*4.2.1 Embryology*

During the 5th week of gestation, the midline urorectal septum descends in a caudal direction toward the cloaca and divides into ventral and dorsal portions. The ventral bud becomes the urogenital sinus, which develops into the urethra and bladder. The dorsal bud becomes the rectum and anal membrane. The anal membrane involutes around week 8, thereby forming the anus. Dysgenesis can occur at any time point, allowing for variability in clinical presentation.

An anatomical distinction based on the pathology's relation to the levator ani muscle complex was first described by Pena. The levator ani complex supports the pelvic floor and is composed of three striated muscles: the puborectalis, the pubococcygeus and the iliococcygeus. The puborectalis encircles the base of the rectum, helps to form the external anal sphincter and thereby plays an integral role in regulating defecation. Anorectal dysgenesis above the levator ani muscles is considered a "high" lesion. Conversely, lesions inferior to the levator ani complex are termed "low" malformations. Generally speaking, higher malformations tend to cause more severe issues with controlling defecation as the neuromuscular development between the levator ani complex and growing recto-anus is compromised to a greater degree.

#### *4.2.2 Clinical presentation*

Failure to pass meconium in the first 24–48 h of life. Physical exam will reveal abdominal distention and absence of anus. A subtle opening in the perineum through which small amounts of meconium pass may be present and indicates an anoperineal fistula in the setting of a low imperforate anus. This is the most common pathology seen. In females, low lesions may also be associated with a rectovestibular fistula, and meconium may be expressed through the vagina. Elimination of meconium during urination indicates rectourethral or rectovesicular fistula and a high rectal pouch.

#### *4.2.3 Diagnosis*

Diagnosis is made upon physical examination of the perineum. Historically, an invertogram was performed to evaluate the length of atresia. In this study, a radiopaque marker is placed on the infant's bottom, where the anus would normally be located, and the infant is placed in a head down position to allow air to ascend at the most inferior point in the rectum. Lateral films of the pelvis are then obtained. The distance between the marker and distal rectum indicate the level of pathology high vs. low. Now, ultrasound is preferred.

Anorectal malformations are part of the VACTERL syndrome and most commonly associated with concomitant genitourinary defects. In addition to a renal ultrasound, a voiding cystourethrogram should be obtained, especially if a rectourethral/rectovesicular fistula is suspected as this can help delineate the tract. Plains films of the chest, limbs and spine as well as an echocardiogram help identify the presence of other anomalies. Any other life-threatening co-morbidities take precedence, and a temporary diverting ostomy can be placed until definitive repair can be safely performed, usually between 8 and 12 months of age.

#### *4.2.4 Surgical management*

Posterior sagittal anorectoplasty (PSARP) is the surgical procedure performed. The infant is placed in a prone jack-knife position. If a perineal fistula is present, an incision is made around the fistula and carried posteriorly toward the coccyx. If no perineal fistula is present, the incision starts inferior to the coccyx and is carried down to the perineum. It is imperative to remain midline. This is ensured by visualizing striated muscle fibers, which run perpendicular to the incision. If fat is encountered during the dissection, this indicates that the operator has deviated from midline and entered the lateral ischioanal/ischiorectal space. The rectum is identified by its overlying glistening fascia and then freed circumferentially, beginning posteriorly and advancing anteriorly until the fistula is encountered. The fistula is resected. After the fistula is taken down, the anterior rectal wall is freed from its surrounding structures. In females, the anterior rectum lies in close proximity to the posterior vaginal wall and in males, the prostate and bladder. The anterior rectal wall is gently dissected off these structures up to the peritoneal reflection. Complete, circumferential dissection of the rectum will allow for tension-free pull down and anastomosis. The rectum is situated in its anatomic position in the muscle complex. The muscle complex is repaired around the properly positioned rectum and the neoanus is created by suturing mucosa to the perineum.

#### *4.2.5 Outcomes*

Long terms outcomes are dependent on the level of pathology—high versus low anorectal dysgenesis—and the extent of neuromuscular development of the levator

**103**

**Author details**

Piedmont Healthcare, Statesville, NC, USA

provided the original work is properly cited.

\*Address all correspondence to: rverma1024@gmail.com

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Richa Verma

*Congenital Anomalies of the Gastrointestinal Tract DOI: http://dx.doi.org/10.5772/intechopen.92588*

**Acknowledgements**

figures numbered as 1-to-6.

ani complex and rectum. Almost all children will require some degree of lifestyle modifications to manage fecal incontinence or, conversely, chronic constipation. This is achieved by strict bowel regimens with enemas or cathartics. In more severe cases, a cecostomy or appendicostomy may be required to allow for daily antegrade

The contribution of Natalia Louise Smith is greatly appreciated for drawing the

enemas. Worst case scenarios may necessitate a diverting ostomy.

*Congenital Anomalies of the Gastrointestinal Tract DOI: http://dx.doi.org/10.5772/intechopen.92588*

ani complex and rectum. Almost all children will require some degree of lifestyle modifications to manage fecal incontinence or, conversely, chronic constipation. This is achieved by strict bowel regimens with enemas or cathartics. In more severe cases, a cecostomy or appendicostomy may be required to allow for daily antegrade enemas. Worst case scenarios may necessitate a diverting ostomy.
