cecum
Meaning of cecum: Wide, blind-ended and full of liquid contents, it hides trouble for longer than the narrow left side of the colon does.
Definition of cecum
The cecum is the pouch that begins the large intestine, sitting in the lower right abdomen where the small intestine empties into it through the ileocecal valve. It is closed at its lower end, wider than any other part of the colon, and the appendix opens off its back wall. Contents arriving here are still liquid.
What passes through it?
Material that the small intestine has finished with arrives through the ileocecal valve, which meters the flow and discourages the dense bacterial population of the colon from moving backward into territory that has few bacteria and is not built to handle them. From the cecum the contents travel up the ascending colon, where water and salts are absorbed and bacteria begin fermenting the fiber that human enzymes cannot break down. What enters as a liquid leaves the far end of the large intestine as a solid, and most of that change happens in the stretch immediately after the cecum.
Why does the appendix matter here?
The appendix opens off the cecum a short distance below the valve, so the two share an address in the lower right abdomen. Long dismissed as functionless, it is densely packed with lymphoid tissue and is now regarded as a reservoir that can help repopulate the colon with bacteria after an illness strips it. The shared location has a practical consequence: pain in that corner of the abdomen may come from either structure, and inflammation of the cecal wall itself, seen when white cell counts collapse during chemotherapy, imitates appendicitis closely enough that the distinction is made on imaging rather than examination.
Why is disease here found late?
| Feature | Cecum and right colon | Sigmoid and left colon |
|---|---|---|
| Width of the tube | Wide | Narrow |
| Consistency of contents | Liquid | Formed and solid |
| How a growth first shows | Iron deficiency and tiredness from slow, unseen bleeding | A change in stool shape, or an obstruction |
A tumor can reach a considerable size in the cecum without blocking anything, because there is room around it and nothing solid to be held up. Blood shed there is mixed and partly digested during the long journey that follows, so it is rarely visible and shows only as falling iron stores. A growth in the sigmoid colon announces itself far sooner. Reaching the cecum is also the standard for a complete colonoscopy: the examination is only counted as complete once the operator has photographed the valve and the opening of the appendix.
Used in a sentence
Colonoscopy was extended to the cecum to complete the examination of the colon.
Good to know
The cecum sits in the lower right abdomen at the base of the appendix, which is part of why inflammation in that region can involve either or both structures and why the two can be mistaken for one another.
Word origin
Where “cecum” comes from
From Latin caecus, meaning blind, describing a pouch closed at one end; British usage keeps the older spelling caecum.