The indications of using prophylactic NPWT are broad. Two review articles from the Cochrane Library mentioned that patients who underwent primary closure of their surgical wound and treated prophylactically with NPWT following surgery experience fewer SSI than those treated with standard dressings.26,27 NPWT is commonly used to treat open wounds in the abdomen in combination with lavage, debridement, and bowel resection as indicated.28 However, existing evidence on the effectiveness of NPWT on postoperative perineal wounds in both APR and ELAPE cases remains uncertain. In our study, APR was performed in all studies, whereas ELAPE was performed in two out of eight studies. Our meta-analysis demonstrated significant reduction in SSI rate and LOS in patients receiving NPWT after APR or ELAPE. This is the first meta-analysis with a TSA on specific surgical interventions for abdominoperineal resection.
Negative pressure with different settings was applied in the included articles. In two studies (Kaneko et al.23 and Chadi et al.20), although the NPWT duration differed (Kaneko et al. was 5 days and Chadi et al. was 7 days), both applied a pressure of 125 mmHg. In another study conducted by van der Valk et al.19, the NPWT duration was the same as that of Chadi et al.’s study, but the pressure applied was only 80 mmHg. However, in van der Valk et al.’ s study, there was no difference in the rate of SSI reduction between the experimental and control groups. In Chadi et al.’s study, which applied a pressure of 125 mmHg, there was a significant reduction in the SSI rate. Hence, in these three studies, we could find a brief conclusive result, suggesting that the main control parameter is the pressure, not the NPWT duration. In the other three studies, they applied negative pressure using a ball that cannot be quantified specifically. Besides, the duration of NPWT was not mentioned in these studies either. However, the rate of SSI reduction was still significant in three studies.
Besides, it is well recognized that a significant proportion of patients with CD and ulcerative colitis ultimately require surgical interventions. Among patients with inflammatory bowel disease (IBD), the perioperative management including the use of immunosuppressants, biologic agents, and corticosteroids might increase the risk of SSI.29 No study has indicated that either APR or ELAPE with NPWT was effective for IBD. In most of the patients in our studies, including rectal cancer-related articles, only three out of eight articles (Kaneko et al., Chadi et al., and Rather et al.) analyzed patients diagnosed with IBD. However, several studies indicated that the risk of postoperative infectious complications, including superficial SSI, deep space infections, and anastomotic leakage, is much higher in IBD patients.
In CD patients, Toh et al. who followed up Australian patients with CD indicate that the overall risk of surgery and the risk of major abdominal surgery have reduced in recent decades, whereas the risk of perianal surgery had increased.30 The surgical intervention, performed with APR, in CD is useful for cases with isolated, severe perianal diseases that is refractory to fecal diversion alone. Nevertheless, the disadvantage may be delayed perineal wound healing. The consensus guideline of the Taiwan Society of IBD also mentioned that surgery is indicated for patients with severe and complicated CD who fail to respond to medical treatment or have worsening symptoms.31 In patients who are candidates for surgery, early surgery is preferred, as prolonged immunosuppressive treatment may increase the risk of surgical complications, such as sepsis and impaired healing. In addition, early surgery has been associated with a reduced risk of clinical recurrence, as compared to surgery performed late in the course of CD. Consequently, in patients who had received immunosuppressive therapy before undergoing a surgical intervention, NPWT may be more effective in improving the postoperative infectious complication rate.
Compared with APR, more radical surgical approaches, such as ELAPE, have better results, as reported in some studies. ELAPE could more effectively achieve free margins and avoid intra-operative tumor perforation. Stelzner et al. suggested that ELAPE results in superior oncologic outcome as compared to standard techniques. The rates of bowel perforation and circumferential resection margin involvement for ELAPE, as compared to APR, were significantly reduced.32 Besides, the technical difficulty associated with operating deep in the pelvis through an abdominal approach during conventional APE could be overcame by extended perineal dissection in the prone jack-knife position in ELAPE, thereby removing the anal canal, levators, and low mesorectum altogether.33 Because of more radical surgical approaches, compared ELAPE to APR, the wound management would be committed to the postoperative care. Thus, effective NPWT should be performed; our study demonstrated the effectiveness of NPWT for patients who have had ELAPE.
Although the LOS in the experimental group is significantly shorter than that of the control group, the high hospitalization cost is still a problem for the patient. Considering the cost-effectiveness of NPWT, this treatment is performed using expensive equipment and facility.
The limitation of our study is that the negative pressure applied in all included studies is not consistent. Meanwhile, the facilities that created negative pressure are not the same as well. Hence, a prospective study or a randomized controlled trial utilizing specific pressures, duration, and facilities is warranted to obtain statistically significant results.