USMLE USMLE Certifications USMLE-STEP-2 Questions & Answers

• Question 621:

  A27-year-old woman has used oral contraceptives (OCs) without problems for 5 years. However, she just read an article about complications of OCs in a popular women's magazine and asks you about the risks and hazards of taking OCs.

  You correctly tell her which of the following?

  A. The risk of developing ovarian cancer is increased.

  B. The risk of developing pelvic inflammatory disease (PID) is increased.

  C. The risk of developing endometrial cancer is decreased.

  D. The risk of bearing a child with major congenital anomalies is increased if taken while pregnant.

  E. The risk of ectopic pregnancy is increased.

  Correct Answer: C

  The incidence of ovarian cancer in OC users is 50% less than that found in nonusers. The incidence of PID is also decreased by 50% in OC users. The risk of endometrial cancer is decreased by 50% after 1 year of OC use, and the protective effect seems to persist after stopping the OC. In well-controlled studies, there is no increase in the risk of having a child with a major malformation, cardiac malformation, or limb abnormality. The risk of ectopic pregnancy is reduced by 90%, perhaps because the risk of any pregnancy approaches zero when the OC is taken correctly.

• Question 622:

  An obese 21-year-old woman complains of increased growth of coarse hair on her lip, chin, chest, and abdomen. She also notes menstrual irregularity with periods of amenorrhea. Which of the following is the most likely cause of this patient's symptoms?

  A. polycystic ovary disease

  B. an ovarian tumor

  C. an adrenal tumor

  D. Cushing disease

  E. familial hirsutism

  Correct Answer: A

  As many as 85% of women with hirsutism, obesity, and menstrual irregularities have polycystic ovary disease (Stein-Leventhal syndrome). Women with this disorder have chronic anovulation and frequent infertility despite the presence of adequate amounts of estrogen. Excessive luteinizing hormone (LH) response to gonadotropin-releasing hormone is thought by many to be the primary problem, resulting in ovarian theca-cell hyperplasia and hypersecretion of androgens. Others have found deficiencies of the ovarian enzymes involved in estrogen biosynthesis. Diagnosis is based on an elevated LH level, decreased follicle-stimulating hormone (FSH) level, and an LH/FSH ratio greater than 2:5. Combination estrogen- progestin therapy suppresses the androgen production. Less common causes of hirsutism are drug induced (e.g., testosterone, anabolic steroids), adrenal tumor or hyperplasia, Cushing disease, and ovarian tumors. Familial hirsutism is not associated with menstrual abnormalities or obesity.

• Question 623:

  A 17-year-old girl notes an enlarging lump in her neck. On examination, her thyroid gland is twice the normal size, firm to rubbery, multilobular, nontender, and freely mobile. There is no adenopathy. Family history is positive for both hypo- and hyperthyroidism. Her serum triiodothyronine (T3) and thyroxine (T4) levels are low normal, and serum thyroid-stimulating hormone (TSH) is high normal. Technetium scan shows nonuniform uptake. Serum and antithyroglobulin titer is strongly positive.

  Which of the following is the most appropriate treatment for this patient?

  A. corticosteroids

  B. antibiotics

  C. thyroid hormone

  D. radioactive iodine

  E. surgery

  Correct Answer: C

  The patient described in the question most likely has Hashimoto's thyroiditis, also called autoimmune or chronic lymphocytic thyroiditis. It is the most common cause of thyroiditis in the United States and is encountered more frequently in women than in men. Patients note progressive thyromegaly but are usually euthyroid at the outset. Hypothyroidism may appear years later, often heralded by an elevated serum TSH level. Diagnosis is based on the history, examination, heterogeneous uptake on thyroid scan, and the presence of antithyroid and antithyroglobulin antibodies. If the diagnosis is still in doubt, needle biopsy will demonstrate lymphocyte infiltration, sometimes in sheets or forming germinal centers. Subacute (de Quervain, granulomatous) thyroiditis will show polymorphonuclear cells, necrosis, and giant cells. Bacteria may not be present in acute suppurative thyroiditis. Thyroid infiltration and replacement by rock-hard, woody, fibrous tissue is typical of Riedel's struma. C-cell hyperplasia is associated with medullary thyroid carcinoma. Hashimoto's thyroiditis is treated with thyroid hormone. Lower doses (0.100.15 mg/day) of levothyroxine are used to treat hypothyroidism alone; whereas, higher doses (0.150.30 mg/day) suppress TSH release and diminish goiter size. Partial resection may result in enlargement of the remaining gland. Steroids, antibiotics, and radioiodine have no role in therapy.

• Question 624:

  A 43-year-old man with AIDS complains of shortness of breath and worsening diarrhea. His temperature is 98°F, respiration rate is 26/min, pulse rate is 100 /min, and BP is 100/70 mmHg. His lung and heart examination are unremarkable. A room air ABG reveals: pH 7.10/PCO2 5/PO2 130/calculated bicarbonate

  6. What is the primary acid-based disorder?

  A. respiratory acidosis

  B. respiratory alkalosis

  C. metabolic acidosis

  D. metabolic alkalosis

  Correct Answer: C

  The pH is 7.10, which indicates the primary disorder to be an acidosis. The low bicarbonate and the low carbon dioxide both are indicative of a metabolic cause for the acidosis. For the primary cause of the acidosis to be respiratory, the carbon dioxide would need to be greater than 40. In this case, the patient is compensating for the metabolic acidosis due to chronic diarrhea by hyperventilation.

• Question 625:

  A 17-year-old girl notes an enlarging lump in her neck. On examination, her thyroid gland is twice the normal size, firm to rubbery, multilobular, nontender, and freely mobile. There is no adenopathy. Family history is positive for both hypo- and hyperthyroidism. Her serum triiodothyronine (T3) and thyroxine (T4) levels are low normal, and serum thyroid-stimulating hormone (TSH) is high normal. Technetium scan shows nonuniform uptake. Serum and antithyroglobulin titer is strongly positive.

  What will thyroid biopsy of this patient most likely disclose?

  A. giant cell granulomas and necrosis

  B. polymorphonuclear cells and bacteria

  C. diffuse fibrous replacement

  D. lymphocytic infiltration

  E. parafollicular cells

  Correct Answer: D

  The patient described in the question most likely has Hashimoto's thyroiditis, also called autoimmune or chronic lymphocytic thyroiditis. It is the most common cause of thyroiditis in the United States and is encountered more frequently in women than in men. Patients note progressive thyromegaly but are usually euthyroid at the outset. Hypothyroidism may appear years later, often heralded by an elevated serum TSH level. Diagnosis is based on the history, examination, heterogeneous uptake on thyroid scan, and the presence of antithyroid and antithyroglobulin antibodies. If the diagnosis is still in doubt, needle biopsy will demonstrate lymphocyte infiltration, sometimes in sheets or forming germinal centers. Subacute (de Quervain, granulomatous) thyroiditis will show polymorphonuclear cells, necrosis, and giant cells. Bacteria may not be present in acute suppurative thyroiditis. Thyroid infiltration and replacement by rock-hard, woody, fibrous tissue is typical of Riedel's struma. C-cell hyperplasia is associated with medullary thyroid carcinoma. Hashimoto's thyroiditis is treated with thyroid hormone. Lower doses (0.100.15 mg/day) of levothyroxine are used to treat hypothyroidism alone; whereas, higher doses (0.150.30 mg/day) suppress TSH release and diminish goiter size. Partial resection may result in enlargement of the remaining gland. Steroids, antibiotics, and radioiodine have no role in therapy.

• Question 626:

  Ayoung woman with a history of seizures has a series of grand mal seizures in the emergency room. She is lethargic and has a nonfocal neurologic examination. Her blood gas reveals a pH of 7.12, carbon dioxide of 48, PO2 of 86, and calculated bicarbonate of 16. How would you best characterize her underlying acid-base problem?

  A. respiratory acidosis

  B. metabolic and respiratory acidosis

  C. metabolic acidosis and respiratory alkalosis

  D. metabolic alkalosis and respiratory acidosis

  E. metabolic acidosis

  Correct Answer: B

  The pH is 7.12, indicating acidosis as the primary disorder. Alow bicarbonate is consistent with a metabolic cause of the acidosis and a high carbon dioxide is consistent with a respiratory cause of the acidosis. Therefore, both are contributing as primary problems. The metabolic source likely is lactic acidosis from muscle breakdown resulting from the seizures. The respiratory source likely is related to the patient's postictal state and hypoventilation after the seizures.

• Question 627:

  A 54-year-old man complains of cough, shortness of breath, and pleuritic left-sided chest pain. Examination and CXR are compatible with a large left-sided pleural effusion. At thoracentesis, the pleural fluid is straw colored and slightly turbid, with a WBC count of 53,000/mL, RBC count of 1200/mL, glucose of 42 mg/100 mL, total protein of 5 g/100 mL, LDH of 418 IU/L, and pH of 7.2. Simultaneous serum total protein is 8 g/100 mL (normal, 68 g/100 mL), and serum LDH level is 497 IU/L (normal, 52149 IU/L). Gram stain is positive for gram-negative rods.

  Which of the following is the most likely cause of his pleural effusion?

  A. parapneumonic effusion

  B. congestive heart failure

  C. malignant effusion

  D. trauma E. nephrotic syndrome

  Correct Answer: A

  Although the differential diagnosis of a pleural effusion is large, the diagnostic possibilities may be narrowed by classifying the fluid as transudative or exudative. Exudates are characterized by a pleural fluid- to-serum protein ratio greater than 0.5, pleural fluid LDH greater than 200 IU/L, or pleural fluidtoserum LDH ratio greater than 0.6. Other common findings in exudative effusions are a WBC count greater than 1000/mL, glucose less than 60 mg/100 mL, and grossly hemorrhagic fluid. Causes of transudative effusions include CHF, nephrotic syndrome, cirrhosis with ascites, and myxedema. Causes of exudative fluid include parapneumonic effusion, neoplasm, pulmonary infarction, tuberculosis, and fungal infection among others. Alow pleural fluid pH (<7.30) limits the differential diagnosis to empyema, carcinoma, collagen vascular disease, esophageal rupture, tuberculosis, or hemothorax. Uncomplicated parapneumonic effusions have WBC counts under 40,000/mL, normal glucose levels, and a pH under 7.30; a positive Gram stain or culture constitutes a complicated parapneumonic effusion. These tend to loculate and form adhesions if not immediately and thoroughly drained by chest tube placement.

• Question 628:

  A 30-year-old woman comes to your office for evaluation of fatigue and shortness of breath on exertion. Past medical history is unremarkable. Physical examination is remarkable only for mild pallor. Lung and cardiovascular examination are normal. Laboratory tests show a hematocrit of 28 with a mean corpuscular volume of 72. WBC count and platelet count are normal. On taking further history from the patient, which of the following patient questions would most likely confirm a diagnosis?

  A. What is your family history of colon cancer?

  B. What is your family history of heart disease?

  C. How much alcohol do you drink?

  D. Do you have attacks of pain in your joints?

  E. How heavy are your menstrual periods?

  Correct Answer: E

  Iron-deficiency anemia characteristically is a hypochromic, microcytic anemia. Causes of iron- deficiency anemia include menstrual loss, inadequate diet, malabsorption, chronic inflammation, and chronic blood loss. Colon cancer could lead to chronic blood loss and irondeficiency anemia. This, however, would be very uncommon in a young patient without a family history of colon cancer. Alcohol causes a macrocytic anemia.

• Question 629:

  A 28-year-old man has the acute onset of colicky pain in the left costovertebral angle radiating into the groin, as well as gross hematuria. Abdominal x-ray discloses a stone in the left ureter. Which of the following is true concerning this disease?

  The patient spontaneously passes the stone, which is found to contain calcium oxalate. Which of the following is the most likely cause of this stone?

  A. chronic urinary tract infection

  B. vitamin D excess

  C. primary hyperparathyroidism

  D. idiopathic hypercalciuria

  E. RTA

  Correct Answer: D

  More than 90% of renal stones are visible on a plain abdominal x-ray, and the majority contain calcium oxalate. Staghorn calculi usually contain magnesium ammonium phosphate (triple phosphate or struvite) and are associated with alkaline urine. This is commonly encountered in chronic urinary tract infections with urea-splitting bacteria. Radiolucent stones often contain urea, which is associated with acidic urine. A small percentage (fewer than 10%) of renal stones contain cystine. The most common cause of calcium stone disease is idiopathic hypercalciuria. Almost half these patients will excrete more than 4 mg of calcium/kg body weight/24 h in the absence of hypercalcemia. Causes of hypercalciuria to be ruled out are sarcoidosis, hyperparathyroidism, and Paget's disease of bone. Idiopathic hypercalciuria is believed to result from either increased GI absorption of calcium, increased calcium resorption from bone, or excessive renal calcium leakage into the urine.

• Question 630:

  A 28-year-old man has the acute onset of colicky pain in the left costovertebral angle radiating into the groin, as well as gross hematuria. Abdominal x-ray discloses a stone in the left ureter. Which of the following is true concerning this disease?

  A. The majority of renal stones are radiolucent.

  B. Radiolucent stones are usually composed of uric acid.

  C. Staghorn calculi are associated with acid urine.

  D. Radiopaque stones usually contain cystine.

  E. Urate stones are associated with alkaline urine.

  Correct Answer: B

  More than 90% of renal stones are visible on a plain abdominal x-ray, and the majority contain calcium oxalate. Staghorn calculi usually contain magnesium ammonium phosphate (triple phosphate or struvite) and are associated with alkaline urine. This is commonly encountered in chronic urinary tract infections with urea-splitting bacteria. Radiolucent stones often contain urea, which is associated with acidic urine. A small percentage (fewer than 10%) of renal stones contain cystine. The most common cause of calcium stone disease is idiopathic hypercalciuria. Almost half these patients will excrete more than 4 mg of calcium/kg body weight/24 h in the absence of hypercalcemia. Causes of hypercalciuria to be ruled out are sarcoidosis, hyperparathyroidism, and Paget's disease of bone. Idiopathic hypercalciuria is believed to result from either increased GI absorption of calcium, increased calcium resorption from bone, or excessive renal calcium leakage into the urine.