An endoscope is characterized by its often long, thin (sometimes flexible) lighted tube containing fiber-optical instrumentation attached to a viewing device through which one may closely observe, via the naked eye or an attached camera, the surface of a canal or hollow organ in the body.
The endoscope is often used as a form of less invasive monitoring of the body instead of, or in conjunction with, surgery. A key aspect of the device is that it is not only capable of traversing the body to allow direct observation, but may also be equipped with endoscopic accessories that allow manipulation and diagnostic/therapeutic procedures to be performed much less invasively than more conventional surgical operations.
Endoscopic surgery minimizes pain, hospital stays, and recovery time, which is good for patients. Its use is also promoted by health insurance companies and hospital administrators inclined toward reduced costs as well as to offer the best treatment options technology can provide.
The endoscope is a generalization of a broad variety of fiber-optical scopes used to elucidate diverse aspects of the body to medical practitioners for various purposes. Endoscopes come in two main categories: rigid and flexible. The rigid endoscope is designed with a rigid insertion tube and is preferred over flexible endoscopes when feasible because the rigidity allows use of optics that permit greater resolution and the absence of a visible lattice structure. However, it is more difficult to design and construct a rigid endoscope, which entails using lenses rather than fibers to transmit the image externally to the user or to a camera.
The fiber-optical endoscope can in general be viewed as a simple input/output device that utilizes an objective lens system along with a fiber relay and an ocular for magnification. The objective component is inserted directly into the body with a lighting constituent and focuses an image onto the two-dimensional surface of the array of fibers. These fibers, on the order of 10 micrometers, are bundled in groups of hundreds of thousands. Each pixel of a picture can be associated with a fiber in a one-to-one fashion of input light that is transferred from the objective end through the optical fiber relay, and magnified by the ocular to an output image on camera or seen with the naked eye. The elegant aspect is that these fibers may be twisted and flexed without damaging the image, which proves to be an integral element in many types of endoscopy. The optical layout discussed above has been simplified considerably; for spherical, chromatic, and other optical aberrations must be dealt with in order to manufacture a functional endoscope.
Not only must endoscopes be precisely organized optically, but great care must be taken to ensure their biocompatibility, since they come in close contact with extremely sensitive internal body surfaces. Accordingly, biocompatibility is of prime importance to the United States Food and Drug Administration (FDA), which considers endoscopes to be "short-term mucosal contacting, externally communicating devices and testing [for approval of use] should include, but is not limited to, mucosal irritation, sensitization, cytotoxicity, acute systemic toxicity, and short-term implantation."
Endoscopes may be used to observe and biopsy as well as to perform actual surgeries through tiny incisions in appropriate sites. The latter generally involves use of miniature video cameras and minute surgical instrumentation, often electrosurgical equipment, forceps, or biopsy attachments.
While fiberoptic technology utilizes extremely thin strands of glass or plastic to transmit light through repeated internal reflection along the optical fiber lengths for image formation and visualization, other forms of endoscopy have surfaced. Electronic endoscopes, which do not require fiber optics (yet possess a field-of-view identical to the fiber-optic endoscope as well as similar controls depressible by finger-tip, i.e. air insufflation, suction, and water injection) are also on the market. These devices boast a mounted computer chip (in reality three chips for red, blue, and green light) on the tip. They are lower-maintenance due to the lack of fiber optics, and images from them can easily be sent to a television monitor for the entire operating room to view. Even more recently (as of July 2001), technology has permitted the development of high-speed 3D endoscopic measurements.
Forms of endoscopy
The abundance of instruments falling under the designation "endoscope" includes the following, with brief descriptions of each:
- Amnioscope: Used to examine the fetus through the cervical canal prior to membrane breakage.
- Angioscope: Used to examine the interior of blood vessels. The scope must thus be very long, slender (generally on the order of 0.5 mm), and flexible to accomodate navigation of minute spaces and dynamic curvature.
- Arthroscope: Used to examine intraarticular surfaces of joints. Arthroscopes are rigid and contain stacks of optical lenses while the eyepiece is generally attached to a video camera. Due to the frequency of knee injuries, the arthroscope is most often used to diagnose and help treat knee damage.
- Bronchoscope: Aids in exploring the interior of the bronchi, their branches, and tracheal mucosa (the windpipe tissue lining).
- Choledochoscope: Used to examine the bile duct (duct carrying bile from the liver to the gallbladder or from the gallbladder to the small intestine) during an open surgical procedure intraoperatively. Both rigid and flexible scopes are employed.
- Colonoscope: Used to examine the lower section of the bowel, the large intestine, i.e. the colon.
- Culdoscope: Used to examine the pelvis and its structures. The scope is normally introduced through a small incision in the posterior vaginal cul-de-sac.
- Cystoscope: Used to examine the urinary tract and bladder; it employs similar optics to the arthroscope, yet possesses a longer depth of insertion.
- Cystourethroscope: Used to examine the urethra, bladder, and distal ureter.
- Encephaloscope: Used to examine brain cavities.
- Endoscopic retrograde cholangiopancreatography: Used in diagnosis of pancreatic disease through injection of radio-opaque dye into biliary and pancreatic ducts while examining the duodenal area.
- Enteroscope: Used to examine the esophagus, small intestine, and stomach.
- Esophagogastroduodenoscope: Used to examine the esophagus, duodenum, and stomach.
- Esophagoscope: Used to examine the channel connecting the pharynx to the stomach.
- Gastroscope: Used to examine the stomach lumen.
- Gonioscope: Used to examine and help determine the configuration of the angle between the iris and cornea.
- Hysteroscope: Used to examine the passage of the uterine cervix and cavity.
- Laparoscope: Used to examine the peritoneal cavity through the anterior abodominal wall and is commonly rigid. This scope is the most common type used by the general surgeon.
- Laryngoscope: Used to examine the larynx (the sphincter at the entrance of the trachea).
- Mediastinoscope: Used to examine the mediastinum (mass of tissues and organs separating the lungs, i.e. the heart, esophagus, trachea, etc). Often used for visualization of lymph nodes and tumors in the superior mediastinum.
- Nephroscope: Used to examine the kidneys, i.e. the renal pelvis, calyces, and upper ureter. It is employed during open procedures intraoperatively.
- Proctoscope: Used to examine the rectum.
- Resectoscope: Used to perform resections of tissue as a part of a diagnostic or therapeutic procedure.
- Rhinoscope: Used to examine the nasal cavity.
- Sigmoidoscope: Used for direct examination of the sigmoid colon.
- Thoracoscope: Used to examine the pleural cavity through an intercostal space (space between adjacent ribs, filled by intercostals muscles).
- Ureteroscope: Used to examine the ureter.
- Urethroscope: Used to examine the urethra.
Endoscopic procedures are sometimes performed under local anesthesia, especially with regard to upper gastrointestinal endoscopy. However, the majority of patients are sedated entirely. After the appropriate anesthetic has been administered, the physician inserts the endoscope in the anatomically relevant position and views the patient. The anesthesiologist, meanwhile, remains busy watching for blood pressure drops and reductions in oxygen saturation; this concern has resulted in a mandate that elderly, cardiovascularly risky, and anemic patients receive extra oxygen during the procedure.
Of paramount importance is the disinfection of used endoscopes. Endoscopic cross-infection is rare, but does occur. According to Davidson's Principles and Practice of Medicine, cross-infection has occurred in three ways:
- Transmission of pathogenic organisms from one patient to another, with salmonella the most frequent organism.
- Transmission of infection, such as hepatitis B, to staff by needle-stick injury.
- Introduction of opportunistic organisms that colonize the instruments in storage. These may cause serious infection in immunocompromised patients and can cause sever biliary or pancreatic sepsis if introduced during endoscopic retrograde cholangiopancreatography. To eliminate this possibility, many medical practices have become accustomed to disinfecting endoscopes again in the morning before the first patient arrives.
To prevent the above from occurring, health personnel must abide by strict procedures. Endoscopes should be submerged in detergent and water immediately upon removal from a patient. Valves and other removable components (including such endoscopic accessories as biopsy forceps) must be meticulously cleansed with cotton tips and a soft toothbrush, while channels must be washed. Disinfection by immersion in 2% gluteraldehyde (or 10% succine dealdehyde) for at least 20 minutes is strongly recommended since the scrubbing does not wipe out bacteria entirely. Also, medical personnel should wear gloves and masks as well as eye protection for positive hepatitis B or HIV patients. The general guideline for endoscopic disinfection is fivefold: cleaning (by mechanical scrubbing); disinfecting (by immersion in guteraldehyde or some other high-level disinfectant); rinsing (using sterile water); drying (using forced air prior to storage); and storing (without recontaminating equipment, i.e. by hanging it vertically).
Proper care of endoscopes and endoscopic instrumentation should result in:
- enhanced life span of endoscopes and accessory instruments
- reduced repair and replacement costs
- low number of microorganisms, restricting infection possibilities
As indicated above, disinfection is a chief concern in the field of endoscopy. Proper disassembly, cleansing, rinsing, drying, storage, and reassembly of the equipment, all according to the manufacturer's instructions, can help it to remain viable and safe for a long while. Corrosion is a common cause of equipment failure; stainless steel can in fact spot and stain. According to the company Gamma Endoscopy, "when endoscopic instruments do spot or stain common causes are:
- very acid or alkaline pH detergents
- improperly dissolved detergent leaving residual powder
- high mineral content of the water used for cleaning, rinsing, or in the steam autoclave
- residual disinfection solution
- disinfection solutions with an acidic pH
- residual blood, organic matter, or irrigation solution (e.g. saline), especially if instruments are not completely disassembled or thoroughly cleaned
- chemical change resulting from prolonged exposure of dissimilar metals to electrolytic solutions (e.g. normal saline, disinfection solutions)
- scratches on instruments that allow corrosive agents to get below the passivation layer, a protective layer on the instrument surface
All moving parts should be lubricated before [reassembly] to prevent 'freezing' of stopcocks and forceps jaws. It is necessary to check the instruction manual to determine which parts to lubricate, and a waterbased lubricant may be used when reassembling portions of instruments before sterilization/disinfection. Because sterilization/disinfection mediums may not penetrate tight-locking mechanisms, endoscopic instruments should not be reassembled before sterilization or disinfection."
If all other methods fail, endoscopes may be sent to instrument refurbishment companies that specialize in endoscopic repair.
Fiber optics—A technology using glass (or plastic) fibers to transmit data. A fiber optic cable is simply a bundle of these threads, each of which is capable of transmitting light wave data. Fiber optic cables can carry much more data in less space than conventional metal wires (i.e. they have greater bandwidth), are thinner and lighter, and are appropriate for transmission of digital data. It is possible to construct flexible fiber bundles that are spatially aligned for use in endoscopic procedures.
Health care team roles
Physicians perform endoscopic procedures while nurses and other medical personnel aid them. Health personnel prepare the equipment prior to examination and play a critical role in disinfecting it after the procedure has culminated. Endoscopes and accessories should be examined by health care staff for structural integrity, proper function, and cleanliness before use; during the exam; immediately following disinfection procedures; and prior to disinfection/sterilization. It is also recommended that endoscopes and accessories be thoroughly tested before initial use and used in accordance with the manufacturer's manual.
Training varies from procedure to procedure among the widely varying types of endoscopy; however, disinfection training is essentially similar, except that there are major differences in cleansing between rigid, flexible (the most difficult), and electronic endoscopes.
Dietze, B., H. Neuman, U. Mansmann, and H. Martiny. "Determination of Gluteraldehyde Residues on Flexible Endoscopes after Chemothermal Treatment in an Endoscope Washer-Disinfector." Endoscopy 33, no. 6 (2001): 529-532.
Hasegawa, K., and Y. Sato. "Endoscope system for high-speed 3D measurement." Systems and Computers in Japan 32, no. 8 (July 2001): 30-39.
The Association of Perioperative Registered Nurses (AORN). AORN, Inc., 2170 South Parker Rd., Suite 300, Denver, CO 80231-5711. (800) 755-2676 or (303) 755-6300. <http://www.aorn.org>.
Endoscope Tutorial. <http://www.leineroptics.com/endotut.htm>.
Bryan Ronain Smith