-IBIS-1.5.0-
tx
digestive system
colon cancer
diagnoses

definition and etiology

definition:
carcinoma of the colon and/or rectum, usually called "colorectal cancer"

etiology:
Colorectal cancer causes about 20% of deaths from malignant disease in the U.S. In Western countries, it ranks second only to skin cancer. Most of the cancers occur in the rectum or sigmoid colon and 95% are adenocarcinomas. It is predominantly a disease of the elderly; most patients are 60-75 years old. Females are at greater risk for colon cancer, males for rectal cancer. Etiologic factors include:
• "populations with a high incidence of colorectal cancer consume diets containing less fiber, and more animal protein, fat, and refined carbohydrates than populations with a low incidence of the disease." "...it seems likely that carcinogens are produced endogenously from dietary substances or intestinal secretions" (Merck).
• familial adenomatous polyps of the colon
• patients with a previous history of the disease
• women with a history of breast or uterine cancer
• patients with ulcerative colitis and, less significantly, Crohn's disease

signs and symptoms

Onset of symptoms is very gradual and depends on the tumor location, size, type and complications (e.g. if the tumor is irritating any adjacent organs, like the urinary bladder, or the stomach; or if it leads to bowel perforation and peritonitis).

signs and symptoms:
• rectal bleeding
• abdominal pain
• change in bowel habits and/or size/shape/color of stool: esp. gradually increasing constipation and black stool
• acute obstruction: colicky pain, increasing abdominal distention, failure to pass stools or gas
• weight loss
• anorexia

location specifics:
• right colon: may have palpable mass through abdominal wall; fatigue and weakness from anemia due to occult blood; obstruction (change in bowel habits) is usually a late sign
• left colon: obstruction is more of an issue here; often the patient will experience alternating constipation with diarrhea; stools may be overtly bloody
• rectum: primary symptom is defecation with bloody stools

lab findings:
• 65% of tumors are evident upon digital or sigmoidoscopic exam
• sigmoidoscopy/colonoscopy has surpassed barium studies as the procedure of choice for diagnosis
• biopsies of tumor
• stool analysis for occult blood
• elevated levels of CEA (serum carcinoembryonic antigen)
• anemia (usually normochromic, normocytic)

course and prognosis

Conventional treatment of choice is surgical resection and, less importantly, postsurgical procedures such as chemotherapy, radiation therapy, and immunotherapy. Postsurgical procedures have not been shown as particularly helpful or effective.

Prognosis varies with extent of disease, location in bowel, degree of wall infiltration, local or distant metastasis. In patients with cancer limited to the mucosa, the five-year survival rate is 70%; with spread to the lymph nodes, it drops to 30%.

differential diagnosis

• hemorrhoids
• diverticulitis: when it causes obstruction of the bowel
• ulcerative colitis
• other gastrointestinal disease


footnotes