Colitis

Colitis is inflammation of the inner lining of the colon and is associated with diarrhea, pain, and blood in the stool. There are numerous reasons for the colon to become inflamed including:

• infection,
  
• loss of blood supply to the colon,
  
• inflammatory bowel disease, and
  
• invasion of the colon wall with collagen or lymphocytic white blood cells.

Anatomy of the colon

The colon is a hollow, muscular tube that receives products of digestion from the small intestine and ultimately eliminates them from the body through the anus. The colon is located in the abdomen and has numerous sections that are named based on their location. Colitis can affect different sections of the colon.

• The colon begins in the right lower abdomen with the cecum (located just above the appendix) into which the products of digestion empty from the small intestine.
  
• The ascending portion of the colon then ascends from the lower to the upper right side of the abdomen.
  
• It traverses the abdomen as the transverse portion of the colon from the right upper to left upper abdomen before descending from the upper to the lower left side of the abdomen.
  
• The last portions of the colon are the sigmoid colon low in the abdomen and finally the anus.

The colon also has several layers. The mucosa (inner layer or lining) comes into contact with the products of digestion and fluid and actively removes water and electrolytes to help solidify the feces. A layer of smooth muscle (a special type of muscle) surrounds the inner layer and is responsible for squeezing and mixing the undigested food and transporting it through the length of the colon to the anus.

What are the causes (types) of colitis

All types of colitis are associated with inflammation of the colon, though some types may be more severe and potentially dangerous than others. When a patient complains of pain and diarrhea with or without bloody stool, it is important to diagnose the type of colitis since treatments are different for the different types of colitis.

Infectious colitis

Many bacteria normally reside in the colon; they live in harmony with the body and cause no symptoms. However, if disease-causing bacteria are ingested with bacteria-contaminated foods, these bacteria may infect the small intestine and/or colon. Common infecting bacteria include:

• Campylobacter,
  
• Shigella,
  
• E. Coli, and
  
• Salmonella.

These infections, with the exception of Campylobacter infection, often cause bloody diarrhea and can lead to dehydration from the loss of fluids in the diarrheal stools. Similar symptoms can be seen with viral and parasitic infections, though common viral infections of the gastrointestinal tract more often involve infection of the small intestine rather than the colon.

Sometimes colitis may occur after antibiotics have been prescribed for an infection elsewhere in the body. The antibiotic suppresses some of the normal bacteria within the colon and allows an overgrowth of another type of bacteria, some of which can lead to colitis. Most commonly the bacterium that overgrows is a bacterium called, Clostridium difficile (C. difficile, C. diff). This bacteria produces toxins that cause diarrhea, usually non-bloody, associated with a fever and is called C. difficile colitis or pseudomembranous colitis (because of the membrane-like clumps of pus that form on the inner lining of the colon).

Ischemic colitis

The colon can be thought of as a hollow muscle. It requires a supply of blood to bring oxygen and nutrients in order for the muscles to function normally. When the colon loses its supply of blood and becomes ischemic (isch= restricted + emia=blood supply), it may become inflamed. Ischemia or lack of blood supply causes pain, fever, and bloody bowel movements.

• As a person ages, the arteries that supply blood to the colon gradually narrow and can cause ischemic colitis. These arteries narrow even faster if the individual has diseases that promote narrowing of the arteries, for example, diabetes, high blood pressure, high cholesterol and smoking.
• Ischemia also may be brought on by low blood pressure or anemia (low red blood cell count) in association with the arterial narrowing, since these further reduce blood flow.
• The blood supply to the colon may be compromised because the blood vessels are mechanically obstructed, for example by a twisting of the bowel (volvulus) or a herniation of the colon through a small opening in the tissues within the abdomen (an incarcerated hernia).

Inflammatory bowel disease

Ulcerative colitis and Crohn's disease are the two types of inflammatory bowel disease (IBD) that give rise to colitis.

Ulcerative colitis always begins in the rectum and sigmoid colon and frequently progresses over time through the ascending, transverse, and then ascending colon. It is thought to be a disease caused by overactivity of the immune system and usually causes abdominal pain, and bloody, diarrheal bowel movements.

Crohn's disease may occur anywhere in the digestive tract - in the esophagus, stomach, small intestine, or colon - though it is most commonly involves the small intestine and colon. In Crohn's disease there may be "skip lesions," that is, abnormal segments interspersed between normal segments. If segments of the colon are involved, then symptoms of colitis may be present.

Microscopic colitis

There are two types of microscopic colitis, 1) collagenous colitis and 2) lymphocytic colitis. Either collagen or lymphocytes (a type of white blood cell) engorge the layers of the wall of the colon, presumably a result of inflammation. This is an uncommon illness and may be an auto-immune disease. It is seen more frequently in older women. The diarrhea often is watery, but no blood is present in the stool.

What are the symptoms of colitis?

Inflammation of the colon causes the muscle layers to go into intermittent spasm and cause cramp-like pain, which is pain that comes and goes. The pain usually is in the lower abdomen. Since the muscles fail to contract in a normal pattern and the colonic contents move through the colon rapidly, there is little opportunity for water to be reabsorbed. This leads to watery diarrhea. If the lining of the colon is inflamed and breaks down, bleeding may occur.

With colitis, particularly colitis involving the distal colon (rectum and sigmoid colon), the pain often crescendos and precedes a diarrheal bowel movement. After the bowel movement, the pain may relent but then returns with the next episode of pain.

Depending upon the cause of the colitis, fever, and possibly malaise may or may not be present.

When should I contact my doctor about colitis?

Diarrhea is a common symptom, is usually self limited, and usually requires only supportive care, rest, and clear fluids until it resolves. If the diarrhea persists, diagnosis of the cause and further care may be needed.

• Blood in the stool is never normal and should always be evaluated. The blood may be from a hemorrhoid bleed, however, other serious causes of bleeding need to be investigated. Colitis is not the only cause of rectal bleeding, other cause include diverticulitis, colon polyps, anal fissures, or cancer.
• Chronic diarrhea can lead to dehydration, and if severe enough, dehydration may require treatment with fluids. The symptoms of dehydration may include:
  • lightheadedness (dizziness) especially when going from the sitting or lying positions to the upright position,
    
  • weakness,
    
  • dry mouth, and
    
  • decreased output of urine.
• High fever associated with diarrhea may be a warning sign that an significant infection is present that may need evaluation by a health care practitioner and treatment.
  
• Abdominal pain is not normal, and while diarrhea may be associated with mild cramps, if a person has moderate or severe abdominal pain he or she should seek medical care.

How is colitis diagnosed?

Patient history

Diagnosis of colitis and its causes always begins with the taking of the patient's history. The information the patient provides helps the physician guide the direction for diagnosis and treatment.

• In patients with abdominal pain and diarrhea, it is important to find out when the symptoms began, how long they have lasted, whether they come and go, and what makes them better or worse. Questions may be asked about travel because infections may arise while traveling, particularly in undeveloped countries. Patients often ask if the cause of symptoms is food poisoning, but that is often a difficult question to answer immediately.
  
• If the patient has blood with bowel movements (which in general, is not normal) further questions may be explored to screen for colon cancer or polyps.
  
• Food poisoning not due to bacterial infections usually does not cause blood in the stool. Evaluation of the body's other systems (cardiovascular, neurological, etc.) may be necesseary.

Physical examination

Once the history is taken, physical examination will be helpful in determining potential causes of the symptoms.

• Signs of more severe disease with dehydration may include orthostatic changes in blood pressure and pulse rate (decreases in the former and increases in the latter upon standing). In patients who are low on fluid or blood, blood pressure and pulse may be normal when they lie flat but may change with standing; the blood pressure falls and the pulse rate rises.
  
• Temperature often is checked for fever.
  
• Examination of the abdomen will disclose areas of tenderness and potentially abnormal masses if tumors or Crohn's disease are present.
  
• The exam also may include a rectal examination to test the stool for blood and to feel for abnormal rectal masses.
  
• In patients where ischemic colitis is a consideration, the healthcare practitioner may examine the heart and listen for sounds of abnormal, restricted blood flow (bruits) in arteries located in the neck, groin, and abdomen as signs of coexisting vascular disease.
  
• In patients where there is clinical suspicion of viral infection, no further testing may be needed. However, in a patient who appears ill, dehydrated, or has significant pain, fever or blood in the stool, more evaluation may be required.

Other tests

Blood tests (complete blood count) may be useful to explore the possibility of anemia or low red blood cell count due to bleeding.

An elevated white blood cell count may be present as the body's response to infection. However, an elevated white blood cell count does not necessarily mean infection, since the white cell count may be elevated as part of the body's general response to any type of inflammation.

Blood chemistries may be measured looking for changes in electrolyte concentrations in the body, especially abnormal sodium and potassium levels that would suggest serious diarrhea or loss of fluid. Kidney function may be checked by measuring the BUN (blood urea nitrogen) and creatinine levels; this may be an important clue that patients are dehydrated. As well, certain bacterial causes of diarrhea may also cause kidney failure.

Stool samples will likely be collected for culture, searching for bacterial and parasitic infections as the cause of colitis.

Imaging

Colonoscopy is a test in which a gastroenterologist uses a thin, flexible tube with a fiberoptic camera attached it to look at the inside of the colon searching for the cause of the symptoms. The appearance of the colonic lining often allows the doctor to make the diagnosis and also provides the opportunity to look for tumors and polyps. Biopsies - small bits of tissue - an be removed from the mucosal lining during colonoscopy and then evaluated under the microscope to make or confirm a diagnosis of the presence or cause of colitis.

Computerized tomography and barium enemas are tests that are performed by a radiologist to explore the cause of colitis but often are ordered as part of the evaluation of abdominal pain or diarrhea.

How is colitis treated?

The treatment of colitis depends on the cause.

Often the initial treatment no matter what the cause of colitis is to rehydrate the patient and assist with the control of pain. Rehydration may occur by mouth, however, in patient's who cannot tolerate fluids orally, are too dehydrated, or have severe electrolyte abnormalities, intravenous fluids may be required.

What is the prognosis for a patient with colitis?

Patients with infectious diarrhea tend to get better relatively quickly with supportive care. Most infections will resolve with or without specific treatment such as antibiotics.

Patients with inflammatory bowel disease probably will require lifelong treatment to help control their symptoms. The goal, as with any long term illness, is to allow the patient to live a normal life with minimal symptoms from the disease.

Patients with ischemic colitis need to minimize their risk factors for progressive narrowing of the arteries. These are the same risks as for heart disease, including controlling high blood pressure, diabetes, and high cholesterol; and stopping smoking. Patients with severe ischemia that leads to dead (gangrenous) colon require surgery to remove the gangrenous segment.

Colitis At A Glance

• Colitis is inflammation of the inner lining of the colon. It may cause abdominal pain and diarrhea with or without bloody diarrhea. Fever may be present.
  
• There are numerous causes of colitis including infection, inflammatory bowel disease, ischemic and microscopic colitis.
  
• Blood in the stool is never normal and should not be ignored.
  
• Depending upon the history and physical examination, further testing may be required to find the cause of colitis.
  
• Treatment of colitis often is supportive and is aimed at maintaining adequate hydration and pain control while a diagnosis is being pursued.