The clinical term rectovaginal (urethral) fistula is a chronic inflammatory fistula that forms between the rectum and the vagina or urethra from various causes, except for tumor-infiltrating leaks or acute phase leaks due to trauma or surgery. Treatment is based on surgical repair, but there are numerous surgical procedures and a high failure rate. Pinto reported 125 patients with rectovaginal fistulas, with an overall success rate of about 60%. Especially for the so-called complex fistulas with low tissue healing ability after local radiotherapy, severe local scarring after trauma or surgery, fistulas due to Crohn’s disease and multiple repair failures, surgical repair is particularly difficult and the recurrence rate is high, which brings serious impact on patients’ lives and becomes one of the difficult surgical problems. In recent years, we have treated 19 cases of these complex fistulas with good results by using a femoral muscle flap with vascular nerve tip to isolate the rectum from the vagina (urethra). Rectovaginal (urethral) fistulas are not uncommon clinically, and their incidence is increasing year by year both at home and abroad, but the distribution of causes of fistulas varies greatly. In Western countries, about 45% of adult female rectovaginal fistulas are caused by inflammatory bowel disease, 24% by birth injury, and 16% by pelvic surgery; the vast majority of adult male rectovaginal fistulas are due to medical causes, including 67% after radical prostatectomy, about 14% from radiation therapy, 11% from other causes including low rectal cancer surgery, and 8% from prostate electrosurgery. In China, more than 90% of the causes of rectovaginal (urethral) fistula in adults are of medical origin, and inflammatory bowel disease is relatively rare, which is basically consistent with the situation in this paper (17/19). It is noteworthy that the incidence of complex fistulas caused by pelvic tumor surgery ± perioperative local radiotherapy, especially anal preservation after neoadjuvant radiotherapy for low rectal cancer, has been increasing in recent years, both at home and abroad, accounting for 47% in this paper (9/19). It is complicated because of the severe pathological changes in the local tissue structure, manifested by large fistula defects, heavy scarring, low tissue viability, and poor blood supply, which make surgical repair extremely difficult. In the last 20 years, surgical techniques for rectovaginal (urethral) fistulas have progressed rapidly, abandoning the previous method of direct suturing after fistula excision, which had a very low success rate, and have been updated in two main ways: first, the layer-to-layer method of advancement flap; second, the interposition of autograft flap or biological flap. The autograft flap or biomaterial isolates the rectum from the vagina (urethra) and serves as a mucosal healing matrix (bed) to improve local tissue blood supply and enhance resistance to infection and healing. Regardless of the surgical access (perineal, anal, vaginal, abdominal or sacrococcygeal, etc.), the success rate of one-time repair is basically about 90% with acceptable complication rates, with the exception of Crohn’s disease and complex fistulas, provided that the indications are properly selected. Because the results of prospective controlled studies are lacking for each procedure and are limited to empirical, small sample analyses, the clinical outcomes reported in the literature vary widely. Although there are differing opinions, experts from several medical centers with a large number of cases recommend a reasonable choice of surgical approach based on their experience: for simple fistulas, a less invasive layered repair with a nudge flap is recommended, with no fecal-urinary diversion, whereas for complex or recurrent fistulas, an isolated repair with an autologous tissue flap graft ± fecal-urinary diversion is recommended. Isolation with biomaterials is still in the experimental observation phase and is not widely accepted. Autologous tissues with vascular tissues are often selected, such as the bulbocavernosus muscle, gluteus maximus muscle, femoralis muscle and greater omentum, each with its own advantages, disadvantages and indications. The bulbocavernosus muscle is easy to retrieve, but because it is small and short, it is generally used only for isolated repair of simple fistulas that are low in location and small in diameter. The greater omentum is mostly used in the transabdominal route, but in some patients the omentum is missing due to multiple surgeries. The gluteus maximus is also easier to harvest, but the gluteus maximus flap does not have a well-defined single vascular bundle, which sometimes results in distal ischemia of the flap and may have some impact on limb function after excision. In contrast, the thin femoral muscle is relatively free, has a single vascular nerve bundle, and the muscle is thicker, so there is no significant effect on limb function after excision, which is especially suitable for complex fistulas with high and large defects, but the harvesting is not convenient, the position needs to be changed intraoperatively, and once the vascular bundle is damaged, the whole muscle will be ischemic and necrotic. All 19 cases of particularly complex fistulas in our group used the thin femoral muscle, but one patient failed the repair after surgery because of muscle ischemic necrosis, and four cases presented with mild numbness and pain in the leg, which could be relieved in about six months. Because the muscle flap with blood supply or large omental tissue has a strong resistance to infection, the tissue filling increases the thickness of the rectovaginal (urethral) septum, which acts as an isolator and enhances the healing ability of the local tissue. Therefore, the success rate of using autologous tissue is high in patients with recurrent fistulae or after local radiotherapy and severe scarring of the surrounding area. In our group, the one-time repair success rate reached 94.7%, which is much higher than the first success rate of 53 cases reported by Wexner. The main reason may be that 11 (20.75%) of the 53 fistulas in Wexner were Crohn’s disease fistulas, and the 10 (19%) patients who developed local infection after surgery were only passively drained and did not actively perform continuous flushing. In contrast, there were no fistulas due to Crohn’s disease in this group, and the 5 patients (26%) who developed local infections were cured by timely continuous flushing with double cannulae. The success rate of first-time repair of fistulas due to inflammatory bowel disease, regardless of the method used, is low, generally ranging from 30% to 50%. A review of the domestic and international literature also revealed that the success rate of repair reported in China is mostly higher than in Europe and the United States, probably because the incidence of Crohn’s disease is much lower in the East than in Europe and the United States, and the chance of fistula is also lower than in the West. The main immediate postoperative complications in our patients were local infection (5/19, 26%) and delayed closure of the fistula due to urine leakage (5/9, 55.6%). Among the distant complications, complete closure of the rectovaginal fistula took more than 6 months in 2 cases, a small amount of postoperative leakage of urine occurred in the rectourethral fistula, which healed about 2 months after surgery, and urethral stricture occurred after removal of the urethra in about 44% (4/9), especially at the anterior-posterior urethral junction. Therefore, for complex rectovaginal (urethral) fistulas, where the local tissues are poorly resistant to infection and healing, we believe that fecal diversion is still necessary to improve the success rate, and once local signs of infection are detected, early and timely continuous irrigation should be performed. In addition, the time to judge the success of the repair should be observed for about 1 year after surgery if it is confirmed that the transferred muscle flap is still between the fistula and not displaced, and patients with delayed fistula closure should not be rushed into a second operation or judged to have failed repair because the healing ability of the tissue varies greatly from person to person. Of course, if the muscle flap is found to have shifted and has not closed for more than 6 months, there is little point in extending the observation period. To avoid displacement of the muscle flap, special attention is paid to three points intraoperatively: first, the plane of separation must be more than 2 villagers above the fistula; second, the top space of the rectovaginal (urethral) gap must be sufficient to accommodate the muscle flap, often we have to see the normal fatty tissue in the gap on both sides of the vagina when separating it and fixing it firmly with non-absorbable sutures; third, adequate drainage must be provided so that no dead space is left, and we often use thicker latex drainage tubes to facilitate placement of this channel after infection. facilitate the placement of double cannulae in this channel after infection. In our experience, it is not critical to have good sutures for rectal and vaginal (urethral) fistulas, as long as the aging scar tissue at the edge of the fistula is removed and the healthy mucosa with good blood supply is properly sutured with absorbable thread to reduce the diameter of the fistula. Because fistulas with severe scarring, even if they are well sutured at the time, will partially dehiscence after a few days, the mucosal defect will crawl along the stroma and close completely as long as there is a healthy muscle flap. Repair of a rectovaginal (urethral) fistula by transferring the thin femoral muscle is more invasive than the method of pushing the flap with layered sutures and takes a relatively long time to operate, so strict indications are required. We do not recommend this highly invasive procedure for patients with simple fistulas in general, who have not received radiotherapy, have minimal surrounding scarring, and have small fistula defects. In the rare patients with very large fistulas, such as total destruction of the entire rectovaginal compartment, bladder triangle and posterior urethra, none of the local repair options are suitable and only rectal resection, coloanal anastomosis or permanent colostomy is an option. In patients with total destruction of the posterior urethra and bladder triangle, if the urethral sphincter is normal, the posterior urethra can be reconstructed via the abdomen with a bladder mucosal flap. If the urethral sphincter is absent, complete urinary incontinence or scarring of the urethra prevents recanalization, the only option is to perform ileal cyst diversion. Patients with rectovaginal fistula often present with gas or liquid stool or foul-smelling discharge from the vagina, recurrent vaginitis or even vaginal bleeding; patients with rectourethral fistula often present with urine or semen from the anus, and the urethra often discharges gas and fecal urine, leading to chronic urethritis and a poor quality of life for the patient. The simplest treatment is a permanent enterostomy or suprapubic cystostomy, but it poses a great psychological and social obstacle to the patient. The prospective quality of life scores of the 18 patients who were successfully repaired in this group showed that the rectal fistula cure greatly improved the quality of life and feelings of the patients, especially in younger patients, and also improved the quality of sexual life. Therefore, the choice of this procedure brings more benefits to patients than the disadvantages of surgical risks and complications and is worthy of clinical promotion.