Since most people with diverticulosis have no symptoms, the condition is usually detected during an imaging test for another gastrointestinal condition. When a patient is experiencing symptoms that suggest diverticulosis, a physician (often a gastroenterologist) will normally collect a medical history, perform a physical examination and order blood tests and imaging tests.

During the evaluation of medical history, patients will typically be asked about their bowel habits, symptoms, diet and any prescription and/or over-the-counter medications they may be taking. During the physical examination, the physician may press on the abdomen to check for fullness or tenderness and perform a digital rectal exam. This exam involves inserting a gloved, lubricated finger into the rectum to check for bleeding, blockage or tenderness. blood tests will usually be ordered to rule out infection.

The symptoms of diverticulosis and other gastrointestinal conditions, especially irritable bowel syndrome, are very similar. Because of this, the diagnosis of diverticulosis occurs only after imaging tests to look for the presence of diverticula. These tests are also important in ruling out the possibility of colon cancer. Imaging tests that may be used include:

• Barium x-ray. A special compound is consumed or inserted into the colon to make it visible in x-rays. This can be used to detect the pouches and is usually the first test performed. However, there may be a large margin of error with barium tests and further imaging tests are usually required.
  
  
• Colonoscopy. A narrow tube with a tiny camera is inserted into the rectum and through the colon while the patient is sedated. The image of the colon appears on a monitor for examination, allowing for the visual detection of diverticula.
  
  
• Sigmoidoscopy. This is similar to a colonoscopy, but only the sigmoid colon and sometimes part of the descending colon are examined for diverticula. The patient does not need to be sedated.
  
  
• Computed axial topography (CAT) scan. A series of x-rays taken from different angles to create a three-dimensional image of the colon may be used.