April 18, 2020

Approximately 1 in 6 people experience chronic constipation (CC), a condition that can significantly affect quality of life and is a frequent cause for referrals to gastroenterologists and colorectal surgeons within the United States. Although it's more common in women and older adults, especially those living in care facilities, chronic constipation can affect people of all ages, races, ethnicities and socioeconomic groups.

CC is either primary or secondary, a classification determined from patient history and results from examinations and laboratory tests. Primary disorders include normal transit, slow transit or defecatory disorders (DD). Secondary causes include medications such as opioids and anticholinergics, several neurological conditions, and diseases affecting the colon. Colonic sensorimotor disturbances and pelvic floor dysfunction (such as defecatory disorders) are the most widely recognized pathogenic mechanisms. Additional factors, such as reduced caloric intake, disturbances of the microbiome, anatomical issues or medications, also can contribute.

In a review article published in Gastroenterology in 2020, co-authors Adil E. Bharucha, M.B.B.S., M.D., and Brian E. Lacy, M.D., Ph.D., provide an overview about the pathophysiology and appropriate clinical evaluation of CC, and discuss options for managing defecatory disorders and medically refractory chronic constipation. Dr. Bharucha is a gastroenterologist at Mayo Clinic's campus in Rochester, Minnesota, and Dr. Lacy is a gastroenterologist at Mayo Clinic's campus in Jacksonville, Florida. In the Q&A that follows, Dr. Bharucha answers questions about this common disorder.

What does an initial clinical evaluation for chronic constipation typically include?

Clinical evaluation for this condition can include analysis of a bowel symptom questionnaire, a two-week bowel diary, and information on prior bowel habits, including when those habits changed and the patient's perception of what "normal" is. Determining if patients have abdominal pain related to bowel movements can help differentiate between chronic constipation and constipation-predominant irritable bowel syndrome (IBS-C). The Bristol Stool Form Scale offers a simple way to characterize stool form, which is a marker of colonic transit.

Many patients have coexisting gastrointestinal symptoms, such as bloating, dyspepsia, and fecal incontinence. And a complete evaluation should also include a review of other related factors, including medications, diet, lifestyle, toileting habits, history of abuse, medical conditions, obstetric history and surgery. In patients who do not experience alarm symptoms, a complete blood count and age-appropriate screening for colon cancer are the only tests necessary. Assessment of serum calcium or sensitive thyroid-stimulating hormone (TSH) is not required unless there are other features to suggest hypo- or hypercalcemia or hypothyroidism.

A meticulous and directed physical examination can reveal an organic cause for constipation, such as an abdominal mass, or discriminate between defecatory disorders and other causes of chronic constipation. Often overlooked, a digital rectal examination is required for every constipated patient and can help identify structural disorders (such as anal fissures, hemorrhoids, fecal impactions, descending perineum syndrome or anorectal cancer) and pelvic floor dyssynergia.

What are some appropriate first line treatments for chronic constipation?

Clinicians and their patients should discuss the benign nature of this condition and the efficacy, safety and cost of available treatment options. Initially, most patients can be treated with a fiber supplement or an osmotic laxative supplemented by a stimulant laxative. These agents are as effective as and less costly than agents requiring a prescription.

What additional steps do you take with patients who don't respond to over-the-counter agents?

Patients with persistent symptoms should be referred for anorectal testing to evaluate for defecatory disorders. The Rome IV criteria for primary constipation have established these three classification categories of CC: functional constipation (FC), constipation-predominant irritable bowel syndrome (IBS-C), and defecatory disorders (DDs), also called functional outlet obstruction, anorectal dyssynergia or pelvic floor dysfunction.

What tests are available for diagnosing defecatory disorders?

Defecatory disorders are caused by reduced rectal propulsive forces and increased resistance to evacuation. Assessment of colonic transit followed by assessment of colonic motility with manometry and a barostat can help identify colonic dysmotility and impaired rectal evacuation. Manometry is useful for revealing reduced propagated and nonpropagated activity and reduced phasic contractile responses. Manometry catheters measure phasic pressure activity, while barostat balloon devices also record colonic tone.

What is unique about Mayo Clinic's diagnostic approach and capabilities?

Our assessments are comprehensive, practical and multidimensional, and they are designed to examine transit and anorectal functions. We can simultaneously evaluate gastric, small intestinal and colonic transit with a single test in 48 hours. Available anorectal tests include manometry, rectal barostat, and both barium and magnetic resonance (MR) defecography. We also provide colonic manometry and barostat assessment. To my knowledge, Mayo Clinic is unique in offering all of these tests in our clinical practice, backed by an extensive database of normal values.

Mayo Clinic's use of high-resolution anorectal manometry and MR defecography reflects the influence of our active research program. These tests and normal values were developed through research studies. Some tests, such as barium defecography, that are shunned at other institutions flourish at Mayo Clinic. This approach allows us to tailor the tests to the needs of our patients. We continue to push the envelope by integrating imaging and manometry into our research studies. As always, many research projects underway today will influence tomorrow's clinical practice.

What is Mayo Clinic's approach to treating patients with defecatory disorders?

Because defecatory disorders primarily develop via maladaptive learning of pelvic floor or sphincter contraction during defecation, patients with this diagnosis often respond to treatment with pelvic floor biofeedback therapy. Mayo Clinic has a two-week pelvic floor biofeedback therapy program that has a considerable success rate. Again, the therapies we offer are comprehensive. Although pelvic floor dysfunction is common, biofeedback therapy is not widely available within the United States. While we also offer surgery, in contrast to some other institutions, we recommend this approach for only a tiny fraction of patients with chronic constipation.

What treatment options are available for patients with chronic constipation who don't have a defecatory disorder?

For this population, treatment with intestinal secretagogues and prokinetic agents may be warranted. Peripherally acting m-opiate antagonists are another option for opioid-induced constipation. Although more expensive than over-the-counter agents, these agents are effective and relatively safe treatment options. A small minority of patients with slow transit constipation may require and benefit from a subtotal colectomy to manage symptoms. To date, there are no published studies comparing the efficacy of inexpensive laxatives with newer drugs that use different mechanisms.

For more information

Bharucha AE, et al. Mechanisms, evaluation, and management of chronic constipation. Gastroenterology. 2020;158:1232.