Colorectal carcinoma, the commonest type of gastrointestinal carcinoma, accounts for a significant proportion of morbidity and mortality worldwide. It results from a combination of genetic and environmental risk factors.
The clinical features of colorectal carcinoma manifest due to the tumor itself or due to a local and metastatic spread of the tumor. However, it must be remembered that a certain proportion of patients are asymptomatic and are only detected incidentally or during screening. The common clinical manifestations arising from the tumor are rectal bleeding, change in bowel habits, rectal/ abdominal mass, anemia, weight loss, abdominal pain, pelvic pain, and urinary symptoms   .
Rectal bleeding is a common manifestation. This presents as either drops of fresh blood or as blood streaked on the stools . Dark-colored blood, in general, is more likely to be associated with colorectal cancer than bright red-colored blood . Sometimes, bleeding can occur in an occult fashion without the patient having taken any notice. However, long-term blood loss, even in minute quantities, leads to symptoms of anemia .
Digital rectal examination is the most specific test in physical examination and it may reveal the size of the tumor and features such as ulceration and local spread. It may also reveal a change in anal sphincter tone, which will indicate whether the tumor has spread locally to involve the nerves. Proctoscopy will help to further visualize the tumor.
Screening is an important part of diagnosing colorectal carcinoma and has led to its decline in incidence over time . The recommended mode of screening is colonoscopy every ten years from 50 years of age .
The mainstay of diagnosing colorectal carcinoma is colonoscopy followed by biopsy of the suspicious lesions.
Further testing is aimed at grading and staging the tumor that may have an implication on management.
Serum carcinoembryonic antigen (CEA) levels give an insight into prognosis.
Other tests which must be considered are ultrasonography (US) and magnetic resonance imaging (MRI) to assess the spread of the disease.
A chest radiography and abdominal computed tomography (CT) may also help to assess metastatic spread. Positron emission tomography (PET) scans are gaining popularity as an effective imaging modality to detect metastatic lesions.
Molecular genetic testing to detect various genetic mutations is rapidly gaining evidence as a guide for the treatment of metastatic colorectal cancer.