A 27-year-old woman presents to the clinic with intermittent abdominal discomfort for the past year. The pain is associated with bloating and improves after bowel movements. She reports alternating episodes of constipation and diarrhea. She denies weight loss, nocturnal symptoms, hematochezia. Past medical history is negative, and she does not take any medications. She has no family history of colorectal cancer. Temperature is 36.7°C (98.1°F), blood pressure is 114/72 mm Hg, pulse is 72/min, and respiratory rate is 14/min. Physical examination is unremarkable. Complete blood count, metabolic panel, liver function tests, and inflammatory markers are normal.
Which of the following is the most likely diagnosis?
The correct answer is:
C: Irritable bowel syndrome.
This patient has recurrent abdominal pain associated with changes in bowel habits and relief with defecation. The absence of alarm features such as weight loss, anemia, gastrointestinal bleeding, or nocturnal symptoms supports a diagnosis of irritable bowel syndreom(IBS). IBS is a functional gastrointestinal disorder and does not cause structural abnormalities or systemic inflammation.
Answer choice A: Celiac disease, is incorrect.
Celiac disease can cause chronic diarrhea and bloating. However, patients often have evidence of malabsorption such as weight loss, iron deficiency anemia, or nutritional deficiencies.
Answer choice B: Crohn disease, is incorrect.
Crohn disease typically causes inflammatory symptoms such as weight loss, anemia, elevated inflammatory markers, or perianal disease. None are present here.
Answer choice D: Microscopic colitis, is incorrect.
Microscopic colitis usually presents in older adults with chronic watery diarrhea rather than alternating bowel habits.
Answer choice E: Ulcerative colitis, is incorrect.
Ulcerative colitis commonly causes bloody diarrhea and evidence of inflammation. This patient’s symptoms are more consistent with a functional disorder.
Key Learning Point
Irritable bowel syndrome is characterized by recurrent abdominal pain associated with altered bowel habits in the absence of alarm features or objective evidence of inflammation.
