NURS 443 Lecture Notes - Lecture 12: Ovarian Cancer, Muscularis Mucosae, Gastroenteritis
Colorectal Cancer
Colorectal cancer (CRC) is the third most common form of cancer and responsible for 9% of cancer deaths. It is
estimated that annually about 103,170 Americans are diagnosed with CRC.28 The incidence of CRC is presented in
eFig. 43-1 on the website for this chapter.
CRC is more common in men than in women. Mortality rates are highest among African American men and women.
The risk of CRC increases with age, with about 90% of new CRC cases detected in people older than 50. However,
the incidence of CRC in individuals over 50 is decreasing due to increased screening to detect precancerous lesions.
Etiology and Pathophysiology
Risk factors for CRC include a diet high in red or processed meat, obesity, physical inactivity, alcohol, long-term
smoking,
Cultural & Ethnic Health Disparities
Colorectal Cancer
● • African Americans are at the highest risk compared with other ethnic groups.
● • Incidence is declining in the United States except among African American men.
● • Among Asian Americans, this is the second most commonly diagnosed cancer, and it is the third most
frequent cause of cancer-related death.
and low intake of fruits and vegetables.28 Genetic conditions such as FAP and a personal history of IBD place an
individual at risk for CRC. About one third of cases of CRC occur in patients with a family history of CRC.
Hereditary diseases (e.g., FAP) account for about 5% to 10% of CRC cases. Hereditary nonpolyposis colorectal
cancer (HNPCC) syndrome (also called Lynch syndrome) is the most common form of hereditary CRC (see the
Genetics in Clinical Practice box).
Physical exercise and a diet with large amounts of fruits, vegetables, and grains may decrease the risk of CRC.
Long-term use of NSAIDs (e.g., aspirin) is associated with reduced CRC risk. (See Table 43-21 for a list of risk
factors.)
Adenocarcinoma is the most common type of CRC. Typically it begins as adenomatous polyps. Approximately 85%
of CRCs arise from adenomatous polyps (see Fig. 43-6).
As the tumor grows, the cancer invades and penetrates the muscularis mucosae (see eFig. 43-2 on the website for
this chapter). Eventually tumor cells gain access to the regional lymph nodes and vascular system and spread to
distant sites. (The stages of tumor growth are shown in Fig. 43-7.) Since venous blood leaving the colon and rectum
flows through the portal vein and the inferior rectal vein, the liver is a common site of metastasis. The cancer
spreads from the liver to other sites, including the lungs, bones, and brain. CRC can also spread directly into
adjacent structures.
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Genetics in Clinical Practice
Hereditary Nonpolyposis Colorectal Cancer (HNPCC) or Lynch Syndrome
Genetic Basis
● • Autosomal dominant disorder.
● • Mutations in MSH2, MLH1, MSH6, PMS2 genes.
● • These genes are involved in repair of mistakes when DNA is replicated.
Incidence
● • Affects 1 in 500 to 2000 people.
Genetic Testing
● • DNA testing is available.
Clinical Implications
● • Accounts for 5% of all colorectal cancers.
● • Individual with genetic mutation has 80% to 90% lifetime risk of developing colorectal cancer.
● • People with HNPCC have an increased risk of cancers of stomach, small intestine, liver, gallbladder,
upper urinary tract, brain, skin, and prostate. Occasionally, people with HNPCC also have colon polyps,
which occur at an earlier age than do colon polyps in the general population and are more prone to
become malignant.
● • Individuals with known genetic mutations need to be monitored with colonoscopy every year.
● • Women with HNPCC also have a greatly increased risk of endometrial and ovarian cancer.
● • Examination by pelvic ultrasound and endometrial biopsy should also be considered to screen for
endometrial cancer.
TABLE 43-21 RISK FACTORS FOR COLORECTAL CANCER
● • Family history of colorectal cancer (first-degree relative)
● • Personal history of inflammatory bowel disease
● • Personal history of colorectal cancer
● • Family or personal history of familial adenomatous polyposis (FAP)
● • Family or personal history of hereditary nonpolyposis colorectal cancer (HNPCC) syndrome
● • Obesity (body mass index ≥30 kg/m2)
● • Red meat (≥7 servings/wk)
● • Cigarette smoking
● • Alcohol (≥4 drinks/wk)
Clinical Manifestations
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CRC has an insidious onset, and symptoms do not appear until the disease is advanced. Common clinical
manifestations include iron-deficiency anemia, rectal bleeding, abdominal pain, change in bowel habits, and
intestinal obstruction or perforation.
Physical findings may include the following:
● •Early disease: Nonspecific findings (fatigue, weight loss) or none at all
● •More advanced disease: Abdominal tenderness, palpable abdominal mass, hepatomegaly, ascites
Right-sided lesions are more likely to bleed and cause diarrhea, while left-sided tumors are usually detected later
and could present with bowel obstruction (Fig. 43-8).
Due to increased emphasis on screening practices, colon cancer is now often detected during screening procedures.
Complications of CRC include obstruction, bleeding, perforation, peritonitis, and fistula formation.
Diagnostic Studies
Obtain a thorough history with close attention to family history (Table 43-22). Since symptoms of CRC do not
become evident until the disease is advanced, regular screening is advocated to detect and remove polyps before
they become cancerous. Beginning at age 50, both men and women at average risk for developing CRC should have
screening tests to detect both polyps and cancer based on one of these testing schedules.28
Tests that find polyps and cancer include the following:
● •Flexible sigmoidoscopy (done every 5 years)
● •Colonoscopy (done every 10 years)
● •Double-contrast barium enema (done every 5 years)
● •CT colonography (virtual colonoscopy) (done every 5 years)
Tests that primarily find cancer include the following:
● •Fecal occult blood test (FOBT) (done every year)
● •Fecal immunochemical test (FIT) (done every year)
Colonoscopy is the gold standard for CRC screening because the entire colon is examined (only 50% of CRCs are
detected by sigmoidoscopy), biopsies can be obtained, and polyps can be immediately removed and sent to the
laboratory for examination. People at average risk of CRC should have a colonoscopy every 10 years beginning at
age 50, except for African Americans, who should have the first colonoscopy at age 45.37
TABLE 43-22 COLLABORATIVE CARE: Colorectal Cancer
● Diagnostic
● • History and physical examination
● • Digital rectal examination
● • Testing of stool for occult blood
● • Barium enema
● • Sigmoidoscopy
● • Colonoscopy
● • CBC
● • Liver function tests
● Collaborative Therapy
● • Surgery
○ •Right hemicolectomy
○ •Left hemicolectomy
○ •Abdominal-perineal
resection
○ •Laparoscopic colectomy
●
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Document Summary
Colorectal cancer (crc) is the third most common form of cancer and responsible for 9% of cancer deaths. It is estimated that annually about 103,170 americans are diagnosed with crc. 28 the incidence of crc is presented in efig. Crc is more common in men than in women. Mortality rates are highest among african american men and women. The risk of crc increases with age, with about 90% of new crc cases detected in people older than 50. However, the incidence of crc in individuals over 50 is decreasing due to increased screening to detect precancerous lesions. Risk factors for crc include a diet high in red or processed meat, obesity, physical inactivity, alcohol, long-term smoking, About one third of cases of crc occur in patients with a family history of crc. Hereditary diseases (e. g. , fap) account for about 5% to 10% of crc cases.
