The rectum is the last part of the large intestine before the anal canal, about 12-15 cm long, following the curve of the sacrum and coccyx. It begins at the rectosigmoid junction (about S3) and ends where the puborectalis sling bends the bowel back at the anorectal junction. It has no taeniae, haustra, omental appendices or mesentery, and its lower part widens into the rectal ampulla.
| Location | Posterior pelvis, from the rectosigmoid junction at S3 down along the sacrum and coccyx to the anorectal junction |
|---|---|
| Parts | |
| Nerve Supply | Pelvic splanchnic nerves, S2-S4 (parasympathetic); Inferior hypogastric plexus (sympathetic and parasympathetic) |
| Blood Supply | Superior rectal artery (from the inferior mesenteric artery); Middle rectal arteries (from the internal iliac arteries); Inferior rectal arteries (from the internal pudendal arteries); Median sacral artery |
| Venous drainage |
|
| Lymphatic drainage |
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Stores faeces until defecation is convenient and senses rectal filling, which triggers the urge to defecate.
Peritoneum covers the front and sides of its upper third, only the front of its middle third and none of its lower third. Rectal cancer is removed with its surrounding fatty mesorectum (total mesorectal excision), which lowers local recurrence. Its veins connect the portal system (superior rectal) with the systemic system (middle and inferior rectal), and rectal tumours can therefore spread to liver or lungs.
Adenocarcinoma of the rectum presenting with bleeding, tenesmus or change in bowel habit, often treated with radiotherapy and surgery.
Protrusion of the full thickness of the rectal wall through the anus, most common in older women and linked to chronic straining.
Inflammation of the rectal lining from ulcerative colitis, infection or radiotherapy, causing bleeding, urgency and tenesmus.
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