Diarrhoea and vomiting

Introduction

Diarrhoea is defined as the passage of three or more loose or watery stools per day, while vomiting (emesis) is the forceful expulsion of gastric contents through the mouth. Together, they often indicate an acute gastrointestinal illness, most commonly infective gastroenteritis, but they can also signal systemic disease, drug toxicity, or surgical emergencies.

Both symptoms are important because they lead to fluid and electrolyte loss, which can cause dehydration, hypotension, shock, and even death if untreated.

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Pathophysiology

• Diarrhoea mechanisms:

  • Osmotic: Non-absorbed solutes draw water into bowel (e.g., lactose intolerance).

  • Secretory: Increased intestinal secretion (cholera, enterotoxins).

  • Inflammatory: Mucosal injury, exudation of pus/blood (dysentery, IBD).

  • Motility disorders: Rapid transit (IBS, hyperthyroidism).

• Vomiting mechanisms:

  • Coordinated by vomiting center in medulla.

  • Stimulated by vagal/enteric afferents (gastroenteritis), vestibular system (motion sickness), chemoreceptor trigger zone (toxins, drugs), higher CNS (emotions, raised ICP).

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Causes of Diarrhoea and Vomiting

1. Infective Causes (Most Common)

• Viral gastroenteritis: Rotavirus, norovirus, adenovirus.

• Bacterial gastroenteritis: Salmonella, Shigella, E. coli, Campylobacter, Vibrio cholerae.

• Parasitic: Giardia lamblia, Entamoeba histolytica.

• Food poisoning: Staphylococcus aureus, Bacillus cereus, Clostridium perfringens.

2. Non-Infective Gastrointestinal Causes

• Inflammatory bowel disease (Crohn’s, ulcerative colitis).

• Irritable bowel syndrome (functional).

• Coeliac disease, lactose intolerance.

• Peptic ulcer, gastritis.

• Bowel obstruction (vomiting predominant).

3. Medication-Induced

• Antibiotics (Clostridioides difficile colitis).

• Chemotherapy drugs.

• NSAIDs (gastric irritation).

• Laxative overuse.

• Digoxin, theophylline, opioids (nausea/vomiting).

4. Systemic and Metabolic

• Uremia, diabetic ketoacidosis (DKA).

• Thyrotoxicosis.

• Pregnancy (hyperemesis gravidarum).

• Sepsis.

5. Neurological

• Raised intracranial pressure.

• Vestibular disorders (labyrinthitis, Ménière’s).

• Migraine.

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Clinical Features

• Diarrhoea: Frequent loose stools, urgency, cramps, sometimes blood/mucus.

• Vomiting: Nausea, retching, dehydration.

• Associated:

  • Fever (infection).

  • Abdominal pain (inflammatory, obstruction).

  • Tenesmus, rectal bleeding (IBD, dysentery).

  • Weight loss (chronic disease, malignancy).

• Dehydration signs: Thirst, dry mouth, reduced urine, tachycardia, hypotension, sunken eyes, lethargy.

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Diagnostic Approach

1. History

• Duration (acute <14 days vs chronic).

• Travel, food exposure, sick contacts.

• Medication use.

• Systemic disease (diabetes, thyroid, renal).

• Alarm features: blood in stool, persistent vomiting, weight loss.

2. Examination

• Vitals: dehydration, shock.

• Abdominal exam: tenderness, distension, bowel sounds.

• Rectal exam (bleeding, masses).

• Neurological status if severe dehydration.

3. Investigations

• Basic labs: CBC, electrolytes, urea, creatinine, blood glucose.

• Stool analysis: Microscopy, culture, ova & parasites, C. difficile toxin.

• Blood cultures: If sepsis suspected.

• Imaging: Abdominal X-ray/CT if obstruction suspected.

• Pregnancy test (in women with vomiting).

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Management and Treatment

A. General Supportive Measures

• Rehydration is cornerstone (oral or IV depending on severity).

  • Oral rehydration solution (ORS): WHO formula (glucose, NaCl, KCl, citrate).

  • Adults: sip frequently, 200–400 mL after each loose stool.

  • Severe dehydration: IV fluids.

    • Normal saline or Ringer’s lactate: 1–2 L rapidly, then according to deficit.

• Diet: Resume light diet (rice, bananas, toast) as tolerated. Avoid dairy, caffeine, alcohol.

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B. Pharmacological Therapy

1. Antiemetics (for vomiting, if persistent)

• Ondansetron: 4–8 mg orally/IV every 8 hours.

• Metoclopramide: 10 mg orally/IV every 6–8 hours.

• Domperidone: 10 mg orally three times daily.

2. Antidiarrhoeal Agents

• For non-bloody, non-severe cases (not recommended in dysentery).

• Loperamide: 2–4 mg orally after first loose stool, then 2 mg after each episode (max 16 mg/day).

• Avoid in children <12 years and in bloody diarrhoea.

3. Antibiotics (only when indicated)

• Moderate–severe bacterial gastroenteritis, dysentery, traveler’s diarrhoea.

• Ciprofloxacin: 500 mg orally twice daily for 3 days.

• Azithromycin: 500 mg orally daily for 3 days (preferred in Asia due to resistance).

• Metronidazole: 500 mg orally three times daily for 7–10 days (Giardia, Entamoeba).

• Vancomycin 125 mg orally four times daily for 10 days (C. difficile infection).

4. Specific Treatments

• Cholera: Rehydration + Doxycycline 300 mg orally single dose.

• Hyperemesis gravidarum: IV fluids + Pyridoxine 25–50 mg orally three times daily, Ondansetron if refractory.

• DKA: IV insulin + fluids + electrolyte correction.

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C. Treating Underlying Causes

• Stop offending medications (antibiotics, NSAIDs).

• Manage chronic conditions (IBD, coeliac, thyroid).

• Surgery if obstruction or perforation.

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Complications

• Dehydration and electrolyte imbalance (hypokalemia, metabolic acidosis).

• Hypovolemic shock.

• Acute kidney injury.

• Sepsis.

• Malnutrition in chronic cases.

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Prognosis

• Acute gastroenteritis: Excellent prognosis, self-limiting in most.

• Chronic diarrhoea/vomiting: Depends on underlying cause (IBD, malignancy).

• Severe dehydration (children, elderly): Potentially fatal without prompt treatment.

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Patient Education

• Hand hygiene, safe food and water practices.

• Avoid raw/undercooked food when traveling.

• Early use of ORS at onset of diarrhoea.

• Avoid unnecessary antibiotics.

• Seek urgent care if diarrhoea/vomiting is associated with blood, persistent fever, severe abdominal pain, confusion, or reduced urine output.