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Anorectal Congenital Disorders
Anorectal congenital malformations include a wide spectrum of defects, each of which requires a specific treatment and has a different functional prognosis. The main and most feared sequela is fecal incontinence, which is a devastating problem, although anal stenosis also may complicate some repairs.
Approximately 70% of all affected patients who are properly treated will have voluntary bowel movements by the age of 3 years, although some will still experience occasional soiling. About 40% of all patients will be totally continent, meaning that they will have voluntary bowel movements and will never soil their underwear. Our goal in treating patients born with the potential for bowel control is to repair their malformation by preserving the anatomic elements of fecal continence. For patients who are born without the potential for bowel control, our goal is the anatomic repair of the defect followed by the implementation of a bowel management program aimed at keeping the patients constantly clean, giving them the best possible socially acceptable quality of life. This chapter is designed to help clinicians and surgeons find quick answers to practical therapeutic questions.
Because of the existence of a spectrum of defects, any attempt to classify these malformations risks false generalizations. Table 17-1 lists the most conspicuous and common defects seen in everyday practice and correlates each with its prognosis for bowel control. This list may serve as a practical classification based on therapeutic and prognostic implications and includes benign defects (traditionally known as low defects), which are treated without a colostomy and with a small operation (anoplasty); 100% bowel control is achieved, and these defects are associated with a very low frequency of urinary malformations. On the other extreme of the spectrum are complex anorectal defects that are treated with a preliminary protective colostomy, followed by a major repair, with a high incidence of fecal incontinence. These patients also have a high incidence of associated urinary malformations. The term “high imperforate anus” is not used here because it includes malformations that require different treatments and have completely different prognoses (see Table 17-1 ).
TABLE 17-1
Common Congenital Anorectal Defects, Their Treatment, and Their Prognosis
| Type of Defect | Colostomy | Main Repair | Prognosis for Voluntary Bowel Movements (%) | Frequency of Urinary-Associated Defects (%) |
|---|---|---|---|---|
| Perineal fistula (male and female) | No | Anoplasty | 100 | <10 |
| Rectal atresia (male and female) | Yes | PSARP | 100 | 0 |
| Vestibular fistula (female) | Yes | Limited PSARP | 95 | 30 |
| Imperforate anus with no fistula (male and female) | Yes | PSARP | 75 | 26.4 |
| Rectourethral bulbar fistula (male) | Yes | PSARP | 85 | 25 |
| Rectourethral prostatic fistula (male) | Yes | PSARP | 60 | 66 |
| Cloaca (female, common channel <3 cm) | Yes | PSARVUP | 70 | 60 |
| Cloaca (female, common channel >3 cm) | Yes | PSARVUP plus laparotomy | 50 | 90 |
| Recto-bladder-neck fistula (male) | Yes | PSARP plus laparotomy | 15 | 92 |
PSARP, Posterior sagittal anorectoplasty; PSARVUP, posterior sagittal anorectovaginourethroplasty.
A significant portion of patients born with anorectal malformations also have other associated defects including genitourinary, sacrospinal, gastrointestinal, and cardiovascular defects. Early suspicion and expedited diagnosis and treatment of these defects will help avoid increased morbidity and mortality. Genitourinary defects represent the main source of death and morbidity, and therefore their presence should always be kept in mind. The frequency of associated defects varies depending on the specific type of anorectal defect (see Table 17-1 ).
Establishing the final functional prognosis in patients with anorectal malformations is an important step in their management; it avoids false expectations from the parents and allows the early implementation of a bowel management program in patients with a poor functional prognosis. This approach also avoids the traditional saga of fecally incontinent patients in search of a remedy that never comes, guided by a hope that has no factual basis. The prognosis can be established fairly accurately based on the type of defect. In addition, the accuracy of this prognosis can be enhanced by evaluating the integrity of the sacrum.
Fig. 17-1 shows how to calculate the sacral ratio. Values of 0.7 and higher correlate with good prognosis for bowel control, whereas sacral ratio values of 0.4 and lower predict fecal incontinence.
Sacral ratio. Normal values (≥0.7) correlate with good prognosis for bowel control. Values below 0.4 correlate with fecal incontinence.
Description of Defects
Perineal Fistula
A perineal fistula is the simplest of all defects and is seen with similar characteristics in male and female patients. The rectum opens into the perineum (always anterior to the location of the sphincter) and into an abnormal orifice, which is usually stenotic and therefore is called a fistula. Most of the rectum is surrounded by a good sphincter mechanism, except in its most distal part, where the rectum deviates anteriorly. The sacrum is almost always normal, the incidence of associated defects is low, and the functional prognosis is excellent (see Table 17-1 ).
Rectal Atresia
Rectal atresia occurs in only 1% of all male or female patients. Externally the anus looks normal, but an atresia or stenosis is located about 1 to 2 cm above the anal verge, at the junction of the anal canal with the rectum. The sphincter mechanism is normal, as is the sacrum. The incidence of associated defects is very low, and the prognosis is excellent (see Table 17-1 ). When a rectal stenosis is found, the surgeon should rule out the presence of a presacral mass. When a presacral mass is present, a sacral defect (hemisacrum or bifid sacrum) can be seen in the anteroposterior film of the sacrum, which changes the functional prognosis for bowel and urinary control.
Vestibular Fistula
A vestibular fistula is the most frequently seen defect in female patients. The rectum opens into the vestibule of the female genitalia immediately external to the hymen. Frequently, it is erroneously called a vaginal fistula. Most of the rectum is surrounded by a good sphincter mechanism, except for the lower part, which is frequently stenotic and is called a fistula. A common wall that exists between the rectum and the vagina must be separated during the surgical repair. Prior to the surgical repair it is important to confirm that the patient has a vagina and if there is a vaginal septum that correlates with the presence of two hemivaginas and hemi-uteri. The sacrum is usually normal, the frequency of association with urologic defects is low, and the prognosis is very good (see Table 17-1 ).
Imperforate Anus without Fistula
An imperforate anus without a fistula occurs in only 5% of all male and female patients. It is very frequently associated with Down syndrome. The rectum ends blindly about 1 to 2 cm above the perineal skin. The sphincter mechanism is fairly well developed, the sacrum is usually normal, and the prognosis is good (see Table 17-1 ).
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