Congenital Anorectal Malformations: Anything New?

Journal of Pediatric Gastroenterology and Nutrition 48:S79–S82 # 2009 by European Society for Pediatric Gastroenterology, Hepatology, and Nutrition and North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition

Risto J. Rintala

Hospital for Children and Adolescents, Helsinki, Finland

ABSTRACT Management of anorectal malformations, especially that of niques are increasingly applied to the management of these proximal and more severe forms have developed signiﬁcantly anomalies, although their role is as yet not clearly established. in the last 25 years. Echography and magnetic resonance Long-term functional follow data are also available today imaging have improved the diagnostic accuracy, especially in indicating a reasonable favourable faecal and urinary control terms of associated anomalies that are the main cause of in the majority of patients with anorectal malformations. For the fatalities among patients with anorectal malformations. Animal patients with less favourable functional outcome there are models, novel molecular biological techniques and knock-out bowel and bladder management options that provide sufﬁcient gene models have widened our knowledge on aetiology and social continence. JPGN 48:S79–S82, 2009. Key Words: pathogenesis of these anomalies. Anorectal malformations—Imperforate anus—Outcome— From early 1980s, the posterior sagittal anorectoplasty PSARP. # 2009 by European Society for Pediatric Gastro- originally designed by deVries and Pena has systematized enterology, Hepatology, and Nutrition and North American the surgical management of anorectal anomalies leading to Society for Pediatric Gastroenterology, Hepatology, and improved functional outcomes. Surgical mini-invasive tech- Nutrition

Malformations of the anorectum include a series of (Table 1), which is based on consensus recommendations congenital lesions ranging from a slight malposition of world authorities (1). of the anus to complex anomalies of the hindgut and The outcomes of patients with anorectal malformations urogenital organs. The reported incidence of anorectal have greatly improved by modern surgical techniques and anomalies range between 1:3300 and 1:5000 live births. neonatal care facilities during the last decades. Early In Western communities there is a male preponderance, survival is today a rule except in some rare cases with 55% to 70% of the patients in larger series have been cardiac, urogenital, or chromosomal anomalies that are not males. The more severe malformations tend to be more compatible with life. The overall long-term functional common in male patients. outcome expectancy in terms of faecal and urinary con- In most cases, anorectal malformations present as an tinence is today relatively optimistic. The majority of absence of an anus in its normal position. In mild forms of patients reaching adolescence and adulthood are able to anal anomalies the bowel outlet opens in the perineal maintain themselves socially continent. region outside the usually well-developed voluntary sphincter complex. In more severe anomalies bowel outlet RECENT BASIC SCIENCE opens in an ectopic position in the urogenital tract in males or genital tract in females. Neonatal recognition of the type The aetiology of anorectal anomalies is not known. of the malformation is essential for the planning of the Genetically determined syndromes with anorectal mal- surgical management of anorectal anomalies. formations are relatively uncommon. On the contrary, There is no generally accepted method to classify anorectal anomalies occur commonly in multianomaly anorectal malformations. The most commonly used sequences such as VACTERL or CHARGE associations. has been the Wingspread International Classification The overall incidence of associated anomalies in patients for Anorectal Malformations. Recently, a new simplified with anorectal malformations is more than 60%. This classification has emerged, Krickenbeck classification suggests that the stimuli that induce abnormal development of anorectum operate universally in the developing foetus and may cause maldevelopment of several organ Address correspondence and reprint requests to Risto J. Rintala, systems. Anorectal malformations may develop in some Professor of Paediatric Surgery, Hospital for Children and Adolescents, PO Box 281, FIN-00029 HUS, Finland (e-mail: risto.rintala@hus.fi; syndromes that are caused by a mutation of a single gene. risto.rintala@saunalahti.fi). These include Currarrino syndrome, which is caused by The author reports no conflicts of interest. a mutation in HLXB9 gene in chromosome locus 7q39 S79

TABLE 1. Standards for diagnosis—international Despite abundance of sophisticated diagnostic imag- classification (Krickenbeck) ing modalities, the diagnosis and classification of anorectal malformations remain on the basis of clinical picture Major clinical groups Rare/regional variants and examination. The clinical examination performed by Perineal (cutaneous) fistula Pouch colon an experienced examiner reveals the type of the anorectal Rectourethral fistula Rectal atresia/stenosis malformation in >90% of the cases. Prostatic Rectovaginal fistula Classical imaging with inversion or cross-table radio- Bulbar H fistula Rectovesical fistula Others graphy is useful in selected cases where clinical exami- Vestibular fistula nation is equivocal; however, there are many possibilities Cloaca for erroneous interpretation. Ultrasound has not esta- No fistula blished itself as a reliable method to determine the position Anal stenosis of the terminal colon. It provides similar information as the prone, cross-table radiography and has similar limitations. and Townes-Brock syndrome, which has a mutated However, ultrasound is extremely useful in detecting SALL1 gene in chromosome locus 16q12.1 abnormalities in the urinary and genital tracts, especially The pathogenesis of anorectal malformations has obstructive uropathy and hydrometrocolpos. recently been much clarified by modern embryological Modern computed tomography technology allows studies concerning experimental models of anorectal multiplanar imaging, however, this comes at a cost of anomalies. Anorectal anomalies occur spontaneously radiation to a newborn child. Although it provides in some animal models (Danforth’s short tail mouse) increased detail, especially of the bony structures as well and can be induced by several substances, such as as pelvic musculature, it is not reliable in revealing the ethinylthiourea, retinoic acid derivatives, and adriamy- anatomy of bowel termination and the rectourogenital cin. The spectrum of malformations following admi- communication. nistration of these substances is variable, but they are Magnetic resonance imaging provides the same multi- valuable tools for embryological studies. The most sig- planar capability as computed tomography scan but with- nificant findings in these embryological models are out the radiation burden. Although magnetic resonance abnormalities or absence of the cloacal membrane. imaging can accurately delineate the level of the bowel The abnormal cloacal membrane does not allow normal termination, it will detect only a small proportion of the breakdown of the bowel to the perineum. In the animal rectourogenital fistulas. In newborn, small body size also models a clinically important discovery has been the impedes spatial resolution. character of the rectourogenital or perineal communi- The most reliable and useful imaging modality is still cation; the fistulous communication is actually an ectopic the colostogram, especially if it is augmented by pressure. anus. This ectopic anus has the characteristics of a normal All patients who have undergone a primary diverting anal canal including a distal zone of transitional epi- colostomy for a severe anorectal anomaly should have thelium, anal glands, and the internal anal sphincter, this imaging study to accurately delineate the anatomy of which is a thickening of the circular muscle layer around the bowel termination and the fistula. Micturating cysto- the bowel outlet. The voluntary external sphincter com- urethrography has still its place in the imaging of a neonate plex including the levator ani muscle develops separately with an anorectal malformation because of high incidence in a normal position. The voluntary sphincters are always of renal tract anomalies. hypoplastic; the degree of the hypoplasia is dependent on Of absolute importance is imaging to detect associated the distance of the rectal pouch from the perineum and on malformations as some of these defects may be life threat- the severity of commonly associated sacral deformity. ening or have a greater impact on survival of the patients than the anorectal malformation. Typical anomalies of DIAGNOSTIC MODALITIES this kind are cardiac defects and tracheo-oesophageal anomalies. Chest radiography with a nasogastric tube in With the exception of those anorectal malforma- place excludes the presence of an oesophageal atresia. tions that are associated with other major structural Cardiac echogram is used to screen cardiac anomalies. anomalies (eg, VACTERL syndrome or caudal regression Ultrasound of urinary tract is performed in each patient syndromes), prenatal ultrasound diagnosis of it is uncom- with an anorectal malformation to rule out obstructive mon. The sonographic features in the foetus are non- uropathies and other urinary tract anomalies. specific and include dilated or echogenic fetal bowel and Vertebral and sacral anomalies are common in patients hydrometrocolpos. Associated cardiac, renal or vertebral with anorectal malformations. These are commonly anomalies may be detected. Cloacal malformations can accompanied by spinal cord abnormalities. The spinal rarely be diagnosed by the presence of a septated cystic cord can also be visualized by ultrasound in a neonate. mass in the pelvis with hydronephrosis and oligo- This is usually performed in combination with radio- hydramnios. graphs that provide information on the bony structures.

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MANAGEMENT remain unclear. Theoretically, repair as early as possible could augment development of neurocircuitry between A provisional diagnosis of the severity of an anorectal anal canal and brain, resulting in better functional out- malformation is usually easily made in a newborn. The come. most important issue is to ascertain the level of the Recently, some surgeons have advocated laparoscopy- anomaly, because it determines the operative treatment assisted repair for high anorectal anomalies. The pro- in the neonatal period. There is rarely any urgency, and cedure entails laparoscopic mobilisation of the rectal most patients tolerate the low bowel obstruction without blind pouch, closure of the rectourethral fistula, and symptoms for longer than 24 hours if the upper gastro- pull-through of the bowel termination through the centre intestinal tract is decompressed by a nasogastric tube. of sphincter funnel that has been identified by muscle Before any treatment of the anorectal malformation is stimulation. At the moment laparoscopic surgery for carried out, life-threatening associated malformations anorectal anomalies is at an experimental stage, but the should be ruled out. approach is promising, especially because of its mini- The aims of surgical treatment are to provide a nor- invasiveness. Long-term follow-up results are lacking mally sited anus of adequate calibre and appearance but warranted. while preserving as much of the normal intrinsic anorectal anatomy and function as possible. In recent years, OUTCOMES the posterior sagittal anorectoplasty (PSARP), developed and popularized by Alberto Pen˜a, has become the most Long-term functional outcome following repair of frequently performed surgical procedure in the recon- anorectal malformations with a perineal opening (low struction of anorectal malformations (2). The PSARP malformations) is good in the majority of patients. The affords a relatively standardized approach to all common bowel function does not equal that of healthy people, but varieties of anorectal anomalies, enables direct visual- most patients have a good quality of life without social ization of the structures without the necessity for blind, restrictions. The most common complaint especially potentially hazardous, surgical manoeuvres, and offers during childhood is constipation, which is usually the opportunity for anatomically precise reconstruction. manageable with oral laxatives. Functional results are definitely no worse than with Patients with more severe anomalies have somewhat traditional surgical techniques, and there is growing more guarded functional prognosis (4). Although it is evidence that long-term bowel function is superior. evident that modern methods of repair yield superior The timing of surgery is variable; today many surgeons functional results compared with older techniques such try to undertake repair as soon as the patient has stabilised as abdominoperineal or sacroperineal pull-through, a from neonatal procedures. There is some evidence that significant percentage of patients still experience abnor- the functional results are better if the repair is performed mal bowel control. These patients can be helped signifi- as early as possible. cantly by bowel management programmes that often In patients with a perineal bowel outlet or fistula include formation of a continent catheterisable conduit (traditional low anomaly) the anorectal repair can be from the appendix that is used to empty the bowel performed safely in a newborn. In males the options are a regularly. With the help of bowel management regimens simple cutback anoplasty or a limited PSARP procedure a majority of patients with severe malformations gain a that requires significantly more extensive dissection than good quality of life. Novel technical innovations such as the cutback procedure. Functional outcomes are similar, artificial anal sphincters, electrically stimulated sphinc- but there appears to be fewer complications after the ters, or sacral nerve stimulation have been used in some cutback operation (3). In females cutback procedure selected patients with promising outcomes. However, yields unsightly cosmetic result and probably worse similar cleanliness as with antegrade bowel washouts outcome than after a limited PSARP procedure. is rarely achieved. Patients with more severe anomalies usually receive a The patients with anorectal malformations need care- diverting colostomy as a newborn. These anomalies are ful follow-up throughout their childhood. Functional usually repaired with the PSARP procedure followed by complications such as constipation should be detected closure of the colostomy. A typical male anomaly is an and treated early to achieve optimal outcome. The treat- imperforate anus with a rectourethral fistula and a typical ment of defective continence should be started well female anomaly an imperforate anus with a rectovesti- before the child reaches school age to overcome the bular fistula. The latter may be repaired in a newborn devastating social consequences of faecal soiling and without previous colostomy, but a safer approach would to integrate the child to the social context of his peers. be a staged operation. Recently, some surgeons have Because the management of anorectal malformations advocated neonatal repair without preceding colostomy requires years of commitment and special knowledge for severe anomalies as well. This approach has not concerning the anatomical and physiological character- gained general acceptance and the functional outcomes istics of this complex group of congenital malformations,

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these children should be treated by specialised medical 2. Pena A. Anorectal malformations. Semin Pediatr Surg 1995;4:35– personnel in specialised referral centres. 47. 3. Pakarinen MP, Goyal A, Koivusalo A, et al. Functional outcome REFERENCES in correction of perineal ﬁstula in boys with anoplasty versus posterior sagittal anorectoplasty. Pediatr Surg Int 2006;22: 1. Holschneider A, Hutson J, Pen˜a A, et al. Preliminary report on 961–5. the International Conference for the Development of Standards for 4. Rintala R, Lindahl H. Is normal bowel function possible after repair the Treatment of Anorectal Malformations. J Pediatr Surg 2005; of intermediate and high anorectal malformations. J Pediatr Surg 40:1521–6. 1995;30:491–4.

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