The most significant factor in fistula formation is an associated wound infection. The oral cavity, pharynx, and larynx are clean contaminated surgical sites, exposed not only to saliva, but also to tracheal, pulmonary, and regurgitant gastric secretions. Kirchner at al.4 have shown bacterial counts in saliva of irradiated subjects to be as high as 105/ml. Others have shown decreased fistula rates when dental prophylaxis precedes tumor resection. As shown by Weber et al.,5 wound infection rates are 30 to 80% without antibiotic prophylaxis and decrease to about 5 to 30% with appropriate antibiotic administration. Modern surgical techniques and preoperative administration of prophylactic antibiotics have been critical factors in preventing wound infections and fistula formation in head and neck surgery.
Gastroesophageal reflux has been identified as an important factor in many inflammatory and neoplastic disorders of the aerodigestive tract. Although no definitive studies have shown a correlation between reflux and fistulization, Seikaly and Park6 showed a decreased rate of fistulae formation in patients treated with a postoperative antireflux regimen. We routinely maintain intravenous H2 blocking agents until gastric feeding can be started via tube feeds.
The effect of preoperative radiation therapy on fistula formation remains controversial. Studies reported by Dedo et al.,7 Mendelsohn et al.8 and others report that preoperative radiation predisposes to fistula formation by damaging tissue, decreasing vascular perfusion, and delaying healing. However, other studies, including Thawley9 and, more recently, Fradis et al.10 and Soylu et al.,11 concluded that radiation does not correlate with the likelihood of fistulization. Studies of patients undergoing brachytherapy show wound complication rates ranging from 10% to 50% in patients undergoing either brachytherapy as part of their initial cancer treatment or combined surgery-brachytherapy for salvage. In our experience, prior full-course radiotherapy (>5000 cGy) and brachytherapy have a detrimental effect on wound healing and are considered risk factors for compromised healing and fistulization. As a general practice, a trial of oral intake that might routinely take place on postoperative day 7 is deferred until postoperative day 10 in the previously irradiated or implanted patient.
Another well-established cause of fistula formation is tight wound closure that places undue tension on the suture line. Advanced T3 and T4 tumors have a higher incidence of fistula formation, due primarily to the added resection of the pharyngeal wall and consequent tighter closure. Similarly, pharyngocutaneous fistulae are more common with total laryngectomy or partial laryngopharyngectomy than with supraglottic resection due to extension of the resection to include the pyriform area. Although the extent of oncologic resection is not within the reconstructive surgeon's control, reconstructive efforts should strive to minimize tight closure. If the pharyngeal closure is tight enough to impair the outflow of the swallowed bolus, saliva will follow the path of least resistance and may leak through the suture line during swallowing. Similarly, distal anastomotic stricture in gastric pullup may lead to outflow resistance and cause backup of secretions. The problem of tense closure can be managed by recruiting additional tissue for closure of the pharyngeal mucosa over a nasogastric tube. As shown by Horowitz and Sasaki,11 upper esophageal sphincter myotomy at total laryngectomy significantly decreases peak pharyngeal pressures, minimizing proximal fistulization through the suture line. Clayman and Weber12 report a 20% fistula rate with gastric pullup reconstruction of circumferential hypopharyngeal defects, with a rate of only 2% with free jejunal transfer—a difference they attribute to decreased tension of closure with free jejunal transfer giving less concern about tethering. At our institution, laryn-gopharyngoesophagectomy with gastric transposition is more commonly performed than free jejunal transfer, with a fistulization rate of 3%.
The last local predisposing factor in the development of pharyngocutaneous fistula is residual gross or microscopic tumor at the surgical site or resection margins. Residual tumor disrupts the healing process, leads to wound infection, and results in early dehiscence and fistula formation. Fistulae that occur within 1 to 2 weeks postoperatively frequently reflect problems relating to systemic and local factors in wound healing. Those occurring about 2 to 3 weeks postoperatively may also be due to these same factors, however, persistent cancer should also be considered, particularly if the fistula persists despite appropriate management.
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