Endoscopy
Eric G. Weiss, MD, FACS, FASCRS
Department of Colorectal Surgery
Cleveland Clinic Florida
Fort Lauderdale, Florida
Introduction
Lower gastrointestinal endoscopy is an integral part of the practice of colon and rectal surgery. Although it encompasses the use of multiple instruments, including rigid proctosigmoidoscopy, flexible sigmoidoscopy and colonoscopy, this discussion will focus on colonoscopy. Since its introduction into the armamentarium of the physician about 30 years ago, colonoscopy has gained an increasing role in both the diagnosis and treatment of colon and rectal problems. With greater experience the safety of the procedure has improved with a lower frequency of perforation and bleeding. Numerous advances have also occurred so that the colonoscopes themselves have better optics, techniques for polyp removal have improved and the indications for the procedure have been clarified. Recommendations regarding the frequency of evaluation in various risk patients has been stratified by the major endscopic societies and clarification on issues such as valvular prophylaxis and anticoagulation have also been determined.
Instrumentation
The initial colonoscopes were fiberoptic in nature with images being carried back to the eye piece using bundled, optical fibers. These scopes are still manufactured but newer instruments utilizing digital technology are available and provide clearer, more lifelike color and improved magnification as compared to the fiberoptic scopes. In addition videoscopes where the eyepiece has either been removed and all images are displayed on a monitor or the eyepiece is coupled to a camera for the same purpose are available. Most centers now use videoendoscopic equipment.
A variety of biopsy forceps, graspers, baskets, snares, irrigators and snares are available to help the endoscopist tackle even the most challenging polyps. These instruments come in a variety of sizes and shapes and are available through numerous manufacturers of endoscopic equipment.
Indications for Colonoscopy
Evaluation of the lower gastrointestinal tract is indicated for diagnosis of a variety of disorders. Patients with symptomatic complaints such as unexplained diarrhea, constipation, change in bowel habits, rectal bleeding, abdominal pain and others are all indications for colonoscopy. However surveillance and screening using colonoscopy is not as clearly defined until recently. Within the past three years all the major societies dealing with endoscopy have come up with similar although not identical recommendations for colorectal cancer screening and surveillance of patients at risk for colorectal malignancies. These include ASGE, AGA, ASCRS and American Cancer Society. ASCRS has published practice parameters for screening and surveillance of colorectal cancer.(1)
Asymptotic patients have been divided into 2 categories, low risk and high risk individuals based on personal and family history. Colonoscopy is not indicated for screening purposes in an asymptomatic patient without a family history of colorectal cancer or adenomatous polyps, but rather annual digital rectal examinations and fecal occult blood testing beginning at age 40 and sigmoidoscopy beginning at age 50 and being repeated every 3-5 years. Patients with one or more first-degree relatives with either colorectal cancer or adenomatous colorectal polyps are defined as high risk. These high risk patients should have fecal occult blood testing beginning at age 35 with colonoscopy being performed at age 40 and being repeated every three to five years thereafter. Patients with familial cancer syndromes such as HNPCC are at even higher risk and colonoscopy should begin 5-10 prior to the youngest index case and repeated as described above.
Patients with specific diseases such as ulcerative colitis and Crohn's disease are at increased risk of developing colorectal cancer and should be followed more aggressively. In ulcerative colitis, extent of disease and length of disease duration are important parameters. In patients with pancolitis, surveillance colonoscopy should begin at 7-8 years of disease duration. Random biopsies should be obtained to rule out dysplasia. If on 2 consecutive annual colonoscopies no dysplasia is noted than biannual colonoscopy with biopsy should be carried out indefinitely. Patients with Crohn's disease or left-sided colitis are at slightly less risk and therefore biannual surveillance should begin at 15 years of disease duration.
Patients with a history of colorectal cancer or adenomatous polyps should have a repeat colonoscopy 1 year after the initial colonoscopy. If at the subsequent colonoscopy no further polyps are noted than colonoscopy every three years should be adequate. Other societies have slight variations on the above recommendations but are similar.
Valve Prophylaxis
It was once thought that endoscopic evaluation of the lower gastrointestinal tract increased the risk of endocarditis due to the resulting bacteremia that occurred during the procedure. In addition patients are often asked if when they go to the dentist do they take antibiotics and if they answer yes than they are given antibiotics for their endoscopic procedures. Also often patients are advised by their cardiologists or primary care doctors to receive antibiotic prophylaxis for these procedures.
ASCRS, ASGE and AHA all have recently updated their recommendations for antibiotic prophylaxis. Practice Parameters from ASCRS have been developed on this topic and are based on the AHA guidelines.(2,3) Colonoscopy and sigmoidoscopy with or without therapeutic interventions are considered low risk procedures from the standpoint of endocarditis or prosthesis infection risk. However certain cardiac conditions and prosthesis themselves are at an increased risk and therefore do require prophylaxis. Any patient with a history of endocarditis, surgically constructed systemic pulmonary shunts or conduits, prosthetic cardiac valves and recent vascular graft implants of less than 1 years duration are considered high risk and receive prophylactic antibiotics. Orthopedic prosthesis, CNS shunts, penile prosthesis, intraocular lenses, pacemakers, plastic surgical tissue augmentation material, and other valvular heart disease are considered low risk and do not require prophylaxis.
Prophylactic antibiotics should be administered as follows: 30 minutes prior to the procedure, 2grams of Ampacillin IV and Gentamycin (1.5mg/kg to a maximum of 80mg). No second oral dose is required. If the patient is allergic to Ampacillin then Vancomycin 1gram IV should be given in addition to the Gentamycin
Management of Anticoagulant Medications
The risk of gastrointestinal bleeding following lower gastrointestinal endoscopy varies with the type of procedure. On the converse patients who are taking anticoagulant medications have risks of thrombembolic events once they are taken off their anticoagulant medications. Their risk of thromboembolic event is based on the underlying condition requiring anticoagulation. These two diametrically opposed risks, bleeding and thromboembolic events must be weighed against each other in order to determine the safety, timing and length of cessation of anticoagulant therapy for lower gastrointestinal endoscopy.
Diagnostic colonoscopy and sigmoidoscopy as well as when combined with "cold" biopsy are considered low risk procedures in relation to bleeding risk. When polypectomy is performed the bleeding risk increases to 1-2.5% and if laser ablation or coagulation is performed this increases to 6% or less. The risk of thrombembolic complications is dependent on the underlying condition requiring anticoagulation. Major thromboembolic complications include death, persistent neurologic impairment (CVA), or peripheral embolic event requiring surgery. In patients with mechanical valves not receiving anticoagulation this risk is about 4 per 100 patient years, and is decreased 50% by the addition of antiplatelet therapy and by 75% by the addition of Coumadin. Mechanical valves in the mitral or mitral and aortic positions carry the greatest risk. Caged-ball or disc valves carry greater risk than bileaflet, tilting valve or bioprosthesis. Patients with atrial fibrillation and underlying cardiac or valvular disease are at the highest risk for thromboembolic complications at 5-7% annually without anticoagulation. Anticoagulation for DVT which typically is prescribed for 1-6 months does not appear to have an increased risk of thromboembolic events if stopped for short periods of time.
ASGE has recently published new guidelines for the management of anticoagulant medications in relation to endoscopic procedures.(4) Low risk procedures (colonoscopy or sigmoidoscopy with or without biopsy) require no change in anticoagulant therapy. However since prior to endoscopy, one doesn't necessarily know the findings and the subsequent therapy it may be wise to stop the anticoagulation prior to the procedure and reinstitute it immediately if no high-risk procedure is performed. High-risk procedures in which the patient is at low risk for thromboebolic complications (polypectomy or laser ablation, DVT, atrial fibrillation without underlying valve disease, bioprosthetic valves and mechanical valves in the aortic position) require discontinuation of coumadin 3-5 days prior to the procedure. Controversy exists as to whether it is necessary for one to check a preprocedure prothrombin time to assure a normal value. The timing of the reinstitution of coumadin remains unclear but typically is 5-10 days following the procedure.
High-risk procedures in high-risk conditions (polypectomy or laser ablation, atrial fibrillation with underlying valve disease, mechanical valves in the mitral position and in any patient with previous throboembolic complications) require cessation of coumadin 3-5 days prior to the procedure. The addition of heparin while the INR is subtherapeutic should be individualized. Heparin if used should be stopped 4-6 hours prior to the procedure and reinstituted 2-6 hours after the procedure.
The management of antiplatelet drugs and NSAIDs in patients without previous bleeding disorders is felt to be at no increased risk for bleeding complications and requires no change in medication for any endoscopic procedure.
Advanced Polypectomy Techniques
Polypectomy is associated with some rate of bleeding and thermal injury following electrocautery snare excision. Therefore techniques which will enhance the safety of polypectomy with decreased complication rates would be beneficial.
Submucosal saline-epinephrine injection polypectomy provides an increased safety margin when performing snare polypectomy.(5,6) Saline injection into the submucosa underneath and surrounding sessile polyps mechanically compresses blood vessels and the epinephrine causes vasoconstriction. In addition the submucosa is expanded separating the wall of the colon from the mucosa. This increased space provides a "cushion" in preventing thermal, transmural injury to the colon. Lastly some extensive flat polyps once raised up by using this injection will be endoscopically resectable when they were not without the injection technique.
The technique itself is as follows. Once a flat polyp is identified and usually polyps only greater than 1.5-2cm in diameter may require this technique, a standard sclerotherapy needle is advanced down the biopsy port of the colonoscope. A solution of .005% epinephrine and 5% saline is used for injection. .5 to 1cc is injected submucosally to raise a bleb in the submucosal plane elevating the polyp. For larger polyps the more proximal area should be injected first rather than the distal aspect so that it does not obscure the view of the proximal extent of the polyp. Snare polypectomy is than performed in the standard fashion. This technique can be used for large pedunculated polyps to prevent bleeding. Using this technique Shirai et al, performed 645 polypectomies with no bleeding or perforations. The size of the polyps in this series was a mean of 13.3mm (3-34) for pedunculated polyps (24%) and 7.6mm (3-40) for sessile polyps (76%).
Another, although less popular technique for the treatment of polyps, which reduces the risk of thermal injury to the colon, is cold snare polypectomy. Typically small 1-3mm polyps are removed with hot biopsy forceps and larger polyps removed with electrocautery snare. Particularly hot biopsy removal of small polyps can create a rather large ulcer and "burn" at the site of polypectomy. Cold snare excision of small polyps was described by Tappero et al in 1992.(7) 210 consecutive patients without prior bleeding disorders had a total of 288 small polyps (less than 5mm in size) removed via snare technique without applying cautery. No case of perforation, serious bleeding or mortality was noted. This technique may be used instead of hot biopsy technique for small polyps.
Colonoscopic Tattoo
Two clinical scenarios occur where later exact identification of a polypectomy site would be advantageous and include the removal of a sessile polyp which may harbor cancer or in the patient whom recently underwent polypectomy and subsequently found to have cancer. In both these cases the exact site of the polyp has important implications in directing the surgeon to the appropriate site for resection. Colonscopic tattooing is one means of achieving this.(8,9,10) This is especially true now that laparoscopic colectomy is being increasingly performed. The lack of tactile discrimination associated with laparoscopy requires either intraoperative endoscopy or some type of labeling such as tattooing to allow identification at the time of surgery.
Colonoscopic tattooing is performed as follows. Usually India ink diluted 1:100 with sterile saline is used. Sterile ink can be produced by purchasing it in a sterile form, autoclaving it or passing it through a .22um Millipore filter(standard TPN filter). If clogging of the filter occurs(10%) than a tandem of a .4um a .22um filter can be used. Once the ink is ready, a standard sclerotherapy needle is advanced through the scope to the site of polypectomy. The sclerotherapy needle is advanced out at an angle to the mucosa and inserted. .1-.5cc are injected at each site to allow a bleb to form. If a bleb does not form the needle is in too deep and should be pulled back. At least 3 injections, at various points circumferentially should be perfumed, as the endoscopist does not know the relationship of the polyp to the surrounding mesenteric and antimesenteric borders of the colon. This ink is a permanent marker and has been seen as long as 10.5 years after initial placement.
Colonic Anastomotic Strictures
Anastomotic strictures following surgery are common especially when stapling techniques are employed. Although strictures can occur at any anastomosis the most common type stricture occurs after colorectal anastomosis. Options in management include surgical revision with resection and anastomosis, stapled stricture excision, strictureplasty and dilation. Endoscopic balloon dilation similar to that used for esophageal strictures is currently be used selectively for colonic strictures.11 Numerous techniques are available but most the most commonly used is a transendscopic technique where the balloon is passed through the biopsy channel of the colonoscope under direct vision through the stricture. A variety of balloons ranging from 4-25mm in diameter and 2-8cm in length are available. All balloons have a maximum recommended pressure and should not exceeded. If possible, complete bowel preparations should be given. If the stricture is so narrow that colonic obstruction is present cleansing distally with tap water enemas is performed. The colonoscope is advanced to the level of the stricture and if possible through it, than it is withdrawn 2 cm distal to the stricture and the balloon advanced through the stricture to the midpoint of the balloon. The balloon is then inflated to the recommended pressure for 60 seconds and deflated and the procedure repeated 2-3 times. Fluoroscopic guidance can be invaluable in conjunction with this technique. In addition a postprocedural water soluble contrast enema should be performed in any patient suspected of a possible perforation. Using this technique success rates of as high as 80% for symptomatic relief of anastigmatic strictures have been reported.
Colonoscopic Stenting
Colonic or rectal obstruction due to underlying malignancy has traditionally required emergent surgery with the creation of a stoma given the unprepared nature of the bowel. Other techniques to avoid stoma creation in these situations have included the performance of a subtotal colectomy with ileosigmoid or ileorectal anastomosis or on-table lavage. A more recent advancement has been the use of an expandable stent similar to stents used for esophageal malignancies.(12,13) Patients with distal colonic or rectal obstruction can have a metallic, expandable stint placed under endoscopic and flouroscopic guidance through and obstructing tumor. The stent than expands, increasing the luminal diameter and allows a bowel preparation to be given so that an elective single stage operation can be performed. The technique is as follows, endoscopy is performed to the level of the obstruction and a guidewire is advanced under a combination of direct endoscopic vision and fluoro through the obstructed area. The endoscope is removed and then using fluoroscopic guidance the stent is positioned over a wire into the obstruction. Once properly aligned it is deployed and expands, relieving the obstruction and allowing bowel preparation. Using this technique Tejero et al. reported on 25 patients without distant metastasis treated with a colonic stent.(12) Successful relief of obstruction occurred in 22 of the 25 patients allowing primary resection and anastomosis. In three patients the obstruction did not resolve requiring either subtotal colectomy or colostomy formation at the time of surgery. No perforations occurred. In another 13 patients the stent was left long term for palliation of unresectable disease.
Conclusions
Numerous advances and clarifications have occurred over the past decade in the uses of lower gastrointestinal endoscopy. Knowledge of these indications and techniques allows for better patient care and gives the endoscopist a wider range of applications of the current technology. Clear guidelines now available allows for more uniformity in regards to screening and follow-up of patients.
References
1. Practice parameters for the detection of colorectal neoplasms. The Standards Task Force. The American Society of Colon and Rectal Surgeons.
2. Practice parameters for antibiotic prophylaxis to prevent infective endocarditis or infective prosthesis during colon and rectal endoscopy. The American Society of Colon and Rectal Surgeons.
3. Dajani AS, Bisno AL, Chung KJ. Prevention of bacterial endocarditis: recommendations by the American Heart Association. JAMA 1990;264:2919-22.
4. American Society for Gastrointestinal Endoscopy: Guideline on the management of anticoagulation and antiplatelet therapy for endoscopic procedures. Gastrointestinal Endoscopy 1998;48(6):672-5.
5. Shirai M, Nakamura T, Matsuura A, Ito Y and Kobayashi S. Safer colonoscopic polypectomy with local submucosal injection of hypertonic saline-epinephrine solution. Am J Gastro 1994;89(3):334-8.
6. Waye JD. New methods of polypectomy. Gastrointest Endosc Clin N Am. 1997 Jul;7(3):413-22. Review.
7. Tappero G, Gaia E, De Guili P, Martini S, et al. Cold snare excsion of small colorectal polyps. Gastointest Endosc (Comment) 1992;38(3):310-3.
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10. Hyman N, Waye J. Endoscopic four quadrant tattoo for the indentification of colonic lesions at surgery. Gastrointest Endosc 1991;37(1):56-8.
11. Endoscopic management of colonic strictures: technology and follow-up. In, Barkan JS and O'Phelan CA, eds. Advanced Therapeutic Endoscopy, 2nd Ed. Raven Press, NY 1994.
12. Tejero E, Fernandez-Lobato R, Mainar A, Montes C, et al. Initial results of a new procedure for the treatment of malignant obstruction of the left colon. Dis Colon Rectum 1997;40:432-6.
13. Mainar A, DeGregorio A, Tejero E, Tobio R, et al. Acute colorectal obstruction: treatment with self-expandable metallic stents before schedules-results of a multicenter study. Radiology 1999;210(1):65-9.