Irritable bowel syndrome: Clinical sciences

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. 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. 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.
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.

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.