It is important to recognize the various anal and rectal disorders in infants and children. In this chapter, the following disorders are discussed in succession:

1. Hirschprung disease

2. Imperforate anus

3. Rectal prolapse

4. Anal fissure

5. Anal abscess and Fistula in ano

Patient Story

An 8-week-old girl is brought to your office with abdominal distention and constipation. On digital examination of her anus she has an episode of explosive diarrhea and flatus. A plain radiograph shows stool impaction and a contrast enema reveals a transition zone in the sigmoid colon (Figure 62-1). A suction biopsy confirms the diagnosis of Hirschsprung disease. An enema regimen was started and 3 weeks later she underwent a primary pull through operation.

Introduction

Hirschsprung disease is a developmental disorder of the enteric nervous system characterized by absence of ganglion nerve cells in the myenteric and submucosal plexuses of the distal intestine.

Synonyms

Hirschsprung disease; partial or total aganglionosis; congenital megacolon.

Epidemiology

• US: 1 case per 5400 to 7200 newborns.

• Worldwide: 1 case per 1500 to 7000 newborns.¹

• Most cases are diagnosed by 2 years of age.

Etiology and Pathophysiology

• Congenital aganglionosis of the distal bowel leads to impaired bowel peristalsis with constipation. The aganglionosis usually begins in the anus and continues proximally for a variable distance.

• There are two theories for the aganglionosis: The incomplete migration of ganglion cells from the neural crest to the distal bowel or the dysfunctional maturation or apoptosis of primitive nerve cells. There is increasing evidence that mutations in a variety of genes, including the RET proto-oncogene, may play a key role in the etiology.^2,3

Risk Factors

• Race: No racial predilection.

• Sex: Male to Female ratio 4:1.

• About 10 percent of patients have a positive family history.

• Trisomy 21.

Diagnosis

History

• Neonatal period.

  • Consider the diagnosis in any newborn with delayed passage of first meconium. beyond the first 24 hours, abdominal distention, and repeated vomiting.

  • Signs of intestinal obstruction with bilious vomiting, poor feeding, and failure to thrive.

• Children.

  • Chronic constipation, abdominal distension since birth.

  • Soiling and overflow incontinence.

• Enterocolitis.

  • Ten percent of all patients present with fever, abdominal distension, and diarrhea caused by enterocolitis, which can progress to colonic perforation and life-threatening sepsis.

Clinical Features

• Physical examination may reveal a distended abdomen and/or a hypertonic anus with empty rectum.

• Digital rectal examination may result in explosive expulsion of stool.

Rectal Biopsy

• Definitive diagnosis is made by histologic evaluation of a rectal biopsy.

• A suction rectal biopsy that samples rectal mucosa and submucosa is routinely used in neonates and small children and can be performed at the bedside.

• Alternatively, full-thickness rectal biopsies are taken under general anesthesia in the OR.

Laboratory Testing

• White blood cell count and C-reactive protein may be elevated in children with enterocolitis.

• Chemistry panel: Electrolytes are usually normal. Children with diarrhea may have findings consistent with dehydration.

Imaging

• Plain abdominal radiographs may show distended bowel without air in the rectum.

• Contrast enema—A narrowed distal colon representing the pathologic segment with proximal dilation of the normal bowel is the classic finding (Figure 62-1).

Anorectal Manometry

• Demonstrates decreased relaxation of the diseased segment.

• May not be available in all facilities and is not routinely used for neonates.

• Most useful in the evaluation of an older child with chronic constipation to rule out Hirschsprung disease.

Differential Diagnosis

• Functional constipation—Usually not associated with systemic symptoms, failure to thrive and bilious vomiting.

• Cystic fibrosis—Can present with meconium ileus early in life (see Chapter 51, Cystic Fibrosis).

• Hypothyroidism—Constipation is often a manifestation along with other systemic findings.

• Intestinal obstruction—May present with similar symptoms and may need to rely to imaging studies to determine the location of the obstruction.

• Ileus—Usually more acute and does not present with systemic manifestations such as failure to thrive.

• Neonatal sepsis—Always need to be considered in the newborn, but signs other than constipation usually evident (see Chapter 187, Congenital and Perinatal Infections).

• Intestinal Motility Disorders—May present with symptoms similar to Hirschsprung but without the systemic manifestations.

• Low imperforate anus with large perineal fistula opening—Usually can be seen on physical examination.

Management

• Definitive treatment is surgical—To remove the aganglionic portion of bowel, which can be performed semielectively.^4,5 SOR A

• Preoperative considerations include treatment of complications of unrecognized or untreated disease until reconstructive surgery can be performed:

  • Constipation—Rectal stimulation, enemas, laxatives.

  • Dehydration—Resuscitation with intravenous fluids.

  • Bowel obstruction—Naso-/orogastric tube decompression.

  • Enterocolitis—Colonic irrigations, broad-spectrum antibiotics.

Medications

• Antimicrobial therapy—Perioperatively and in cases of enterocolitis. SOR C

• Laxatives. SOR C

Surgery

• Surgical treatment options:

  • Primary pull-through procedure without diverting colostomy.

  • Diverting colostomy with secondary definitive repair.

• Contraindications to a one-stage procedure include very distended proximal bowel, enterocolitis, bowel perforation, and malnutrition.

Referral

• Pediatric surgeon.

• Pediatric gastroenterologist.

• Geneticist if associated with a syndrome.

Prevention and Screening

• Hirschsprung disease can be associated with different syndromes, including trisomy 21.⁶

Prognosis

• Left untreated, Hirschsprung disease results in a high rate of mortality.

• Common postoperative problems include obstructive symptoms, fecal soiling, and enterocolitis.⁷

• Constipation can be caused by mechanical obstruction, residual aganglionosis, motility disorder, or habitual stool-holding behavior.

• The long-term outcome after definitive pull-through procedure is good.^4,5 SOR B

• Most adolescents and adults with Hirschsprung disease report normal sexual function.

Follow-Up

• Despite proper corrective surgery patients remain at high risk of developing constipation, soiling, and enterocolitis.⁷

Patient Story

A newborn boy is found to have noticeably flat buttocks and no anal opening on his first physical examination (Figure 62-2). The pediatric surgeon is consulted and the child is given nothing by mouth (NPO). The following day fecal particles are noted in his urine. A cross-table radiograph shows a rectal stump above the coccyx (Figure 62-3). A high rectourethral fistula is suspected and the surgeon takes the neonate to the operating room for colostomy formation. Three months later the child undergoes definitive imperforate anus repair and later colostomy takedown.

Introduction

Imperforate anus is a congenital anomaly in which the natural anal opening is absent. The presentation is highly variable with inconsistent findings of fistulas to skin or the urogenital tract. The term “anorectal malformations” integrates various forms of imperforate anus.

Epidemiology

• Approximately 1 newborn per 5000 live births.⁸

• Slight male preponderance.

Etiology and Pathophysiology

• Defects in the early urogenital and anorectal development, normally completed by 9 weeks gestation, account for the described abnormalities of imperforate anus.⁹

Risk Factors

• There are no known risk factors.

• Most cases are sporadic, but geographic clustering and families with cases in succeeding generations have been described.

Diagnosis

• Usually identified at first physical examination in newborn age. More subtle cases of imperforate anus with large perineal fistulas may be missed and manifest later with chronic constipation.

Clinical Features

• Usually discovered within 24 hours—At first physical exam or when the neonate develops abdominal distention and fails to pass meconium.

• May present with flat buttocks, malformed sacrum, perineal fistula opening, or no visible signs of meconium filled fistula tract.¹⁰

• Lesions are classified as low or high based on the termination of the rectum in relation to the levator muscles or more recently according to clinical relevance and fistula anatomy.

Laboratory Testing

• Urinalysis.

Imaging

• Directed to identify associated anomalies: cardiac, gastrointestinal, spinal/sacral/vertebral, or urogenital.¹¹

  • Babygram—Vertebral anomalies.

  • Sacral radiography—Sacral defects.

  • Abdominal ultrasonography—Genitourinary tract anomalies.

  • Spinal ultrasonography—Spinal malformations.

  • Echocardiogram—Cardiac defects.

  • Cross-table lateral radiograph—Elevated, prone lateral radiograph to determine level of sacral pouch if no fistula is evident on second day of life (Figure 62-3).

Management

• Assessment of type of malformation, level of rectal pouch, and identification of rectal fistula, which is present in the majority of cases.

• Naso-/orogastric tube decompression and NPO.

• Workup for associated malformations.

• Planning of surgical management according to the level of the rectal pouch: high versus low.