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Update your knowledge with MKSAP 14 Q&A


MKSAP 14 will help you update your knowledge in the field of internal medicine for improved patient care, support your clinical decisions in practice, and assess your medical knowledge with 1,200 multiple-choice questions. For more information on how to order MKSAP 14 click here


A 72-year-old woman is evaluated in the hospital for nausea and vomiting. The episode began 3 days ago with the onset on non-bloody watery diarrhea and abdominal cramping that progressed to worsening abdominal pain with distention, fever, mild chills, and then nausea and vomiting. The patient had community-acquired pneumonia 3 weeks ago, for which she was treated in the hospital and then discharged on therapy with oral levofloxacin. Her medical history also includes osteoporosis and hypertension, and her medications include alendronate and hydrochlorothiazide.

The temperature is 37.4 C (99.0 F), pulse rate is 110/min with orthostatic changes, and blood pressure is 95/60 mm Hg. Physical examination reveals dry mucous membranes, a distended abdomen with absent bowel sounds and tympany to percussion that is diffusely tender to palpation; there is pitting edema of the lower extremities.

Laboratory abnormalities include a leukocyte count of 27,100/L (27 109/L), a serum albumin concentration of 1.9 g/dL (19 g/L), and many stool leukocytes. Abdominal imaging shows dilated small bowel loops suggestive of ileus, and thickening of the wall of the entire colon without megacolon.

Which of the following is the most likely diagnosis?

A. Acute diverticulitis
B. Clostridium difficile infection
C. Ischemic colitis
D. Ulcerative colitis

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Answer: B, Clostridium difficile infection

Objective: Diagnose Clostridium difficile infection

Critique: Clostridium difficile infection is likely in this elderly patient because of the non-bloody diarrhea, colonic wall thickening (probable pseudomembranes) on abdominal imaging, and her recent hospitalization and antibiotic therapy. A new epidemic strain of C. difficile known as BI/NAP1 appears to cause more frequent, severe, and persistent infections; the virulence of this new strain is likely due to multiple factors, including significantly higher toxin production. Clinical manifestations of this more severe infection include high rates of toxic megacolon, leukemoid reaction, severe hypoalbuminemia, shock, and increased rates of colectomy and death. Most patients are elderly and the inducing agent is often a quinolone or cephalosporin. There is no readily available test to detect the BI/NAP1 strain and management is the same for the less virulent strains, although early detection and rapid treatment are emphasized by experts.

Patients with uncomplicated acute diverticulitis present with left lower abdominal pain and fever. Leukocytosis is present, but hypoalbuminemia and hypotension are unusual. If a complication is suspected, a CT scan of the abdomen and pelvis may demonstrate localized inflammation or abscess formation. Elderly patients with cardiovascular disease are most frequently affected by ischemic colitis. Symptoms include left lower quadrant abdominal pain and bloody diarrhea, which are often self-limited. The finding of patchy segmental ulcerations on colonoscopy supports the diagnosis; biopsies can help substantiate the diagnosis if needed. Ulcerative colitis typically involves the rectum and extends proximally with contiguous inflammation that is generally limited to the mucosa of the colon and rectum. Patients usually present with bloody diarrhea associated with rectal discomfort, fecal urgency, and cramps. Fever, tachycardia, dehydration, and significant abdominal tenderness or rebound indicates more severe disease. Hypoactive bowel sounds or abdominal distention suggests perforation or megacolon. While ulcerative colitis may initially manifest at an older age, the recent hospitalization and antibiotic exposure in this case makes C. difficile infection more likely.

Key Point: A new strain of Clostridium difficile known as BI/NAP1 tends to cause more frequent, severe, and refractory infections than previous strains.


Bartlett JG. Narrative review: The new epidemic of Clostridium difficile-associated enteric disease. Ann Intern Med. 2006;145:758-64. [PMID: 17116920]
Borgmann S, Kist M, Jakobiak T, et al. Increased number of Clostridium difficile infections and prevalence of Clostridium difficile PCR ribotype 001 in southern Germany. Euro Surveill. 2008 Dec 4;13(49). pii: 19057. [PMID: 19081002]

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