Can A Colonoscopy Detect Anus Cancer?


Can a colonoscopy detect anus cancer?


A colonoscopy can detect anus cancer by visualizing the anal canal and the rectum. it can also take a biopsy to confirm the diagnosis of anal cancer. However, less invasive methods such as physical examination, anoscopy, or rigid sigmoidoscopy are preferred (ref).

Doctors don’t routinely perform a colonoscopy to detect anal cancer. A physical examination (inspection or digital rectal examination) or anoscopy is usually sufficient.

However, if you are performing a screening colonoscopy for colorectal cancers; your doctor is supposed to inspect the anal canal as a part of colonoscopy to detect any anal cancers or lesions.


Is it a must to perform a colonoscopy to detect anal cancers?


Your doctor doesn’t need to request a colonoscopy if he suspects anal cancer. Detection of anal cancer by local examination or by the use of less invasive tools such as anoscope or rigid proctosigmoidoscopy.

A colonoscopy may be required for the exclusion of other colorectal masses or tumors in certain cases.

Discuss the issue with your doctor for the best option.


How colonoscopy detects anal cancers?


Anal cancer is usually a mass or ulcer that arises from the wall of the anal canal. The mass usually bleeds or causes anal pain and mass sensation (ref).

During a routine colonoscopy screening, a colonoscopy can visualize the lesion, and if it is suspicious, your doctor may take a biopsy to confirm the condition.

Not only the anus, but colonoscopy can also visualize the rectum and the entire colon.

Another alternative is a flexible sigmoidoscopy. It looks at the anal canal, rectum, and the last part of the colon (sigmoid colon).


What are other methods to detect anal cancer?


Symptoms & history:


1- Rectal bleeding:

Bleeding from the anal canal either blood when wiping or blood on the outside of the stool is the most common sign of anal cancer. Rectal bleeding occurs in about 45% of cases of anal cancer.

Unfortunately, many people can miss cancers because they think the blood is due to piles.

So, it is extremely important to get a clinical examination if it is your first time to experience blood in the stool.

2- Anal Pain:

pain is also common with anal cancer but it is not a consistent finding in all patients with anal cancers.

Studies show that anal pain occurs in about 30% of cases of anal cancer.

3- A sense of mass inside the anus.

Clinical examination by your doctor:


1- Visual inspection of the anal canal and perianal area.

2- Digital rectal examination: your doctor inserts a gloved finger into the anal canal and the rectum to detect any masses.

3- Anoscopy: Anoscopy is a firm, short, and hollow tube (about 3-4 inches). After inserting it into the anus, the doctor shines a light to visualize the wall of the anal canal.

Anoscopy is less invasive than colonoscopy. Also, It doesn’t require anesthesia or sedation.

4- Rectal Endoscopic Ultrasound: It is a special type of endoscopy with an ultrasound sensor. this is a very sensitive method for detecting small anal cancers (especially in the early stages)

5- Rigid proctosigmoidoscope: Another alternative tool for classical colonoscopy.  It is a hollow tube, usually with a tiny light at the end, it visualizes the anus, rectum, and anal canal. Also, Proctosigmoidoscope can take biopsies. Learn More.

Radiology also helps the diagnosis of anal cancers.


Radiological tests can help the diagnosis of anal cancer. common radiological tests that detect and stage anal cancers are:

  • Computed Tomography (C.T) scans of the pelvis and abdomen.
  • Magnetic resonance imaging (MRI).
  • Positron emission tomography (PET) scan.

These imaging tests, not only aid in the diagnosis of anal cancer but also help:

  • Help find how far cancer has spread.
  • Help see if the treatment is working.
  • Help look for signs of cancer coming back after treatment.

What are the risk factors for anal cancer?


Being a female


Females are more affected than men by anal cancer. according to, 5900 new cases in women and 2690 cases in men in 2020 inside the USA alone.




Human papillomavirus commonly infects the female cervix and anal canal. It is a significant cause of anal and genital warts. Also, it is involved in the development of anal and cervical cancers.

Learn more about HPV.

Multiple sexual partners.


Having sexual intercourse with multiple sex partners raises the risk of infections such as HPV and HIV. The higher the lifetime number of sexual partners, the more risk for anal cancers.


Genital warts.


Genital warts are usually a sign of HPV infection. presence of genital warts is associated with a higher risk of anal cancer (ref).


Receptive anal intercourse.


Anal intercourse increases the risk of anal fissures and HPV infection.


HIV infection.


An increased incidence of anal cancer was noted in some reports during the peak of the AIDS epidemic. For example, In New York City, there was a 10-fold increase in the incidence of anal cancer from 1979 to 1985 in adults between 20-49 years old (ref).

Cigarette smoking.


This study estimates that people with cigarette smoking are approximately 2x more likely to have anal cancers than non-smokers.