Pathophysiology of Colorectal Cancer

How does colorectal cancer develop?

The pathogenesis of colon cancer is complex. Colon cancer results from the accumulation of multiple genetic alterations that happen in a specific sequence over a period of time. The genetic alterations may result from sporadic mutations or from mutations that are inherited as discussed under risk factors for rectal and colon cancer.

The APC gene, which has an essential role in the regulation of the growth of intestinal epithelial cells, and is frequently mutated resulting in FAP. APC mutations can lead to accumulation of a type of oncogene in the cells, which can promote cancer development.

The right-sided tumors usually grow as polypoid masses that bleed. The bleeding can often be in the form of occult bleeding. The right-sided tumors rarely cause obstruction, while the carcinomas of the left side (distal colon) usually lead to bowel obstruction due to constriction of the bowel as the lesions are generally annular shaped. The tumors of the distal colon may also present with bleeding.

Majority of colon cancers are left-sided, but of late there has been a steady increase in the incidence of right-sided colon cancer in the US, Europe and Asia. The anatomic shift probably results from response to carcinogens, increased longevity, or genetic factors with defects in mismatch repair genes.

continue reading Colorectal Cancers Types, Symptoms by Location and Spread

Who is at risk of developing colon cancer?

The development of colorectal cancer is complex interplay of  acquired and inherited factors. It should be noted that not every person with one or more of the risk factors will develop cancer of the colon and/or rectum. High risk patients, however, should be vigilant, undergo routine screening and undertake any lifestyle measures that may reduce the risk.

Age

The most important risk factor is age. The peak age of incidence is 60 to 79 years of age. The epidemiological studies show that there is a 0.5 to 2% chance that an unscreened individual aged above 50 years may have colon cancer and there is also a similar chance for carcinoma-in-situ of the colon (precancerous stage). The same group has 7 to 10% chance of harboring large adenomatous polyps of the colon, which can turn malignant in some individuals.

continue reading Inherited and Acquired Risk Factors for Rectal and Colon Cancer

A pleural effusion is the excessive accumulation of fluid between the two layers of pleura that surrounds the lungs (pleural space). There is continuous formation of fluid in the pleural cavity which is continuously reabsorbed. This is normal. The balance between secretion and reabsorption is such that only a small amount of pleural fluid exists in the cavity – about 15mL. Small pleural effusions may cause mild or no symptoms. Large pleural effusions can limit the normal expansion of the lungs during breathing.

Diagnosis of a Pleural Effusion

Signs of a Pleural Effusion

A pleural effusion is detectable clinically only when the quantity of accumulated fluid exceeds 500 ml. The following signs may be evident :

• Chest movement in relation to breathing is reduced on the affected side.
• Breath sounds are reduced on the affected side.
• Percussion over the fluid-filled area gives a dull note (stony dullness).
• Tracheal deviation may be a result of the lungs being pushed opposite to the affected side as a result of a massive effusion.

continue reading Diagnosing a Pleural Effusion (X-Ray Pictures) and Treatment

Pleural tap

A pleural tap can be performed for diagnostic purpose or for therapeutic reasons to drain the fluid around the lungs. A needle or a canula is passed into the pleural space and a small quantity, about 30 to 50 ml, of the fluid is collected for analysis. In some patients, with a small pleural effusion, this diagnostic procedure is usually combined with the treatment. A pleural tap helps in the diagnosis of the cause of the pleural effusion in about 80% of the patients. It may help in excluding certain diseases in the remaining individuals, even if the procedure may not be diagnostic.

The procedure is not indicated in individuals with coagulation (blood clotting) disorders that cannot be controlled. It is also done with great deal of caution in patients on mechanical ventilation as in with emphysema, those with only one functional lung and other high risk conditions.

A pleural tap can be complicated at times by pneumothorax (air accumulation in pleural cavity) or hemorrhage. These complications can be minimized with use of ultrasound for guiding the needle used for the pleural tap. Some individuals can develop sudden hypotension during the procedure (vasovagal). Other complications include pain, surgical emphysema (accumulation of air in the skin and subcutaneous tissue), infection, and puncture of spleen or liver.

continue reading Drainage of Pleural Fluid – Procedures, Tests and Results

The retroperitoneal space is the area outside the peritoneum at the back of the abdominal cavity. A retroperitoneal abscess is a collection of pus in this retroperitoneal space. It can develop due to spread of an infection from adjacent organs or an infection of the blood as is seen with other types of intra-abdominal abscesses (abscess in the abdomen). Renal and gastrointestinal diseases are the most common conditions leading to a retroperitoneal abscess. A psoas abscess is also a type retroperitoneal abscess. It is collection of pus in the iliopsoas muscle compartment and can drain downwards to present as a swelling in the upper part of the thigh.

continue reading Retroperitoneal Abscess and Psoas Muscle Abscess