Anorectal Malformations

ANORECTAL MALFORMATIONS

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Introduction  Anorectal malformations are any birth defects that involve the anus and rectum.  The spectrum of anorectal malformations ranges from simple anal stenosis to the persistence of a cloaca.

A persistent cloaca is defined as a defect in which the rectum, vagina, and urethra all meet and fuse to form a single, common channel.

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Management of anorectal anomalies requires that the level of the rectal pouch and presence of fistula to the urinary tract or vagina be determined; this is important in early management.

Incidence  Ranges from 1 in 4000 to 5000 live births, being slightly more common in males.

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Evaluating the location of a fistula can be performed at a later time.

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The most common defect in both males and females is an imperforate anus with a fistula between the distal bowel and the urethra in males or the vestibule of the vagina in females. Low lesions are much more common than high lesions.

Gross Anatomy:

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The RECTUM is about 12cm long terminating about 3-4 cm anteroinferior to tip of coccyx and at this point is the anorectal angle which is made of a sling of the puborectalis muscle.

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May occur as part of the VACTREL group of anomalies;

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It is related posteriorly to the Inferior 3 sacral vertebra, coccyx, anococcygeal ligament, median sacral vessel and the sympathetic trunk and sacral plexuses.

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Anorectal malformations.

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Anteriorly it is related to the fundus of urinary bladder, the terminal part of ureters, the ductus deferens and the prostate in male while in females it is related to the rectovaginal septum, vagina $ rectouterine (Douglas’) pouch.

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The blood supply of the rectum is from the Superior rectal artery- a branch of the inferior mesenteric, middle rectal artery- a branch of the internal iliac and the inferior rectal artery- a branch of the internal pudendal artery, a branch of the internal iliac too.

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It is drained by the superior rectal vein a tributary to the portal system (inferior mesenteric) and the inferior rectal vein which drains to the systemic circulation (internal pudendal-internal iliac).

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It is innervated by the middle rectal plexus and also the sympathetic and parasympathetic nerves.

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The ANUS (superior 2/3=25mm $ inf. 1/3=13mm) is supplied by superior rectal artery and two inferior rectal arteries and drained by the middle rectal vein and the inferior rectal vein. Innervated by the inferior hypogastric plexus of nerves. Lymphatic drainage for superior $ inf. parts is to Inf. Mesenteric L.N $ Superficial inguinal L.N respectively.

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Vertebral body segmentation defects - Hemivertebra, Sacral agenesis, spins bifida, scoliosis, kyphosis. Cardiovascular - PDA, VSD Tracheo-Esophageal anomalies TO, esopahageal atresia Radial ray hypoplasia; unilateral Renal agenesis or ectopia Limb anomalies-amelia, phalyngeal anomalies-reduction or addition anomalies

Embryology

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From the 4th to 7th weeks, the Primitive cloaca, derived from the primitive hind gut (endoderm) is divided by the urorectal septum by its cauadal growth into:

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Ventral cloaca (urogenital sinus) - gives rise to the urinary bladder, urethra & vestibule of the vagina

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Dorsal cloaca(anorectal canal) - gives rise to the rectum & anal canal which fuses with the proctodeum-anal pit (an invagination of the ectoderm which eventually breaks down by the 8th week) to give rise to the anus

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The rectum develops from the hindgut while the superior 2/3 of the anus develops from the terminal end of the hind gut. The caudal one third of the anus develops from the proctodeum which is an ectodermal invagination.

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Failure of the urorectal septum to form results in a fistula between the bowel and urinary tract (in males) or the vagina (in females).

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The urorectal septum divides the cloacal membrane (composed of endoderm of cloaca $ ectoderm of proctodeum) into the urogenital (anterior) and anal (posterior) membranes.

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Complete or partial failure of the anal membrane to resorb results in an anal agenesis or stenosis. The perineum also contributes to development of the external anal opening and genitalia by formation of cloacal folds that extend from the anterior genital tubercle to the anal membrane. The perineal body is formed by fusion of the cloacal folds between the anal and urogenital membranes.

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Classification-high/low and fistula present /absent  Below  Low anomalies include a o anal agenesis (>90% with fistula) o stenosed anus o membranous atresia of anus (imperforate anus) o ectopic anus (often anteriorly) Anterior Displacement of the Anus ∗ This anomaly is more common in girls than in boys.

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It may be associated with a posterior rectal shelf and usually is characterized by constipation and straining with stool. The diagnosis of anterior displaced anus depends on finding the anus located close to the base of the scrotum or vaginal fourchette. If the center of the anus is located less than 33% of the total distance from vaginal fourchette (or base of scrotum) to coccyx, there is a high likelihood of difficulty with defecation.

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Breakdown of the cloacal membrane anywhere long its course results in the external anal opening being anterior to the external sphincter (ie, anteriorly displaced anus).

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Rectal atresia refers to an unusual lesion in which the lumen of the rectum is either completely or partially interrupted, with the upper rectum being dilated and the lower rectum consisting of a small anal canal.

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Anal Stenosis ∗ ∗

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In anal stenosis, the anal aperture may be very small and filled with a dot of meconium. Defecation is difficult, and there may be ribbon-like stools, fecal impaction, and abdominal distention. This malformation accounts for about 10% of cases of anorectal anomalies. This anomaly may not be apparent at birth and may be discovered on rectal examination of the infant with straining at stool.

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Physical examination

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A piece of gauze is placed around the tip of the penis can be used to check for particles of meconium filtered through this gauze.

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The presence of meconium in the urine and a flat bottom (flat perineum with short sacrum) are considered indications to create a protective colostomy.

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The presence of a single perineal orifice is pathognomonic of a cloaca.

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A palpable pelvic mass (hydrocolpos) reinforces the suspicions of a cloaca.

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The diagnosis of a vestibular fistula can be established by a careful separation of the labia to see the vestibule. Examination to exclude other abnormalities.

Imperforate Anal Membrane ∗ ∗

In imperforate anal membrane, the infant fails to pass meconium, and a greenish bulging membrane is seen in the anal aperture. After excision, bowel and sphincter function are normal.

Associated conditions - oesophageal atresia, duodenal atresia, and cardiovascular defects

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Anal Agenesis

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In the child with anal agenesis, an anal pit or dimple is present, and stimulation of the perianal area leads to puckering indicative of the presence of the external sphincter. If there is no associated rectoperineal fistula, intestinal obstruction occurs. Fistulas may also be vulvar in the female and urethral in the male.

Anorectal Agenesis

Investigations 1. Baby gram-X-ray showing head to toe. Air in the abdomen may indicate small intestinal atresia 2. No Fistula - Invertogram - X-ray with head down hips flexed at 90 degrees and legs flexed at 90 degrees  Baby held for several minutes to allow air to pass into the rectal pouch

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Anorectal agenesis accounts for 75% of total anorectal anomalies.

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Fistulas are almost invariably present. In the female, they may be vaginal or may enter a urogenital sinus, which is a common passageway for the urethra and vagina.

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In the male, fistulas are rectovesical or rectourethral (often prostatic urethra).

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Associated major congenital malformations are common Sacral defects and absence of internal and external anal sphincters are common.

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Rectal atresia The rectum $ anal canal are present but are separated (sometimes connected by a fibrous cord-a remnant of the atretic portion of rectum). Due to:  Abnormal recanalization of colon  Defective blood supply there Clinical presentation  Absence of anal opening o Anorectal (or anal) agenesis without fistula o Anal stenosis/agenesis

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Single perineal opening with Rectovaginal & Urethral openings immediately behind the clitoris – Cloaca Failure to pass stool/meconium Passing meconium/stool/air; o Per urethra (mixed with urine). o Per vagina. o Ectopic point in perineum. Abdominal distension and Vomiting

GICHOYA JUDY WAWIRA YR 2007

(Alternative - Prone cross-table lateral view) Best done after 16-24 hr of life - At birth the bowel is not distended; therefore, clinical and radiologic evaluations are not reliable during the first 16–24 hr of life.

To find out the level of the rectal atresia by viewing how far the gas has reached in relation to area where sphincter should be (Put a coin)  High lesions are above the levator.  Intermediate lesions are characterized by the rectal pouch ending within the levator,  low lesions, the rectal pouch has completely traversed the levator musculature, and a fistula usually is evident on the skin within the midline (ie, anteriorly displaced anus) 3. Fistula - Colostogram - Should be done under pressure to illustrate any fistula 4 .Abdominal U/S

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During the first 24 hrs of life, all these patients need an abdominal ultrasound evaluation to identify an obstructive uropathy especially in patients with;

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Cloaca (Cervix faces posteriorly not downwards thus may obstruct the ureters) Rectovesical (Bladder neck) fistula Rectoprostatic urethral fistula

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5..Perineal U/S or MRI If required, the level of the rectal pouch can be delineated more definitively by ultrasonography or magnetic resonance imaging.  Perineal ultrasonography may be useful in determining the distance between the rectal pouch and the anal skin,  In general, a lesion can be considered to be low if the distance from the rectal pouch to the skin, as determined by ultrasonography, is less than 1 cm.

Evaluation for other anomalies: 1-Chest x-ray 2-Lumbosacral x-ray 3-Abdominal pelvic ultrasonography 4-Kidney Ureter Bladder KUB x-ray 5-IVU 6-Echocardiography and ECG 7-Passage of nasogastric tube

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The proximal bowel as brought out as colostomy and the distal bowel as a mucous fistula.

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The second-stage procedure usually is performed 2-3 months later.

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Posterior saggital anorectoplasty it consists Surgically dividing the rectourinary or rectovaginal fistula "-Pull-through" of the terminal rectal pouch into the normal anal position. The patient is left with the protective colostomy to afford healing of the new anal anastomosis. In males, a urinary catheter remains in place to maintain the lumen of the urethra after repair of the rectourinary fistula.

Congenital anorectal anomalies often co-exist with other lesions, and the VATER or VACTERL association must be considered.

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Bony abnormalities of the sacrum and spine occur in about one third of patients with anorectal anomalies and consist of absent, accessory, or hemivertebrae and/or an asymmetric or short sacrum.  The absence of two or more vertebrae is associated with poor prognosis in terms of bowel and bladder continence.  Occult dysraphism of the spinal cord also may be present, and it consists of tethered cord, lipomeningocele, or fat within the filum.  Vesicoureteral reflux and hydronephrosis are the most common abnormalities, but other findings such as horseshoe, dysplastic, or absent kidney as well as hypospadias or cryptorchidism also must be considered.  The higher the anorectal malformation, the more frequent the associated urologic abnormalities.  In patients with persistent cloacas or rectovesical fistula, the likelihood of a genitourinary abnormality is approximately 90%. SURGICAL MANAGEMENT(depend on whether its low or high lesion)

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The third and final stage is performed a few months after the second stage, and it consists of colostomy closure. Anal dilatations are begun 2 weeks after the pull-through procedure and continue for several months after the colostomy closure. A 12-Fr dilator is used for newborns, which is increased up to 14- or 16-Fr for older infants.

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All stages of the surgery should be complete before 1 year of age when toilet training is meant to commence.

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Alternative is an extended posterior saggital anorectovaginoplasty

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Supportive care includes intravenous fluids, analgesia and antibiotics nasogastric tube for decompression in cases in intestinal obstruction.

Newer methods: that can be used include: (a) biofeedback mechanisms, (b) muscle transfer (Gracilis, Gluteus maximus), (c) tightening surgery, (d) Malone procedure ( Use of appendix/colonic conduit used to deliver anterograde enemas) and a permanent colostomy.

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The newborn infant with a low lesion can have a primary, single-stage repair procedure on the perineum without need for a colostomy. Three basic approaches may be used.

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For anal stenosis with a normal location of the anal opening, only simple serial dilatation is necessary. This should be performed daily (12-Fr size for newborn infants), and the size of the dilator should be increased progressively. Over several months, the anus ultimately will admit an index finger easily, and the dilatations can be discontinued.

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If the anal opening is anterior to the external sphincter (ie, anteriorly displaced anus) with a small distance between the opening and the center of the external sphincter and perineal body also is intact, a cutback anoplasty is performed.

PSARP + Abdominal approach 1. Rectovesical (Bladder neck) fistulae in males 2. Rectoprostatic urethral fistula 3.≥3cm high (bowel-skin distance) Cloaca

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A covered anus – open tract with a scissor then do routine dilatation;

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An ectopic anus - a plastic cut back operation (pena procedure);

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A stenosed anus – regular dilatation and

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Infants with intermediate or high lesions require a colostomy as the first part of a three-stage reconstruction. In males without fistulae fashioning of a colostomy is an emergency procedure.

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NB. In females with a fistulae a colostomy may be fashioned at 3months-times when food starts to solidify and cant go through the fistulae. The colon is completely divided junction of the descending and sigmoid colon region(this is because of good blood supply ,length of gut good mobilization)

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A membranous covering – incision of the membrane.

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Antegrade continence enema procedures may allow for continence in children without anal sphincter function by facilitating irrigation of the colon via a cecostomy or appendicostomy

Summary

PSARP only; 1. Rectobulbar urethral fistula 2. Anal Agenesis <1cm bowel-skin distance(No colostomy) 3. Perineal fistula (No colostomy) 4. <3cm Cloaca (Rectovaginal & Rectovestibular fistula) Post-operative management i)-4th day - Sitz baths to remove any bacteria ii)-10th day - When the wound has healed, start daily Hegars dilatation - Always start the previous days dilator then increase to the next size - to prevent stenosis. Aim for a size in keeping with the child's age (or mother's index finger). Once the size has been achieved, the mother is taught how to digitally dilate at home for some time. iii)-Confirm adequacy of anus before closure of colostomy iv)-If there is faecal soiling, reassess the sphincter by performing anal mapping under GA -If rectum misplaced, then put a colostomy & redo PSARP -If rectum is appropriately placed, then manage the patient medically - constipating diet & high daily enema

Prognostic factors 1. High lesions have poorer prognosis compared to low lesions (think of surrounding structures) High lesions -Females-Cloacal complex, rectovaginal fistula, rectocutaneous fistula Males-Rectovesical fistula, rectoprostatic fistula (commonest lesion) 2. Timing of the surgery-earlier surgeries have better results. 3. Bony abnormalities are associated with poorer prognosis, 4. Number of operations-first attempt operation would achieve best results 5. Timing of colostomy-done early to avoid megacolon and regain peristalsis ∗ ∗

Of the patients with low imperforate anus, 80-90% are continent after surgery; of those with high imperforate anus, only 30% achieve continence. Success or failure in achieving continence cannot be judged until after the age of 10 years.

Local Exam - Anus Normal gluteal cheeks, anal canal is in normal position, with no anal fissures or tags, no ulcers. Normal external female genitalia. Tender anal opening admitting the little finger, normal anal tone, blood stains on examining finger but no pus. Describing the colostomy stoma A colostomy bag was present over a double barreled colostomy about 3 cm left to the midline and about 2 cm above the umbilicus. The bag had little fecal material. The skin around the colostomy was slightly hyper pigmented compared with surrounding skin but had no ulcerations or marks from scratching. In a female the fistula could be: -Recto vaginal fistula -Recto urethral fistula -Rectovestibular fistula -Rectovesicular fistula

GICHOYA JUDY WAWIRA YR 2007

GICHOYA JUDY WAWIRA YR 2007

GICHOYA JUDY WAWIRA YR 2007