: Systematic Review A systematic literature review on the use of vacuum assisted closure for enterocutaneous fistula

Discussion
This systematic review has demonstrated that there is limited evidence, exclusively from a few level IV studies, that VAC therapy has been used with some success to treat patients with ECF. The estimated median closure rate using VAC therapy of 64.6% within 58 (12-90) days is encouraging but is comparable to the 50% spontaneous closure reported recently in the literature (4). It is therefore debatable at the moment whether the theoretical benefits of VAC therapy accelerates or contributes to the closure of ECF or whether the fistula would close spontaneously with conservative measures. Nevertheless, VAC may have a use as a temporary preoperative measure protecting the skin and improving the patient’s nutritional status ahead of more definitive therapy.
Studies investigating factors affecting closure using VAC have identified several important considerations. D’Hondt et al showed a statistically significant beneficial effect on closure rates in the absence of visible intestinal mucosa at the site of the fistula (p=0.0015). (23) Gunn et al reinforced this observation; 11 patients without visible mucosa achieved VAC-assisted ECF closure, whereas all four patients with visible mucosa did not. (24) They suggested that the reason might be that visible intestinal mucosa suggests epithelialisation at the mucocutaneous junction, which if present would mean that no conservative therapy can achieve closure.
The results of this review also showed that success of VAC depends on the output of the fistula. The higher the output, the less likely it was to close, with the proportion of fistulae closing halving from 85.7% in the low output group to 42.1% in the high output group. This observation is reinforced by D’Hondt et al, who showed that an output of <500mL/day is significantly associated with a higher closure rate using VAC (p=0.0147) (23). It is, however, worth mentioning that a high output fistula is generally accepted to be a negative predictor of closure with conservative and surgical therapy, regardless of the use of a VAC device. (4)
Streimitzer et al used Octreotide for a median of 5 (2-9) days in the initial stage of treatment to help establish fistula control with the VAC method. The authors believe that its success is independent of the use of Octreotide, but Octreotide may be initially helpful in gaining control of the fistula and reducing its output. (22) Somatostatin was used in the high output cases in one study, but its effect is not commented on. In this study no high output fistula closed, regardless of the use of Somatostatin. (23)
Several studies have also identified additional benefits relating to the use of VAC in patients with ECF. One of the most important immediate benefits is the ability to contain the effluent, protect the skin around the fistula and to prevent further tissue breakdown and improve dermatitis. (18, 21) One of the studies specifically mentioned that 7-15 days after the start of VAC therapy the wound was noted to be clean, dry and granulating (25).
Another study showed that in 89 (97.8%) of 91 cases oral or enteral feeding could be reintroduced within a mean of 3.4 days without significant increase in the fistula output. The same study also showed that 69% of 84 patients treated with VAC regained mobility within 20 days of starting treatment (21). Unfortunately no specific comparison with conservative therapy could be found.
While a former cost analysis was not done in any of the studies, it would be reasonable to assume that VAC treatment, whether as a definitive measure or as a pre-operative one, could be more cost-effective than conservative treatment and/or surgery, due to the reduced use of medical treatment such as Octreotide, expensive surgical measures, and the possibility of outpatient care, especially for low output fistulae. (21, 24)
There is little information on the possible adverse effects of VAC. A recent paper suggested that when further fistulation occurs, mortality after formation of the secondary fistula increases and if so VAC treatment for ECF may increase overall mortality. (26) The authors acknowledged, however, that the number of patients in the study was too small to allow this to be firmly established. (26) A UK national prospective study of 578 patients found that VAC use for open abdominal wounds was not associated with an incidence of fistulation through the wound (relative risk = 0.83, 95% confidence interval: 0.44-1.58). Indeed in a paired matched cohort of 187 pairs, VAC therapy showed an absolute reduction of risk of 1.6% compared with other methods of wound care. (27) NICE guidance agrees with these results and does not warn of an increased rate of fistulation with VAC therapy. Whether fistulation occurs more often with VAC in certain conditions such as sepsis or wound dehiscence is unclear and there is therefore no specific guidance to avoid the use of VAC in these situations. (15) In another study, 40% of patients experienced short term pain due to the treatment and 14 out of 59 patients at long term follow-up encountered the complication of abdominal wall disruption, while one patient had a significant distal obstruction (20). It is, however worth mentioning that it is unclear whether or not these long term effects were secondary to the use of VAC treatment. Recurrence of ECF after VAC is yet to be compared to the reported 21% recurrence rate after surgery alone. (28)
Clearly the reviewed studies, while informative, have a number of gross limitations that prevent them from being used as strong evidence in favour of VAC of ECF. All but one contained small numbers of 15 or less. All were of evidence level IV, and retrospective case series or single case studies. Some of the included studies did contain greater numbers which were split into groups depending on what specific ECF treatment they received, but statistical comparisons within these groups were not demonstrated and, perhaps more importantly, there was no control group. Some studies also used other medical treatment, such as octreotide, somatostatin or TPN which rendered the data non-comparable. Further studies investigating the roles of these nutritional aids would be valuable. The studies are also characterised by heterogeneity, as all but one of the patients in all 10 studies developed the fistula following surgery. Many of the studies also lack a number of specific details and do not show individual parameters in the case series, making it difficult to estimate the relevance of some results.
Despite the limited evidence, available the literature suggests, nevertheless, that VAC therapy may be used safely to treat patients with ECF resulting from surgery either as a definitive tool to achieve closure or as a bridge to definitive surgery. Due to the scarcity and heterogeneity of available literature on the subject, further retrospective and prospective studies are required to assess its true role and to identify patients that may benefit the most.