Cancer of the Small Intestine

Cancer of the Small Intestine Introduction

The small intestine, or small bowel, lies between the stomach and the colon. The small intestine is about 6 m (20 ft) long. Its primary function is to digest and absorb nutrients. The small intestine makes up more than 70% of the length and 90% of the surface area of the gastrointestinal (GI) tract.

The most common cancerous (malignant) tumors of the small bowel include adenocarcinoma, lymphoma, sarcoma, and carcinoids.

• In industrialized countries, adenocarcinomas occur most often.
  
  
• In developing countries, lymphomas are much more common.
  
  
• All these tumors have the potential to invade the bowel wall, spread into adjoining lymph nodes, and move to distant organs (metastasize).

Risk Factors

Each year, US doctors diagnose about 1200 malignant small intestine tumors. This is a small number relative to the frequency of tumors in other parts of the GI tract.

• It has been proposed that the liquid nature of the small intestinal contents may be less irritating to the mucosa, the innermost lining of the small bowel.
  
  
• Rapid transit time in the small bowel may reduce exposure of the intestinal wall to cancer-inducing agents found in the intestinal contents.
  
  
• Other factors that might limit the presence or impact of potential cancer-inducing agents include the following:
  
  
  • A low bacterial count
    
    
  • A large lymphoid tissue component in the wall of the small intestine
    
    
  • An alkaline pH inside the small intestine
    
    
  • The presence of the enzyme benzpyrene hydroxylase
  
  
• Adenocarcinoma of the small bowel is associated with the following underlying conditions:
  
  
  • Crohn disease - An inflammation in the small intestine. Crohn disease usually occurs in the lower part of the small intestine, called the ileum. The inflammation extends deep into the lining of the affected organ, causing pain and making the intestines empty frequently, resulting in diarrhea.
    
    
  • Celiac disease - Gluten intolerance
    
    
  • Familial polyposis syndromes - An inherited disease in which the large bowel becomes carpeted by polyps of various dimensions during the second or third decade of life. If untreated, the disease invariably leads to cancer of the colon or rectum. Celecoxib (Celebrex) has been Food and Drug Administration (FDA) approved for FAP. After 6 months, celecoxib reduced the mean number of rectal and colon polyps by 28% compared to placebo (sugar pill) 5%.
  
  
• Cancer is 50 times more common in the large bowel than in the small bowel. Risk factors in the general population include the following:
  
  
  • Alcohol abuse
    
    
  • Consumption of salted or smoked meats and fish
    
    
  • Heavy sugar intake
  
  
• Risk factors for developing cancer of the small intestine in Crohn disease include the following:
  
  
  • Male sex
    
    
  • Long duration of disease
    
    
  • Associated fistulous disease: A fistula is an abnormal tube that passes from one surface to another, such as from the colon to the skin.
    
    
  • Surgical removal of part of the bowel
    
    
  • The risk of developing small intestinal cancer is 6 times greater for people with Crohn disease compared to the general population.
  
  
• Lymphoma of the small intestine is associated with celiac disease but is also strongly associated with weakened immune systems such as occurs with AIDS.