Most people with constipation will not need extensive testing. Testing is usually required in cases of severe or sudden constipation, when blood is found in the stool and/or for older adults.

Physicians often rely on a patient’s report of symptoms in diagnosing and determining treatment for constipation. A medical history will include questions about the duration and severity of symptoms. Current medications, eating habits and levels of physical activity may also be discussed.

Chronic constipation is suggested when any two of the following factors occurs for a total of 12 weeks (not necessarily consecutive) in the past year:

• Straining during bowel movements
• Hard stool
• Sensation of incomplete defecation
• Sensation of blockage or obstruction
• Having less than three bowel movements per week

A physical examination may include a digital rectal examination. This involves use of a physician’s gloved, lubricated finger to evaluate the strength of anal sphincter, and to detect any tenderness, obstruction or blood in the area.

Additional tests that may be conducted when a patient has constipation include:

• Fecal tests. Stool is tested for the presence of occult bleeding (subtle traces of blood not visible to the naked eye) that may indicate an underlying disease, such as colorectal cancer.
  

  

• Blood tests. Blood is drawn and tested for evidence of thyroid or other disorders that may be causing the constipation.
  
  
• Colorectal transit study. Patients swallow capsules containing small markers that can be visible when x-rays are taken three to seven days after the capsule is swallowed. This may be used in cases of chronic constipation to identify how well food moves through the colon.
  
  
• Anorectal function tests. Used to identify dysfunction of the anus or rectum. Tests include a pressure-sensitive tube inserted into the anus to measure the muscle contractions in the anal sphincter and a defecography x-ray that can measure the completeness of defecation.
  
  
• Barium enema x-ray. X-rays of the colon and rectum are taken after a patient has an enema of a chalky substance (barium) inserted into their bowel. The barium enables images of internal organs to show up clearly on x-ray. This method may be preferred if constipation is accompanied by rectal bleeding. Barium enema x-rays may be used to identify cancer, intestinal obstruction or Hirschsprung's disease (a birth defect that causes intestinal blockage) in patients with constipation.
  
  
• Colonoscopy. A flexible tube (with light and camera attached) is inserted into the patient’s anus and through the entire colon. This method is used to identify any abnormalities, including whether colorectal cancer may be causing the constipation. A biopsy may be performed during this procedure and color pictures may be taken.
  
  
• Sigmoidoscopy. Similar to a colonoscopy, although the tube is only inserted up to the lower part of the colon. May help identify problems in the rectum and lower colon in patients with constipation.