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

USMLE USMLE-STEP-3 Online Questions & Answers

• Question 491:

  A 49-year-old male presents with crushing substernal pain and rules out for a myocardial infarction. He is noted to have subcutaneous emphysema of the chest and neck and precordial crackles that correlate to his heartbeat but not his respirations Which of the following approaches to management is most appropriate?

  A. This condition should always be managed operatively.
  B. The best diagnostic test is thoracic CT.
  C. Early endoscopy is contraindicated.
  D. Primary surgical repair is the first approach to treatment if the diagnosis is made within 24 hours.
  E. Anticoagulation should be started while the diagnostic workup proceeds.
  D. Primary surgical repair is the first approach to treatment if the diagnosis is made within 24 hours.

  ---

  Explanation

  "Hamman's crunch" is precordial crackles heard on auscultation that correlate with heart sounds in the setting of mediastinal emphysema and is suggestive of esophageal perforation. When present along with subcutaneous emphysema of the chest and neck, pneumomediastinum from an esophageal perforation is the most likely diagnosis. The most common cause of esophageal perforation is iatrogenic, but it may be spontaneous (Boerhaave's syndrome) or secondary to a malignancy or stricture. Diagnosis is often made after clinical suspicion by endoscopy or a swallow study with water- soluble contrast. If diagnosed early (within 24 hours), a primary repair is the first approach to treatment. Closure is dependent on the amount of infected or necrotic tissue, tension on the anastomosis, etiology of the perforation, and the ability to adequately drain the contaminated areas. Late perforations may be complicated in their management, requiring several procedures or diversion to provide for adequate healing.

• Question 492:

  A 53-year-old female has made an appointment to see you concerning the recent onset of menopause. Her last menstrual period was 8 months ago and, over the last year, she had noticed that her periods were becoming lighter and less frequent. In addition, she has developed frequent hot flashes, and her mood has become very labile. She wishes to know what your advice is regarding hormone replacement therapy (HRT). She has heard recent reports in the news concerning an increased risk of developing cardiovascular complications, especially heart attacks and strokes. Although she is in great health, her father died at age 50 of a massive heart attack. Her mother is alive and well, and there is no history of breast cancer among the females in her family.

  Regarding postmenopausal HRT, which of the following statements would be correct?

  A. Known benefits from HRT in postmenopausal women include a reduction in the incidence of osteoporosis and bone fractures (particularly hip fractures).
  B. Known benefits from HRT in postmenopausal women include a cardioprotective effect, which reduces the incidence of coronary artery disease (CAD) and myocardial infarction (MI).
  C. HRT increases the incidence of endometrial cancer in all patients.
  D. Although HRT reduces vasomotor instability and hot flashes after menopause, this effect is short- lived and there is no effect in mood stability.
  E. Despite recent press reports, any woman at risk for osteoporosis should take HRT, regardless of cardiovascular risk factors.
  A. Known benefits from HRT in postmenopausal women include a reduction in the incidence of osteoporosis and bone fractures (particularly hip fractures).

  ---

  Explanation

  Despite recent findings from the Women's Health Initiative (WHI) study, which show that HRT may not be cardioprotective and may increase the risk for cardiovascular events (MI and stroke) in postmenopausal women with a known history of cardiovascular disease, HRT remains an effective way to treat and alleviate vasomotor instability and reduce the risk of osteoporosis and bone fractures (particularly hip fractures). In addition, there is evidence to support that this effect, along with improvement in affect and mood stability, is long lived and persists during the course of therapy. The incidence of endometrial cancer appears to be reduced in those taking HRT. The use of HRT in those with risk factors for cardiovascular disease must be made on an individual case base, with carefully considering the risks versus the potential benefits of the intervention.

  The WHI study has demonstrated an added risk for developing cardiovascular events, such as MI and stroke, among those with known coronary disease or populations at high risk for CAD. A significant family history of CAD (father died at early age of an MI) would place this patient in the category of higher risk. Although patients taking HRT are at an increase risk for developing venous thromboembolism, this would not preclude its use unless the patient had a known history of the disease. The incidence of breast cancer in women on HRT remains controversial and, in our patient's case, we are told that there is a negative family history, hence making it less of a concern. Bloating and breast tenderness may develop in patients taking HRT, but its occurrence would not be a reason not to start therapy on our patient.

• Question 493:

  A 32-year-old woman presents with complaints of irritability, heat intolerance, hyperdefecation, and frequent palpitations. She has lost 20 lb over the past six months. She has always been in good health and does not take any prescription or OTC medications. She denies any prior history of thyroid disease or exposure to head/neck irradiation, but she states that one of her relatives was diagnosed with a thyroid disorder at roughly the same age. Vital signs are as follows: BP 138/78, HR 112, RR 22, temp.

  98.8. On examination, her thyroid is diffusely enlarged and smooth. Auscultation of the thyroid reveals a bruit. Her hair is fine in texture, and she has warm velvety skin. She has hyperactive deep tendon reflexes. There is a fine tremor in her outstretched hands.

  Which of the following sets of laboratory results would be consistent with this patient's presentation? TSH free T3 free T4

  A. low lowhigh
  B. low normal normal
  C. low high high
  D. highlow low
  E. high high high
  C. low high high

  ---

  Explanation

  This patient's presentation is consistent with Graves' disease. Infiltrative ophthalmopathy is a common finding in this condition. Approximately 2040% of patients with Graves' disease possess clinically evident eye disease. Complaints include photophobia, diplopia, reduced visual acuity, and easy tearing; and, signs of corneal or conjunctival irritation are oftentimes present. Periorbital edema, chemosis, lid retraction with restricted ocular movement, proptosis, and upward gaze impairment may also be found.

  Optic nerve compression may also arise, leading to decreased visual acuity, visual field defects, impaired color vision, and papilledema. Macroglossia, hyperkeratosis, cerebellar ataxia, and pericardial effusion are all findings in hypothyroidism. (Ceci Textbook of Medicine, pp. 13961400) Free T3 levels are elevated in all patients with Graves' disease. Most patients also have elevated free T4 levels, but occasionally this level will remain within the normal reference range in a state known as T3 toxicosis. This generally occurs during the initial phases of Graves' disease or at the onset of a relapse. TSH levels are suppressed by the elevated thyroid hormone levels.

• Question 494:

  A 4-year-old child is seen in the emergency department after having a seizure at home. This is the first time that this has happened. The mother says that the child was sitting on the couch watching television when she suddenly became limp, started drooling, and having generalized tonic-clonic movements of her arms and legs. The mother relates that the child felt like she was "burning up" and that the tonic- clonic activity stopped after a few minutes. The mother says that the child is otherwise healthy, does not take any medicines, and has never been hospitalized. The child's immunizations are up-todate, and she has no known drug allergies. On examination, the vital signs are temperature of 104, BP 97/49, HR 112, and RR 26. The child is sitting on the examination table playing with stickers and drawing. She has a mild amount of clear nasal congestion but her examination is otherwise normal. When asked, the child replies that she feels fine.

  What is the most likely diagnosis?

  A. bacterial meningitis
  B. first seizure in an epilepsy syndrome
  C. viral encephalitis
  D. typical febrile seizure
  E. hypocalcemic tetany
  D. typical febrile seizure

  ---

  Explanation

  Febrile seizures are the most common cause of seizures in childhood. These are classically seen early in an illness and when there is a rapid rise in the child's temperature. These seizures usually last less than 23 minutes (typical febrile seizures last no longer than 15 minutes) and have a very mild, short, postictal phase. Children who have seizures that are the result of bacterial meningitis will not subsequently be normal. For typical febrile seizures, in an otherwise healthy and well-appearing child, no evaluation (outside of treating any underlying cause of the fever) is warranted. Blood and urine cultures would not be necessary in evaluation of the seizures, but they may be warranted in evaluation of the fever. An EEG and head CT will nearly universally be normal and are unwarranted. A single typical febrile seizure routinely does not require any anticonvulsant therapy. If the child has had multiple febrile seizures, or the seizures are not typical, anticonvulsant therapy may be entertained. Prophylactic

  anticonvulsant therapy is usually initiated after the third febrile seizure. Occasionally, children may have convulsions associated with fevers which do not fall into the typical features. Some criteria which would make a febrile seizure atypical would be prolonged duration (greater than 15 minutes) and a prolonged postictal state

• Question 495:

  A 63-year-old male presents to your office with palpitations for the past 3 weeks. He has had no chest pains or dyspnea. He has no significant medical history and takes no medications. He does not smoke cigarettes and a recent lipid panel was normal. On examination, he is in no apparent distress. His pulse is 115 bpm and irregular. His BP is 125/77. His lungs are clear and his cardiac examination reveals an irregularly irregular rhythm with no murmurs, rubs, or gallops. Which of the following studies would be most appropriate to order at this time?

  A. radionuclide ventriculography
  B. exercise stress test
  C. echocardiogram
  D. cardiac catheterization
  E. electrophysiologic studies
  C. echocardiogram

  ---

  Explanation

  Atrial fibrillation is the most common sustained clinical arrhythmia. It occurs in approximately 4% of the population over the age of 60. It is diagnosed by the presence of irregularly irregular QRS complexes on an ECG with an absence of P waves. The QRS complex is most commonly narrow, as this is a supraventricular arrhythmia. Wide QRS complexes can occur if there is an underlying conduction abnormality, such as Wolff-Parkinson-White syndrome or a bundle branch block. Saw- tooth Pwaves occur in atrial flutter, another atrial arrhythmia that may present similarly to atrial fibrillation but which is less common. The saw-tooth P waves, or flutter waves, are representative of an atrial rate typically in the range of 300350/minute.

  Not infrequently, atrial flutter will lead to atrial fibrillation. Q waves in II, III, and aVF would be seen if there had been a previous inferior MI. Peaked T waves are seen in certain conditions, such as hyperkalemia, but are not routinely associated with atrial fibrillation. Atrial fibrillation may be precipitated by both cardiac and noncardiac conditions. Among the noncardiac conditions are metabolic abnormalities, which include hyperthyroidism. Of the tests listed, a suppressed TSH level, consistent with hyperthyroidism, would be most likely to be causative of atrial fibrillation. Troponin may be elevated in acute myocardial ischemia. Atrial fibrillation can occur following a MI, particularly when complicated by CHF. This is not consistent with the clinical scenario presented. Renal disease and diabetes may contribute to some of the conditions that can predispose to the development of atrial fibrillation, such as metabolic derangements or CAD. Acute and chronic pulmonary disease may also precipitate atrial fibrillation. In the setting of a man who is otherwise healthy and without significant medical history, new-onset atrial fibrillation would be less likely to be the initial presentation of diabetes, renal failure, or pulmonary disease than hyperthyroidism. For this reason, choice A is the single best answer of those provided.

• Question 496:

  You are seeing a 48-year-old female in followup in your clinic. She originally presented for evaluation of a suspicious nonpalpable lesion in her right breast that was seen on her annual mammogram. A stereotactic core biopsy was done. She now returns to your office to review the results of the pathology report that confirms the presence of lobular carcinoma in situ (LCIS).

  How do you counsel her at this time?

  A. Tamoxifen can prevent this cancer from spreading but may increase your risk of developing cancer in the other breast.
  B. You can consider nonoperative treatment with close observation, annual mammograms, and semiannual clinical examinations.
  C. The recommended treatment is a right breast mastectomy.
  D. Further staging workup at this time will include a chest x-ray and bone scan.
  E. Because you are at such high risk for future cancers, bilateral mastectomies should be performed to prevent this from happening.
  B. You can consider nonoperative treatment with close observation, annual mammograms, and semiannual clinical examinations.

  ---

  Explanation

  LCIS is a benign diagnosis and alone does not have a risk of progression to an invasive cancer. However, a diagnosis of LCIS does increase the risk for development of future breast cancer at a rate of about 1% per year. It is important to remember that the risk is increased for both breasts. It has been shown that chemoprevention with tamoxifen can decrease the incidence of breast cancer by 49%. It is also sufficient to follow this population closely with annual mammograms and semiannual clinical examinations. Prophylactic bilateral mastectomies are an option and result in a 90% decrease in the risk of subsequent breast cancer. Since a diagnosis of LCIS increases the risk of cancer in both breasts, a mastectomy of the affected side is insufficient treatment

• Question 497:

  You receive a call from the nurse at a nursing home for a 70-year-old patient of yours who was febrile overnight and had blood cultures, CXR, and urinalysis ordered by the housestaff. The patient was started empirically on a fluoroquinolone orally. The nurse informs you that the CXR and urinalysis were normal but the blood culture grew out Enterococcus faecalis. The patient has been on oral fluoroquinolone for 36 hours and patient is still febrile but appears stable. Which of the following is most appropriate?

  A. Continue the oral quinolone and add an intravenous first-generation cephalosporin.
  B. Discontinue the quinolone and start treatment with an intravenous thirdgeneration cephalosporin.
  C. Discontinue the quinolone and start treatment with intravenous ampicillin and an aminoglycoside.
  D. Continue the quinolone, but change from oral to IV route of administration.
  D. Continue the quinolone, but change from oral to IV route of administration.

  ---

  Explanation

  No cephalosporin is appropriate for the treatment of E. faecalis. This organism is occasionally sensitive to fluoroquinolones, but this choice is unreliable. The combination of ampicillin and an aminoglycoside is synergistic for susceptible E

• Question 498:

  One of your responsibilities at the community health center is to serve as director of the tuberculosis (TB) screening and prevention program.

  Which of the following test results would be considered positive?

  A. 10 mm redness and 3 mm induration in a man with HIV
  B. 10 mm redness and 10 mm induration in a nursing home resident
  C. 20 mm redness and 8 mm induration in a person with no known risk factors
  D. 5 mm redness and 5 mm induration in a physician having a routine, annual screening
  E. 10 mm redness and 5 mm induration in an immigrant from Southeast Asia
  B. 10 mm redness and 10 mm induration in a nursing home resident

  ---

  Explanation

  Current guidelines for TB control emphasize testing of those who are at high risk for the development of TB and who would benefit from the treatment of a latent TB infection, if detected. Based on that principle, testing is encouraged in those who are at high risk and discouraged among those who are at low risk. Further, anyone who is at high risk for the development of TB and who tests positive should be offered treatment, regardless of age. The preferred testing modality for asymptomatic persons of all ages is the intradermal (Mantoux) method of testing with PPD. Multiple puncture tests (e.g., Tine) are not sufficiently accurate and should not be used. The test should be read at 4872 hours and the diameter of induration, not redness, should be measured and recorded. Previous BCG vaccination is not a contraindication to skin testing and a positive skin reaction should be used as an indication of TB infection when the tested person is at increased risk for infection or has medical conditions that increase the risk of the disease. Delayed- type hypersensitivity reactions may wane over time. This is especially a problem in older individuals. Repeating a PPD placement may result in a "booster" phenomenon, in which a person who initially tests negative develops a positive reaction. This increases the overall sensitivity of the testing process. Three cutoff points for the determination of a positive test are currently in use: 5 mm of induration is used for those who are at the highest risk of disease, such as those immunosuppressed from HIV or medications, or those recently exposed to TB; 10 mm induration is used as a positive result for persons who have an increased probability of infection (such as immigrants from endemic areas), who have clinical conditions that increase the risk for TB (such as injection drug users) or who are residents or employees in high-risk settings (nursing homes, hospitals, prisons, and so on); 15 mm is used as a cutoff for those who Ignoring the amount of redness and using only induration as the criteria for have no known risk factors.

  positive or negative, the nursing home resident (option B) is the only one with a positive test. All persons who test positive by a skin test should then have a chest x-ray to evaluate for evidence of pulmonary TB. In an asymptomatic person, sputum studies are not necessary to determine the need for treatment. Pregnant women should still get a chest x-ray, with appropriate abdominal shielding, as soon as feasible. As stated above, a history of BCG vaccination should not deter from the need for further evaluation and treatment of a positive test result. Age should also not be a determining factor in treating someone who is at risk for the development of TB. Currently, there are four acceptable treatment recommendations for latent TB infections. Daily isoniazid for 9 months is the most widely used regimen and has the highest level of recommendation because of its effectiveness, relative safety, ease of administration, and low cost. Twice- weekly isoniazid may also be used but should only be given as directly observed therapy, due to the fact that a missed dose of this regimen represents a substantial risk of under treatment. Rifampin alone or rifampin plus pyrazinamide are alternative regimens for use in certain, specified situations.

• Question 499:

  A 17-year-old boy is reluctantly taken to the family medicine clinic by his mother, who is upset as "he is hanging out with the wrong crowd." She strongly believes that he has been smoking marijuana every day after school and on weekends with his friends. The patient appears irritated about the appointment but denies using any drugs or alcohol. His mother would like him to be counseled about the potential dangers of "smoking pot."

  Which of the following physical effects would be most consistent with cannabis intoxication?

  A. decreased respiration
  B. increased salivation
  C. decreased appetite
  D. normal motor function
  E. tachycardia
  E. tachycardia

  ---

  Explanation

  Cannabis is one of the few substances of abuse that does not affect the respiratory rate. Consuming marijuana classically produces symptoms of a dry mouth and increased appetite (the munchies). Contrary to what is sometimes claimed, intoxication with cannabis does significantly impair motor function and, therefore, interferes with driving ability. It also can cause tachycardia (DSM IV- TR). Amotivational syndrome is a potential, but controversial, long-term effect of heavy cannabis use. It is characterized by apathy and boredom. Cerebral atrophy, chromosomal damage, and seizures have also been reported, but not confirmed, in individuals with chronic cannabis use. The most concerning medical consequences of smoking cannabis over the long term are similar to those from smoking tobacco, such as lung cancer and respiratory disease.

• Question 500:

  A50-year-old man undergoes a sigmoid colectomy and colostomy for perforated diverticulitis of the midsigmoid colon. The surgeon reports a difficult dissection in the pelvis secondary to adhesions of the sigmoid colon to the abdominal wall. On postoperative day 1, the patient reports appropriate abdominal pain. His pulse is 100 and BP 120/60. He has made 400 mL of urine over the past 8 hours. The urine in the Foley bag is blood-tinged.

  He reports no problems with his urination preoperatively. What is the appropriate management?

  A. Remove the Foley catheter. The irritation of the catheter is probably causing the hematuria.
  B. Increase his IV fluids and add bicarbonate in case this is rhabdomyolysis.
  C. Start antibiotics for a urinary tract infection.
  D. Order an intravenous pyelogram to assess for ureteral injury.
  E. Send a prostate-specific antigen (PSA) to screen for a prostatic process.
  D. Order an intravenous pyelogram to assess for ureteral injury.

  ---

  Explanation

  Ureteral injuries are a well-known complication of pelvic surgery. The risk is greatly increased in the setting of inflammation, which can make the ureters difficult to identify. Intravenous pyelogram is a sensitive test for injury. CT scan and retrograde pyelogram are also diagnostic options. Injuries identified early are usually amenable to primary surgical repair, making early diagnosis essential. Delayed recognition usually results in a staged repair requiring urinary diversion with percutaneous nephrostomy tubes.