Variation in surgical management of neurogenic bowel among centers participating in National Spina Bifida Patient Registry

1. Introduction

Spina bifida (SB) without anencephaly is the most common non-chromosomal central nervous system defect, occurring in approximately 3/10,000 live births [1, 2]. Neurogenic bowel dysfunction is the norm in patients with SB and negatively impacts quality of life [3, 4]. Many individuals with SB undergo procedures to manage neurogenic bowel, such as creation of a continent stoma, an incontinent colostomy, or percutaneous cecostomy tube (Chait) placement.

In previous analyses, our group has noted significant variation in the use of urological surgeries for management of neurogenic bladder in individuals with SB [5]. A recent analysis of national data revealed that privately insured patients were more likely to undergo continent bladder augmentation instead of incontinent urinary diversion [6] The underlying clinical reasons behind this variation are not clear. To the best of our knowledge, no studies have yet examined whether similar variation exists for neurogenic bowel procedures.

The primary objective of this study is, therefore, to describe current patterns of care among NSBPR clinics. We hypothesized that significant variation exists among NSBPR clinics in the use of neurogenic bowel procedures. Our exploratory, secondary aim was to identify factors that may influence such variation.

2. Patients and methods

3. Results

4. Discussion

In this national, multicenter study, we demonstrate an association between neurogenic bowel surgery and SB-related factors such as bladder surgery, mobility status and lesion type/level. In addition, non-SB-related factors such as patient age, gender, race and treating center were also associated with the likelihood of undergoing neurogenic bowel procedures.

This last association suggests the presence of significant variation in the use of procedures to manage neurogenic bowel among NSBPR clinics. The overall intervention rate across all clinics was 19%. At some clinics, however, only 3% of patients underwent neurogenic bowel procedures; at other clinics, up to 38% of patients did. This variation remained significant even after correcting for clinical and non-clinical factors.

Surgical management of neurogenic bowel has evolved significantly over the past several decades. Historically, incontinent diversions such as colostomy or ileostomy were the only means available to those who failed non-operative measures. In 1990, Malone et al. reported initial results with appendicocecostomy, also known as the ACE procedure, to allow antegrade enemas [12]. This procedure has been reported to have continence rates of 90% or better with low complication rates [12, 13, 14, 15]. For patients without an appendix, who are not good surgical candidates, or who do not desire intraabdominal surgery, a cecostomy tube can be placed percutaneously to also allow antegrade enemas to achieve colonic evacuation. Among patients enrolled in the NSBPR, continent ACE or cecostomy tube procedures are performed $>$ 6-fold as commonly as incontinent diversions. This is reflective of national trends towards increased usage of continent rather than incontinent procedures among SB patients [6, 13]. Perhaps unsurprisingly, bladder surgery (concurrent or prior) was associated with continent bowel procedures being performed. The drop-off in the frequency of these procedures in the oldest group of patients is likely explained by the fact that these continent procedures did not exist when these patients were younger. Likewise, adult patients may not have desired surgical interventions.

In a previous analysis, Sawin and colleagues analyzed continence rates among the first 10 clinics to participate in the NSBPR; they found that only 30% of SB patients reported themselves as being continent of stool [7]. However, this analysis did not examine whether patients undergoing ACE or colostomy procedures were more or less likely to identify themselves as “continent” compared to patients receiving medical management alone or no management. Given recent advances with cone enemas or the Peristeen ® anal irrigation system, this is clearly an area that merits further study [16]. In terms of establishment of applicable standards of care, future analysis will need to focus on the outcomes of all interventions, specifically whether specific interventions or specific clinics with higher surgical rates have higher continence rates. The NSBPR has been recently modified to allow better quantification and qualification of fecal incontinence episodes, so more granular data may be available in coming years.

In our analysis, we found that patients undergoing ACE or cecostomy tube procedures were more likely to be younger (predominantly aged 10–21 years), to be white, to be non-ambulatory, to undergo concurrent bladder reconstruction, and to have been treated at certain NSBPR clinics. Compared to incontinent procedures and to medically managed constipation, these procedures have been reported to significantly increase satisfaction and quality of life measures among SB patients [17, 18]. Therefore, it is not surprising ACE/cecostomy procedures were much more fre- quently performed than incontinent procedures. Similarly, fecal stream diversion procedures such as colostomy may be performed as a component of management of posterior pelvis pressure ulcers that may be more common in adults who are heavier or possibly ambulate less. Interestingly, we noted relatively high odds of ileostomy or colostomy among non-MMC patients. While the exact reason for this finding is unclear, we suspect that our results are influenced by the presence of non-MMC patients with other co-morbid diagnoses such as cloacal exstrophy or anorectal malformations.

As these studies highlight, the decisions to proceed with surgical management of neurogenic bowel issues in SB patients are complex and involve many aspects of patients’ medical condition. We noted a similar variation in surgical management rates of neurogenic bladder among NSBPR clinics [19], and the pattern is also apparent in the choice of procedure since ACE/cecostomy procedures are commonly performed with bladder reconstruction. Importantly, those decisions also seem to include consideration of other non-medical aspects of each SB patient.

Given the complexity of surgical decision-making in this population, it is perhaps unsurprising that some variation should exist among clinics caring for individuals with SB. Variation is likely a reflection, in part, of surgeon philosophy. Surgical variation may be further influenced by the population, social situation and the level of support and resources available at home and in the local environment. These factors are not necessarily reflected by the demographic or socioeconomic data available in the NSBPR. Another contributing factor could be allocation of limited resources (e.g., surgeon time) and possible lower reimbursement potential for longer reconstructive cases, particularly given high rates of public insurance coverage among these patients.

Regardless of the root causes, this degree of variation is intriguing as it implies either overuse or underuse of these procedures; such variation can be problematic [20, 21, 22, 23]. A high degree of variation in the use of these procedures is of interest to clinicians, researchers, and policy makers alike, as such variation implies that there is not an obvious or widely accepted standard of care for the management of neurogenic bowel, including surgical management. Further, such variation typically implies either overuse or underuse of these procedures, either of which may be a significant problem in medically complex patients. Overuse of neurogenic bowel procedures is of concern due to the significant potential morbidity and expense of surgery; underuse is problematic because constipation and fecal incontinence can have a detrimental impact on patients’ quality of life and may predispose to other health concerns.

Our results suggest that the hospital at which the individual is treated plays a role in surgical decision-making along with clinical factors such as age, race, mobility status, and lesion level. Given the significant social and financial costs of neurogenic bowel procedures, this level of variation suggests that further research is needed to help clinicians and patients make appropriate and less arbitrary choices regarding surgery.

The findings of our study must be interpreted in the context of study limitations. The NSBPR continues to undergo improvements and modifications to ensure the validity of its data. Whereas clear definitions are provided for the functional outcomes that we have analyzed, these are still potentially subject to variation in their interpretation and reporting by different individuals at different clinics. This raises particular caveats when attempting to compare outcomes from different clinics. As with any large database, it is also possible that there are errors in data acquisition and input. However, previous NSBPR studies have shown that these errors should be infrequent [8].

Selection bias may be a threat to external validity. NSBPR is clinic-based, so it may not represent SB patients who do not attend SB clinics. It is also possible that the clinics participating in the registry are not representative of SB clinics in general. No attempt was made to ensure representativeness in choosing NSBPR clinics; indeed, the fact that all NSBPR clinics are multidisciplinary may limit generalizability of our findings. Nevertheless, we believe the NSBPR probably characterizes the majority of SB clinics in the United States. In addition, selection bias may be a threat to internal validity: participating clinics enrolled most but not all eligible patients, raising concerns that those who are eligible but not contributing data may be different from those who are. In an attempt to evaluate the possible impact of this bias, we conducted a rigorous selection bias analysis (Table 5) based on the best available literature on this topic. Importantly, we did not see a significant difference in outcomes before and after these adjustments, implying that selection bias may not play a significant role in our findings.

5. Conclusions

There is significant variation in neurogenic bowel procedure rates among NSBPR clinics. In addition to SB-related factors such as bladder surgery, mobility status and lesion type/level, non-SB-related factors such as patient age, gender, race/ethnicity and treating center are also associated with the likelihood of undergoing neurogenic bowel procedures.