Appendicitis is often difficult to detect, particularly in children. However, it is crucial to diagnose the condition early. Once an appendix has ruptured and peritonitis has set in, the condition can be very difficult to treat. Children are more likely than adults to suffer a ruptured appendix. For this reason, parents should consult a physician anytime their child has a stomach ache that appears to be serious or unusual.

A physician will perform a complete physical examination and compile a thorough medical history. The physician will pay special attention to the abdomen, applying gentle pressure and quickly releasing it to see if the pain worsens, indicating an inflamed peritoneum. Signs of appendicitis include abdominal rigidity and a patient’s instinct to tense the abdominal muscles when pressure is applied, a response known as “guarding.” Other potential signs are pain when the patient lies on the left side and extends the right leg and pain when the right hip is rotated toward the center of the body.

The patient’s blood may also be tested to check for an elevated white cell count, which indicates the presence of an infection. A urine test can also help detect other conditions that might cause similar symptoms, such as a kidney stone (solid mass of tiny crystals that causes pain when it moves down the ureter) or urinary tract infection.

Imaging tests can help confirm the presence of appendicitis or another disease. An abdominal x-ray can reveal signs of obstruction, foreign bodies, perforation or a fecolith. An ultrasound scan(which uses high-frequency sound waves to create an image) can show inflammation of the appendix or reveal an ectopic pregnancy (pregnancy that occurs outside the uterus) or gallbladder disease. A computed axial tomography (CAT) scan (which uses a series of computer-generated x-rays to form a detailed image) is the most frequently used imaging test because it provides the most detailed and comprehensive look at the abdomen. Women of childbearing age will usually be given a pregnancy test before undergoing an x-ray procedure.

Pregnant women will typically be given an ultrasound examination as x-ray procedures may be harmful to a developing fetus. However, recent research shows that magnetic resonance imaging (MRI) may be safer and more effective than ultrasound in diagnosing appendicitis in this population.

In some cases, symptoms that appear to indicate appendicitis may actually indicate another disorder. These may include:

• Various digestive disorders. Many such disorders sometimes mimic the symptoms of appendicitis. These disorders include Crohn's disease (inflammation of the digestive tract), gastroenteritis (inflammation of the stomach and intestinal linings), Meckel's diverticulum (birth defect in which a small sac is present in the ileum), diverticulitis (infection or irritation of the diverticula) or intussusception (disorder in which blockage of the intestine occurs).
  

  

• Ectopic pregnancy. A pregnancy that occurs outside the uterus can cause pain similar to that associated with appendicitis.
  
  
• Ovarian cysts. A cyst that develops on the right ovary may mimic symptoms of appendicitis.
  
  
• Pelvic inflammatory disease (PID). Infection of a woman’s internal reproductive organs, which may be caused by sexually transmitted diseases. Pain associated with PID may closely resemble symptoms of appendicitis.
  
  
• Kidney stone. A stone from the right kidney may become stuck in the ureter, the long tube that runs from the kidney to the bladder. This can cause pain similar to that of appendicitis.
  
  
• Urinary tract infection. An infection that can occur along any part of the urinary tract (e.g., kidneys, ureters, bladder, urethra) and cause pain similar to that of appendicitis.
  
  
• Other diseases. Other illnesses that may cause abdominal pain include pneumonia and heart disease.