Laboratory and diagnostic testing: a perioperative update

AORN Journal,  April, 2007  by Kathleen D. Pagana

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VIRTUAL COLONOSCOPY

Many professional medical societies in the United States recommend screening asymptomatic, average-risk adults for colorectal cancer and polyps beginning at age 50. (9,10) Virtual colonoscopy is an evolving alternative to invasive conventional colonoscopy because it is noninvasive, does not require sedation, and allows a view of the colon without use of a colonoscope.

REVIEW OF CONVENTIONAL COLONOSCOPY. The conventional or optical colonoscopy is an endoscopic procedure that allows direct visualization of the rectum, colon, and small bowel with the use of a fiberoptic colonoscope. A bowel-cleaning preparation is required before the test. Conventional colonoscopy requires insertion of an IV line for administration of sedation and analgesia.

The endoscopy physician inserts a colonoscope into the patient's rectum while the patient is in the lateral decubitus position. The physician insufflates air into the patient's bowel to distend the bowel for better visualization. The physician then can perform a polypectomy, a biopsy, or other forms of endoscopic surgery as needed. (4)

After the procedure is complete, the physician carefully examines the patient's abdomen for evidence of colon perforation (eg, abdominal discomfort and tenderness). The nurse assesses the patient's vital signs for indications of hemorrhage (eg, decreased blood pressure, increased pulse rate) and notes evidence of fever and chills, which could indicate a bowel perforation. The nurse discharges the patient when the patient has recovered from the sedatives and instructs the patient not to drive and not to make any important decisions that day. (4)

Traditionally, colonoscopy has been the best procedure for viewing the entire colon. (9) Colonoscopies, however, are invasive, and approximately 85% of screening colonoscopies do not identify any significant pathology. (11) Scheduling a colonoscopy is associated with long waiting lists in some areas of the country because of the declining number of endoscopy physicians and the increasing number of Baby Boomers reaching age 50. Virtual colonoscopy is far less physician-intensive and, therefore, is easier to schedule.

REVIEW OF VIRTUAL COLONOSCOPY. Virtual colonoscopy, also known as computed tomography (CT) colonography, uses a CT scanner and computer virtual reality software to provide a view inside the colon without use of a colonoscope. This promising new screening test helps detect colorectal polyps and cancers. (9,12) Three-dimensional images of the colon simulating those obtained with conventional colonoscopy can be reconstructed from the data. (13) This noninvasive procedure is now being performed in many health care facilities. No sedation is required, and the patient does not experience discomfort (Table 3).

PREPROCEDURE PREPARATION FOR VIRTUAL COLONOSCOPY. The patient performs a cleansing bowel preparation at home before arriving at the radiology department for the virtual colonoscopy. Many different bowel-cleansing regimens have been used, and new ones are being studied in an effort to minimize the negative aspects of bowel preparation and to increase patient compliance with bowel preparation.