Anal cancer isn’t typically found during routine colonoscopy screenings for colon cancer. A test called an anoscopy can better detect and diagnose anal cancer.

Anal cancer is a rare type of cancer that develops inside the anal tract. Less than 10,000 Americans are diagnosed with this type of cancer each year.

During routine colonoscopy screenings for colon cancer, doctors are looking for abnormalities or diseases in the colon and don’t usually examine the anus. Tests like anoscopies and proctoscopies are better for examining the rectum and anus and for confirming a diagnosis of anal cancer.

In this article, we take a look at what a colonoscopy can and can’t detect and the tests doctors typically use to diagnose anal cancer.

A colonoscopy is a medical procedure that doctors use to examine the inside of the colon and rectum. Sometimes, samples of tissue are also taken during this procedure.

Colonoscopies are used as routine screenings for colon cancer. Doctors use colonoscopies to examine ulcers and polyps and to look for the causes of symptoms like anal bleeding, unexplained weight loss, frequent diarrhea, or chronic stomach pain.

A colonoscopy isn’t typically able to detect anal cancer, and routine colonoscopy screening doesn’t often find anal cancer. Colonoscopies examine tissue that’s further into the rectum and colon.

Colonoscopies are sometimes used during anal cancer testing to rule out colon or rectal cancer as causes of symptoms, but they don’t confirm anal cancer.

You’ll likely have several tests to confirm a diagnosis of anal cancer. Your doctor will usually start by discussing your symptoms, your health history, and your family’s health history. After that, your doctor will order tests to find the cause of your symptoms. These might include:

  • Digital rectal exam: A doctor or nurse will examine your rectum to feel for lumps or other abnormalities during a digital rectal exam. This procedure can be done in-office.
  • Anoscopy: In an anoscopy, a short and thin lighted tube is inserted into the rectum to examine the area.
  • Proctoscopy: A proctoscopy uses a short, thin, lighted tube with a camera lens called a proctoscope. The proctoscope is inserted into the anus to view the anus and rectum and take images. Sometimes, tissue removal and a biopsy are done at the same time.
  • Endo-anal ultrasound: An ultrasound probe is inserted into the anus to create detailed images during an endo-anal ultrasound.

Symptoms of anal cancer include:

  • small lumps near the anus
  • itching or pain around the anus
  • mucus discharge from the anus
  • bleeding from the anus
  • loss of bowel control (incontinence)

It’s worth noting that other health conditions can also cause the above symptoms of anal cancer. It’s a good idea to make a medical appointment if you’re experiencing any of these symptoms, especially if you’ve been experiencing them for more than a week.

There are multiple risk factors associated with anal cancer. These include:

There are steps you can take to protect yourself from anal cancer. An HPV vaccine is a good way to prevent HPV and reduce your risk of anal cancer.

Practicing safe sex is another important way you can lower your risk. You can read more about ways to keep yourself protected in our safe sex guide. Getting regularly tested for STDs and quitting smoking can also help you lower your risk.

A colonoscopy is a test that’s used to examine the large intestine and rectum. This procedure is commonly used as routine screening for colon cancer and can also be used to look at polyps and ulcers.

Sometimes, this test is used as part of anal cancer testing to rule out other possible causes of anal cancer symptoms. But a colonoscopy can’t find anal cancer. Instead, doctors use a test called an anoscopy to examine the anal area and confirm a diagnosis of anal cancer.