Approach to constipation: Clinical sciences

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Introduction0:00–0:34

Constipation is a common gastrointestinal condition characterized by infrequent bowel movements and difficulty passing stool.
It happens when the intestines don't move waste to the rectum properly, and pelvic muscles and anal sphincter don't coordinate well to expel stool.
Now, based on the cause, constipation can be classified as primary, also known as idiopathic or functional constipation; and secondary, which occurs as a side effect of some medications or due to another medical condition, such as malignancy.Now, if your patient presents with constipation, first, you should obtain a focused history and physical exam.

Focused H&P0:34–2:29

Always perform a digital rectal exam, including inspection, palpation at rest, and palpation during a simulated evacuation, which is performed by asking the patient to bear down on your finger as if they were having a bowel movement.
Your patient will typically report a history of infrequent bowel movements, usually fewer than three stools per week, as well as straining, hard stools, and a feeling of incomplete evacuation.
Additionally, history might reveal abdominal discomfort or bloating, and sometimes the patient might report the use of manual maneuvers to defecate.
Now, here’s a clinical pearl to keep in mind! Many patients find it embarrassing to discuss bowel habits, so they might not describe their symptoms in detail.
So, be sure to ask direct questions about things like digital manipulation to defecate, and ask them to describe the appearance of their stools.
You can use tools like the Bristol stool chart, which lists seven categories of stool based on shape and texture, to help patients describe their stool.
Next, in patients with acute onset constipation, always ask about the ability to pass gas, as failure to pass gas can signal bowel obstruction.
Other symptoms that point to obstruction include obstipation, which refers to severe or complete constipation with practically no stool passage and absence of flatus, and can be accompanied by abdominal pain, nausea, and vomiting.
Alright, moving on to the physical exam findings, which typically include fecal impaction and a palpable stool ball. Additionally, some patients may have anal fissures, hemorrhoids, or functional problems like pelvic floor dyssynergia.
This is when the anal sphincter fails to relax or the perineum does not descend when the patient bears down during evacuation.
Based on these history and physical exam findings, you can make the diagnosis of constipation. Once you diagnose constipation, it's important to look for red flag features that could indicate underlying serious conditions like malignancy.

Red flag features2:29–3:02

These include hematochezia, unintentional weight loss, a family history of colorectal cancer, acute onset of constipation in an older adult, change in stool caliber, anemia, and the presence of a rectal mass.
If any of these red flag features are present, you should consider colorectal cancer and proceed with an endoscopy, such as colonoscopy or flexible sigmoidoscopy, with a biopsy to look for obstructive lesions.

Colorectal cancer3:02–3:29

Endoscopy typically reveals an endoluminal, exophytic polypoid mass with or without bleeding and necrosis, while biopsy reveals malignancy.
In this case, you can diagnose colorectal cancer. Now, let’s go back and take a look at individuals with no red flag features.

Secondary constipation3:29–4:07

In these patients, your next step is to assess for secondary causes of constipation. These include medication side effects, commonly seen in patients taking opioid medications or iron supplements; endocrine or metabolic disorders like hypothyroidism, hypokalemia, or hypercalcemia; and neurogenic conditions, such as spinal cord injury or multiple sclerosis.
If you identify an underlying cause, diagnose secondary constipation. On the other hand, if there are no secondary causes, you should suspect primary constipation.

Primary constipation4:07–4:55

In this case, your next step is to start your patient on a trial of empiric therapy, which includes increasing dietary fiber or starting a fiber supplement, advising sedentary patients to increase their physical activity, and starting an over-the-counter laxative, such as an osmotic agent or a stimulant laxative.
Next, assess the patient’s response to empiric therapy. If they have an adequate response, meaning, the frequency of bowel movements and their symptoms improve, you can diagnose primary constipation, and no further workup is needed.
Note that a majority of your patients will likely fall into this category. On the other hand, if they have an inadequate response to empiric therapy, then you should proceed with additional testing.

Defecatory disorder4:55–5:56

First, you should order anorectal manometry and a balloon expulsion test. These tests measure pressures inside the rectum and anus and the ability of the pelvic muscles to expel stool from the rectum.
If the results are abnormal, diagnose defecatory disorder. In this condition constipation arises from difficulty in evacuating stool from the rectum.
Now, here’s a clinical pearl! If there’s a high suspicion of defecatory disorder, but the results of the anorectal manometry and balloon expulsion test are inconclusive, then you can order an imaging study called defecography.
Defecography is performed by placing a thickened barium mixture into the rectum, and taking images as the patient defecates.
Abnormal defecography results indicate a defecatory disorder.However, if the anorectal manometry and balloon expulsion test are normal, your next step is to order a colonic transit study.

Slow transit constipation5:56–6:28

During colonic transit studies, patients swallow radiopaque markers, which are then tracked through the gastrointestinal tract using X-rays.
If the markers are not passed within the expected time frame, then the test is abnormal, so you can diagnose slow transit constipation.On the flip side, if the colonic transit study results are normal, diagnose normal transit constipation, which is also referred to as a disorder of the gut-brain axis.

Normal transit constipation6:28–6:51

There are different types of normal transit constipation. One type is irritable bowel syndrome, which might be marked by alternating episodes of diarrhea and constipation, or dominated by either symptom.
Alright, as a quick recap... If a patient presents with constipation, start by assessing for red flag features.

Review6:51–7:52

If you find red flag features, order an endoscopy, like colonoscopy or flexible sigmoidoscopy, and biopsy to rule out colorectal cancer.
On the other hand, if there’s no red flags, assess for secondary causes of constipation, such as medication side effects, endocrine or metabolic disorders, or neurogenic disorders.
If you identify a secondary cause, diagnose secondary constipation. If there’s no identifiable cause, consider primary constipation; then, start your patient on empiric therapy and assess their response.
If there’s an adequate response, diagnose primary constipation. If there’s an inadequate response, proceed with anorectal manometry and balloon expulsion testing.
If these studies are abnormal, you can diagnose a defecatory disorder; if they’re normal, proceed to a colonic transit study, which can help you differentiate between slow and normal transit