Congenital megacolon is usually caused by low-level functional intestinal obstruction of the colon due to abnormal nerve distribution. The pathogenesis is that due to the lack of intermuscular and submucosal nerve plexuses in the intestinal wall, the smooth muscle spasm of the corresponding intestinal segment causes the intestinal contents to be easily expelled through the diseased intestinal segment, resulting in partial or complete intestinal obstruction due to the accumulation of intestinal lumen contents. The lumen of the intestine with normal nerve distribution is severely dilated, and compensatory hypertrophy develops after a long period of time. The lesion may occur in part of the colon or the entire colon, but rarely the terminal ileum and the entire gastrointestinal tract are involved.
It is important to diagnose children with megacolon as early as possible. The later the treatment, the more likely it is that small bowel colitis will occur because of bacterial overgrowth in the dilated section of the intestine releasing bacterial toxins, causing loss of large amounts of fluid from the intestinal lumen, or loss of large amounts of electrolyte fluid due to diarrhea causing dehydration or even death. As a result, parents who suspect abnormal bowel movements should seek prompt medical attention for early diagnosis.
Clinical symptoms: delayed defecation after birth (often 24-48 hours after birth), difficulty in defecation or difficulty in self-extraction of stool with assistance, little anal venting, obstinate constipation, abdominal distension, vomiting. Sometimes the constipation is only mild or phasic in nature.
In children with late diagnosis, anorexia and lack of normal desire to defecate may be present.
Diagnosis
Symptoms: delayed meconium evacuation after birth (often 24-48 hours after birth), progressive abdominal distension, persistent constipation, and in severe cases, vomiting. Delayed growth and development.
On examination: delayed growth, poor nutrition, abdominal distension, dilated colonic collaterals on abdominal palpation, and even intestinal pattern can be seen, anal examination: tight rectum, tight ring, or a sense of wrapped fingers, accompanied by a sense of rectal emptiness, and an explosive venting of stool when the fingers are withdrawn for examination. The possibility of megacolon should be considered.
Abdominal plain film: low-level intestinal obstruction.
Barium enema: typical visible colonic obstruction with distal narrowing and proximal dilatation and the presence of a migrating segment between the dilated and stenotic segments,resembling a funnel. The typical presentation may be lacking during the neonatal period; therefore, the examination is best repeated at 3 months of age if not clarified early.
Definitive diagnosis depends on rectal wall biopsy: absence of ganglion cells.
Differential diagnosis.
1, colonic class marginal disease: symptoms similar to megacolon, barium enema without typical megacolon changes, laparoscopic pathological biopsy can be differentiated.
2, functional constipation: it is also one of the most common digestive system diseases in childhood. According to the diagnostic criteria of functional constipation in China.
Diagnostic prerequisites: ① defecation ≤ 2 times per week; ② incontinence at least 1 time per week after one can control defecation; ③ history of stool retention; ④ history of painful or difficult defecation; ⑤ presence of large fecal masses in the rectum; ⑥ large enough feces to block the toilet outlet.
(1) Diagnostic criteria for functional constipation in newborns/young children (children under 4 years of age): Diagnosis is made by the presence of at least 2 of the above symptoms for at least 1 month. Accompanying symptoms include irritability, decreased appetite, and/or early satiety, which may disappear quickly with the passage of large amounts of stool.
(2) Children/adolescents with functional constipation must meet 2 or more of the diagnostic criteria (children over 4 years of age) and do not meet the diagnostic criteria for irritable bowel syndrome, have met these criteria for at least 2 months prior to diagnosis, and have at least 1 episode per week.
In addition, T3, T4, TSH, and blood glucose are measured for those who need differentiation to exclude hypothyroidism and diabetes mellitus. Sacrococcygeal plain radiography is performed to rule out sacrococcygeal malformation.
Functional constipation can be treated by adjusting the diet to increase the intake of liquid and fiber-rich diet; regular defecation to develop good defecation habits. The symptoms can be gradually improved.
Treatment.
Neonatal treatment: If the obstruction is not serious, the bowel can be assisted by warm saline (i.e. 0.9% sodium chloride aqueous solution at 38°C) lavage, 1-2 times a day (pay attention to the balance of water in and out, gentle movements, unclear must be learned in the hospital before self-lavage) to relieve symptoms, improve nutrition and promote normal development of the child. Surgery can be considered after the age of six months.
If the effect of bowel cleansing is not good, enterostomy is usually performed, and then after 3-6 months, radical surgery of giant colon is performed.
Treatment for infants and older children: surgery after clear diagnosis.
Surgical options.
1.Transanal megacolon radical surgery: common type of megacolon, the proximal intestinal canal dilatation is not intense, or the dilated segment is not long, and can be dragged out through the anus and the colonic blood supply is not affected.
2.Laparoscopic assisted transanal megacolon radical surgery: suitable for total colon type megacolon, long segment type megacolon, older, dilated section of colon is very thick and long, and it is difficult to be dragged out directly through the anus.
Of course, there are some other procedures depending on the experience of the surgeon.
Prognosis: good, most children have good bowel function.