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Zorluk: OrtaSomatic Symptom and Eating Disorders

A 20-year-old female college student is brought to the student health clinic by her roommate due to severe generalized weakness, muscle cramps, and dizziness upon standing. The patient admits to having an intense fear of gaining weight and reveals that she has been using over-the-counter pills to "stay thin", though she refuses to specify the exact medication. Her body mass index is 22 kg/m222 \text{ kg/m}^2. Vital signs show a blood pressure of 105/65 mm Hg supine and 85/50 mm Hg standing. Pulse is 92/min supine and 118/min standing. Physical examination is unremarkable, with no dental erosions or calluses on her hands. Laboratory studies show:

Sodium: 139 mEq/L139 \text{ mEq/L}
Potassium: 2.6 mEq/L2.6 \text{ mEq/L}
Chloride: 115 mEq/L115 \text{ mEq/L}
Bicarbonate: 14 mEq/L14 \text{ mEq/L}

Arterial blood gas on room air:
pH: 7.287.28
pCO2pCO_2: 30 mm Hg30 \text{ mm Hg}

Which of the following inappropriate compensatory behaviors is most likely responsible for this patient's laboratory findings?

  1. Frequent use of bisacodylCevap
  2. B
    Self-induced vomiting
  3. C
    Misuse of furosemide
  4. D
    Severe caloric restriction
  5. E
    Ingestion of levothyroxine

Cevap

Frequent use of bisacodyl
The correct answer is the frequent use of bisacodyl. This patient presents with orthostatic hypotension, severe hypokalemia, and a normal anion gap metabolic acidosis. In the context of a patient with an eating disorder, these findings are highly specific for laxative abuse (such as bisacodyl or senna). Laxatives cause rapid gastrointestinal transit and profound loss of potassium-rich and bicarbonate-rich fluids in the stool. The loss of bicarbonate directly causes a non-anion gap metabolic acidosis, and the loss of potassium leads to severe hypokalemia.

Adım Adım Çözüm

1
Identify the primary acid-base disturbance.
The pH is 7.287.28 (acidemia) and bicarbonate is 14 mEq/L14 \text{ mEq/L} (low), indicating a primary metabolic acidosis.
To determine the primary etiology of the electrolyte derangement.
2
Calculate the anion gap and expected respiratory compensation.
The anion gap is 139−(115+14)=10 mEq/L139 - (115 + 14) = 10 \text{ mEq/L}, which is normal. Expected pCO2pCO_2 by Winter's formula is 1.5(14)+8±2=29±2 mm Hg1.5(14) + 8 \pm 2 = 29 \pm 2 \text{ mm Hg}, matching the measured 30 mm Hg30 \text{ mm Hg}.
To differentiate between normal anion gap and high anion gap metabolic acidosis, and to confirm there is no mixed disorder.
3
Correlate the laboratory findings with eating disorder behaviors.
The combination of severe hypokalemia, volume depletion, and a normal anion gap metabolic acidosis points to lower gastrointestinal loss of bicarbonate and potassium.
To identify the specific mechanism (laxative abuse) among the differential diagnoses for inappropriate compensatory weight-loss behaviors.

Anahtar Kavram

Patients with eating disorders who abuse laxatives typically present with volume depletion, severe hypokalemia, and a normal anion gap metabolic acidosis due to gastrointestinal loss of bicarbonate and potassium.
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Somatic Symptom and Eating Disorders

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