4. MTB Step 3 - Diarrhea

Question 1

INFECTIOUS DIARRHEA

What is the most important feature of Infectious Diarrhea on presentation?

Answer 1

The Presence of Blood. Blood means the presence of invasive bacterial pathogens

Question 2

INFECTIOUS DIARRHEA

What are (8) Invasive Bacterial Pathogens that cause Infectious (bloody) Diarrhea?

Answer 2

• Campylobacter: This is the most common cause of food poisoning. It can be associated with Guillain-Barre syndrome and reactive arthritis.
• Salmonella: This is transmitted by chickens and eggs.
• Vibrio parahaemolyticus: This is associated with seafood.
• E. coli: This can have several variants, some of which are associated with blood.
  
  • E. coli 0157:H7 is most commonly associated with hemolytic uremic syndrome (via effects of verotoxin). Look for undercooked beef in the history. Do not give platelet transfusions or antibiotics, which can make it worse.
• Vibrio vulnificus: Look for shellfish (oysters, clams) in a person with liver disease and skin lesions.
• Shigella: Secretes Shiga toxin. This bacteria is also associated with reactive arthritis.
• Yersinia: Rodents (rarely other mammals) are the natural reservoir of this bacteria. Transmission is via vegetables, milk-derived products, and meat (case may describe pork) that is contaminated with infected urine or feces.
• Amebic: Perform 3-stool ova and parasite examinations or serologic testing. Treat with metronidazole. May be associated with liver abscesses.

Question 3

INFECTIOUS DIARRHEA

1. What is the Best INITIAL Test for Infectious (bloody) Diarrhea?
2. What is the Most ACCURATE Test for Infectious (bloody) Diarrhea?

Answer 3

• Best initial test: Fecal leukocytes
• Most accurate test: Stool culture

Question 4

INFECTIOUS DIARRHEA

What are the treatments for both Mild Infectious Diarrhea and Severe Infectious Diarrhea?

Answer 4

• Mild Disease: This will resolve on its own, and the patient should be hydrated only.
• Severe Disease: Fluoroquinolones, such as Ciprofloxacin, are the best initial therapy. Severe disease is defined as the presence of the following:
  
  • Blood
  • Fever
  • Abdominal pain
  • Hypotension and tachycardia

Question 5

NONBLOODY DIARRHEA

What are (6) causes of Nonbloody Diarrhea?

Answer 5

• Viruses: Rotavirus, norovirus (also called “Norwalk virus”)
• Giardia: Look for camping/hiking and men who have sex with men. Stool ELISA antigen is > 90 percent sensitive and specific and is more accurate than 3-stool ova and parasite exams. Look for bloating, flatus, and signs of steatorrhea. Treat with metronidazole or tinidazole.
• Staphylococcus aureus: Presents with vomiting in addition to diarrhea. It will resolve spontaneously.
• Bacillus cereus: Associated with refried Chinese rice and vomiting. It resolves spontaneously.
• Cryptosporidiosis: Look for an HIV-positive patient with < 100 CD4 cells. Diagnose with a modified acid-fast stain. Use antiretroviral medications to raise the CD4 count. Paromomycin is only partially effective. Nitazoxanide is used effectively.
• Scombroid: This is histamine fish poisoning. This has the fastest onset of diarrhea; within 10 minutes of eating an infected tuna, mackerel, or mahi-mahi, the patient has vomiting, diarrhea, wheezing, and flushing. Treat with antihistamines, such as diphenhydramine.

Question 6

CLOSTRIDIUM DIFFICILE

What is the cause of C. difficile Diarrhea?

Answer 6

• C. difficile Diarrhea develops several days to weeks after the use of antibiotics.
• Although clindamycin is the most common cause, antibiotic-associated diarrhea can be caused by any antibiotic.
• Recently fluoroquinolones have also come to be associated with Clostridium difficile. There can be both blood and fecal leukocytes with C. difficile colitis.
• PPIs increase the risk of C. diff in hospitalized patients.

Question 7

CLOSTRIDIUM DIFFICILE

What are the Best INITIAL and Most ACCURATE Diagnostics Tests for C. difficile Diarrhea?

Answer 7

• Best initial test: Stool toxin assay
• Most accurate test: Stool PCR

Question 8

CLOSTRIDIUM DIFFICILE

What is the Best INITIAL and Further treatments for C. difficile Diarrhea?

Answer 8

• Best initial therapy: Vancomycin (PO)
• If antibiotic-associated diarrhea resolves with vancomycin and then recurs later, the patient should be re-treated with Vancomycin.
• Severe disease can be treated with Metronidazole + Vancomycin in combination.
  
  • Fidaxomicin (PO) is an alternative to vancomycin in severe, recurrent cases.
  • Fidaxomicin (PO) does not have more efficacy than metronidazole on the first episode.
  • Fidaxomicin (PO) is used if there is no response to metronidazole and with severe disease.
  • IV vancomycin is not useful.
• Surgery is used in severe disease, such as toxic megacolon, elevated lactate, leukocytosis, and elevated creatinine.
• “Bezlotoxumab” is the answer when the question asks, “Which of the following prevents recurrence?”

Question 9

CHRONIC DIARRHEA

What is the Definition of Chronic Diarrhea?

Answer 9

The production of Loose Stools with or without increased frequency for ≥ 4 weeks.

Question 10

CHRONIC DIARRHEA

What is the Most Common Cause of Chronic Diarrhea?

Answer 10

Lactose Intolerance

Question 11

CHRONIC DIARRHEA

What is the best way to both Diagnose and Treat Lactose Intolerance in one step?

Answer 11

Remove ALL Milk and milk-related products from the diet except yogurt.

A lactose-intolerance test may also be performed. Stool osmolarity is increased.

Question 12

CHRONIC DIARRHEA

What is the presentation of Carcinoid Syndrome?

Answer 12

Flushing

and

Episodes of Hypotension

Question 13

CHRONIC DIARRHEA

1. What is the Diagnostic Test finding in Carcinoid Syndrome?
2. What is the Treatment for Carcinoid Syndrome?

Answer 13

Diagnose with a Urinary 5-HIAA level

Treat with the Somatostatin Analog Octreotide