hyperechoic central core of bowel and mesentery surrounded by the hypoechoic outer edematous bowel. In longitudinal imaging, intussusception resembles a sandwich. It is also called "pseudokidney" sign because hyperechoic tubular centre is covered by a hypoechoic rim producing a kidney-like appearance. Classification Ileoileal – 4% Ileocolic (or ileocecal) – 77% Ileo-ileo-colic – 12% Colocolic – 2% Multiple – 1% Retrograde – 0.2% Others – 2.8% In children, insussusception at the ileocecal junction and accounts for 90 percent of all cases. Differential diagnosis An intussusception has two main differential diagnoses: acute gastroenteritis and rectal prolapse. Abdominal pain, vomiting, and stool with mucus and blood are present in acute gastroenteritis, but diarrhea is the leading symptom. Rectal prolapse can be differentiated by projecting mucosa that can be felt in continuity with the perianal skin, whereas in intussusception the finger may pass indefinitely into the depth of the sulcus. Treatment The condition is not usually immediately life-threatening. The intussusception can be treated with either a barium or water-soluble contrast enema or an air-contrast enema, which both confirms the diagnosis of intussusception, and in most cases successfully reduces it. The success rate is over 80%. However, approximately 5–10% of these recur within 24 hours. Cases where it cannot be reduced by an enema or the intestine is damaged require surgical reduction. In a surgical reduction, the surgeon opens the abdomen and manually squeezes (rather than pulls) the part that has telescoped. If the surgeon cannot successfully reduce it, or the bowel is damaged, they resect the affected section. More often, the intussusception can be reduced by laparoscopy, pulling the segments of intestine apart with forceps. Prognosis Intussusception may become a medical emergency if not treated early, as it eventually causes death if not reduced. In developing countries where medical hospitals are not easily accessible, especially when other problems complicate the intussusception, death becomes almost inevitable. When intussusception or any other severe medical problem is suspected, the person must be taken to a hospital immediately. The outlook for intussusception is excellent when treated quickly, but when untreated it can lead to death within two to five days. It requires fast treatment, because the longer the intestine segment is prolapsed the longer it goes without bloodflow, and the less effective a non-surgical reduction is. Prolonged intussusception also increases the likelihood of bowel ischemia and necrosis, requiring surgical resection. Epidemiology The condition is more common in children