Laxative Abuse

Physiology

  • GI loss of bicarbonate -> hypovolemia with decreased sodium delivery to distal nephron
  • Serum bicarbonate is replaced with chloride -> hyperchloremia

Diagnosis

  • Serum Potassium: usually decreased
  • Urine AG: (urine Na+ + urine K+) – (urine Cl-)
    • Normal: -20 to -50 mEq/L
    • Negative: urine AG becomes more negative (usually >-50 mEq/L), due to the kidney increasing H+ excretion in the form of NH4+