malformations.

Operative exploration of the asymptomatic contralateral groin remains controversial but is often

performed in infants younger than 2 years because of the reported 60% to 70% incidence of a patent

processus vaginalis on the opposite side.43 In a survey of the surgical section of the American Academy

of Pediatrics, 65% of the respondents perform contralateral exploration in male patients younger than 2

years, and 84% perform exploration for female infants up to 4 years of age.44 Direct visualization of the

contralateral groin can be performed using a laparoscope inserted either through the umbilicus or

through a side-viewing laparoscope inserted through the hernia sac. Experience with diagnostic

laparoscopy demonstrates that approximately one-third to one-half of children have a patent processus

vaginalis on the contralateral, asymptomatic groin, with higher rates in infants younger than 1 year.45,46

This approach avoids unnecessary contralateral groin exploration in about half of all children who

undergo surgery for unilateral inguinal hernia. However, the presence of a patent processus alone does

not necessarily translate into a clinically significant hernia, and via systematic review, the reported risk

of developing a metachronous contralateral inguinal hernia following open unilateral hernia repair in

children is 7.2%.47

The major risk of inguinal hernia repair in infants and children is related to general anesthesia.

Complications in pediatric inguinal hernia repair include wound infection, injury to the vas deferens or

testicular vessels, injury or displacement of the testicle, and recurrence. Fortunately, all these

complications are infrequent. The overall complication rate is higher for children requiring emergent

operation for incarcerated or strangulated hernia. Recurrent inguinal hernia following elective repair is

unusual and may be an indication of an underlying connective tissue disorder such as Ehlers–Danlos

syndrome.

Hydrocele

A hydrocele is a fluid collection that resides in the tunica vaginalis in the scrotum or the processus

vaginalis in the inguinal canal. A hydrocele may be present at birth, or it may occur acutely as a result

of an incarcerated hernia or torsion of the appendix testis. On examination, a hydrocele transilluminates

with a bright handheld light. A hydrocele is described as either communicating or noncommunicating

depending on whether there is direct patency between the hydrocele and the peritoneal cavity. A

history of intermittent fluctuation in the size of the hydrocele is generally diagnostic for communicating

hydrocele. A communicating hydrocele is synonymous with a patent processus vaginalis, and, therefore,

a communicating hydrocele is treated operatively in the same fashion. In male patients, a hydrocele of

the cord is a collection of fluid in the processus vaginalis separate from the tunica vaginalis. In female

patients, fluid trapped in the processus vaginalis is considered a hydrocele of the canal of Nuck. In

noncommunicating hydrocele, the isolated fluid collection is typically asymptomatic and tends to

spontaneously resolve before age 12 months. Operative management of noncommunicating hydrocele is

usually reserved for lesions that persist after this age, acute enlargement of the hydrocele, or if there is

any question of communication.

GASTROINTESTINAL DISORDERS

Neonatal Intestinal Obstruction

3 A variety of congenital anatomic defects, inherited metabolic diseases, and acquired physiologic

disorders may present as intestinal obstruction in a newborn. Neonatal intestinal obstruction is

characterized clinically by bilious emesis and is often associated with abdominal distention. Bilious

emesis in a neonate must be considered to be acute mechanical intestinal obstruction until proven

otherwise. Emergent surgical evaluation is warranted for any newborn with bilious emesis. Table 103-2

provides differential diagnoses for neonatal intestinal obstruction along with salient features of the

history, physical examination, and diagnostic studies.

DIAGNOSIS

Table 103-2 Neonatal Intestinal Obstruction

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The clinical presentation of neonatal intestinal obstruction depends, in part, on the site of obstruction

and the age of the infant. Clinical examination of the infant typically provides the surgeon with a

preliminary diagnosis and helps guide further diagnostic studies. Abdominal distention is a characteristic

physical finding with distal bowel obstruction, whereas the abdomen may be flat in proximal

obstruction. The presence of bile in the gastric contents or stool provides clinical evidence of the

location of an obstruction relative to the ampulla of Vater. Bilious emesis in an infant or child should be

considered an anatomic obstruction requiring emergent surgical evaluation. An infant with bilious

emesis who has already passed meconium and has tolerated feeding is unlikely to have intestinal atresia

and more likely to have intestinal malrotation with midgut volvulus. If volvulus is suspected, emergent

evaluation must be performed to diagnose and prevent catastrophic bowel injury or death.

Definitive diagnosis of neonatal intestinal obstruction may often be made by physical examination

and readily available radiologic studies. Incarcerated inguinal hernia is an important cause of neonatal

bowel obstruction, and examination leads to a straightforward diagnosis. Some congenital conditions

have clearly recognizable features and may be associated with anatomic intestinal obstruction. For

example, infants with trisomy 21 have a higher probability of having duodenal atresia or Hirschsprung

disease than the general population. An approach to imaging the neonate suspected of having an

intestinal obstruction is to obtain a plain abdominal radiograph, followed by either a contrast enema or

an upper gastrointestinal series. Plain films of the newborn abdomen can be extremely useful because

swallowed gas acts as a contrast agent. For example, duodenal atresia gives rise to a dilated, gas-filled

stomach and duodenum proximal to the obstruction; the remainder of the bowel remains gasless, giving

rise to the “double-bubble” appearance on plain films. Other causes of proximal intestinal obstruction

may lead to a microcolon on contrast enema, which is a small, unused but otherwise normal colon. If a

retrograde contrast enema does not pass into the dilated segment of bowel, an upper gastrointestinal

series may be useful to identify a more proximal obstruction. Upper gastrointestinal series is also the

most useful diagnostic test for intestinal malrotation.

Several medical conditions of the newborn appear clinically similar to mechanical intestinal

obstruction (see Table 103-2). In particular, bilious emesis from ileus secondary to neonatal sepsis is not

uncommon. Congenital hypothyroidism is an infrequent and medically treatable condition that can

produce delayed intestinal motility that mimics mechanical intestinal obstruction.

Intestinal Atresia or Stenosis

Embryology and Anatomy

The embryonic intestine undergoes segmental development during the third week of gestation. The

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septum transversum demarcates the developing foregut from the midgut. The midgut can be considered

a tubular structure that progressively undergoes several predictable, developmental stages: (a)

elongation; (b) herniation from and reduction into the coelomic cavity; (c) rotation; and (d) fixation of

the mesentery to the posterior body wall.

Several different types of intestinal atresia are clinically observed (Fig. 103-7). Type I atresia is an

intraluminal web or diaphragm that can either be complete or fenestrated with intact seromuscular

layers of bowel. Type II and IIIa atresia are believed to be a result of in utero mesenteric vascular

accidents. Experimental interruption of the fetal mesenteric blood supply in utero leads to this type of

atresia.48,49 Type IIIb atresia, also known as the apple-peel or Christmas tree deformity, has complete

mesenteric discontinuity, with the distal bowel concentrically surrounding a singular mesenteric blood

supply. Type IV atresia has multiple segmental areas of discontinuous bowel. Type IIIb and IV atresia

are thought to be consequences of major and multiple fetal mesenteric vascular interruption.

At least 90% of infants with congenital intestinal obstruction of the small bowel have complete

atresia, whereas the remaining children have either stenoses or fenestrated intraluminal webs. The most

common location is the distal ileum, and multiple areas of atresia are discovered in 3.6% to 20% of

these infants.38 Infants with fenestrated intraluminal webs may have a small, often eccentric opening

only millimeters in diameter. These infants may not have obstructive symptoms until the introduction of

solid food at 6 to 12 months of age and present with feeding intolerance, failure to thrive, or abdominal

pain.

Congenital colonic atresia is a distinctly unusual condition. In a contemporary series of 277 infants

treated with intestinal atresia, only 21 children had colonic atresia.50 Similar to small bowel atresia,

colonic atresia is believed to reflect fetal mesenteric vascular injury. Given the distal nature of colonic

atresia, initial feeding may be well tolerated and definitive diagnosis may be delayed for several days.

The diagnostic evaluation and surgical treatment of colonic atresia is identical to the approach used for

small bowel atresia. Colonic atresia may be associated with abdominal wall defects, skeletal or cardiac

defects, or coexisting intestinal atresia.

Clinical Presentation

The actual incidence rate of congenital intestinal atresia is unknown. Reported estimates in the United

States are 3.5 to 3.75 cases per 10,000 total births.51 Infants with jejunal or ileal atresia have a low

incidence rate of significant associated anomalies. Approximately 10% of infants with gastroschisis have

intestinal atresia or stenosis secondary to mechanical interruption of the mesenteric vascular supply.

Detection of maternal polyhydramnios on routine prenatal ultrasound screening can be an indication

of proximal bowel obstruction caused by the interruption of normal amniotic fluid absorption in the

fetal gut.52 Following delivery, the classic clinical presentation of intestinal atresia is bilious emesis,

abdominal distention, and failure to pass meconium. The degree of abdominal distention depends on the

site of obstruction, the infant’s age, and the efficacy of proximal decompression. Abdominal distention

may be absent with proximal intestinal atresia. Distal intestinal atresia may lead to abdominal

distention with visible or palpable intestinal loops on examination. Rectal examination and evaluation of

stool character remains important when intestinal obstruction is suspected.

Diagnosis

Following history and physical examination, plain radiographic abdominal films should be obtained.

Plain films in jejunal or ileal atresia demonstrate marked gaseous distention of the proximal intestine

with gasless distal small bowel and colon. Haustral markings are normally not apparent in the neonatal

colon, and, therefore, discrimination between small bowel and colon in the newborn is difficult without

intraluminal contrast. A contrast enema is generally obtained to confirm the diagnosis of jejunoileal

atresia. A diminutive, unused but otherwise normal microcolon is typical of proximal intestinal

obstruction. The inability to reflux contrast into the proximal, dilated small bowel segment is diagnostic

for congenital intestinal obstruction. This radiographic finding, in conjunction with the clinical setting,

warrants operative exploration. An upper gastrointestinal series is unnecessary and may increase the

risk of further emesis and aspiration in the newborn with obstruction. Incomplete obstruction from a

fenestrated intraluminal web may require more sophisticated imaging techniques such as catheterdirected enteroclysis.

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Figure 103-7. Classification of intestinal atresia. Type I, muscular continuity with a complete web. Type II, mesentery intact,

fibrous cord. Type IIIa, muscular and mesenteric discontinuous. Type IIIb, apple-peel deformity. Type IV, multiple atresias.56

Treatment

Anatomic lesions causing neonatal intestinal obstruction require operative treatment. Whereas

malrotation with midgut volvulus requires emergent diagnostic workup and operative intervention,

obstruction resulting from intestinal atresia is generally not associated with life-threatening physiologic

disturbances. Therefore, initial treatment is aimed at treating any other associated problems, confirming

diagnosis, and preparing the infant for an operation. During this period, the infant should always have

an orogastric or nasogastric tube in place to provide proximal decompression of the obstructed bowel.

The operative strategy in treating intestinal atresia is to restore gastrointestinal tract continuity while

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preserving as much intestinal length as possible. The operation is straightforward and an end-to-end or

end-to-oblique (end-to-back) anastomosis is typically performed (Fig. 103-8). Short-segmental bowel

resection and excision of an intraluminal web or diaphragm are done when necessary. Visual inspection

and instillation of intraluminal saline or air to exclude distal atresia or web prior to anastomosis is

important to evaluate patency of the downstream bowel. The size discrepancy between the proximal

and distal bowel is usually considerable, and delayed postoperative bowel motility is common. Some

surgeons advocate the use of technical procedures to improve emptying of the proximal bowel by

reducing overall bowel diameter. These procedures include resection, plication, and tapering

enteroplasty. Complex atresia associated with apple-peel deformity or multiple segmental atresias may

require multiple serial anastomoses to preserve as much bowel length as possible. The ileocecal valve is

preserved whenever possible, allowing improved tolerance of enteral nutrition in infants with limited

small bowel length. It is estimated that approximately 40 cm of small bowel without an ileocecal valve,

compared with 15 to 20 cm with an ileocecal valve, is sufficient for long-term enteral feeding tolerance

in the neonate.53 Contemporary management of colonic atresia includes primary anastomosis when

technically possible.

Results and Outcome

Currently, the overall survival rate for infants treated for intestinal atresia or stenosis (including

duodenal atresia) exceeds 93% in most large series.50,54 Mortality in these infants is generally related to

cardiac anomalies, birth weight less than 2 kg, and associated congenital anomalies.55 Infants with a

limited amount of intestinal length for nutritional absorption (short bowel syndrome with less than 40

cm) usually require long-term TPN and are at moderate to high risk for sepsis and liver injury. Infants

with normal gastrointestinal length may still have prolonged intestinal dysfunction and dysmotility for

several weeks.

Congenital Duodenal Obstruction

Causes of duodenal obstruction in the newborn include duodenal atresia or stenosis, duodenal

intraluminal web, and annular pancreas. Because of the common embryologic basis, clinical

presentation, and treatment, these entities are considered jointly.

Figure 103-8. A,B: The end-to-oblique anastomosis for small bowel atresia. C: An extension of the distal enterostomy along the

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antimesenteric border may be used to create proximal and distal lumens of equal size for anastomosis.

Embryology and Anatomy

The duodenum is derived from both the caudal segment of the foregut and the cranial segment of the

midgut. Duodenal development is intimately related to the developing pancreaticobiliary system. The

fetal pancreas arises from paired dorsal and ventral foregut diverticula during week 6 of gestation. The

dorsal anlage gives rise to the body and tail of the pancreas as well as the main pancreatic duct. The

ventral anlage migrates 180 degrees to fuse with the dorsal gland, forming the uncinate process and the

distal portion of the duct of Wirsung (Fig. 103-9). An annular pancreas is characterized by glandular

persistence surrounding the duodenum at the site of the embryonic ventral anlage. It is invariably

associated with intrinsic duodenal obstruction, and a patent accessory pancreatic duct is common (Fig.

103-10).57

It is believed that congenital duodenal obstruction results from abnormalities of pancreatic

development, failure of duodenal recanalization, or vascular compromise to the duodenum. Duodenal

atresia may occur with or without seromuscular continuity, and an intraluminal duodenal web may

occur with or without fenestration. The most frequent location for duodenal atresia is in the descending

duodenum distal to the ampulla of Vater. Most series report a 5% to 10% incidence of duodenal atresia

proximal to the ampulla, giving rise to nonbilious gastric contents and emesis. Another important

variant is a periampullary web projecting distally into the duodenal or jejunal lumen, forming a “windsock” deformity (Fig. 103-11). In this instance, the ampulla must be clearly identified before excision

and repair because of the proximity of the ampulla to the web.

Figure 103-9. Normal embryologic development of the duodenum, pancreas, and bile ducts. A: Fifth gestational week. B: Sixth

week. C: Seventh week. D: Eighth week.

Clinical Presentation

The incidence rate of congenital duodenal obstruction is estimated to be about 1 in 6,000 to 10,000

births.58 About 30% of these infants have trisomy 21.59 Infants born with duodenal atresia should be

examined with a high degree of suspicion for trisomy 21 and undergo routine karyotype analysis. Other

associated anomalies such as congenital heart disease, genitourinary tract malformations, and

musculoskeletal disorders are common in these infants, and appropriate preoperative workup is

necessary.

Congenital duodenal obstruction most commonly presents in the first 24 to 48 hours of life with

feeding intolerance and bilious emesis; duodenal obstruction proximal to the ampulla of Vater results in

nonbilious emesis. On physical examination, infants with untreated duodenal obstruction may have a

palpable epigastric mass, and gastric peristaltic waves may be visible. The collapsed and unused distal

2961

small intestine typically does not produce diffuse abdominal distention. Partial duodenal obstruction

from a fenestrated web may not produce symptoms in the newborn period, and delayed diagnosis is

common.

Figure 103-10. Annular pancreas. A: The associated duodenal atresia is shown. B: The relationships of the annular pancreas to the

common bile duct and main and accessory pancreatic ducts are shown in cross section.

Figure 103-11. Anatomic forms of duodenal atresia (A–C) and webs (D,E). In particular, (E) demonstrates the unique wind-sock

deformity. This lesion is important and potentially confusing because the point of obstruction is not at the apparent point of

change in luminal diameter.

Diagnosis

Prenatal diagnosis of duodenal atresia is possible given contemporary fetal ultrasound techniques.

2962

Following birth, infants with suspected duodenal atresia should obtain plain abdominal radiographs. The

classic radiographic finding of duodenal atresia is a double bubble from the air-filled stomach and

duodenum (Fig. 103-12). In complete duodenal obstruction, no gas is seen distal to the duodenum; in

this setting, the plain film is sufficiently diagnostic that no further imaging of the gastrointestinal tract

is necessary. If there is incomplete obstruction, gas may be seen distally in the small or large intestine.

Infants with suspected incomplete obstruction at the duodenal level may have either a fenestrated web

or volvulus secondary to malrotation. Given the need for emergent operative intervention in

malrotation with acute volvulus, an urgent upper gastrointestinal series with contrast should be strongly

considered to exclude a neonatal surgical emergency. Importantly, all anatomic lesions causing neonatal

duodenal obstruction require operative repair using a similar approach.

Treatment

Following expedient treatment of any associated life-threatening medical conditions and preoperative

evaluation, the operative goals are to restore gastrointestinal continuity without sacrificing intestinal

length or absorptive surface area. Because most lesions causing congenital duodenal obstruction are

near the ampulla of Vater, great care must be exercised in treatment to avoid inadvertent injury to the

ampulla or the pancreas.

Figure 103-12. Classic radiographic appearance of duodenal atresia. There is a double bubble of gas in the stomach and the

proximal duodenum, with no gas in the distal intestinal tract.

Congenital duodenal atresia is treated by duodenoduodenostomy. Duodenal obstruction secondary to

annular pancreas is also treated by duodenoduodenostomy. Direct division of annular pancreas is not

performed because this does not address the underlying intraluminal duodenal obstruction, and there is

significant risk of injury to the accessory pancreatic duct (see Fig. 103-10).

Duodenoduodenostomy is performed by making a transverse incision in the dilated, proximal

duodenum and a longitudinal incision in the unused, downstream duodenum. The lumens are sutured

together to form a diamond-shaped anastomosis (Fig. 103-13).60 Downstream duodenal patency should

be demonstrated by passing a catheter or infusing saline or air distally to avoid overlooking

synchronous distal intestinal atresia. Successful and efficacious laparoscopic duodenal atresia repair has

also been reported.61

Duodenal webs are excised through a longitudinal duodenotomy. The wind-sock duodenal web must

be clearly identified because the visible transition from the distended, proximal duodenum to the small,

downstream duodenum may be several centimeters distal to the base of the web. The ampulla of Vater

must be unequivocally identified before duodenal web excision to avoid injury. Closure of the

longitudinal duodenotomy is performed transversely to avoid narrowing of the duodenum.

There is usually great size discrepancy between the dilated, proximal pouch and the distal duodenal

lumen, leading some surgeons to advocate procedures designed to reduce the diameter of the proximal

duodenum in an effort to facilitate improved postoperative bowel motility. The efficacy of these

procedures, which include tapering duodenoplasty and duodenal plication, has been described in

anecdotal fashion without randomized comparison.

2963

Results and Outcome

After successful operative repair of duodenal atresia or stenosis, delayed gastric emptying is common

and typically manifests as enteral feeding intolerance. Patience and persistence are essential during the

postoperative period. Surgical outcomes after repair of congenital duodenal obstruction are

excellent,59–62 with perioperative survival exceeding 95%. Perioperative mortality is generally related

to other congenital anomalies and, in particular, congenital heart disease in infants with trisomy 21.

Other late problems may be encountered that reflect gastroduodenal motility issues such as poor gastric

emptying, gastroesophageal reflux, and duodenal dilatation. These symptoms may appear several

months to years following repair and, therefore, long-term surgical follow-up remains important.

Figure 103-13. Diamond-shaped duodenoduodenostomy for repair of duodenal atresia.

Anorectal Malformations (Imperforate Anus)

Embryology

By week 5 of gestation, the fetal cloaca is identifiable with the adjacent hindgut, allantois, and vestigial

tailgut (Fig. 103-14). The mesoderm of the urorectal septum extends caudally to fuse with the cloacal

closing plate. Fusion of the lateral cloacal ridges completes division of the cloaca into the rectum and

the urogenital sinus. The caudal aspect of the urorectal septum forms the perineal body. The anal

membrane normally ruptures during week 8 of gestation, completing the patency of the distal rectum to

the skin. Further development of the urogenital sinus leads to the formation of the urethra and the

bladder. In female infants, the uterus and the proximal vagina develop from the müllerian ducts. The

diverse anatomic variation observed with anorectal malformations is thought to reflect anomalous or

interrupted development of these structures during normal embryogenesis.

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Figure 103-14. Normal embryologic division of the cloaca by the urorectal septum into the ventral urinary tract and the dorsal

rectum. This process is normally completed by the ninth or tenth week of gestation.

Figure 103-15. The normal relations of the pelvic striated muscle complex and the rectum. A: Normal male anatomy. B: Coronal

view showing individual components of the striated muscle complex. C: Sagittal view of normal anatomy.

2965

Anatomy and Classification

The normal anatomy of the anus and the rectum is reviewed in previous chapters. Normally, the rectum

descends to the perineum and ultimately to the anal orifice through a striated muscle complex in the

pelvis resembling a funnel. The striated muscle complex is under voluntary control and is responsible

for providing fecal continence (Fig. 103-15). Contiguous portions of the levator ani, the external

sphincter, and the puborectalis muscles compose the striated muscle complex. These anatomically indistinct

components of the muscle complex act together to provide control of defecation. The concept of the

striated muscle complex and anatomic relationships leading to normal fecal continence with respect to

anorectal malformations has evolved from both clinical and anatomic data as described by Peña.63

Because of the variety of anorectal malformations observed, different classification systems have been

proposed in an attempt to characterize the defects. A summary of the Wingspread Classification is

provided in Table 103-3. This anatomically descriptive classification scheme is useful in planning the

operative management of anorectal malformations.

CLASSIFICATION

Table 103-3 Anatomic Classification of Anorectal Malformations

In male subjects, the two most common anorectal malformations observed are low imperforate anus

with a perineal fistula (Fig. 103-16) and high anorectal agenesis with a rectoprostatic urethral fistula

(Fig. 103-17). Male patients without a visible perineal fistula are assumed to have high imperforate

anus with a rectourethral fistula until proven otherwise. In female subjects, the most common

malformation encountered is low imperforate anus with a fistula from the rectum to either the perineal

body or the vaginal vestibule (Fig. 103-18). As these malformations result from developmental arrest at

various times during migration of the urogenital septum, considerable anatomic variability exists in

both male and female subjects.

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Figure 103-16. Male infant with low imperforate anus and perineal fistula. Note that the fistula is anterior to the striated muscle

complex.

A common anatomic feature of imperforate anus is incomplete rectal descent to the perineum.

Consequently, the rectum is not completely within the striated muscle complex. The caudal portion of

the striated muscle complex remains a solid mass of striated muscle, whereas the cephalad portion may

be normally positioned circumferentially around the rectal pouch. In low imperforate anus, the rectum

nearly reaches the perineum, and the configuration of the striated muscle complex surrounding the

rectum more closely approximates normal. With high imperforate anus, less striated muscle surrounds

the rectal pouch. All anorectal malformations are considered to have some component of striated muscle

complex hypoplasia and dysfunction, although the physiologic effects are variable. Low anorectal

lesions have a more favorable prognosis for fecal continence than intermediate or high lesions.

Classic delineation between low and high anorectal malformations is made anatomically at the

pubococcygeal line. The vast majority of low lesions have associated perineal or vestibular fistulas.

High imperforate anus has a blind-ending rectal pouch above the pubococcygeal line and, therefore,

above the striated muscle complex (or levator ani).

Associated Anomalies

Associated anomalies in infants with anorectal malformations are common and may be found in more

than 70% of patients. The VACTERL (vertebral, anal, cardiac, tracheal, esophageal, renal, and limb)

association is important and requires consideration in any infant with imperforate anus. Vertebral

anomalies are common and include sacral dysplasia and agenesis. Infants with sacral anomalies

commonly have high imperforate anus and sacral nerve dysfunction that can lead to poor long-term

fecal continence and neurogenic bladder. A variety of spinal cord malformations can also be observed in

these infants, including tethered spinal cord syndromes and some myelodysplastic syndromes. During

the neonatal period, these spinal lesions may be detected by using ultrasound or magnetic resonance

imaging (MRI), and surgical treatment may be necessary within the first 8 to 18 months of life.

Tracheoesophageal fistula with or without esophageal atresia is estimated to occur in about 10% of

infants with anorectal malformations. Renal anomalies are the most common associated abnormalities

with anorectal malformations and include both upper and lower tract conditions. Genitourinary

screening in the form of a renal ultrasound and voiding cystourethrogram is routinely performed.

Cardiac anomalies are common and screening echocardiography is clinically indicated. Limb

abnormalities, in particular, involvement of the radius, complete the associated anomalies defined by the

acronym.

Clinical Presentation

The incidence rate of anorectal malformations is estimated at 1 in 2,524 to 5,000 live births,64 with a

slightly higher rate in males. Careful examination of the neonatal perineum reveals the diagnosis. If

unrecognized and left untreated, high imperforate anus eventually leads to signs and symptoms of

complete bowel obstruction characterized by abdominal distention, feeding intolerance, and bilious

emesis. Because of the nearly uniform rectourethral or rectovesicular fistula in males with high lesions,

some of these infants will pass meconium or gas through the urethra during urination. In contrast,

2967

infants with low malformations typically pass meconium through a perineal or vestibular fistula within

the first 24 hours of life. Occasionally, infants with large perineal fistulas are not diagnosed with an

anorectal malformation until progressive constipation is noted weeks to months after birth.

In male infants, more than 95% of low malformations are associated with either a thin anal

membrane or a fistula to the perineum or the scrotal raphe. The presence of a “bucket-handle” skin

deformity at the presumptive anal dimple is also diagnostic of a low lesion. Infants with high

malformations typically lack anal skin dimpling, have a flat gluteal contour, and may have little or

absent contraction of the external sphincter with cutaneous stimulation. In female infants, 90% to 95%

of low malformations have a perineal or vestibular fistula. In both male and female infants, a perineal

fistula may not become apparent in the first 12 to 24 hours of life until meconium progresses distally

through the rectum into the fistula.

Figure 103-17. Male infant with high imperforate anus, showing the pubococcygeal line, ischium, and striated muscle complex. A:

The rectal pouch ends cephalad to the pubococcygeal line. This location of the rectourethral fistula is typical. B: Coronal view

showing incomplete development of the rectal pouch within the striated muscle complex. The rectourethral fistula is shown.

2968