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Difficulty: EasySomatic Symptom and Eating Disorders

A 19-year-old female is evaluated in the emergency department for severe generalized weakness and muscle cramps. Her roommate reports that the patient is heavily preoccupied with her body image and frequently goes to the bathroom immediately after meals. Vital signs show a blood pressure of 100/60 mm Hg and a heart rate of 98/min. Physical examination reveals bilateral parotid gland enlargement, dry mucous membranes, and calluses on the dorsum of her right hand. Which of the following sets of laboratory abnormalities is most likely to be found in this patient?

  1. Hypokalemia, hypochloremia, and metabolic alkalosisAnswer
  2. B
    Hypokalemia, hyperchloremia, and metabolic acidosis
  3. C
    Hyperkalemia, hypochloremia, and metabolic alkalosis
  4. D
    Hyperkalemia, hyperchloremia, and metabolic acidosis
  5. E
    Normal potassium, normal chloride, and respiratory alkalosis

Answer

Hypokalemia, hypochloremia, and metabolic alkalosis
The correct answer accurately reflects the pathophysiology of repeated self-induced vomiting. The patient's clinical presentation, including Russell sign (calluses on the knuckles) and parotid gland enlargement, strongly indicates purging via vomiting. Emesis results in the loss of gastric hydrochloric acid (HCl), causing hypochloremia and primary metabolic alkalosis. Additionally, the resulting volume depletion stimulates the renin-angiotensin-aldosterone system, which increases urinary potassium excretion in order to reabsorb sodium, leading to significant hypokalemia.

Step-by-Step Solution

1
Identify the patient's underlying condition based on the clinical presentation.
The patient has signs of self-induced vomiting (Russell sign, parotid enlargement) suggesting an eating disorder with purging behavior.
Parotid gland hypertrophy and calluses on the dorsum of the hand (Russell sign) are classic physical findings of frequent self-induced vomiting.
2
Determine the physiological consequences of frequent self-induced vomiting.
Vomiting causes a significant loss of fluid, hydrogen ions, and chloride ions from the stomach.
Gastric fluid is rich in hydrochloric acid (HCl).
3
Predict the resulting electrolyte and acid-base disturbances.
The loss of HCl leads to hypochloremia and metabolic alkalosis. Subsequent volume depletion activates the renin-angiotensin-aldosterone system, leading to renal potassium wasting and hypokalemia.
Aldosterone promotes sodium reabsorption at the expense of potassium and hydrogen ion excretion, exacerbating both the hypokalemia and metabolic alkalosis.

Key Concept

Patients with eating disorders who engage in self-induced vomiting characteristically develop a hypokalemic, hypochloremic metabolic alkalosis.
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Topics

Somatic Symptom and Eating Disorders

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