Youngjae Im, MD
Sang Won Han, MD
BASICS
DESCRIPTION
• Anorectal malformations (ARMs) are a spectrum of congenital anomalies involving the anorectal and urogenital systems, such that the anus and distal rectum are often absent
– Imperforate anus: Absence of an anus, typically with a fistula between rectum and lower urinary tract
– Persistent urogenital sinus (UGS) is seen in 4 entities (1):
Genital ambiguity state: Most common being congenital adrenal hyperplasia (CAH)
Pure UGS: With normal external genitalia
Cloaca: In females, a common channel between lower urinary tract, vagina, and rectum
Female exstrophy
EPIDEMIOLOGY
Incidence
• ARM: 1 in 4,000–5,000 live births:
• Cloaca: 1 in 40,000–50,000 live births
• UGS: 1 in 500 live births
• Incidence of ARM in the setting of genetic disease is about 5–10%
Prevalence
N/A
RISK FACTORS
• Proposed association with in utero vascular accidents, maternal diabetes and obesity, maternal ingestion of thalidomide, phenytoin, and trimethadione and maternal exposure to smoking and caffeine
• Some degree of heritability, as incidence of subsequent children having ARM is 1%
Genetics
• ARM found in certain congenital syndromes with associated genetic abnormalities (2)
– Trisomy 21: Imperforate anus without fistula
– Microdeletion of chromosome 22q11.2
– Familial inheritance pattern: ARM with a rectovestibular or rectoperineal fistula, almost 15% had a positive family history for an ARM
– Currarino triad: ARM, sacral agenesis, presacral mass (or meningocele); autosomal dominant
– Townes–Brocks syndrome: ARM, external ear abnormalities, hearing loss, polydactyly, renal anomalies; autosomal dominant
– Cat eye syndrome: ARM, coloboma, preauricular tag, heart defect, urinary tract abnormalities, mental retardation
PATHOPHYSIOLOGY
• Classic theory: The urorectal septum (mesoderm), fails to grow caudally to meet the lateral Rathke folds to divide the cloacal membrane (endoderm and ectoderm) into the anterior urogenital membrane and the posterior anal membrane.
• Alternative theory: A mesenchymal mass displaces the dorsal cloacal membrane anteriorly, preventing its joining with the hind gut.
ASSOCIATED CONDITIONS
• About 50–67% of all ARM are associated with other anomalies
– In general, the higher the ARM, the more likely there are associated abnormalities
• Can occur as an isolated abnormality or as part of a syndrome:
– VACTERL: Vertebral, anorectal, cardiac, tracheoesophageal fistula, renal, limb abnormalities
• Spinal and bony abnormalities are present in 33–50% of ARM:
– Tethered cord in 20–30%
– Sacral agenesis, the most common vertebral anomaly
• Genitourinary abnormalities ranges from 33% to almost 50% of ARM:
– VUR present in 14–56% of ARM
– Renal agenesis: 12–30%
– Neurogenic bladder: 4–25%
– Renal anomalies: Horseshoe kidney, ectopic kidney, multicystic dysplastic kidney 4–12%
– Cryptorchidism/hypospadias: 4–6%
• Gynecologic problems are common in ARM, but most may not be diagnosed until puberty or adulthood
– Duplicated vaginas with septum
– Absent vagina; vaginal atresia
– Bicornuate uterus
– Clitoromegaly in UGS associated with CAH
• Cardiovascular abnormalities are present in 10–30% of ARM:
– Atrial septal defects and ventricular septal defects are most common
• Tracheoesophageal fistula (TEF) and esophageal atresia (EA) occur in 5–10% with ARM
GENERAL PREVENTION
International Consortium on Anorectal Malformations aims to identify genetic and environmental risk factors in ARM. No prevention reduction strategies are currently available.
DIAGNOSIS
HISTORY
• Prenatal diagnosis: Low sensitivity/specificity
– Dilated colon, oligohydramnios, and distended vagina on prenatal US may be signs of ARM
– Antenatal findings suggestive of cloacal anomaly:
Transient fet al ascites with bilobed or trilobed pelvic cystic structures
Bilateral hydronephrosis or oligohydramnios
• Lower-level ARM and UGS may go undiagnosed in newborn until later symptoms develop:
– Constipation, abdominal distension in rectal atresia, anorectal stenosis
– Urinary incontinence and/or retention in UGS
– Amenorrhea and abdominal distension due to hydrometrocolpos or hematocolpos at puberty in UGS
PHYSICAL EXAM
• Thoroughly examine the perineum to determine number and position of orifices:
– Perineum flattened in higher-level ARM
• Inspect the genitalia: Rule out hypospadias, cryptorchidism, clitoromegaly
• Assess vertebrae: Look for sacral abnormalities
• Palpate for an abdominal mass that may represent a distended bladder or hydrometrocolpos
• Rule out associated pathologies:
– Cardiac auscultation for murmur
– Insert nasogastric tube for tracheoesophageal fistula
– Skelet al/limb assessment
• Once the diagnosis of an imperforate anus is made, assess for the presence of a fistula
– It may take up to 24 hr for signs of fistula to be evident
DIAGNOSTIC TESTS & INTERPRETATION
Lab
• Renal profile
• Urinalysis: Abnormal if fistula to urinary tract
• 17-hydroxy-progesterone in UGS with virilization to rule out CAH
• Karyotype if ambiguous genitalia
Imaging
• Studies to determine level of ARM:
– Prone, cross-table lateral plain film
Should be performed at 24 hr after birth to allow enteric gas to reach the most distal area of the colon
Distance between rectal gas shadow and perineal opening measured
• Abdominal US: Evaluate bilateral kidneys, bladder, ± müllerian structures
• Voiding cystourethrogram (VCUG)/cloaca gram/genitogram: Evaluate presence of VUR as well as relation of urinary tract to rectum (and to müllerian structures)
• Colostogram: Distal to mucous fistula and proximal to colostomy to evaluate colon and its relation to other pelvic structures prior to definitive surgery
• Spinal imaging:
– Spinal US prior to 6 mo of age
– Spinal MRI after 6 mo of age
Diagnostic Procedures/Surgery
• Echocardiogram and ECG: Rule out cardiac anomalies
• Urodynamic study : Especially in cases of UTI, VUR, urinary incontinence, spinal anomalies
– The most common finding on UDS is an upper motor neuron lesion with an overactive detrusor and/or detrusor sphincter dyssynergia (DSD)
• Exam under anesthesia/endoscopy: Helps delineate relationships between structures and measure length of common channel and proximity of fistula/confluence to bladder neck
Pathologic Findings
N/A
DIFFERENTIAL DIAGNOSIS
• Classification systems for ARM (3)
– Wingspread classification: Traditional “low,” “intermediate,” or “high” ARM
– Pena classification: Based on the presence and position of the fistula
– Krickenbeck anatomic classification: An anatomic description of ARM, type of surgical procedure performed, and postop assessment of bowel movements, constipation, and soiling
• Lesions in the male: Classifying patients (ie, into low-lying or higher lesions) have important clinical implications with regard to their treatment and prognosis
– Imperforate anus without fistula, rectal atresia, rectoperineal fistula
– Recto bulbar urethral fistula
– Recto posterior urethral fistula
– Rectovesical fistula
• Lesions in the female:
– Imperforate anus without fistula, rectal atresia, rectoperineal fistua
– Rectovestibular fistula: Most common defect
– Cloaca: Further subdivided into length of common channels:
Short (<3 cm): Good prognosis
Long (>3 cm): More complicated and worse prognosis
– UGS:
Some associated with virilization, as in CAH
Some not associated with virilization
Can be result of congenital cloaca following isolated repair of the rectum
TREATMENT
GENERAL MEASURES
• Newborn should not be given any enteric intake and should have nasogastric suction
• Hydrometrocolpos (present in 50% of cloaca) and urinary retention in newborn period managed with catheter drainage until operative intervention
MEDICATION
First Line
• IV antibiotics neonatally and perioperatively
• Prophylactic antibiotics continued at least until VUR is ruled out
• Eventual fecal incontinence may be treated with combination of enemas and antimotility agents
• Eventual constipation may be treated with combination of enemas and laxatives
• Anticholinergics may be necessary for neurogenic bladder
Second Line
N/A
SURGERY/OTHER PROCEDURES
• Newborn:
– Diverting colostomy with mucous fistula needed in all but the lowest of ARM:
Level of colostomy should be distal on descending colon; distance between stomas should be wide to minimize the length of bowel that could potentially be in contact with urine in cases of fistula
– Neonatal posterior sagittal anorectoplasty (PSARP) in low ARM
– In cases of hydrometrocolpos, vaginotomy may be necessary as newborn
– In cases of urinary retention, cutaneous vesicostomy may be necessary as newborn
• Definitive surgery at age 2–24 mo:
– Lower lesions: Approached through a PSARP
– Higher lesions: Laparotomy as well as PSARP
– In cloaca with a long common channel, when vagina will not reach perineum, can interpose a section of bowel between vagina and perineum
– Genitoplasty in cases of virilized genitalia
• Colostomy take-down a few months after definitive reconstruction, once anal dilations satisfactory
• Further urologic surgery later as indicated (ureteral reimplantation for VUR, bladder neck reconstruction for incontinence, augmentation for small capacity, poorly compliant bladder)
ADDITIONAL TREATMENT
Radiation Therapy
N/A
Additional Therapies
Clean intermittent catheterization may be necessary in cases of neurogenic bladder
Complementary & Alternative Therapies
N/A
ONGOING CARE
PROGNOSIS
• Bowel function (4):
– Voluntary bowel movements in 75% of ARM after definitive repair
– Fecal soiling occurs in about half of patients with voluntary bowel movements
– Total fecal continence (voluntary bowel movements, no soiling) in 37% of ARM; the lower the ARM, the chance of fecal continence
– Constipation in 48% of ARM; the lower the ARM, the more likely to have constipation
• Positive prognostic factors for fecal continence: Good perineal raphe, well-defined anal dimple, normal spine, brisk muscle reflex
• Urinary incontinence (4):
– Present overall in 9% of ARM
– Highest probability in cloaca (19% if common channel <3 cm, 69% if >3 cm)
• Renal failure (CKD): 1–6% (5)
COMPLICATIONS
• Ongoing problems usually due to underlying congenital abnormality, not iatrogenic causes
• NGB in many ARM, but rarely due to surgery
FOLLOW-UP
Patient Monitoring
• Close follow-up needed to manage long-term problems like fecal and urinary incontinence and associated urologic abnormalities
• Should follow through puberty and child-bearing age due to potential for hydrometrocolpos/ hematocolpos, infertility, ectopic pregnancy, delivery issues
Patient Resources
http://www.pullthrough.org/anorectal-malformation-treatment/
REFERENCES
1. Rink RC, Kaefer M. Surgical management of disorders of sexual differentiation, cloacal malformation, and other abnormalities of the genitalia in girls. In: Wein AJ, et al., eds. Campbell-Walsh Urology. 10th ed. Philadelphia, PA: Saunders Elsevier; 2012.
2. Marcelis C, de Blaauw I, Brunner H. Chromosomal anomalies in the etiology of anorectal malformations: A review. Am J Med Genet A. 2011;155:2692–2704.
3. Nah SA, Ong CC, Lakshmi NK, et al. Anomalies associated with anorectal malformations according to the Krickenbeck anatomic classification. J Ped Surg. 2012;47:2273–2278.
4. Peña A, Hong A. Advances in the management of anorectal malformations. Am J Surg. 2000;180:370–376.
5. Ganesan I, Rajah S. Urological anomalies and chronic kidney disease in children with anorectal malformations. Pediatr Nephrol. 2012;27:1125–1130.
ADDITIONAL READING
• Grano C, Aminoff D, Lucidi F, et al. Long-term disease-specific quality of life in children and adolescent patients with ARM. J Ped Surg. 2012;47:1317–1322.
• Herman RS, Teitelbaum DH. Anorectal malformations. Clin Perinatol. 2012;39:403–422.
See Also (Topic, Algorithm, Media)
• Anorectal Malformations: Imperforate Anus, Cloaca and Urogenital Sinus Anomalies Images 
• Disorders of Sexual Differentiation
• Exstrophy, Cloacal
CODES
ICD9
• 255.2 Adrenogenital disorders
• 751.2 Atresia and stenosis of large intestine, rectum, and anal canal
• 751.5 Other anomalies of intestine
ICD10
• E25.0 Congenital adrenogenital disorders assoc w enzyme deficiency
• Q42.3 Congenital absence, atresia and stenosis of anus without fistula
• Q43.9 Congenital malformation of intestine, unspecified
CLINICAL/SURGICAL PEARLS
ARM usually requires neonatal surgical interventions and follow-up to obtain and maintain fecal and urinary continence.