This is the most pronounced intussusception I have seen and it, therefore, a good case to show the components and nomenclature of intussusceptions. 

There are two main prerequisites for intussusception:

• a 'lead point'; in this case, it is a necrotic cecal mucosal mass, but it can be anything that the bowel can 'get hold of' and prolapse distally; mucosal-based tumors (primary and secondary) are by far and away most common
• the proximal portion of bowel must be mobile; this is why small bowel is so commonly involved

The components of an intussusception are (using the above case as an example):

• the inverted cecum/ascending colon is described as the ' intussusceptum'; this is the part of the bowel that is prolapsing
• the transverse colon is the 'intussuscipiens'; the potion of the bowel receiving the intussusceptum