A 32-Year-Old Man Is Being Evaluated Due to Several Weeks

question 41

Multiple Choice

A 32-year-old man is being evaluated due to several weeks of watery diarrhea.  He has also had intermittent, crampy abdominal pain and has lost 7 kg (15.4 lb) during this period.  The patient has a history of HIV and was hospitalized 6 months ago for Pneumocystis pneumonia.  On physical examination, the patient is afebrile, and the abdomen is soft and nontender with no organomegaly.  Stool tests for leukocytes and occult blood are negative.  Endoscopy is performed, and mucosal biopsy shows an inflammatory infiltrate in the lamina propria and pathogens lining the epithelium, as shown in the exhibit.
  The organisms have a cystic appearance on modified acid-fast staining.  Which of the following is the most likely cause of this patient's condition?

• A)Clostridium difficile
• B)Cryptosporidium parvum
• C)Entamoeba histolytica
• D)Enteropathogenic Escherichia coli
• E)Giardia lamblia
• F)Mycobacterium avium complex
• G)Salmonella enteritidis

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Definitions:

ADH

Antidiuretic hormone, a peptide hormone produced by the pituitary gland that regulates water absorption in the kidneys.

Insulin

Protein hormone secreted from the pancreas that increases the uptake of glucose and amino acids by most tissues.

Medullary Interstitial Fluid

The fluid located in the interstitial space of the kidney medulla, playing a crucial role in the concentration of urine.

Vasa Recta

The vasa recta are a series of straight capillaries in the kidney that play a crucial role in the process of urine concentration.