Intussusception

Intussusception occurs when a proximal part of the bowel invaginates into a distal part, leading to a mechanical obstruction and bowel ischemia. Infants aged 3–12 months are most commonly affected, usually with no identifiable underlying cause. Some patients may have an intraperitoneal anomaly or abnormality which initiates the process of intussusception (pathological lead point). Affected infants are typically of a healthy weight, and present with acute cyclical abdominal pain, knees drawn to the chest, and vomiting (initially nonbilious). Pallor, lethargy, and other symptoms of shock or altered mental status may be present. A late-onset symptom is “currant jelly” stool (stool with blood and mucus) passed from the ischemic bowel. A classic sign is a palpable right upper quadrant (RUQ) mass on abdominal examination, seen as a target or pseudokidney sign on abdominal ultrasound. Contrast enema (i.e., pneumatic insufflation or hydrostatic enema with normal saline or barium), is the best confirmatory diagnostic test. Intussusception is considered a surgical emergency, as it may lead to bowel necrosis and perforation if left untreated. Open surgery is indicated when nonoperative measures fail, a pathological lead point is suspected, or bowel perforation is present. If treated before complications arise, patients generally have an excellent prognosis.

• Sex: ♂ > ♀ (3:2)
• Age ^[1]
  • Peak incidence: 3–12-month-old infants
  • Otherwise commonly occurs in children 3 months to 5 years of age
  • Uncommon in adults

Intussusception, alongside incarcerated hernia, is one of the most common causes of bowel obstruction in children. It is the most common cause of bowel obstruction in the first two years of life.

Epidemiological data refers to the US, unless otherwise specified.

• Mostly idiopathic
  • ∼ 75% of cases have no identifiable lead point
  • More common in children 3 months to 5 years of age
• Pathological lead points
  • Defined as intraperitoneal anomalies or abnormalities that obstruct or tether the bowel and act as lead points in the process of intussusception ^[2]
    • Meckel diverticulum (most common in children)
    • Intestinal polyps or other benign tumors (most common in adults and 2^nd most common in general)
    • Enlarged Peyer patches: individuals with a history of a recent viral infection or immunization (e.g., rotavirus or adenovirus)
    • Bowel wall thickening in IgA vasculitis
    • Cystic fibrosis ^[3]
    • Hematoma, hemangioma
    • Enlarged lymph nodes, lymphomas
    • Adhesions
  • More likely the underlying cause in patients with recurrent episodes of intussusception; more common in children < 3 months or > 5 years of age

References:^[1]

• Imbalance in the bowel wall (idiopathic or via a pathological lead point) → invagination or “telescoping” of a portion of intestinal bowel (intussusceptum) into the distal adjacent bowel loop (intussuscipiens) → impaired lymphatic drainage and increasing pressure in intussusceptum bowel wall → venous impairment → mesenteric vessels congestion → ischemia of intussusceptum bowel wall → sloughing of bowel mucosa (most sensitive to bowel ischemia since it is the furthest from the arterial supply) → transmural necrosis and perforation with prolonged ischemia
• The dysfunctional passage leads to mechanical bowel obstruction → vomiting

• Ileocecal invagination; (most common; accounts for 85–90% of cases)
• Ileoileal invagination
• Ileocolic invagination
• Colosigmoidal invagination
• Appendicocecal invagination (very rare)

References:^[1]

• Child typically looks healthy.
• Acute cyclical colicky abdominal pain (sudden screaming or crying spells), often with legs drawn up, with asymptomatic intervals: Acute attacks occur approx. every 15–30 min.
• Vomiting (initially nonbilious)
• Abdominal tenderness, palpable sausage-shaped mass in the RUQ , and an “emptiness” or retraction in the RLQ (Dance sign) during palpation
• High-pitched bowel sounds on auscultation
• “Currant jelly” stool: Dark red stool (resembling currant jelly) may be noticed in passed stool or during digital rectal examination (usually a late sign).
• Lethargy , pallor, and other symptoms of shock or altered mental status may be present.

Less than 15% of patients with intussusception present with the classic triad of abdominal pain, a palpable sausage-shaped abdominal mass, and blood per rectum.

References:^[1][4][5]

Approach ^[1]

• If clinical suspicion is high : perform an enema.
• If the diagnosis is unclear at presentation or pathological lead points are suspected : perform an ultrasound or abdominal x-ray to confirm the diagnosis.

Procedures ^[1]

• Abdominal ultrasound (best initial test): often sufficient to confirm diagnosis ; ^[6]
  • Target sign; (transverse view): The invaginated portion of bowel appears as rings on a target in transverse view on ultrasound.
  • Pseudokidney sign (longitudinal view): The lead point of the invagination in the distal loop of bowel resembles a kidney. This “pseudokidney” is made up of longitudinal layers of bowel wall. ^[7]
  • Possible pendulous peristalsis
  • Can help rule out other causes of an acute abdomen
• Contrast or pneumatic enema using ultrasound or fluoroscopy (best confirmatory test)
  • Interruption of contrast or air at the site of invagination.
  • Pneumatic insufflation (air enema): air is injected into the intestines to create pressure.
• Abdominal x-ray
  • Inhomogeneous distribution of gas with absence of air at the site of invagination (usually right upper and lower quadrants) may be visible.
  • In cases of advanced-stage intussusception, other features of mechanical bowel obstruction will be detected.
• Abdominal CT: Perform if ultrasound and abdominal x-ray are inconclusive.
  • May show target sign
  • Helps to identify pathological lead points
• Laboratory tests: leukocytosis (suggests peritonitis)

The differential diagnoses listed here are not exhaustive.

• Initial steps: nasogastric decompression and fluid resuscitation
• Nonsurgical management (performed under continuous ultrasound or fluoroscopic guidance) ^[7]
  • Air enema: treatment of choice
  • Hydrostatic reduction: normal saline (or water-soluble contrast enema)
  • Observe for 24 hours post-reduction, as there is a small risk of perforation and recurrence is common during this period. ^[1]
• Surgical reduction
  • Indications ^[1]
    • When a pathological lead point is suspected
    • Failed conservative management ^[8]
    • Suspected gangrenous or perforated bowel
    • Critically ill patient (e.g., shock)
  • Open or laparoscopic method
    • Hutchinson maneuver: manual proximal bowel compression and reduction of intussusception
    • For necrotic bowel segments: resection and end-to-end anastomosis

Urgent intervention is necessary for intussusception to prevent potentially life-threatening complications.

• Small bowel obstruction
• Bowel gangrene, perforation, and peritonitis

We list the most important complications. The selection is not exhaustive.

The prognosis of intussusception depends on how quickly it is treated. Most cases may be treated successfully with conservative pneumatic insufflation or hydrostatic reduction. The absence of ischemia or necrotic bowel is associated with a good prognosis.

• Success rates for non-surgical reduction: 45–95% ^[9]
• Rate of relapse in patients with non-surgical reduction: 4.5–10% ^[10]