Digestive tract malformations

　　Congenital gastrointestinal malformations are caused by developmental defects in the fetus during the early stage of embryogenesis due to various reasons. Clinically, they are mainly manifested as gastrointestinal obstruction, and the time and degree of symptom appearance are related to the height and severity of the lesion. The two major causes of neonatal gastrointestinal malformations are:

　　(1) Genetic factors

　　(2) Environmental factors

　　(2) Environmental factors: The two factors mentioned above, along with some unknown reasons, account for 65% of birth defects. Gastrointestinal malformations in neonates during the perinatal period are not uncommon. The formation of gastrointestinal malformations is most common during the 4-8 weeks of fetal development, due to various factors causing developmental disorders in the gastrointestinal tract. In addition to a few being local manifestations of chromosomal abnormality syndromes, most are affected by environmental factors, especially the effects of infectious factors in the early stage of embryogenesis. In addition, the influence of factors such as X-rays, microwaves, computers, televisions, lead, tobacco, alcohol, pesticides, and others should not be ignored.

　　In addition to general symptoms, gastrointestinal malformations can also cause other diseases. Depending on the location of the malformation, the complications caused are not the same. For example, esophageal atresia can cause aspiration pneumonia, and diaphragmatic hernia can cause respiratory distress and atelectasis.

　　Vomiting is a major symptom of gastrointestinal malformations and one of the most common clinical symptoms in pediatric and internal medicine outpatients. Due to the incomplete development of the nervous system in infants and young children, physical examinations are not cooperative, and there is no way to communicate through language, so they often seek medical attention with vomiting and crying. The first-time doctor has to judge whether it is functional vomiting or organic vomiting, whether it is internal medicine vomiting or surgical vomiting, which is quite challenging.

　　Generally, vomiting containing bile is mostly associated with surgical diseases. Vomiting resembling feces can basically be determined as a surgical disease. Bile-free vomiting can be either an internal medicine disease or a surgical disease, hence the difficulty in distinguishing between internal and surgical diseases in cases of bile-free vomiting. In terms of surgery, the diseases that commonly cause bile-free vomiting are mostly abnormalities in the upper gastrointestinal tract, such as esophageal atresia, gastroesophageal reflux, diaphragmatic hernia, gastric volvulus, hiatus hernia, pyloric stenosis, and others. These diseases often have no abdominal signs such as abdominal distension or pain, and even the abdominal X-ray film shows no obvious abnormalities, making it easy to confuse with internal medicine diseases. Diagnosis mainly relies on medical history and gastrointestinal imaging, so it is required that our medical workers ask detailed medical histories, carefully examine, and analyze meticulously. We must pay attention to both the universality and individual differences, so as to improve the diagnostic rate and reduce the rate of misdiagnosis.

　　A preliminary judgment of surgical diseases based on the nature, color, and degree of vomiting:

　　1. Non-biliary vomiting

　　Vomit is white gastric content. If the vomiting is not severe, it is often seen in functional vomiting, gastroesophageal reflux, gastric torsion, hiatal hernia, and other conditions. If the vomiting is severe and喷射状, it is often due to pyloric obstruction (such as congenital hypertrophic pyloric stenosis).

　　2. Biliary vomiting

　　Vomit with a yellowish green liquid, not thick, is often due to obstruction at the distal ampulla of the duodenum, such as malrotation of the intestines, duodenal stenosis, annular pancreas, superior mesenteric artery syndrome, and narrowing at the beginning of the jejunum.

　　3. Fecal vomiting

　　Vomit with a brownish yellow, thick consistency and an odor often indicates a lower intestinal obstruction, ileal atresia, congenital megacolon, and other conditions.

　　4. Bloody vomiting

　　Blood in vomit is often caused by bleeding from esophageal or gastric mucosal ulcers near the Treitz ligament. If hematemesis is accompanied by abdominal pain, distension, and muscle tension, it should be considered that there may be bowel torsion and necrosis, or strangulated intestinal obstruction.

　　Digestive tract malformations are congenital abnormalities that are difficult to prevent. They can be detected early, operated on early, and serious complications can be avoided. Congenital megacolon is caused by persistent spasm of the distal rectum or colon, with feces stagnating in the proximal colon, leading to thickening and expansion of the intestinal segment, which is a common congenital intestinal malformation in children.

　　Ultrasound examination of the fetal digestive tract can obtain important morphological and physiological activity information, and can discover digestive tract malformations early. How to correctly understand the sonographic features of the fetal digestive tract and identify whether the fetal digestive tract is 'abnormal' or 'normal' is a serious issue that ultrasound physicians need to face. Correct identification is of great significance for the clinical management of physicians. Early detection of digestive tract abnormalities can indicate certain fetal chromosomal abnormalities, and amniocentesis should be performed to check the chromosomes.

　　The size of the fetal stomach increases with the gestational weeks, and its size is affected by the amount of amniotic fluid swallowed and the emptying of the stomach. The incidence of esophageal atresia is 1 in 4000 to 1 in 3000, with an incidence of 1 in 4000 in China, occurring during the 3rd to 6th weeks of embryonic development. Ultrasound cannot directly display the atretic esophagus. When there is esophageal atresia in the fetus, ultrasound can show a small gastric bubble or no gastric bubble, with 80% accompanied by polyhydramnios, and the index ≥ 20cm. However, for fetuses with esophageal atresia and tracheoesophageal fistula, the gastric bubble may not be small, and it may be visible, so the possibility of esophageal atresia cannot be absolutely excluded. Due to the secretory function of the stomach itself, about 10% can show a small gastric bubble, and a small gastric bubble should also be considered as a sign of esophageal atresia with tracheoesophageal fistula. If the gastric bubble or small gastric bubble is not seen after repeated examinations, malformation of the digestive tract should be considered.

　　Duodenal obstruction is a special type of small bowel obstruction, which is manifested as a typical double bubble sign and usually appears after 24 weeks of gestation. Almost all patients with duodenal atresia have polyhydramnios. When the stomach shows a

　　Colonic atresia can manifest as colonic dilation. Whether the colon is dilated should be judged according to the gestational age at the time of examination. The normal fetal colon diameter is not more than 7mm within 25 weeks of gestation, and not more than 18mm at term. If the widest diameter is greater than 20mm, intestinal obstruction should be suspected. When anal atresia occurs, ultrasound often shows a

　　It is noteworthy that it is not possible to perform aetiological classification of fetal gastrointestinal abnormalities before birth. Fetal intestinal obstruction and gastrointestinal malformations are different concepts, and not all fetal intestinal obstructions are caused by gastrointestinal malformations. There are 2 cases in this group with tenacious feces blockage or other causes leading to transient fetal intestinal obstruction, bowel dilation, without obvious adverse perinatal outcomes, and the fetus defecates normally after birth. Therefore, correct clinical guidance should be given to patients with fetal intestinal obstruction found before birth.

　　Enhanced bowel echo and strong echo in the abdomen are related to intestinal obstruction.

　　If chromosomal abnormalities are merged, congenital infections and TORCH infections (cytomegalovirus, herpes simplex virus, Epstein-Barr virus, enterovirus) are related. Abdominal calcification with strong echo is related to meconium peritonitis. The bowel echo in this group is slightly stronger, and most fetuses show no abnormalities after birth follow-up.

　　In summary, ultrasound prenatal diagnosis of fetal gastrointestinal malformations has unique advantages, emphasizing dynamic observation and repeated examinations, which is of great significance for eugenics, optimal breeding, and early treatment after birth.

　　Gastrointestinal malformations are congenital abnormalities of the gastrointestinal tract and are unrelated to diet, but some gastrointestinal malformations cannot be fed, such as esophageal atresia, so the diet should be determined according to the location of the gastrointestinal malformation.

　　Congenital gastrointestinal malformations in neonates often manifest soon after birth, with symptoms mainly including vomiting, abdominal distension, dysfunction of defecation, and respiratory distress, which are similar to some pediatric diseases such as dyspepsia and pneumonia, and are prone to delayed diagnosis. Therefore, not only pediatric surgeons but also pediatricians and obstetricians must understand the clinical characteristics of this disease, achieve early diagnosis and timely treatment, and reduce the mortality rate of neonatal gastrointestinal malformations.

　　I. A disease mainly manifested by respiratory distress, coughing, and cyanosis

　　1. Congenital esophageal atresia

　　Mostly type III, that is, the proximal esophagus is a blind end and is accompanied by an esophageal tracheal fistula, which is a representative surgical disease that requires emergency treatment in the neonatal period. The mortality rate was high in the past, but with the development of perinatal medicine and neonatal surgery, the mortality rate has decreased year by year, and it has dropped below 10% in foreign countries, and the cure rate in China has reached about 70-90%. The key to success lies in early diagnosis. Since this disease often has a history of polyhydramnios or asphyxia after birth, all neonates have aspiration pneumonia, and the severity of pneumonia is an important factor affecting the prognosis. Any neonate who spits foam, dribbles saliva, and has coughing, shortness of breath, cyanosis, and respiratory distress after drinking water or breastfeeding, and whose symptoms improve after secretion from the oral cavity is aspirated, should be considered for this disease. Further, a nasogastric tube can be tried, and if the tube is obstructed or deflected from the mouth, it can be adjusted to the blind end, a chest X-ray can be taken, and iodine oil can be injected through the tube for造影确诊. After diagnosis, active preoperative preparation should be made for primary anastomosis surgery.

　　2. Thoracoabdominal hernia

　　This disease is characterized by a large defect in the diaphragm, with abdominal organs entering the thoracic cavity and accompanied by poor lung development, pulmonary hypertension, leading to death soon after birth due to respiratory distress and hypoxemia. In recent years, with the use of extracorporeal membrane oxygenation (ECMO) in foreign countries, the mortality rate has significantly decreased. Mild cases may experience shortness of breath or mild cyanosis during feeding or crying, but the symptoms can be relieved when the chest is elevated or the child is in a lateral position, and they are prone to pneumonia. X-ray透视 shows multiple light areas or lung bubble shadows in the thoracic cavity. Lung collapse and mediastinal displacement to the healthy side are observed. Barium meal X-ray can detect the entry of the stomach and intestines into the thoracic cavity, and treatment should include chest hernia reduction and diaphragm repair surgery.

　　3. Esophageal hiatus hernia

　　This disease occurs when part or all of the stomach enters the thoracic cavity through an enlarged esophageal hiatus. Most children溢奶或呕吐乳汁 after feeding, with severe cases vomiting brown or coffee-colored substances. The diagnosis is primarily confirmed by X-ray imaging, where the chest X-ray shows a shadow of the stomach bubble in the thoracic cavity, and further confirmed by barium meal X-ray. In severe cases, timely hernia reduction and esophageal hiatus hernia repair surgery should be performed. For mild cases, conservative treatment can be tried first, and if there is no improvement, surgical treatment can be considered.

　　2. Diseases mainly characterized by abdominal distension, vomiting, dyspnea, and cyanosis

　　1. Neonatal gastric perforation

　　The etiology is unclear and may be related to high neonatal gastric acid, increased intragastric pressure, and congenital defects in the development of the gastric wall. Perforations are often located on the anterior wall of the greater curvature of the stomach. The patient usually develops symptoms within 2 to 3 days after birth, with marked abdominal distension, varicose veins of the abdominal wall, limited diaphragmatic breathing, edema and redness of the abdominal wall, disappearance of the lung-hepatic junction, and weakened or absent bowel sounds. Due to abdominal distension, symptoms such as vomiting, dyspnea, and cyanosis may rapidly worsen, with toxic shock appearing within 1 to 2 days after the onset, with a mortality rate of over 50%. Abdominal puncture can withdraw a large amount of gas and gastric contents, and X-ray fluoroscopy can show free gas under the diaphragm. After diagnosis, emergency surgery should be performed promptly.

　　2. Fetal meconium peritonitis

　　Fetal meconium peritonitis refers to chemical aseptic peritonitis caused by the entry of meconium into the peritoneal cavity due to intestinal perforation during the embryonic period. It forms extensive adhesions around the intestines and is divided into peritonitis type and intestinal obstruction type according to the timing of intestinal closure. If the perforation does not close after birth, typical symptoms and signs of neonatal peritonitis appear within 1 to 2 days after birth. X-ray films can show characteristic calcification spots for diagnosis. If X-ray films or B-ultrasound examination is performed, calcification shadows can be found in the fetal period, and a diagnosis can be made before delivery. Treatment should be determined according to the pathological type, with emergency surgery for the peritonitis type, including perforation suture or peritoneal drainage, and conservative therapy or surgery for the intestinal obstruction type.

　　3. Diseases mainly characterized by frequent vomiting, with the vomit being milk (without bile)

　　Congenital hypertrophic pyloric stenosis accounts for the third place among digestive tract malformations. The disease usually manifests between 2 to 3 weeks after birth, primarily with immediate vomiting after feeding, followed by a strong desire to eat. The vomit does not contain bile and is喷射状. Clinical manifestations include malnutrition, weight loss, significant reduction in stool and urine output, and no weight gain. The upper abdomen shows a gastric type and peristaltic waves. A spindle-shaped cartilage-like mass can be palpated at the outer margin of the rectus muscle in the upper right abdomen. X-ray barium meal shows a narrow pyloric canal longer than 1 cm, and an arched impression can be seen in the pyloric antrum. After diagnosis, pyloromyotomy should be performed. Postoperative symptoms improve, and the long-term efficacy is satisfactory.

　　4. Diseases mainly characterized by vomiting, abdominal distension, and difficulty in defecation

　　1. High-position intestinal obstruction

　　The patient begins to show symptoms 3 to 5 days after birth, with the initial symptom being vomiting, the vomit being a yellow-green bile-like substance, with a small amount of meconium possibly excreted. The upper abdomen is visible as distended and showing intestinal loops, while the lower abdomen is flat. X-ray films show a double-bubble or triple-bubble sign, with less air in the lower abdominal intestinal cavity. If the above typical clinical manifestations are present, it indicates duodenal or proximal jejunum obstruction. The common causes include the following three: A. Congenital duodenal or jejunal atresia or stenosis; B. Congenital malrotation of the intestines; C. Ring pancreas. These three digestive tract malformations have similar clinical manifestations. Observation of the ileocecal position by barium enema suggests congenital malrotation of the intestines if the ileocecal junction is in the upper right abdomen. After diagnosis, surgical treatment should be performed.

　　2. Low intestinal obstruction

　　If there is abdominal distension and vomiting immediately after birth and no meconium is excreted, the following four diseases should be considered, namely congenital anorectal malformation, congenital megacolon, congenital anorectal malformation, congenital megacolon, congenital colonic atresia, and meconium constipation.

　　①Congenital anorectal malformation: This disease ranks first in gastrointestinal malformations, with complex lesions and pathological types. It not only includes anorectal atresia but also the absence of anal and external anal sphincter development, sacral malformation, and urinary tract malformation. It is divided into high, middle, and low types according to the position of the rectal blind end, and there are also those with rectourethral fistula and rectovaginal fistula. If the operation is not handled properly, it will cause serious defecation dysfunction such as fecal incontinence, which may affect the quality of life. Therefore, it is advisable to make an early diagnosis and choose appropriate surgical treatment in a timely manner.

　　②Congenital megacolon: Congenital megacolon ranks second in gastrointestinal malformations, about 1/3 of the children have acute intestinal obstruction in the neonatal period (i.e., within 1-6 days after birth), with clinical manifestations of constipation. There is still no meconium or only a small amount of meconium excreted 24-48 hours after birth, and more meconium can only be excreted after enema or anorectal examination. Subsequently, abdominal distension relieves, but after a few days, refractory constipation appears again. Neonatal congenital megacolon, if not treated in time, can often lead to serious complications such as small intestinal and colonic inflammation, colon perforation, and megacolon crisis, with a high mortality rate. After diagnosis, non-surgical treatment should be performed first, and if it is ineffective, megacolon resection should be performed after 2 months.

　　③Differential diagnosis methods for neonatal low intestinal obstruction: A. Check if the child has an anus, the position, size of the anal orifice, and whether there is a fistula; B. Anorectal examination should be routine, if there is no anus, it is anorectal malformation, and if there is an anus, anorectal examination should be performed immediately. During the anorectal examination, attention should be paid to whether meconium is excreted, if there is no normal meconium, only a few grayish-white lumps or mucus, it should be considered as congenital intestinal atresia. If a large amount of meconium is excreted, it should be considered as meconium constipation or congenital megacolon. Meconium constipation improves after enema and does not recur, while congenital megacolon can repeatedly appear abdominal distension and constipation. Neonatal congenital megacolon, if not treated in time, can often lead to serious complications such as small intestinal and colonic inflammation, colon perforation, and megacolon crisis, with a high mortality rate. After diagnosis, non-surgical treatment should be performed first, and if it is ineffective, megacolon resection should be performed after 2 months.