Clinical Manifestations
The early symptoms of carcinoma of the colon are often mild and nonspecific, especially with tumors in the area of the cecum or ascending colon where obstruction is rare and where blood that is lost is well mixed with feces and therefore less apparent. A change in bowel habits, espeÂcially with leftsided lesions, may be the first symptoms. This can be diarrhea, constipation, alÂternation of diarrhea and constipation, a change in the caliber of the stool, or tenesmus. Pain with left-sided tumors usually results from partial obÂstruction, but pain with right-sided tumors may represent invasion of the colonic wall or adjacent structures. Hematochezia is common, as is conÂstant occult bleeding, leading to iron deficiency anemia with its associated symptoms of weakÂness, fatigability, and shortness of breath. The generalized symptoms of many malignancies-weight loss, anorexia, and malaise—are usually present late in the illness. Rarely patients may present with peritonitis due to tumor invasion and perforation of the colonic wall or with comÂplications from metastases such as jaundice or asÂcites.