Colonoscopy and MR Colonography: A Comparative Study

Karthikeyan, R (2010) Colonoscopy and MR Colonography: A Comparative Study. Masters thesis, Madras Medical College, Chennai.


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INTRODUCTION: Colorectal cancer (CRC) is the fourth most common cancer in men and the third most common in women, with mortality paralleling incidence, in the mid-1970s, approximately 60 cases of colorectal cancer were diagnosed per 100,000 people in the United States, and approximately 51% of those diagnosed survived their disease at least five years. Over the last two decades, incidence rates have fallen by nearly 26% between 1984 and 2004. This decline is likely due to increased colorectal cancer screening, which allows physicians to detect and remove colorectal polyps before they progress to cancer. United States Preventive Services Task Force (USPSTF) recommended screening for CRC should be performed in all persons aged 50 years and older. Yet, incidence is still high: colorectal cancer is the third most commonly diagnosed cancer for both men and women. As of 2004, approximately 48 cases of colorectal cancer were diagnosed per 100,000 people in the United States. About 65% of men and women diagnosed with colorectal cancer now survive their disease at least five years. American Cancer Society recommended the following screening tool for CRC, which includes fecal occult blood test (FOBT) annually, flexible sigmoidoscopy every 5 years as an option, colonoscopy as an option every 10 years, double contrast barium enema recommended every 5 years as an option. Colonoscopy is the gold-standard for evaluation of colonic pathology, but in certain situation where colonoscopy is not possible or incomplete due to procedural pain, colonic stenosis; elongated colon may be found in up to 26% of patients. Thus there has been a need to develop alternative diagnostic procedure to visualize large bowel. Currently available modalities like Barium enema, which has following drawbacks like 1) Highly subjective, 2) Bowel loop superimposed with one another without cross sectional image to see the small lesions, 3) Risk of ionizing radiation. CT Colonography is another alternative but it carries the risk of excessive ionizing radiation and contrast exposure. MR Colonography (MRC) is technically similar to CT Colonography with few advantages. In recent years major technologic advances in diagnostic MRI have led to improve image quality particularly with the use of Fast sequence and surface coil. Positive contrast like water/saline can be used to distend the colonic lumen; hence without radiation and contrast material we can study the colon using this technique.5,6 Sixty patients with suspected colonic pathology were evaluated, thirty patients underwent colonoscopy first then MRC, another thirty patients underwent MRC first which was followed by colonoscopy. Findings in both modalities were compared to know the merits and demerits of each modality. AIMS AND OBJECTIVES: 1. To find out the merits and demerits of standard tool colonoscopy and newer modality Magnetic Resonance Colonography (MRC) in assessing the various colonic pathology. 2. To find out the Sensitivity, Specificity. Positive predictive value and Negative predictive value of MRC in comparison with standard tool Colonoscopy. 3. To find out the role of MRC in patients with obstructive type of colonic lesion were further scope passage was not possible. MATERIALS AND METHODS: This comparative study between Colonoscopy and MR Colonography was carried out in the Department of medical Gastroenterology and Radiology Department of Madras Medical College, Chennai. This is the major referral tertiary care center available to the entire Tamilnadu, Pondicherry and neighboring states like Andhra Pradesh and Karnataka. The study was carried between the February 2008 to January 2010. (24 months). Patients who are attending Medical Gastroenterology Department with clinical diagnosis highly suspicious of colorectal pathology were included in this study. Sixty patients were taken up for study and out of sixty patients thirty patients underwent colonoscopy first then subjected to MR Colonography and another thirty patients were subjected for MR Colonography first then followed by Colonoscopy. Inclusion Criteria: 1. Patients with bleeding per rectum suggestive of colonic lesion rather than perianal problem like hemorrhoids or fissure. 2. Significant weight loss & Change in bowel habits with Positive FOBT. 3. Abnormal finding during rectal examination. 4. Patients with family history of Colorectal Cancer/ Polyposis with symptoms of bowel disease. Exclusion criteria: Patients with metal implants like Hip prosthesis, cardiac pacemaker and intracranial aneurismal coil were excluded from MR Colonography. SUMMARY AND CONCLUSION: This study includes total of sixty patients with a mean age of 47 years and the male female ratio of 2:1. Among the clinical symptoms and abnormal finding on examination the most common symptom being bleeding per rectum seen in 31%, Growth rectum in 21% and suspected IBD-UC in 10% and the remaining 38% constitute all other presentation. FOBT Positive in 25% of patients with suspected colorectal malignancy, clinically suspected TB abdomen in 11% of patients. Colonoscopic assessment of the entire colon up to cecum/ileum was possible in forty two patients (70%) and in the remaining eighteen patients (30%) scope not passed up to cecum due to obstructing lesion in sixteen patients (27%) and the patients intolerance to procedure in two patients (3%) in my study. Biopsy was taken from all patients with colorectal growth and inflammatory lesions, while doing colonoscopy. Biopsy taken from growth arising in Rectum, Sigmoid, and Transverse colon the yield rate was 100% and the Histopathology report (HPE) was Adenocarcinoma. Similarly Ascending colon growth biopsy revealed 100% positive for malignancy. Biopsy from Suspected Ileocecal TB revealed caseating granulomas in 50% and non-specific inflammatory infiltrate in another 50% of patients. Biopsy taken in patient with familial adenomatous polyposis showed adenomatous polyp (100%). Biopsy is very important in planning the management which is possible only with colonoscopy Out of eight patients with colorectal polyp, polypectomy done for five patients and the remaining three patients did not report for polypectomy. The obstructing type of lesions (27%) and poor patient tolerance (3%) accounts for 30% incomplete study, where in the alternative modality MRC was helpful to evaluate rest of the colon. Both colonoscopy and MRC detects lesion with same accuracy in thirty four patients (57%), colonoscopy detects lesions missed by MRC in twenty one patients (35%) and MRC detects the lesion missed by Colonoscopy in five patients (8%), because of non-passage of scope. (Fig - 5) Overall accuracy of Colonoscopy is 92% (both modality same accuracy in thirty four patients + colonoscopy scores over MRC in twenty one patients) in assessing colonic lesions. (Fig - 5) Overall accuracy of MRC is 65% (both modality same accuracy in thirty four patients + MRC detects lesion missed by colonoscopy in five patients) in accessing colonic lesion Extracolonic findings were detected by MRC in seven patients in addition to colonic lesions viz. Pelvic nodes, Liver metastasis, Gall stones. Left Renal calculi and Left sided Hydrouretonephrosis. Statistically while comparing the MRC with standard tool Colonoscopy the Sensitivity - 53%, Specificity – 67%, Positive predictive value – 83% and Negative predictive value – 32% and the p-value is also not significant (>0.05), suggesting MRC is only an alternate modality if colonoscopy is not possible. In future 3 Tesla MRI with advanced software may play an important role in evaluation of colonic lesions especially for screening Polyposis and Colorectal cancer but still colonoscopy will be needed for tissue diagnosis.

Item Type: Thesis (Masters)
Uncontrolled Keywords: Colonoscopy ; MR Colonography ; Comparative Study
Subjects: MEDICAL > Gastroenterology
Depositing User: Kambaraman B
Date Deposited: 09 May 2018 16:10
Last Modified: 09 May 2018 16:10

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