Megarectum is a large rectum

Rectum

The rectum is the final straight portion of the large intestine in some mammals, and the gut in others, terminating in the anus. The human rectum is about 12 cm long...

 as a result of underlying nerve

Nerve

A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...

 supply abnormalities or muscle

Muscle

Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...

 dysfunction, which remains after disimpaction of the rectum. The Principles of Surgery textbook describes any rectum that can hold more than 1500cc of fluid as a megarectum. The term megarectum is also used for a large rectal mass on rectal examination

Rectal examination

A rectal examination or rectal exam is an internal examination of the rectum such as by a physician or other healthcare professional.-Procedure:...

, a wide rectum on an abdominal x-ray

Abdominal x-ray

An abdominal x-ray is an x-ray of the abdomen. It is sometimes abbreviated to AXR, or KUB .-Diagnostic Tool:...

, the presence of impaired rectal sensation or the finding of large maximal rectal volumes on anorectal manometry

Anorectal manometry

Anorectal manometry is a technique used to measure contractility in the anus and rectum.It may be used to assist in the diagnosis of Hirschprung disease....

. In addition, can be the bloating of the colon due to infection, also called megacolon

Megacolon

Megacolon is an abnormal dilation of the colon . The dilatation is often accompanied by a paralysis of the peristaltic movements of the bowel...

.