improvements in prenatal diagnosis followed by selective foetal intervention have not yet produced improvement in long-term renal outcomes, although better patient selection may alter this in the future. Proactive management with surveillance, pharmacotherapy, timed voiding, double voiding, and/or assisted bladder-emptying, is being increasingly offered to those with severe bladder dysfunction and has the potential of reducing the burden of renal disease. Clinicians are currently able to counsel regarding the prognosis using serum creatinine and other emerging markers. However, much of this work remains to be validated. Satisfactory graft survival rates are now reported with aggressive management of bladder dysfunction in children who are candidates for renal transplantation. Knowledge gaps exist in identifying early markers of renal injury, risk stratification, and in understanding patient and carer perspectives in PUV.

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.

From gene discovery to new biological mechanisms: heparanases and congenital urinary bladder disease

We present a scientific investigation into the pathogenesis of a urinary bladder disease. The disease in question is called urofacial syndrome (UFS), a congenital condition inherited in an autosomal recessive manner. UFS features incomplete urinary bladder emptying and vesicoureteric reflux, with a high risk of recurrent urosepsis and end-stage renal disease. The story starts from a human genomic perspective, then proceeds through experiments that seek to determine the roles of the implicated molecules in embryonic frogs and newborn mice. A future aim would be to use such biological knowledge to intelligently choose novel therapies for UFS. We focus on heparanase proteins and the peripheral nervous system, molecules and tissues that appear to be key players in the pathogenesis of UFS and therefore must also be critical for functional differentiation of healthy bladders. These considerations allow the envisioning of novel biological treatments, although the potential difficulties of targeting the developing bladder in vivo should not be underestimated.

CONGENITAL URINARY BLADDER OUTLET OBSTRUCTION

The term congenital ‘bladder outlet obstruction (BOO)’ describes the collection of conditions in which the normal, urethral egress of urine from the fetal bladder is impaired. The term is interchangeable with fetal ‘lower urinary tract obstruction’, as used by other authors. After considering normal urinary tract embryology, we describe the epidemiology of congenital BOO and the primary anatomical disorders associated with it. We then proceed to describe its fetal and postnatal clinical manifestations and then consider therapies and interventions which have been used to manage the condition. We not only focus on urethral and bladder disease with constitutes BOO itself, but also describe associated kidney disorders which, via chronic renal excretory failure, are important causes of morbidity. Rather than provide an exhaustive review, we emphasise studies published in the last decade, and therefore readers are referred to other reviews citing numerous earlier references.