The correct answer is D. The clinical picture is consistent with Crohn disease (CD). Non-bloody diarrhea, abdominal pain and cramps, malaise, and low-grade fever are the most common, but rather nonspecific, presenting symptoms. CD affects the terminal ileum most frequently, so that tenderness and a mass can often be detected on palpation in the lower right quadrant of the abdomen. The most characteristic signs of CD include sharp demarcation of affected segments from adjacent noninvolved loops and presence of non-necrotizing granulomas in biopsies. Strictures resulting in bowel obstruction may necessitate surgical resection, as in this case.
Carcinoma (choice A) is highly unlikely, considering the clinical picture, location of lesion (small bowel cancer is rare), and young age of the patient.
Celiac disease (choice B) is a chronic diarrheal disease that is characterized by intestinal malabsorption and precipitated by indigestion of gluten-containing foods. The disease also presents with non-bloody diarrhea, cramps, and abdominal distension due to fluid- and gas-filled intestinal loops. Distinguishing features on small bowel series are flocculation of barium, small bowel dilatation, and flattening of the normal mucosal fold pattern. Occasionally, ulceration and strictures may occur.
Chronic appendicitis (choice C) is a rather controversial entity. Repeated bouts of acute appendicitis, especially when incompletely controlled with antibiotic therapy, may rarely result in periappendiceal and pericolic adhesions.
Pseudomembranous colitis (choice E) is due to the toxins produced by Clostridium difficile. This condition develops as a complication of broad-spectrum antibiotic treatment, particularly in hospitalized patients. It affects the colon (not the ileum) and manifests with greenish, foul-smelling diarrhea. Endoscopic and pathologic examination reveal the characteristic yellow-green plaques adherent to the mucosa.
Ulcerative colitis (UC) (choice F) shares many clinical and pathologic features of CD, so that an "umbrella" designation of inflammatory bowel disease (IBD) is used to refer to both conditions when a specific diagnosis is not yet made. Features not consistent with UC (thus favoring CD) include involvement of the ileum (which is exceptional in UC), sharp demarcation of the affected bowel segment, and the presence of granulomas on histologic examination.
