How Constipation Is Diagnosed in Adults

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Constipation is a very common problem and refers to stools that are too hard or too small, difficult to pass, or infrequent (occurring less than three times per week). Constipation may exist on its own or it may be due to an underlying condition or problem such as an underactive thyroid gland, a neurological disorder, medication use, dehydration, or more seriously, intestinal obstruction or colorectal cancer.

Diagnosing constipation and teasing apart its potential causes can sometimes be done with a medical history and physical examination alone. In some cases, however, further tests may need to be performed, such as blood tests, a colonoscopy, or imaging studies.

It is important to note that constipation in children is assessed differently than in adults—the following information focuses on constipation in adults.

Medical History

During the medical history, your doctor will start by asking you questions about your past medical history and medication list. Example questions may include:

  • What medications, including laxatives or over-the-counter supplements, are you taking?
  • What medical conditions do you have, especially metabolic (for example, hypothyroidism or diabetes mellitus) or neurologic (such as Parkinson's disease or multiple sclerosis)?
  • Have you ever had abdominal surgery?
  • What is your daily diet and fluid intake and level of physical activity?

In addition, your doctor will ask you several specific questions about your symptoms. Some example questions may include:

  • Are you experiencing abdominal pain, bloating, or cramping between bowel movements? (These could be symptoms of irritable bowel syndrome.)
  • Have you experienced any blood in your stool and/or unintended weight loss? (These could be symptoms of colon cancer.)
  • Do you experience prolonged straining or need to use digital evacuation in order to pass stool? (These could be symptoms of pelvic floor dysfunction.)

Finally, your doctor will also likely inquire about the shape and consistency of your stool, as this can help pinpoint down a diagnosis. More specifically, your doctor may ask you to look at the Bristol Stool Chart to identify what your stool looks like.

Physical Examination

During your physical examination, your doctor will check your vitals and weight and then inspect and press on your abdomen to evaluate for swelling, tenderness, and masses or lumps. She or he will also use his stethoscope to listen to intestinal sounds in your abdomen.

In addition, your doctor will examine your rectum to look for various abnormalities like hemorrhoids and anal fissures (small tears in the tissue that lines your anus). He may also check your anal wink reflex by gently rubbing a cotton-tipped applicator on the skin around the anus. In response, the anal sphincter should tighten—the absence of such a reflex may indicate a nerve problem.

Moreover, your doctor may also ask you to strain (like when having a bowel movement) to identify potential rectal prolapse, fecal impaction (you may see leakage of stool), or pelvic floor dysfunction.

The last part of your physical examination will entail a digital rectal examination, in which your doctor will insert a lubricated, gloved finger into your anus. This maneuver can be used to further access for rectal tone, masses or tears, fecal impaction, and pelvic floor dysfunction.

Labs and Tests

Depending on findings from your medical history and physical exam, various blood tests and/or a colonoscopy may be ordered. For example, if your doctor suspects hypothyroidism as a potential cause of your constipation, a thyroid-stimulating hormone (TSH) blood test will be ordered.

Examples of other blood tests that may be ordered include:

Colonoscopy is not generally recommended for adults with constipation. However, if the below symptoms are present, an endoscopy evaluation (usually a colonoscopy, but sometimes a flexible sigmoidoscopy in younger patients), is generally warranted to rule out cancer or other serious conditions:

  • rectal bleeding
  • positive fecal occult blood test, indicating there is blood in your stool
  • iron deficiency anemia
  • unintended weight loss of 10 or more pounds
  • intestinal obstructive symptoms (such as severe bloating, inability to pass gas or stool, abdominal pain, and more)
  • recent onset of constipation without an obvious explanation
  • family history of colon cancer or rectal cancer
  • family history of inflammatory bowel disease

In addition, a colonoscopy is warranted if a person is about to undergo surgery for constipation or is age 50 years or older and has not yet undergone standard colo-rectal cancer screening with a colonoscopy.

Imaging and Other Diagnostic Studies

Sometimes, imaging and other diagnostic studies are warranted for specific potential diagnoses. For instance, if your doctor is worried about intestinal obstruction, abdominal X-rays may be ordered. Likewise, colonic transit studies may be ordered to evaluate how well stool moves through the colon.

Other diagnostic studies may include:

  • Anorectal manometry: A test that measures how well the anal sphincter, muscles surrounding the anus, and the rectum are functioning
  • Balloon expulsion test: A test that measures how long it takes to push out a balloon filled with water from the rectum
  • Defecography: An X-ray or magnetic resonance imaging (MRI) that shows the anus and rectum and how they change as a person has a bowel movement.

A Word From Verywell

While constipation is a very common problem, it may be a symptom of an underlying health condition or problem. This is why it's important to not self-diagnose but rather see a healthcare provider for a proper diagnosis.

Seeking medical attention is especially important if your constipation is lasting longer than a couple of weeks, is severe or new, or is associated with other worrisome symptoms like bleeding, unintended weight loss, fever, vomiting, or pain. Early intervention is always key. It's important not to panic if you do have constipation, but to take any unusual health issue seriously for your long-term health.

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Article Sources

  1. Jamshed N, Lee ZE, Olden KW. Diagnostic approach to chronic constipation in adults. Am Fam Physician. 2011;84(3):299-306.


  2. National Institute of Diabetes and Digestive and Kidney Diseases. Diagnosis of Constipation. 2018.


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