Colorectal Adenocarcinoma

• • Colorectal cancer second leading cause of cancer deaths (after lung)

  • Adenocarcinoma accounts for 95% of malignant colorectal tumors

  • Genetic predisposition in familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer (HNPCC)

  • Conditions predisposing to colorectal cancer

  • -Ulcerative colitis

    -Crohn colitis

    -Schistosomal colitis

    -Exposure to radiation

    -Presence of ureterocolostomy

  • Possible dietary influences

  • -High caloric intake

    -High saturated fat intake

    -Decreased dietary calcium

    -Decreased fiber intake

  • Carcinogenesis multi-step process involving dysfunction of tumor suppressor genes, including APC, DCC, P53

  • Distribution of colorectal cancer

  • -25% right colon

    -10% transverse colon

    -15% left colon

    -20-50% rectosigmoid colon

  • Spreads through direct extension, hematogenously, lymph nodes, transperitoneal, intraluminal

  • Synchronous lesions occur in 3-5%

Epidemiology

• • 156,000 cases diagnosed per year

  • 65,000 colorectal cancer deaths per year

  • Incidence increases with age

  • Colon cancer is more common in women than men

  • Rectal cancer is more common in men than women

  • Multiple synchronous colonic cancers found in 5% of patients

  • 5% lifetime risk

  • 6-8% occurs before age 40 years

Symptoms and Signs

• • Symptoms depend on anatomic location and extent of lesion

  • Right colon lesions may become large before symptoms develop

  • -May cause occult bleeding, anemia

  • Left colon lesions often cause crampy abdominal pain

  • Large bowel obstruction ~ 10% cases

  • Fatigue, weakness, vague abdominal pain, abdominal mass (< 10%), anemia

  • Constipation alternating with increased frequency of defecation

  • Dark or blood tinged stool

  • Change in stool caliber

  • Rectal cancers

  • -Hematochezia

    -Tenesmus

  • Physical exam findings may include abdominal mass, lymphadenopathy, rectal mass

Laboratory Findings

• • Patients may have microcytic, hypochromic anemia

  • Positive occult blood on guiac stool test

  • Carcinoembryonic antigen (CEA) elevation (nonspecific, more useful for surveillance following resection), prompts additional imaging (CT scan)

  • Elevation of biochemical markers (nonspecific): CA 19-9, CA 72-4, plasma prolactin

Imaging Findings

• • Contrast enema-filling defect, "apple core lesion"; constricted area or intraluminal mass

  • Total colonoscopy: Should be performed to evaluate lesion and presence of synchronous lesions

• • Ulcerative colitis

  • Crohn colitis

  • Ischemic colitis

  • Parasite infection, amebiasis

  • Diverticulitis

  • Diverticulosis

  • Appendicitis

  • Peptic ulcer disease

  • Other neoplasms of colon/rectum

  • -Lymphoma

    -Carcinoid

• • Complete history (including family) and physical exam

  • Total colonoscopy with biopsy

  • Obtain plain abdominal x-ray and water-soluble contrast enema in patients with bowel obstruction

  • Once diagnosis is made, staging studies should be performed

  • -Chest x-ray

    -CT scan:Helpful to assess extramural extension or metastatic lesions

    -Liver function tests

  • Endorectal US: Helpful for determining depth of invasion in rectal lesions

When to Admit

• • Bowel obstruction/perforation

  • Hemodynamically significant lower GI bleeding

• • Mainstay of management is surgical with good mechanical bowel prep

  • Lesion ...