The imaging of intussusception.

Intussusception is defined as the telescoping of one segment of the gastrointestinal tract into an adjacent one. It is relatively common in children and is the second most common cause of an acute abdomen in this age group. It is much less common in adults and accounts for less than 5% of cases of mechanical small bowel obstruction. Whereas the diagnosis is usually already suspected in children before imaging, it is often made unexpectedly in adults. In addition, although in children there is usually no specific underlying cause, an underlying lead point is often present in adults. Plain film radiography, barium studies and ultrasound imaging play major roles in both the diagnosis and management of this condition, and it is increasingly common for the diagnosis to be made by CT and MRI, particularly in adults. This pictorial essay reviews the imaging features that may be found in patients with bowel intussusception. As well as describing the imaging features of the more commonly used tests, we also stress the role of emerging technologies such as MRI using ultrafast half-fourier sequences with single shot turbo spin echo.