Neonatal necrotizing enterocolitis

Introduction to neonatal necrotizing enterocolitis Neonatal necrotizing enterokolitis (NEC) is an acquired disease that occurs mainly in premature or diseased neonates. It is characterized by abdominal distension and blood in the stool. It is characterized by intestinal mucosa and even deep intestine. Necrosis, most commonly occurs in the distal ileum and proximal to the colon, the small intestine is rarely involved, and the abdominal X-ray plain film is characterized by cystic gas accumulation in the intestine. This disease is a very serious disease in the neonatal digestive system. basic knowledge Probability ratio: Newborn incidence rate is about 1% Susceptible people: children Mode of infection: non-infectious Complications: peritonitis, ascites, sepsis

Causes of neonatal necrotizing enterocolitis

(1) Causes of the disease

The cause of necrotizing enterocolitis has not been fully elucidated, but it is generally thought to be caused by a combination of causes, among which preterm birth and infection are the most important.

1. Premature delivery: Premature birth is an important pathogenic factor of NEC. Due to poor immune function, poor peristalsis, and suffocation at birth, causing hypoxia damage in the intestinal wall, causing bacterial invasion.

2. Infection: Infection is one of the main causes of NEC, mostly intestinal bacteria such as Klebsiella, Escherichia coli, and Pseudomonas aeruginosa.

3. Hypoxia and ischemia: In the neonatal asphyxia, respiratory disease, shock and other hypoxic-ischemic conditions, the intestinal wall vasoconstriction, resulting in intestinal mucosal ischemia and hypoxia, necrosis, with the recovery of oxygen, vasodilatation and congestion, Reperfusion during expansion increases tissue damage.

4. Feeding: Eating and exchanging blood transfusion can increase the reperfusion of the intestinal wall, which is the cause of the disease, leading to intestinal invasion by bacteria. Once feeding, it provides sufficient substrate for intestinal bacterial reproduction, intestinal feeding. It has long been considered as a factor in the pathogenesis of NEC. Premature infants with infection and asphyxia prematurely, excessive feeding of cow's milk can induce NEC, but the opinion of feeding leading to NEC is still controversial. It is reported that the incidence of NEC in preterm infants started to be fed until 2 weeks is reported. Instead, it is higher than early feeding.

5. Others: umbilical artery or vein cannulation, transfusion therapy, polycythemia, open arterial catheter, hypothermia, etc., the incidence of NEC is higher.

(two) pathogenesis

In children with necrotizing enterocolitis, there are usually three factors in the small intestine: persistent intestinal ischemic damage, bacterial colonization, and intestinal lumen (eg, enteral feeding).

1. Intestinal wall hypoxia and inflammatory injury: premature infants with poor immune function, poor intestinal peristalsis, long food residence time, easy to make bacteria growth; high milk osmotic pressure, infection, asphyxiating premature infants prematurely overfeeding milk, can be aggravated Intestinal wall mucosal damage, induces NEC, suffocation at birth causes hypoxic damage to the intestinal wall, allowing bacteria to invade, excessive bacterial growth and toxins can cause inflammation in the hypoxic intestinal wall, and cytokines released by tissue during inflammation, such as platelets Activating factor, tumor necrosis factor, prostaglandin, etc., aggravate the inflammatory reaction and promote the occurrence of NEC. Klebsiella has a strong fermentation effect on lactose in food, and the hydrogen produced causes cystic gas accumulation in the intestinal wall.

2. Hypoxia and reperfusion injury: ischemic damage can be caused by hypoxic damage, such as neonatal asphyxia, respiratory disease, triggered by the original diving reflex, caused by mesenteric artery spasm, resulting in a significant reduction in intestinal blood flow In the process of blood transfusion, during the period of sepsis or when fed with high-tension formula, the intestinal blood flow is reduced, leading to intestinal ischemic damage. Similarly, shock, congenital heart disease and other ischemic conditions can reduce systemic blood flow. Or decreased arterial oxygen saturation, resulting in intestinal mucosal ischemia and hypoxia, necrosis; recovery of oxygen supply, reperfusion during feeding and exchange transfusion, increased tissue damage.

3. Pathological changes: NEC can affect the entire small intestine and colon, but the most common sites are in the distal part of the ileum and proximal to the ascending colon. In mild cases, the necrotic intestine is only a few centimeters. In severe cases, it can extend to the jejunum and colon, but generally Does not affect the duodenum, bacteria can penetrate the intestinal wall, produce hydrogen and accumulate, produce characteristic intestinal wall gas on the X-ray, gas and can enter the portal vein, visible to the liver through the abdominal X-ray film or liver B-ultrasound The above portal vein gas accumulation, along with the progression of the lesion, can lead to necrosis, perforation, peritonitis, sepsis and death of the entire intestinal wall. Early lesions are mainly intestinal mucosa and submucosal congestion, edema, hemorrhage, necrosis, and advanced lesions. Enlargement, involving the muscular layer, severe intestinal necrosis of the intestinal wall, can be complicated by intestinal perforation and peritonitis.

Neonatal necrotizing enterocolitis prevention

NEC can be an outbreak and is contagious. Therefore, if several cases of necrotizing enterocolitis occur in a short period of time, the sick child should be isolated and the other exposed infants should be evaluated for newborns and premature births that have been directly or indirectly contacted. Children need to check the appearance of bloating and the nature of stool every day. Once bloating occurs, they should be alert to the occurrence of NEC. For very small or premature infants, delay the feeding for several days or weeks by using total parenteral nutrition, and then for several weeks. The slow increase in intestinal feeding during the time can reduce the incidence of necrotizing enterocolitis (NEC).

Neonatal necrotizing enterocolitis complications Complications peritonitis ascites sepsis

If the disease progresses, intestinal necrosis starts from the mucosa and gradually affects the whole layer of the intestinal wall, leading to intestinal perforation, peritonitis and ascites. One third of the newborns can develop sepsis, and multiple organ dysfunction, DIC and so on.

Neonatal necrotizing enterocolitis symptoms common symptoms pale pale hypothermia diarrhea watery stool bowel phlegm refused to eat abdominal distension black stool jaundice intestinal perforation

More male infants than female infants, mainly sporadic cases, no obvious seasonality, normal meconium after birth, often within 2 to 3 weeks after birth, with a peak of 2 to 10 days, NEC in the epidemic of neonatal diarrhea It can also be a small epidemic, with no gender, age and season differences.

1. Abdominal distension and bowel sounds weakened: children with delayed gastric emptying, gastric retention, followed by abdominal distension, light only abdominal distension, severe cases of symptoms quickly increased, abdominal distension such as drums, bowel sounds weakened, or even disappeared, premature delivery NEC bloating is not typical, abdominal distension and bowel sounds are the early symptoms of NEC. For high-risk children, the changes of abdominal distension and bowel sounds should be observed at any time.

2. Vomiting: Children often have vomiting, vomit can be coffee-like or with bile, some children have no vomiting, but the stomach can extract coffee or bile-like stomach contents.

3. Diarrhea and bloody stools: watery stools at the beginning, ranging from 5 to 6 times to more than 10 times a day. After 1 to 2 days, they are bloody stools, which can be blood, jam or black stool. In some cases, there is no diarrhea and naked eyes. Bloody stools, only stool occult blood positive.

4. Systemic symptoms: children with NEC often have poor response, wilting, refusal to eat, severe cases with pale or gray, cold limbs, shock, acidosis, jaundice, premature infants are prone to repeated apnea, slow heart rate, body temperature Normal or have low fever, or body temperature does not rise.

Neonatal necrotizing enterocolitis examination

1. Peripheral blood: white blood cells increase, classification of nuclear left shift, thrombocytopenia.

2. Blood gas analysis and electrolyte determination: can understand the degree of electrolyte imbalance and acidosis, and guide the treatment of liquid and intravenous nutrient solution.

3. Fecal examination: the appearance of dark color, occult blood positive, microscopic examination of a number of white blood cells and red blood cells, stool culture of Escherichia coli, Klebsiella and Pseudomonas aeruginosa more common.

4. Blood culture: If the cultured bacteria are consistent with the culture of feces, it is meaningful for the diagnosis of the cause of NEC.

5. Abdominal X-ray film examination: It has great value for the diagnosis of NEC. It is necessary to follow up and check for dynamic changes.

(1) Early performance:

1 small intestine is light, moderate flatulence, the colon can be less gas or flatulence.

2 There may be a small liquid level in the intestinal lumen.

3 intestinal mucosa and intestinal gap thickening.

4 The intestinal tube is disorderly arranged, the shape is stiff, and the lumen is irregular or narrow.

(2) Changes in the progress period:

1 Intestinal cavities are aggravated, and the level of fluid is increased, which is stepped, suggesting that the lesions involve the muscular layer.

2 In the submucosal layer of the intestinal wall, gas accumulation appears as a dense small foam-like translucent area, called pneumatosis cystoides intestinalis, and the sub-serosal gas is thin strips, semi-arc or circular translucent.

3 The intestinal wall has a long gas accumulation time, and the gas can rise from the intestinal wall to the portal vein, resulting in accumulation of gas in the portal vein, showing a branch-like upward translucent shadow at the portal vein of the liver, which can be absorbed and disappeared within 4 hours.

4 intestinal tube fixation.

5 peritoneal effusion, pneumoperitoneum occurs in acute intestinal perforation, such as the perforation is closed by the mesenteric membrane, the escaped gas is absorbed, X-ray film can not be easily displayed.

6. Bacterial culture: Most of the smear and culture of peritoneal puncture fluid are bacilli, and the abdominal cavity fluid taken during surgery is cultured with bacteria, and the positive rate is high.

7. Abdominal B-ultrasound: visible microscopic air bubbles appear intermittently in the liver parenchyma and portal vein.

Diagnosis and diagnosis of neonatal necrotizing enterocolitis

diagnosis

In children with risk factors for this disease, a more positive diagnosis can be made once the relevant clinical manifestations and X-ray examination changes occur.

1. History and clinical manifestations: For premature infants with high risk factors, close observation of abdominal distension and bowel sound changes, vomiting, abdominal distension, diarrhea and bloody stools should be taken immediately to test the abdominal X-ray film and fecal occult blood test.

2. Fecal examination: occult blood screening or reducing substance examination in premature infants (beginning of feeding) can help early diagnosis of necrotizing enterocolitis, occult blood positive, white blood cells and red blood cells, stool culture is consistent with blood culture Bacteria.

3. Blood culture: neonatal necrotic enteritis, blood culture has a certain positive rate, should pay attention to this check.

4. Abdominal X-ray examination: It is the main means of diagnosing NEC. For those suspected of NEC, it is necessary to take a positive radiograph of the abdominal X-ray in time, follow-up and observe the dynamic changes.

For some children with bloating and vomiting, X-ray examination only changes the gastrointestinal motility intestinal obstruction, there is no intestinal wall accumulation, and can not remove the mild early stage of this disease, should be closely followed, repeated X-ray examination, fixed position The dilated bowel segment suggests the presence of necrotizing enterocolitis. The X-ray diagnosis of necrotizing enterocolitis is the accumulation of gas in the intestinal wall and portal vein. The pneumoperitoneum suggests intestinal perforation. Emergency surgery is needed. The most important thing is that it needs constant Reassess the infant (eg at least 6 hours) and continuous abdominal X-ray, complete blood count, platelet count and blood gas analysis.

Differential diagnosis

1. Toxic intestinal paralysis: When the primary disease is diarrhea or sepsis, it is easy to misdiagnose NEC as toxic intestinal paralysis, but the toxic intestinal paralysis has no blood in the stool, and there is no gas accumulation between the intestinal wall on the X-ray film.

2. Mechanical small bowel obstruction: On the X-ray web, the span of the liquid surface is larger, the intestinal wall is thinner, the intestinal gap is widened, the blur is not formed, and there is no gas accumulation in the intestinal wall.

3. Intestinal torsion: The symptoms of mechanical intestinal obstruction are severe when the torsion is reversed, and vomiting is frequent. The plain X-ray film shows the image of duodenal obstruction, the abdominal density is evenly deepened, and there is irregular polymorphic gas shadow, no obvious inflation expansion. Intestines.

4. Hirschsprung's disease: Early NEC showed that the small intestine should be differentiated from congenital megacolon when it is generally flatulent. The latter is mainly bloating, difficulty in defecation, no bloody stool, and X-ray dynamic observation of abdominal changes without intestinal wall gas accumulation. It is easier to identify in combination with clinical.

5. Neonatal hemorrhagic disease: 2 to 5 days after birth can occur gastrointestinal bleeding, the need to identify, neonatal hemorrhagic disease did not give vitamin K injection history after birth, abdominal distension, abdominal X-ray film no Intestinal cavity inflation and intestinal wall accumulation, vitamin K treatment is effective.

6. Meconium peritonitis: In some cases, the abdominal X-ray film can be seen scattered in the small vesicle-like intestinal wall, but there may be typical abnormal calcification, and it is not difficult to identify with clinical combination.

7. Spontaneous gastric perforation: mostly caused by congenital gastric wall muscle defect, often occurs in the big stomach near the cardia, most of the children have a history of hypoxia at birth, sudden onset, sudden onset 3 to 5 days after birth Abdominal distension, accompanied by vomiting, difficulty breathing and cyanosis, X-ray plain abdomen only see pneumoperitoneum, no intestinal wall gas or intestinal tube flatulence.

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