My Plan for Diagnosis of Chronic Constipation

Key Takeaways

• Chronic constipation should be assessed as primary or secondary; subtypes of primary constipation include normal transit, slow transit, and disorders of rectal evacuation.
• A full assessment of symptoms should be taken, along with a small panel of laboratory tests.
• It may be useful to consider consultation with a urologist or gastroenterologist.

Chronic constipation affects 9% to 15% of the general population. When encountering chronic constipation, the first consideration is whether the patient is dealing with primary or secondary constipation. The most common causes of secondary constipation are medications (eg, blood pressure medications, opioid analgesics, or even calcium supplements). Other causes of secondary constipation may include neurologic diseases such as Parkinson’s disease or myasthenia gravis or even dementia.

Constipation Subtypes
Most patients, however, have primary constipation, and within that there are 3 subgroups. Most patients (~80%) will have normal transit constipation. By contrast, a much smaller percentage of patients (<5%) have slow transit constipation, in which colonic transit is delayed. The remaining 15% to 20% have disorders of rectal evacuation. This last subgroup can overlap with both slow transit constipation and normal transit constipation.

Constipation Symptoms
The most common symptoms of constipation are infrequent bowel movements and difficulty with defecation. Patients may complain of abdominal discomfort, bloating, or a sense of obstruction. When evaluating these patients, it is important to ask about the array of symptoms that patients may be experiencing, not just the stool frequency.

We need to ask if they must use manual maneuvers to facilitate evacuation. Do they push up on their perineum, or in the case of females, do they have to push into the vagina posteriorly or anteriorly? If so, we should consider the possibility of rectocele and other disorders of rectal evacuation. Although these may be relatively uncommon, it is important to determine whether these maneuvers are part of the patient’s routine. You also may have patients who describe both constipation and diarrhea. However, if you take a careful history, you will usually discover that these patients just have constipation. That is, they will be constipated and not have a significant defecation for 3 or 4 days, but when they do, they will have a day of crampy abdominal pain and loose stool that is likely overflow diarrhea. So, when patients describe both stool extremes, consider chronic constipation as the underlying disorder.

Initial Evaluation
Diagnosing chronic constipation should not require many diagnostic tests. The American Gastroenterological Association guidelines recommend a complete blood count and metabolic panel (to make sure the patient is not hypercalcemic) and, in some cases, a thyroid function study. It is important to exclude anemia, hematochezia, or unintentional weight loss and to evaluate family history of organic gastrointestinal (GI) disease, including colon cancer or inflammatory bowel disease. Finally, the patient should have a digital rectal examination. That should encompass all of your preliminary evaluation.

Physiologic Testing for Patients Who Do Not Respond to Treatment
How should we approach patients who are treated but do not respond? Healthcare professionals may want to consider some additional diagnostic tests specifically looking for abnormal transit constipation subtypes to determine whether these are patients who lack coordination of their pelvic floor muscles.

It is important to understand that pelvic muscles are different from the rest of the muscles that line the GI tract. That is, the muscles of the pelvic floor are skeletal or striated muscles, and therefore they are under voluntary control. When one sits to defecate, a series of maneuvers facilitates the passage of stool out of the rectum or the left colon for evacuation, and that includes relaxing the internal and external anal sphincters. We contract muscles in the pelvic floor, specifically the puborectalis, which allows the anorectal angle to become less acute or, essentially, to straighten out. We increase the intra-abdominal pressure to facilitate forcing evacuation of the stool.

Although all of that is quite complex, it does not take much thought to coordinate those muscles. However, in some patients, that coordination is not complete or may even be dysfunctional. If we uncover this dysfunction, we can treat those patients with pelvic floor therapy. These patients will not respond to medical therapy, including both over-the-counter and prescription therapies.

To evaluate for slow transit constipation, healthcare professionals would consider colonic marker studies, using gelatin capsules in which radiopaque markers are incorporated. Patients ingest these capsules and undergo a radiographic study 3‑5 days later, and we note the location of the markers. Finding them on the right side of the colon is suggestive of slow transit constipation, because the markers should be much more distal after 5 days. However, if they accumulate in the rectosigmoid area, that does not allow us to completely exclude pelvic floor dysfunction.

It is important to distinguish between these 2 subtypes, because although patients with pelvic floor dysfunction may be helped with surgery, those with slow transit constipation may actually be worse off if they go to surgery and have pelvic floor dysfunction that has not been assessed and successfully treated.

Incorporation of Urology or GI Colleagues
This level of evaluation may be complex for those at the primary care level. You may want to enlist the help of your trusted gastroenterology colleagues, including colorectal surgery or even urogynecology. It is not uncommon for some patients to have urinary symptoms as well, so a team‑based approach may be helpful for these more refractory patients.

Most patients respond quite well to over-the-counter therapy, lifestyle modifications, or prescription therapies—or perhaps a combination of those. But for those patients who are more refractory, one must consider other etiologies, do a complete medication list, and involve patients in their care and diagnosis. These steps will improve their care and ensure cooperation both for evaluation and for treatment. It is important to identify the most bothersome symptoms for patients and to address those and thereby improve the quality of life for these patients.  

Your Thoughts?
Have you diagnosed patients with chronic constipation? What was difficult about their assessment? Share your thoughts and join the conversation.