Congenital hypertrophic pyloric stenosis

　　1. Etiology of the disease

　　In order to clarify the etiology and pathogenesis of pyloric stenosis, a lot of research work has been carried out over the years, including pathological examination, establishment of animal models, detection of gastrointestinal hormones, virus isolation, genetic research, etc., but the etiology is still not clear to this day.

　　1. Genetic factors play a very important role in etiology. The onset has a clear familial nature, even to the extent that a mother and 7 sons in a family are affected, and it is more common in monozygotic twins than in dizygotic twins. The incidence rate of children with a history of pyloric stenosis in both parents can reach 6.9%. If the mother has this history, the probability of her son being affected is 19%, and her daughter is 7%; if the father has this history, the respective probabilities are 5.5% and 2.4%. Research has pointed out that the genetic mechanism of pyloric stenosis is polygenic, neither recessive nor sex-linked, but is directed by a dominant gene and a sex-modified multifactor gene. This genetic predisposition is influenced by certain environmental factors, such as social class, types of diet, various seasons, etc., with the highest incidence in spring and autumn, but the related factors are not clear. It is common in male infants with high body weight, but it is not related to the length of gestation.

　　2. Researchers specializing in the study of the pyloric enteric nerve plexus found that ganglion cells do not mature until 2 to 4 weeks after birth, therefore, many scholars believe that maldevelopment of neural cells is the mechanism that causes hypertrophy of the pyloric muscle, and they deny the past theory that the degeneration of pyloric ganglion cells leads to lesions, using histochemical analysis to determine the activity of enzymes in the pyloric ganglion cells; however, there are also those who hold different opinions, observing that the ganglion cells in pyloric stenosis are not the same as those in fetuses, such as maldevelopment of ganglion cells being the cause, then premature infants should have more cases than full-term infants, but there is no difference between the two. Recent research suggests that structural changes and dysfunction of peptide neurotransmitters may be one of the main causes, observed through immunofluorescence technology that the number of nerve fibers containing enkephalin and vasoactive intestinal peptide in the circular muscle is significantly reduced, and the application of radioimmunoassay to determine the content of substance P in the tissue is reduced, thereby suggesting that these changes in peptide neurotransmitters are related to the onset of the disease.

　　3. Experimental administration of pentagastrin to pregnant dogs resulted in a high proportion of puppies born with pyloric stenosis. It was also found that the serum gastrin concentration was relatively high in pregnant women in the last 3 to 4 months of pregnancy. It is believed that pregnant women in the later stages of pregnancy have an increased serum gastrin concentration due to emotional anxiety, which enters the fetus through the placenta, combined with the定向 genetic factors of the fetus, causing long-term pyloric spasm and obstruction. The expansion of the pylorus stimulates G-cell secretion of gastrin, leading to the onset of the disease. However, other scholars have repeated measurements of gastrin, with some reports showing increased levels and some showing no abnormal changes. Even in cases with increased gastrin levels, it cannot be inferred whether it is the cause or the result of pyloric stenosis, as some cases returned to normal levels of gastrin within a week after surgery, while others increased. In recent years, research on gastrointestinal stimulants has measured the concentration of prostaglandins (E2 and E2a) in serum and gastric juice, indicating that the content in the gastric juice of children is significantly increased, suggesting that the pathogenesis is the increase in local hormone concentration in the pyloric muscle layer, causing the muscle to be in a state of continuous tension, thereby leading to the onset of the disease. Some researchers have also studied serum cholecystokinin, with no abnormal changes observed.

　　4. Some scholars have observed and studied in detail and found that some infants born between 7 to 10 days old show signs of forcibly passing curdled milk through the narrow pyloric canal. It is believed that this mechanical stimulation can cause edema and thickening of the mucosa. On the other hand, it also leads to functional disorders of the cerebral cortex in the viscera, causing the pylorus to spasm. These two factors promote the formation of severe obstruction in the pylorus and the appearance of symptoms. However, there are also some who hold a negative view, believing that the first cause of pyloric spasm leading to functional hypertrophy of the pyloric muscle is inappropriate, because the hypertrophied muscle is mainly the circular muscle, and in addition, spasms should cause certain early symptoms. However, in some cases where surgery was performed early due to vomiting, it is usually found that the mass has already formed, and the size of the mass is not related to the duration of the disease. Pyloric obstruction symptoms appear when the muscle hypertrophy reaches a certain critical value.

　　5. The incidence of environmental factors has a significant seasonal peak, mainly in spring and autumn. White blood cells are found to infiltrate around the ganglion cells in the tissue sections of biopsies. It is speculated that this may be related to viral infection, but no Coxsackie virus was isolated from the blood, feces, and pharynx of the children and their mothers. The detection of serum neutralizing antibodies also showed no change. No pathological changes were observed in animals infected with Coxsackie virus, and the research is ongoing.

　　The main pathological change is hypertrophy of the pyloric muscle layer, especially the circular muscle, but it also manifests similarly in the longitudinal muscle and elastic fibers. The pyloric part is olive-shaped, hard and elastic. When the muscle is spasmodic, it becomes even harder. Generally, it is 2-2.5 cm long, 0.5-1 cm in diameter, and the muscle layer is 0.4-0.6 cm thick, and the tumor is larger in older children. However, the size is not related to the severity of symptoms and the duration of the disease. The surface of the tumor is covered with peritoneum and is very smooth, but due to the pressure on blood supply, part of it is obstructed, so the color appears pale. The circular muscle fibers increase and thicken, the muscle is as hard as sand, the thickened muscle layer squeezes the mucosa into longitudinal folds, making the lumen narrow, and with mucosal edema, inflammation occurs later, making the lumen even smaller. In the cadaveric specimen, the pylorus can only pass a probe that is 1 mm in diameter. As the narrow pyloric lumen transitions to the gastric antrum, the cavity becomes conical and gradually wider, and the thickened muscle layer becomes gradually thinner, with no precise boundary between them. However, the boundary is clear on the duodenal side, because the muscle layer of the gastric wall is not continuous with the muscle layer of the duodenum, the thickened pyloric tumor suddenly terminates and bulges into the duodenal cavity, resembling a cervical structure. Histological examination shows hyperplasia and hypertrophy of the muscle layer, disordered arrangement of muscle fibers, edema and congestion of the mucosa.

　　Due to pyloric obstruction, there is proximal gastric dilation, wall thickening, increased and edematous mucosal folds, and due to retention of gastric contents, it often leads to mucosal inflammation and erosion, even ulcers.

　　Secondly, Pathogenesis

　　The pylorus is characterized by complete muscular hypertrophy and hyperplasia, with a prominent ring muscle, caused by thickening of muscle fibers and hyperplasia of the connective tissue between muscle bundles. The thickened muscle tissue gradually transitions to the normal gastric wall. On the duodenal side, because the muscle layer of the gastric wall does not continue with the muscle layer of the duodenal wall, the thickened part suddenly terminates at the beginning of the duodenum, making the pylorus appear as a spindle-shaped tumor, 2-3 cm in length, 1.5-2 cm in diameter, and the muscle layer is as thick as 0.4-0.6 cm. The surface is pale and smooth, hard like cartilage. As age increases, the tumor grows. The thickened muscle layer pushes the mucosa inward and forms folds, causing the pyloric lumen to become narrow, resulting in incomplete obstruction. The obstruction of gastric emptying leads to increased peristalsis of the stomach, thickening of the gastric wall, and secondary gastric dilation. On the duodenal side, due to strong peristalsis, part of the pyloric lumen is pushed into the duodenal bulb, causing the duodenal mucosa to fold like a cervix. After pyloric obstruction, milk retention stimulates the gastric mucosa to produce congestion and edema.

　　1. Severe dehydration, insufficient body fluids;

　　2. Electrolyte disorder: alkalosis, shallow and slow breathing, and symptoms such as laryngeal spasm and cramps of the hands and feet may occur. Later, with low renal function, acidic metabolic products accumulate in the body, part of the alkaline substances are neutralized, so there are few cases of obvious alkalosis;

　　3. Malnutrition: below the body's requirement;

　　4. There is a risk of asphyxia;

　　5. There is a risk of infection after surgery.

　　1. Vomiting

　　Vomiting is the initial symptom of this disease. Generally, children with congenital hypertrophic pyloric stenosis show no symptoms after birth. Breastfeeding and defecation are normal, and vomiting usually occurs 2 to 3 weeks after birth. In a few cases, vomiting occurs immediately after birth, or occasionally, it may take up to 7 to 8 weeks to start vomiting. Premature infants tend to develop the disease later, starting with postprandial regurgitation, occasionally with vomiting, which gradually increases in frequency, eventually resulting in vomiting after every feeding. Vomiting usually appears within a few minutes after feeding, changing from general vomiting to projectile vomiting, which can be thrown several feet away in severe cases, often coming out of the mouth and nostrils. In immature infants with pyloric stenosis, vomiting is often non-specific, being general and without projectile vomiting. The vomit consists of milk and gastric juice or milk curd, without bile. In severe cases, the vomit may be coffee-colored (accounting for 3% to 5%), and as the stomach gradually expands and relaxes, milk remains in the stomach for a longer period, resulting in a decrease in the frequency of vomiting compared to before. Sometimes, one or two feedings may not result in vomiting, but the amount of vomit after the next feeding is often greater than the intake. The two amounts are vomited together, containing more milk curd and a sour taste. Although vomiting occurs frequently, there is still a strong appetite, showing a feeling of hunger. If breastfed again, the child can suckle normally. In severe cases of vomiting, the stool decreases, defecating once every few days, with dry and hard stool, and urine output also decreases.

　　2. Gastric peristalsis waves

　　Abdominal examination shows an abdominal bulge in the upper abdomen, a flat and soft lower abdomen, and about 95% of the children show gastric peristalsis waves in the upper abdomen, starting from below the left rib and moving to the upper right abdomen before disappearing. Sometimes, two waves appear successively, especially after feeding, which is more easily seen. Sometimes, gently tapping the abdominal wall can also cause the appearance of gastric peristalsis waves. Gastric peristalsis waves are common in congenital hypertrophic pyloric stenosis but are not specific signs. They are usually seen during feeding or after a meal. Premature infants can also show them under normal circumstances, and they cannot be used as a basis for diagnosis.

　　3. Abdominal mass

　　The presence of an olive-like mass in the upper right quadrant of the abdomen is a characteristic sign of pyloric stenosis. If this mass can be felt and combined with a history of typical vomiting, a diagnosis can be confirmed. However, this mass is not always easy to feel, and the detection rate of the mass is related to the examiner's experience, especially their patience. The examination is best performed when the child is deeply asleep or being breastfed in the mother's arms. At this time, the child is suckling vigorously, the abdominal wall is relaxed, and the physician stands on the child's right side, using the tip of the middle finger to gently massage deep into the upper right quadrant of the abdomen below the ribs and the outer edge of the rectus abdominis muscle. An olive-shaped, relatively hard pyloric mass can be felt. Sometimes, due to the deep position of the mass, it is covered by the liver and is not easily palpable. In this case, place the left hand behind the child to slightly support them, and with the right middle finger, push the liver margin upwards before touching deeper. With patience and careful repeated checks, the mass can be felt in almost all cases. Premature infants, due to poor development of abdominal muscles and a thin abdominal wall, are more likely to be palpated.

　　4. Dehydration and malnutrition

　　Due to the progressive worsening of vomiting, inadequate intake, frequent dehydration, no weight gain in the early stage, and a rapid decline in weight thereafter, the child appears to be losing weight day by day. If a child with the disease is not treated within 2 to 3 weeks of onset, their weight may be about 20% lower than at birth, presenting with malnutrition. Subcutaneous fat decreases, the skin becomes loose, dry, with wrinkles, elasticity disappears, the fontanelle and eye sockets become sunken, the buccal fat disappears, and the child has a prematurely aged appearance.

　　5. Alkalosis

　　Due to long-term vomiting, large amounts of gastric acid and potassium ions are lost, which can lead to hypochloremia and hypokalemic alkalosis. Clinical manifestations include shallow and slow breathing. Due to the decrease in free calcium ions in the blood, hypocalcemia can cause tetany, manifested as twitching of the hands and feet, laryngeal spasm, and tonic spasms. However, if the child is severely dehydrated, renal function is low, and acidic metabolic products are retained in the body, some alkaline substances are neutralized, so it is not common to have significant alkalosis. A few late cases may even have metabolic acidosis as the main manifestation, characterized by listlessness, refusal to eat, and pale complexion.

　　6. Jaundice

　　2% to 3% of children may develop jaundice, mainly due to increased indirect bilirubin. After surgery, jaundice gradually disappears. The cause of jaundice is related to insufficient calories, dehydration, acidosis affecting the activity of glucose醛酰transferase in liver cells, and delayed defecation increasing the enterohepatic circulation. Sometimes, there is an increase in direct bilirubin, which is due to mechanical obstruction by the thickened pylorus compressing the common bile duct; autonomic nervous imbalance causing spasm of the common bile duct; dehydration leading to bile concentration and stasis, and other factors.

　　To prevent congenital hypertrophic pyloric stenosis, the best way to exclude gas in the gastric cavity before examination is to drink water or milk and assume a right lateral position. Experts suggest: This disease is a congenital digestive tract malformation with no effective preventive measures. Drug treatment cannot correct the malformation. Early detection and early treatment are the key to prevention and treatment. Therefore, it is necessary to go to the hospital for a pyloromyotomy as soon as possible, which has a good effect.

　　1. Abdominal X-ray film and barium meal examination

　　1. Abdominal X-ray film:An upright abdominal X-ray film shows gastric dilation, the lower limit of the stomach reaching below the level of the second lumbar vertebra, with reduced intestinal gas; lying down can see gastric peristalsis waves.

　　2. Barium meal examination:For cases where a mass cannot be palpated, barium meal X-ray examination should be performed to detect typical X-ray changes and make a diagnosis. After the child takes a dilute barium solution, under X-ray fluoroscopy, it can be seen that the stomach is expanded to varying degrees, with increased peristalsis, and there may be gastroesophageal reflux. The barium stops at the pyloric part or only a small amount of barium enters the duodenum.

　　Barium retention time is prolonged, in normal infants, barium can be seen passing through the pylorus into the duodenum immediately or a few minutes after taking barium; when there is pyloric stenosis, no barium passes through the pylorus for 15 to 20 minutes; in addition, the time for the contrast medium to be excreted is also significantly prolonged, the normal gastric emptying time for infants is 2.5 to 3 hours, while in pyloric stenosis, it takes 6 to 10 hours to empty, and even 24 hours later, barium may still be retained in the stomach. More importantly, if observed carefully in the right anterior oblique position, the pyloric canal can be seen to be thin and narrow, presenting a 'thread-like sign', extending to 1 to 3.5 cm; the thickened circular muscle of the pylorus compresses the antrum, showing a 'shoulder sign'; compressing the base of the duodenal bulb changes it into a mushroom-like shape, known as the 'mushroom sign'; the pyloric canal is not filled with barium, only the pyloric orifice is filled with barium, resembling a bird's beak, known as the 'bird's beak sign'; edematous mucosa is located in the center of the pyloric canal, with parallel barium filling on both sides, known as the 'double track sign', and other characteristic X-ray changes of congenital hypertrophic pyloric stenosis, such as the pressure mark at the base of the duodenal bulb, should be noted. The barium emptying time is prolonged, and care should be taken to aspirate the barium to prevent aspiration.

　　二、超声检查

　　幽门肥厚的诊断标准：幽门管长径>16mm，幽门肌厚度≥4mm，幽门管直径>14mm，若以上3个标准未同时达到，仅有一项或两项达到标准，则采用超声评分系统[2]，评分≥4时诊断为CHPS，≤2时为阴性，=3分时建议进一步检查，CHPS的超声图像：肥厚的幽门环肌呈实质性中等或低回声团块，轮廓清晰，边界清，幽门管中央黏膜层呈强回声，幽门管腔呈线状无声，当胃蠕动强烈时可见少量液体通过幽门管，有人提出的狭窄指数大于50％作为诊断标准，并可注意观察幽门管的开闭和食物通过情况，有人发现少数病例幽门管开放正常：称为非梗阻性幽门肥厚，随访观察肿块逐渐消失。

　　Third, endoscopic examination

　　It can be seen that the pyloric tube is narrowed in a cauliflower-like manner, the lens cannot pass through the pyloric tube, there is gastric retention, and the diagnosis rate is 97%.

　　Diet should be light and nutritious, with attention to dietary balance. The patient's diet should be light and easy to digest, with more vegetables and fruits, a reasonable diet, and attention to adequate nutrition. In addition, patients should also pay attention to avoiding spicy, greasy, and cold foods.

　　First, treatment

　　1. Internal medicine therapy can be used for cases where the diagnosis is uncertain, symptoms are mild, or the onset is late; there are no surgical conditions or due to concurrent other diseases, surgery cannot be performed temporarily, or parents refuse surgical treatment. Some believe that the circular muscle gradually softens and shrinks from 4 to 9 weeks after birth, or consider that the obstruction is not complete, and some milk can still pass through. There are spasm factors in the obstruction, advocating the use of internal medicine therapy first.

　　(1)Antispasmodic treatment: Use a freshly prepared atropine solution at a concentration of 1:1000 or 1:2000, taken orally 30 minutes before feeding. The dose starts from 1 drop and is gradually increased to 2 to 6 drops, until the skin turns red. It can also be tried with 0.6% methyl nitrate atropine or scopolamine nitrate, 0.12 to 0.15mg each time, which is 5 times more potent than atropine with less toxic reaction.

　　(2)Appropriately reduce the milk volume: Use thickened milk, such as adding 1% to 3% of cake powder to the milk.

　　(3) Correction of dehydration and acidosis: Use normal saline, not alkaline solution, due to the lack of chloride in the body, and at the same time, pay attention to potassium supplementation.

　　(4) Others: Some foreign reports have stated that feeding through the duodenum was used in conservative treatment of 50 cases, with a cure rate of 90%, and an average hospital stay of 39.7 days. There have also been reports of 3 cases cured by endoscopic balloon dilation.

　　II. Surgical treatment: Pyloric muscle incision is the best treatment method, with a short course and good effect. It is necessary to prepare for 24 to 48 hours before surgery, correct dehydration and electrolyte disorders, and supplement potassium salts. Venous nutrition is provided for malnourished patients to improve the overall condition. In the 'I' type group, the serous layer is incised along the longitudinal axis of the pylorus during surgery, and the muscle layer is bluntly separated to the submucosal layer to make the mucosa completely bulge out of the serous layer. Pay attention not to damage the duodenal mucosa, and the proximal end should exceed the stomach end to ensure efficacy. Then, the muscle layer is incised deeply with a钝器, exposing the mucosa, and the incision is widened to more than 5mm in width to allow the mucosa to come out freely, and bleeding can be stopped by pressing. The inverted 'Y' type group starts the incision at about 2/3 of the pyloric ring muscle from the gastric antrum, and then cuts diagonally to both sides, forming an angle of about 100 degrees to form an inverted 'Y' incision. This method incises the muscle layer sufficiently, increases the range of mucosal bulging, and can significantly enlarge the pyloric canal, significantly reducing the incidence of duodenal mucosal injury and postoperative vomiting. The serosal layer incision should have sufficient length and depth, and the separation must reach the full length of the lesion, with the depth reaching the serosal level when the mucosa bulges.

　　Postoperative management: Postoperative vomiting may be related to pyloric stenosis and incomplete incision of the pyloric muscle, therefore, preoperative isotonic warm saline lavage is necessary. Postoperative eating should start the next morning, try to drink 15-30ml of sugar water, and if there is no vomiting 2 hours later, give an equal amount of breast milk or milk. Gradually increase the amount, and increase to normal quantity 48 hours after surgery. Most postoperative vomiting is the result of too rapid increase in diet, and should be reduced before gradually increasing. Normal intestinal function does not increase the incidence of ulcerative diseases, however, X-ray follow-up studies have found that successful pyloric muscle incision sometimes shows a narrow pylorus for 7 to 10 years.

　　II. Prognosis

　　Early diagnosis and treatment, without combined other organ malformations, have a good prognosis. Inadequate diagnosis and treatment can lead to malnutrition and pulmonary infection, resulting in death. The mortality rate in Europe and the United States is 0.12% to 0.5%, and in China it is 0.5% to 1%.