Organ
Sigmoid colon
A mobile pelvic loop before the rectum
High-yield
Volvulus is associated with a redundant sigmoid loop and a relatively narrow mesenteric attachment; this is a predisposing configuration, not the anatomy of every sigmoid colon.
Overview
Between the descending colon and rectum, the sigmoid colon forms a loop whose position depends on its length and mesentery. It usually occupies the left lower abdomen and pelvis but can extend beyond them. Its mesocolon permits movement while carrying vessels and nerves.
Reference facts
- Location
- Usually the left iliac region and pelvis; continuation into the rectum is conventionally placed near S3.
- Parts
- An intraperitoneal loop supported by a mesocolon with an approximately inverted-V attachment.
- Blood supply
- Sigmoid branches of the inferior mesenteric artery, linked through the colonic arterial arcade.
- Innervation
- Enteric circuits receive sympathetic input through mesenteric and pelvic plexuses and parasympathetic input from pelvic splanchnic nerves.
- Venous/Lymphatic drainage
- Venous return joins the inferior mesenteric vein; lymph follows sigmoid vessels toward inferior mesenteric nodes.
- Relations
- The left ureter and iliac vessels lie posterior to the mesenteric root; pelvic organs have variable relations to the mobile loop.
- Function
- Holds formed contents and contributes to their onward propulsion into the rectum.
Clinical correlation
Twisting can obstruct both bowel contents and mesenteric circulation. Marked distension may produce a coffee-bean pattern on imaging. The ureter behind the left mesocolic attachment is an important relationship during surgery.
Frequently asked questions
Where is the sigmoid colon located?
Usually the left iliac region and pelvis; continuation into the rectum is conventionally placed near S3.
What does the sigmoid colon do?
Holds formed contents and contributes to their onward propulsion into the rectum.
What are the parts of the sigmoid colon?
An intraperitoneal loop supported by a mesocolon with an approximately inverted-V attachment.
What is the blood supply of the sigmoid colon?
The sigmoid colon is supplied by the sigmoid branches of the inferior mesenteric artery, linked through the colonic arterial arcade.