Internal Medicine Written Board Exam Sample Questions
2000
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QUESTION
83. A 36-year-old man is brought to the emergency department for evaluation. He was found on the street and is lethargic.  He presents with the following laboratory data

    Na 148 mEq/L  Arterial Blood Gases
    K  3.6 mEq/L  pH 7.29
    Cl 100 mEq/L  pCO2 28 torr
    HCO3   28 mEq/L   pO2  79 torr
    BUN    23 mg/dL
    Creatinine 1.3 mg/dL

Which of the following choices BEST describes the metabolic abnormalities?

    A) Metabolic acidosis, respiratory alkalosis, metabolic alkalosis
    B) Metabolic acidosis, respiratory acidosis, metabolic alkalosis
    C) Respiratory acidosis, metabolic alkalosis
    D) Respiratory alkalosis, metabolic alkalosis
    E) Metabolic acidosis, respiratory alkalosis

ANSWER
83. A Metabolic acidosis, respiratory alkalosis, metabolic alkalosis

This patient was found lethargic on the street. Looking at the electrolytes initially reveals an anion gap of 20. Therefore, the patient has an anion gap metabolic acidosis. Some possibilities include ketoacidosis (alcoholic or diabetic), toxin ingestion, (ethylene glycol, methanol or salicylates) or renal failure. We also see that the pH is 7.29 and the pCO2 is 28 which means that the primary disorder is metabolic acidosis and that the patient is attempting to compensate by inducing respiratory alkalosis (hyperventilation). If the pCO2 were normal (assumed to be 40), then the patient would simply have one disorder, namely metabolic acidosis. It is rare that an attempt at compensation does not occur, but this might happen in the setting of severe respiratory compromise or sedation resulting in relative hypoventilation. This patient additionally has a third disorder. This is determined by the fact that the G is 8. This number is arrived at by subtracting the normal anion gap from the patient's anion gap (20-12).

The G is then added to the serum bicarbonate concentration (28+8). This gives us 36. This is how we know that there is an underlying metabolic alkalosis.

1. Fauci A, Braunwald E, Isselbacher K, Wilson J, Martin J, Kasper D. Harrison's Principles of Internal Medicine. 14th Edition. McGraw-Hill, Inc. 1998:277-9

QUESTION
128. A 62-year-old man returns to the oncology clinic for routine follow-up. Eighteen months ago he was treated for medullary thyroid cancer with a thyroid resection and local lymph node resection. Since then, he has been maintained on levothyroxine. He reports that he is feeling well but at times is weak.

Examination reveals a healthy-appearing male with a blood pressure of 162/106 mmHg and heart rate 106 bpm.  His temperature is 101F and a slight tremor is noted. There is a large transverse scar on his neck but nodes are not palpable.  His lungs are clear and no carotid bruits are heard.  His heart rate is rapid but regular and a II/VI systolic ejection murmur is audible. Abdominal examination reveals diffuse mild tenderness, but no masses or organomegaly are noted.

Following the examination, the patient becomes diaphoretic and pale and is mildly orthostatic.  Laboratory data are significant for a sodium of 152 mEq/L and a calcium of 11.7 mEq/L.

The MOST appropriate evaluation at this point is

    A) Measurement of serum TSH
    B) Measurement of serum PTH
    C) Obtaining blood cultures
    D) Perform an abdominal CT to assess for abscess
    E) Collect a 24-hour urine for metanephrine

ANSWER
128. E To collect a 24-hour urine for metanephrines

Pheochromocytomas occurs with a frequency of 0.01%-0.1% of the hypertensive population.  In this condition, hyperplastic chromaffin cells of the adrenal medulla or sympathetic ganglion secrete catecholamines.  Clinical effects from these catecholamines can be labeled the five Ps:

  • Pressure (hypertension)
  • Pain (headache, chest pain, abdominal pain)
  • Perspiration (diaphoresis)
  • Palpitations
  • Pallor

These symptoms can occur spontaneously or can be precipitated by change in posture, anxiety, exercise, or abdominal pressure.

Pheochromocytomas can also be described with the rule of 10%:  10% are extra-adrenal, 10% occur in children, 10% are bilateral, 10% recur, and 10% are familial.

There is also an association with the multiple endocrine neoplasia (MEN) syndromes: type IIA includes medullary carcinoma of the thyroid, pheochromocytoma, and hyperparathyroidism (Sipple's syndrome); type IIB includes pheochromocytoma, medullary carcinoma of the thyroid, and neurofibromas.  The disease is diagnosed by measurement of serum or urine catecholamines, abdominal CT or MRI scans, or an octreotide or meta-iodo-benzyl-guanidine (MIBG) scan.

1. Young, WF. Pheochromocytoma: A brief management guide. Hospital Medicine. October 1993:67-79.

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