Colonoscopies are performed in the primary care in growing numbers, also by general practitioners. In diagnosing adenomas and cancers, colonoscopy is preferable to sigmoidoscopy. Colonoscopy should be performed as the initial investigation when looking for possible colonic causes of iron deficiency anaemia or occult blood in the faeces. Thorough investigation of these patients and endoscopic follow-up of adenoma patients is the key to an early diagnosis and treatment as well as prevention of colon cancer. Readiness for polypectomy is desirable, at least if colonoscopy is performed because of positive screening test for faecal occult blood. Sigmoidoscopy is often sufficient in the investigation of bloody or prolonged diarrhoea or fresh blood from the anus if the cause of the bleeding becomes evident in the investigation. Microscopic colitis can almost always be diagnosed from the sigma. If an adenoma is detected in sigmoidoscopy, colonoscopy must always be performed. Fiberosigmoidoscopy should replace rectoscopy with a stiff instrument whenever sigmoidoscopy is available. Sigmoidoscopy must always be complemented by proctoscopy and touch per rectum in order to detect abnormalities of the anal canal.

This dissertation, "Are Colonoscopy and Sigmoidoscopy Effective in Reducing the Mortality and Incidence of Colorectal Cancer in Colorectal Cancer Screening?" by Tsui-ying, Kwan, 關翠瑩, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: BACKGROUND: Colorectal cancer is usually asymptomatic until later stage and the 5-year survival for stage III or IV are 68% and 10 % because of delayed diagnosis. Worldwide, it is the 4th leading cause of death among cancers which accounted for 694,000 deaths in 2012. While healthy diet and lifestyle helps prevent colorectal cancer, increased surveillance through screening has been suggested to attribute to the decreasing trend of colorectal cancer incidence in the United States in the past decade. Identifying what type of colorectal cancer screening methods is more effective is of public health relevance to Hong Kong where colorectal cancer ranks the top leading cancer. OBJECTIVES: To conduct a systematically review on current literatures to examine whether endoscopy screening by flexible sigmoidoscopy or colonoscopy is more effective for reducing the mortality and incidence of colorectal cancer than no screening as many colorectal cancers arise from adenomatous polyps, which polypectomy is hypothesized to be protective. Meanwhile, different countries adopt different kinds of colorectal cancer screening modalities, but yet, there is no agreement for the types of screening. METHODS: Four databases, Medline (OVIDSP), Pubmed, CINAHL plus (EBSCOhost), Embase (OVIDSP) were used to search for published journals. Reference list of the identified articles were screened for more relevant studies. RESULTS: A total of 8 studies were included in this systematic review. There were only 2 randomized controlled trials (RCTs) on screening for colorectal cancer using flexible sigmoidoscopy in asymptomatic and average-risk people and no RCT was found for colonoscopy. Based on the studies reviewed, findings were inconsistent on whether endoscopy screening is more effective in reducing overall colorectal cancer incidence and mortality than no screening. Endoscopy screening, either sigmoidoscopy or colonoscopy was associated with lower incidence of distal colorectal cancer. CONCLUSION: Screening by flexible sigmoidoscopy or colonoscopy is not clearly associated with lower overall colorectal cancer risks based on current systematic review. Randomized controlled trials or retrospective cohorts are required to clarify the effectiveness of endoscopy screening before considering the implementation of population-wide colorectal cancer screening. DOI: 10.5353/th_b5320387 Subjects: Colonoscopy Colon (Anatomy) - Cancer Sigmoidoscopy Rectum - Cancer

Colorectal cancer is the third-ranked neoplasm in order of incidence and mortality worldwide, and it is the second cause of cancer death in industrialized countries. Risk factors that increase the likelihood of developing colorectal cancer include diet, genetic mutations, alcohol abuse, smoking, and being over 50 years of age. In Canada, over 20,000 cases of colorectal cancer are diagnosed annually, highlighting the importance of early detection, diagnosis and treatment of the disease. Colorectal cancer can be screened using fecal occult blood testing (FOBT), double contrast barium enema (DCBE), sigmoidoscopy and colonoscopy. More than 90% of colorectal cancers arise from adenomatous polyps, which are abnormal growths of tissue projecting from the lining of the colon or rectum. Colonoscopy and flexible sigmoidoscopy are two procedures that are currently used to detect and locate colon polyps and carcinomas. Computed tomographic colonography (CTC), or virtual colonoscopy, is an imaging technique of the colon involving helical computed tomography and computer software to generate high-resolution two- and three-dimensional images of the inner surface of the colon. CTC is less invasive, requires less bowel preparation, does not require sedation or analgesia, takes less time, and can be performed in patients who have had incomplete colonoscopy or are contraindicated for colonoscopy. Disadvantages of CTC include high cost, high radiation dose, and less sensitivity and specificity than colonoscopy. A previous CADTH report published in 2008 compared the clinical- and cost-effectiveness of colonoscopy to sigmoidoscopy and CTC in the context of colorectal cancer screening. This report found that CTC did not perform as well as colonoscopy in the detection of colorectal lesions, particular for smaller polyp sizes (

The first portion of this work is devoted to a consideration of the practical aspects of the proctoscopic examination and thus presents the indications for performing a proctologic evaluation, the information that may be obtained from the patient's medical history, an example of a preprinted data form for use in the recording of the physician's findings, the preparation and positioning of the patient, and the preliminary examination of the anus including the digital rectal examination. The instruments needed to perform proctoscopy are uncomplicated, and the basic tools are inexpensive. The instruments currently available do not really differ from each other except in minor details. In the text, therefore, we have only described the prototype instruments, and details about the pro posed advantages of any particular instrument can be obtained from its manufac turer. The concluding portion of the text describes how the proctoscopic and colonoscopic examinations are performed. The atlas itself is a topographical stratification of the various diseases that may involve the perianal region, the anus, and the adjacent portions of the large bowel as well as their classification according to morphologic criteria, for example, inflammatory bowel diseases and tumors. Since many pathologic findings in the rectum and sigmoid colon are comparable to those in the upper portions of the large bowel, a duplication of these proctoscopic and colonoscopic illustrations has been avoided.

Table 1 Cancer is the second most common cause of death in Americans (see www.cdc.gov). Colorectal cancer kills more Incidence and Mortality of the Five Most Common Gastrointestinal Malignancies Americans than any other malignancy except for lung cancer. The incidences and mortalities of the major gastrointestinal a a Site Incidence Mortality (GI) malignancies are shown in Table 1. Taken as a group, the five most common GI malignancies account for more cancers Colorectum 53.9 21.6 and more cancer deaths than for any other site. Pancreas 11.1 10.6 Stomach 9.1 4.9 Flexible endoscopy has given physicians unprecedented Liver/intrahepatic bile ducts 6.2 4.4 access to the GI tract. The ability to endoscopically visu- Esophagus 4.5 4.3 alize, biopsy, and apply therapy has had implications for the management of all the major GI malignancies. Accepted Data from SEER database 1992–2002 (www.seer.cancer.gov). applications of endoscopy range from detection of mal- a Per 100,000.