DIFFRENTIAL DIAGNOSIS

• Diverticular disease.
• Irritable bowel syndrome.
• Inflammatory bowel disease.
• Local rectal pathology. E.g. hemorrhoids.
• Ischemic colitis.
• Infective colitis
• Pneumatosis coli.
• Endometriosis
• Solitary rectal ulcer

If patient has mass in colon it should be differentiated from

• Tuberculosis
• Amebiasis
• Cytomegalovirus
• Fungal infections
• Extrinsic lesions

INVESTIGATIONS

• If CRC is suspected advise full blood count
• If CRC is suspected also advise liver function tests.
• If patient has ca colon advise X Ray chest
• Digital rectal examination and proctoscopy with or without sigmoidoscopy if available should be done but this should not delay definitive investigations.
• Flexible sigmoidoscope can reach deep enough into the bowel to detect about 60% of tumors [31].
• If screening sigmoidoscopy discloses a large adenoma (>1.0 cm), or adenomas of any size with tubulovillous or villous histology, or multiple adenomas; sigmoidoscopy should be followed by colonoscopy in these circumstances [33].
• Colonoscopy is the gold standard for diagnosis of colorectal cancer. At colonoscopy, up to 30% of subjects with distal colonic neoplasms have proximal lesions (up to 20% of these may be advanced) [30].
• If malignant obstruction precludes a full colonoscopy preoperatively, it should be carried out at a later time
• Attempt biopsy of every polyp under 5 mm in diameter. Polyps larger than 10 mm should be referred for complete excision at colonoscopy (no biopsy needed). Intermediate-sized polyps (greater than 5 mm and less than 10 mm) may be referred for colonoscopic removal [30]
• If the polyp was biopsied at flexible sigmoidoscopy and is hyperplastic on histology, no further exam is needed at this screening. Nonadenomatous polyps (juvenile, hyperplastic, lipomatous, inflammatory) have no precancerous potential and do not require referral for colonoscopy [30].
• If the colonoscopy is inadequate due to a partially obstructing lesion that precludes a more proximal advance of the colonoscope, the more proximal colon should be evaluated by radiologic means like CT colonography where available and if not available, use of a contrast enema to evaluate the more proximal colon is advised [32].
• Barium enema may be used if colonoscopy fails to visualise the caecum and/or the patient is unable to tolerate the procedure.
• Liver ultrasound, (occasionally intrarectal ultrasound) and CT or MRI is useful in staging. MRI is more specific than CT in showing liver metastases [22].
• Positron emission tomography (PET) is valuable for detection of recurrent colorectal cancer, but has little effect on staging of primary cancer [22].
• No consensus has been reached about the most sensitive method for detection of liver metastases of colorectal cancer. A meta-analysis [22] showed that PET is the most sensitive modality, and is also especially valuable for detection of extrahepatic disease. However, no randomised study has yet proved the value of PET in this setting, and therefore, CT and MRI remains the diagnostic standards.
• For patients with symptoms or a rising serum CEA level who is suspected of having metastatic disease but whose diagnostic workup is negative, PET scanning can potentially localize occult disease, permitting the selection of patients who may benefit from exploratory laparotomy [34].
• Elevated pre-treatment serum levels of carcinoembryonic antigen (CEA) have a negative prognostic significance (CEA is no use in screening but can be helpful in predicting relapse in patients after surgery suitable for further resection).
• If CEA is > 3 ng/ml in on smokers or > 5 ngram/ml in smokers, consider patient may have ca colon or rectum. It may also be raised in people with cancer of the pancreas, breast, ovary, or lung. CEA can also be elevated in cirrhosis, pancreatitis, kidney failure, inflammatory bowel disease, peptic ulcer disease, chronic obstructive pulmonary disease (COPD), or an obstructed bile duct.

STAGING

If patient is diagnosed to have ca colon determine the local and distant extent of disease spread in order to provide a framework for discussing therapy and prognosis by examining the biopsy specimen, having abdominopelvic ultrasonography/ CT for disease extent and X Ray chest for secondaries: