USMLE USMLE Certifications USMLE-STEP-2 Questions & Answers

• Question 631:

  A 49-year-old woman with a history of migraine headaches reports 6 days of persistent headache, nausea, and recurrent vomiting. On examination, the patient is orthostatic. Electrolytes show a bicarbonate of 42 and a blood gas is obtained revealing a pH of 7.53, carbon dioxide of 53, and PO2 of

  85. What is the underlying acid-base abnormality?

  A. metabolic acidosis

  B. metabolic alkalosis

  C. respiratory acidosis

  D. respiratory alkalosis

  E. respiratory alkalosis and metabolic acidosis

  Correct Answer: B

  The pH of 7.53 indicates alkalosis as the primary disorder (normal pH is 7.40). A high bicarbonate is consistent with a metabolic cause of the alkalosis. The high carbon dioxide of 53 (normal is 40) is compensating for the primary disorder (alkalosis) in an attempt to bring the pH closer to normal. Metabolic alkalosis results from renal bicarbonate reabsorption. Processes which maintain persistent high reclamation of bicarbonate include dehydration, hypokalemia, hypercapnea, and mineralocorticoid excess.

• Question 632:

  A 27-year-old female complains of dysuria and urinary frequency. Urinalysis reveals 1020 WBCs per high-power field and numerous gram-negative bacteria. She denies fevers, chills, and has no flank pain or tenderness.

  Which of the following bacteria is most likely responsible for this patient's urinary tract infection?

  A. Klebsiella

  B. Chlamydia

  C. Escherichia coli

  D. Pseudomonas

  E. Candida

  Correct Answer: C

  Urinary tract infections are extremely common in young women. For simple infections uncomplicated by fever, chills, or flank pain, a single dose of an antibiotic may be curative. In the presence of symptoms suggesting renal parenchymal infection (i.e., pyelonephritis), treatment should continue for as long as 2 weeks, and parenteral antibiotics may be required (e.g., fluoroquinolone). Bacteriuria in pregnant women should be treated regardless of symptoms; whereas, bacteriuria in patients with indwelling catheters should probably be treated only in the presence of symptoms. Chronic suppressive antibiotic therapy in the latter group has not been shown to be useful. Radiologic investigation for underlying anatomic abnormalities should be undertaken in girls up to age 6, in all males after their first infection, and in women of any age with recurrent urinary tract infections. The most common pathogen is E. coli, accounting for greater than 80% of infections. Other organisms frequently encountered include Klebsiella, Proteus, and Enterobacter species.

• Question 633:

  A 27-year-old female complains of dysuria and urinary frequency. Urinalysis reveals 1020 WBCs per high-power field and numerous gram-negative bacteria. She denies fevers, chills, and has no flank pain or tenderness.

  Which of the following statements concerning urinary tract infections is true?

  A. A single dose of an antibiotic may be sufficient treatment.

  B. Pregnant women with bacteriuria should not be treated if asymptomatic.

  C. Patients with flank pain or fever should be hospitalized.

  D. Hematuria indicates renal involvement.

  E. Urologic investigation is indicated after the treatment course is completed.

  Correct Answer: A

  Urinary tract infections are extremely common in young women. For simple infections uncomplicated by fever, chills, or flank pain, a single dose of an antibiotic may be curative. In the presence of symptoms suggesting renal parenchymal infection (i.e., pyelonephritis), treatment should continue for as long as 2 weeks, and parenteral antibiotics may be required (e.g., fluoroquinolone). Bacteriuria in pregnant women should be treated regardless of symptoms; whereas, bacteriuria in patients with indwelling catheters should probably be treated only in the presence of symptoms. Chronic suppressive antibiotic therapy in the latter group has not been shown to be useful. Radiologic investigation for underlying anatomic abnormalities should be undertaken in girls up to age 6, in all males after their first infection, and in women of any age with recurrent urinary tract infections. The most common pathogen is E. coli, accounting for greater than 80% of infections. Other organisms frequently encountered include Klebsiella, Proteus, and Enterobacter species.

• Question 634:

  A 33-year-old woman experiences visions of flashing lights followed by throbbing left-sided temporal pain and nausea. Which of the following is the most likely diagnosis?

  This patient is most likely to benefit from acute treatment with which of the following substances?

  A. propranolol

  B. prednisone

  C. sumatriptan

  D. heparin

  E. oxygen

  Correct Answer: C

  The typical migraine attack consists of a visual aura with flashes, scintillating scotomata (field loss), or fortification spectra followed by a throbbing unilateral temporal headache. There may be associated vestibular, GI, or neurologic symptoms. Attacks are often precipitated by stress, fatigue, or foods that contain tyramine (e.g., cheese, yogurt, nuts) or phenylethylamine (wine, chocolate). Symptoms peak within an hour of onset and persist for hours to days. A positive family history is found in as many as 50% of cases. Tension headaches are more often bilateral and described as band like or vise like and are not usually associated with visual auras. TIAs more typically present as transient monocular blindness without aura or headache. Temporal arteritis may present as painless loss of vision without aura, but is usually in older people. Cluster headaches are much more common in men. Sumatriptan and the other triptans work by inhibiting the release of vasoactive peptides, promoting vasoconstriction, and blocking brainstem pain pathways. Sumatriptan comes in oral, injectable, and nasal spray form. Ergotamine tartrate, antiemetics, and analgesics may also be used in the acute treatment of migraine headache. Prophylactic medications such as beta-blockers, tricyclic antidepressants, calcium channel blockers, and anticonvulsants are ineffective for acute attacks. Avoidance of known precipitants and control of stress are also important in prevention.

• Question 635:

  A 33-year-old woman experiences visions of flashing lights followed by throbbing left-sided temporal pain and nausea. Which of the following is the most likely diagnosis?

  A. tension headache

  B. transient ischemic attack (TIA)

  C. temporal arteritis

  D. migraine headache

  E. cluster headache

  Correct Answer: D

  The typical migraine attack consists of a visual aura with flashes, scintillating scotomata (field loss), or fortification spectra followed by a throbbing unilateral temporal headache. There may be associated vestibular, GI, or neurologic symptoms. Attacks are often precipitated by stress, fatigue, or foods that contain tyramine (e.g., cheese, yogurt, nuts) or phenylethylamine (wine, chocolate). Symptoms peak within an hour of onset and persist for hours to days. A positive family history is found in as many as 50% of cases. Tension headaches are more often bilateral and described as band like or vise like and are not usually associated with visual auras. TIAs more typically present as transient monocular blindness without aura or headache. Temporal arteritis may present as painless loss of vision without aura, but is usually in older people. Cluster headaches are much more common in men. Sumatriptan and the other triptans work by inhibiting the release of vasoactive peptides, promoting vasoconstriction, and blocking brainstem pain pathways. Sumatriptan comes in oral, injectable, and nasal spray form. Ergotamine tartrate, antiemetics, and analgesics may also be used in the acute treatment of migraine headache. Prophylactic medications such as beta-blockers, tricyclic antidepressants, calcium channel blockers, and anticonvulsants are ineffective for acute attacks. Avoidance of known precipitants and control of stress are also important in prevention.

• Question 636:

  Which of the following is the most common cause of nephrotic syndrome?

  A. diabetes mellitus

  B. Hodgkin's lymphoma

  C. heroin abuse

  D. malignant hypertension

  E. renal failure

  Correct Answer: A

  The nephrotic syndrome is characterized by proteinuria of greater than 3 g/day. Hypoalbuminemia, edema, and hyperlipidemia, lipiduria, and hypercoagulability are other defining features. Six entities account for >90% of cases of nephrotic syndrome in adults: minimal change disease (MCD), focal and segmental glomerulosclerosis (FSGS), membranous glomerulopathy, membranoproliferative glomerulonephritis (MPGN), diabetic nephropathy, and amyloidosis. In North America, the most common cause of nephrotic syndrome is diabetes mellitus. Heroin use has been associated with FSGS and lymphoma has been associated with glomerular disorders. Some of the glomerular disorders above may present with nephritic syndrome and if untreated progress to renal failure

• Question 637:

  A92-year-old man is referred from his nursing home for evaluation of lethargy. Examination is unrevealing, but laboratory results are significant for a serum sodium level of 118 meq/L (normal, 135 148). Serum osmolality is 260, urine osmolality is 450, and urine sodium is 80. Which of the following is the most likely cause of this patient's lethargy?

  A. hyperglycemia

  B. hyperlipidemia

  C. hyperproteinemia

  D. SIADH

  E. diabetes insipidus

  Correct Answer: D

  Hyponatremia is a common metabolic derangement. Facititious hyponatremia is seen with severe hyperlipidemia or hyperproteinemia (which lower plasma water content) and with hyperglycemia due to water movement out of cells. Most patients with hyponatremia are hypoosmolar and the diagnosis is based on an estimation of extracellular fluid (ECF) volume status. Decreased ECF volume and hyponatremia are associated with diuretic use, diarrhea, and dehydration. Expanded ECF volume due to decreased effective circulating volume and increased ADH secretion may result in edema and hyponatremia as often seen with congestive heart failure, cirrhosis of the iver, and nephritic syndrome. Euvolemia and hyponatremia can be due to hypothyroidism, drenal insufficiency, and other conditions associated with the SIADH. Diabetes insipidus is a cause of hypernatremia.

• Question 638:

  Select the ONE best lettered option that is most closely associated with the question below. A 38-year-old African American female with shortness of breath and bilateral hilar adenopathy on CXR.

  A. rheumatoid arthritis

  B. SLE

  C. Wegener's granulomatosus

  D. polyarteritis nodosa

  E. Goodpasture syndrome

  F. fibromyalgia

  G. osteoarthritis (OA)

  H. giant cell arteritis

  I. sarcoidosis

  Correct Answer: I

  Sarcoidosis is a relatively common disease. In the United States, most patients are African American (ratio ranges from 10:1 to 17:1). The disease is systemic, and the lung is almost always affected (primarily an ILD). Seventyfive to ninety percent of patients have enlarged intrathoracic lymph nodes, usually the hilar nodes

• Question 639:

  Select the ONE best lettered option that is most closely associated with the question below.

  A 45-year-old female with pain and visible swelling in her metacarpal-phalangeal joints bilaterally. Her distal interphalangeal joints (DIPs) appear normal.

  A. rheumatoid arthritis

  B. SLE

  C. Wegener's granulomatosus

  D. polyarteritis nodosa

  E. Goodpasture syndrome

  F. fibromyalgia

  G. osteoarthritis (OA)

  H. giant cell arteritis

  I. sarcoidosis

  Correct Answer: A

  Rheumatoid arthritis affects approximately 0.8% of the population. Women are affected three times more often than men. Synovial inflammation causes tenderness, swelling, and limitation of motion. Most often the arthritis is symmetric and characteristically involves joints such as the wrist and the proximal interphalangeal and metacarpophalangeal joints.

• Question 640:

  Select the ONE best lettered option that is most closely associated with the question below.

  A 60-year-old obese male with Heberden's nodes on his hands and chronic, severe leftsided knee pain.

  A. rheumatoid arthritis

  B. SLE

  C. Wegener's granulomatosus

  D. polyarteritis nodosa

  E. Goodpasture syndrome

  F. fibromyalgia

  G. osteoarthritis (OA)

  H. giant cell arteritis

  I. sarcoidosis

  Correct Answer: G

  Risk factors for OA include age, obesity, major trauma, and repetitive joint use. Bony enlargements of the DIP joint (Heberden's nodes) are the most common form of idiopathic OA. Obesity is a risk factor for knee OA. With severe OA of the knee in particular, obesity is thought to play a large role in pathogenesis.