Polyp guideline: diagnosis, treatment, and surveillance for patients with nonfamilial colorectal polyps. The Practice Parameters Committee of the American College of Gastroenterology.

Preamble This guideline is intended to indicate preferable approaches to the management of patients with colorectal polyps. It does not deal with either patients with known colon cancer or familial polyposis. When only data that will not withstand objective scrutiny are available, an American College of Gastroenterology (ACG) recommendation is identified as a consensus of experts. The guideline is applicable to all physicians who address this subject without regard to specialty training or interests and is intended to indicate the preferable but not necessarily the only acceptable approach to the patient with colorectal polyps. The guideline is intended to be flexible and must be distinguished from standards of care that are inflexible and rarely violated. Given the wide range of specifics in this common health care problem, the physician must always choose the course best suited to the individual patient and the variables in existence at the moment of decision. This guideline was developed under the auspices of the American College of Gastroenterology and its Practice Parameters Committee and approved by the Board of Trustees. It has been intensely reviewed and revised by the committee, other experts in the field, physicians who will use it, and specialists in the science of decision analysis (see Methods). The ACG recommendations are therefore considered valid at the time of their publication based on available data. Methods The human subject English-language literature was searched using MEDLINE and the following MeSH terms: polyp-, adenoma-, and polypectomy-colorectal. The titles and abstracts of the articles were reviewed by the primary author. All randomized, controlled trials were read in depth, as were all large casecontrol and cohort studies. In the resulting review, evidence was evaluated along a hierarchy with randomized, controlled trials receiving the greatest weight. Abstracts presented at national meetings were used only in special circumstances in which unique data from ongoing randomized trials were presented. When scientific data were lacking, recommendations were based on expert consensus. During its preparation, the guideline was submitted for review by the Practice Committees and the Governing Boards of the American Gastroenterological Association and the American Society for Gastrointestinal Endoscopy, and by selected authorities in colorectal neoplasia including gastroenterologists, pathologists, and radiologists. All recommendations resulting from this review were carefully considered by the Committee and incorporated in the final revision. In addition, the guideline was circulated for review and comment to primary internal medicine and family practice societies and to the membership of the American College of Gastroenterology. Clinical Considerations A colorectal polyp is a circumscribed mass of tissue that projects above the surface of the bowel mucosa. Grossly, a polyp is classified as pedunculated or sessile depending on whether it contains a discrete stalk. Polyps may ulcerate and cause intestinal bleeding. Rarely, large polyps may cause symptoms of partial bowel obstruction. Most polyps, however, are asymptomatic lesions detected only by screening or diagnostic studies. This guideline addresses the management of patients known to have one or more polyps; it does not address primary screening for colorectal neoplasia. Colorectal polyps are extremely common in Western countries; they are found in more than 30% of autopsies performed in people older than 60 years [1, 2]. The main importance of polyps is their well-recognized relationship to colorectal cancer [3]. After years of debate, it is generally accepted that most colorectal cancers arise from benign, neoplastic polyps (adenomas). Although this adenoma-cancer sequence can probably never be proved directly, persuasive data exist indicating that colorectal neoplasia changes through a continuous process from normal mucosa, to benign adenoma, to carcinoma [4]. Evidence of this sequence includes the following: 1. There is a parallel prevalence of adenomas and carcinomas, with the average age of patients with adenomas being 5 to 7 years less than that of patients with carcinomas [5, 6]. 2. Cancer is often contiguous with benign adenomatous tissue, whereas small carcinomas without adenomatous tissue are rare [7, 8]. 3. The adenomas of the familial polyposis syndrome, a well-recognized premalignant state, are histologically similar to sporadic adenomas [9]. 4. As adenomas grow, they exhibit increasing cellular atypia and abnormal chromosomal patterns [5, 10]. 5. The anatomic distribution is similar for adenomas and carcinomas [11]. 6. Adenomas are found in more than one third of surgical specimens containing a colorectal cancer [12, 13]. Histologically, polyps are classified as neoplastic (adenomas) or non-neoplastic [14, 15]. Non-neoplastic polyps have no malignant potential and include hyperplastic polyps, hamartomas, lymphoid aggregates, and inflammatory polyps. Neoplastic polyps or adenomas have malignant potential and are classified according to the World Health Organization as tubular, tubulovillous, or villous adenomas, depending on the presence and volume of villous tissue [16]. Tubular adenomas are composed of straight or branched tubules of dysplastic tissue; villous adenomas contain fingerlike projections of dysplastic epithelium. Approximately 70% of polyps removed at colonoscopy are adenomas [17]. Seventy percent to 85% of these are classified as tubular (0% to 25%, villous tissue), 10% to 25% are tubulovillous (25% to 75%, villous tissue), and fewer than 5% are villous adenomas (75% to 100%, villous tissue). Some degree of dysplasia exists in all adenomas. Most authorities recommend that dysplasia be classified as mild, moderate, or severe [18]. Others prefer only two gradations, low- and high-grade dysplasia, because this classification reduces the problem of interobserver variation [19]. Severe, or high-grade, dysplasia includes the histologic changes previously called carcinoma in situ, intramucosal carcinoma, or focal carcinoma. Abandonment of these terms is recommended because of concern for misinterpretation of the clinical significance that might lead to overtreatment, and thus they will not be used in this guideline. Approximately 5% to 7% of patients with adenomas have severe dysplasia and 3% to 5% have invasive carcinoma at the time of diagnosis. Increasing dysplasia and, presumably, malignant potential correlate with increasing adenoma size, villous component, and patient age [19]. The likelihood of invasive carcinoma also increases with increasing polyp size [15]. The development of colorectal adenomas and carcinomas probably involves both environmental and genetic factors [10, 20-22]. Environmental carcinogens appear to act on a genetically susceptible mucosa causing cellular proliferation followed by oncogene activation and chromosomal deletions leading to adenoma formation, growth, increasing dysplasia, and then invasive carcinoma. Diagnosis and Treatment Colonic polyps are diagnosed by endoscopy or barium radiography. Because most polyps are asymptomatic, they are usually found incidentally. The single-contrast barium enema examination is an inaccurate method for detecting polyps in most patients. In one large screening study, single-contrast barium enemas found only 40% of neoplastic polyps detected on subsequent colonoscopy [23]. Double-contrast techniques greatly improve the accuracy of radiologic methods for detecting polyps [24]. A study comparing the accuracy of both radiographic methods in 425 patients reported a sensitivity for detecting polyps of 90% and 40% for double- and single-contrast methods, respectively [25]. Several studies indicate that the double-contrast barium enema can accurately detect most cancers and most polyps that are larger than 1 cm in diameter [26, 27]. The main limitation of barium enema is that it does not allow biopsy or polypectomy. The most common use of flexible sigmoidoscopy is for screening asymptomatic average-risk persons for colonic neoplasms. Flexible sigmoidoscopy done with the standard 60-cm instrument detects two to three times as many polyps and is more comfortable than is rigid sigmoidoscopy [28, 29]. Sensitivity and specificity are very high because few polyps within reach of the examination instrument are missed and the false-positive rate is negligible. The combination of a double-contrast barium enema and flexible sigmoidoscopy has been promoted as an acceptable alternative to colonoscopy for patients requiring a complete examination of the large bowel. When a barium enema is used for surveillance, rigid or flexible proctosigmoidoscopy should always be done to ensure an adequate examination of the rectum. Flexible sigmoidoscopy also provides a more accurate examination of the sigmoid colon, which is often a difficult area for the radiologist to examine. Double-contrast barium enema appears to be more accurate in the proximal colon than in the distal colon [30]. Although flexible sigmoidoscopy allows biopsy of lesions, it should not be used for electrosurgical polypectomy unless the entire colon is prepared to eliminate the risk for electrocautery-induced explosion [31]. Furthermore, detection of a neoplastic polyp by screening flexible sigmoidoscopy is usually an indication for colonoscopy, at which time the polyp can be resected and a search made for synchronous neoplasia. Colonoscopy is the best method for detecting polyps accurately, especially those measuring less than 1 cm in diameter, and it allows biopsy of lesions and resection of most polyps [32, 33]. A controlled, single-blinded comparison study of double-contrast barium enema and colonoscopy performed by expert examiners reported an accuracy of 94% and 67% for diagnosing polyps for colonoscopy and radiographic studies, respectively [34]. In a recent, similarly controlled investigation, tandem