Endoscopes

by Chris Woodford. Last updated: July 28, 2020.

Think back to what medicine was like only a hundred years ago. Suppose you're a 19th-century physician and a patient knocks on your door complaining of acute pains in their abdomen. You can ask them questions and examine their body with your hands. You can prescribe them drugs and watch how they respond over days, weeks, or months. But ultimately, unless you cut their body open and examine it directly, you have no way of knowing with complete confidence what's wrong. So do you take a risk, do nothing, and wait to see how things turn out? Or do you operate immediately, potentially wasting time and money and putting your patient through disruptive and traumatic surgery? Thanks to medical imaging devices such as endoscopes, decisions like this are a thing of the past: physicians can see exactly what's going on inside your body without cutting it open. Let's take a closer look at how they work!

Photo: Endoscopes not only allow physicians to see into your body, they can also be used to carry out delicate, minor surgery. You can see the three key tubes in an endoscope at work here. The big black tube in the middle carries the image of the patient's body into the doctor's eye. The smaller black tube on the right, coming down at an angle, is where light shines into the endoscope from a lamp (not shown) in the operating room. The tube on the upper left at the top (with the silver crown) is where tiny surgical tools can be inserted. The doctor is pressing on a cable that enters the patient's body through this tube to take a tissue sample. Photo by courtesy of National Institutes of Health (NIH).

What is an endoscope?

An endoscope is a bit like a bendy telescope a physician can use for seeing inside one of the body's cavities. Unlike a telescope, which is a very rigid tube, the part of an endoscope that enters a person's body is relatively flexible. It consists of two or three main optical cables, each of which comprises up to 50,000 separate optical fibers (made from optical-quality glass or plastic). One or two of the cables carry light down into the patient's body; another one carries reflected light (the image of the patient's body) back up to the physician's eyepiece (or into a camera, which can display it on a TV monitor), as illustrated in the box below.

The optics of an endoscope are similar to those in a telescope. At the remote (distal) end, there's an objective lens, which links to one or more bendy sections of fiber-optic cable (sometimes called relays) that carry the light back out of the patient's body to a second lens in the eyepiece (or to a monitor or CCD), which can be swiveled from side to side to adjust the focus (much like the eyepieces on binoculars). Typically the lenses and cables are about 0.5cm (1/5 inch) in diameter (sometimes slightly bigger, sometimes slightly smaller).

Endoscope surgery

Artwork: An endoscope "clip" like this can be used to stop bleeding during minimally invasive surgery. Clips like this were invented in the 1970s, though they became popular in the mid-1990s with the development of better endoscope tools. Image from Clip device for endoscope and clip for endoscope for use therein by Haruhiko Masuda and Shinetsu Harada, Sumitomo Bakelite Co Ltd, courtesy of US Patent and Trademark Office.

Most modern endoscopes aren't limited to piping light in and out of a patient's body: they can also be used to carry out small surgical operations and other minor, medical procedures. Typically, the remote end of the endoscope can be moved around by turning knobs or pulling on cables, which swivel and bend it from side to side. A secondary tube attached to the main optical cables can be used for sucking out obstructing material (for example, obstacles that block the bronchial tubes in the lungs) or carrying out biopsies (removing small tissue samples for testing) with tiny forceps. Surgeons can also shine powerful, precision lasers down endoscopes to destroy diseased tissue, make accurate incisions, or heal wounds, all the time watching what they're doing through the eyepiece or on the TV monitor. This type of procedure is called minimally invasive surgery and it's simpler, quicker, less expensive, and far less traumatic than conventional operations. However, it still generally needs the patient to have an anesthetic and it's not always without drawbacks and complications.

What are the different kinds of endoscopes?

Photo: Images of stomach cancer seen through a gastroscope. Photo by courtesy of National Institutes of Health (NIH) Image Bank.

"Endoscope" is the generic name for an instrument used to look inside any part of the body in this way. Endoscopes used for specific forms of examination have the following names:

• Arthroscope: Joints
• Bronchoscope: Esophagus and lung
• Colonoscope: Colon and bowel
• Coloposcope: Vagina and cervix
• Cystoeurethroscope: Bladder and urethra
• Cytoscope: Bladder
• Duodenoscope: Small intestine
• Esophagogastroduodenoscope: Esophagus, stomach and small intestine
• Fetoscope: Womb
• Gastroscope: Stomach
• Hysteroscope: Womb
• Laparoscope: Abdomen
• Laryngoscope: Larynx
• Peritoneoscope: Peritoneum
• Proctosigmoidoscope: Lower part of the large intestine
• Sigmoidoscope: Large intestine
• Thoracoscope: Thorax
• Ureteroscope: Pelvis and ureter

Endoscopes aren't just used for medical diagnosis: they're incredibly useful for inspecting inaccessible areas of buildings or parts of machines where people can't easily see. Industrial endoscopes used in this way are called borescopes and fiberscopes.

How are fiber-optic cables different in endoscopes?

You might be wondering what's the difference between fiber-optic cables used in endoscopes and those used for carrying telephone calls, cable TV, and Internet data. Telecommunications cables are designed to carry data in digital form over very long distances; by contrast, the cables used in endoscopes carry pictures over much shorter distances and in analog form. In other words, while telecoms cables carry binary data (long strings of zeros and ones) that represent everything from MP3 music tracks to digital photos of rock stars, endoscope cables carry the actual pictures of someone's insides!

Who invented endoscopes?

Artwork: The highly flexible fiber-optic gastroscope designed by Hirschowitz et al in the 1950s. The right-hand end is inserted into the patient; the left-hand end is the bit the doctor looks into. Some of the key bits include 1) Light source (interestingly, still positioned inside the patient); 2) Prism; 3) Focusing lenses; 4) Gear-driven focusing mechanism (shown in more detail in the pullout illustration); 5) Optical fibers surrounded by protective waterproof and air-proof membrane; 6) Metal shell that transmits forces down the tube, allowing it to be manipulated along its entire length by twisting and turning; 7) Air tube allows the body cavity to be inflated; 8) Eyepiece lenses. Original artwork courtesy of US Patent and Trademark Office (with colors and new numbering added for explanatory purposes). For more details, please see US Patent 3,010,357: Flexible light-transmitting tube.

Attempts to see inside the body with crude endoscopes go back to the late 19th century; the earliest US patent I've found using the term is dated 1911. These early medical endoscopes were crude and bulky by modern standards, because they placed the light source itself inside the body cavity that needed to be examined. Typically, that meant using tiny bulbs, which produced little light and burned out quite quickly (because they had to be turned up so brightly). They also produced quite a lot of heat, which meant they risked burning or drying out the body tissue under examination. In the early 1950s, Max Fourestier and colleagues at the Centre National de la Recherche Scientifique in Paris, France developed an endoscope using rods made of quartz or Plexiglas, which enabled light from a source outside the patient's body to be shone down inside a body cavity. It was an important breakthrough—and a major stepping stone to the fiber-optic endoscope.

The basic technology behind the modern endoscope was developed in the early 1950s by English physicist Harold Hopkins (1918–1994) and his Indian-born student Narinder Kapany (1927–), who'd been asked for help by a group of surgeons. After a great deal of research, Hopkins and Kapany developed a way of making flexible pieces of glass that became known as optical fibers—thicker versions of modern fiber-optic cables that are now so widely used in telecommunications.

By the mid-1950s, three University of Michigan scientists (Basil Hirschowitz, Lawrence Curtiss, and C. Wilbur Peters) had used optical-fiber technology (which they neatly defined as "long, thin, highly flexible, rope-like tube for use in transmitting light") to build an instrument called a gastroscope that could be used to see inside a patient's stomach. The same technology was later used to study other body cavities.

Find out more

Books

• Medical Imaging by Victoria Sherrow. Marshall Cavendish, 2006. A very good school library text for teenage readers that describes the varied advances in imaging over the 20th century, including X rays, endoscopes, MRI scans, and CT scans.
• City of Light: The Story of Fiber Optics by Jeff Hecht. Oxford University Press, 2004. A more general book about how fiber optics has changed our world (mainly in telecommunications).
• A Brief History of Endoscopy by Irvin Modlin. Nexthealth, 2000. An authoritative account, but not that easy to find. Produced by Professor Modlin for the American Society for Gastrointestinal Endoscopy.

Patents

For much more technical detail, take a look at these three key patents:

• US Patent 2,699,770: Endoscope by Max Fourestier, et al, patented January 18, 1955. A pioneering endoscope that put the light source outside the body.
• US Patent 3,010,357: Flexible light-transmitting tube by Basil I. Hirschowitz, C. Wilbur Peters, and Lawrence E. Curtiss, patented November 28, 1961. The basic technology behind the modern, flexible, fiber-optic gastroscope.
• US Patent 3,016,785: Method and means for transmitting images through a bundle of transparent fibers by Narinder Kapany, patented January 16, 1962. One of Kapany's original fiber-optic patents.
• US Patent 20160184032A1: Configurable robotic surgical system with virtual rail and flexible endoscope by Enrique Romo et al, Auris Surgical Robotics Inc, patented August 22, 2017. A robot surgeon based on endoscopy techniques.

Articles

• First Surgical Robot from Secretive Startup Auris Cleared for Use by Mark Harris. IEEE Spectrum, June 7, 2016. Introducing a robot surgeon that inserts tools through natural body openings, using techniques similar to endoscopy.
• Endoscope gives close up look at Jeremy Vine's voice box: BBC News, April 17, 2013. A BBC broadcaster goes on an endoscopic voyage through his own nose and throat!
• How Do You Design a Medical Gadget That Costs 95 Percent Less Than Before? by Joseph Flaherty. Wired, July 23, 2013. How EvoTech radically redesigned the endoscope to make it cheaper and more accessible.
• Waking Up to Major Colonoscopy Bills by Roni Caryn Rabin. The New York Times, May 28, 2012. Why endoscopy can turn into a very expensive procedure.
• Dr. William Wolff, Colonoscopy Co-Developer, Dies at 94 by Douglas Martin. The New York Times, September 1, 2011. Looking back on the life of an endoscopy pioneer.
• Pentax Offering HD Endoscopes by Rob Beschizza. Wired, May 11, 2007. A brief look at a Pentax high-definition endoscope.

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