Intussusception overview

# Overview
An intussusception is a situation in which a part of the intestine has prolapsed into another section of intestine, similar to the way in which the parts of a collapsible telescope slide into one another. The part which prolapses into the other is called the intussusceptum, and the part which receives it is called the intussuscipiens. 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.
Intussusception in humans is almost exclusively a disease of the young, usually those between 2 months and 36 months old. This may be a result of its link with certain childhood vaccinations. The CDC through the Federal Government of the United States through the National Vaccine Injury Compensation Program provides compensation for individuals who suffer intussusception as a result of their reaction to vaccines that contain "live, oral, rhesus-based rotavirus."
Intussusception occurs more frequently in boys than in girls, with a ratio of approximately 3:1.
In adults, intussusception represents the cause of approximately 1% of bowel obstructions and is frequently associated with neoplasm, malignant or otherwise.

# Historical Perspective
Intussusception was first mentioned in 1674 by Barbette of Amsterdam. It was described in detail in 1789 by John Hunter. He called it "introssusception" and described it as a rare form of bowel obstruction in adults, in which telescoping of an intestine segment occurs into another segment of intestine. In 1871, a case of intussusception in a child was operated upon by Sir Jonathan Hutchinson.

# Classification
Intussusception may be classified into several subtypes based on location and etiology. According to location of intussusception it is classified into ileocolic, ileo-ileo-colic, jejuno-jejunal, jejuno-ileal, and colo-colic. According to etiology of intussusception it is classified into idiopathic or lead point (pathologic) types.

# Pathophysiology
The exact pathogenesis of intussusception is not fully understood. Intussusception occurs if there is an imbalance between the longitudinal and radial smooth muscle forces of intestine that maintain its normal structure. This imbalance leads to a segment of intestine to invaginate into another segment and cause entero-enteral intussusception. Etiology of intussusception is either idiopathic or pathologic (lead point). In children intussusception occurs mostly due to idiopathic causes. Idiopathic causes include seasonal viral gastroenteritis, rotavirus vaccine, adenovirus infection, hypertrophy of intestinal peyers patches, and bacterial enteritis. In adults intussusception occurs mostly due a lead point. Lead point occurs due to Henoch-Schonlein purpura, cystic fibrosis, Celiac disease, Crohn's disease, Meckel's  diverticulum etc.

# Causes
Common causes of intussusception in children can be divided into idiopathic and pathologic. Idiopathic causes include seasonal viral gastroenteritis, rotavirus vaccine, adenovirus infection, and bacterial enteritis. Pathologic causes of intussusception in children include Henoch-Schonlein purpura, cystic fibrosis, Celiac disease, Crohn's disease, Meckel's diverticulum, polyps, duplication cysts, and lymphoma. Intussusception in adults is mostly due to a pathologic lead point. Non-idiopathic intestinal causes for intussusception in adults can further be divided into benign and malignant enteric causes, and benign and malignant colonic causes.

# Differentiating Intussusception from Other Diseases
Intussusception must be differentiated from other diseases that cause abdominal pain,nausea/vomiting,and rectal bleeding.

# Epidemiology and Demographics
Intussuception is a common pediatric emergency. The incidence of intussusception is estimated to be 2000 cases in children born in USA in the first year of life. The prevalenceof intussusception does not vary with geographic and demographic distribution. Males are more commonly affected by intussusception than females. Male to female ratio is approximately 3:2. Intussusception most commonly affects children between the age of 6 months and 36 months. It can occur in adults but is mostly related to an underlying pathology (lead point).

# Risk Factors
Common risk factors for the development of intussusception include male gender, age 6 to 12 months and anatomical anomaly of the intestine. Less common risk factors in the development of intussusception include antecedent viral illness, seasonal variation, first generation Rotavirus vaccine, Meckel's diverticulum, Celiac disease, polyp, cystic fibrosis, Henoch-Schonlein purpura (HSP), surgical procedures involving the gut, duplication cyst, lymphomas, and areas of reactive lymphoid hyperplasia.

# Screening
There is insufficient evidence to recommend routine screening for intussusception.

## Natural history
If left untreated, patients with intussusception may progress to develop intestinal obstruction, perforation, and peritonitis . If intussusception is not treated then it can be fatal in 2-5 days.

## Complications
Common complications of intussusception include: Intestinal perforation, intestinal Hernia, intestinal adhesions, peritonitis, intestinal necrosis, electrolyte imbalance, and recurrence.

## Prognosis
Prognosis is generally excellent if diagnosed and treated early. After nonoperative reduction is less than 10%.Recurrence mostly occurs within 72 hours after first episode.In some cases recurrence has been reported after 36 months.More than 1 recurrence can be due to a lead point.After pneumatic enema recurrence rate is 4%.After barium enema recurrence rate is 10%.

# Diagnosis

## History and symptoms
A positive history of abdominal pain, vomiting, rectal bleeding, and lethargy is suggestive of intussusception. Presentation of intussusception is very variable. Suspicion for intussusception should be kept on a high index, especially in children aged 3 months - 5 years (Peak age of presentation). Obtaining history about different causes of symptoms like fever, exposure to toxins, and ill contacts. Common symptoms include pain, inconsolable crying, drawing up of legs,vomiting, abdominal mass, bloody stools, and current jelly stools. There can be intermittent pain free intervals in between episodes of pain.which can be confused with an episode of gastroenteritis. The classic triad of pain, sausage-shaped abdominal mass and currant jelly stool are only seen in 15% of initial patient presentation. Atypically patients might present with only abdominal pain and lethargy. Intussusception should be kept in mind in an infant presenting with lethargy or altered consciousness alone.

## Physical examination
Patients with intussusception usually appear in distress . Physical examination of patients with intussusception is usually remarkable for Dance's sign, sausage shaped palpable mass, and abdominal distension. On rectal examination the intussusceptum might be felt. Classical sign of intussusception - currant jelly stools may be present in a minority of cases at a later stage. Patient with intussusception usually appear chubby and healthy.

## Laboratory findings
There are no diagnostic lab findings associated with intussusception. If due to intussusception gangrene develops then it may lead to leukocytosis. Dehydration and electrolyte may develop due to persistent vomiting and fluid sequestration because of obstructed bowel.

## Imaging findings
X-Ray findings:
An x-ray may be helpful in the diagnosis of intussusception. Plain xray abdomen of patient are done in supine and upright position. Findings on an x-ray suggestive of/diagnostic of intussusception include absence of air in right lower quadrant and right upper quadrant, soft tissue density in right upper quadrant in 25-60% of patients, and normal in 60% of cases.
Ultrasound findings:
An x-ray may be helpful in the diagnosis of Intussusception. Findings on an x-ray suggestive of/diagnostic of Intussusception include target sign or doughnut sign and pseudokidney sign. If the ultrasonographer is experienced then sensitivity, specificity and negative predictive value can be close to 100%.
CT findings:
CT scan may be helpful in the diagnosis of intussusception. CT scan maybe used when other image modalities like x-ray and ultrasound have not given positive results but suspicion of intussusception is high. CT scan is also used to characterize the pathology(lead point) once intussusception has been diagnosed by ultrasound. CT scan has its drawbacks in children as it is time consuming and leads to substantial radiation exposure.

# Treatment

## Medical therapy
Non-operative treatment of intussusception is done in patients who are stable and have normal vital signs with no signs of intestinal perforation. It is done in a clinical setting with an experienced physician. This is done to prevent a major complication called tension pneumoperitoneum. Methods include fluoroscopic and ultrasonographic guided hydrostatic or pneumatic enema. Ultrasound is preferred as it avoids exposure to ionizing radiation and has better detection of pathological lead points. Ultrasonographic reduction uses a saline enema as pneumatic enema cannot be used in this. If reduction is successful then the intussusception disappears and wate /air bubbles are seen in the terminal ileum. Fluoroscopic guidance is used if there is a filling defect within bowel enema. Both hydrostatic and pneumatic enema can be used under this method. If reduction is successful then free flowing contrast or air into the small bowel is seen and there is relief of symptoms. Complications of non-operative reduction include perforation of bowel.It mostly occurs in the distal part of intussusception in the transverse colon. Recurrence of intussusception can occur in about 10% children after successful reduction. 50% cases occur in the first 72 hours and all episodes of recurrence should be considered as the first episode.

## Surgery
Surgery is not the first-line treatment option for patients with intussusception. Surgery is usually reserved for patients with either unstable patient, intestinal perforation, peritonitis, a mass lesion and patients in whom medical therapy was completely unstable. Technique includes intravenous fluid resuscitation, N.G. tube decompression and use of laparoscopy. Benefits of laparoscopy include:- accurate diagnosis, rapid recovery and minimal use of narcotic analgesia post-operatively.

## Prevention
There are no established measures for the primary prevention of Intussusception.