New advances in the pathophysiologic and radiologic basis of the exstrophy spectrum

New Insights on the Basic Science of Bladder Exstrophy-epispadias Complex

The exstrophy-epispadias complex is a rare congenital anomaly presenting as a wide spectrum of disorders. The complex nature of this malformation leads to continuous investigations of the basic science concepts behind it. Elucidating these concepts allows one to fully understand the mechanisms behind the disease in order to improve diagnosis, management, and treatment ultimately leading to improvement in patient quality of life. Multiple technological advancements within the last 10 years have been made allowing for new studies to be conducted. Herein, the authors conduct a literature review of studies from 2009 to 2019, considering novel theories regarding the genetics, embryology, bladder, bony pelvis, prostate, and genitalia of patients with bladder exstrophy-epispadias complex.

Variants in ALX4 and their association with genitourinary defects

BACKGROUND

Genitourinary anomalies occur in approximately 1% of humans, but in most cases, the cause is unknown. Aristaless-like homeobox 4 (ALX4) is an important homeodomain transcription factor. ALX4 mutations in humans and mouse have been associated with craniofacial defects and genitourinary anomalies such as cryptorchidism and epispadias.

OBJECTIVES

To investigate the presence and the functional impact of ALX4 variants in patients with genitourinary defects.

MATERIALS AND METHODS

Two separate patient cohorts were analyzed. One includes clinical exome-sequencing (ES) data from 7500 individuals. The other includes 52 ALX4 Sanger-sequenced individuals with bladder exstrophy-epispadias complex (BEEC). Dual luciferase assays were conducted to investigate the functional transcriptional impact of ALX4 variants in HeLa cells and HEK293 cells.

RESULTS

A total of 41 distinct ALX4 heterozygous missense variants were identified in the ES cohort with 15 variants present as recurrent in multiple patients. p.G369E and p.L373F were the only two present in individuals with genitourinary defects. A p.L373F heterozygous variant was also identified in one of the 52 individuals in the BEEC cohort. p.L373F and p.G369E were tested in vitro as both are considered damaging by MutationTaster, although only p.G369E was considered damaging by PolyPhen-2. p.L373F did not alter transcriptional activity in HeLa and HEK293 cells. p.G369E caused a significant 3.4- and 1.8-fold decrease in transcriptional activities relative to wild-type ALX4 in HEK293 and HeLa cells, respectively.

DISCUSSION AND CONCLUSIONS

Our study supports the idea that transcription factors like ALX4 could influence the normal development of the GU tract in humans as demonstrated in mouse models as ALX4 variant p.G369E (predicted pathogenic by multiple databases) affects ALX4 function in vitro. Variant p.L373F (predicted pathogenic by only MutationTaster) did not affect ALX4 function in vitro. Exon-sequence information and mouse genetics provide important insights into the complex mechanisms driving genitourinary defects allowing the association of transcriptional defects with congenital disorders.

Continence in the cloacal exstrophy patient: What does it cost?

BACKGROUND

Surgical advancements have made cloacal exstrophy (CE) a survivable condition, though management remains complex. Urologic, orthopedic, colorectal and gynecologic interventions are not standardized, and the cost of this care is high. While the importance of a successful primary closure in terms of outcomes is known, the economic consequences of failure remain uncharacterized.

METHODS

A prospectively maintained institutional database of epispadias-exstrophy complex patients was reviewed for continent CE patients. Hospital charges for all inpatient admissions prior to achieving urinary continence were inflation-adjusted to year 2013 values using Consumer Price Index for medical care published by the United States Bureau of Labor Statistics. Records for which charge data were incomplete were completed by using single mean imputation, also inflation-adjusted. Descriptive data are presented as mean±standard deviation (SD).

RESULTS

Of 102 CE patients, 35 had available hospital charge data: 15 who underwent successful primary closure at the authors' institution and 20 who presented after previously failed primary closures at referring institutions. The mean±SD hospital charges for primary closure in the success group were $136,201±$48,920. These patients then underwent subsequent additional surgeries that accrued charges of $59,549±$25,189 in order to achieve continence. Overall, successful primary closures accumulated hospital charges of $200,366±$40,071. In comparison, patients referred after prior failure required significantly more hospital admissions and additional charges of $207,674±$65,820 were required to achieve continence (p<0.001). Patients who failed primary closure are estimated to accumulate 70% more total health care charges compared to the group following successful primary closure.

CONCLUSION

The cost of CE management until urinary continence is high, averaging more than $200,000 in inpatient hospital charges alone. Initial success is desirable from both an outcomes and economic perspective, as the cost of salvaging a failed primary closure at our institution is similar to the overall costs of a successful closure; this is in addition to the cost of any previous failed closures. Further studies will be required to determine the optimal timing of surgical management in terms of both patient outcomes and financial consequences.

Newborn exstrophy closure without osteotomy: Is there a role?

INTRODUCTION

Recent articles document successful classic bladder exstrophy (CBE) closure without osteotomy. Still, many patients require osteotomy if they have a large bladder template and pubic diastasis, or non-malleable pelvis.

OBJECTIVE

To understand the indications and outcomes of bladder closure with and without pelvic osteotomy in patients younger than 1 month of age.

METHODS

An institutional database of 1217 exstrophy-epispadias patients was reviewed for CBE patients closed at the authors' institution within the first month of life. Patient demographics, closure history, pubic diastasis distance, bladder capacity, and outcomes were recorded and compared using chi-square tests between osteotomy and non-osteotomy patients. Failure was defined as bladder dehiscence, prolapse, vesicocutaneous fistula, or bladder outlet obstruction requiring reoperation. Bladder capacity >100 mL was deemed sufficient for bladder neck reconstruction (BNR).

RESULTS

One hundred CBE patients were included for analysis: 38 closed with osteotomy (26 male, 12 female), and 62 closed without osteotomy (42 male, 20 female). There were four failed closures in the osteotomy group (2 dehiscence, 2 prolapse) and four failed closures in the non-osteotomy group (2 dehiscence, 2 prolapse). This corresponded to statistically equivalent rates of failure between the osteotomy and non-osteotomy groups (10.5% vs. 6.5%, p = 0.466). There was no statistically significant difference between the groups' ability to achieve bladder capacity sufficient for BNR (82% vs. 71%, p = 0.234).

DISCUSSION

A successful primary bladder closure, regardless of the use of osteotomy, has been shown to be the single most important predictor of eventual continence. Because of the complexity of exstrophy manifestations, a multidisciplinary team approach is of the utmost importance. Based on our institutional experience, closure without osteotomy is considered when patients are <72 h of life, have a pubic diastasis <4 cm, malleable pelvis, and pubic apposition without difficulty. Rates of successful closure and attaining sufficient capacity for BNR were both statistically equivalent across groups. This retrospective study is limited by selection bias and the significant difference in follow-up time between groups. Nevertheless, as a high-volume exstrophy center this study draws from one of the largest cohorts available.

CONCLUSIONS

Regardless of the type of closure undertaken, there clearly is a role for newborn CBE closure without pelvic osteotomy in patients considered suitable for closure by both the pediatric urologist and orthopedic consultant. However, if there is any doubt concerning pubic diastasis width, pelvic malleability, or ease of pubic apposition, an osteotomy is highly recommended.