What is abdominal pain?

Abdominal pain is pain that is felt in the abdomen. The abdomen is an anatomical area that is bounded by the lower margin of the ribs and diaphragm above, the pelvic bone (pubic ramus) below, and the flanks on each side. Although abdominal pain can arise from the tissues of the abdominal wall that surround the abdominal cavity (such as the skin and abdominal wall muscles), the term abdominal pain generally is used to describe pain originating from organs within the abdominal cavity. Organs of the abdomen include the stomach, small intestine, colon, liver, gallbladder, and pancreas.

Occasionally, pain may be felt in the abdomen even though it is arising from organs that are close to, but not within, the abdominal cavity. For example, conditions of the lower lungs, the kidneys, and the uterus or ovaries can cause abdominal pain. On the other hand, it also is possible for pain from organs within the abdomen to be felt outside of the abdomen. For example, the pain of pancreatic inflammation may be felt in the back. These latter types of pain are called "referred" pain because the pain does not originate in the location that it is felt. Rather, the cause of the pain is located away from where it is felt.

What causes abdominal pain?

Abdominal pain is caused by inflammation (for example, appendicitis, diverticulitis, colitis ), by stretching or distention of an organ (for example, obstruction of the intestine, blockage of a bile duct by gallstones, swelling of the liver with hepatitis), or by loss of the supply of blood to an organ (for example, ischemic colitis).

To complicate matters, however, abdominal pain also can occur without inflammation, distention or loss of blood supply. An important example of this latter type of pain is the irritable bowel syndrome (IBS). It is not clear what causes the abdominal pain in IBS, but it is believed to be due either to abnormal contractions of the intestinal muscles (for example, spasm) or abnormally sensitive nerves within the intestines that give rise to painful sensations inappropriately (visceral hyper-sensitivity). These latter types of pain are often referred to as functional pain because no recognizable (visible) causes for the pain have been found - at least not yet.

How is the cause of abdominal pain diagnosed?

Doctors determine the cause of abdominal pain by relying on:

1. characteristics of the pain,
2. findings on physical examination,
3. laboratory, radiological, and endoscopic testing, and
4. surgery.
   

Special problem in irritable bowel syndrome (IBS) of diagnosing the cause of abdominal pain

As previously discussed, the pain of irritable bowel syndrome is due either to abnormal intestinal muscle contractions or visceral hypersensitivity. Generally, abnormal muscle contractions and visceral hypersensitivity are much more difficult to diagnose than other diseases causing abdominal pain, particularly since there are no typical abnormalities of the physical examination or the usual tests. The diagnosis is based on the history (typical symptoms) and the absence of other causes of abdominal pain.

Why can diagnosis of the cause of abdominal pain be difficult?

Modern advances in technology have greatly improved the accuracy, speed, and ease of establishing the cause of abdominal pain, but significant challenges remain. There are many reasons why diagnosing the cause of abdominal pain can be difficult. They are:

• Symptoms may be atypical. For example, the pain of appendicitis sometimes is located in the right upper abdomen, and the pain of diverticulitis on the right side. Elderly patients and patients taking corticosteroids may have little or no pain and tenderness when there is inflammation, for example, with cholecystitis or diverticulitis. This occurs because corticosteroids reduce the inflammation.
  

• Tests are not always abnormal.
  
  • Ultrasound examinations can miss gallstones, particularly small ones.
    
  • CT scans may fail to show pancreatic cancer, particularly small ones.
    
  • The KUB can miss the signs of intestinal obstruction or stomach perforation.
    
  • Ultrasounds and CT scans may fail to demonstrate appendicitis or even abscesses, particularly if the abscesses are small.
    
  • The CBC and other blood tests may be normal despite severe infection or inflammation, particularly in patients receiving corticosteroids.
  
  
• Diseases can mimic one another.
  
  • IBS symptoms can mimic bowel obstruction, cancer, ulcer, gallbladder attacks, or even appendicitis.
    
  • Crohn's disease can mimic appendicitis.
    
  • Infection of the right kidney can mimic acute cholecystitis.
  • A ruptured right ovarian cyst can mimic appendicitis; while a ruptured left ovarian cyst can mimic diverticulitis.
    
  • Kidney stones can mimic appendicitis or diverticulitis.
  
  
• The characteristics of the pain may change. Examples discussed previously include the extension of the inflammation of pancreatitis to involve the entire abdomen and the progression of biliary colic to cholecystitis.
  

Abdominal Pain At A Glance

• Abdominal pain is pain that is felt in the abdomen.
• Abdominal pain comes from organs within the abdomen or organs adjacent to the abdomen.
  
• Abdominal pain is caused by inflammation, distention of an organ, or by loss of the blood supply to an organ. Abdominal pain in IBS may be caused by contraction of the intestinal muscles or hyper-sensitivity.
  
• The cause of abdominal pain is diagnosed on the basis of the characteristics of the pain, physical examination, and testing. Occasionally, surgery is necessary for diagnosis.
  
• The diagnosis of the cause of abdominal pain is challenging because characteristics of the pain may be atypical, tests are not always abnormal, diseases causing pain may mimic each other, and the characteristics of the pain may change over time