The use of viewing devices to look at organs or structures deep within the body
During endoscopy, a viewing device known as an endoscope is introduced deep into the body so that internal structures can be examined visually. Access into the body is usually through a natural opening, such as the mouth, anus, or urethra, although some endoscopes are introduced through small incisions made in the skin.
The first endoscopes were rigid, but various flexible instruments have been developed since the 1960s. Although most endoscopes now in routine use are flexible, rigid types are preferred in certain cases, including investigations in which there is a short distance from the skin to the structure being viewed, such as in an examination of the knee joint. There is also a relatively new type of endoscope, called a wireless capsule endoscope, which may occasionally be used to investigate certain gastrointestinal problems, such as bleeding of unknown cause. However, because this is a recently developed diagnostic tool, it is not widely available.
How do they work?
There are many types of endoscope, each specifically designed to investigate a particular part of the body. Flexible and rigid endoscopes differ in appearance, but they share many of the same features and operate in a similar way. For example, both forms of endoscope are tube-like instruments that use light, reflection, and magnification to show body structures clearly. Wireless capsule endoscopes essentially consist of a miniature camera, light source, and transmission circuit in a self-contained, pill-sized unit, together with an external data recorder.
The development of flexible endoscopes has been made possible by the invention of fibre-optics. Fibre-optics use thin, flexible fibres of glass or plastic (optical fibres) that transmit light along their length by internal reflections. The main part of flexible endoscope consists of a long, thin tube containing several channels that run along its length. Some channels in the endoscope carry optical fibres to provide light or transmit the image back up to the eyepiece. Other channels contain wires to control the direction of the endoscope. Channels may also be used to pump or suck air or fluid into or out of the area being examined. Other channels may be used to pass down various instruments, such as biopsy forceps or scissors.
Most flexible endoscopes have a miniature camera built into their tip, and the view recorded by the camera is displayed on a monitor. This facility allows the doctor and his or her colleagues, and sometimes the patient, to observe an investigation together and makes it possible for a record to be kept for reference.
These endoscopes are normally much shorter than flexible endoscopes and are usually inserted through an incision in the skin. Like flexible endoscopes, rigid endoscopes use a fibre-optic light source. However, other instruments, such as those used to hold tissues out of the way or to perform a surgical procedure, are passed through a separate incision rather than down the endoscope.
To allow the surfaces of the different organs or structures to be seen clearly, investigations using rigid endoscopes often involve expanding the organ or body cavity with gas or fluid to separate tissue surfaces. For example, air may be pumped into the abdomen during a laparoscopy so that the abdominal organs can be examined.
Wireless capsule endoscopes
These consist of a small capsule containing a camera, light, and transmission circuit. The capsule is swallowed by the patient and passes through the digestive tract, eventually being passed out of the body in the faeces. As the capsule endoscope moves through the digestive tract, the images captured by its camera are transmitted wirelessly to a data recorder on a belt worn by the patient. The images are later downloaded to a computer for viewing and medical assessment.
What are they used for?
Flexible endoscopes are particularly useful for looking at the digestive and respiratory tracts, which bend in places (see Flexible endoscopy). For example, nasendoscopes are very thin, short, flexible endoscopes that are used to inspect the nasal cavity and the surrounding sinuses (see Endoscopy of the nose and throat). Rigid endoscopes are used to investigate the abdominal cavity and joints (see Rigid endoscopy), where the structure to be viewed is near the skin surface.
If an abnormality is discovered during endoscopy, samples can be taken and, in some cases, treatment can be administered immediately. Instruments may be passed either down the channels of an endoscope or through small incisions in the skin in order to enable the doctor to carry out certain procedures such as taking tissue samples or removing foreign bodies. An endoscope can also be used to introduce a contrast medium into a particular site so that detailed images can then be produced on X-rays (see ERCP).
Some surgical procedures, such as removal of the gallbladder, that used to require a lengthy operation and a large incision can now be carried out more quickly and easily using instruments together with a rigid endoscope (see Endoscopic surgery).
Wireless capsule endoscopes are used only to examine the digestive tract, mainly to investigate bleeding when other diagnostic methods, such as flexible endoscopy, have failed to find the cause. Unlike rigid or flexible endoscopes, capsule endoscopes cannot be used to perform procedures such as taking tissue samples.
What are the risks?
Endoscopy is generally very safe, but, in rare cases, the endoscope may perforate an organ’s wall. For example, if the endoscope is in the stomach, it may pierce the digestive tract. Immediate surgery will then be needed to repair the damage. If a tissue sample is taken, there may be some bleeding from the site. Wireless capsule endoscopy rarely causes serious problems, although very occasionally the capsule may not pass out of the digestive tract and may need to be surgically removed.
For some endoscopic investigations, general anaesthesia or sedation may be required (see Having a general anaesthetic), and these carry risks of their own. Your doctor will therefore make sure that you are in sufficiently good health to undergo the procedure.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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