Congenital Anal-Rectal Malformation

　　The occurrence of congenital rectal anal malformations is the result of malformation during the embryonic development period, and there is basically no difference between males and females, with only anatomical differences. This condition is also the result of the separation process of the cloaca, with communication between the urogenital sinus and the anal-rectal sinus, forming high or intermediate position malformations, and leading to various incomplete anal-rectal developments and fistulas between the rectum and the urethra or vagina. Obstruction in the posterior movement of the anus and incomplete perineal development can result in this condition, forming low position malformations, such as anal skin fistulas, anal vestibular fistulas, and anal stenosis.

　　Patients with congenital anal-rectal malformations may present with complications such as acute complete low intestinal obstruction symptoms, and patients with anal-rectal stenosis may experience difficulties in defecation, constipation, fecal stone formation, and secondary megacolon, among other chronic obstructive symptoms. This condition often leads to hypochloremic acidosis in children with low intestinal obstruction, and severe cases may be accompanied by shock and death. Patients may also develop megacolon, nutritional disorders, and complications such as vulvitis and urinary tract infections.

　　After the birth of infants with congenital anal-rectal malformations, some can be found to have no anus at the normal anal position by careful observation of the perineum, especially if the meconium is not defecated within 24 hours after birth, it should be checked in time. If it can be detected early, its clinical manifestations are symptoms of varying degrees of low intestinal obstructionThat is, abdominal pain, vomiting, abdominal distension, without defecation and anal exhaust.. In cases without fistulas or with narrow fistulas, acute complete low intestinal obstruction symptoms often occur in the early stage after birth. In cases of anal-rectal stenosis or accompanied by larger fistulas, depending on the degree of stenosis and the size of the fistula, defecation difficulties, constipation, fecal stone formation, secondary megacolon, and other chronic obstruction symptoms may appear in a few weeks, months, or even years. According to the type of malformation, the specific clinical manifestations of this disease are as follows:

　　1, High malformation

　　About 40%, more common in boys, often with fistulas present, but due to the small size of the fistulas, almost all have symptoms of intestinal obstruction. There is often a defect in the neural supply of the pelvic muscles, and it is accompanied by sacral and upper urinary tract malformations. In this type of case, at the normal anal position, the skin is slightly concave, and the pigmentation is deeper, but there is no anus. During crying, the concave part does not bulge outwardly, and there is no冲击感 when touched with fingers. Girls often have vaginal fistulas, opening at the posterior fornix of the vagina. The external genitalia are also underdeveloped,呈幼稚型, and feces often flow out through the fistula, easily causing genital tract infection. Boys often have urinary tract fistulas, with gases and meconium excreted from the urethral orifice, which can cause recurrent urethritis, glans penis inflammation, and upper urinary tract infection.

　　2, Intermediate malformation

　　About 15%. In those without fistulas, the rectal blind end is located adjacent to the bulbous corpus cavernosum of the urethra or the lower segment of the vagina, surrounded by the puborectalis muscle. In those with fistulas, the fistula opening is at the bulbous corpus cavernosum, lower segment of the vagina, or vestibule. The appearance of the anal area is similar to that of high malformations, and defecation can also occur through the urethra or vagina. The probe can be inserted into the rectum through the fistula orifice, and the tip of the probe can be felt in the perineum. In girls, rectal vestibular fistulas are more common, as the fistula orifice is located in the navicular fossa of the vaginal vestibule, also known as navicular fossa fistula. The fistula orifice is large, and the baby can basically maintain normal defecation through the fistula in the early stage of life, which can cause vulvitis or ascending infection.

　　3, Low malformation

　　About 40%. The distal rectum is located lower, often accompanied by fistulas, and rarely associated with other malformations. Some have a thin film covering the normal anal position, with a faint color of meconium visible, and the diaphragm bulges outwardly明显 during crying. Sometimes the anal membrane is broken but not completely, and defecation is difficult. In boys, anal skin fistulas are present, filled with meconium and appear deep blue, with the fistula orifice located in the perineum, or even further anterior to the scrotal suture, or at any part of the tail side of the urethra. In girls, there are anterior vaginal fornix fistulas or skin fistulas, with the fistula orifice located in the anterior vaginal fornix or perineum.

　　The congenital anomaly of this disease is not clear, and it may be related to environmental factors, genetic factors, dietary factors, and emotional and nutritional factors during pregnancy. Therefore, it is not possible to prevent the disease directly. Early detection, early diagnosis, and early treatment are of great significance for preventing the disease. Regular check-ups during pregnancy should be done, and if the child shows a tendency of developmental abnormalities, timely checks should be made to clarify.

　　Congenital rectal anal anomalies are easily diagnosed due to their surface deformities. In addition to clinical examination, it is necessary to further measure the distance from the rectal blind end to the pelvic floor muscle plane and the distance from the anal skin to determine the type of anomaly, the position of the fistula, and the associated anomalies. The specific methods of these examinations are as follows:

　　1. Peripheral blood

　　When there are symptoms of infection and systemic toxicity, peripheral blood leukocytes and neutrophils increase, and there may be a decrease in platelet count and other manifestations.

　　2. Blood biochemistry

　　When complications such as dehydration and acidosis occur, routine blood tests for sodium, potassium, chloride, calcium, blood pH value, blood urea nitrogen, and creatinine are required.

　　3. Urinalysis

　　The child's urine contains meconium components.

　　4. Supine lateral X-ray film

　　It is required to take photos more than 12 hours after birth, waiting for the gas to reach the rectum. Children with poor vitality need more time. Apply barium paste to the perineal anal area of the skin as a marker. Invert the infant for 2-3 minutes before taking photos to allow the meconium at the rectal blind end to exchange with the intestinal gas. Adopt the hip joint in a 90° flexion position to ensure that the angle between the points P (pubic center), C (sacral coccygeal joint), and I (lowest point of the ischium) can be fully displayed. With the center of the greater trochanter of the femur, take a photo at each of the expiration, inspiration, and crying. Through the I point, set an I line parallel to the PC line, and the distance between the PC line and the I line is the pelvic floor muscle group. The rectal blind end located above the PC line is high, between the two lines is intermediate, and beyond the I line is low. Alternatively, set the M point, which is the junction of the upper two-thirds and lower one-third of the ischial tuberosity. The position above the M line is intermediate, and the position below the M line is low. However, attention must be paid to various influencing factors, such as insufficient intestinal gas, excessively sticky meconium, pelvic floor muscle movement, and X-ray projection angle bias, all of which can affect the accuracy of the position.

　　5. Fistula contrast study

　　The contrast study of the fistula requires the display of the colonic image at the time of contrast medium injection and the rectal fistula image at the time of contrast medium excretion. Double-contrast colonic and rectal urethral imaging can show the relationship between the rectal fistula and the urethra, and vaginal contrast imaging can show the relationship between the vagina and the rectum.

　　6. CT

　　It can display the development status and direction of the pelvic floor muscle group, and can also be used as a reference for postoperative follow-up. In normal children, the CT shows the puborectalis muscle as a soft tissue mass, fixed in front of the pubis, and connected to the sides and posterior wall of the rectum, the internal and external anal sphincters form an oval mass, which is difficult to separate. Children with different types of anal rectal anomalies have different CT findings, such as rectourethral fistula, the puborectalis muscle surrounds the urethra and rectal blind end, and the anal sphincter is located directly below the perineum.

　　7. B-ultrasound examination

　　Not limited by time, no special preparation is required before the examination. This method is safe and simple, the measured data is reliable, the error is smaller than that of X-ray, it can be repeated, and the pain to the child is minimal.

　　8, Magnetic Resonance Imaging (MRI)

　　The application of magnetic resonance imaging (MRI) in anal rectal malformations can observe the changes in the anal peripheral muscle groups, and at the same time, it can judge the type of malformation and whether the sacrum and coccyx are malformed.

　　Patients with congenital anal rectal malformations should have a light diet, avoid eating greasy, cold, and hard foods, eat more vegetables and fruits to prevent constipation. Patients should eat high collagen, high zinc, and diuretic foods. Avoid eating hot, spicy, and irritating foods.

　　The surgical treatment method for congenital anal rectal malformations, the purpose of surgical treatment is to reconstruct an anal sphincter with normal defecation control function. The choice of method and time is determined according to various different types and the condition of associated fistulae. The principle of treatment is to improve the defecation control function after surgery, and the protruded rectum must pass through the puborectalis muscle ring. To better identify the puborectalis muscle and urethra, intermediate and high-level malformations can be treated with sacral tail anal plastic surgery or sacral abdominal perineal anal plastic surgery. To minimize the injury to the pelvic nerves during surgery to enhance sensation, the prolapsed 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 and other issues. These are the key points, and whether the surgeon has such a concept will determine whether the prognosis is good. Nowadays, most doctors advocate that for those who are not suitable for perineal anal plastic surgery, a temporary colostomy should be performed first at birth, and anal plastic surgery should be performed between 6 to 10 months, and the colostomy should be closed 3 months after surgery.

　　As for the treatment of low-level malformations, such as anal skin fistula without stricture and no impairment of 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 patients 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 is large, normal defecation can still be maintained for a period of time, and surgery can be performed after 6 months. Low-level malformations are easier to operate on because they have passed through the puborectalis muscle ring, and the defecation function is good after surgery. As for the treatment of cloacal malformations, due to the complexity of one-hole anal malformation, a temporary colostomy is first performed in the neonatal period, and radical surgery is performed between 6 months and 1 year.