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Project - USMLE Step 3 > Symptom To Diagnosis - Acute Diarrhea > Flashcards

Symptom To Diagnosis - Acute Diarrhea Flashcards

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USMLE® Step 1 flashcards
1
Q

The DDX of acute diarrhea uses the pivotal point of presenting symptoms to organize diagnoses into 3 categories:

A
  1. Non infectious.
  2. Gastroenteritis.
  3. Infectious colitis.
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2
Q

Non infectious diarrhea:

A

Lack of constitutional symptoms.

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3
Q

Infectious diarrhea (gastroenteritis):

A

Presents with large volume (often watery) stool, constitutional symptoms, nausea and vomiting, and often abdominal cramps can be categorized as gastroenteritis.

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4
Q

Infectious colitis:

A

Presents with fever, tenesmus, and dysentery (stools with blood and mucus).
Many organisms can cause gastroenteritis and inflammatory diarrhea.

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5
Q

Non infectious diarrhea - General causes:

A
  1. Medications and other ingestible substances (some with osmotic effect).
  2. Mg-containing medications.
  3. Malabsorption.
  4. Medications causing diarrhea through non osmotic means.
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6
Q

Non infectious diarrhea - Medications and other ingestible substances (some with osmotic effect):

A
  1. Sorbitol (gum, mints, pill fillers).
  2. Mannitol.
  3. Fructose (fruits, soft drinks).
  4. Fiber (bran, fruits, vegetables).
  5. Lactulose.
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7
Q

Non infectious diarrhea - Mg-containing medications:

A
  1. Nutritional supplements.
  2. Antacids.
  3. Laxatives.
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8
Q

Non infectious diarrhea - Malabsorption:

A
  1. Lactulose intolerance.

2. Pancreatitis.

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9
Q

Non infectious diarrhea - Medications causing diarrhea through non osmotic means:

A
  1. Metformin.
  2. Antibiotics.
  3. Colchicine.
  4. Digoxin.
  5. SSRIs.
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10
Q

Infectious diarrhea (gastroenteritis) - General causes:

A
  1. Viral.
  2. Bacterial.
  3. Toxin-mediated.
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11
Q

Infectious diarrhea (gastroenteritis) - Viral causes:

A

Most common.

  1. Caliciviruses (Norovirus).
  2. Rotovirus.
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12
Q

Infectious diarrhea (gastroenteritis) - Bacterial (commonly food-borne):

A
  1. V.cholera.
  2. E.coli.
  3. Shigella.
  4. Salmonella.
  5. Campylobacter.
  6. Yersinia enterocolitica.
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13
Q

Infectious diarrhea (gastroenteritis): Toxin-mediated:

A
  1. S.aureus.
  2. C.perfringens.
  3. B.cereus.
  4. E.coli.
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14
Q

Infectious diarrhea (inflammatory colitis) - General causes:

A
  1. Bacterial.

2. Antibiotic-associated.

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15
Q

Infectious diarrhea (inflammatory colitis): Bacterial causes:

A
  1. Shigella.
  2. E.coli.
  3. Campylobacter.
  4. Salmonella.
  5. Y.enterocolitica.
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16
Q

Infectious diarrhea (inflammatory colitis): Antibiotic-associated:

A
  1. C.difficile.
  2. Klebsiella oxytoca.
  3. Non-C. difficile -related.
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17
Q

Acute diarrhea - Norovirus - Textbook presentation:

A
  1. Acute vomiting is usually the presenting symptom.
  2. Mild diarrhea begins after the vomiting.
  3. Mild abdominal cramping is common.
  4. Low-grade fever and dehydration are usually present.
  5. All symptoms resolve completely by 3 days.
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18
Q

Calicivirus (Norovirus, Sapovirus) account for what percentage of adult non bacterial gastroenteritis?

A

80%.

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19
Q

Norovirus infection most commonly occurs in?

A

Winter.

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20
Q

Norovirus - Transmission and attack rate?

A

Transmission may be person-to-person or food-borne.

50% attack rate.

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21
Q

MCC of food-borne infection:

A

Norovirus.

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22
Q

Norovirus - Incubation period:

A

1-2 days.

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23
Q

Home-made solution for patients with more significant volume depletion?

A

Mix 1 L of water with:
1/2 tea-spoon of salt.
1/4 teaspoon of baking soda.
8 teaspoons of sugar.

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24
Q

Antidiarrheals (loperamide) are safe and effective for patients with or without dysentery?

A

Without dysentery.

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25
Q

Using antidiarrheals in a patient with dysentery is not safe because they can:

A
  1. Cause prolonged fever.
  2. Cause toxic megacolon and perforation.
  3. Possibly increase the risk of HUS in patients with shiga toxin-producing E.coli (STEC).
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26
Q

Diet in adult non bacterial diarrhea:

A
  1. BRAT diet (banana, rice, applesauce, toast) is often recommended.
  2. Avoid dairy products.
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27
Q

S.aureus, C.perfringens, and B.cereus account for what percentage of food-borne infections?

A

<1% (!). (Viral causes account for about 60%).

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28
Q

MC bacterial and parasitic food-borne infections:

A
  1. Salmonella (38%).
  2. Campylobacter (33%).
  3. Shigella (16%).
  4. Cryptosporidium (5%).
  5. STEC (5%).
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29
Q

Gastroenteritis caused by Salmonella species:

A
  1. Subacute with nausea, fever, and diarrhea.
  2. Fever and nausea often resolve over 1-2 days while diarrhea persists for 5-7 days.
  3. . Patients usually have watery diarrhea with 6-8 bowel movements each day.
  4. Dysentery is possible.
  5. Bacteria remain in the stool for 4-5 weeks.
  6. Salmonella gastroenteritis may cause higher fevers than viral or preformed toxin disease.
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30
Q

Salmonella species cause 3 major types of disease:

A
  1. Diarrheal illnesses.
  2. Bacteremia with the potential for focal infectious complications.
  3. Typhoid fever.
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31
Q

Typhoid fever:

A

A systemic illness characterized by fever and abdominal pain caused by Salmonella typhi.

32
Q

Typhoid fever is distinct from gastroenteritis, which is caused by?

A

Non typhi Salmonella species.

33
Q

Typhoid fever - A diarrheal illness?

A

Although not generally considered a diarrheal illness, some patients may have diarrhea as a predominant symptom.

34
Q

Typhoid fever should be considered in the DDX of?

A

A traveler with a febrile illness.

35
Q

Incidence of Salmonella diarrhea in 2006 was?

A

14.8/100.000.

36
Q

Salmonella is transmitted by?

A
  1. Food (eggs, poultry).
  2. Fecal-oral contact with infected patients (patients shed bacteria for WEEKS after infection.
  3. Animals (reptiles most classically).
37
Q

Gold standard for diagnosing Salmonella gastroenteritis:

A

Stool cultures.

38
Q

Prolonged bacterial shedding after gastroenteritis - Especially common with?

A

Salmonella and Campylobacter.

39
Q

Lactose intolerance - Textbook presentation:

A

Commonly presents as chronic symptoms in a person of susceptible ethnic background.

40
Q

Populations more likely to have LOW levels of lactase activity are:

A
  1. Middle East and Mediterranean.
  2. East Asia.
  3. Africa.
  4. Native American.
41
Q

Definitive tests for lactose intolerance:

A
  1. Lactose intolerance test.
  2. Lactose breath hydrogen test.
    for patients in whom the diagnosis is likely but not clear historically.
42
Q

2 distinct types of antibiotic associated diarrhea:

A
  1. Diarrhea related to an enteric pathogen (primarily C.difficile).
  2. Diarrhea related to other effects of antibiotics.
43
Q

Antibiotics most commonly responsible for both types of diarrhea are:

A
  1. Clindamycin.
  2. Cephalosporins.
  3. Ampicillin.
  4. Amoxicillin.
  5. Amoxicillin-clavulanate.
44
Q

C.difficile accounts for …-…% of antibiotic-associated diarrhea.

A

10-20%.

45
Q

Risk factors for C.difficile colitis:

A
  1. Advanced age.
  2. Hospitalization.
  3. Exposure to antibiotics.
46
Q

C.difficile has been reported up to … after a course of antibiotics.

A

6 months.

47
Q

Recent reports about C.difficile:

A
  1. Greater incidence of community-acquired C.difficile.
  2. C.difficile related to the use of PPIs.
  3. C.difficile genetic changes dictating toxin production.
48
Q

Klebsiella oxytoca:

A

Newly recognized cytotoxin-producing bacteria capable of causing antibiotic-associated hemorrhagic colitis.
Much less common than C.difficile.

49
Q

Antibiotic-associated diarrhea NOT related to C.difficile:

A

Mild disease. Causes:

  1. Change in intestinal flora.
  2. Non antimicrobial effect of antibiotics such as the promotility effects of erythromycin.
  3. Enteric infections other than C.difficile.
50
Q

C.difficile colitis - Relapse:

A

20-25%.

51
Q

MCC of parasitic diarrhea in the USA:

A

Giardia.

52
Q

Giardia - Common symptoms:

A 
96% --> Diarrhea.
62% --> Weight loss.
61% --> Abdominal cramps.
57% --> Greasy stools.
Belching, flatulence, and foul smelling stools are commonly reported.
Fever is UNCOMMON.
53
Q

Parasitic diarrhea especially in immunocompromised?

A
  1. Cryptosporidium (stool antigen).
  2. Cyclospora cayetanensis (acid-fast).
  3. Isospora belli (acid-fast).
54
Q

Organisms most commonly cause bloody diarrhea:

A
  1. Shigella species.
  2. Campylobacter species.
  3. E.coli.
    Salmonella, Y.enterocolitica and C.difficile also may cause bloody diarrhea.
55
Q

Non infectious causes of bloody diarrhea:

A
  1. UC.

2. Ischemic colitis.

56
Q

Campylobacter infection - Textbook presentation:

A
  1. Presenting symptoms are usually diarrhea and abdominal pain.
  2. Diarrhea is often profuse and watery.
  3. Pain may be severe, often mimicking appendicitis or other abdominal disease that may require surgery.
  4. Fever usually resolves over the first 2 days.
  5. Diarrhea and abdominal pain may last 4-6 days.
57
Q

Incidence of Campylobacter diarrhea:

A

12.7 /100.000 (2006).

58
Q

In 1 recent study of patients arriving at emergency department with bloody diarrhea, the breakdown of diagnoses were:

A
  1. 3% –> Shigella.
  2. 2% –> Campylobacter.
  3. 2% –> Salmonella.
  4. 6% –> Shiga-toxin producing E.coli.
  5. 6% –> Other cause.
59
Q

Campylobacter infection - Common aspects of presentation are:

A
  1. Constitutional symptoms before GI disease.

2. Bloody diarrhea beginning AFTER 2-3 days of watery diarrhea.

60
Q

Campylobacter infection - Rare late complications:

A
  1. Reactive arthritis.

2. Guillain-Barre.

61
Q

Campylobacter infection - Bacteria commonly remain in the stool for?

A

4-5 WEEKS - Reinfection might occur.

62
Q

Campylobacter infection - Although stool cultures are most likely to be negative, they can be useful in some circumstances:

A
  1. Campylobacter and Shigella infections clearly benefit from treatment.
  2. Inappropriate treatment of Salmonella (treating mild or moderate non-typhi infection) is NOT helpful and may lead to prolonged carriage.
  3. Culture results can be very helpful from a public health standpoint.
63
Q

Campylobacter infection - The ONLY way to distinguish organisms:

A

Stool cultures.

64
Q

Campylobacter infection - When to send stool cultures?

3 questions must be considered:

A
  1. Is there a clinical suspicion for a specific disease that requires treatment?
  2. Does the patient have an underlying disease that makes treatment more necessary?
  3. Are there public health reasons that a diagnosis needs to be made?
65
Q

Campylobacter infection - Is there a reason NOT to culture?

A

Stool cultures and ova and parasite exams of hospitalized patients are particularly unrevealing.

66
Q

Bottom line about when to take stool cultures?

A

Patients with more severe clinical presentations, including high fever, abdominal pain, and dysentery, should always have stool cultures taken.

67
Q

Shigella infection - Textbook presentation:

A
  1. Often begins with fever and constitutional symptoms.
  2. Diarrhea is initially watery and may become bloody.
  3. Can be very frequent.
  4. Tenesmus is often prominent.
68
Q

Shigella infection - Incidence:

A

6.1/100.000 (2006).

69
Q

Shigella infection - Evidence based diagnosis:

A
  1. STOOL CULTURE IS THE GOLD STANDARD.
  2. Sensitivity of band count >1% = 85%.
  3. Sensitivity of fecal leukocytes is at least 70%.
70
Q

Shigella infection clearly benefits from treatment - Antibiotic of choice:

A

Oral ciprofloxacin.

71
Q

Shiga Toxin-producing E.coli (STEC) O157:H7 infection - Textbook presentation:

A
  1. Diarrhea + abdominal pain.
  2. Pain is often worse in the RLQ.
  3. Bloody diarrhea is very common, while nausea, vomiting, and fever are NOT.
72
Q

STEC incidence:

A

1.3/100.000 (2006).

73
Q

STEC is associated with?

A

HUS:

  1. Microangiopathic hemolytic anemia.
  2. Thrombocytopenia.
  3. Acute renal failure.
74
Q

Patients infected with STEC are significantly more likely than patients infected with other pathogens to:

A
  1. Report bloody diarrhea.
  2. Provide visibly bloody specimens.
  3. NOT report fever.
  4. Have abdominal tenderness.
  5. Have a WBC >10.000.
75
Q

If an organism is isolated from a patient with bloody diarrhea, it is most likely to be?

A

Shigella or Campylobacter.

76
Q

Although the presence of diarrhea is actually defined by stool weight, how is it more useful to define acute diarrhea?

A

Clinically –> >3 bowel movements of a looser consistency.

Acute diarrhea develops over a period of 1-2 days and lasts for less than 4 weeks.

Project - USMLE Step 3 (82 decks)

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