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Free STEP2 Exam Braindumps (page: 5)

Page 4 of 185
PDF with 738 Questions

A 57-year-old man is on maintenance hemodialysis for chronic renal failure. Which of the following metabolic derangements can be anticipated?

  1. hypercalcemia
  2. hypophosphatemia
  3. osteomalacia
  4. vitamin D excess
  5. hypoparathyroidism

Answer(s): C

Explanation:

Chronic renal failure treated with hemodialysis results in predictable metabolic abnormalities. The kidneys fail to excrete phosphate, leading to hyperphosphatemia, and fail to synthesize 1,25(OH)2D3. Vitamin D deficiency causes impaired intestinal calcium absorption. Phosphate retention, defective intestinal absorption, and skeletal resistance to parathyroid hormone (PTH) all result in hypocalcemia. Hypocalcemia causes secondary hyperparathyroidism, and the excess PTH production worsens the hyperphosphatemia by increasing phosphorus release from bone. These derangements impair collagen synthesis and maturation, resulting in skeletal abnormalities collectively referred to as renal osteodystrophy.
Osteomalacia, osteosclerosis, and osteitis fibrosa cystica may all be seen.



A 25-year-old man was admitted to the intensive care unit with a severe head injury, with fracture of the base of the skull. Approximately 18 hours after the injury, he developed polyuria. Urine osmolality was 150 mOsm/L and serum osmolality was 350 mOsm/L. IV fluids were stopped, and 3 hours later, urine output and urine osmolality remained unchanged. Five units of vasopressin were intravenously administered. Urine osmolality increased to 300 mOsm/L. Which of the following is the most likely diagnosis?

  1. central diabetes insipidus
  2. nephrogenic diabetes insipidus
  3. water intoxication
  4. solute overload
  5. syndrome of inappropriate antidiuretic hormone secretion (SIADH)

Answer(s): A

Explanation:

Diabetes insipidus, a deficiency of pituitary antidiuretic hormone (ADH) (arginine vasopressin), causes water loss because of failure to facilitate reabsorption of water in the distal tubules and collecting ducts of the kidneys. In central diabetes insipidus, there is impaired production of vasopressin, and in nephrogenic diabetes insipidus, the distal renal tubules are refractory to vasopressin. In central diabetes insipidus, urine osmolality remains unchanged. If water intoxication were present, stopping IV fluids should have increased urine osmolality. With solute overload, serum osmolality would have been higher. In SIADH, urine osmolality is usually higher than serum osmolality.



A70-year-old man with a 60 pack-year smoking history presents with cough and weight loss. He describes recent diffuse darkening of his skin and his CXR shows a mass suspicious for lung cancer in the left hilum. His laboratory tests reveal hypokalemia. Which of the following is the most likely histology of his lung cancer?

  1. adenocarcinoma
  2. small cell
  3. squamous cell
  4. mesothelioma
  5. glioblastoma

Answer(s): B

Explanation:

Endocrine syndromes are seen in 12% of patients with lung cancer. Squamous cell carcinoma is associated with PTH-related peptide. Adrenocorticotrophic hormone (ACTH) and ADH secretion can be associated with small cell lung carcinoma. ACTH-secreting tumors are associated with darkening of the skin and hypokalemia.



A47-year-old man is postoperative day number 2 after an open cholecystectomy. He becomes short of breath and a medicine consultation is called to evaluate. Vital signs include a temperature of 100°F, pulse rate of 110/min, blood pressure (BP) of 110/60 mmHg, and respiratory rate of 24/min. Blood gas shows a pH of 7.52, carbon dioxide of 28, PO2 of 58, and calculated bicarbonate of 20. What is the primary acid- base disorder in this patient?

  1. metabolic acidosis
  2. respiratory acidosis
  3. metabolic alkalosis
  4. respiratory alkalosis
  5. metabolic and respiratory acidosis

Answer(s): D

Explanation:

This patient has an elevated pH (normal is 7.40) indicating alkalosis. Alow carbon dioxide level is consistent with a respiratory etiology of the alkalosis. This occurs when alveolar ventilation is increased relative to CO2 production. Causes may include fever, anxiety, pain, pulmonary, and/or neurologic conditions. In a metabolic alkalosis, a high bicarbonate is seen (a bicarbonate of 20 is low normal).






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