Irritable bowel syndrome: Clinical sciences

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Introduction0:00–0:35

Irritable bowel syndrome, or IBS for short, is a chronic bowel condition characterized by recurrent abdominal pain associated with abnormal bowel movements.
The cause is unknown but could be related to changes in the normal gut microbiota, autonomic dysfunction, altered motility of the gastrointestinal tract, and psychological factors.
Now, based on the clinical manifestations, IBS can be diarrhea-predominant, constipation-predominant, or mixed.Generally, individuals with irritable bowel syndrome are stable, so first, you should obtain a focused history and physical examination.

Focused H&P0:35–1:39

History findings typically include bowel habit changes for at least 6 months, which are usually related to diarrhea or constipation.
Your patient will also report abdominal pain or discomfort that’s typically relieved with defecation. In some cases, the patient could report abdominal bloating, or they might have a history of depression, anxiety, fibromyalgia, trauma, or recent infectious gastroenteritis.
On the physical exam, you might notice abdominal tenderness during palpation, or find hemorrhoids or anal fissures on the rectal exam.
Now, here’s a clinical pearl! Describing stools can be challenging for some patients.
To make it easier, you can use a tool called the Bristol Stool Scale, which ranks stool from 1, solid lumps or balls to 7, watery diarrhea.Now, based on these history and physical exam findings, you should suspect a chronic bowel condition.

Suspect chronic bowel condition1:39–2:58

But, before you diagnose irritable bowel syndrome, first, you need to assess your patient for red flag features, which could indicate serious underlying conditions, like colorectal cancer.
These include hematochezia, unintentional weight loss, a family history of colon cancer, acute onset of constipation in an older adult, change in stool caliber, anemia, and the presence of a rectal mass.
Next, order labs to rule out other non-malignant gastrointestinal conditions with similar clinical manifestations. Order CBC to assess for anemia or infection; inflammatory markers like ESR and CRP to look for inflammation; and a TSH to assess for thyroid dysregulation.
Additionally, don’t forget to check a tissue transglutaminase IgA, or tTg-IgA for short, to evaluate for possible Celiac disease.
Lastly, obtain a fecal calprotectin to rule out colonic inflammation, which may indicate uncontrolled inflammatory bowel disease.

Alternative Diagnosis2:58–4:01

Now, if red flag features are present or if the labs reveal abnormalities, there’s a higher chance that your patient is presenting with another condition.
For instance, the CBC might reveal low hemoglobin indicating anemia, or elevated white cell count, suggesting an underlying infection.
Next, elevated ESR or CRP, are highly suggestive of ongoing inflammation, which can be seen in inflammatory bowel disease, such as Ulcerative Colitis and Crohn disease; while high or low TSH could indicate an underlying thyroid condition.
Furthermore, your patient could present with a positive tTg-IgA, which points to Celiac disease; whereas elevated fecal calprotectin points to inflammatory bowel disease again.
So, if you notice any of the red flags or labs reveal abnormalities associated with other conditions, you should consider an alternative diagnosis.

Rome IV criteria4:01–4:42

On the flip side,if no red flag symptoms are present and the labs and fecal calprotectin are normal, you should suspect IBS.
In this case, your next step is to assess for Rome IV Criteria, which define IBS as recurrent abdominal pain that occurs at least 1 day per week in the last 3 months, with at least 2 two of the following criteria: the pain is related to defecation, a change in stool frequency, or a change in stool form.
If criteria are not met, consider an alternative diagnosis. On the other hand, if the Rome IV criteria are met, diagnose IBS.
Once you diagnose IBS, your next step is to start management.Now, as part of management, there are four recommendations you should give to your patient.

Management of IBS4:42–5:49

The first one is diet modification, which includes consuming soluble fiber, and a trial of a diet low in a specific set of carbohydrates, which is also known as the low FODMAP diet.
Some examples of foods that your patient should limit include potatoes, brown rice, oats, and almonds. Next up is peppermint oil, which has been shown to relax smooth muscle and target spasming of the GI tract; as well as tricyclic antidepressants, like amitriptyline or nortriptyline, which are beneficial in relieving IBS-associated abdominal pain.
Finally, gut-directed psychotherapy can be beneficial since IBS has a strong association with mental health. Now, here’s a clinical pearl!
You should not prescribe antispasmodic medications or probiotics to patients with IBS, because there is a lack of evidence supporting their efficacy.Okay, once you start the initial management, you need to assess the subtype of irritable bowel syndrome since the patient can benefit from additional therapeutic options.

Assessing IBS Subtype5:49–6:19

Main IBS subtypes include the diarrhea-predominant type, or IBS-D; and the constipation-predominant type, or IBS-C. Keep in mind that some patients may present a mixed subtype, called IBS-M, that includes features of both IBS-D and C.First, let’s talk about patients with the diarrhea-predominant type.

IBS-D6:19–6:53

In this case, the goal is to increase stool firmness or decrease bowel movement frequency. There are two options that you should consider.
The first one is the non-absorbed antibiotic rifaximin, which works by addressing bacterial growth associated with diarrhea.
The other option is the mixed opioid agonist-antagonist called eluxadoline, which targets opioid receptors in the GI tract and helps regulate motility and secretion.
On the other hand, there’s the constipation-predominant type. Treatment for these individuals is geared towards stool softening and increasing bowel movement frequency.

IBS-C6:53–7:50

There are two options available for treatment. The first one includes chloride channel activators, like lubiprostone; while the second one covers guanylate cyclase activators, like linaclotide or plecanatide.
Both groups of medications help soften the stool and stimulate bowel movement. Now, here’s one last clinical pearl!
Another medication that you can consider for the management of constipation-predominant IBS is tegaserod, which is a serotonin 5-HT4 agonist that increases colonic transit time.
But, keep in mind that this medication is reserved only for biologically female individuals that are younger than 65 years and have a low risk of cardiovascular conditions.Alright, as a quick recap… Irritable bowel syndrome is a chronic bowel condition characterized by bowel habit changes and abdominal pain or discomfort that’s typically relieved by defecation.

Review7:50–9:00

Once you suspect a chronic bowel condition, you need to rule out other gastrointestinal conditions associated with similar clinical manifestations.
Do this by assessing the patient for red flag features and ordering labs, such as CBC, ESR, and CRP. If your patient presents with no red flag features and all labs are normal, suspect IBS.
Next, assess the Rome IV criteria. If the patient meets the criteria, diagnose IBS and start the initial management, which includes diet modifications, peppermint oil, tricyclic antidepressants, and gut-directed psychotherapy.
Finally, in individuals with diarrhea-predominant IBS, consider adding non-absorbed antibiotics and mixed opioid agonists-antagonists; and in individuals with the constipation-predominant type of IBS, consider chloride channels activators and guanylate cyclase activators.