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Dehydration

Medicine > Renal

Differential Diagnosis Schema 🧠

Gastrointestinal Causes

  • Gastroenteritis: Diarrhea and vomiting leading to fluid loss and dehydration
  • Inflammatory bowel disease (e.g., Crohn’s, ulcerative colitis): Chronic diarrhea leading to gradual dehydration
  • Malabsorption syndromes: Chronic diarrhea and malabsorption leading to dehydration and electrolyte imbalance
  • Bowel obstruction: Vomiting, inability to tolerate oral intake, and fluid sequestration in the bowel leading to dehydration
  • Pyloric stenosis: Projectile vomiting in infants leading to significant dehydration
  • Pancreatitis: Vomiting, poor oral intake, and fluid shifts leading to dehydration
  • Clostridium difficile infection: Severe diarrhea, often after antibiotic use, leading to dehydration
  • Cholera: Profuse watery diarrhea leading to rapid dehydration, often in areas with poor sanitation

Renal Causes

  • Diabetes insipidus: Polyuria and inability to concentrate urine leading to dehydration
  • Acute kidney injury: Reduced urine output (oliguria) or fluid loss from diuretics leading to dehydration
  • Chronic kidney disease: Reduced ability to concentrate urine leading to chronic dehydration
  • Nephrotic syndrome: Proteinuria, hypoalbuminemia, and fluid loss into tissues leading to intravascular dehydration
  • Diuretic use: Excessive diuresis leading to fluid and electrolyte imbalance and dehydration
  • Post-obstructive diuresis: Polyuria following relief of urinary obstruction leading to dehydration
  • Hypercalcemia: Polyuria and polydipsia leading to dehydration, often due to hyperparathyroidism or malignancy
  • Hyperglycemia: Osmotic diuresis in poorly controlled diabetes leading to dehydration

Respiratory Causes

  • Pneumonia: Fever, increased respiratory rate, and poor oral intake leading to dehydration, particularly in elderly or young patients
  • Bronchiolitis: In infants, increased work of breathing and poor oral intake can lead to dehydration
  • Severe asthma exacerbation: Increased respiratory effort and insensible fluid loss through hyperventilation leading to dehydration
  • Tuberculosis: Chronic cough, fever, night sweats, and weight loss leading to dehydration over time
  • Chronic obstructive pulmonary disease (COPD) exacerbation: Poor oral intake and increased respiratory effort leading to dehydration
  • Cystic fibrosis: Recurrent respiratory infections and malabsorption leading to chronic dehydration
  • Fever of any cause: Increased insensible fluid loss due to sweating and tachypnea leading to dehydration

Endocrine Causes

  • Diabetes mellitus: Osmotic diuresis in poorly controlled diabetes leading to dehydration
  • Hyperthyroidism: Increased metabolic rate leading to insensible fluid loss and dehydration
  • Adrenal insufficiency: Hyponatremia, hyperkalemia, and hypovolemia leading to dehydration, particularly in Addisonian crisis
  • Diabetic ketoacidosis (DKA): Polyuria, vomiting, and dehydration in poorly controlled type 1 diabetes
  • Hyperosmolar hyperglycemic state (HHS): Severe dehydration, hyperglycemia, and altered mental status in type 2 diabetes
  • Pheochromocytoma: Excessive sweating and tachycardia leading to insensible fluid loss and dehydration

Other Causes

  • Heat stroke: Prolonged exposure to high temperatures leading to excessive sweating, fluid loss, and dehydration
  • Burns: Significant fluid loss through damaged skin leading to dehydration and hypovolemic shock
  • Hemorrhage: Significant blood loss leading to hypovolemia and dehydration
  • Poor oral intake: Due to any cause (e.g., dementia, dysphagia, or social factors) leading to gradual dehydration
  • Excessive exercise: Prolonged physical activity without adequate fluid replacement leading to dehydration
  • Medications: Diuretics, laxatives, and other medications leading to fluid loss and dehydration
  • Psychogenic polydipsia: Excessive fluid intake followed by rapid excretion leading to dehydration
  • Geriatric dehydration: Common in elderly patients due to reduced thirst perception, poor oral intake, and medications
  • Pediatric dehydration: Common in infants and young children due to higher fluid requirements and greater susceptibility to fluid loss
  • Alcohol intoxication: Diuretic effect of alcohol leading to dehydration, particularly after binge drinking

Key Points in History 🥼

Symptoms of Dehydration

  • Thirst: Early and common symptom, often the first sign of dehydration.
  • Dry mouth and mucous membranes: Indicative of moderate to severe dehydration.
  • Reduced urine output: Oliguria or dark concentrated urine suggests significant fluid loss.
  • Dizziness or lightheadedness: Particularly on standing, suggestive of orthostatic hypotension due to dehydration.
  • Fatigue or lethargy: Common in moderate to severe dehydration, particularly in elderly or chronically ill patients.
  • Confusion or altered mental state: Seen in severe dehydration, particularly in elderly or very young patients.
  • Sunken eyes: Particularly in children and elderly, suggestive of severe dehydration.
  • Tachycardia: Compensatory response to hypovolemia in dehydration.
  • Hypotension: Seen in severe dehydration, often with tachycardia and poor perfusion.
  • Capillary refill time >2 seconds: Indicates poor perfusion and significant dehydration.
  • Decreased skin turgor: Skin “tenting” on pinch test, particularly in elderly or children.
  • Weight loss: Acute weight loss indicating fluid loss, particularly in children.
  • Headache: Common in moderate to severe dehydration.
  • Nausea or vomiting: Can be both a cause and a symptom of dehydration.
  • Cold extremities: Indicative of hypovolemia and shock in severe dehydration.
  • Fever: Can cause dehydration and is also a symptom in some underlying causes.
  • Muscle cramps: Common in moderate to severe dehydration due to electrolyte imbalance.
  • Seizures: Rare but severe symptom of electrolyte imbalance due to dehydration.

Background

  • Past medical history: Conditions such as diabetes, renal disease, heart failure, or chronic diarrhea that predispose to dehydration
  • Drug history: Use of diuretics, laxatives, or medications that may affect fluid balance
  • Family history: Genetic predisposition to conditions like diabetes insipidus or cystic fibrosis
  • Social history: Alcohol use, living conditions, and access to water or healthcare, particularly in the elderly or isolated individuals
  • Dietary history: Inadequate fluid intake, excessive salt intake, or dietary habits that may contribute to dehydration
  • Travel history: Recent travel to areas with high temperatures, poor sanitation, or risk of infectious diarrhea
  • Environmental factors: Exposure to high temperatures, physical exertion, or lack of access to fluids
  • Occupational history: Jobs requiring prolonged physical activity or exposure to heat without adequate fluid intake
  • Recent surgery or illness: Postoperative fluid loss or reduced intake due to pain, nausea, or vomiting
  • Psychosocial stressors: Conditions like depression, anxiety, or dementia that may lead to neglect of fluid intake
  • Exercise habits: Prolonged or intense physical activity without adequate fluid replacement
  • Infant history: In infants, assess feeding habits, number of wet nappies, and episodes of vomiting or diarrhea
  • Elderly considerations: In elderly patients, assess for factors like reduced thirst perception, cognitive impairment, and social isolation

Possible Investigations 🌡️

Bedside Tests

  • Capillary refill time: Prolonged refill time suggests hypovolemia and dehydration
  • Urinalysis: Assess specific gravity, ketones, and glucose, which may indicate dehydration, diabetes, or starvation ketosis
  • Blood pressure: Postural hypotension suggests significant dehydration
  • Pulse rate: Tachycardia can be a sign of hypovolemia due to dehydration
  • Temperature: Fever can both cause and result from dehydration; hypothermia may occur in severe dehydration
  • Skin turgor test: Reduced skin elasticity suggests dehydration, particularly in children and the elderly
  • Weight measurement: Acute weight loss indicates fluid loss, particularly in children
  • Fluid balance chart: Monitoring intake and output provides a practical assessment of hydration status
  • Blood glucose monitoring: Particularly important in diabetic patients to rule out hyperglycemia or hypoglycemia
  • Consciousness level: Assessing for confusion or decreased level of consciousness can indicate severe dehydration
  • Oxygen saturation: Hypoxia may be present in severe dehydration or associated conditions like pneumonia
  • Blood gas analysis: May show metabolic acidosis in cases of severe dehydration or associated conditions like DKA
  • Chest auscultation: May reveal crackles in cases of pneumonia or respiratory distress associated with dehydration
  • Electrolyte assessment: May reveal imbalances like hypernatremia, hyponatremia, or hyperkalemia in dehydration
  • ECG: To assess for arrhythmias, particularly in cases of severe electrolyte imbalance
  • Oral mucosa examination: Dry mucous membranes are a common sign of dehydration

Laboratory and Imaging Investigations

  • Full blood count (FBC): To assess for infection or anemia, both of which may be associated with dehydration
  • Urea and electrolytes (U&E): To assess for renal function and electrolyte imbalances
  • Serum osmolality: Elevated in dehydration, particularly with hypernatremia
  • Creatinine: Elevated levels may indicate renal impairment due to dehydration
  • Liver function tests (LFTs): To assess for liver disease or dehydration-related liver dysfunction
  • Arterial blood gas (ABG): May show metabolic acidosis or alkalosis depending on the underlying cause of dehydration
  • Blood glucose: To assess for hyperglycemia in diabetic patients or hypoglycemia in others
  • Urine sodium and osmolality: To differentiate between different causes of dehydration, particularly in renal and endocrine disorders
  • Chest X-ray: To assess for pneumonia, pulmonary edema, or other respiratory causes contributing to dehydration
  • Abdominal ultrasound: To assess for renal pathology, bowel obstruction, or other intra-abdominal causes of dehydration
  • ECG: To assess for arrhythmias, which may result from electrolyte imbalances associated with dehydration
  • Serum calcium and magnesium: To assess for imbalances that may contribute to dehydration symptoms such as muscle cramps
  • Serum lactate: Elevated in severe dehydration or associated conditions like sepsis
  • Thyroid function tests: To assess for hyperthyroidism as a potential cause of increased fluid loss
  • CT or MRI: To assess for central causes of altered mental status in severe dehydration or associated conditions
  • Urine culture: If urinary tract infection is suspected as a cause of fever and dehydration
  • Serum ketones: Elevated in DKA, a critical cause of dehydration in diabetic patients
  • CSF analysis: In cases of suspected meningitis or encephalitis presenting with dehydration and altered mental status
  • Serum bicarbonate: Low in cases of metabolic acidosis associated with dehydration

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Renal