USMLE USMLE Certifications USMLE-STEP-2 Questions & Answers

• Question 721:

  A 54-year-old man presents to the emergency department complaining of epigastric discomfort, which began while he was walking his dog after dinner about one-half hour earlier. He has not received medical care for several years. On examination, he is moderately obese and in obvious discomfort and seems restless. His BP is 160/98 mmHg, and his examination is otherwise unremarkable. His ECG is seen in Figure below:

  

  Which of the following is the most likely diagnosis?

  A. gastroesophageal reflux

  B. costochondritis

  C. pericarditis

  D. inferior wall myocardial infarction

  E. anterolateral myocardial infarction

  Correct Answer: D

  This ECG reveals ST-segment elevation in II, III, and AVF, indicating acute injury of the inferior wall of the myocardium. Inferior wall ischemia can be perceived as pain in the epigastric area. Anterolateral myocardial infarction would show loss of R-wave progression in V4 through V6. Pericarditis would show diffuse ST segment elevation in limb and precordial leads. Although his symptoms could suggest gastroesophageal reflux, this ECG shows this a cardiac event. Costochondritis is not present by examination. When ST segment elevation is present, a patient should be considered a candidate for reperfusion therapy or primary percutaneous intervention (PCI) such as angioplasty and stenting. If no contraindications are present and PCI is unavaliable, thrombolytic therapy should ideally be initiated within 30 minutes, right in the emergency department. The goal of both thrombolysis and PCI is prompt restoration of coronary arterial patency. Thrombolytic therapy can reduce the risk of in- hospital death by up to 50% when administered within the first hour of symptoms, so time is of the essence. Arranging for a bed may waste time for limiting infarct size. The ECG would obviously preclude the other two options: immediate trial of antacid or reassurance and arranging outpatient follow-up.

• Question 722:

  A20-year-old female presents to the office complaining that her right eye has been itchy and watery. The patient reports that the onset was abrupt. The patient is noted to be afebrile with normal vital signs. Examination discloses a red eye with watery discharge. Minimal preauricular adenopathy is also found on examination. Tonometry is normal. Profuse tearing is noted. Which of the following is the most likely diagnosis?

  

  A. viral conjunctivitis

  B. bacterial conjunctivitis

  C. foreign body reaction

  D. allergic conjunctivitis

  E. acute open-angle glaucoma

  Correct Answer: A

  Viral (follicular) conjunctivitis most often presents with minimal discharge and itching as compared to the moderate-to-profuse discharge of bacterial conjunctivitis. While mild pain and photophobia may be noted in viral, bacterial, fungal, and allergic conjunctivitis, preauricular adenopathy is common in viral and fungal conjunctivitis only. Allergic conjunctivitis presents with minimal discharge and marked itching. The patient's young age and normal eye pressure (tonometry) helps to rule out glaucoma.

• Question 723:

  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?

  A. adenocarcinoma

  B. small cell

  C. squamous cell

  D. mesothelioma E. glioblastoma

  Correct Answer: B

  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.

• Question 724:

  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?

  A. metabolic acidosis

  B. respiratory acidosis

  C. metabolic alkalosis

  D. respiratory alkalosis

  E. metabolic and respiratory acidosis

  Correct Answer: D

  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).

• Question 725:

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

  A. hypercalcemia

  B. hypophosphatemia

  C. osteomalacia

  D. vitamin D excess

  E. hypoparathyroidism

  Correct Answer: C

  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.

• Question 726:

  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?

  A. central diabetes insipidus

  B. nephrogenic diabetes insipidus

  C. water intoxication

  D. solute overload

  E. syndrome of inappropriate antidiuretic hormone secretion (SIADH)

  Correct Answer: A

  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.

• Question 727:

  A 60-year-old patient with long-standing diabetes has a creatinine of 3.6, which has been stable for several years. Which of the following antibiotics requires the most dosage modification in chronic renal failure?

  A. tetracycline

  B. gentamicin

  C. erythromycin

  D. nafcillin

  E. chloramphenicol

  Correct Answer: B

  Many drugs require dosage modifications in chronic renal insufficiency. Bioavailability, distribution, action, and elimination of drugs all may be altered. Drugs that are nephrotoxic may be contraindicated or used only with extreme care in renal insufficiency. The aminoglycosides, vancomycin, ampicillin, most cephalosporins, methicillin, penicillin G, sulfonamides, and trimethoprim all should be given in reduced dosage to patients with chronic renal failure. The aminoglycosides and vancomycin can be nephrotoxic and should be used with caution in renal insufficiency. The small group of antibiotics not needing dosage modification includes chloramphenicol, erythromycin, the isoxazolyl penicillins (nafcillin and oxacillin), and moxifloxacin.

• Question 728:

  A55-year-old retired policeman has had hypertension for about 15 years for which he takes hydralazine.

  He has a 35 pack-year tobacco history and continues to smoke one pack a day. On his visit, he complains

  about the appearance of his nose and asks if something can be done to decrease the redness.

  Which of the following statements is correct?

  

  A. Hydralazine does not play a role in his nasal erythema.

  B. Smoking probably aggravates the dilatation of the blood vessels on his nose.

  C. He should avoid alcohol and spicy foods.

  D. There is no effective topical therapy.

  E. Laser therapy will worsen the erythema.

  Correct Answer: C

  He should avoid alcohol and spicy foods because these along with the heat, emotional stress, and hot temperature foods can aggravate rosacea. Hydralazine is a vasodilator and could worsen his nasal erythema. Smoking vasoconstricts rather than dilates blood vessels. Metronidazole gel is an effective topical therapy. Laser therapy is usually done after the other interventions have been tried

• Question 729:

  A46-year-old attorney is noted to have normal cholesterol levels but a very high fasting triglyceride level of 1600. He is otherwise healthy and has no risk factors for CAD. Which of the following statements is correct?

  A. Hypertriglyceridemia is a strong independent risk factor for premature CAD.

  B. Dietary modification is usually sufficient.

  C. High triglyceride levels are associated with elevated high-density lipoprotein (HDL) levels.

  D. Hypertriglyceridemia is usually associated with skin lesions.

  E. Control of triglyceride levels can prevent attacks of acute pancreatitis in patients with extreme hypertriglyceridemia.

  Correct Answer: E

  Hypertriglyceridemia has not been shown to be a strong independent risk factor for CAD, however, epidemiologic data do suggest a relationship. According to the National Cholesterol Education Program, when tirglycerides are above 200 mg/dL then non-HDL (total HDL) cholesterol becomes a pharmacologic treatment target. Severely elevated triglycerides (1000 mg/dL) are a recognized risk factor for attacks of acute pancreatitis, and control of the triglycerides can prevent these attacks. Diet alone is usually not sufficient at these high levels. A National Institutes of Health Consensus Conference has recommended that treatment be initiated in all patients with triglycerides greater than 500 mg/ 100 mL to prevent acute pancreatitis. Skin lesions are not present with hypertriglyceridemia.

• Question 730:

  A 59-year-old woman had a left modified radical mastectomy for intraductal carcinoma 2 years previously. She presents with confusion, lethargy, and thigh pain. X-rays reveal a lytic lesion in the shaft of the femur.

  Which of the following is the most appropriate initial therapy?

  A. radiotherapy to the femur

  B. vigorous saline infusion

  C. tamoxifen

  D. chemotherapy

  E. glucocorticoids

  Correct Answer: B

  Hypercalcemia is a common complication of malignancy. Mechanisms include bone metastases, humoral secretion (e.g., osteoclast-activating factor), prostaglandin, or ectopic parathormone production and immobilization. Hypercalcemia is often manifested by confusion and lethargy. The other metabolic abnormalities usually are not associated with confusion. Therapy is directed at increasing renal calcium clearance and inhibiting further bone resorption. Saline infusion raises the glomerular filtration rate and decreases calcium reabsorption in the proximal tubule. Under life-threatening circumstances, the infusion may need to be aggressive, as much as 6 L of saline daily plus furosemide. Radiotherapy will do nothing for the calcium. Tamoxifen is an antiestrogen used in the treatment of breast carcinoma and other malignancies. When used in the presence of bone metastases, it may contribute to hypercalcemia. Chemotherapy will not decrease the calcium levels. Glucocorticoids have an antitumor effect and reduce tumor production of humoral mediators, but act slowly.