A 19-year-old man comes to the office due to a change in bowel habits. Six months ago, the patient began having loose, watery stools with increased frequency to approximately 5 times daily. In addition, he has had crampy, intermittent abdominal pain that usually improves after defecation. No nausea, vomiting, melena, fevers, night sweats, or weight loss has occurred. The patient vacationed in South America 12 months ago. He does not use tobacco or alcohol. Temperature is 37.4 C (99.3 F), blood pressure is 138/87 mm Hg, pulse is 75/min, and respirations are 12/min. The patient appears comfortable and is not in acute distress. There is no conjunctival pallor, scleral icterus, or palpable lymphadenopathy. Cardiopulmonary examination is unremarkable. The abdomen is nontender and nondistended. Rectal examination reveals scant blood in the stool but no hemorrhoids or fissures. Laboratory results are as follows:
| Complete blood count | |
| Hemoglobin | 11.7 g/dL |
| Platelets | 435,000/mm3 |
| Leukocytes | 7,000/mm3 |
| Immunologic and rheumatologic studies | |
| C-reactive protein | 12.1 mg/L (<3 mg/L) |
Stool studies are negative for ova and parasites as well as Clostridioides (formerly Clostridium) difficile. Which of the following is the best next step in management?
Inflammatory bowel disease subtype characteristics | ||
Crohn disease | Ulcerative colitis | |
Involvement |
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Microscopy |
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Clinical |
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Intestinal |
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RLQ = right lower quadrant. | ||
This patient's presentation is most consistent with inflammatory bowel disease (IBD), which encompasses 2 disorders: Crohn disease (CD) and ulcerative colitis (UC). Both CD and UC present with chronic diarrhea, abdominal pain, anemia, and elevated inflammatory markers (eg, C-reactive protein, erythrocyte sedimentation rate). Although not universally true, pain is predominant in CD, whereas hematochezia is more common in UC. Severe manifestations of CD include fistulas, strictures, and abscesses; uncontrolled UC can lead to toxic megacolon.
Diagnosing IBD and distinguishing between CD and UC requires colonoscopy with biopsies. CD is characterized grossly by a cobblestone appearance, skip lesions (eg, areas of normal-appearing bowel between inflamed segments), and deep serpiginous ulcers. On the other hand, UC demonstrates continuous, shallow ulcerations and pseudopolyps. On histology, chronic inflammation in CD extends beyond the submucosa and is often transmural; noncaseating granulomas may be present. In UC, inflammation is usually limited to the mucosa, although it occasionally extends into the submucosa.
(Choice A) Fecal calprotectin, a stool marker for inflammatory diarrhea, is typically elevated in patients with IBD. However, it is not specific for IBD and is not used to make the initial diagnosis of IBD; it is sometimes used in patients with established CD who have symptoms of a flare. An elevated fecal calprotectin would not distinguish between CD and UC.
(Choices B and G) Tissue transglutaminase is a marker of celiac disease, whereas loperamide and the low FODMAP (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, And Polyols) diet represent initial steps in the management of irritable bowel syndrome (IBS). Neither celiac disease nor IBS presents with an elevated C-reactive protein or bloody stool on rectal examination.
(Choice C) A barium enema can be used to characterize colonic inflammation; however, it is less accurate than a colonoscopy for diagnosing IBD.
(Choice E) CT findings (eg, fat stranding, intestinal wall thickening) in IBD are identical to those of other types of colitis (eg, infectious, ischemic) and are therefore too nonspecific to be used for initial diagnosis.
(Choice F) Azithromycin is used to treat travelers' diarrhea, which causes abdominal cramps and self-limited watery or bloody diarrhea. This patient's travel history is too remote to be related to his clinical presentation; travelers' diarrhea typically presents within 2 weeks of initial infection.
Educational objective:
Both Crohn disease and ulcerative colitis present with chronic diarrhea, abdominal pain, anemia, and elevated inflammatory markers. Colonoscopy with biopsies is the test of choice for diagnosis because it can distinguish between characteristic findings of Crohn disease (eg, cobblestone appearance, skip lesions, deep ulcerations, transmural inflammation, granulomas) and those of ulcerative colitis (eg, continuous, shallow ulcerations limited to the mucosa/submucosa, pseudopolyps).