Updated: 5/22/2018

Diarrhea

Topic
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Questions
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Evidence
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Snapshot
  • A 12-year-old boy is brought to the clinic for diarrhea and vomiting. He has no fever but complains of intermittent, cramping, and abdominal pain. They just returned from a family picnic, where about two hours ago the child ate potato salad. The mother reports other family members had become ill after the meal as well. 
Introduction
  • Definitions
    • stool with increased water content, volume, or frequency (> 250 grams/day of stool)
    • cause of 2.5 million deaths per year worldwide
    • in US, an estimated 48 million foodborne diarrheal illnesses occur annually
  • Classifications
    • timecourse
      • acute diarrhea lasts less than 14 days 
      • persistent diarrhea lasts 2 - 4 weeks
      • chronic diarrhea lasts > 4 weeks
    • types
      • invasive/inflammatory
      • non-invasive, non-inflammatory
        • osmotic diarrhea
        • secretory diarrhea
  • Differential diagnosis
    • depends on both time course and type of diarrhea 
    • infectious causes include:
      • viruses
      • bacteria
      • parasites
      • for full list of bugs causing diarrhea, see Microbiology topic 
    • noninfectious causes include:
      • medication adverse effects
      • acute abdominal processes
      • gastroenterologic disease
      • endocrine disease
  • General approach - 5 criteria to consider
    • does the patient really have diarrhea?
      • beware of fecal incontinence and impaction
    • rule out medications as a cause of diarrhea (drug-induced diarrhea)
    • distinguish acute from chronic diarrhea.
    • categorize the diarrhea as inflammatory, fatty, or watery.
    • consider factitious diarrhea.
Pathophysiology
  • Invasive, inflammatory diarrhea
    • history characterized by frequent, small-volume, bloody stools
    • may be accompanied by tenesmus, fever, or severe abdominal pain
    • fundamentally indicates disrupted and inflamed mucosa
    • causes
      • infectious processes (i.e., ShigellaCampylobacter jejuniEntamoeba histolytica, Salmonella enterensis, Entero-hemorrhagic E. coli, Clostridium difficile, cytomegalovirus, tuberculosis)
      • idiopathic inflammatory bowel disease (i.e., Crohn's, Ulcerative Colitis)
      • ischemic colitis
  • Fatty diarrhea
    • history of weight loss, greasy or bulky stools that are difficult to flush, and oil in the toilet bowl that requires a brush to remove
    • results from: 
      • fat malabsorption (inadequate mucosal transport)
        • i.e., celiac disease
      • fat maldigestion (defective hydrolysis of triglycerides)
        • pancreatic exocrine insufficiency (i.e., chronic pancreatitis) 
        • inadequate duodenal bile acid concentration (i.e., small intestinal bacterial overgrowth [SIBO] or cirrhosis)
  • Watery diarrhea
    • osmotic diarrhea 
      • loss of large volumes of diarrhea without inflammation of the enterocytes
      • osmotically active substance drawing hypotonic solution into the lumen
      • caused by ingestion of poorly absorbed ions or sugars
      • stool volume decreases with fasting
      • causes:
        • giardiasis
        • laxatives (e.g., magnesium containing products)
        • lactose intolerance (e.g., lactase deficiency)  
    • Secretory diarrhea
      • loss of large volumes of isotonic, watery diarrhea without inflammation of the enterocytes
      • caused by disruption of epithelial electrolyte transporters
      • stool volume continues unabated with fasting
      • causes
        • infection
          • enterotoxin production by ETECVibrio cholera
          • stimulates Cl- channel via ↑ cAMP
        • non-osmotic laxative use
          •  phenanthracene use can cause melanosis coli 
        • peptide-secreting endocrine tumors
          • carcinoid syndrome
          • increased production of 5-HT by tumor
Presentation
  • Symptoms
    • abdominal pain and cramping
    • frequent and profuse stools
Evaluation
  • In the vast majority of cases, work-up of acute diarrheal illness is not necessary, as most causes of diarrhea are self-lmited
  • Indications for increased severity requiring further evaluation:
    • profuse watery diarrhea with signs of hypovolemia
    • bloody diarrhea
    • temperature ≥ 38.5ºC (101.3ºF)
    • passage of ≥ 6 unformed stools per 24 hours or a duration of illness > 48 hours
    • severe abdominal pain
    • hospitalized patients or recent use of antibiotics
    • elderly (≥ 70 years of age) 
    • immunocompromised
    • systemic illness with diarrhea, especially in pregnant women 
  • Invasive diarrhea findings
    • stool culture
    • stool smear (+) for fecal leukocytes
    • CRP, ESR often elevated
    • low serum albumin level
  • Fatty diarrhea findings
    • Sudan stain - positive test indicates presence of steatorrhea
    • endoscopy or CT scan may be required to identify structural problem involving the small intestine or pancreas
  • Osmotic diarrhea findings
    • stool osmotic gap
      • > 50 consistent with osmotic type
    • stool smear (-) for fecal leukocytes
    • decreased stool pH
      • seen in lactase deficiency 
  • Secretory diarrhea findings
    • stool osmotic gap
      • < 50 excludes osmotic type
    • stool smear (-) for fecal leukocytes
    • look for ↑ 5-HIAA as a degradation product of 5-HT in carcinoid syndrome
      • if positive, further imaging will be required
    • microscopy
      • no abnormal morphology evidenced 
Treatment
  • Pharmacologic
    • oral rehydration therapy
      • components include water, glucose, sodium
      • in most diarrheal illnesses, intestinal glucose absorption via sodium-glucose cotransport remains intact
    • antidiarrheal agents
      • loperamide and bismuth salicylate
    • dietary modifications
      • boiled starches and cereals (e.g., potatoes, noodles, rice, wheat, oats) with salt 
      • avoidance of foods with high-fat content 
    • antimicrobials
      • consider empiric treatment for patients with severe illness (as described under Evaluation)
      • if organism identified, can tailor treatment, i.e.,:
        • TMP-SMX for severe E. coli diarrhea
        • metronidazole for G. lamblia
  • Prevention
    • consistent hand-hygiene techniques
    • prudent selection of food and drink while traveling
      • food that has been thoroughly cooked and served hot
      • fruits that the traveler peels just prior to eating
      • pasteurized dairy products
    • water sanitation
 
 

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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.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

QID: 101137
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Decreased stool osmolar gap

19%

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Decreased stool pH

62%

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3

Positive fecal smear for leukocytes

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4

Positive stool culture for Rotavirus

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Positive stool culture for T. whippelii

10%

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(M1.GI.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

QID: 101157
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Celiac disease

21%

(6/28)

2

Crohns disease

0%

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3

Tropical sprue

4%

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4

No GI disease

75%

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5

Ulcerative colitis

0%

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(M1.GI.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

QID: 101064
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Omeprazole

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Bismuth

8%

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Ranitidine

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4

Octreotide

11%

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5

Magnesium hydroxide

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