As of now, there have been few studies that reported the treatment measures which can obviously improve the LARS. It is currently believed that the mechanism of LARS is primarily related to injury to the associated muscles and nerves of the pelvic floor, changes in the volume, pressure, and compliance of the reconstructed rectum, changes in intestinal dynamics, foreign body effects, and radiotherapy. In this study, we introduced a productive way using a greater omental pedicle flap to full fill post-rectal space vacancy after conventional Dixon-TME, in order to improve LARS in 11 patients. The primary outcomes and feedbacks were positive and uplifting.
The main reasons for the development of LARS after anal preservation in low rectal cancer are believed to include the following. On the one hand, the large rectal ampulla is removed together with rectal cancer, and the colon intestinal segment is displaced downwards and anastomosed with the rectal stump or anal canal, thereby restoring intestinal continuity following resection of the rectum. However, the residual rectum is very short, which changes the normal physiology of the anorectum and results in the loss of the rectal anal inhibitory reflex (RAIR). In most cases, RAIR is partially restored at 12 months after the operation with the regeneration of autonomic nerves in the wall at the anastomotic scar (10, 11). However, the direction of peristalsis of the reconstructed rectum, the perception of feces and adjustments in distention, and the volume are very different from those of the original rectum (12). Studies have found that (13) the maximum tolerable rectal capacity after anterior rectal resection is 77 ± 28 mL, which is significantly less than the normal level before the operation. The decrease in the maximum tolerable volume detected by postoperative defecography and anorectal manometry of the reconstructed rectum confirmed the changes in volume and the frequency of bowel movement in the reconstructed rectum. On the other hand, the sharp separation between the presacral space and the visceral and parietal layers of the pelvic fascia during TME inevitably damages the pelvic nerve plexus branches, blood vessels, and lymphatic tissues in the mesorectum, resulting in rectal and anal dysfunction (14, 15). The nerve conduction function of the middle and inferior plexus of the rectum is impaired, which affects the function of the anal sphincter, resulting in a significant decrease in anal resting pressure(16, 17). However, we have performed preoperative CT examinations and intraoperative explorations at our center for many patients with severe long-term LARS that requires secondary surgery and found that their reconstructed rectum and presacral and pelvic organs have severe adhesions and intestinal stiffness (Figure 4). Thus, we speculate that there is no surrounding mesorectum after TME that resembles the surrounding colon that is moved down to replace the rectum, resulting in direct adhesion of the reconstructed rectum to the presacral tissue, causing the reconstructed rectum to lose peristalsis, distention, and elasticity (18, 19), resulting in decreased compliance and capacity tolerance in the reconstructed rectum. Over time (usually 6-12 months), the reconstructed rectum will gradually compensate by expanding, and anorectal function and compliance will improve, but not to preoperative levels (20, 21). A study by Bittorf et al. (22) found that rectal compliance of 1.4±1.2 mL/mmHg at 2 years after anterior rectal resection also fully proves this point. Therefore, some researchers believe that restoring the volume and compliance of the reconstructed rectum is conducive to improving the short-term anorectal function of patients with low anterior resection. Clinical researchers have used colon J- pouches or transverse coloplasty pouches to increase the capacity of the reconstructed rectum, but their efficacy is not significant (23, 24). Preoperative neoadjuvant chemoradiotherapy causes pelvic tissue fibrosis (25) and damage to the nerve plexus of the pelvic floor, which stiffens the intestinal canal, further reduces peristalsis, worsens postoperative LARS symptoms, prolongs the time for the recovery of anorectal function, and increases complications (26, 27).
Therefore, we filled the presacral space with a greater omental pedicle flap to reconstruct a new mesorectum so that the reconstructed rectum has a mesenteric structure embedded in fatty tissue, which resembles the normal anatomical structure, thereby maintaining rectal compliance. Postoperative follow-up and evaluation using the LARS questionnaire (28) also confirmed that the operation reduced symptoms of LARS with significant efficacy, rapidly improving the symptoms to near-normal levels in a short period of time. The procedure is simple, does not significantly increase the time and difficulty of operation, has no significant complications, and is suitable for broad application. In one patient, due to poor healing of the anastomosis (nearly 1/2 cycle) in the intestinal canal after the operation, the transplanted omentum may experience limited inflammation, thereby promoting healing. However, due to the small number of cases, long-term observation is still necessary. Even more importantly, the patient’s anal function quickly returned to normal after the operation, whereas low rectal cancer patients with anastomotic leakage in the past have experienced a series of symptoms such as increased defecation frequency, urgency, difficulty in defecation, and incontinence due to pelvic inflammation, from which recovery is difficult. Other studies have found that the particular biological characteristics of the greater omentum can be used to treat brain injuries, hand trauma, and other defects, and has the ability to repair nerve tissue and promote regeneration (6, 29, 30). Research on whether the omental pedicle flap reconstruction of the mesorectum in the present study has similar restoration of neurological function as to accelerate the recovery of anal function is still lacking.
Greater omental pedicle flap transplantation for filling the presacral space and reconstructing the mesorectum can significantly improve LARS after Dixon-TME in patients with low rectal cancer. The flap comes from the body itself and the material is natural. The surgical procedure is simple and does not significantly increase the time and difficulty of operation. There are no significant complications associated with omental transplantation. Therefore, we believe that this is a promising technique warranting application. However, the number of cases treated with this technique is still small. After further studies with larger sample sizes, we expect it to become a standard surgical procedure for prevention of LARS after Dixon-TME for low rectal cancer, drive the development of functional organ surgery, and have a positive impact on tissue and organ function restoration and other complex problems.