A 67-year-old man comes to the emergency department due to abdominal cramps, diarrhea, and fever that started 3 days ago. The patient initially had 3 or 4 stools per day for 2 days but, today, had 7 watery stools; the stools have not had gross blood or mucus or black discoloration. The patient has also had generalized weakness and malaise. Two weeks ago, he was treated with oral antibiotics for acute cellulitis. Since then, the patient's appetite has decreased, and he has had mild bloating. He has no history of recent travel, unusual foods, or sick contacts with similar symptoms. Other medical conditions include type 2 diabetes mellitus, hypertension, and hyperlipidemia. Temperature is 38.7 C (101.7 F) , blood pressure is 110/70 mm Hg, and pulse is 95/min. Physical examination shows moderate abdominal tenderness. The cellulitis has resolved. Leukocytes are 26,000/mm³, serum creatinine is 1.9 mg/dL (increased from 1.2 mg/dL 2 months ago) , and serum albumin is 2.9 g/dL. The patient does not want to be admitted to the hospital and would like to be treated as an outpatient.
The patient is at most risk for developing which of the following complications?

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Explanation: 11ec2b69_bf8f_42cd_8f63_9b8cf6974d62_MD0005_00 This patient who recently completed a course of antibiotics for cellulitis now has profuse watery diarrhea accompanied by abdominal bloating, fever, and leukocytosis. This presentation is most concerning for Clostridioides difficileinfection (CDI). Profuse watery diarrhea (≥3 loose stools/24 hr) is the hallmark symptom of CDI, which is suspected when major risk factors (eg, recent antibiotic use, advanced age [>65]) for CDI are present. Other common features include abdominal pain and leukocytosis; fever is present in approximately 15% of patients. CDI is typically classified as nonsevere, severe (leukocytes >15,000/mm³ and/or serum creatinine >1.5 mg/dL), or fulminant (eg, severe CDI with hypotension, ileus, or megacolon). This patient has markers of severe disease (eg, leukocytes 26,000/mm³, creatinine 1.9 mg/dL) with hypoalbuminemia, which can occur in CDI due to inflammatory protein-losing enteropathy. He is at risk, especially without appropriate treatment, for developing fulminant disease, in which severe colonic dilation (ie, megacolon) and/or necrosis can occur, leading to perforation. (Choices A and C) Infection with Shiga toxin-producing Escherichia coli (STEC) can cause fever, abdominal pain, and, initially, watery diarrhea that may convert to bloody diarrhea. In addition, STEC may be complicated by hemolytic uremic syndrome (characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury). However, STEC rarely causes fever >38.5 C (101.3 F), and stools typically become bloody within 1-3 days of diarrhea onset. (Choice B) Demyelination of axons, as seen in Guillain-Barré syndrome, can occur as a complication of Campylobacter gastroenteritis. Campylobacter infection can cause fever, abdominal pain, and profuse watery diarrhea; however, the diarrhea also typically contains mucus and/or blood. Leukocytosis may be present but is typically mild (not 26,000/mm³). (Choice E) Infection with Shigella can present with high fever, abdominal pain, and diarrhea. Although mild disease may cause only watery diarrhea, most cases (and especially those with numerous diarrheal episodes per day) have mucoid and/or bloody diarrhea. In addition, tenesmus (not present in this patient) is common due to preferential involvement of the rectosigmoid region. When present, Shigella may be complicated by seizures; however, this occurs almost exclusively in children age <15. Educational objective: Clostridioides difficile infection (CDI) is characterized by profuse watery diarrhea and should be suspected when major risk factors (eg, recent antibiotic use, age >65) are present. Severe CDI is characterized by leukocytosis (>15,000/mm³) and elevated serum creatinine (≥1.5 mg/dL) and can progress to fulminant disease, which may be complicated by colonic dilation, necrosis, and perforation. References: ACG clinical guidelines: prevention, diagnosis, and treatment of Clostridioides difficile infections. (http://www.ncbi.nlm.nih.gov/pubmed/34003176) Clinical practice guideline by the Infectious Diseases Society of America (IDSA) and Society for Healthcare Epidemiology of America (SHEA): 2021 focused update guidelines on management of Clostridioides difficile infection in adults. (http://www.ncbi.nlm.nih.gov/pubmed/34164674)

A 67-Year-Old Man Comes to the Emergency Department Due to Abdominal