Differential Diagnosis for New Onset Polyuria in a Two Year Old Child with Severe Acute Malnutrition

• Single Most Likely Diagnosis
  • Diabetes Insipidus (DI): This condition, characterized by the inability to regulate fluids in the body due to a problem with the antidiuretic hormone (ADH), can lead to polyuria. In a child with severe acute malnutrition, the body's stress response and potential dehydration could exacerbate or unveil underlying DI.
• Other Likely Diagnoses
  • Diabetes Mellitus: Although less common in this age group, especially without a clear family history, the stress of severe malnutrition could potentially trigger an autoimmune response leading to type 1 diabetes, presenting with polyuria among other symptoms.
  • Renal Tubular Acidosis: This condition affects the kidney's ability to regulate acid levels, leading to various metabolic imbalances. It could present with polyuria and is a consideration in a malnourished child due to potential renal impairment.
  • Nephrogenic Diabetes Insipidus: Similar to central DI but caused by renal insensitivity to ADH, this could be a result of or exacerbated by severe dehydration and electrolyte imbalances seen in severe acute malnutrition.
• Do Not Miss Diagnoses
  • Posterior Pituitary Apoplexy or Other Central Nervous System Lesions: Although rare, any condition affecting the pituitary gland could lead to central DI. Given the severity of the presentation, missing such a diagnosis could have significant implications.
  • Hypercalcemia: Can cause nephrogenic DI. In a malnourished child, hypercalcemia could result from various factors including excessive intake or mobilization from bones due to lack of dietary calcium.
  • Sepsis: Can lead to acute kidney injury (AKI), which might present with polyuria during the recovery phase. Sepsis is a critical condition that requires immediate attention, especially in a severely malnourished child with a compromised immune system.
• Rare Diagnoses
  • Fanconi Syndrome: A disorder of the proximal renal tubules, leading to impaired reabsorption of glucose, amino acids, and phosphate. It could present with polyuria among other symptoms but is less common.
  • Barter Syndrome or Gitelman Syndrome: These are rare genetic disorders affecting the kidneys' ability to reabsorb potassium, leading to various electrolyte imbalances and potentially polyuria.
  • Psychogenic Polydipsia: Although rare in a two-year-old, it's a condition where excessive fluid intake leads to polyuria. In the context of severe malnutrition, it might be less likely but should be considered if the child has access to large amounts of water.