Congenital diseases of the rectum and anal canal

　　It is generally believed to be due to incomplete cavitation during the embryonic development stage of the anal canal, abnormal development of the anal-rectal membrane between the rectum and anal canal, incomplete penetration or non-disappearance of this membrane after birth, forming anal-rectal stenosis or even atresia. It is generally called congenital anal agenesis or congenital anal atresia. If the anal atresia after birth is not treated properly, it often forms stenosis. There are also cases where the sacrum and coccyx develop abnormally and compress the intestinal cavity.

　　The complications of congenital rectal and anal diseases are anal sphincter external fistula; anal sphincter upper fistula.

　　Sphincter external anal fistula is the least common, accounting for 1%, and is the consequence of pelvic rectal abscess and ischiorectal abscess. The fistula tube passes through the levator ani directly to the rectum. This anal fistula is often caused by Crohn's disease, colorectal cancer, or trauma, and the treatment should pay attention to the primary disease focus. The above classification is more detailed in terms of high and low positions, which is conducive to the selection of surgical methods.

　　Sphincter anal fistula is a high anal fistula, which is rare, accounting for 5%. The fistula tube passes through the levator ani and then descends to the ischiorectal fossa to penetrate the skin. Since the fistula often involves the anal and rectal ring, the treatment is more difficult and often requires staged surgery.

　　The vast majority of children with congenital rectal and anal malformations do not have an anus in the normal position and are easy to find. Rectal and anal malformations without fistula tubes show no meconium excretion, abdominal distension, and vomiting soon after birth; the orifice is narrow and cannot excrete meconium or only a small amount of meconium can be excreted. The child vomits after feeding, and then can vomit fecal-like matter, and gradually abdominal distension; the orifice is large. There may be no intestinal obstruction symptoms for a period of time after birth, and then gradually appear difficulties in defecation for several weeks to several years.

　　High rectal atresia, normal anus and anal infants show no meconium excretion, or turbid fluid excreted from the urethra. Rectal examination can find rectal atresia. Girls often have vaginal fistula. Urinary fistula is almost seen in boys. Exhaling from the urethral orifice and meconium are the main symptoms of rectal and urinary fistula.

　　Congenital rectal and anal atresia is a congenital disease. There are no effective preventive measures. Early detection and early treatment are the key to the prevention and treatment of the disease.

　　1. Avoid hereditary diseases:Methods for preventing hereditary diseases

　　2. Avoid consanguineous marriage:The offspring of consanguineous marriage have much lower intelligence than non-consanguineous offspring, and the incidence rate is very high. Therefore, it is necessary to avoid consanguineous marriage.

　　3. Pre-marital consultation:Both parties or one party, if there is a hereditary disease patient among their relatives, worry about whether a child with the same hereditary disease will be born after marriage, should consult whether they can get married, and if the consequences after marriage are very serious; one party of the two has a certain disease, but does not know whether it is a hereditary disease, can they get married, and what is the chance of passing it on to the offspring? The doctor will make a clear diagnosis and inform the reasonable treatment methods.

　　4. Avoid late childbearing:The age of childbearing should not be over 35 years old, because the cells of elderly pregnant women age, are prone to external viral infection, and the individuals formed after fertilization are prone to chromosomal diseases.

　　5. Conducting fertility counseling:If you have given birth to a child with low intelligence or disability, or if the child died prematurely due to illness, whether the same situation will occur in subsequent pregnancies; if the woman is a habitual aborter, whether she can have another child, and how to prevent it; if a woman has been sick during pregnancy, taken certain drugs, been exposed to chemical toxins, or worked in a radioactive polluted position, whether it will affect the fetus, etc. Through consultation, doctors will perform necessary examinations on both partners and give appropriate treatment methods and accurate advice.

　　6. Administrative department consultation:The health administration department or family planning department should consult with medical geneticists when drafting relevant eugenic policies, such as: whether the formulation of certain eugenic regulations and regulations is reasonable; what countermeasures should be taken to control common genetic diseases in a certain area; how to carry out the investigation of certain genetic diseases, etc. Therefore, newly married couples should consult relevant administrative departments.

　　7. Termination of pregnancy:If you are pregnant and find that you have a serious disease after examination, terminate the pregnancy as soon as possible.

　　Diagnosis based on medical history and clinical manifestations is not difficult. Congenital megacolon in infants and children often has a typical history and intractable constipation, with gradually worsening abdominal distension, manifested as chronic incomplete colonic obstruction.

　　To make a clear diagnosis and understand the location and extent of the lesion, the following examinations should be performed:

　　1. Abdominal X-ray examination:It can be seen as an expanded and aerated colon shadow, or it can be manifested as colonic obstruction.

　　2. Barium enema:A small amount of barium enema is used to understand the length of the spastic segment and the barium excretion function; if there is still residual barium 24 hours later, it is a sign of megacolon.

　　3. Rectal manometry:It is an effective method to check congenital megacolon, to understand whether the anal canal has normal relaxation reflex.

　　4. Rectal mucosal histochemical examination:The submucosal layer of the rectum can be observed under histochemical staining, showing nerve fibers with acetylcholinesterase-positive staining.

　　5. Biopsy:Submucosal and muscular layer tissue pathological examination should be performed to determine the presence of ganglion cells.

　　Pregnant women should not be picky about their diet before pregnancy, nor should they be anorexic, nor should they eat spicy foods. The variety of food should be comprehensive, free from pollution, and the balance of meat and vegetables should be reasonable. The arrangement of meals should be reasonable, and neither overeating nor fasting should be allowed. Pre-pregnancy diet should supplement various nutrients or energy such as vitamins, inorganic salts, trace elements, fats, proteins, calories, and folic acid. Pregnant women are prohibited from drinking alcohol and eating spoiled food. Alcohol and spoiled food are prone to cause malformation. It is necessary to prevent the occurrence of congenital rectal and anal diseases in advance.

　　The treatment methods vary according to the type of rectal and anal malformation, but all require surgical treatment. Anal and rectal atresia should be operated on immediately after birth.

　　Low-grade malformation surgery is relatively simple and can be completed through perineal approach. For simple anal membrane atresia, it is only necessary to excise the anal membrane and suture the rectal mucosa with the anal skin. For anal atresia, the distal rectal blind end can be freed, pulled out through the anus, and sutured with the anal skin to perform anal canal shaping surgery.

　　High-grade malformations require transabdominal, perineal, or post-sagittal incision approaches for anal canal and rectal shaping surgery. Surgical principles: ①游离rectal blind end; ②For those with fistula, excise the fistula and repair it; ③Anal and rectal shaping. Generally, a colostomy is performed first, followed by a second-stage operation 6-12 months later.

　　Congenital megacolon is a type of intestinal developmental malformation in which the neural ganglion cells are absent in the affected intestinal wall. In digestive tract malformations, its incidence rate is second only to congenital rectal and anal malformations, and has a familial occurrence tendency. The incidence rate is about 1:5000, and it is more common in males, with a male-to-female ratio of 4:1. The occurrence of congenital megacolon is due to the arrest of the migration and development process of the ectodermal neural crest cells, resulting in the absence of neural ganglion cells in the intermuscular plexus of the distal intestinal tract (rectum, sigmoid colon), causing persistent spasm of the intestinal tract, leading to functional intestinal obstruction, and the proximal colon becomes secondary dilated. Therefore, the primary lesion of congenital megacolon is not in the dilated and thickened intestinal segment, but in the distal narrow intestinal segment. The length of the segment without ganglion cells varies, so congenital megacolon has long-segment and short-segment types. The pathological basis of congenital megacolon is the complete absence of normal neural ganglion cells visible in the neural plexus of the muscular layer of the intestinal wall and the submucosal neural plexus, and there is also a type called megacolon-related diseases. These include decreased, underdeveloped, and maldeveloped ganglion cells, as well as underdeveloped neurons.