Congenital esophageal stenosis (CES) is a common esophageal benign disease in infants and young children with the incidence rate of about 1/25000-1/50000 live births. It can be classified into three types according to the results of postoperative pathological examination: tracheobronchial remnant (TBR), fibromuscular hypertrophy (FMH), and membranous diaphragm (MD). By means of upper gastrointestinal angiography and gastroscopy, it is easy to identify and treat MD or esophageal fistula, while preoperative diagnosis of TNR and FMH is indistinguishable, which need to be identified by surgical resection and postoperative pathology [2, 3].
The age of the visit and the time of the diagnosis varied depending on the severity of the stenosis and consciousness of parents. Most of the cases didn’t visit the hospital until electrolyte disorder occurred, although the symptoms emerged, and unfortunately ignored, when changing the diet structure (such as adding complementary food) . One of the children in this group was after the operation of esophageal atresia. During the operation, it had been found that the 8th gastric tube could not reach the stomach through the distal esophagus, and the 6th gastric tube could. Thus, the esophageal atresia was ignored, and the lower esophageal stenosis was confirmed by angiography 8 months later. From the results of the upper gastrointestinal contrast, it can be found that the location of the early esophageal stenosis was relatively high, closer to the middle part of the esophagus, and the location of the late esophageal stenosis was found to be lower, closer to the cardia. Similarly, in terms of the proximal extension, it was not found in the cases of early esophageal stenosis, but significant dilation among late cases not only in diameter of reaching more than 30 mm, but also the whole esophagus shape changing into "C" type. These suggest that esophageal stenosis is a continuous process. It is inaccurate to judge the nature of the stenosis by simply relying on upper gastrointestinal contrast and gastroscope to find the position of esophageal stenosis. It has been reported that endoscopic ultrasonography can accurately and clearly show the hierarchical structure and extra-wall conditions of the digestive tract wall, as well as determine the origin, extent, size and nature of the submucosal lesions, which was of guiding significant for further treatment .
In order to ensure a clear diagnosis before surgery, and to avoid the trauma and postoperative complications of surgery performed through the sterile surgical area (thoracic, abdominal cavity), we used common gastroscopic and endoscopic ultrasonography to distinguish the nature of esophageal stenosis and tried to use endoscopic treatment instead of surgical resection. First, we tried to pass the narrow section using electronic gastroscope EG-600WR. When the gastroscope entered the lower part of esophagus, it can be seen that the distribution of esophageal mucosa and vascular network in the place of stenosis was normal. The narrow mouth of the esophagus remains naturally closed. Although the gastroscope with a front end 9 mm or more in diameter can not enter the stomach through the narrow ring, the naturally closed narrow mouth can be peristalsis with or without cervix-like bulge, and can be slightly opened after gas injection and the distal end of esophagus or cardiac orifice can be seen from the narrow hole. This confirms that the stenosis has nothing to do with the cardia, nor is it caused by acid reflux. Second, we used endoscopic ultrasonography to observe the 5-layer structure of the esophageal wall . Normal adult esophageal thickness is about 3mm . We performed ultrasonography on 5 children in this group and found that the muscular layer of the stenotic segment was significantly thickened, and the thickness of the intrinsic muscular layer could reach 3 mm. The thicker the muscle layer, the more obvious the esophageal stenosis. And the thickened intrinsic muscle layer itself had stratification with the thick inner layer and the thin outer one.
In the past, most of the esophageal stenosis that failed to pass or expand by the gastroscope was surgically resected. The surgical methods were either thoracoscopic or laparoscopic alone or combined . However, most of them must pass through the sterile area (thoracic or abdominal cavity), and there are some postoperative complications, such as anastomotic stenosis, gastroesophageal reflux, diaphragmatic eventeration  and so on. In recent years, there have been reports of endoscopic treatment of lower esophageal stenosis through natural passages [9, 10], which avoid some postoperative complications and shorten the hospital stay. We also tried endoscopic treatment instead of surgical resection based on ultrasound results. Endoscopic balloon dilatation is preferred. The principle of balloon dilation is that the inflated balloon gives a constant, central axis pressure to the stenosis, causing partial tearing of the stenotic muscle layer for expansion . In the first 3 cases, the target diameter of esophageal dilation was determined to be 11mm according to the report , and the total expansion was 4-5 times/person. But the effects were still unsatisfactory. With the accumulation of experience, our target diameter was set to 12-15mm, and the effects were obvious when expanded only 1-2 times/person. It has been reported that the endoscopic expansion target of adults was 15mm , but the stenosis of children was designed starts to be expanded from 3-5mm. There would be mucosal, submucosal and muscular damage before reaching to 15mm. Practically we added the pressure gradually, and for each time to increase the pressure value, damages around the stenosis would be observed and evaluated. The results showed that, when the endoscope with a diameter of 9mm or more could pass through the narrow mouth, there would be ineluctable damage to the mucosa, submucosa and part of the muscle layer of the wall. But the surface of damage, if without perforation, was with no need for special treatment, for it was reported that the residue of the anastomotic nail could stimulate the local fibrosis . As the wound ends naturally, the damaged mucosal layer could be naturally apposed and healed after a day or two postoperation. On the day after surgery, the case could be given the liquid food and an appropriate anti-inflammatory for 1-3 days, and could be discharged 1-2 days after surgery. The review examination one month later showed that the diet structure of the child was significantly improved. The 9mm gastroscope could pass through the previous narrow mouth, and the narrow mouth had been transformed from "O" to "C". The one-sided centripetal ring of the wall disappeared.
Endoscopic balloon dilatation for the treatment of congenital lower esophageal muscular hypertrophic stenosis in infants is a new minimally invasive surgical treatment, similar to endoscopic treatment of pyloric anterior and duodenal valves [13, 14]. However, with the auxiliary diagnosis of endoscopic ultrasonography, the wall structure is clearer, which enables us more confident in treatment.