EA is one of the most dangerous diseases in paediatric surgery. Improvements in surgical techniques and postoperative care have greatly improved the survival rate for EA.5 Despite esophageal anastomosis, infants still inevitably face severe infection and even death caused by anastomotic fistula. In the past, most of these patients were successfully treated conservatively with observation, drainage and the use of antibiotics. In 1990, MacKinnon, describing his experience with EA infants, found that the anastomotic fistula rate was 21% and first proposed that EA anastomotic fistula was directly related to anastomotic tension.6 Anastomotic fistula is a serious complication after EA, which can lead to serious chest infection and even the possibility of refractory stenosis.7 Anastomotic fistula is the most important early complication. Possible factors associated with its onset include poor anastomotic technique, the use of woven sutures, two-layer anastomosis, long-gap EA, blood transfusion, anastomosis under tension and gastroesophageal reflux.8 Factors associated with mortality included delayed diagnosis, premature birth, low birth weight and CHD. In the Spitz Classification, patients with a birth weight of more than 1.5 kg are classified as a low-risk group; however, it is still possible to be classified as a group with high mortality and poor prognosis in the Waterston classification because of severe congenital malformations.9 In our study, the incidence of anastomotic fistula was 23.4%. We found that some long-gap infants with a low birth weight were faced with anastomotic difficulties or even delayed anastomosis, which brought more anastomotic fistulas. We tried to find more reliable evaluation indexes to predict the occurrence of anastomotic fistula. Very-low-birth-weight infants are a high-risk preoperative group. Survival is directly related to birth weight and CHD. Infants weighing over 1500g and with no major cardiac problems should have a near 100% survival, whereas the presence of one risk factor reduces survival to 80%, and survival is further reduced to 30–50% in the presence of both risk factors.10 Folaranmi compared infants with very low birth weight (< 1.5 kg), low birth weight (1.5–2.5 kg) and normal weight (> 2.5 kg). The results showed that the probability of esophageal anastomosis increased significantly with increasing body weight. Logistic regression analysis showed that birth weight was a significant variable associated with the probability of primary esophageal anastomosis (OR = 1.009, P = 0.004).11 A study from Turkey also reported a significantly higher incidence of anastomotic fistula in very-low-birth-weight infants compared with cases in the low- and normal-birth-weight groups.12 There was a significant correlation between birth weight and prognosis, but the relationship between anastomotic fistula and birth weight has not been confirmed.
We found that the birth weight of the anastomotic fistula group was lower than that of the non-anastomotic fistula group (2.61 ± 0.58 vs. 2.91 ± 0.47, P = 0.023). Nine of seventeen infants with CHD weighed less than 2.5 kg. To some extent, birth weight reflects the developmental level of infants. Low birth weight is often associated with a history of premature delivery, fetal distress and heart malformation.13 Low birth weight may be associated with poorer peripheral circulation and lower cardiac output, which may lead to a poor blood supply at the local anastomotic site.14
On the other hand, the esophageal gap length is one of the important factors in the preoperative evaluation of surgical difficulty in infants. The treatment of long-gap EA is still a serious problem.15 There is an increased risk of anastomotic leakage in long-gap EA. It usually requires extensive mobilisation of the esophageal stump, which may impair the vascular supply to the esophagus and thus impair the healing ability of the anastomotic site.16 In addition, anastomotic tension may lead to a reduction of the esophageal blood supply. Surgeons should carefully anastomose under low tension to prevent anastomotic complications during the initial repair of EA/TEF.17 In this study, the average defect length was 1.52 ± 0.95 cm, 1.98 ± 1.08 cm in the anastomotic fistula group and 1.33 ± 0.82 cm in the non-anastomotic fistula group, and the difference was statistically significant. Long-gap is an independent risk factor for anastomotic fistula. Serious anastomotic fistula was found in 6 of the 8 patients with long-gap EA. We believe that delayed anastomosis of a long segment defect may be a better choice, especially for infants with a gap length > 3 cm (intraoperative or preoperative), and the timing of anastomosis should be carefully determined.
Preoperative low albumin may result in postoperative anastomotic edema, which increased the anastomotic tension, preoperative albumin in anastomotic fistula group was obviously lower than non-anastomotic fistula, but in multiple factors analysis, albumin levels were not included in the regression equation, it may be related to this research in the number of cases of low albumin (albumin < 28 g/L) is less. The sample size should be further expanded to find a more appropriate Cut-off value to evaluate the relationship between albumin level and anastomotic fistula.
Logistic regression analysis showed that birth weight and defect length were important correlative factors of postoperative anastomotic fistula. With increasing birth weight, the risk of anastomotic fistula was significantly reduced. The larger the defect length, the higher the probability of anastomotic fistula. Therefore, we boldly proposed a new indicator, the ratio of gap length to birth weight. The ratio in the anastomotic fistula group was significantly higher than that in the non-anastomotic fistula group (0.71 ± 0.49 vs. 0.47 ± 0.32, P = 0.012). Using the receiver operating curve, the AUC of this indicator was found to be 0.732, which had a good predictive value. We believe the index can be used as a good predictor of anastomotic fistula during the perioperative period. For infants with a preoperative evaluation of the ratio of loss length to birth weight greater than 0.7 cm, esophageal extension and gastrostomy should be considered. The anastomosis can be attempted after the natural extension of the esophagus in the chest reaches a gap length of less than 3 cm, and delayed repair may be a better choice.18
As with any retrospective study, there is bias associated with data collection, this study was limited to one institution and other institutions may come up with different results. A prospective study with a large group of patients and long-term follow-up is necessary.