What is the workup for a patient presenting with diarrhea?

Workup for Diarrhea

The initial workup for a patient with diarrhea should include a thorough clinical and epidemiological history, physical examination focused on signs of dehydration, and targeted laboratory testing based on presentation severity and suspected etiology. 1

Initial Assessment

History

• Timing and onset: Abrupt vs. gradual onset, duration of symptoms 1
• Stool characteristics: Watery, bloody, mucous, purulent, greasy 1
• Frequency and volume of bowel movements 1
• Associated symptoms:
  • Fever, tenesmus, abdominal pain, cramps
  • Nausea, vomiting, headache, myalgias
  • Signs of dehydration (thirst, decreased urination, lethargy) 1

Epidemiological Risk Factors

• Travel to developing areas
• Day-care center attendance/employment
• Consumption of unsafe foods (raw meats, eggs, shellfish, unpasteurized products)
• Swimming in or drinking untreated water
• Animal contact (farms, petting zoos, reptiles, pets with diarrhea)
• Exposure to ill persons
• Recent medications (antibiotics, antacids, anti-motility agents)
• Underlying medical conditions (immunosuppression, prior gastrectomy)
• Sexual practices (receptive anal intercourse, oral-anal contact)
• Occupation as food-handler or caregiver 1

Physical Examination

• Vital signs (fever, tachycardia, orthostatic changes)
• Signs of volume depletion:
  • Dry mucous membranes
  • Decreased skin turgor
  • Absent jugular venous pulsations
• Abdominal examination for tenderness
• Mental status assessment 1

Laboratory Evaluation

Initial Testing (Based on Severity)

• Mild, uncomplicated diarrhea: Limited testing needed
• Moderate to severe diarrhea:
  • Stool analysis for blood, leukocytes, ova and parasites
  • Stool culture for bacterial pathogens
  • Clostridium difficile testing (especially with recent antibiotic use)
  • Complete blood count
  • Electrolyte panel 1, 2

Extended Workup (For Persistent Cases)

• Adenovirus, astrovirus, CMV, rotavirus testing
• Parasitic studies
• Lactose breath test
• Consider alternative causes (treatment-associated, paraneoplastic) 1

Management Algorithm

1. Assess Hydration Status

• Evaluate for signs of dehydration (vital signs, mucous membranes, skin turgor)
• Determine appropriate rehydration approach 2

2. Rehydration

• Mild to moderate dehydration:

  • Oral rehydration solution (ORS) with 75-90 mEq/L sodium, 20 mEq/L potassium, 65-80 mEq/L chloride, 10 mEq/L citrate, and 75-111 mmol/L glucose 2
  • Drink 8-10 large glasses of clear liquids daily 1

• Severe dehydration:

  • Intravenous fluids and electrolyte replacement 1

3. Dietary Modifications

• Stop lactose-containing products, alcohol, and high-osmolar supplements
• Follow BRAT diet (bread, rice, applesauce, toast) 1, 2
• Resume age-appropriate diet during or immediately after rehydration 2

4. Pharmacological Treatment

• Mild to moderate diarrhea (Grade 1-2):

  • Loperamide: Initial dose 4 mg followed by 2 mg every 4 hours or after each unformed stool (maximum 16 mg/day) 1, 3
  • Avoid in children under 2 years, bloody diarrhea, or suspected inflammatory diarrhea 2, 3

• Severe diarrhea (Grade 3-4) or persistent symptoms:

  • Octreotide (100-150 μg SC TID or IV 25-50 μg/hr) 1
  • Consider antibiotics if infectious etiology suspected 1

Special Considerations

Infectious Diarrhea

• Antibiotics only if evidence of bacterial infection, immunocompromised status, or severe illness with systemic symptoms 2
• Appropriate antibiotic selection based on suspected pathogen 2

Cancer Treatment-Related Diarrhea

• Hold cytotoxic chemotherapy until symptoms resolve for grade 2 or higher diarrhea
• Consider dose reduction after resolution 1
• For severe cases, administer octreotide and intravenous fluids 1

When to Refer/Hospitalize

• No improvement within 48 hours
• Severe dehydration
• Bloody diarrhea with fever
• Immunocompromised patients
• Severe abdominal pain
• Elderly patients with significant comorbidities 2, 4

Pitfalls to Avoid

• Delaying rehydration therapy in severe cases
• Using antimotility agents in suspected inflammatory or infectious diarrhea
• Failing to consider C. difficile in patients with recent antibiotic use
• Overlooking underlying conditions in persistent diarrhea
• Repeating testing for the same pathogen (may lead to false positives) 1, 2