Updated: 10/13/2019

Diarrhea

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Snapshot
  • A 25-year-old man presents to his primary care physician for evaluation of diarrhea. He had recently gone to Mexico for spring break, where he stayed in a hostel with his friends. He spent a lot of time on the beach, swimming in caves, and hiking. He reports having onset of watery diarrhea about a week ago. He has not had any fevers, nausea, or vomiting. He does recall eating multiple rounds of raw oysters while in Mexico. He is found to be dehydrated, with poor skin turgor and dry mucous membrane.
Introduction
  • Overview
    • acute diarrhea is characterized by acute onset of >3 bowel movements/day lasting <14 days and is often caused by infection
    • persistent diarrhea lasts 2-4 weeks
    • chronic diarrhea lasts >4 weeks and is often caused by underlying conditions such as inflammatory bowel disease or fat malabsorption
  • Epidemiology
    • incidence
      • very common
      • rotavirus is most common cause of infectious diarrhea worldwide
        • vaccine available
      • acute diarrhea is the second cause of childhood mortality in the world
    • demographics
      • viral diarrhea is most common in children
        • especially rotavirus and adenovirus
  • Etiology
    • infections
      • viruses
      • bacteria
      • parasites
    • drug-induced
      • quinidine
      • colchicine
      • cytotoxic agents
      • chemotherapy
    • food allergies
    • toxic ingestions
    • autoimmun
    • small intestine bacterial overgrowth, often secondary to scleroderma or diabetes
  • Pathogenesis
    • types of diarrhea
      • exudative/inflammatory diarrhea
        • frequent, small-volume, and bloody stools
        • indicates disrupted and inflamed mucosa
        • etiologies
          • infectious (i.e., Shigella, Salmonella, E. coli, Campylobacter, amebiasis)
          • idiopathic inflammatory bowel disease (ulcerative colitis, Crohn disease)
          • ischemic colitis
      • fatty diarrhea
        • weight loss and greasy or bulky stools that float that are often chronic
        • etiologies
          • fat malabsorption
      • watery diarrhea
        • osmotic diarrhea
          • due to osmotic pull of water into the intestinal lumen
          • etiologies
            • giardiasis
            • laxatives
            • lactose intolerance
        • secretory diarrhea
          • due to active secretion of water
          • etiologies
            • infectious (i.e., enterotoxic E. coli, Vibrio)
            • carcinoid syndrome
            • gastrinoma
            • drugs (i.e., colchicine)
 
Infectious Bloody vs Watery Diarrhea
Bloody Diarrhea
Watery Diarrhea
  • Campylobacter
  • E. histolytica
  • Enterohemorrhagic E. coli
  • Enteroinvasive E. coli
  • Non-thypoidal Salmonella
  • Shigella
  • Y. enterocolitica
  • C. difficile
  • C. perfringens
  • Enterotoxigenic E. coli
  • Giardia
  • Cryptosporidium
  • V. cholerae
  • Rotavirus
  • Norovirus
  • Adenovirus
  • S. aureus
 
High Yield Risk Factors
Exposure Risk Factors
Associated Organisms
Daycare
  • Rotavirus, astrovirus, calicivirus, Campylobacter, Shigella, Giardia, Cryptosporidium
Food       
  • Dairy
  • Campylobacter, Salmonella
  • Eggs
  • Salmonella
  • Beef
  • E. coli
  • Poultry
  • Campylobacter, Salmonella
  • Pork
  • C. perfringens, Y. enterocolitica
  • Seafood
  • Astrovirus, Vibrio
  • Oysters
  • Calicivirus, Vibrio
  • Rice/pasta
  • Bacillus cereus
Water exposure 
  • Swimming pools
  • Shigella
  • Contaminated water with cysts
  • Giardia, E. histolytica, Cryptosporidium
Travel history 
  • "Traveler's" diarrhea
  • E. coli, Giardia, Salmonella, Shigella, Campylobacter
  • Camping/hiking
  • Giardia
Past medical history
  • Antibiotics/hospitalization
  • C. difficile, rotavirus
Pets  
  • Dog feces
  • Yersinia enterocolitica
  • Turtles/reptiles
  • Non-typhoidal Salmonella
  • Other animals/pets
  • Campylobacter
 
Presentation
  • Symptoms
    • common symptoms
      • dehydration
        • lethargy
        • feeling of thirst
      • diarrhea
        • foul-smelling along with stools that float
        • bloody diarrhea
        • watery diarrhea 
      • other enteric symptoms
        • nausea
        • vomiting
        • abdominal pain/cramping
  • Physical exam
    • inspection
      • dry mucous membranes
      • sunken eyes
      • poor skin turgor
      • delayed capillary refill
Studies
  • Acute diarrhea does not routinely require laboratory evaluation, unless clinical presentation includes
    • high fever
    • bloody diarrhea
    • severe abdominal pain
    • requires hospitalization
    • elderly
    • immunocompromised status
  • Serum labs
    • complete blood count
  • Stool studies
    • ova and parasite examination
    • C. difficile toxin
    • leukocyte presence suggests enteroinvasive infection
    • pH <5.5 usually indicates viral illness and can also indicate lactase deficiency
    • culture
    • enzyme immunoassay for rotavirus and adenovirus antigens
    • latex agglutination assay for rotavirus
Differential
  • Chronic diarrhea, which lasts 4 weeks or more, suggests other etiologies, such as fat malabsorption syndrome
 
Chronic Diarrhea
  • Malabsorption syndromes
  • Celiac disease
  • Lactose intolerance
  • Pancreatic insufficiency
  • Diabetic neuropathy
  • Inflammatory bowel disease
  • Crohn disease
  • Ulcerative colitis
  • Other gastrointestinal causes
  • Microscopic colitis
  • Irritable bowel syndrome
  • Endocrinological
  • Carcinoid
  • Gastrinoma
  • Drug-induced
  • Quinidine
  • Colchicine
  • Chemotherapy
  • Other
  • Severe combined immunodeficiency
  • Arsenic poisoning
  • Vitamin C toxicity
  • Vitamin B3 deficiency
 
Treatment
  • Medical
    • supportive care
      • modalities
        • oral rehydration
        • intravenous rehydration
        • electrolyte repletion
    • antibiotics
      • indication
        • for bacterial etiologies causing moderate or severe diarrhea and not responsive to rehydration
        • metronidazole or tinidazole for Giardia infections 
        • doxycycline for Vibrio cholera
        • oral vancomycin for C. difficile infection 
    • anti-motility agents
      • indication
        • not indicated for infectious diarrhea
      • modalities
        • loperamide
        • bismuth salicylate
Complications
  • Dehydration
 

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Questions (3)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
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(M1.GI.13.80) A 22-year-old female presents to your office with gas, abdominal distention, and explosive diarrhea. She normally enjoys eating cheese but has been experiencing these symptoms after eating it for the past few months. She has otherwise been entirely well except for a few days of nausea, diarrhea, and vomiting earlier in the year from which she recovered without treatment. Which of the following laboratory findings would you expect to find during workup of this patient? Review Topic | Tested Concept

QID: 101137
1

Decreased stool osmolar gap

15%

(10/66)

2

Decreased stool pH

70%

(46/66)

3

Positive fecal smear for leukocytes

3%

(2/66)

4

Positive stool culture for Rotavirus

5%

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5

Positive stool culture for T. whippelii

8%

(5/66)

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(M1.GI.13.100) A 30-year-old male visits you in the clinic complaining of chronic abdominal pain and diarrhea following milk intake. Gastrointestinal histology of this patient's condition is most similar to which of the following? Review Topic | Tested Concept

QID: 101157
1

Celiac disease

13%

(9/71)

2

Crohns disease

0%

(0/71)

3

Tropical sprue

3%

(2/71)

4

No GI disease

83%

(59/71)

5

Ulcerative colitis

0%

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(M1.GI.13.7) A 24-year-old patient presents to your gastroenterology practice on a referral from her primary care provider. The patient has been experiencing postprandial bloating and abdominal pain for one year. Symptoms occur following the ingestion of milk products. Which of the following drugs has a mechanism of action that is similar to the pathophysiology of this patient's disease? Review Topic | Tested Concept

QID: 101064
1

Omeprazole

3%

(7/201)

2

Bismuth

10%

(20/201)

3

Ranitidine

6%

(12/201)

4

Octreotide

10%

(21/201)

5

Magnesium hydroxide

67%

(134/201)

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