ANORECTAL MALFORMATIONS – IMPERFORATE ANUS | Hellenic pediatric center for colorectal and urogenital diseases

ANORECTAL MALFORMATIONS - IMPERFORATE ANUS

Anorectal malformations (ARM) are also known as imperforate anus. This is a general term for a group of congenital anomalies affecting the anus and rectum.

In children with ARMs, there is abnormal development of the rectum and anus. The rectum develops in a different position from normal, often with a connection (fistula) depending on the type of ARM (perineum, bladder, urethra, vagina, etc.). In some cases, there is also abnormal development of the muscles and nerves in this area, which are responsible for continence.

ARMs may be accompanied by problems in other parts of the digestive tract or in other bodily systems (urogenital, cardiovascular, musculoskeletal, nervous).

The incidence of ARMs is one in 5,000 births and is slightly more common in boys. The exact etiology of ARMs is not known.

TYPES OF ANORECTAL MALFORMATIONS

Under normal circumstances, stool passes through the large intestine into the rectum (the last part of the large intestine) and is excreted through the anus.

In neonates with ARMs the stool is not excreted through the anus but to a different location, depending on endpoint of the rectum (fistula), which also determines the type of ARM.

Each type of ARM has specific characteristics and challenges that affect each child in a different way. The most common types of ARMs in children are:

MALES

Normal anatomy

ARM with a perineal fistula
In boys, the perineum is a small area between the scrotum and the anal sphincter. In this type of ARM the anus does not form normally and the rectum ends with an opening (fistula) in the perineum in front of the anal sphincter.

ARM with bulbar urethral fistula

In this type of ARM, the rectum joins (via a fistula) to the lower urethra. The stool passes into the urethra, are mixed with the urine and then excreted via the urethra.

ARM with prostatic urethral fistula

In this type of ARM, the rectum joins the urethra at the level of the prostate (proximal urethra). Stools are mixed with urine and excreted via the urethra.

ARM with bladder neck fistula

In this type of ARM, the rectum joins the bladder and feces enter into it. This causes a mixture of urine and feces, which are excreted from the urethra.

ARM without fistula

In this type of ARM, the rectum is a blind ending pouch and does not have a connection with another other anatomical structures.

Membranous anal atresia

In this malformation the rectum has formed normally but the anus is covered by a thin membrane not allowing the stool to be excreted.

Anal Stenosis
In these cases the rectum passes through the sphincter to reach the anus but is narrower than usual. Thus results in difficulty in the passage of stool and requiring higher pressure in the rectum which may be associated with a dilated rectum and significant constipation.

FEMALES

Normal anatomy

ARM with perineal fistula

In girls, the perineum is a small area between the anal sphincter and the lower pole of the vulva (external genitalia). In this type of ARM the anus does not form normally and the rectum ends with an opening (fistula) in the perineum in front of the anal sphincter.

ARM with rectovestibular fistula

In girls, there is a small area between the labia and the opening of the vagina called the vestibule. In this case, the anus does not form normally and the rectum ends in a small opening in the vestibule.

ARM with recto-vaginal fistula

In this type of ARM, there is an abnormal connection between the rectum and the vagina. This results in the passage of stool via the vagina.

ARM without fistula
In this type of ARM, the rectum is a blind ending poutch and does not have a connection with another anatomical structure.

Cloaca

In this complex type of ARM, the rectum, vagina, and urethra have not formed into separate structures and are combined as a common channel resulting in a single external orifice. Instead of having 3 normal orifices (anus, vagina, urethra) in the rectal area, the child has only one.

Membranous anal atresia

In this malformation the rectum has formed normally but the anus is covered by a thin membrane not allowing the stool to be excreted.

Anal Stenosis
In these cases the rectum passes through the sphincter to the anus but is narrower than usual. Thus results in difficulty in the passage of stool and requiring higher pressure in the rectum which may be associated with a dilated rectum and significant constipation.

DISORDERS ASSOCIATED WITH ANORECTAL MALFORMATIONS

Other malformations that may co-exist with ARMs affect the:

Associated anomalies affect the urogenital system at a rate of 30% -50% depending on the severity of ARM.

The most common disorders affecting the urinary tract are vesicoureteral reflux (45%) and unilateral renal agenesis (18%). Less frequently observed are duplication of intra-pelvic organs, neurogenic cysts, posterior urethral valves, and hydronephrosis.

Anomalies may also affect the reproductive organs. In males undescended testis (10%) and hypospadias (5%) are most commonly seen. In females, anomalies are especially common in cloaca malformations, these may be anomalies of the vagina (hydrocolpos, atresia, vaginal septum or duplication) or of the uterus (didelphys or bicornuate uterus).

the spinal column and spinal cord at a rate of 30% -40%. The most common of these are lumbar hemivertebrae, sacral agenesis, bifurcated spine, syringomyelia, meningocele and myelomeningocele.

the cardiovascular system at a rate of 15% -30%. The most common are atrial septal defects, patent ductus arteriosus, ventral septal defects, Tetralogy of Fallot, transposition of the great arteries, and hypoplastic left heart syndrome.

the digestive system at a rate of 12%. Esophageal atresia is the most common (10%), followed by duodenal atresia, annular pancreas (1% -2%), and malrotation (1%).

About 50% of children with ARM have other associated anomalies that may be classified as VACTERL syndrome.

The acronym VACTERL stands for:

anomalies of the spinal column (Vertebral defects)
Anorectal malformations
Cardiac Defects
Esophageal Atresia and Tracho-Esophageal fistula
Renal anomalies
Limb anomalies

Children affected by 3 of the above anomalies are diagnosed with VACTERL syndrome.

Children who are affected by associated anomalies are best managed by a multidisciplinary team of specialists, who can work together to best evaluate and treat their problems.

DIAGNOSIS

In some cases (16%), a diagnosis of an ARM may be made on prenatal ultrasound. When this is suspected, the obstetrician/gynecologist can refer the family to the Pediatric Center for Colorectal and associated Urogenital Disorders (PCCUD).

However, ARMs are usually diagnosed immediately after birth, during the newborn’s first clinical examination. The neonatologist detects the absence of an anal opening or finds it in an abnormal position.

Following the clinical diagnosis, further evaluations are is required, especially in cases that are not clinically evident regarding exact type of ARM. Furthermore, clinical laboratory and imaging test are necessary to determine possible associated anomalies affecting other systems.

Urine analysis and culture: detection of meconium in the urine of males is evidence of a fistula between the rectum and either: the bladder, the prostatic urethra, or the bulbar urethra
Lateral cross table X-ray (Invertogram): May help to determine the type of ARM by investigating the distance of the rectum from the perineal skin (low or high malformation).
Ultrasound of the kidneys, ureter, and bladder: is performed to detect any anomalies of the urinary tract.
Ultrasound of the internal reproductive organs: is performed to investigate for any anomalies of the internal reproductive organs in females.
Ultrasound of the spine: to investigate for spina bifida or a tethered cord. Tethered cord is a disorder in which the spinal cord is fixed to a structure of the spine (e.g. dura, bone). This may lead to neurological problems such as urinary or fecal incontinence, and lower limb weakness as the child grows older.
MRI of the lower abdomen – lumbar region – pelvis: may help to more accurately diagnose the type of abnormality (measurement of rectal-anal distance / low or high atresia) and is sometimes required for the definitive diagnosis of tethered cord, or other abnormalities of the spine. In addition, it is used to characterise the anatomy pelvic floor muscles and internal reproductive organs.
Cardiac echo: to detect any structural anomalies of the heart.
Orthopedic evaluation: to detect any anomalies affecting the musculoskeletal system.

TREATMENT

Every child with ARM has individualized needs. The team that will take on their care will create a specific treatment plan based on the type of ARM that your child has, the presence of other associated anomalies, and the overall state of their health. The cooperation of the specialized team ensures the best possible outcome for your child.

All babies with ARM will need surgery to correct their anomaly except in the case of anal stenosis. The type and number of operations your child needs depends on the type of ARM he or she has.

THE AIM OF SURGICAL MANAGEMENT

The aim of surgical management of a child with an anorectal malformation is:

the anatomical correction of the malformations
fecal continence
urinary continence
function of external genitalia for future sexual and reproductive functions

After its introduction, the Posterior Sagital Anorectoplasty (PSARP) became the treatment of choice for the treatment of patients with ARM. The functional outcomes (fecal incontinence, defecation control, rectal sensation, pre-emptying warning, urination control and sexual function) of patients has improved dramatically following its widespread adoption.

However, it is important to know that even a technically excellent operation does not ensure a good functional outcome. This is determined by the severity of ARM and its associated malformations.

SURGICAL PROCEDURES

In some instances (anal atresia with perineal fistula) a PSARP operation may occur in the first days of life without the needs for a colostomy.

In other cases, however, the correction of an ARM requires more than one surgical procedure. These operations include:

POSTOPERATIVE CARE

The immediate postoperative period after a PSARP operation is usually without significant problems. Postoperative pain is controlled, feeding is started immediately after bowel are active and parents can be by their children’s side throughout their post operative period. The length of stay in the hospital varies from case to case. During the operation, self-absorbable sutures are used and no further procedure is required to remove them.

After a colostomy formation the stoma is observed for passage of stool, and also for signs of bacteria and infection that this stool may bring with it.

A few weeks after the operation, the dilatation of the anus are started, and a few months after the PSARP the colostomy will be closed. This restores the continuity of the intestine and the feces will be expelled from the anus.

After the closure of the colostomy, the patient oftan has many soft or watery stools for a short period of time. This can irritate the skin around the anus (diaper rash). Within a few weeks of surgery, bowel movements become less frequent and more formed in texture.

Then the number of bowel movements normally decreases and most patients will experience some degree of constipation. After about 6-12 months, the patient is expected, depending on the case, to have normal bowel movements. However, some children may have problems even after corrective surgery

For this reason, all patients who have had surgery for an ARM need postoperative follow-up for bowel movements and urinary function for a significant period of time. The length of time depends on the severity and type of ARM.

The multidisciplinary team will work closely with you for the improvement any problems that may arise.

PROBLEMS (FUNCTIONAL DISORDERS) THAT MAY EXIST FOLLOWING THE CORRECTION OF ANORECTAL MALFORMATION AND THEIR MANAGEMENT

A significant proportion of patients with ARMs following their surgical correction may experience bowel disorders (constipation, fecal incontinence), urinary disorders, infections and other problems.

Even a technically excellent operation does not ensure a similar functional result. This is highly dependent on the type of ARM and the associated abnormality of the pelvic floor and sphincter muscles, and the nerves to those muscles and the rectum. This of course depends on the severity of ARM. The greater the severity of ARM, the more likely that a patient will face further problems during the course of thier life.

In some cases these problems may be minor and easy to treat. When they are significant they may affect multiple facets of life, such as control of urine and feces, and sexual function. This may lead to psychological problems and difficulties in social adjustment, they may need the support of a specialized medical and surgical team, psychologists, and nursing staff for long periods of time.

FUNCTIONAL DISORDERS OF DEFECATION

Functional bowel disorders can be mild or severe, and can accompany a number of patients for short or long periods of time. In a small number of patients these problems exist throughout their childhood, adolescence and adulthood.

Patients with functional disorders of the bowel are divided in three main categories

1.The first category are patients with functional disorders due to postoperative or intraoperative complications and must undergo a second operation to restore the anatomy of the area. Approximately 13% -43% of these patients will show complete continence after reoperation while 64% -83% will have relative control of the defecation mechanism.

2.The second category are patients who experience pseudo-diarrhea due to overfilling. These patients have a large rectum which is the cause of the functional disorder.

Approximately 90% of these patients, can have satisfactory control of defication with the BOWEL MANAGEMENT PROGRAM. Of these, approximately 30% may at some point undergo surgical removal of the dilated rectosigmoid colon with encouraging functional results.

3.The third category are patients with a previous severe form of ARM that suffer with fecal incontinence.

Children who have been operated on for ARMS may gain fecal continence and outgrow urgency for stooling at an older age then children without ARMs.

A small number of children have behavioral problems relating to the defecation process. This is due either due to insufficient training or the psychosomatic impact of experiences of pain, poor conduct of enemas, etc. Education for continence and urgency for defecation should begin at a normal age for children with ARM. This usually happens at the age of three or four. If the child is still using a diaper, unlike children their age, the care team will help to address the problem.

In some children, the type of ARM they were born with may not give them the potential for full control of their bowels and/or may have severe constipation.

The BOWEL MANAGEMENT PROGRAM is specially designed for the management of these problems. The approach combines management of diet, medication, enemas, physiotherapy, psychological support all aimed at instructing and improving bowel continence.

Results are encouraging as the majority of children have a detectible improvement in the quantity and form of their stool, their urinary continence, and thus improving to their quality of life

A significant number of patients with ARMs are able to empty their bowels on a daily basis. This is also dependent on the severity of ARM.

When children are able to stay clean during the day for three consecutive days, the treatment is considered successful and the program is adopted by the patient and his family.

In case the patient continues to have problems despite the efforts through the BOWEL MANAGEMENT PROGRAM then consideration is given to perform either a permanent colostomy or a permanent formation of route for Antegrade Continence Enemas (ACE/MALONE OPERATION).

URINARY AND GENETIC SYSTEM DISORDERS

Due to the anatomical and functional abnormality of the pelvic muscles and nerves, disorders of the urinary system may occur and lead to a range of simple to serious problems (urinary incontinence, lack of bladder filling and urgency to urination, etc.). The number of patients in whom there is a concomitant congenital abnormality of the urinary tract (vesicoureteral reflux, etc.) is not insignificant.

In a small proportion of patients there may also be sexual dysfunction in adolescent or adult life.

PSYCHOSOCIAL PROBLEMS

Due to functional problems of the bowel, a significant number of patients with ARMS experience psychosocial problems such as shame, introversion, depression, limited self-esteem, avoidance of coexistence with others, avoidance or dropping out of school, social isolation and general problems affecting social integration. Their quality of life may be gravely affected.

TREATMENT OF POSTOPERATIVE SOCIAL AND FUNCTIONAL CHALLENGES

Treating social functional disorders in patients with ARM is a particularly complex, challenging, and important part of their overall treatment.

In order to improve their quality of life, the cooperation of the patient and the parents with the treating physician and the members of the PCCUD multidisciplinary team (pediatric surgeons – pediatric urologists, pediatric gastroenterologists, neurosurgeons, gynecologists, neurologists, psychiatrists, psychiatrists, physiotherapists). In doing so an individualized management plan is formulated for each patient, results in optimization and greatest improvement in the social and functional problems they face.

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