**4. Clinical presentation**

#### **4.1. Symptoms**

Symptoms are common and prominent late in colon cancer when the prognosis is poor but are less common and less obvious early in the disease. Common symptoms include abdominal pain, rectal bleeding, altered bowel habits, and involuntary weight loss [58]. Although colon cancer can present with either diarrhea or constipation, a recent change in bowel habits is much more likely to be from colon cancer than chronically abnormal bowel habits. Less common symptoms include nausea and vomiting, malaise, anorexia, and abdominal distention.

Symptoms depend on cancer location, cancer size, and presence of metastases. Left colonic cancers are more likely than right colon cancers to cause partial or complete intestinal ob‐ struction because the left colonic lumen is narrower and the stool in the left colon tends to be better formed because of reabsorption of water in the proximal colon [59]. Large exophytic cancers are also more likely to obstruct the colonic lumen. Partial obstruction produces constipation, nausea, abdominal distention, and abdominal pain. Partial obstruction occa‐ sionally paradoxically produces intermittent diarrhea as stool moves beyond the obstruction.

Distal cancers sometimes cause gross rectal bleeding, but proximal cancers rarely produce this symptom because the blood becomes mixed with stool and chemically degraded during colonic transit. Bleeding from proximal cancers tends to be occult, and the patient may present with iron deficiency anemia without gross rectal bleeding. The anemia may produce weakness, fatigue, dyspnea, or palpitations. Advanced cancer, particularly with metastasis, can cause cancer cachexia, characterized by a symptomatic tetrad of involuntary weight loss, anorexia, muscle weakness, and a feeling of poor health.

#### **4.2. Signs**

Just as with symptoms, colon cancer tends not to produce signs until advanced. Anemia from gastrointestinal bleeding may produce pallor. Iron deficiency anemia can cause koilonychia manifested by brittle, longitudinally furrowed, and spooned nails; glossitis manifested by lingual erythema and papillae loss; and cheilitis manifested by scaling or fissuring of the lips. Hypoalbuminemia may clinically manifest as peripheral edema, ascites, or anasarca. Hypo‐ active or high-pitched bowel sounds suggest gastrointestinal obstruction. A palpable abdomi‐ nal mass is a rare finding that suggests advanced disease. Rectal examination, including fecal occult blood testing (FOBT), is important in the evaluation of possible colon cancer. Rectal cancer may be palpable by digital rectal examination. Other physical findings, although rare, should be systematically searched for, including peripheral lymphadenopathy, especially a Virchow's node in the left supraclavicular space; hepatomegaly from hepatic metastases; and temporal or intercostal muscle wasting from cancer cachexia. Very rare findings with colon cancer include a Sister Mary Joseph node caused by metastases to a periumbilical node, and a Blumer's shelf caused by perirectal extension of the primary tumor.

#### **4.3. Laboratory abnormalities**

**4.** Hormone Replacement Therapy

12 Colonoscopy and Colorectal Cancer Screening - Future Directions

**4. Clinical presentation**

muscle weakness, and a feeling of poor health.

for CRC.

**4.1. Symptoms**

**4.2. Signs**

Observational studies have demonstrated an association between hormone replacement therapy (HRT) in women and a reduction in both incidence and mortality from CRC. Possible mechanisms for the effect of HRT include a reduction in bile acid secretion (a potential promoter or initiator of CRC), as well as estrogen effects on colonic epithelium, both directly and through alterations in insulin-like growth factor with the use of estrogens. Overall, there appears to be a consistent reduction in the risk of CRC with the use of HRT. However, given the potential adverse effect of HRT, this should not be used as a primary preventive strategy

Symptoms are common and prominent late in colon cancer when the prognosis is poor but are less common and less obvious early in the disease. Common symptoms include abdominal pain, rectal bleeding, altered bowel habits, and involuntary weight loss [58]. Although colon cancer can present with either diarrhea or constipation, a recent change in bowel habits is much more likely to be from colon cancer than chronically abnormal bowel habits. Less common symptoms include nausea and vomiting, malaise, anorexia, and abdominal distention.

Symptoms depend on cancer location, cancer size, and presence of metastases. Left colonic cancers are more likely than right colon cancers to cause partial or complete intestinal ob‐ struction because the left colonic lumen is narrower and the stool in the left colon tends to be better formed because of reabsorption of water in the proximal colon [59]. Large exophytic cancers are also more likely to obstruct the colonic lumen. Partial obstruction produces constipation, nausea, abdominal distention, and abdominal pain. Partial obstruction occa‐ sionally paradoxically produces intermittent diarrhea as stool moves beyond the obstruction. Distal cancers sometimes cause gross rectal bleeding, but proximal cancers rarely produce this symptom because the blood becomes mixed with stool and chemically degraded during colonic transit. Bleeding from proximal cancers tends to be occult, and the patient may present with iron deficiency anemia without gross rectal bleeding. The anemia may produce weakness, fatigue, dyspnea, or palpitations. Advanced cancer, particularly with metastasis, can cause cancer cachexia, characterized by a symptomatic tetrad of involuntary weight loss, anorexia,

Just as with symptoms, colon cancer tends not to produce signs until advanced. Anemia from gastrointestinal bleeding may produce pallor. Iron deficiency anemia can cause koilonychia manifested by brittle, longitudinally furrowed, and spooned nails; glossitis manifested by lingual erythema and papillae loss; and cheilitis manifested by scaling or fissuring of the lips. Hypoalbuminemia may clinically manifest as peripheral edema, ascites, or anasarca. Hypo‐

Patients with suspected colon cancer should have routine blood tests including a hemogram with platelet count determination, serum electrolytes and glucose determination, evaluation of routine serum biochemical parameters of liver function, and a routine coagulation profile. About half of patients with colon cancer are anemic. Anemia, however, is very common, so that only a small minority of patients with anemia have colon cancer. Iron deficiency anemia of undetermined etiology, however, warrants evaluation for colon cancer, particularly in the elderly [60]. Hypoalbuminemia is uncommon, but not rare, in colon cancer. It usually indicates poor nutritional status from advanced cancer. Routine serum biochemical parameters of liver function are usually within normal limits in patients with colon cancer. Abnormalities, particularly elevation of the alkaline phosphatase level, often indicate hepatic metastases. The serum lactate dehydrogenase level may increase with colon cancer. Diarrhea associated with colon cancer can rarely produce electrolyte derangements or dehydration. Nausea and vomiting from colon cancer can rarely produce metabolic derangements of hypovolemia, hypokalemia, or alkalosis.

The serum carcinoembryonic antigen level is not useful to screen for colon cancer. It is only moderately sensitive. Although patients with very advanced cancer tend to have highly elevated levels, patients with early and highly curable colon cancer tend to have only mini‐ mally elevated levels, with considerable overlap with the levels of patients without colon cancer. It is poorly specific. Other colonic diseases or systemic disorders can cause a carci‐ noembryonic antigen elevation. Preoperative testing is, however, useful to determine cancer prognosis and to provide a baseline for comparison with postoperative levels. An elevated serum level preoperatively is a poor prognostic indicator: the higher the serum level the more likely the cancer is extensive and will recur postoperatively. After apparently complete colon cancer resection the serum level almost always normalizes; failure to normalize postopera‐ tively suggests incomplete resection. A sustained and progressive rise after postoperative normalization strongly suggests cancer recurrence. Patients with this finding require prompt surveillance colonoscopy to exclude colonic recurrence and abdominal imaging to exclude metastases.

#### **4.4. Unusual clinical syndromes caused by colon cancer**

Colon cancer can cause acute colonic obstruction, most commonly from exophytic intralu‐ minal growth, and most uncommonly from intussusception or volvulus. Obstruction typically occurs in the sigmoid colon because of the narrow lumen and hard stool in this region. Patients present with abdominal pain, nausea and vomiting, obstipation, abdomi‐ nal tenderness, abdominal distention, and hypoactive bowel sounds. Colon cancer can rarely perforate acutely through the colonic wall and cause acute generalized peritonitis, and can rarely perforate slowly to form a walled-off inflammatory mass or abscess with localized peritoneal signs [61]. Factors promoting colonic perforation include disruption of mucosal integrity because of transmural malignant extension or colonic ischemia, and increased intraluminal pressure because of colonic obstruction. Presentation with colonic obstruc‐ tion or perforation indicates a poor prognosis. Colon cancer rarely causes ischemic colitis because of colonic dilatation proximal to malignant obstruction or malignant infiltration of blood vessels. Colon cancer occasionally causes gross rectal bleeding because of cancer‐ ous mucosal ulceration.

#### **5. Colorectal cancer (crc) – screening**

Colorectal cancer is theoretically a preventable disease and is ideally suited to a population screening programme, as there is a long premalignant phase, during which there is ample opportunity to intervene with a variety of different screening modalities.

**Figure 4.** Colorectal cancer

**Figure 5.** Five-year survival of colorectal cancer for each Dukes' stage at diagnosis

Colorectal Cancer

15

http://dx.doi.org/10.5772/53524

Most CRCs are thought to arise from benign adenomatous polyps, a process that takes approximately five to ten years. This long premalignant phase makes the disease ideally suited to a population screening programme.

Early detection and removal of precancerous colon polyps and CRC may reduce both incidence and death rates related of CRC. It is recommended to begin screening at age 50 for asympto‐ matic persons who are at average risk. High-risk patients should have regular colorectal surveillance [45]. Several screening methods are used to detect CRC lesions. Colonoscopy is the best method and final assessment step for detection of CRC.

The ultimate aim of a screening programme for CRC is to reduce mortality from the disease, which may be achieved in two ways. As five-year survival is closely related to the stage at which the cancer is detected (patients with Dukes' stage A cancer have a greater than 90 per cent five-year survival rate, while those with Dukes' stage D disease have a 7 per cent fiveyear survival rate), any screening modality that results in early detection of the disease will have a beneficial effect on survival through more effective treatment (figure 5). Additionally, if benign adenomatous polyps are removed, cancer development is prevented, resulting in decreased mortality.

**Figure 4.** Colorectal cancer

**4.4. Unusual clinical syndromes caused by colon cancer**

14 Colonoscopy and Colorectal Cancer Screening - Future Directions

ous mucosal ulceration.

**5. Colorectal cancer (crc) – screening**

to a population screening programme.

decreased mortality.

Colon cancer can cause acute colonic obstruction, most commonly from exophytic intralu‐ minal growth, and most uncommonly from intussusception or volvulus. Obstruction typically occurs in the sigmoid colon because of the narrow lumen and hard stool in this region. Patients present with abdominal pain, nausea and vomiting, obstipation, abdomi‐ nal tenderness, abdominal distention, and hypoactive bowel sounds. Colon cancer can rarely perforate acutely through the colonic wall and cause acute generalized peritonitis, and can rarely perforate slowly to form a walled-off inflammatory mass or abscess with localized peritoneal signs [61]. Factors promoting colonic perforation include disruption of mucosal integrity because of transmural malignant extension or colonic ischemia, and increased intraluminal pressure because of colonic obstruction. Presentation with colonic obstruc‐ tion or perforation indicates a poor prognosis. Colon cancer rarely causes ischemic colitis because of colonic dilatation proximal to malignant obstruction or malignant infiltration of blood vessels. Colon cancer occasionally causes gross rectal bleeding because of cancer‐

Colorectal cancer is theoretically a preventable disease and is ideally suited to a population screening programme, as there is a long premalignant phase, during which there is ample

Most CRCs are thought to arise from benign adenomatous polyps, a process that takes approximately five to ten years. This long premalignant phase makes the disease ideally suited

Early detection and removal of precancerous colon polyps and CRC may reduce both incidence and death rates related of CRC. It is recommended to begin screening at age 50 for asympto‐ matic persons who are at average risk. High-risk patients should have regular colorectal surveillance [45]. Several screening methods are used to detect CRC lesions. Colonoscopy is

The ultimate aim of a screening programme for CRC is to reduce mortality from the disease, which may be achieved in two ways. As five-year survival is closely related to the stage at which the cancer is detected (patients with Dukes' stage A cancer have a greater than 90 per cent five-year survival rate, while those with Dukes' stage D disease have a 7 per cent fiveyear survival rate), any screening modality that results in early detection of the disease will have a beneficial effect on survival through more effective treatment (figure 5). Additionally, if benign adenomatous polyps are removed, cancer development is prevented, resulting in

opportunity to intervene with a variety of different screening modalities.

the best method and final assessment step for detection of CRC.

**Figure 5.** Five-year survival of colorectal cancer for each Dukes' stage at diagnosis
