You are in: eMedicine Specialties > Pediatrics: Surgery > General Surgery Imperforate Anus: Surgical PerspectiveArticle Last Updated: Aug 10, 2007AUTHOR AND EDITOR INFORMATIONSection 1 of 12
  Author: Marc A Levitt, MD, Assistant Professor of Surgery and Pediatrics, University of Cincinnati; Associate Director, Colorectal Center for Children, Department of Pediatric Surgery, Cincinnati Children's Hospital Medical Center Marc A Levitt is a member of the following medical societies: Alpha Omega Alpha, American College of Surgeons, and Society of American Gastrointestinal and Endoscopic Surgeons Coauthor(s): Alberto Pena, MD, Consulting Surgeon, Colorectal Center for Children, Department of Pediatric Surgery, Cincinnati Children's Hospital Medical Center Editors: Robert Kelly, MD, Chairman, Department of Surgery, Departments of Surgery and Pediatrics, Children's Hospital of the King's Daughters; Associate Professor, Eastern Virginia Medical School; Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine.com, Inc; Deborah F Billmire, MD, Associate Professor, Department of Surgery, Indiana University Medical Center; H Biemann Othersen Jr, MD, Professor of Surgery and Pediatrics, Emeritus Head, Division of Pediatric Surgery, Medical University of South Carolina; Marleta Reynolds, MD, Professor of Surgery, Feinberg School of Medicine, Northwestern University; Interim Head, Division of Pediatric Surgery, Department of Surgery, Children's Memorial Hospital of Chicago Author and Editor Disclosure Synonyms and related keywords: imperforate anus, anorectal malformations, anorectal anomaly, persistent cloaca, rectoperineal fistula, bucket-handle malformation, recto–bladder neck fistula, rectobladder neck fistula, bowel control, anoplasty, colostomy, rectobulbar urethral fistula, rectoprostatic urethral fistula, rectovesical fistula, imperforate anus without fistula, rectal atresia, rectovestibular fistula, rectovaginal fistula, urinary fistula, urinary tract malformation, colostography, rectovesical defect, rectoperineal, tethered cord, sacral defect, spinal defect, descending colostomy with separated stomas, fecal diversion, megarectum, posterior sagittal approach, constipation, megasigmoid INTRODUCTIONSection 2 of 12
  Anorectal malformations comprise a wide spectrum of diseases that affect boys and girls and can involve malformations of the distal anus and rectum, as well as the urinary and genital tracts. Malformations range from minor, easily treated defects that carry an excellent functional prognosis, to complex defects that are difficult to treat, are often associated with other anomalies, and carry a poor functional prognosis. History of the ProcedureThroughout the centuries, doctors have seen and attempted to treat babies born with imperforate anus. Because few patients have been described in the early literature, most are assumed to have died without treatment. Paulus Aegineta recorded the earliest account of successful surgery for imperforate anus. He suggested rupturing an obstructing membrane with the finger or knifepoint and then dilating the tract until healing was complete. This approach was used for many years. Almost 1000 years later, in 1660, Scultet used dilatation to treat an infant with anal stenosis. In 1676, Cooke used incision and dilatation and advised care of the sphincter muscles. In 1787, In 1835, Amussat described formal perineal proctoplasty (ie, mobilization of the bowel through a perineal incision and suturing to the skin). This technique gained rapid acceptance. Strictures were less common than observed in earlier procedures. In addition to Amussat, Dieffenbach described anal transposition (1826); Chassaignac used a probe through a stoma to guide the perineal dissection (1856); and Leisrink (1872), McLeod (1880), and Hadra (1884) recommended opening the peritoneum if the bowel was not encountered from below. In 1930, Wangensteen and Rice first advocated imaging to delineate the abnormality. Single-stage abdominoperineal procedures became widely used after reports by Rhoads, Pipes, Randall, Norris, Brophy, and Brayton (1948-1949). In 1953, Stephens described this procedure and emphasized preservation of the puborectalis muscle. This surgery and its modifications were the standard approach until 1980. In 1980, the surgical approach to repairing anorectal malformations altered dramatically with the introduction of the posterior sagittal approach. This approach allowed pediatric surgeons to clearly view the anatomy of anorectal malformations and to repair them under direct vision, with better visualization and understanding of the anatomy than previous approaches allowed. Surgeons were able to understand the complex anatomic arrangement of the rectum-genitourinary tract junction. FrequencyAnorectal malformations occur in approximately 1 per 5000 live births. EtiologyAlthough the etiology remains unknown, a slight genetic predisposition appears to exist. PathophysiologyUnderstanding the true anatomy is helpful to prevent damage to important structures during surgical repair and to preserve the best potential for bowel control. Anatomic visualization has allowed surgeons to eliminate many previous misconceptions. For instance, the previous classification of these defects into high, intermediate, and low malformations was a misleading oversimplification that did not adequately demonstrate the spectrum of anorectal anomalies. Improved imaging techniques and a more thorough knowledge of the anatomy and physiology of the pelvic structures at birth have refined diagnosis and early treatment. Analysis of large series of patients has allowed better prediction of associated anomalies and functional prognosis. The surgeon’s primary concern in correcting these anomalies is bowel control. Although uncommon, problems with urinary control and sexual function must also be considered. Early diagnosis, treatment of associated anomalies, and efficient and meticulous surgical repair provide patients the best chance for a good functional outcome. Some patients experience fecal and occasional urinary incontinence despite excellent anatomic repair. Associated problems such as a poorly developed sacrum, nerve supply, and spinal cord likely contribute to an inability to achieve continence. For patients with fecal incontinence, an effective bowel management program has been devised to improve quality of life (see Bowel Management). ClinicalDiagnosis and early treatment For neonates born with an anorectal anomaly, early treatment is crucial. During the first 24-48 hours of life in a newborn with an anorectal malformation, the following 2 questions should be answered:
The surgeon must also determine whether female neonates have a dilated vagina, if it should be drained, and whether urinary diversion is required. These maneuvers are intended to prevent sepsis and metabolic acidosis (see Cloacal Malformations). The decision to perform an anoplasty during the newborn period or to delay the repair and perform a colostomy is based on physical examination findings in the newborn, the appearance of the perineum, and changes that occur during the first 24 hours of life. Operating earlier and in a single stage is potentially beneficial to the patient, but this should be decided carefully, based on the specific circumstances of the newborn and the experience of the surgeon. A more conservative approach is warranted in neonates with low birth weight and associated cardiac or respiratory conditions. The indications for colostomy compared with anoplasty based on sex are as follows:
Decision-making in newborn boys with anorectal anomalies In 80-90% of newborn boys, clinical evaluation and urinalysis provide enough information for the surgeon to decide whether a colostomy is required. After birth, an intravenous line is placed for fluids and antibiotics. A nasogastric tube is inserted to keep the stomach decompressed to avoid the risk of vomiting and aspiration. Meconium is not usually observed at the perineum in a newborn with rectoperineal fistula until at least 16-24 hours of life. Abdominal distension does not develop during the first few hours of life but is required to force meconium through a rectoperineal fistula, as well as through a urinary fistula. This is because the most distal part of the rectum in these children is surrounded by a funnel-like voluntary muscle structure that keeps part of the rectum collapsed and empty. The intra-abdominal pressure must be high enough to overcome the tone of the muscles that surround the rectum to force meconium through the fistula. Therefore, the decision to perform a colostomy or an anoplasty must be delayed for 16-24 hours while the surgeon evaluates for clinical evidence of the newborn’s anorectal anomaly. Clinical inspection of the buttocks is important. A flat bottom or flat perineum, as evidenced by the lack of a midline gluteal fold and the absence of an anal dimple, indicates that the patient has poor muscles in the perineum. These findings are associated with a high malformation; therefore, a colostomy should be performed. Perineal signs found in patients with low malformations include the presence of meconium at the perineum, a bucket-handle malformation (ie, a prominent skin tag located at the anal dimple, below which an instrument can be passed), and an anal membrane (through which meconium is visible). Newborn boys with rectoperineal fistula do not require a colostomy. They can undergo a posterior sagittal anoplasty. Newborn boys with evidence of a rectourinary tract communication should undergo fecal diversion with a colostomy. If none of the clinical signs to reveal the location of the anorectal anomaly are evident by 24 hours, obtaining radiographs can help. This situation is necessary in only approximately 10% of patients. Obtain cross-table lateral radiographs with the newborn prone, with the pelvis elevated, and with a radiopaque marker placed on the perineum (see Image 3). Rarely, radiography reveals the column of air in the distal rectum to be within 1 cm of the perineum; in these instances, treatment is similar to that for rectoperineal fistula, and a newborn perineal operation may be performed. If the air column is more than 1 cm from the perineum, a colostomy is indicated. Some authors have performed definitive repair in the newborn period. Advantages to this approach include avoiding colostomy and repairing the malformation earlier; however, because the surgeon does not know the precise anorectal defect, the urinary tract is at considerable risk. To definitively determine the patient's anorectal defect, perform distal colostography, which requires the presence of a colostomy. Without this information, an operation in the newborn period is, essentially, a blind perineal exploration. The surgeon may not be able to locate the rectum and may find and damage other unexpected structures (eg, posterior urethra, seminal vesicles, vas deferens, ectopic ureters) during the search for the rectum. Finally, without fecal diversion, the risk of dehiscence and infection exists. These complications may compromise the chance of achieving bowel function. The rare exception occurs when the cross-table lateral radiograph obtained at 16-24 hours reveals that the rectum is located just below the coccyx. In this case, the rectum may be reached from the posterior sagittal approach. Obtain urinalysis and place gauze over the penis to reveal the presence of fecal matter in the urine, which is considered evidence of a rectourinary fistula. Abdominal ultrasonography must be performed to evaluate for the presence of an obstructive uropathy. At the same time, spinal ultrasonography may be performed to evaluate for spinal anomalies, including the presence of a tethered cord. Methods to reveal the location of the distal rectum before 16 hours of life are flawed because of the contracted state of the funnel-like sphincter mechanism. Typically, the funnel-shaped muscle structure is contracted unless overcome with a distending force. Tests such as MRI, ultrasonography, CT scanning, or injection of contrast through the perineum falsely locate the distal rectum as high in the pelvis. Distal colostography (typically obtained 1 mo after colostomy opening) must have adequate pressure to demonstrate a fistula from the rectum to the urinary tract. If pressure is inadequate, this method also falsely locates the distal rectum as high in the pelvis. Once the patient recovers from colostomy and demonstrates good growth and development, the definitive operation can be planned 4-8 weeks later. Decision-making in newborn girls with anorectal anomalies The decision to perform colostomy in newborns girls is less complicated in newborn girls. In 90% of patients, a meticulous perineal inspection demonstrates the anorectal defect. Waiting 16-24 hours for enough abdominal distension to demonstrate the presence of a rectoperineal fistula or rectovestibular fistula also applies to newborn girls. The most common anomaly in newborn girls is a rectovestibular fistula. Perineal inspection reveals a typical urethra, typical vagina, and another orifice, which is the rectal fistula in the vestibule. In newborns with clinical evidence of a rectovestibular fistula, a diverting colostomy is the safest option for surgeons without extensive experience in anorectal anomalies. Colostomy prior to the main repair avoids the complications of infection and dehiscence. Definitive repair of this anomaly in the newborn period should be reserved for surgeons who have significant experience repairing these defects. Once this anomaly is repaired, patients have an excellent prognosis; therefore, complications that may affect continence must be avoided. Patients with rectovestibular fistulas in whom primary repair failed in the newborn period are the most common referrals for re-operations to tertiary centers that care for anorectal anomalies. Occasionally, the fistulas are large enough to decompress the gastrointestinal tract. They may be dilated to facilitate fecal drainage until the baby is older and a definitive repair is performed. Definitive repair involves a posterior sagittal approach. The most delicate part of this operation is the separation of the rectum and vagina, which share a common wall. As in boys, newborn girls may also have a rectoperineal fistula, which requires an anoplasty procedure in the newborn period. Similar to boys, the rectum location is not clinically evident in less than 5% of newborn girls after 24 hours. They may have imperforate anus with no fistula. Cross-table lateral radiography should be performed, which helps determine the need for a colostomy. The presence of a single perineal orifice in a patient is clinical evidence of persistent cloaca (see Image 4). Patients with these anomalies also have small genitalia. See Cloacal Malformations for details regarding treatment of persistent cloaca. In patients with persistent cloaca, abdominal examination may reveal a mass that likely represents a distended vagina (hydrocolpos), which is present in 50% of patients with persistent cloaca. Abdominal ultrasonography is helpful to reveal the presence of an obstructive uropathy and hydrocolpos. During the perineal inspection, newborn girls are commonly given an incorrect diagnosis of imperforate anus with rectovaginal fistula; however, all 3 structures (ie, urinary tract, vagina, rectum) actually meet in a common channel, and the baby has persistent cloaca. This misconception carries important therapeutic implications. Making the correct determination is vital, because 90% of newborns with persistent cloaca have an associated urologic problem and 50% have hydrocolpos. The urinary tract and distended vagina both may require treatment in the newborn period to avoid serious complications. Missing the diagnosis of persistent cloaca commonly means that an obstructive uropathy is overlooked. The patient may then receive only a colostomy, resulting in subsequent sepsis, acidosis, and, occasionally, death. The other implication of missing the diagnosis of persistent cloaca involves repairing only the rectal component of the anomaly, leaving the patient with a persistent urogenital sinus. Types of urinary tract malformations are as follows:
INDICATIONSSection 3 of 12
See Colostomy versus anoplasty. RELEVANT ANATOMYSection 4 of 12
See Pathophysiology. CONTRAINDICATIONSSection 5 of 12
No absolute contraindications to surgery exist. The presence of associated malformations, such as prematurity and congenital cardiac disease, often postpones definitive colorectal reconstruction. WORKUPSection 6 of 12
Imaging Studies
TREATMENTSection 7 of 12
Medical therapyAssociated malformations
Surgical therapyAs discussed above, the surgeon must decide in the newborn period whether the child requires fecal diversion with a colostomy or if a primary procedure is possible. Colostomy
Definitive repair
Postoperative detailsPostoperative management The posterior sagittal incision is relatively painless. In patients with a rectourethral fistula, the Foley catheter usually stays in place for approximately 5-7 days. Occasionally, a longer period is required. If the colostomy is untouched during the operation and laparotomy was not necessary, oral feedings may be started immediately postoperatively. If a laparotomy was necessary, the patient may require a period of fasting and nasogastric decompression. At 2 weeks' postsurgery, anal calibration is performed, followed by a program of anal dilatations. The anus must be dilated twice daily, and the size of the dilator is increased every week. The final size to be reached depends on the patient’s age. Once the desired size is reached, the colostomy may be closed. Dilatations are continued afterward according to a prescribed protocol. Dilatations are a vital part of postoperative treatment to avoid an anoplasty stricture. After colostomy closure, severe diaper rash is common, because the perineal skin has never before been exposed to stool. Postoperative functional disorders Constipation is the most common problem encountered after treatment for imperforate anus with rectal preservation. Constipation is the most important problem to avoid after definitive repair in newborn girls with rectovestibular or rectoperineal fistula and in newborn boys with rectobulbar urethral fistula, imperforate anus without fistula, and rectoperineal fistula. Failure to avoid constipation may result in megarectum and megasigmoid and can lead to fecal impaction and overflow incontinence. See Bowel Management for further discussion.The origin of the constipation problem is unknown. Originally, the perirectal dissection was believed to cause a degree of denervation that resulted in constipation. However, on careful review of the largest patient series, those with the most benign defects (ie, the least amount of perirectal dissection) experienced the worst constipation. The presence of a megarectum prior to the pull-through procedure correlates with postoperative constipation. Megarectum is more common in patients who underwent a transverse or loop colostomy during the newborn period. Constipation appears to be a hypomotility disorder secondary to chronic bowel dilatation; alternatively, the hypomotility may cause the dilatation. Dilatation causes constipation, creating a vicious cycle. Patients who have undergone abdominoperineal operations for imperforate anus that included rectum resection are prone to develop diarrhea because of lack of a rectal reservoir. Incontinence in these patients is much more difficult to treat because stool is constantly passed (see Bowel Management). Occasionally, constipation becomes so severe that patients develop chronic fecal impaction and constant soiling. These patients are often referred to as having fecal incontinence. However, if the patient has a type of anorectal anomaly with a good prognosis, this incontinence is often overflow pseudoincontinence. Once the constipation is treated, the patient regains continence. When constipation is severe and the patient has a megasigmoid (and the patient is fecally continent), resection of the sigmoid has been found to dramatically reduce the patient's laxative requirements. The descending colon with typical caliber and motility is anastomosed to the rectum at the peritoneal reflection. This procedure is for the select group of patients who require enormous amounts of daily laxatives to keep their colons clean. A new pull-through operation should be avoided to preserve the rectal reservoir. Loss of the rectal reservoir may lead to the worse problem of diarrhea-related incontinence. Follow-upThe key in these patients is to treat constipation proactively and avoid it after the pull-through procedure. Patients must be regularly monitored, and laxatives and dietary manipulations are begun at the first sign of constipation. The child’s bowel movement pattern before toilet-training may provide important information concerning the potential for continence. For example, a 1-year-old child who has undergone a pull-through procedure for imperforate anus and has 1-3 bowel movements per day with no soiling accidents has high potential for future fecal continence. Signs of feeling are demonstrated while the child is pushing during a bowel movement. On the other end of the spectrum, a child who has fecal incontinence passes stool constantly without evidence of pushing or feeling. A child with a typical bowel movement pattern is trainable, whereas a child with the pattern of fecal incontinence likely requires a bowel-management program. The child with fecal incontinence should not be expected to achieve voluntary bowel control. COMPLICATIONSSection 8 of 12
Complications of surgery include dehiscence and infection, which may be avoided with colostomy before the main repair. Some authors have performed definitive repair in the newborn period. The advantages to this approach include avoiding a colostomy and repairing of the malformation earlier; however, with this practice, the urinary tract is at considerable risk because the surgeon does not know the precise anorectal defect. The only way to definitively determine the patient's anorectal defect is to perform distal colostography, which requires the presence of a colostomy. Without this information, an operation in the newborn period is, essentially, a blind perineal exploration. The surgeon may not be able to locate the rectum; during the search, he or she may find and damage other unexpected structures, such as the posterior urethra, seminal vesicles, vas deferens, and ectopic ureters. Finally, without fecal diversion, the risk of dehiscence and infection exists. These complications may compromise the chance of achieving typical bowel function. OUTCOME AND PROGNOSISSection 9 of 12
When evaluating the results of treatment of anorectal defects, patients cannot be grouped into the traditional high, intermediate, and low categories. For instance, within the traditional high group, malformations have different treatments and carry different prognoses (eg, rectoprostatic fistula compared with rectobladder neck fistula). Both of these would be considered high in the traditional nomenclature; however, the malformations are so different they should not be grouped together. An anatomic classification is of more clinical value. The functional results of repair of anorectal anomalies have improved significantly since the advent of the posterior sagittal approach. However, the results of this approach are difficult to compare with those of other methods because terminology and classification are inconsistent. Approximately 75% of all patients with anorectal malformations have voluntary bowel movements. Approximately 50% have occasional soiling accidents. Episodes of soiling are usually related to constipation; when constipation is treated properly, the soiling commonly disappears. Approximately 40% of all patients have voluntary bowel movements and no soiling. About 25% of patients with anorectal malformations have fecal incontinence and must receive a bowel management regimen to keep clean (see Bowel Management).Apart from the anorectal anomaly, the status of the sacrum, spine, and muscles greatly affects a patient's fecal continence. Even with a perfect reconstruction, a patient with a poor sacrum may not achieve bowel control. Bowel control must be evaluated when the child is older than 3 years. The need for laxatives, medications, special diet, and enemas must be considered when assessing outcomes. Patients with low defects (eg, rectoperineal fistula, rectal atresia) have excellent outcomes. Girls with vestibular fistulas have very good outcomes, except for a tendency to develop constipation. Approximately 60% of boys with rectourethral fistulae and typical sacra have good outcomes. More than 80% of patients with persistent cloaca and a typical sacrum have bowel control. Patients with very high malformations (eg, rectobladder neck fistula in boys) have poor outcomes, even with a typical sacrum. The sacrum is a good predictor of outcome. Patients with a typical sacrum are much more likely to have fecal continence. Patients with a hypodeveloped sacrum are much more likely to be incontinent. A sacral ratio has been developed to allow for a more objective assessment of the sacrum (see Image 8). Thus far, no patients with a sacral ratio less than 0.3 have achieved continence. A hypodeveloped sacrum is also a good predictor of associated spinal problems, such as tethered cord. A child's outcome may be predicted more accurately with the knowledge obtained from a large patient series. Parents can be realistically informed of their child's potential for bowel control, even in the newborn period. This avoids a great deal of frustration later in life. Establishing the functional prognosis early is vital to avoid raising false expectations in the parents. Once the diagnosis of the specific defect is established, the functional prognosis can be predicted. The status of the spine, sacrum, and perineal musculature are all factors that affect the counseling given to the parents. If a given defect carries a good prognosis, such as vestibular fistula, perineal fistula, rectal atresia, rectourethral bulbar fistula, or imperforate anus without fistula, expect the child to have voluntary bowel movements by age 3 years. Such children require supervision to avoid fecal impaction, constipation, and soiling. Certain defects indicate a poor prognosis, such as a high cloaca (common channel >3 cm) or a rectobladder neck fistula. Parents should be informed that the child may require a bowel management program to remain clean. The program should be implemented at age 3-4 years (see Bowel Management). Patients with rectoprostatic fistulas carry an almost equal chance of voluntary bowel movements or incontinence. Toilet training should be attempted at age 3 years, and, if unsuccessful, a bowel management program should be initiated. Each year, during summer vacation, bowel control should be attempted, and, if unsuccessful, the bowel management should be restarted. As the child grows older and more cooperative, the likelihood of achieving bowel control improves. Urinary incontinence occurs in boys with anorectal malformations only when they have an extremely defective or absent sacrum or when the basic principles of surgical repair are not followed and important nerves are damaged during the operation. The vast majority of boys have urinary control. This is also true for girls, not including the group with persistent cloaca (see Cloacal Malformations). Careful, regular observation is necessary in these patients to accurately reassess their prognosis and to avoid problems that can dramatically affect their ultimate functional results. FUTURE AND CONTROVERSIESSection 10 of 12
Potential methods of evaluation for anorectal malformations, including prenatal diagnosis and genetic karyotyping to reveal familial disposition, remain controversial. MULTIMEDIASection 11 of 12
REFERENCESSection 12 of 12
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