Capsule Endoscopy: How the "Pill Camera" Works & Why You Might Need It

If you've ever heard someone say they swallowed a "pill cam," they're talking about a capsule endoscopy. It's a tiny, high‑tech camera inside a vitamin‑sized capsule that takes thousands of pictures as it travels through your digestive tract.

"We use it when we need to evaluate the small bowel, which is hard to access with routine upper endoscopy or colonoscopy," explains Dr. Kavin A. Kanthasamy, a gastroenterologist at Houston Methodist.

Capsule endoscopy can be a less invasive alternative to traditional endoscopy, a procedure to examine the gastrointestinal (GI) tract. Instead of inserting a thin, flexible tube called an endoscope into either the mouth or rectum to collect images, the person just has to swallow a pill.

What is capsule endoscopy?

Capsule endoscopy involves a single‑use capsule that contains one or two miniature cameras, a light source, a battery and a transmitter. Your doctor will have you swallow this capsule at an office appointment.

As the capsule travels through your GI tract — your mouth, esophagus, stomach, small intestine, large intestine and anus — it snaps high-definition images at a rate of 2 to 6 frames per second. This gives your doctor a 360-degree view throughout the entire length of the bowel.

The device automatically sends the images to a small recorder you wear on a belt or shoulder strap. When the capsule has completed its journey, your body will pass the camera naturally, typically within 24 hours.

"The second we deploy the capsule, the camera starts recording and sends a live feed to a recorder the patient takes home," Dr. Kanthasamy says. "Our team uploads the recording to our software, and a GI doctor reads the entire study and updates the patient with the findings."

This procedure allows doctors to diagnose and treat conditions affecting both the large and small intestines without having to perform a procedure.

Why look at the small bowel this way?

Your small bowel, sometimes called the small intestine, sits between the stomach and colon. Its primary function is to digest food and absorb nutrients into the bloodstream. At about 20 feet long, this is the lengthiest portion of your GI tract, and finding problems via traditional endoscopy can be difficult because of the length and twists of the bowels. (Related: Q&A: What Is an Endoscopy?)

While not particularly common, GI bleeding can sometimes originate in the small bowel. A capsule endoscopy can help find sources of bleeding that other tests can miss.

Other advantages of this method include:

• No sedation or recovery time. You can usually go about normal daily activities during the recording period.
• Noninvasive and well tolerated. Most people can swallow the capsule without difficulty.

Who might benefit from capsule endoscopy?

"Capsules are extremely valuable when we need the full view of the small bowel," says Dr. Kanthasamy.

Common reasons your doctor may recommend capsule endoscopy include:

• Unexplained iron‑deficiency anemia and suspected small‑bowel bleeding
• Suspected Crohn's disease affecting the small intestine
• Celiac disease evaluation in select cases or to assess complications when other tests don't provide answers
• Possible small‑bowel tumors or abnormalities seen on prior imaging

(Related: Crohn's Disease: Symptoms, Causes & More You Should Know)

How does capsule endoscopy work?

Before your appointment, you'll be given fasting instructions — and your provider may recommend a bowel prep and only drinking clear liquids the day before, to improve visibility.

Be sure to review your medications and tell your care team about any history of swallowing difficulties or bowel blockages.

After that, the process is simple:

• Swallowing the capsule: It's about the size of a large vitamin (roughly 2.5 cm long). If swallowing is difficult, some patients can have the capsule placed during a brief upper endoscopy.
• During the study: The capsule captures images for 8–12 hours as it travels through the GI tract. Most systems stream images to your on‑body recorder and the data are uploaded for a GI specialist to interpret.
• Afterward: The capsule will pass with your stool. No need to retrieve — just flush as normal. If you don't see it pass within two weeks, let your provider know.

What happens after the test?

Your images will be reviewed by a gastroenterologist trained in capsule endoscopy interpretation. At a follow-up appointment, you'll return the recorder and discuss the results with your doctor. The imaging and your symptoms will inform next steps in your care.

"Sometimes it's reassurance and watchful waiting," says Dr. Kanthasamy. "Other times, we'll recommend a more targeted procedure or therapy based on what we see."

The capsule method is for diagnosis only. This means your provider can't perform a biopsy or treatment during the test. This differs from a traditional endoscopy, where your provider can remove polyps, stop bleeding, dilate strictures or take tissue samples during the procedure.

In addition, the movement of a capsule is passive. It relies on your body's natural rhythms to move through your GI tract. Unlike a traditional endoscopy, your provider can't position it or adjust the view in real time.

"If we find a source of bleeding, we may use more advanced endoscopy to reach that area," Dr. Kanthasamy says. "If there's a mass, surgery may be needed. If it's inflammation like Crohn's, we treat it with medication."

(Related: 7 Signs It's Time to See a Gastroenterologist)

What risks might be involved?

Capsule endoscopy is safe for most people. However, there are two considerations to keep in mind:

• Incomplete results: Because the camera's battery life is finite, a small percentage of studies may end before the capsule reaches the colon. Battery expiration accounts for 16% of incomplete exams. Your care team will use preparation and timing strategies to reduce this risk.
• Capsule retention: Rarely, a capsule can get stuck if there is an undiagnosed narrowing (stricture).

"I tell my patients that over 90% of the time, the capsule passes safely through your body into your stool," says Dr. Kanthasamy. "We have strict criteria, so we won't use the capsule if there is any history of bowel blockages."

Some people are concerned about privacy and data protection. All the data are encrypted within the recorder and stored in secure software with access limited to designated users.