USMLE USMLE-STEP-2 Online Practice Questions and Exam Preparation

USMLE USMLE-STEP-2 Online Questions & Answers

• Question 571:

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

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  Explanation

  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 572:

  A 65-year-old man presents to the emergency department with an abrupt onset of excruciating chest pain 1 hour ago. The pain is localized to the anterior chest, but radiates to the back and neck. On examination, the patient is afebrile, with a BP of 210/110 mmHg, pulse rate of 95/min, and a respiratory rate of 12/min. He appears pale and sweaty. Unequal carotid, radial, and femoral pulses are noted. An electrocardiogram (ECG) shows nonspecific ST-T segment changes. Chest x-ray shows a slightly widened mediastinum and normal lung fields.

  Which of the following is the preferred modality in establishing the diagnosis?

  A. transcutaneous echocardiography
  B. transesophageal echocardiography
  C. CT scan
  D. coronary angiography
  E. aortography
  B. transesophageal echocardiography

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  Explanation

  The diagnosis of an aortic dissection is strongly suggested by the history of an abrupt onset of excruciating pain in the chest and back with variable radiation patterns, and a hypertensive, illappearing patient. A chest x-ray showing a widened mediastinum may be noted, but the radiograph may be normal. The differential diagnosis of an acute myocardial infarction must be entertained and an ECG performed. Though aortography has historically been the definitive diagnostic procedure and may be required in some patients, transesophageal echocardiography has become the preferred diagnostic modality. It can be performed in the emergency department, thus obviating the need to move an extremely ill patient. CT scan may also be helpful in establishing the diagnosis. Immediate drug therapy to control hypertension is mandatory, followed by definitive therapy, depending on the type of dissection. Involvement with the ascending aorta mandates immediate surgical repair. Dissections involving only the descending aorta can be managed medically, initially.Thrombolytic therapy and anticoagulation are not indicated and may precipitate exsanguination.

• Question 573:

  You have decided to survey the population to establish a health risk profile for the population. Due to budget constraints, you must gather data using a stratified random sample. This approach is correctly described as which of the following?

  A. based on selecting individuals from a list at predetermined intervals (every ith individual)
  B. random sampling of separate segments of a population
  C. randomly grouping the population
  D. sampling a cluster of individuals
  E. removing outliers and sampling from remainder of group
  B. random sampling of separate segments of a population

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  Explanation

  Sometimes it is possible to identify subgroups or strata of a population. Randomly sampling these segments, called strata, may reduce sampling error. Systematic sampling, selecting every "ith" individual, is not necessarily random, depending on how lists are constructed. Random groups would presumably be based on random selection of individuals, and little benefit would derive from studying such groups. Random groups produce more hazards statistically than randomized strata. Clusters are somewhat different; they may be small groups of the population occurring in specific areas, such as families, villages, or wards. The characteristics of clusters are not necessarily those of the population, but more those of location. Cluster sampling may be useful but does not have the same outcome as a stratified sample.

• Question 574:

  The following questions identify health care planning methods used by various organizations. The answer options are strategies that may correspond to these methods. Select the strategy that best corresponds to each health care planning method.

  A maternal and child health care system employs program-based planning to address its goals.

  A. identifying what the market for services are and estimating future demands
  B. identifying mechanisms for carrying out established goals within specific program areas
  C. identifying financial resources to meet community needs
  D. identifying barriers to growth and the resources needed to overcome them
  D. identifying barriers to growth and the resources needed to overcome them

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  Explanation

  Program planning concerns itself with neither the fiscal need for a particular service nor its marketability. By definition, "the program" (e.g., maternal and child health care) will be developed and provided as directed by the state or local government. The planning is directed to carry out program goals for a targeted (select) population (pregnant women and their infants). This type of planning is necessary to implement government or private foundation-sponsored programs.

• Question 575:

  An 11-month-old girl presents to your office with a fever of 39°C she has had for 2 days. She has also vomited frequently and had decreased fluid intake. She looked tired and ill but on examination, had no apparent source of infection. She appeared to be 510% dehydrated.

  You decide to obtain a urine specimen for analysis and culture. Which of the following is the best method?

  A. Collect a midstream "clean catch" specimen.
  B. Collect a catheterized specimen.
  C. Place an adhesive bag to collect urine.
  D. Obtain urine from a diaper.
  E. Collect urine after she urinates in a potty chair.
  B. Collect a catheterized specimen.

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  Explanation

  Urine for urinalysis and culture must be properly obtained. Catheterization is the most reliable method of the choices offered. Suprapubic tap is considered the "gold-standard" but is not always technically feasible, especially in an outpatient office setting. Amidstream, clean catch specimen would be acceptable in an older, toilet-trained child. "Bagged" specimens are not recommended because of possible skin or fecal contamination of the specimen. Similarly, obtaining a sample from a diaper or potty would be unacceptable. Urinalysis includes dipstick method and microscopic examination. Leukocyte esterase (an enzyme in WBC) and nitrites suggest probable infection. Microscopic analysis of unspun urine for WBC (>10/ highpower field) or bacteria is also predictive of infection. RBCs are often present in a UTI. The patient is vomiting and dehydrated; this may indicate possible pyelonephritis. The most appropriate course would be IV hydration and empiric treatment with antibiotics (ceftriaxone) while awaiting cultures. Children with pyelonephritis are at increased risk of renal scarring, especially younger children, and should be treated early. E. coli is the most common organism cultured; others include Proteus, Klebsiella, S saprophyticus, and Enterococcus. The occurrence of a UTI in a girl under age 35 years and in a boy of any age may be a marker for an underlying congenital anatomic abnormality, in particular, vesicourethral reflux. Radiologic investigation with renal ultrasound and VCUG is recommended

• Question 576:

  A 65-year-old man presents to the emergency department with sudden onset of pain and weakness of the left lower extremity of 2-hour duration. Past history reveals chronic atrial fibrillation following a myocardial infarction 12 months ago. On examination, he is found to have a cool, pale left lower extremity with decreased strength and absent popliteal and pedal pulses. The opposite leg has a normal appearance with palpable pulses.

  Which of the following is the treatment of choice for this patient?

  A. r-TPA (tissue plasminogen activator) infusion following anticoagulation
  B. administration of vasodilators
  C. four-compartment fasciotomy
  D. thromboembolectomy
  E. anticoagulation and close observation
  D. thromboembolectomy

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  Explanation

  The diagnosis of arterial embolism is suggested when the patient presents with an acute onset of severe pain, pallor, pulselessness, paresthesia, and paralysis (five P's). The presence of atrial fibrillation is strongly suggestive of a cardiac source of the emboli. The first step in management is immediate heparinization to prevent propagation of the clot and maintain patency of collaterals. The cornerstone of treatment is thromboembolectomy. Thrombolytic therapy is reserved for treatment of irretrievable clots in small vessels. Fasciotomy, alkalinization of the urine, and mannitol diuresis are adjuncts to treatment, particularly if there is a delay in operation, increasing the risk of a reperfusion injury. Anticoagulation has been shown to reduce the rate of recurrent embolism.

• Question 577:

  A 65-year-old man presents to the physician's office for his yearly examination. His past history is pertinent for a 40 pack-year smoking history and colon cancer 3 years ago for which he underwent a sigmoid colectomy. The most recent colonoscopic follow-up 3 months ago was negative. His physical examination is normal. Laboratory results show a normal CBC and electrolytes, markedly elevated cholesterol, and a CEA of 12 compared to values of less than 5 obtained every 6 months since colectomy. A repeat CEA 4 weeks later was 15, and liver function tests revealed a minimally elevated alkaline phosphatase, with normal transaminases and bilirubin. In your discussion with the patient regarding the risks and benefits of the different management options listed above, which of the following values should you quote regarding the expected 5-year survival rate following curative surgical resection?

  A. 510%
  B. 1520%
  C. 2535%
  D. 4050%
  E. 6070%
  C. 2535%

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  Explanation

  In a patient who has undergone surgical resection for colon cancer, elevated CEA, and liver function tests must be followed by an evaluation for metastatic disease, including the possibility of extrahepatic disease. The CT scan is the most useful examination to evaluate both intra- and extrahepatic disease. Various CT scans have been advocated for liver tumors, including dynamic and portography scans. PET scans may detect occult extrahepatic disease and studies are underway to define the role of this modality in metastatic colon cancer. MRI shows promise as a useful examination and can be useful to characterize lesions of uncertain significance. Radionuclide liver scans have been supplanted by more accurate scans. Surgical resection, if possible, is the treatment of choice for metastatic colorectal cancer to the liver. Chemotherapy is reserved for patients who are not surgical candidates or refuse surgical treatment. Radiation therapy is not usually used in these patients. Observation and repeat imaging delays the treatment for patients who may be respectable. The expected 5-year survival has been shown in multiple studies to be greater than 20%, usually in the range of 25 and 35%.

• Question 578:

  A new screening test for prostate cancer becomes available. You assess whether this will be useful to your practice by reviewing the operating characteristics of the test. The test's ability to correctly classify diseased persons as having disease is called what?

  A. specificity
  B. sensitivity
  C. positive predictive value
  D. negative predictive value
  E. reproducibility
  B. sensitivity

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  Explanation

  By definition, sensitivity is the probability of testing positive if the disease is truly present. It indicates the percentage of persons with the disease of interest who have positive test results. Positive predictive value estimates the probability of disease in those who have positive test results. It indicates the percentage of persons with positive test results who actually have the disease of interest.

• Question 579:

  A 65-year-old woman presents to the physician's office for a second opinion on the management options for recently diagnosed breast cancer. She presents with a 2.5-cm mass in the upper outer quadrant of the left breast associated with a palpable axillary node suspicious for metastatic disease. The remainder of her examination is normal. Mammography demonstrates the cancer and shows no other suspicious lesions in either breast. Chest x-ray, bone scan, and blood test panel, including liver function tests, are normal. Family history is positive for breast cancer diagnosed in her sister at age 65. Past history is unremarkable. The first physician recommended modified radical mastectomy. The patient has read about SLN biopsy. She avidly wants to avoid the risk of lymphedema that her sister must endure. She asks the question "Am I a candidate for a SLN biopsy instead of a complete axillary dissection?"

  Which of the following is the most appropriate answer to her question?

  A. Yes, and if the SLN if positive, then a complete axillary dissection should be performed.
  B. Yes, and if the SLN is negative, then an axillary dissection can be avoided.
  C. No, because the success of SLN biopsy in patients over age 60 is decreased.
  D. No, because SLN biopsy is contraindicated when a palpable axillary node issuspicious for metastatic disease.
  E. No, because SLN biopsy is contraindicated for tumors greater than 2 cm.
  D. No, because SLN biopsy is contraindicated when a palpable axillary node issuspicious for metastatic disease.

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  Explanation

  Prospective randomized trials have addressed the issue of locoregional control of breast cancer. Conservative management consisting of lumpectomy (with negative margins), irradiation, and axillary node dissection is equally effective as modified radical mastectomy in patients with clinical stage I or II breast carcinoma. Although radical mastectomy yields equivalent survival to modified radical mastectomy, it is disfiguring and disabling and is rarely employed for treatment of primary operable breast cancer.

  Lumpectomy without irradiation leads to unacceptably high local recurrence rates. Irradiation without surgery is not as effective as surgery in the presence of gross disease. Quadrantectomy removes excessive tissue and leads to an inferior cosmetic result as compared to lumpectomy. If quadrantectomy is thought to be required to gain negative margins, mastectomy with reconstruction should be entertained. The use of SLN biopsy to stage the axilla in breast cancer is gaining wider acceptance as experience with the procedure grows. Trials are ongoing that will answer numerous questions regarding the accuracy and efficacy of SLN biopsy for breast cancer. There are contraindications to SLN biopsy that include palpable adenopathy that is suspicious for metastatic disease, locally advanced disease or tumor size >5 cm, multicentric disease, pregnant or lactating patient, and use of preoperative chemotherapy. Therefore, in this patient with palpable suspicious adenopathy, SLN biopsy would be contraindicated. Although age may influence success of SLN biopsy, increasing age does not preclude the procedure.

• Question 580:

  A62-year-old man presents with weakness and aching in his hips and shoulders which has progressed over the last few months. He reports generalized fatigue and malaise. Workup includes a normal complete blood count, kidney and liver tests, and a sedimentation rate of 102. Which of the following is the most likely diagnosis?

  A. SLE
  B. diabetes
  C. Wegener's granulomatosis
  D. polymyalgia rheumatica
  E. Graves' disease
  D. polymyalgia rheumatica

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  Explanation

  Polymyalgia rheumatica is characterized by bilateral aching and stiffness of the proximal parts of the arms and thighs with associated weakness and generalized fatigue. The sedimentation rate typically is significantly elevated. This condition can coexist with the syndrome of temporal arteritis (aka giant cell arteritis) which is a chronic vasculitis of largeand medium-sized vessels, usually including cranial branches of the aortic arch arteries. Common symptoms among patients with overlapping temporal arteritis are headache and sudden loss of vision. Graves' disease is an autoimmune thyroid disease and Wegner granulomatosis typically involves the sinuses, lungs, and/or kidneys.