Congenital anal and rectal malformation

　　The occurrence of anal-rectal anomalies is the result of developmental disorders during the embryonic development period. There is basically no difference between males and females, just the anatomical difference. The result of the cloaca separation process, the urinary sinus and anal-rectal sinus are connected, forming high or intermediate position anomalies. Various anal-rectal developmental abnormalities and fistulas between the rectum and the urethra or vagina occur. The obstacle in the posterior migration process of the anus and the underdevelopment of the perineum result in low position anomalies, causing anal skin fistula, anterior anal fistula, anal stenosis, etc.

　　Congenital anal-rectal anomalies can lead to complications such as acute complete low-position intestinal obstruction symptoms. Patients with anal-rectal stenosis may experience difficulties in defecation, constipation, fecal stone formation, and secondary megacolon, etc., as chronic obstruction symptoms.

　　1. Common Complications

　　Low-position intestinal obstruction in patients with associated anomalies often leads to dehydration and acidosis, and severe cases may develop shock and death. Secondary colonic enlargement and nutritional disorders are common. It often occurs with vulvitis and urinary tract infection.

　　2. Associated Anomalies

　　The incidence of associated anomalies ranges from 40% to 50%. The differentiation and development of the cloaca occur in the earliest stage of embryonic development. At the critical period of embryonic development, any non-specific factor can also simultaneously affect the development of other organs. Therefore, congenital anal-rectal anomalies often occur simultaneously with anomalies of other organs. Generally, the incidence of high-level anomalies associated with high-level anomalies is more than one times higher than that of low-level anomalies, and the anomalies are severe. Due to the presence of associated anomalies, the difficulty of treatment increases. Among the associated anomalies, urinary system anomalies are the most common, such as renal hypoplasia, unilateral or bilateral hydronephrosis, and ureteral hydronephrosis. Other organ anomalies, such as esophageal atresia, can reach 6% to 7%, and congenital megacolon accounts for 2% to 3%. Skeletal anomalies are mainly represented by hemivertebrae and vertebral fusion. Cardiovascular anomalies such as ventricular septal defects and atrial septal defects are about 7%. According to statistics from the Toronto Children's Hospital, among the associated anomalies of congenital anal-rectal anomalies, in addition to urinary system anomalies being the most common, 51% are skeletal anomalies, heart, nerve, and gastrointestinal tract anomalies. Chinese scholars reported that children with high and middle-level congenital anal-rectal anomalies have underdeveloped nerve endings in the puborectalis muscle and perianal tissues, with reduced density, and a certain number of muscle spindles in the puborectalis muscle. In addition, the morphology of the sacrum and the number of motor neurons in the medial group of the anterior horn of the sacral髓 also show abnormal changes in congenital anal-rectal anomalies.

　　3, Postoperative complications

　　The common complications after this disease are as follows:

　　(1) External mucosal inversion of the rectum: It often occurs within 3 months after surgery. With the softening of scars, the anal sphincter function may recover in mild cases, but severe cases may require reoperation for excision.

　　(1) Anal stenosis: To prevent stenosis, anal dilatation should be maintained for 1 to 1.5 years after surgery, and in cases of severe stenosis, a second operation should be considered.

　　(2) Faecal incontinence: High anal-rectal anomalies are common after surgery and are difficult to recover. Early postoperative defecation training should be performed.

　　(3) Constipation: In the early stage, it can be caused by pain from surgical trauma, and in the later stage, it is often caused by anal stenosis or rectal retraction forming a tubular stenosis. A few children have aganglionic megacolon, and in these cases, conservative treatment such as dilatation and enema is ineffective. Different surgical treatments should be considered according to specific conditions.

　　Congenital anal-rectal anomalies, being surface anomalies, are easy to diagnose. In addition to clinical examination, it is necessary to further measure the distance from the rectal blind end to the levator ani plane and the anal skin to determine the type of anomaly, the location of the fistula, and associated anomalies, so that appropriate treatment methods can be selected.

　　(1) High or levator ani anomaly

　　Accounts for about 40% of anal-rectal anomalies. Boys are more common than girls. Such children have slightly concave skin at the normal anal position, darker in color, but without an anus. When the child cries or strains, the concave area does not bulge outward, and there is no impact when touched with a finger. X-ray examination shows that the air bubble at the end of the rectum is above the pubococcygeal line. Both boys and girls often have fistulas, but because the fistulas are very thin, almost all have symptoms of intestinal obstruction. The position of the rectum is higher, above the levator ani muscle, and there is often a defect in the neural control of the pelvic muscles, and it is often accompanied by spinal and upper urinary tract anomalies. Girls often have vaginal fistulas, which are mostly located at the fornix of the posterior vaginal wall. Such children have underdeveloped external genitalia, showing幼稚型.

　　Urinary system fistulas are almost all seen in boys, and are rare in girls. The main symptoms of recto-urinary fistula are exhaust from the external urethral orifice and meconium. Feces in the external urethral orifice or mixed with urine cannot distinguish between bladder fistula or urethral fistula, but by carefully observing the child's urination, a significant difference can sometimes be found. In bladder fistula, as meconium enters the bladder and mixes with urine, the child's urine is green throughout the urination process, and the last part of the urine is darker, and gas accumulated in the bladder can also be excreted. Since there is no sphincter control, feces often flow out from the fistula, which is prone to cause reproductive tract infection. If the bladder area is compressed, more meconium and gas are excreted, and no gas is excreted when not urinating, due to the control of the bladder sphincter muscle. In recto-urethral fistula, only a small amount of meconium is excreted at the beginning of urination, not mixed with urine, and the subsequent urine is transparent. Since there is no sphincter control, exhaust from the external urethral orifice is unrelated to the micturition action.

　　The above symptoms are of great significance for the diagnosis of urinary system fistula, but due to the different sizes of the fistula, or often blocked by thick meconium, the degree of occurrence varies, even completely absent. Therefore, it is necessary to regularly check for meconium components in the child's urine, and a negative urine test does not exclude the existence of urinary system fistula, and multiple checks are necessary.

　　Some cases can be diagnosed by X-ray films, cystography, or the presence of gas or liquid levels in the bladder. The diagnosis is confirmed by the contrast agent filling the fistula opening or entering the rectum.

　　(2) Intermediate position malformation

　　About 15% of these malformations were previously classified as high-level by some people, while others were classified as low-level. In the absence of fistula, the rectal blind end is located at the edge of the bulbocavernosus muscle of the urethra, or near the lower end of the vagina, surrounded by the puborectalis muscle. In the presence of fistula, the fistula tube opens into the bulb of the urethra, the lower segment of the vagina, or the vestibule. The appearance of the anal area is similar to that of high-level malformations, and feces can also be defecated through the urethra or vagina. A probe can pass through the fistula into the rectum, and the tip of the probe can be felt by the finger touching the anal area. On X-ray films, the bubble shadow of the rectal distal end is located below the pubococcygeal line.

　　Girls with recto-vaginal fistula are more common than those with vaginal fistula. The fistula opening is located at the舟状窝part of the vaginal vestibule, also known as the舟状窝fistula. The fistula is large enough to maintain normal defecation, and can develop normally, with incontinence only during loose stools.

　　Anorectal stenosis is a rare malformation, involving the anal and lower rectum, which may be confused with anal stenosis. Fistulography can determine the diagnosis.

　　(3) Low or translevator ani malformations

　　Accounts for about 40% of anorectal malformations. It is caused by the cessation of embryonic late development. The rectum, anal canal, and sphincter develop normally, and the distal end of the rectum is located lower, below the I line. This kind of malformation often has fistulas, but rarely has other associated malformations.

　　The clinical manifestations include some indentations at the normal anal position, with the anal canal completely occluded by a septum. The septum is sometimes very thin, and through it, the meconium retained in the anal canal can be seen, appearing deep blue. When the child cries, the septum is obviously bulging outward, and there is a significant impact when touched with fingers, showing obvious contraction in response to stimulation. Some anal membranes are broken, but not completely, with an aperture of only 2-3mm, causing difficulty in defecation, with the stool becoming thin, like squeezing toothpaste.

　　Some anuses are normal but located in front, between the normal anus and the root of the scrotum or the posterior commissure of the labia, known as perineal anus. Generally, there are no symptoms in clinical practice, and no treatment is necessary.

　　Many children with low-level malformations have anal skin fistulas at the same time as anal atresia, which are filled with meconium and appear deep blue. The fistula opens at the perineum or even further to any part of the scrotum suture or the ventral side of the penis. In girls, the meconium in the hidden fetus is not easy to see, but if a probe is inserted into the fistula orifice, it runs directly backward next to the subcutaneous tissue.

　　In girls, many low-level malformations have an opening in the vulva near the posterior commissure of the labia. Some of them look similar to the normal anus and are called vestibular anus or vulvar anus. Anal vulvar fistula is a variation of the anal septum. In anal vestibular fistula, the intestinal tract has passed through the puborectalis muscle, and the anal canal end passes through a small fistula to communicate with the vestibule. Clinically, the difference from rectal vestibular fistula is that the probe inserted into the fistula orifice slightly moves towards the dorsal side rather than the cranial side, and it is easy to touch the probe tip with fingers when touching the normal anal orifice.

　　(4) Rare malformations

　　In addition, there are some rare malformations, such as perineal cleft in girls, which is a moist epithelial cleft between the anal and vaginal vestibule, as well as rectal vestibular fistulas with a normal anus. Female infants also have rare anorectal malformations, with the external genitalia developing in an infantile type, the labia majora being small, and only one opening, through which urine and feces are excreted.

　　Congenital anorectal malformations are generally caused by developmental abnormalities during the embryonic period, and there are no effective preventive measures. Early detection and early treatment are the key to the prevention and treatment of this disease. Anorectal congenital malformations, as surface malformations, are easy to diagnose. In addition to clinical examination, it is necessary to further measure the distance between the rectal blind end and the levator ani plane and the anal skin to determine the type of malformation, the location of the fistula, and the associated malformations, so as to select the appropriate treatment method.

　　The main differential diagnosis of congenital anorectal anomalies is with rectal atresia. Rectal atresia is a certain distance between the blind end of the rectum and the anal opening, caused by incomplete development of the primitive anus during fetal development. The symptoms are more severe than anal atresia, and the degree of swelling around the anal opening during straining is smaller than that of anal atresia. The main differential diagnosis is with rectal atresia. The following will be introduced on what examinations should be done for congenital anorectal anomalies.

　　1. X-ray

　　The upright abdominal X-ray film often shows low colonic obstruction. In the lateral and anteroposterior films of barium enema, typical spastic and dilated intestinal segments can be seen, with poor barium excretion, and barium residue can still be seen 24 hours later. If barium is not washed out in time, it can form barium stones. When there is concurrent enteritis, the wall of the dilated intestinal segment shows a saw-toothed appearance. The dilated intestinal tube in the neonatal period can be compared to be seen more than half a month after birth. If it still cannot be diagnosed, the following examinations should be performed.

　　2. Biopsy

　　Take a small piece of tissue from the submucosa and muscle layer of the rectum 4 cm above the anal opening, check the number of nerve ganglion cells, and megacolon patients lack ganglion cells.

　　3. Anorectal manometry

　　The measurement of reflexive pressure changes in the rectum and anal sphincter can diagnose congenital megacolon and differentiate constipation caused by other reasons. In normal children and functional constipation, after the rectum is stimulated by distension, the internal sphincter immediately relaxes reflexively, and the pressure decreases. In children with congenital megacolon, the internal sphincter does not relax but contracts significantly, increasing the pressure. This method may sometimes show false-positive results in newborns within 10 days.

　　4. Rectal mucosal tissue chemical examination method

　　This is based on the hyperplasia at the submucosal and muscular nerve ganglion cell deficiency of the spastic segment, the hypertrophied parasympathetic preganglionic fibers continuously release a large amount of acetylcholine and cholinesterase. Both the quantity and activity of these two substances can be determined by chemical methods and are 5 to 6 times higher than those in normal children, which is helpful for the diagnosis of congenital megacolon and can be used for newborns.

　　Congenital anorectal anomalies are congenital diseases, unrelated to diet, normal diet is sufficient. It is recommended to have a light diet, avoid eating greasy, cold, and hard foods, eat more vegetables and fruits to prevent constipation.

　　The purpose of surgical treatment for congenital anorectal anomalies is to reconstruct an anorectal outlet with normal defecation control function. The choice of method and timing is determined by various different types and the presence of fistulas. The treatment principle is to improve the defecation control function after surgery, the protruded rectum must pass through the puborectalis muscle ring. To better identify the puborectalis muscle and urethra, intermediate and high position anomalies can be treated with sacral perineal anorectaloplasty or sacral abdominal perineal anorectaloplasty. During surgery, it is necessary to minimize the injury to the pelvic nerves to enhance sensation, the descended rectum must have good blood supply and reach the perineum without tension. The skin should be sutured into the anal cavity to prevent mucosal prolapse, etc., these are the key points. Whether the surgeon has such a concept will determine whether the prognosis is good. Nowadays, most physicians advocate that for those who are not suitable for perineal anorectaloplasty, a temporary colostomy should be performed at birth, and then an anorectaloplasty should be performed at 6 to 10 months, and the colostomy should be closed after 3 months of surgery.

　　In recent years, the surgical method of posterior sagittal incision created by Penǎ, which separates to the rectal blind end, processes the fistula under direct vision, identifies the location of the muscle group with electrical stimulation, preserves the rectal and perianal muscle, nerve, and vascular tissues, and restores them to their original state. If the rectum is too short or too wide, free the abdomen and perform caudal trimming to ensure that the rectal blind end accurately passes through the central puborectalis and sphincter muscle group, thus achieving satisfactory defecation function.

　　As for the treatment of low-lying deformities, if there is no stricture in the anal skin fistula and no obstruction in defecation function, no treatment is needed. For mild stricture at the lower end of the anal or rectum, dilation surgery is generally used to restore normal function. For those with anal skin fistula, only a simple "posterior incision" surgery is performed. Membranous anal atresia is treated with perineal anorectal plastic surgery in the neonatal period. For anal vestibular fistula, if the fistula opening is large, normal defecation can be maintained for a period of time, and surgery can be performed after 6 months. For low-lying cases, as they have passed through the puborectalis muscle ring, surgery is relatively easy and the defecation function is good after surgery. As for the treatment of cloacal deformities, due to the complexity of the single anal atresia, a temporary colostomy is first performed in the neonatal period, and radical surgery is performed between 6 months and 1 year. The vaginal成形术 is performed by creating a skin tube or pedicle small intestine transplant, and abdominal perineal anorectal plastic surgery is performed behind the new vagina to form part of the urinary system organs, striving to complete the operation in one stage.

　　Evaluation of Defecation Function

　　The criteria for past records were inconsistent, making it difficult to make a unified evaluation. Now, it is recommended to classify the four types of scores according to the cleanliness of the perineum after surgery: clean, fecal contamination, incomplete incontinence, and complete incontinence. In each item, record whether there is fecal retention according to the rectal emptying function, and indicate whether treatment is required. Any other deformities or complications found during surgery must be recorded item by item, as they may become important factors affecting the score.