USMLE USMLE-STEP-3 Online Practice Questions and Exam Preparation

USMLE USMLE-STEP-3 Online Questions & Answers

• Question 671:

  A74-year-old male with a history of hypertension, CAD, and a 50 pack-year history of smoking presents with complaints of pain and cramping sensation of the thigh and buttock areas for the past 2 months. On detailed history, patient reports that the pain is usually during ambulation and relieves with sitting down. The pain does not change with respect to sitting or supine position. He denies any recent trauma, weakness of the legs, or paresthesias. He takes his prescription medications regularly and denies using alcohol, drugs, or any herbs/ supplements. Which of the following should be performed as an initial test to help confirm your clinical impression?

  A. ankle-brachial index (ABI)
  B. x-ray of the lumbar spine
  C. electromyelography and nerve conduction studies of the lower extremities
  D. lower extremity venous ultrasound with Dopplers
  E. angiography of the aorta and lower extremities
  A. ankle-brachial index (ABI)

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  Explanation

  Peripheral arterial disease (PAD) affects roughly 12% of the U.S. population with higher prevalence rates in persons over the age of 70. The classic symptoms of PAD are intermittent claudication which is usually described by patients as cramping pain in the calf, legs, thighs, or buttocks during any type of exercise that quickly relieves with rest. This scenario of worsening with activity and relief with rest is consistent with the disease process, as the pain results from ischemia. The ischemia is worse during periods of increased oxygen demand where the vascular insufficiency fails to meet the demand. Not all patients with PAD are symptomatic, thus an assessment of risk factors and a thorough physical examination are usually key to making the diagnosis in asymptomatic patients. The ABI is an easy, inexpensive, noninvasive test with a high correlation to angiography that can be done in the office. ABI is the usual initial test to screen for PAD.

  

  A value of greater than 1.0 is considered normal, whereas values less than 0.9 are consistent with varying grades of PAD:

  ?1.0 or greater: normal ?0.810.9: mild PAD ?0.510.8: moderate PAD ?;0.5: severe PAD The sensitivity of the ABI can be increased if performed post exercise. The ABI, however, has its limitations in patients with noncompressible, calcified vessels such as the elderly or in patients with diabetes. An ABI of greater than 1.3 may suggest the above scenario and its utility would be suspect. In these cases, more detailed testing may be warranted. Other modalities to assess PAD include arterial Dopplers, magnetic resonance angiography, and conventional angiography. The initial therapy for patients with PAD should be a trial of a structured walking program along with smoking cessation. Walking programs have been shown to increase walking distance without symptoms. In addition, walking also improves endothelial function, collateral vessel formation and function, and control of blood pressure, lipids, and blood sugars.

  Pentoxyfylline has been traditionally recommended for PAD; however its efficacy is modest at best based on newer trial data. Antiplatelet agents may also be added for PAD as it will improve cardiovascular risk and perhaps modify the pathogenesis for PAD. Ultimately, risk factor modification is key for prevention and reduction of complications and comorbidities. Severe PAD or patients who require more specialized intervention may require vascular surgery consultation.

• Question 672:

  A32-year-old female presents to the outpatient clinic with complaints of ongoing headaches. For the past 8 months, she has had recurrent headaches which she describes as bilateral, occipital, with a tight/squeezing pain, lasting for several hours and relieved with nonsteroidal anti-inflammatory medication (NSAIDs). Further questioning reveals chronic feelings of fatigue and poor concentration. She admits to "constantly worrying" about her job performance as well as issues involving her relationship with a live-in boyfriend. In fact, her focusing on these concerns interferes with her sleep. As a result, she has on more than one occasion awakened with extreme panic, tremors, diaphoresis, nausea, and palpitations. Her medical problems include gastroesophageal reflux disease that is treated with famotidine. She drinks an occasional glass of wine and denies drug use.

  Which of the following is her most likely diagnosis?

  A. GAD
  B. major depressive disorder
  C. OCD
  D. panic disorder
  E. social phobia
  A. GAD

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  Explanation

  The patient does not complain of significant depression, anhedonia, problems with appetite, or guilt consistent with major depressive disorder. She also does not complain of specific obsessions or compulsions necessary for OCD, such as fears of dirt, hurting individuals, or the need for symmetry. While she does have panic attacks, they are not unexpected as they relate to her worries about aspects of her life. She also does not have the ongoing fear of having more attacks characteristic of panic disorder.

  Social phobia consists of fears of acting in an embarrassing or humiliating way in public, which are not apparent in the above case. She complains of excessive anxiety and worry about a number of activities associated with other cognitive and physical symptoms. This case fits the criteria for GAD (DSM IV-TR). GAD tends to be chronic, often requiring lifelong treatment. Although benzodiazepines such as alprazolam are effective, they should not be prescribed indefinitely given their side effects (sedation, disinhibition) and potential for tolerance, withdrawal, and abuse.

  They are not infrequently used in conjunction with another medication, often in the short-term, until the primary psychotropic medication takes effect. Atenolol or other beta-blockers can be useful in situational anxiety, such as social phobia (social anxiety disorder) or specific phobia. Beta-blockers treat the somatic manifestations of anxiety more than the cognitive and affective components. As bupropion is thought to block the reuptake of dopamine and/or norepinephrine, it tends to cause activation and is not considered to be a first-line treatment for GAD. Lithium is a mood stabilizer that is also used in cases of refractory depression. It is inappropriate for use in the treatment of GAD. Venlafaxine, which blocks the reuptake of both serotonin and norepinephrine, and other SSRIs are effective and well tolerated in patients suffering with GAD. Their safety and efficacy make them appropriate first-line and maintenance therapies for GAD.

• Question 673:

  A 50-year-old man comes to the emergency room (ER) with a history of vomiting of 3 days' duration. His past history reveals that for approximately 20 years he has been experiencing epigastric pain that lasts for 23 weeks during spring and autumn. He remembers getting relief from pain by taking milk and antacids. Physical examination showed a fullness in the epigastric area with visible peristalsis, absence of tenderness, and normal active bowel sounds. What is the most likely diagnosis?

  Which of the following metabolic abnormalities are typically found in the above patient?

  A. decreased antidiuretic hormone
  B. hypercalcemia
  C. hypokalemia
  D. hyperchloremia
  E. decreased aldosterone secretion
  C. hypokalemia

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  Explanation

  In a patient who is known to have had symptoms of peptic ulcer disease for many years and presents with nausea and vomiting, one should consider gastric outlet obstruction. The bstruction can be the result of an exacerbation of the ulcer and subsequent edema or it can be secondary to scar tissue formation. These patients typically describe the sensation of epigastric fullness and demonstrate visible peristalsis going from left to right. A succussion splash may be audible. The history of periodicity and pain relief by taking antacids also favors a diagnosis of previous peptic ulcer disease. Patients with an umbilical hernia will have a mass in the region of the umbilicus. Patients with acute cholecystitis usually present with the sudden onset of pain, radiating to the back, with fever and chills. Volvulus of the sigmoid colon presents with constipation and abdominal distention but vomiting is a late feature. Small bowel obstruction would be associated with a history of colicky abdominal pain, nausea, and vomiting.

  Additionally, patients with small bowel obstruction usually have hyperactive highpitched bowel sounds on examination

• Question 674:

  A 25-year-old nulligravid woman presents as a new patient to your gynecology practice. She has recently moved to the area. She is a healthy woman with no medical problems and is currently using oral contraceptives without problems. She informs you that she and her husband are planning to start a family within the next year. On review, you find her family history is unremarkable, but she informs you that her husband's sister has cystic fibrosis.

  If she and her husband were both known to carry a cystic fibrosis gene mutation, what would be their likelihood of having a child with cystic fibrosis?

  A. 100%
  B. 75%
  C. 50%
  D. 33%
  E. 25%
  E. 25%

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  Explanation

  Cystic fibrosis is the most common hereditary condition in Whites with a carrier frequency of 1 in 25. The American College of Obstetricians and Gynecologists, the American College of Medical Genetics, and the National Institutes of Health have recommended that cystic fibrosis carrier screening be offered to all White couples either pregnant or considering a pregnancy, and that the availability of screening be discussed with members of other ethnic groups who have a lower frequency of cystic fibrosis carrier state. Cystic fibrosis is inherited in an autosomal recessive fashion, so for a couple in which both mother and father are carriers the risk of having an affected child is 25% or 1 in 4. In the case presented, in which the husband's sister has cystic fibrosis, his likelihood of being a carrier is 2 in 3 (since he has an affected sibling, both of his parents are obligate carriers, and since he is not affected, he is either a noncarrier [1 in 3] or a carrier [2 in 3]). This pattern is true for all autosomal recessive disorders.

• Question 675:

  A76 year old White female presents to her family practitioner complaining of vaginal pressure, dyspareunia, urinary incontinence, and difficulty emptying her bladder for the past 4 weeks. Seven years ago she had a prolapsed "bladder tacking" procedure. Her postvoid residual urine in the office measures 250 mL. The most notable finding on pelvic examination is seen in Figure .

  

  Which of the following would be the most appropriate action to take at this time?

  A. referral for immediate surgery
  B. abdominal and pelvic CT scan
  C. urinalysis (UA) with culture and sensitivity
  D. prescription for oxybutynin (Ditropan)
  E. urodynamic studies
  C. urinalysis (UA) with culture and sensitivity

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  Explanation

  When pelvic organs prolapse occurs beyond the level of the hymen, anatomic obstruction of urine occurs in approximately 30% of patients. Over time, urinary stasis from obstruction can lead to UTIs. Detrusor hypocontractility, not overactivity, can be another long-term sequela of chronic urinary retention, enhanced by a stretch injury to the postsynaptic parasympathetics in the bladder wall. Menopause alone is not a risk factor for retention, and a spinal cord tumor is not likely in this patient without specific neurologic complaints or findings on physical examination. Due to urinary stasis, she is at risk for a UTI. Left untreated, she could develop obstructive uropathy and/or pyelonephritis. Surgery is an option, but not without the prior consideration of nonsurgical options such as a pessary or intermittent clean, self- catheterization (if the problem were to persist). In the event of chronic retention, radiographic imaging would help to assess for upper tract obstruction (i.e., hydronephrosis). Oxybutynin is not appropriate, as it could compound urinary retention. Urodynamic studies could be helpful in the future to ascertain the exact cause of her retention (obstruction from the prolapse vs. chronic detrusor insufficiency vs. neurogenic bladder), but is not the first action to consider.

• Question 676:

  A 42-year-old man presents to your clinic with a 1-week history of pain and inflammation involving his right first metatarsophalangeal (MTP) joint. He describes the pain as sudden in onset and worse at night. He denies experiencing any fever or traumatic injury to the joint and states that he has never had this type of pain before. He denies any chronic medical conditions, any prior surgery, and any current medication use. Besides an erythematous and exquisitely tender right first MTP joint, the remainder of his physical examination is unremarkable.

  After 1 week of treatment, your patient states that his pain and inflammation have resolved. You measure a serum urate level and find it elevated. Urinary urate excretion is high. Which of the following interventions is now most appropriate?

  A. no further treatment is necessary
  B. daily oral allopurinol
  C. daily oral probenecid
  D. daily oral colchicine with allopurinol
  E. daily oral colchicine with probenecid
  D. daily oral colchicine with allopurinol

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  Explanation

  This patient's presentation is consistent with gout. Aspiration of his first MTP joint is likely to reveal the presence of needle-shaped, negatively birefringent crystals. Rhomboid-shaped, positively birefringent crystals are characteristic of calcium pyrophosphate deposition disease, or pseudogout, with the knee being the joint most commonly affected. Nonbirefringent crystals are found in hydroxyapatite crystal deposition disease. The synovial fluid from joints affected by gout typically show evidence of inflammation in the form of leukocytosis with a predominance of polymorphonuclear neutrophils. The presence of bacteria in synovial fluid is characteristic of infection rather than gout, although gout and infectious arthritis may coexist. (Cecil Textbook of Medicine, pp. 17031708) Acute gouty arthritis usually presents in a monoarticular or oligoarticular distribution, with the first MTP joint most commonly affected. The diagnostic gold standard is detection of urate crystals within the synovial fluid of affected joints.

  It most commonly affects adult men with a peak incidence in the fifth decade of life. While patients with gout typically also have hyperuricemia, only a small fraction of the people with hyperuricemia actually have or will develop gout.

  Tophi are primarily seen in patients with long-standing hyperuricemia and is considered a finding of chronic gouty arthritis. As the disease progresses, acute attacks become more frequent and last longer if left untreated. Indomethacin inhibits the prostaglandin synthesis that facilitates the inflammation of acute gout and inhibits the phagocytosis of urate crystals by leukocytes. This inhibits the cell lysis and release of cytotoxic factors that initiate the inflammatory cascade. Allopurinol (an inhibitor of urate synthesis) and probenecid and sulfinpyrazone (promoters of urate excretion) are useful for preventing gout but are not effective during an acute gout attack. Aspirin is inappropriate in the treatment of gout since it can inhibit urate elimination and, therefore, increase hyperuricemia.

• Question 677:

  An 18-month-old boy is taken to his family doctor for evaluation of easy bruising and decrease range of motion of the right knee. On examination, he had multiple large ecchymoses, mostly in the lower extremities, and a right knee hemarthrosis. He has not had surgery or family history of a bleeding disorder. Initial blood tests reveal a prolonged activated partial thromboplastin time (aPTT) with a normal PT and platelet count.

  What further tests should be ordered to make a diagnosis in this boy?

  A. factor VII
  B. factors II, VII, IX, and X
  C. bleeding time
  D. factors XI, IX, VIII
  E. factor I and II
  D. factors XI, IX, VIII

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  Explanation

  The PTT represents the time for clot formation after adding calcium, phospholipids, and kaolin to citrated blood. It is prolonged by heparin, direct thrombin inhibitors, a deficiency or inhibitor for factors in the intrinsic and common pathway (i.e., factors II, V, VIII, IX, X, XI, XII) as well as lupus anticoagulant, vitamin K deficiency, or severe liver disease. The PT represents the time for clot formation after the addition of thromboplastin (tissue factor) and calcium to citrated blood. It is prolonged with deficiencies of the extrinsic and common pathway factors II, V, VII, X, or fibrinogen; liver disease; vitamin K deficiency and Warfarin use.

• Question 678:

  A64-year-old man with a long history of smoking but no significant past medical history presents to his physician's office complaining of a 12 week history of worsening dyspnea, facial swelling, and discoloration. He has also had swelling and discomfort of his right arm. Physical examination reveals edema with plethora of the face and right arm, with prominent collateral veins over the chest wall.

  What test is most likely to establish the cause of the patient's symptoms?

  A. PA and lateral chest radiograph
  B. echocardiogram
  C. CT of the chest with intravenous contrast
  D. ultrasound with Doppler flow studies of the right arm
  E. arteriogram of the carotid and axillary arteries
  C. CT of the chest with intravenous contrast

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  Explanation

  The patient's most likely diagnosis is superior vena cava syndrome (SVCS), which is usually due to external compression of the SVC by tumor or lymph nodes, sometimes associated with intraluminal thrombosis. The diagnosis is established by CT of the chest with intravenous contrast, which can demonstrate the level and extent of obstruction, as well as the presence of any caval thrombus. Plain chest radiography may show some mediastinal widening, but yields much less information. Echocardiography would be appropriate if the patient had suspected pericardial effusion with tamponade, but that would not produce unilateral arm edema and discoloration. Doppler studies of the deep veins of the arm would be useful if the problem were isolated to the upper extremity. In this case, the cerebral venous drainage is also involved, so the obstruction is more proximal, i.e. at the level of the SVC. Arteriogram would not be indicated, since the issue in this case is venous obstruction, not arterial insufficiency. Unless the patient has cerebral edema with mental status changes or upper airway compromise due to tracheal obstruction, the diagnosis of SVCS is not immediately life-threatening, and emergent therapy is not usually indicated. The majority of patients with SVCS present with this as the initial presentation of their malignancy, before a tissue diagnosis has been established. This is problematic, since therapy is guided by the underlying malignancy (radiation therapy for non-small cell lung cancers, chemotherapy +/- radiation for small cell lung cancers or lymphomas), but empiric initiation of radiation or glucorticoids (if the underlying diagnosis is lymphoma) may obscure the histologic diagnosis. The most important initial step is to try to obtain a biopsy to establish the cancer type before initiating therapy. If symptoms are severe, placement of intravascular stents may provide rapid symptomatic relief without compromising subsequent diagnostic or therapeutic efforts. Surgical intervention is rarely indicated, and usually only

  for benign causes of SVCS.

• Question 679:

  A 50-year-old male presents to your office for a routine annual physical examination. He has no specific complaints for this visit other than wanting to be checked for all the usual stuff. His last visit with you was a year ago for a physical examination. At that time his examination was normal. You performed blood work that was within normal limits and included a total cholesterol of 172 with a high-density lipoprotein (HDL) of 45 and low-density lipoprotein (LDL) of 100. He reports that he had a tetanus shot 5 years ago.

  Past medical history: Unremarkable Past surgical history: 1. Appendectomy at age 17 2. Vasectomy at age 43 Medications: Daily multivitamin Allergies: NKDA (no known drug allergies) Family history: Father died at age 78 of a heart attack Mother is alive at age 76. She has hypertension and osteoarthritis Brother aged 48 without known chronic medical condition Children aged 16, 14, and 8--no known chronic medical illness Social history: Married, employed as an accountant; college graduate Denies tobacco or recreational drug use Drinks one alcoholic drink (either beer or wine) a day Does not exercise on a regular basis

  Which of the following office examinations would be recommended for this patient?

  A. measurement of his blood pressure
  B. abdominal palpation to screen for abdominal aortic aneurysm
  C. testicular examination to screen for testicular cancer
  D. whole body skin examination to screen for skin cancer
  E. palpation of the thyroid gland to screen for thyroid cancer
  A. measurement of his blood pressure

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  Explanation

  Explanations:

  The United States Preventative Services Task Force (USPSTF) is an independent panel of experts in primary care and prevention that systematically reviews the evidence of effectiveness and develops recommendations for clinical preventative services. By carefully and systematically reviewing the available literature, the USPSTF makes recommendations on the effectiveness of screening, counseling, immunization, and chemoprevention using the following rating system:

  A. The USPSTF strongly recommends that clinicians provide the service to eligible patients.

  B. The USPSTF recommends that clinicians provide this service to eligible patients.

  C. The USPSTF makes no recommendation for or against routine provision of the service.

  D. The USPSTF recommends against routinely providing the service to asymptomatic patients.

  I. The USPSTF concludes that the evidence is insufficient to recommend for or against routinely providing the service. All of the recommendations of

  the USPSTF are available free of charge at their web site www.preventiveservices.ahrq.gov. In a 50-year-old male who is generally healthy and does not present any apparent high-risk personal or family history, the USPSTF gives a level A recommendation to blood pressure measurement as a screening tool for hypertension in adults over the age of 18, as there is good evidence that screening for, and treating, hypertension can reduce the incidence of cardiovascular disease. There is insufficient evidence to

  recommend for or against screening for abdominal aortic aneurysm by abdominal palpation or for screening for skin cancer by a whole body skin examination (level I recommendation). This suggests that the evidence is lacking that performing these interventions will reduce the morbidity or mortality associated with these conditions. The USPSTF gives level D recommendations to screening for thyroid cancer by palpation and for screening for testicular cancer by palpation. Fecal occult blood testing using

  three selfcollected stool cards as a screening test for colon cancer has been given a level A recommendation, with good data to support reduction in colon cancer mortality from periodic screening. There is also evidence to support screening for colon cancer by flexible sigmoidoscopy or colonoscopy, with double-contrast barium enema as a possible alternative as well. Screening for lipid disorders in men over the age of 35 and women over the age of 45 also receives a level A recommendation. In general,

  the interval for repeat screening for an otherwise low-risk patient with lipid levels within the goal range, based on the National Cholesterol Education Project's Consensus opinion statement, would be 5 years. As this patient had lipid levels within the goal range 1 year ago, it would not be necessary to repeatthis blood test at this visit. Screening for cardiovascular disease by the routine use of electrocardiography in asymptomatic, lowrisk patients has been given a D recommendation, as there is an absence of

  evidence of improved health outcomes from this intervention. Screening for lung cancer by chest x-ray and for glaucoma by measurement of intraocular pressure are level I recommendations, with insufficient evidence to recommend for

  or against these interventions.

• Question 680:

  An 18-month-old boy is brought into the urgent care clinic by his mother who complains that he is "eating weird stuff." For the past few months since being able to walk, he has been found chewing and swallowing odd substances, such as hair, paper, and string. She has been more concerned since she recently noticed him eating clay from around the foundation of their apartment in the projects. His appetite has been affected because of this, and she is worried that he will become sick as a result.

  Determination of which of the following blood levels would be the most appropriate next step in the workup and management of this patient?

  A. folate
  B. iron
  C. lead
  D. manganese
  E. zinc
  E. zinc

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  Explanation

  This toddler has developed pica, the eating of nonnutritive substances. Decreased levels of folate may be associated with depression and dementia in adults but is not seen in cases of pica. Iron deficiency, a potential cause of pica, may present with eating of dirt. A lead level would be necessary to determine if the child were eating lead-based paint. Manganese levels have not been shown to be abnormal in pica. As zinc deficiency is another cause of pica, assessment of a zinc level is essential in children who consume clay (as is being done by the child in this case)