How Opioid Induced Constipation Is Diagnosed

Opioid-induced constipation is a common condition that results from taking opioid medications for pain management. Constipation describes infrequent bowel movements or experiencing hard, dry stool that is difficult to pass. Opioid-induced constipation is usually diagnosed with a thorough history and physical exam.

This article will describe the tools used to diagnose opioid-induced constipation and list other common causes of constipation. 

Self-Checks/At-Home Testing

Opioid-induced constipation may start as soon as you begin taking opioid medications or it may develop slowly over time. It’s estimated that up to 4%–5% of the population in the United States regularly takes opioid drugs, and 40%–80% of them experience opioid-induced constipation.

While there is no way to test yourself for opioid-induced constipation, it is helpful to be aware of the signs and symptoms. Common symptoms of opioid-induced constipation include:

• Infrequent bowel movements
• Hard, dry bowel movements
• Pain or straining when toileting 
• Bloating
• Nausea
• Vomiting
• Abdominal pain or discomfort
• Gastroesophageal reflux disease (GERD, backing up of stomach acid into the food tube)
• Diarrhea (loose, watery stools)

Physical Examination

If you have developed any of the common symptoms of opioid-induced constipation, it’s time to see your doctor. Opioid-induced constipation is a relatively common problem and should be considered as a diagnosis anytime an individual takes opioid drugs. 

The first step to making a diagnosis is taking a thorough medical history. Healthcare providers will likely ask you about the frequency and consistency of your bowel movements. They will also ask if you have experienced pain or straining when having a bowel movement. 

During the physical exam, your physician will most likely palpate (examine by touch) your abdomen to feel for bloating or a backup of stool. If your physician is concerned that there is a problem with your anal sphincter, the muscles at the end of your rectum that control the release of stools, they may recommend a digital rectal exam (inserting a gloved finger to feel for abnormalities) as well. 

Labs and Tests

Opioid-induced constipation is usually diagnosed with a history and physical. However, your physician may recommend lab tests to determine if there are any other possible causes of your symptoms. Blood tests to expect include:

• Complete blood count (CBC): A CBC can detect signs of infection or anemia.
• Electrolyte panel: An electrolyte panel can help determine if you are experiencing electrolyte abnormalities or imbalances.
• Liver function tests: These can detect changes in liver function. Poor liver function can cause bowel issues such as constipation, bloating, pain, gas, and more.
• Albumin test: Albumin is the main protein in blood plasma. Low levels of albumin (hypoalbuminemia) can indicate malnutrition and other health concerns.

Imaging

It is uncommon to require an imaging study for the diagnosis of opioid-induced constipation. If your physician is concerned that there could be another underlying cause for your constipation, they may recommend further testing. 

If your healthcare provider believes that an imaging study is necessary, you might expect one of the following:

• Abdominal X-ray: Uses X-ray to examine the small intestine for blockages 
• Abdominal computed tomography (CT) scan: Uses X-ray technology to examine your intestines to look for blockages or other issues
• Magnetic resonance imaging (MRI) defecography: Uses magnetic waves to examine your rectum, sphincter, and pelvic floor
• Colonoscopy: Uses a scope to view the inside of the colon to look for polyps and test for colon cancer
  

Differential Diagnosis

Constipation is a very common condition that affects most of us at some point or another. Common causes of occasional or chronic constipation include:

• Irritable bowel syndrome (IBS): IBS is a common chronic condition that affects the large intestine and causes constipation and diarrhea 
• Diabetes: Diabetes (affects how your body turns food into energy) may damage the nerves in the gastrointestinal tract and lead to constipation
• Hypothyroidism: Hypothyroidism (underactive thyroid) causes processes in the body to slow down, including gastric motility (process of food passing through the digestive system), and leads to constipation.
• Celiac disease: Most people with celiac disease (intolerance to gluten found in some grains) experience diarrhea, but it’s estimated that up to 10% of people with celiac disease present with constipation. 
• Colon cancer: Colon cancer can cause both diarrhea and constipation. 

Barriers to Diagnosis 

Opioid-induced constipation is a relatively common problem but still goes undiagnosed too often. A 2019 study found that barriers to diagnosis include:

• Physicians’ lack of awareness of the problem
• Patients feeling embarrassed about bringing it up
• Doctors feeling uncomfortable about asking about constipation
• Lack of universal diagnostic guidelines
• Lack of specific treatment plans

Summary

Opioid-induced constipation is caused by the physiological changes that take place in the gastrointestinal tract from taking opioid medications. It is a relatively common condition and is usually diagnosed with a thorough medical history and possibly a physical exam as well.

Other diagnostic tools that may be used include blood tests, abdominal X-ray, abdominal CT scan, MRI, and colonoscopy. Other common causes of constipation include IBS, diabetes, hypothyroidism, celiac disease, and colon cancer. 

A Word From Verywell

If you have recently started taking a new opioid drug and are now experiencing constipation symptoms, you likely have opioid-induced constipation. Talk with your healthcare provider right away because this condition is treatable. Know that there are laxative medications that can relieve your symptoms and make passing stool easier and more comfortable.