Colonoscopy

David A. Margolin, MD
Department of Colon and Rectal Surgery
The Ochsner Clinic Foundation
New Orleans, LA.

INTRODUCTION

Since it acceptance in the early 1970’s colonoscopy has become the mainstay in the prevention, diagnosis and treatment of colonic pathology. Unlike other diagnostic modalities colonoscopy allows for direct visualization of the colonic mucosa with the option to provide immediate treatment. According to Medicare data over 1,000,000 diagnostic colonoscopies and over 700,000 polypectomies were performed in 2003. Even with this large numbers of procedures performed utilizing standard equipment, new technology and combinations with existing technologies, in the form of laparoscopic assisted polypectomy, have added to the endoscopist’s ability to treat colonic diseases. Despite the wide spread acceptance of colonoscopy there are still a variety of controversial issues to deal with, most notably, the management of periendoscopic anticoagulation and the use of antibiotic prophylaxis.

PERIENDOSCOPIC ANTICOAGULATION

The use of oral anticoagulation (coumadin) and antiplatelet agents (aspirin, NSAID, and plavix) have become common in the treatment and prevention of thromboembolic phenomenon related to heart valve replacement, pulmonary embolism, peripheral vascular disease, carotid artery associated strokes and cardiac arrhythmias. Unfortunately, interrupting therapy to perform diagnostic procedures may increase thromboembolic complications while continuing therapy may increase the incidence of bleeding complications during and after the procedure. In order to make a rational decision concerning treatment the relative risks of both must be weighed.

Colonoscopic procedures vary in their potential to cause significant bleeding even in patients not anticoagulated. Low risk procedures, those that have a bleeding risk less the 1%, include flexible sigmoidoscopy, colonoscopy with or without mucosal biopsies and push eneteroscopy. Procedures with a risk of bleeding complications greater then 1% include colonoscopic polypectomy, with either a hot biopsy forceps or a snare, and endoscopic pneumatic stricture dilatation.¹

Similar to procedural bleeding risks, thromboembolic complication risks also vary according to indication for anticoagulation or antiplatlet therapy. Individuals need to be concerned not only with arterial embolic complications (stroke) but recurrent venous thromboembolic complications.

Low-risk Conditions

>3 months after a deep venous thrombosis
Non-valvular atrial fibrillation (Afib) without risk factors
Biosynthetic aortic valves

High-risk Conditions

<3 months after a deep venous thrombosis
Atrial fibrillation with risk factors
Mechanical prosthetic heart valves
Two prosthetic heart valves
Prosthetic mitral valve
Severe left ventricular dysfunction
Previous cardiac embolization

Very high-risk Conditions

Within one month of a deep venous thrombosis
Within one month of an acute arterial embolic event

The most common cause of arterial thromboembolic complications is Afib. The annual stroke rate for patients with nonvalvular Afib is between 1-20%. Using a mathematical model that assumes a 4-6 day subtherapeutic period of anticoagulation the theoretical stroke risk is between 0.012-0.3% during the periendoscopic period.² This calculation is influenced by the following risk factors: previous stroke, hypertension diabetes and increasing age. In 2003 Blacker and colleagues found that these theoretical numbers understated the actual risks of arterial thromboembolic complications. ³ In their study of over 900 patients the 30 day stoke risk for patients whose anticoagulation was adjusted prior to undergoing a GI endoscopic procedure varied from 0.31% for nonvalvular Afib patients to 2.93% for patients with complex Afib (mechanical valve, age>80, hypertension, hyperlipidema). If the time window studied had been six days, similar to the mathematical model the stroke rate in individuals whose anticoagulation was adjusted still would be between 0.79% and 1.17%. Of note, there were no thromboembolic complications in patients who were continued on their anticoagulation.

In 2002 the American Society for Gastrointestinal Endoscope (ASGE) updated their published recommendations for the management of anticoagulation and antiplatlet agents.⁴ They recommend that for low risk procedures no adjustment should be made in the patients anticoagulation irrespective of their underlying medical condition. They recommend an INR should be checked and the procedure avoided when the patient is over anticoagulated. However this can cause a therapeutic dilemma especially in patients scheduled for a screening colonoscopy. If a polyp is found and the patient is fully anticoagulated do you accept the 20% risk of significant bleeding? Or do you hold the anticoagulation on all procedures and accept a small but increased risk of thromboembolic complications?

For high-risk procedures in patients with low risk conditions, warfarin should be stopped 3-5 days prior to the procedure. For high- risk procedures in high-risk patients the warfarin should be stopped 3-5 days prior to the procedure but the decision to start intravenous heparin when the INR becomes subtherapeutic should be individualized. If used, the heparin should be stopped 2-4 hrs before the procedure. For all patients the warfarin can be restarted at the patient’s normal dose the night of the procedure. For patients in the last group restarting the heparin 2-6 hrs post procedure should be considered.

A newer option available to high-risk patients requiring anticoagulation is the use of low molecular weight heparin (LMWH). Although not currently FDA approved a variety of studies have looked at outpatient use of LMWH in place of inpatient IV unfractionated heparin.^5,6 They found that LMWH to be an efficacious, cost effective method of providing outpatient anticoagulation. However, larger long-term studies are needed before this modality achieves FDA approval and widespread acceptance as bridging therapy.

The use of antipatelet agents to prevent thromboembolic complications has increased, especially with the introduction of drug-eluding stents. The newest oral agent clopidogrel (Plavix) inhibits platelet aggregation by blocking the platelet cell surface adenosine diphosphate receptor (P2T receptor). There is currently a paucity of data regarding its discontinuation prior to endoscopic procedures. However, while the ASGE has no published recommendations, it has been recommended to stop plavix for 7-10 days prior to an endoscopic procedure and restart it 7-10 days post procedure.1

Aspirin and NSAID’s both platelet cyclooxgenase inhibitors inhibit thromboxane A2 dependent platelet aggregation. Like the newer antiplatelet agents there is limited data regarding the peri-endoscopic management of these drugs and currently there is no published recommendation to discontinue their use prior to endoscopic procedures.

PERIENDOSCOPIC ANTIBIOTIC PROPHYLAXIS

Bacterial infection in susceptible patients can have catastrophic effects especially in cardiac patients. Fortunately the rate of bacterial translocation and subsequent endocarditis is extremely low in colonoscopy regardless of whether biopsies or polypectomies are performed. With this in mind the ASCRS,⁷AHA⁸ and the ASGE⁹ have recently published guidelines for the use of antibiotic prophylaxis in endoscopic procedures. Like the guidelines for anticoagulation management patients medical conditions are risk stratified.

High-risk Conditions

Prosthetic heart valves
History of endocarditis
Cyanotic congenital cardiac lesions
Systemic pulmonary shunts

Moderate-risk Conditions

Congenital cardiac anomalies
Acquired valvular dysfunction
Hypertrophic cardiomyopathy
Mitral valve prolapse with regurgitation or thickened leaflets

Low-risk Conditions

All other cardiac conditions (e.g. CABG, pacemakers, repaired ASD, repaires VSD)

Based on the above indications and balancing the risk of treatment versus the risk of subsequent infection antibiotic prophylaxis is only indicated for patients in the high-risk group.

The question as to the need for antibiotic prophylaxis for non-valvular and non-cardiac prostheses is also of significance. For orthopedic prostheses there is a paucity of literature regarding the need for prophylaxis. Both the ASCRS and ASGE currently do not recommend antibiotic prophylaxis in these patients. The issue of vascular grafts is more controversial. The AHA and the ASCRS recommend prophylaxis for the first six months after graft implantation while the ASGE does not recommend it for colonoscopy. These recommendations are based on animal models that show no evidence of bacterial colonization six months after graft implantation.

The current recommended regimen from the ASCRS is:

Ampicillin 2.0 g IV
Gentamicin 120 mg (5mg/kg) IV
Amoxicillin 1 g PO 6 hrs. post procedure

For penicillin allergic individuals

Vancomycin 1 g IV over 1-2 hrs pre procedure.

For moderate risk individuals

Ampicillin 2.0 g IV or Amoxicillin 2 g PO may be used.

It is important to remember that these are only guidelines ant do not replace clinical judgment.

LAPAROSCOPIC ASSISTED ENDOSCOPIC POLYPECTOMY

For lesions that lack clinical features suggestive of the need for a colectomy (e.g., ulceration, fixation, or hardness) laparoscopic assisted endoscopic polypectomy has been proposed as a viable alternative to colectomy. These lesions should not be amenable to endoscopic polypectomy and biopsy of the lesion should demonstrate benign histology.¹⁰

In order to organize the operating room prior to the procedure it is critical accurate preoperative lesion localization be accomplished. Endoscopic tattooing is our preferred method of preoperative lesion localization. The technique involves a submucosal injection of 0.1 ml of sterilized India ink or 0.5 to 0.75 ml of the commercially available "Spot" (carbon black, GI Supply, Camp Hill, PA) in 3 to 4 locations adjacent to the polyp. ^11,12 The injection is placed using a 25-gauge sclerotherapy needle with a needle length of 4 mm or less passed through the working channel of a colonoscope. The tip of the needle is inserted 30-45⁰ tangentially into the submucosa space of the colon. Placing tattoos on different locations circumferential locations on the colon prevents the mesentery or retroperitoneal attachments from obscuring the tattoo. Tattoos allow for adequate laparoscopic lesion visualization for 8-12 weeks (Figure 1).

The patient is placed in a modified Lloyd-Davies position (less than 15⁰ flexion of the hips) and firmly secured to an electric operating room table. Utilizing an open technique, pneumoperitoneum is established and a 10 mm camera is inserted. Under direct vision two additional 5 or 10 mm trocars are placed in the abdomen opposite the side of the lesion. Through one of these ports an atraumatic bowel clamp is placed and the colon is occluded proximal to the lesion or at the ileocecal valve. This prevents excess small bowel distention that could limit visibility. The operating room table is tilted to the side opposite the lesion and in Trendelenberg to expose the portion of the bowel that contains the lesion.

A colonoscope is passed via the anus until the colonic lesion is located. If adhesions prevent insertion of the colonoscope, the adhesions may be lysed laparosocpically. Once the lesion is identified, it is grasped endoscopically with biopsy forceps or an electrocautery snare. Retracting this instrument allows the exact location of the lesion to be identified with the laparoscopic camera. If the snare dimples the colon a saline solution-assisted polypectomy may be performed. ¹³ This involves injection of 2 to 5 ml of saline solution or an epinephrine containing solution (1:100,000) into the submucosal plane with a sclerotherapy needle passed through the biopsy port of the colonoscope. This fluid distends the submucosal layer and elevates the polyp from the surrounding tissue. This cushion increases the distance between the mucosa and the serosal surface of the bowel and reduces the chances of a full-thickness perforation. After injection of the distention solution, the area of injection is inspected with the laparoscope as the snare is retightened. If the area is no longer dimpled, the snare polypectomy proceeds under laparoscopic vision. If dimpling remains after saline injection most surgeons will remove the endoscope and perform a laparoscopic resection. If the laparoscopic assisted technique is successful, the bowel is never opened, and the patient is spared the morbidity associated with a major resection.

Several series of laparoscopic management of colonic polyps have been published. Prohm and colleagues described 6 patients who underwent laparoscopic assisted endoscopic polypectomy ¹⁴ and Franklin and colleges reported on 47 patients who underwent laparoscopic assisted endoscopic polypectomy. ¹⁵ To assure that these were truly benign polyps all underwent immediate frozen section evaluation. Since these patients had been prepped and were undergoing laparoscopic visualization of the polypectomy, resectional therapy could easily be performed if a malignancy was encountered. There were no operative or post-operative complications, conversions to open surgery or endoscopic perforations in both series. It is important that individuals recognize that this procedure should be done for non-cancerous lesions. However an oncologically adequate resection should always be done in case the final pathology is an invasive cancer. These techniques have the potential to decrease patient discomfort, length of stay and still provide adequate oncologic treatment of this problem.

REFERENCES

1. Hittelet A, Deviere J. Management of anticoagulation before and after endoscopy. Can J Gastroenterol 2003;17:329-332.
2. Kearon C, Hirsh J. Current concepts: management of anticoagulation before and after elective surgery. N Engl J Med 1997;336:1506-1511.
3. Blacker DJ, Wijdicks EFM, McClelland RL. Stroke risk in anticoagulated patients with atrial fibrillation undergoing endoscopy. Neurology 2003;61:964-968.
4. Guideline on the management of anticoagulation and antiplatelet therapy for endoscopic procedures. Gastrointestinal Endoscopy 2002;55:775-779.
5. Goldstein JL, Larson LR, Yamashita BD, et al. Low molecular weight heparin versus unfractionated heparin in the colonoscopy peri-procedure period: a cost modeling study. Am J Gasrtoenterol 2001;96:2360-2366.
6. Tinmouth AH, Morrow BH, Cruickshank MK, et al. Dalteparin as periprocedure anticoagulation for patients on warfarin and at high risk of thrombosis. Ann Pharmacother 2001;35:669-674.
7. Standards Task Force, The American Society of Colon and Rectal Surgeons. Practice parameters for antibiotic prophylaxis to prevent infective endocarditis or infected prosthesis during colon and rectal endoscopy. Dis Colon Rectum 2000;43:1193-1200.
8. Bonow RO, Carabello B, de Leon AC, et al. ACC/AHA Guidelines for the Management of Patients With Valvular Heart Disease. Executive Summary. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on Management of Patients With Valvular Heart Disease). J Heart Valve Dis. 1998 Nov;7(6):672-707.
9. Guidelines for antibiotic prophylaxis for GI endoscopy. Gastrointestinal Endoscopy 2003;58:475-482.
10. Beck DE, Margolin DA. Laparoscopic treatment of colonic polyps. Seminars in laparoscopic surgery 2004;11:23-26.
11. Shatz BA, Weinstock LB, Swanson PE, et al. Long-term safety of India ink tattoos in the colon. Gastrointest Endosc 1997; 45:153-6.
12. Askin MP, Wayne JD, Fiedler L, Harpaz N. Tattoo of colonic neoplasms in 113 patients with a new sterile carbon compound. Gastrointest Endo 2002;56:33-42.
13. Waye JD. Saline injection colonoscopic polypectomy. Am J Gastroenterol -1994;89:305-6.
14. Prohm P, Weber J, Bonner C. Laparoscopic-assisted Colonoscopic Polypectomy. Dis Colon Rectum 2001;44:746-8.
15. Franklin ME Jr, Diaz-E JA, Abrego D, Parra-Davila E, Glass JL. Laparoscopic-assisted Colonoscopic Polypectomy: the Texas Endosurgery Institute experience. Dis Colon Rectum 2000;43:1246-9.

. Gastrointestinal Endoscopy 2002;55:775-779.