Clinical History
An 80-year-old female patient presented with complaints of change in the bowel habits, weight loss and PR bleeding.
Imaging Findings
The patient presented with complaints of a change in the bowel habits, weight loss of half a stone over a period of 4 weeks and had noticed a small amount of blood per rectum. She was otherwise well
with no significant past medical history.She was a non-smoker. She was reviewed as an urgent case in the rapid referral cancer clinic. Sigmoidoscopy was performed, but resulted in failure due to the
presence of faeces in the rectum. She was therefore referred for a double contrast barium enema test, which revealed an eccentric annular constricting stricture of the distal sigmoid colon and a few
sigmoid diverticula.
Discussion
Colorectal cancer is the third commonest cancer worldwide and is the second leading cause of cancer death in the UK and United States. The incidence of colorectal cancer increases with age and is
approximately equally distributed among men and women. More than 90% of colorectal cancers occur in people older than 50 years old and the mean age at diagnosis is 70 years. Risk factors which help
in the development of colorectal cancers include - Neoplastic polyps, Inflammatory bowel diseases (mainly ulcerative colitis but also Crohn's disease to a lesser extent), smoking, low fibre diet,
family history and familial adenomatous polyposis. Presentation varies depending on the site of the cancer. Left-sided cancers present with bleeding, altered bowel habit and tenesmus. Right-sided
tumours present much later with weight loss, anaemia and abdominal pain/mass. Complications include obstruction of the bowel; perforation; intussusception and fistula formation. The spread is via a
direct invasion of the bowel wall and into the pericolonic fat and the adjacent organs. Distant spread is via the lymphatics and also haematogenously through the portal veins to the liver and via
systemic circulation to the lungs and bones. Most colorectal cancers are believed to arise via the adenoma–carcinoma sequence. Adenomatous polyps are premalignant and are a major risk in the
development of colorectal carcinoma. Approximately 50% of colorectal carcinomas arise in the rectum and rectosigmoid region; 25% occur in the sigmoid and the other 25% are found evenly distributed
through the rest of the bowel. The diagnosis of colorectal cancer requires examination of the whole colon, since 5% of the patients have a synchronous colon cancer and more than 30% have additional
adenomatous polyps. There are currently no official screening programs for colorectal cancer. Faecal occult blood testing has a low specificity rate and colonoscopy has several disadvantages
including the risk of perforation, bleeding and an inherent miss rate. There are many other imaging methods for detecting colorectal cancer. Though double contrast barium enema was previously the
initial method of choice, CT colonography is now the first line investigation in many institutions. Helical CT is used to generate axial images from which 3D reconstructions can be produced to form a
virtual colonoscopy. Preparation is done for optimum images with cleansing of the colon with bowel preparation and air insufflation. Rectal cancers are imaged preferentially by trans-rectal
ultrasound and MRI.
Differential Diagnosis List