Pediatric Imperforate Anus (Anorectal Malformation) Treatment & Management

Proper consultation and surgical management are important. Transferring these patients to a facility that provides pediatric surgical care aids in proper classification, diagnosis, and management. Optimal resources for the care of these children includes a pediatric surgeon with experience in anorectal malformations, a pediatric urologist, a pediatric anesthesiologist, a critical care specialist, and a neonatologist.

Newborns with imperforate anus should not be fed and should receive intravenous hydration. Life-threatening comorbidities take precedence and must be treated first.

If a urinary fistula is suspected, broad-spectrum antibiotics can be administered, although anaerobic coverage is unnecessary within the first 48 hours of life. Any cardiac murmurs identified upon physical examination should be evaluated using echocardiography prior to surgical intervention. The remainder of treatment includes diagnostics and surgical evaluation and management.

Postoperative management

After initial colostomy, the child is able to eat and grow, and any other associated malformations may be addressed. Most patients are discharged once their ostomy has started to function and they tolerate a regular diet.

Following definitive repair, inpatient course is dictated by the presence or absence of a colostomy.

• If a child has been diverted with a colostomy prior to definitive repair and the repair is effectively completed using a posterior sagittal incision without laparotomy, the postoperative course is usually brief. The child may eat after the anesthesia wears off and requires a short hospitalization with perioperative antibiotic administration.

• Complicated repairs that require laparotomy also require more lengthy postoperative courses. These children usually require several days before intestinal function returns and a diet may be resumed.

• Repairs made without a colostomy may be treated with a "medical colostomy," meaning the child is not fed (ie, strict nothing-by-mouth [NPO] status) and a central line is placed for total parenteral nutrition. After an arbitrary period (commonly 5, 7, or 10 d, determined at the discretion of the surgeon in consideration of a host of factors), a diet is resumed and the total parenteral nutrition is stopped. The central line is removed, and the child may then be discharged.

Following ostomy closure, the child usually remains in the hospital for 2-3 days until intestinal function returns. Diet is then resumed, and the child may be discharged.

The decision-making process aims to determine which children should undergo primary repair in the neonatal period and which children require colostomy and definitive repair in a staged fashion. Children with anorectal malformations may undergo one or several of the following surgical procedures based on the child's presentation, physical examination findings, and imaging study findings.

Neonatal colostomy

A colostomy is performed in children who are not amenable to primary pull-through either because of malformation complexity (any urinary fistula in boys, vestibular fistula and cloaca in girls, no fistula in either sex >1 cm from perineal skin) or associated comorbidity.

The colostomy is usually fashioned through a left lower quadrant incision. The colon is divided at the point where the descending colon meets the sigmoid colon, and both ends are brought to the abdominal wall. By fashioning the colostomy at this location, the entire sigmoid colon is kept in place; thus, when the pull-through is eventually performed, a large portion of the colon is available for the surgeon to bring down to the perineal skin.

The mucous fistula (the downstream segment) should be very small, flush with the skin, and far enough from the proximal end to be outside the colostomy appliance (or under the flange) to avoid continued urinary soiling with feces.

During this operation, the distal segment of the colon must be exhaustively irrigated to clean out the impacted meconium, which is always significant. This prevents postdiversion urinary sepsis and allows for effective distal colostography.

Primary neonatal pull-through without colostomy

Many pediatric surgeons opt for primary pull-through in children with perineal fistulas (or no fistulas) and close (< 1 cm) rectal pouches on 24-hour lateral pelvic radiography. Some pediatric surgeons who specialize in colorectal problems often offer the same procedure for girls with vestibular fistulas.

Cystoscopy is usually performed to rule out associated malformation. This is performed immediately prior to the pull-through operation. A Foley catheter is inserted following the cystoscopy.

The preferred surgical approach is the posterior sagittal approach developed by Peña et al.

• The child is placed in the prone position with generous padding under the face and chest and a large bolster under the hips to elevate the area of interest.

• A muscle stimulator is used to show the precise position of the rectal muscle complex to enable exact division at the midline. The midline for this operation is defined by the line that precisely divides the muscle complex in half.

• Dissection proceeds until the rectal pouch is identified. The pouch is then mobilized until adequate length is obtained and the rectum is fully separated from its attachment to the genitourinary tract. Even if the structures do not communicate, they remain intimately associated until fully mobilized. This step ensures that the surgeon does not miss a fistula that was missed on urinalysis findings.

• Once the rectum has been mobilized, the muscle stimulator is used to mark the anterior and posterior limits of the muscle complex. The perineal body is then reconstructed, and the rectum is tacked down in the middle of the muscle complex. The posterior wound is closed and anoplasty is performed.

Posterior sagittal pull-through with colostomy

This approach is used in boys with rectourinary fistula (bulbar, prostatic, or bladder-neck fistula), in girls with cloaca or vestibular fistula, and in patients of either sex who do not have a fistula when the rectal pouch is further than 1 cm on 24-hour lateral prone abdominal radiography.

The approach is also used in children who may have malformations that were amenable to primary neonatal pull-through but were unable to undergo such a procedure because of extreme prematurity or other comorbidity.

Colostomy is performed after 24 hours (or immediately if one of the above diagnoses is made based on either physical examination findings or meconium in the urine). Several weeks following colostomy, distal colostography is performed, and the specifics of the malformation are clarified.

Cystoscopy is usually performed to clarify anatomy and to rule out associated malformation. This is performed immediately prior to the pull-through operation. A Foley catheter is inserted following the cystoscopy, except in girls with cloaca.

The reconstructive procedure varies based on the malformation, but the essential concepts include identifying and separating the rectum from other structures, dividing and ligating any fistulas, and fully reconstructing the pelvic anatomy with placement of the rectum within the confines of the muscle complex. Procedures for specific malformations are as follows:

• Vestibular fistulas are directly visible but have the longest common wall between the rectum and vagina and require significant delicate mobilization to avoid holes in either structure.

• The posterior sagittal approach is used in boys with bulbar or prostatic urethral fistulas. The rectum is isolated and opened, and the fistula is identified through progressive distal opening. Once the fistula is identified, the rectum proximal to it may be mobilized, and the fistula is then ligated. Reconstruction then proceeds with primary pull-through, as described above.

• Abdominal (open or laparoscopic) and posterior sagittal approaches are best in boys with bladder-neck fistulas because the fistula is best identified in the abdomen.

• Cloaca procedures are complex. A short – common-channel cloaca can be repaired using total urogenital mobilization. The posterior sagittal wound is opened into the cloaca, which is then further proximally opened until the urethral orifice is identified and catheterized. The rectum is then sought. In girls with 2 hemivaginas (50%), the rectum opens in the vaginal septum, although significant asymmetry may be present. After identification, the rectum is separated from the urogenital tract and completely mobilized. The urogenital tract is then mobilized as a solitary structure until the urethral orifice reaches the perineum. This is then reconstructed, and the muscle is marked to enable creation of an adequate vaginal opening and perineal body without impinging on rectal space.

• A long – common-channel cloaca repair often necessitates formal separation of the bladder and vagina, which requires laparotomy and ureteral catheterization. Vaginal replacement is sometimes necessary if the vaginal length is insufficient for reconstruction.

Colostomy closure

Once the wound has completely healed and postoperative dilations have achieved their goal (ie, the neoanus is at the desired size), the colostomy may be closed in traditional surgical fashion.

The following consultations may be indicated:

• Pediatric surgeon: Early consultation with a pediatric surgeon experienced with these anomalies is essential. Ill-conceived procedures during the newborn period may have lifelong consequences for the patient.

• Neurosurgeon: Consultation with a neurosurgeon is warranted if a tethered spinal cord is present (25% of all cases).

• Urologist: The need for consultation with a urologist depends on the malformation and the individual pediatric surgeon.

Diet

After the obstruction is relieved using colostomy, primary pull-through, or dilation, children do not require special diet. The most common complication of imperforate anus repair is constipation or anal incontinence; therefore, diet can be a crucial part of management. Many patients may require laxatives, enemas, or other medications or irrigations in addition to dietary manipulations. ^[14]  Children should avoid constipating foods, such as those included in the bananas, rice, applesauce, and toast (BRAT) diet. High-fiber and laxative foods (whole-grain foods and breads, dairy, fruits, vegetables, greasy foods, spicy foods) should be encouraged. Unfortunately, dietary manipulation is often of limited effectiveness because of the fussy nature of most children regarding diets. Fiber supplements and laxatives can be critically important in avoiding constipation, which can significantly affect prognosis.

Activity

Children with anorectal malformations are often otherwise healthy. Activity limitations are usually related only to the period around their surgical procedures.

Pitfalls abound in the diagnosis and treatment of children with anorectal malformations. A logical approach and an experienced eye are essential for starting the child down the right path from the outset. Complications, while sometimes unavoidable, can have devastating ramifications with respect to a child's chances for urinary and fecal continence.

The following are a few of the most common issues encountered at pediatric colorectal centers.

Primary repair without colostomy

Although certain malformations can be primarily repaired by an experienced pediatric surgeon in the neonatal period without the protection of colostomy, more complex malformations should be treated with colostomy at the initial operation. Primary neonatal operations do not afford the surgeon the benefit of distal colostography to help clarify anatomy. This has resulted in devastating injuries that could have been avoided with a staged approach (colostomy, followed by definitive operation, followed by colostomy closure) with appropriate diagnostic studies.

Colostomy type and position

The ideal colostomy position in children with an anorectal malformation is at the junction of the descending and sigmoid colon. The colostomy should be completely divided, with the ends spaced far enough apart to ensure that the mucous fistula is not located within the ostomy appliance. This prevents continued soiling of the urinary tract by feces, which can result in urinary infection. Loop colostomies are never completely diverting and put a child at risk for urinary sepsis. Transverse colostomies seem to be associated with a significant degree of mucous accumulation in the long defunctionalized segment, resulting in chronic distension and dysmotility similar to that seen in children with atresias. Desire to perform laparoscopic pull-through should not be a primary factor in the decision to perform colostomy. ^[15]

Intestinal perforation

This complication can arise during any phase of management.

In children diagnosed with imperforate anus at birth, 24 hours is allowed to pass prior to surgical treatment if perineal fistula (or other visible malformation, eg, vestibular fistula or cloaca) is not evident and urinalysis findings do not show meconium. This allows the distal colon to distend a bit, and meconium occasionally leaks out on the perineum from a tiny perineal fistula. This waiting period is advocated by the most experienced surgeons and should not increase the risk of perforation prior to repair or colostomy. Although exceedingly rare, some children have perforated during this period.

Perforation has also occurred during anal dilations. Dilations should always be performed first by the surgical staff. Dilation (performed instead of anoplasty) should be performed only by the surgical staff in extremely low birthweight premature babies. Parents may be taught how to dilate larger babies but must be closely supervised.

Perforation is minimized by appropriately positioning the colostomy while avoiding a transverse colostomy.

Operative complications

Correction of malformations, even those that some surgeons may describe as minor, requires significant experience, a keen eye, and a sensitive hand. Devastating complications (eg, complete dehiscence, postoperative fistula, missed fistula, urologic injury, ischemia) can render a child who may have been continent after a successful operation completely incontinent. Thus, these children should be directed to a subspecialist with a special interest in this area at the earliest possible opportunity.

Stenosis

This is a narrowing of the new anus. A tight ring of scar tissue forms instead of a soft and stretchable anus. This is a devastating complication and usually requires complete surgical repair. A regular schedule of slow progressive dilation of the neoanus prevents stenosis. Weekly dilations increase risk of stenosis. If the dilations are spaced too far apart, the anus can narrow between the dilations. Large dilations provoke tears. Tears heal with scar tissue, which causes stenosis.

Undrained hydrocolpos

Many baby girls born with cloaca have a very large mucous-filled vagina. This may appear as a giant cystic structure on prenatal ultrasonography. Ultrasonography should be performed at birth to look for such a cystic mass. If present, it must be drained either from below (through the cloaca) or at the time of colostomy using a vaginostomy tube. If it is left undrained, complications ensue.

Hydrocolpos can large enough to obstruct the ureters. Some children with undrained hydrocolpos have undergone vesicostomy and ureterostomy, when simple drainage of the hydrocolpos would have sufficed.

Hydrocolpos can also become infected. If the vagina perforates, it usually scars and becomes unusable, often necessitating vaginal replacement

Constipation

Many children who have undergone anorectal malformation repair develop constipation. This must be prevented by strong parental counseling and diligence to ensure the child clears the rectum daily. Constipation on its own is not a complication. The complication is not preventing the constipation through close follow-up and parental counseling.

Once constipation develops, the distal colon can become dilated, which exacerbates the constipation because the dilated bowel has poor motility. The end result is termed encopresis. Fecal impaction forms, and liquid stool leaks around it constantly, leaving the child incontinent. This can be treated but is best prevented.

Incontinence

Many children who have malformations associated with poor prognosis develop fecal or urinary incontinence, even after a flawless operation without complication. While "the plumbing" may seem to be a relatively simple matter of rearranging some tubes, continence is a complex state that requires a delicate balance of nerves, anorectal and colonic motility, and sphincter muscles. Parents should be given realistic expectations and should be made aware of all options, including bowel management or continent diversion and intermittent catheterization, should incontinence occur.

Children with an anorectal malformation require close follow-up for life. Continuity of care is essential in the growing years and into adulthood, as the children deal with issues relating to continence and constipation.

Following the initial colostomy, further investigations in preparation for definitive operation, such as distal colostography or repeat renal ultrasonography, are performed in an outpatient setting.

Following definitive operation in either the neonatal period or after colostomy, follow-up is necessary 2 weeks after surgery. Parents are often instructed as to how to obtain a set of Hegar dilators, which they are to bring to the first postoperative visit. At that visit, the surgeon measures the size of the anus and instructs the parents how to perform the daily dilations. These dilations continue until the anus has reached its goal size. At this time, the colostomy may be closed if one was performed.

Patients with cloacal anomalies need specialized follow-up care after puberty to assess sexual function and to correct genitourinary problems.

• Some girls who have undergone surgical correction for cloaca have incompletely canalized fallopian tubes and can develop painful cystic collections of menstrual blood following menarche. This condition sometimes requires surgical intervention. A pediatric gynecologist can be extremely helpful for these girls and can suppress menstrual blood production through exogenous hormone administration until a clear treatment strategy is established.

• Only within the past 20-30 years have significant numbers of girls with cloaca undergone definitive repair. A few have become pregnant. While this is miraculous, the delivery process should include close involvement of the pediatric surgeon who performed the original repair, if possible. If this is not possible, a surgeon experienced in cloaca repair should be consulted. Caesarean delivery is the only safe way to avoid damage to tissues that originally required complex reconstruction.

Some children present with prolapse during the toilet-training years. Eliminating constipation as a cause helps identify children who need surgical trimming of prolapsed mucosa.

Visits for constipation are frequent, and it is best treated with a regular preventative regimen that includes diet, fiber, and laxatives for as long as they are needed. Dietary water does not influence stool quality in a healthy child.