The anus Rectum and Anus The rectum is a chamber that begins at the end of the large intestine, immediately following the sigmoid colon, and ends at the anus (see also Overview of the Anus and Rectum). Ordinarily, the... read more is the opening at the far end of the digestive tract through which stool leaves the body. The rectum Rectum and Anus The rectum is a chamber that begins at the end of the large intestine, immediately following the sigmoid colon, and ends at the anus (see also Overview of the Anus and Rectum). Ordinarily, the... read more is the pouch of large intestine that holds stool prior to defecation. In anorectal malformations, skin may be covering the area where the anus should be, and the skin may be several centimeters thick or just a thin membrane. The opening to the anus may be narrow or may be missing completely.
Anal atresia occurs when the intestines do not develop properly while the fetus is growing. It is not known why the intestines do not develop properly.
Most infants with anal atresia develop some type of abnormal connection (fistula) between the anus and either the urethra, the area between the urethra and anus (the perineum), the vagina, or rarely the bladder. Anal atresia commonly occurs along with other birth defects, such as defects of the spine, heart Overview of Heart Defects About one in 100 babies is born with a heart defect. Some are severe, but many are not. Defects may involve abnormal formation of the heart's walls or valves or of the blood vessels that enter... read more , kidneys Kidney Defects There are several different birth defects that affect the kidneys (the two organs that filter waste from the blood to make urine). These defects are not usually apparent at the doctor's examination... read more , and limbs Missing or Incompletely Formed Limbs Limbs can be missing, deformed, or incompletely developed at birth. Limbs may form abnormally. For example, bones in the hand and forearm may be missing because of a genetic defect (see Chromosome... read more . Affected infants may also have tracheoesophageal fistula Esophageal Atresia and Tracheoesophageal Fistula Esophageal atresia is a birth defect in which the esophagus narrows or comes to an end. Most newborns with esophageal atresia also have an abnormal connection between the esophagus and the windpipe... read more and esophageal atresia Esophageal Atresia and Tracheoesophageal Fistula Esophageal atresia is a birth defect in which the esophagus narrows or comes to an end. Most newborns with esophageal atresia also have an abnormal connection between the esophagus and the windpipe... read more .
Infants with anal atresia do not defecate normally after birth. Eventually, if the defect is not treated, intestinal obstruction Intestinal Obstruction An obstruction of the intestine is a blockage that completely stops or seriously impairs the passage of food, fluid, digestive secretions, and gas through the intestines. The most common causes... read more develops. Intestinal obstruction is a blockage that completely stops or seriously impairs the movement of material in the intestines. Symptoms of intestinal obstruction in infants include pain, irritability, vomiting, and a swollen abdomen.
(See also Overview of Digestive Tract Birth Defects Overview of Digestive Tract Birth Defects The digestive organs may be incompletely developed or abnormally positioned, causing blockages, or the muscles or nerves of the digestive tract may be defective. Symptoms depend on the location... read more .)
Doctors often detect the malformation by looking at the anus when they first examine the baby after birth, before symptoms develop.
Using x-rays X-Ray Studies of the Digestive Tract X-rays often are used to evaluate digestive problems. Standard x-rays (plain x-rays) do not require any special preparation (see Plain X-Rays). These x-rays usually can show a blockage or paralysis... read more , a radiologist can see the location of and determine other details about a fistula. Doctors may also do an ultrasound to determine the type of malformation and to look for other defects.
Anal atresia usually requires immediate surgery to create a passage for stool and to close the fistula. However, sometimes infants first have a surgical procedure called temporary colostomy (see figure Understanding Colostomy Understanding Colostomy Anorectal malformations are birth defects in which the opening of the anus is narrow, covered with skin, or missing. Infants may develop intestinal obstruction. The diagnosis is based on a physical... read more ). In this procedure, the surgeon makes a hole in the abdominal wall and connects it to the colon to allow stool to flow into a plastic bag on the abdominal wall. The colostomy stays in place until the infant is older and the structures that need to be repaired have grown larger. The colostomy is closed when surgery to fully repair the defect is done.