Rectum: Function, Anatomy, Length, Conditions and Care
Updated: 3 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Quick Answer: What does the rectum do?
The rectum collects and holds stool until it is ready to leave the body. It stretches as stool enters, absorbs remaining water and electrolytes, secretes mucus to support passage and uses stretch-sensing nerves to signal the urge to defecate. It is the last part of the large intestine, between the sigmoid colon and anal canal. [1]
Core idea | Plain-language meaning |
Location | The last part of the large intestine, between the sigmoid colon and anal canal. |
Main job | Collect and hold stool before it is released. |
Water handling | Absorbs remaining water and electrolytes and further solidifies waste. |
Passage | Secretes mucus to help stool pass smoothly. |
Sensation | Stretch receptors signal the central nervous system when the rectal ampulla fills. |
Typical length | About 10 to 15 centimeters, or 5 to 6 inches. |
Main concern | Persistent bleeding, pain, stool changes or difficulty pooping need professional review. |
What the research says
Flexible sigmoidoscopy screening lowers rectal and distal colorectal cancer deaths. A meta-analysis of four randomized trials involving 457,871 people found that flexible sigmoidoscopy-based screening was associated with a 20% lower colorectal cancer incidence (RR 0.80, 95% CI 0.75–0.86) and a 24% lower mortality (RR 0.76, 95% CI 0.70–0.82). For distal cancers, incidence fell (RR 0.68, 95% CI 0.60–0.77) and mortality fell (RR 0.64, 95% CI 0.49–0.83), with no significant effect on proximal colon cancer (Zhang et al., Expert Rev Anticancer Ther, 2023). [2]
Fecal incontinence affects about 1 in 12 adults worldwide. A systematic review and meta-analysis of 80 population surveys covering 548,316 people found a pooled global prevalence of 8.0% (95% CI 6.8–9.2%). Prevalence was higher in people aged 60 and older (9.3%) than in younger people (4.9%), and higher in women (9.1%) than in men (7.4%) (Mack et al., Clin Gastroenterol Hepatol, 2024). [3]
Surgery can treat full-thickness rectal prolapse with a low recurrence rate. A systematic review and meta-analysis of 17 studies including 1,242 patients who had laparoscopic ventral mesh rectopexy reported a weighted mean recurrence of 2.8% (95% CI 1.4–4.3%) over a median follow-up of 23 months, with a complication rate of 12.4%. Fecal incontinence improved in 79.3% of patients and constipation in 71% (Emile et al., Surg Endosc, 2019). [4]
What is the rectum?
The rectum is at the end of the large intestine, just before it turns into the anal canal. The large intestine is a continuous tube that includes the colon, rectum and anus. [1]
The rectum makes up the last 6 inches or so of the large intestine. It is the last stop on the gastrointestinal tract before waste exits. As food waste passes from the colon into the rectum, it collects there until nerves trigger the urge to poop. [1]
How is the rectum different from the colon?
The rectum continues from the colon and has layers of muscles and tissues, with glands on the inside that secrete and absorb. The colon is much longer, and digestion is still in progress there. [1]
By the time waste reaches the rectum, it has been reduced to solid waste. The rectum holds it and absorbs remaining water until it is ready to be released. [1]
How is the rectum different from the anus?
The anal canal continues from the rectum and makes up the last few centimeters of the large intestine. The anus contains anal sphincters, important muscles that control bowel movements. [1]
The rectum functions mainly as a reservoir and sensing area. The anal canal and anus are involved in the final controlled release of stool. [1]
How does the rectum function?
The rectum's primary function is to collect and hold stool until it is time to release it. It relaxes and stretches as waste gradually arrives from the colon. [1]
While it holds waste, the rectum absorbs remaining water and electrolytes and further solidifies the stool. It secretes mucus to help stool move through smoothly. When the rectum is full, nerves trigger the urge to poop. [1]
Where is the rectum located?
The large intestine lies loosely around the edges of the abdominal cavity and surrounds the small intestine. At its lower end, the rectum curls under the abdominal organs toward the anus. [1]
The rectum is in the pelvic cavity between the abdomen and the pelvic-floor muscles. Its top connects to the sigmoid colon, and its bottom connects to the anus. [1]
How long is the rectum?
The rectum averages between 10 and 15 centimeters, or about 5 or 6 inches, long. When its muscles activate to move waste, it can contract and shorten. [1]
Like the rest of the large intestine, the rectum is about 3 inches wide, but it can stretch wider to accommodate more waste and act as a reservoir. [1]
Measurement or feature | Description |
Average length | 10 to 15 centimeters, or about 5 to 6 inches. |
Approximate width | About 3 inches, like the rest of the large intestine. |
Stretching | It can widen to accommodate more waste. |
Muscle action | It can contract and shorten when moving waste. |
Storage role | It acts as a reservoir before stool is released. |
What are the parts of the rectum?
The rectum has a slight S shape with two bends. The upper bend, called the sacral flexure, follows the curve of the spine. The lower bend, called the anorectal flexure, marks the transition from rectum to anus. [1]
These bends help control continence, or the ability to hold stool in. Horizontal folds in the inner lining, called the valves of Houston, separate the rectal segments. [1]
The rectum has three or four chambers. The final chamber, the rectal ampulla, is the last reservoir for stool before it leaves the body. When the ampulla fills, stretch receptors in the rectal wall tell the central nervous system that it is time to defecate. Increasing pressure makes it increasingly difficult to hold stool in. [1]
What are common rectal disorders?
Rectal disorders can affect the inner lining, muscles or nerves of the rectum. They can cause pain or interfere with the rectum's storage, sensing or emptying functions.
Condition | Description |
Proctitis | Inflammation of the rectum. Infections, especially STIs, may cause acute proctitis; inflammatory bowel disease may cause chronic proctitis. |
Rectal ulcers | Painful open sores that may bleed. |
Perianal abscess | A painful, pus-filled lump near the rectum, anus or perineum. |
Colorectal polyps | Growths in the rectum that are common and not always concerning; some may develop into colorectal cancer. |
Rectal prolapse | Wear and tear on supporting muscles can cause the rectum to fall out of place and telescope into the anal canal. |
Levator syndrome | Episodic rectal pain usually attributed to spasms in the levator ani muscle. |
Fecal incontinence | Problems with rectal muscles or nerves can make it difficult to hold stool, causing accidents or leakage. |
Obstructed defecation | Difficulty pooping related to physical or psychological issues, including loss of sensation or muscle coordination. |
Constipation or fecal impaction | Difficulty pooping or infrequent bowel movements can lead to hard, impacted stool plugging the rectum. |
For more on related conditions, see our guides to constipation, fecal impaction and colon polyps.
What symptoms can signal a rectal disorder?
Rectal disorder symptoms are worth discussing with a healthcare provider whenever they appear. These include rectal bleeding in underwear or the toilet, anorectal pain or pain felt in the lower abdomen or pelvis, anal itching or signs of infection, and changes in stool color, consistency or frequency.
Other symptoms include tenesmus, the feeling that you constantly need to poop; dyschezia, meaning difficult or painful pooping; and a fleshy bulge protruding through the anus, which can be associated with pelvic-organ prolapse. [1]
How is rectal health checked?
A healthcare professional chooses tests based on symptoms and the concern being evaluated. Options include physical examinations, cultures, stool testing, pressure and coordination tests, imaging and endoscopic examinations. [1]
Test | What it may examine |
Digital rectal exam | A gloved, lubricated finger is inserted into the rectum to examine the rectum and, through its wall, structures such as the prostate or cervix. It may be part of a routine physical or gynecological exam. |
Rectal culture | A swab from inside the rectum is placed in a culture to identify bacteria or viruses. |
Stool test | A stool sample may be checked for infection, bleeding or excess white blood cells. |
Anorectal manometry | Measures how well rectal muscles and nerves work together to push stool out, using a balloon catheter connected to a measuring machine. |
Defecography | X-ray or MRI imaging while a person tries to poop, to examine how organs and muscles work together. |
Barium enema | Fluoroscopic X-ray imaging of the large intestine, including the rectum, after contrast is inserted into the rectum. |
Proctoscopy | Examination of the inside of the rectum with a short, rigid, lighted scope; an instrument may be passed through it for a biopsy. |
Flexible sigmoidoscopy | A longer flexible scope examines the rectum and the sigmoid colon; bowel preparation is required. |
How can you support rectal health?
Not every rectal condition is preventable, but several general health measures may reduce the risk of certain problems.
Practice safer sex. Sexually transmitted infections that infect the anus can also infect the rectum. Screen partners for STIs and use protection when in doubt. [1]
Support regular, healthy bowel movements. A diet with more whole foods and fewer processed foods can help prevent constipation and straining, which can contribute to other problems. [1]
Follow recommended colorectal screening. Routine colonoscopy, when appropriate for you, is an important way to screen for rectal polyps and help prevent rectal cancer. [1]
Do not ignore symptoms. Persistent pain, stool changes or difficulty pooping should be discussed with a healthcare professional before they worsen.
What questions should you ask a healthcare professional about the rectum?
A symptom diary can help you describe changes in pain, stool color, consistency and frequency, and note bleeding, itching, leakage, urgency, difficulty emptying or a bulge. These details do not diagnose a condition, but they can make a clinical discussion more specific.
Question | Why it helps |
Could the symptom involve the lining, muscles or nerves? | Rectal disorders can affect each of these areas. |
Which test is appropriate? | Evaluation may involve examination, stool testing, imaging or endoscopy. |
Could constipation or impaction be contributing? | Hard stool can plug the rectum. |
Is colorectal screening due for me? | Colonoscopy is a way to screen for rectal polyps and help prevent rectal cancer. |
What symptoms should prompt follow-up? | Persistent pain, stool changes and pooping difficulty should not be ignored. |
A gastroenterologist or proctologist can help diagnose and treat rectal conditions. Not every rectal symptom is an emergency, but persistent bleeding, pain, stool changes, signs of infection, a bulge, leakage or difficult and painful bowel movements need professional review, and severe or rapidly worsening symptoms need prompt assessment. Get emergency care for heavy rectal bleeding, bleeding with dizziness or fainting, or black, tarry stools.
Conclusion: The rectum is a storage and sensing organ
The rectum is the final part of the large intestine before the anal canal. It stores stool, absorbs remaining water and electrolytes, secretes mucus and sends stretch-related signals that help coordinate the urge to defecate. [1]
Its S-shaped anatomy, folds, chambers and rectal ampulla support storage and continence. Disorders can affect the inner lining, muscles or nerves and may lead to pain, bleeding, stool changes, leakage or difficulty emptying. Safer sex, a healthy diet, appropriate colorectal screening and attention to symptoms can support rectal health, but they do not replace individualized medical care. [1]
Use this guide to prepare questions for a healthcare professional. It is an anatomy and awareness resource, not a diagnosis or a substitute for urgent care. [1]
Frequently Asked Questions
What is the rectum?
The rectum is the last part of the large intestine before it turns into the anal canal. It collects and holds stool before it leaves the body.
Where is the rectum located?
The rectum is in the pelvic cavity between the abdomen and the pelvic-floor muscles. Its top connects to the sigmoid colon and its bottom connects to the anus.
How long is the rectum?
The rectum averages 10 to 15 centimeters, or about 5 to 6 inches.
What is the main function of the rectum?
The rectum's primary function is to collect and hold stool until release. It also absorbs remaining water and electrolytes, secretes mucus and sends stretch-related nerve signals.
What is the rectal ampulla?
The rectal ampulla is the final chamber of the rectum and the last reservoir for stool before it leaves the body.
What makes you feel the urge to poop?
When the rectum fills and stretches, nerves signal the central nervous system, creating the urge to defecate. Increasing pressure makes it harder to hold stool in.
What is the difference between the rectum and the anus?
The anal canal continues from the rectum. The anus contains sphincter muscles that control bowel movements.
What is proctitis?
Proctitis is inflammation in the rectum. Infections, especially STIs, may cause acute proctitis, while inflammatory bowel disease may cause chronic proctitis.
What is rectal prolapse?
Rectal prolapse occurs when wear and tear on the muscles holding the rectum in place lets it fall out of place and telescope into the anal canal.
When should I discuss rectal bleeding with a healthcare professional?
Rectal bleeding in your underwear or the toilet should be discussed with a healthcare professional. Persistent pain, stool changes or difficult pooping also need review.
Related guides
References
Cleveland Clinic. Rectum: Function, Anatomy, Length & Location. Cleveland Clinic. Updated March 3, 2023. https://my.clevelandclinic.org/health/body/24785-rectum-function
Zhang C, Liu L, Li J, et al. Effect of flexible sigmoidoscopy-based screening on colorectal cancer incidence and mortality: an updated systematic review and meta-analysis of randomized controlled trials. Expert Rev Anticancer Ther. 2023;23(11):1217-1227. PMID 37542427. https://doi.org/10.1080/14737140.2023.2245564
Mack I, Hahn H, Gödel C, et al. Global Prevalence of Fecal Incontinence in Community-Dwelling Adults: A Systematic Review and Meta-analysis. Clin Gastroenterol Hepatol. 2024;22(4):712-731.e8. PMID 37734583. https://doi.org/10.1016/j.cgh.2023.09.004
Emile SH, Elfeki H, Shalaby M, et al. Outcome of laparoscopic ventral mesh rectopexy for full-thickness external rectal prolapse: a systematic review, meta-analysis, and meta-regression analysis of the predictors for recurrence. Surg Endosc. 2019;33(8):2444-2455. PMID 31041515. https://doi.org/10.1007/s00464-019-06803-0
Medical disclaimer
This article is for general educational purposes and is not a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified healthcare professional with any questions about a medical condition or treatment.
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