Intussusception is characterized by the telescoping of a segment of the intestine, along with its mesentery, into an adjacent intestinal lumen, causing bowel obstruction. It is one of the most common acute abdominal conditions in infants and young children. Sixty percent of cases occur in children under one year of age, though it is rare in neonates. Eighty percent of cases occur in children under two years of age, with a higher incidence in boys than girls, at a ratio of approximately (2:1) to (3:1). The condition often aligns with the seasonal prevalence of gastrointestinal viral infections, being more common in spring, and is frequently associated with gastroenteritis or upper respiratory tract infections.
Etiology and Pathogenesis
Intussusception can be classified as primary or secondary.
Primary Intussusception
This accounts for 95% of cases and predominantly occurs in infants. The structural factor predisposing infants to intussusception is the incomplete fixation and increased mobility of the ileocecal mesentery.
Secondary Intussusception
Secondary cases, which account for 5%, are more common in older children and are usually caused by an underlying organic pathology in the bowel. Examples include a Meckel’s diverticulum prolapsing into the ileum, acting as the leading point of intussusception. Other causes include intestinal polyps, bowel tumors, duplications of the intestine, or intestinal wall inflammation and thickening due to abdominal purpura.
Certain triggers, such as dietary changes, viral infections, or diarrhea, can disrupt the normal rhythm of intestinal peristalsis and initiate intussusception. Studies suggest that viral infections can lead to hyperplasia of lymphoid follicles in the terminal ileum, resulting in localized intestinal wall thickening and protrusion into the bowel lumen, which serves as the leading point for the intussusception. Enhanced intestinal peristalsis following viral infection further contributes to the occurrence of intussusception.
Pathology
Intussusception is typically antegrade, with the proximal intestinal segment telescoping into the distal lumen. Retrograde intussusception is extremely rare. There are six types based on the location of the intussusception:
Ileocecal Type
The ileocecal valve acts as the leading point, dragging the terminal ileum into the ascending colon. The cecum and appendix also invaginate into the colon. This is the most common type, accounting for approximately 50–60% of cases.
Ileo-Colic Type
The small intestine telescopes from several centimeters above the ileocecal valve into the distal ileum, then passes through the ileocecal valve into the colon. This accounts for about 30% of cases.
Ileo-Ileo-Colic Type
The ileum first invaginates into a more distal part of the ileum and subsequently telescopes into the colon. This accounts for about 10% of cases.
Small Bowel Type
This rare form involves the small intestine folding into itself.
Colonic Type
Another rare type where the colon telescopes into a more distal section of the colon.
Multiple Type
A combination of ileocolic and small-bowel intussusception occurring simultaneously.
Most cases of intussusception involving the colon or recurrent instances of intussusception cannot resolve spontaneously, with only a small fraction (transient small-bowel intussusception) being able to self-correct. Continuous spasms in the outer intussuscepted segment compromise blood flow to the inner, telescoped bowel. Initially, venous return is obstructed, leading to congestion, edema, and venous dilation in the affected bowel. Copious amounts of mucus are produced by the mucosal cells and mix with blood and stool, forming the characteristic "red currant jelly" stools. As bowel wall edema worsens, arterial supply is impaired, resulting in ischemia, necrosis, and systemic toxicity. Severe cases may lead to intestinal perforation and peritonitis.
Clinical Manifestations
Acute Intussusception
Abdominal Pain
Previously healthy, well-fed infants may suddenly exhibit severe, rhythmic, colicky abdominal pain. The infant may cry uncontrollably, pull their knees to their chest, and appear pale. The pain typically lasts 10–20 minutes and resolves temporarily, with intervals of calm or sleep lasting 5–10 minutes or longer. Recurrent colicky pain arises from traction on the mesentery and vigorous contraction of the outer intussuscepted segment.
Vomiting
Initially reflexive, the vomitus contains curdled milk or food debris. Later stages may include bile-stained vomitus or fecal-like fluid, indicating bowel obstruction.
Bloody Stool
This is a hallmark symptom. Stool may initially appear normal during the first few hours, but later becomes reduced or ceases entirely. Approximately 85% of patients pass "red currant jelly" stools (containing mucus and blood) within 6–12 hours after symptom onset. Finger examination of the rectum may also reveal bloody stools.
Abdominal Mass
In most cases, a sausage-shaped mass, tender and mobile, can be palpated in the right upper quadrant beneath the subcostal margin. The mass is smooth, mildly firm, and may shift slightly. In later stages, intestinal necrosis or peritonitis may cause abdominal distension, ascites, abdominal rigidity, tenderness, and make the mass harder to detect. Combined abdominal palpation and digital rectal examination may occasionally reveal the intussusception mass.
Systemic Condition
Early-stage patients generally appear well and have normal body temperature without systemic toxicity. As the disease progresses, intestinal necrosis or peritonitis may result in worsening systemic symptoms, including severe dehydration, fever, lethargy, coma, and shock.
Chronic Intussusception
Older children tend to exhibit a more gradual disease course. Symptoms are primarily recurrent, colicky abdominal pain. During episodes, a mass may be palpable in the upper abdomen or periumbilical region, but the abdomen appears flat, soft, and free of masses between episodes. The disease course may extend over ten days or more. Owing to the wider intestinal lumen in older children, bowel obstruction and bowel necrosis are less common. Vomiting is rare, and the passage of bloody stools occurs later in the course.
Auxiliary Examinations
Abdominal Ultrasound
Transverse scanning at the site of intussusception displays a "target sign" or "concentric ring" mass, while longitudinal scanning reveals a "sandwich sign" or "pseudo-sleeve sign.”
Ultrasound-Guided Hydrostatic Enema
A Foley catheter is inserted into the rectum, and the balloon is inflated with 20–40 ml of air. One end of a T-tube is attached to the Foley catheter, the side arm is connected to a sphygmomanometer to monitor infusion pressure, and the other end is used for fluid infusion. Warm isotonic saline (37–40°C) is gradually introduced into the bowel. Recession of the target-shaped opacity to the ileocecal region, along with the "peninsula sign" decreasing in size and eventually disappearing, indicates successful reduction. Under ultrasound, the disappearance of the "concentric ring" or "sandwich sign," restored "crab-claw" movement at the ileocecal valve, and small bowel distension showing a "honeycomb appearance" confirm both diagnosis and treatment.
Air Enema
Air is introduced via the rectum, and X-ray fluoroscopy reveals a "cup-shaped opacity," clearly visualizing the intussusception lead point. Concurrent therapeutic reduction can be performed.
Barium Enema
In chronic or difficult cases, a barium enema may show a filling defect at the intussusception site, a "cup-shaped opacity" at the leading edge of barium, and line-like or spring-like opacities between the sheath and invaginated portions.
Diagnosis and Differential Diagnosis
A diagnosis of intussusception can be made in previously healthy infants or young children who experience sudden onset of rhythmic, paroxysmal abdominal pain, crying episodes, vomiting, bloody stool, and a palpable sausage-shaped abdominal mass. Digital rectal examination should be performed early, even before the passage of bloody stool. Differential diagnosis should consider the following conditions:
Bacterial Dysentery
This condition is more common in summer. Stool is frequent, containing mucus and bloody pus, accompanied by tenesmus and often high fever with symptoms of infectious toxicity. Stool examination reveals clusters of pus cells, and bacterial cultures are positive. However, it is important to note that bacterial dysentery may occasionally lead to intussusception. Both conditions can coexist, or intussusception may develop secondary to bacterial dysentery.
Meckel's Diverticulum Hemorrhage
This condition presents as painless, large-volume bloody stool and may be complicated by intussusception.
Henoch-Schönlein Purpura
Characterized by paroxysmal abdominal pain, vomiting, and bloody stool, this condition may also present with bowel wall edema, hemorrhage, and thickening. Abdominal masses may be palpable in some cases, typically in the lower quadrants. However, most patients exhibit hallmark symptoms such as purpuric skin rashes, joint swelling and pain, and, in some cases, proteinuria or hematuria. The associated intestinal functional disturbance and bowel wall swelling may lead to secondary intussusception.
Treatment
Acute intussusception is a life-threatening emergency that requires immediate reduction upon diagnosis. For cases of recurrent intussusception with suspected organic lesions, timely identification of the underlying cause is crucial for appropriate treatment.
Non-Surgical Treatment
Indications for Enema Reduction: Intussusception occurring within 48 hours, with a stable general condition, no abdominal distension, and no significant dehydration or electrolyte imbalance.
Contraindications:
- Intussusception lasting more than 48 hours, with poor general condition, including dehydration, lethargy, high fever, or shock (especially in infants under three months of age).
- Severe abdominal distension with signs of peritoneal irritation and multiple air-fluid levels visible on X-ray.
- Intussusception reaching the splenic flexure, with a firm, high-tension mass.
- Small bowel-type intussusception.
Methods:
- Ultrasound-guided hydrostatic enema.
- Air enema.
- Barium enema reduction.
Indicators of Successful Enema Reduction:
- Expulsion of foul-smelling mucus, bloody stool, and yellowish fecal water following removal of the rectal catheter.
- The child falls asleep quickly, stops crying, and no longer vomits.
- The abdomen becomes soft, and the previously palpable mass is no longer detectable.
- Oral administration of 0.5–1 g of activated charcoal after enema reduction, followed by its passage in stool within 6–8 hours, confirms successful reduction.
Surgical Treatment
Surgery is required for intussusception lasting more than 48–72 hours, cases with severe symptoms or complications such as bowel necrosis or perforation, and small bowel-type intussusception. Depending on the child’s overall condition and the pathological changes in the affected bowel, procedures may include manual reduction, bowel resection with anastomosis, or bowel stoma formation. Recurrence of intussusception occurs in 5–8% of cases, with higher rates in those treated with enema reduction compared to surgical reduction.