Consultant.
No. 10
Primary Care Procedures
A Photo Guide
Colonoscopy: A Guide to Endoscopic Screening and Therapy
By D. BRADY PREGERSON, MD—Series Editor |
September 1, 2008
Dr Pregerson is a staff emergency medicine physician at Cedars-Sinai Medical Center in Los Angeles and at Tri-City Medical Center in Oceanside, Calif. He is also a clinical instructor in medicine at the University of California, Los Angeles, School of Medicine and the designer of ERPocketBooks.com, a medical Web site designed for health care providers who work in emergency medicine and urgent care.
SHAI FRIEDLAND, MD and TONYA KALTENBACH, MD
Dr Friedland is assistant professor of medicine in the division of gastroenterology and heptatology at Stanford University School of Medicine in Stanford, Calif, and a staff physician at the Veterans Administration Palo Alto Health Care System in Palo Alto, Calif. Dr Kaltenbach is a staff physician at the Veterans Administration Palo Alto Health Care System.
REACHING THE CECUM
| |
|
Figure 2 – The puckered lips of the ileocecal valve are visible in the lower left of this photograph. The base of the cecum is seen at the center of the photo, in the distance. | Figure 3 – This image shows the appendiceal orifice as seen on entering the cecum. The orifice typically appears as a slit or a small opening visible at the base of the cecum. |
The cecum is identified as a blind end to the colon, with the appendiceal orifice visible, even in patients who have had an appendectomy (
Figure 2). The ileocecal valve entrance is visible on the proximal margin of the fold nearest the appendix (
Figure 3). It is important to advance the scope into the cecum to maximize visualization of the cecum and to definitively identify the ileocecal valve and appendiceal orifice landmarks to ensure examination of the entire colon. Obtain photographs of the cecum and ileocecal valve for documentation purposes.
WITHDRAWAL OF THE SCOPE
| |
Figure 4 – Diverticula are commonly seen even in asymptomatic patients. Two diverticula are visible near the top of this photograph. These are small and easily distinguished from the true lumen of the colon, which is visible on the lower right. | Figure 5 – The head of this pedunculated polyp is erythematous and consists of adenomatous tissue. The stalk is a tan color and contains feeding vessels that are cauterized during snare polypectomy. |
| |
Figure 6 – The scalloped mass on the left side of this image is an adenocarcinoma that penetrates at least into the deep submucosa and is appropriately treated by surgical resection. | Figure 7 – In ulcerative colitis, the surface of the colon is erythematous and friable. Here diminutive inflammatory nodules are visible in the center and at top right. |
|
Figure 8 – A retroflexed view is important for optimal visualization of the distal rectum. Here the black scope shaft is visible entering through the anus with the instrument tip maximally deflected to obtain a backward view. |
Once at the cecum, gradually withdraw the scope, carefully inspecting the colon as you do so. Usually considerable back and forth motion is required to inspect behind all of the many folds of the colon, as well as to lavage and suction fluid residue in areas that have not been adequately cleansed (a second button on the scope controls suction). A withdrawal time of at least 6 minutes is recommended to ensure an adequate examination. Common findings, such as diverticulosis, a pedunculated polyp, adenocarcinoma, and ulcerative colitis, are shown in
Figures 4 through
7.
In the rectum, it is customary to retroflex the scope (turn the tip 180 degrees so that it faces the distal rectum) (Figure 8); this area is difficult to inspect fully without retroflexion. Once the examination is finished, suction excess air from the rectum, remove the scope, and monitor the patient for 30 minutes or more while the sedative wears off. Encourage the patient to pass gas to relieve the bloating that is nearly universal after colonoscopy.
COLONOSCOPY: PITFALLS & PEARLS
•When selecting a preparation agent, keep in mind that polyethylene
glycol causes comparatively few electrolyte derangements and fluid shifts
and is thus relatively safe even in patients with renal failure or other
comorbidities. Although sodium phosphate can result in kidney injury,
fluid shifts, and electrolyte imbalances, many patients find this agent
more palatable.
•Decisions regarding discontinuation of the use of platelet inhibitors
and anticoagulants can be complex. Guidelines are available at
http://www.asge.org; however, in many cases, the decision may need
to be individualized.
•After negotiating several turns, the colonoscope may no longer move
forward smoothly. If you try to advance it further in this situation, there
is a tendency for the loops in the colon to enlarge and for the tip to remain
stationary rather than moving forward as desired. In fact, advancing the
scope in the presence of a loop can result in perforation. A variety of maneuvers
can be used to reduce the loops. These include withdrawing the
scope while applying torque to the shaft in either a clockwise or a counterclockwise
direction; repositioning the patient onto his or her back,
stomach, or right side; and having an assistant apply pressure to strategic
locations on the abdomen.
•To reach the cecum in some patients, you may need to change to a thinner
scope (pediatric scope) or occasionally a longer scope (enteroscope).
•The appendiceal orifice, visualization of which serves as a marker for
the cecum, is visible even in patients who have had an appendectomy.
•While withdrawing the scope, considerable back and forth motion is
usually required to inspect behind all of the many folds of the colon, as
well as to lavage and suction fluid residue in areas that have not been
adequately cleansed.
•Because the rectum is difficult to fully inspect with the scope in the
standard position, it is customary to retroflex the scope in the rectum.
•Many experts now favor using a snare without cautery to excise small
adenomas, less than 5 mm in diameter, which are the most common size
of adenomas encountered.
