Intussusception (medical disorder)
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An intussuception as seen on CT
An intussusception is a medical condition in which a part of the intestine has invaginated into another section of intestine, similar to the way in which the parts of a collapsible telescope slide into one another. This can often result in an obstruction. The part that prolapses into the other is called the intussusceptum, and the part that receives it is called the intussuscipiens.
Signs and symptoms
Early symptoms can include nausea, vomiting (sometimes bile stained (green color)), pulling legs to the chest area, and intermittent moderate to severe cramping abdominal pain. Pain is intermittent not because the intussusception temporarily resolves, but because the intussuscepted bowel segment transiently stops contracting. Later signs include rectal bleeding, often with "red currant jelly" stool (stool mixed with blood and mucus), and lethargy. Physical examination may reveal a "sausage-shaped" mass felt upon palpation of the abdomen.
Fever is not a symptom of intussusception. However, intussusception can cause a loop of bowel to become necrotic, secondary to ischemia due to compression to arterial blood supply. This leads to perforation and sepsis, which causes fever.
Intussusception is often suspected based on history and physical exam, including observation of Dance's sign. Per rectal examination is particularly helpful in children as part of the intussusceptum may be felt by the finger. A definite diagnosis often requires confirmation by diagnostic imaging modalities. Ultrasound is today considered the imaging modality of choice for diagnosis and exclusion of intussusception due to its high accuracy and lack of radiation. A target-like mass, usually around 3 cm in diameter, confirms the diagnosis. An x-ray of the abdomen may be indicated for evaluation of intestinal obstruction or the presence of free intraperitoneal gas; the latter finding would imply that bowel perforation has already occurred. In some institutions, air enema is used for diagnosis as the same procedure can be used for treatment.
Intussusception has three main differential diagnoses. These are acute gastroenteritis, Henoch–Schönlein purpura, 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 sulcus. Henoch–Schönlein purpura presents the characteristic rash.
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.
If it cannot be reduced by an enema or if the intestine is damaged, then a surgical reduction is necessary. In a surgical reduction, the abdomen is opened and the part that has telescoped in is squeezed out (rather than pulled out) manually by the surgeon or if the surgeon is unable to successfully reduce it or the bowel is damaged, the affected section will be resected. More often, the intussusception can be reduced by laparoscopy, whereby the segments of intestine are pulled apart by forceps.
Intussusception may become a medical emergency if not treated early, as it will eventually cause death if not reduced. In developing countries where medical hospitals are not easily accessible, especially when the occurrence of intussusception is complicated with other problems, 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 2–5 days. Fast treatment is a necessity, because the longer the intestine segment is prolapsed the longer it goes without bloodflow, and the less effective a non-surgical reduction will be. Prolonged intussusception also increases the likelihood of bowel ischemia and necrosis, requiring surgical resection.
The most frequent type of intussusception is one in which the ileum enters the cecum, however other types are known to occur, such as when a part of the ileum or jejunum prolapses into itself. Almost all intussusceptions occur with the intussusceptum having been located proximally to the intussuscipiens. The reason for this is that peristaltic action of the intestine pulls the proximal segment into the distal segment. There are, however, rare reports of the opposite being true.
An anatomic lead point (that is, a piece of intestinal tissue which protrudes into the bowel lumen) is present in approximately 10% of intussusceptions.
As the trapped section of bowel may have its blood supply cut off, there is resultant ischemia (lack of oxygen in the tissues). The mucosa (gut lining) is very sensitive to ischemia, and responds by sloughing off into the gut. This creates the classically described "red currant jelly" stool, which is a mixture of sloughed mucosa, blood, and mucus. A study reported that in actuality, only a minority of children with intussusception had stools which could be described as "red currant jelly," and hence intussusception should be considered in the differential diagnosis of children passing any type of bloody stool.
Causes and risk factors
The causes of intussusception have not been clearly established and are very poorly understood. They may include infections, anatomical factors and altered motility. Although infectious agents, including rotavirus, have been suspected by some researchers to be a possible causative factor, studies and analysis have not conclusively identified them to be such. A review of sparse data on the possible association between natural rotavirus and intussusception has not demonstrated a possible association until very recently. In addition, ecological studies revealed that no seasonality exists for intussusception in the United States, whereas rotavirus has distinct wintertime peaks. In developing countries, patterns of intussusception may be quite variable and different from developed countries. A likely reason for this may be incomplete reporting of cases in developing countries. Rates of intussusception may also vary according to socioeconomic status in developing country.
There has been suspicion that it may be linked with certain childhood vaccinations due to improper use. The CDC through the Federal Government of the United States through the National Vaccine Injury Compensation Program provides compensation for individuals who suffer from injuries, if proven in court, of their reaction to vaccines that contain "live, oral, rhesus-based rotavirus."
In February of 2006, a new rotavirus vaccination, called RotaTeq (Merck) or Rotarix (GlaxoSmithKline), was introduced after extensive testing and clinical trials. More than 60,000 doses of the vaccine were given to children before the vaccine was approved by the FDA, and of these 60,000 children, the number of cases of intussusception in children receiving the vaccine was no higher than would be naturally expected. A 2007 report by the CDC states that the vaccine had fewer cases of intussusception observed than with other vaccines. 
It is diagnosed most often in infancy and early childhood, strikes about 2,000 infants (1 in every 1,900) in the United States in the first year of life. Its incidence begins to rise at about 2 to 3 months of life, peaks at 4 to 9 months of age, and then gradually declines at around 18 months.
Intussusception occurs more frequently in boys than in girls, with a ratio of approximately 3:1.
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