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

USMLE USMLE-STEP-2 Online Questions & Answers

• Question 501:

  Select the ONE best lettered option that is the most likely diagnosis of vaginal bleeding in pregnancy. Each lettered option may be selected once, more than once, or not at all. A 31-year-old woman has an uncomplicated labor and vaginal delivery of a healthy 3400-g male infant. However, her placenta has not yet delivered 2 hours after the delivery of her child. Under appropriate anesthesia manual extraction of the placenta is attempted, but the placenta is removed in fragments. She continues to have excessive vaginal bleeding after manual removal of her placenta. Her first child was delivered by a low transverse cesarean section because of fetal distress.

  A. threatened abortion
  B. gestational trophoblastic disease
  C. cervicitis
  D. placenta previa
  E. placental abruption
  F. uterine rupture
  G. placenta accreta
  H. uterine inversion
  I. uterine atony
  J. vaginal lacerationK. tubal pregnancy
  G. placenta accreta

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  Explanation

  Placenta accreta is suggested by the difficulty with manual removal of the placenta in a woman with a prior cesarean section. Placenta accrete is also more common over any previous uterine incision, such as a myomectomy. Placenta accrete is also more common in women with placenta previa and there is greater than an eightfold increase in women with an AFP higher than 2.5 MOM. The safest and most appropriate treatment is a hysterectomy.

• Question 502:

  A 65-year-old woman presents to the physician's office for evaluation of an abnormal screening mammogram. She denies any breast masses, nipple discharge, pain, or skin changes. Past history is pertinent for hypertension. Family history is positive for postmenopausal breast cancer in a sister. She has a normal breast examination and no axillary adenopathy. The remainder of her examination is unremarkable. An MLO view of the right breast is shown in Figure along with a magnification view of the craniocaudal (CC) film

  

  

  

  Which of the following is the most likely diagnosis?

  A. milk of calcium
  B. LCIS with or without an invasive component
  C. DCIS with or without an invasive component
  D. involuting fibroadenoma
  E. phyllodes tumor
  C. DCIS with or without an invasive component

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  Explanation

  The mammographic appearance is most consistent with DCIS with or without an invasive component. The calcifications of DCIS are clustered, pleomorphic, irregular, and linear, and may be associated with a mass representing an invasive carcinoma. LCIS does not usually present with calcifications. Cystosarcoma phyllodes presents as a mass, often indistinguishable from a fibroadenoma. An involuting fibroadenoma often presents as a mass with large, coarse calcifications, indicating its benignity. Milk of calcium will often layer differently in the CC and mediolateral projections, suggesting fluid with calcium. The next step in management is to obtain a biopsy, preferably a core needle biopsy, for histologic confirmation and to evaluate for invasive disease. Observation is not recommended because these calcifications appear malignant. All other choices (i.e., lumpectomy or total mastectomy) are not indicated until a diagnosis by biopsy is obtained.

• Question 503:

  Select the ONE best lettered option that is the most likely diagnosis of vaginal bleeding in pregnancy. Each lettered option may be selected once, more than once, or not at all.

  A 29-year-old pregnant woman at 38 weeks' gestation presents to your labor and delivery unit complaining of dizziness, heavy vaginal bleeding, and loss of fetal movement. She had been having uterine contractions for approximately 4 hours, but these stopped when the bleeding began. Her previous pregnancy was delivered by classical cesarean section because of a transverse lie.

  A. threatened abortion
  B. gestational trophoblastic disease
  C. cervicitis
  D. placenta previa
  E. placental abruption
  F. uterine rupture
  G. placenta accreta
  H. uterine inversion
  I. uterine atony
  J. vaginal lacerationK. tubal pregnancy
  F. uterine rupture

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  Explanation

  The clinical features that make uterine rupture the most likely diagnosis are profuse bleeding coincident with cessation of uterine contractions and labor in a woman with a prior classical cesarean section (vertical incision in the uterine fundus). Uterine rupture is uncommon in women with a prior low transverse cesarean section and rare in women with no scar on her uterus. The standard of care is that all women with a previous classical cesarean section be delivered by repeat cesarean section at term before the onset of labor.

• Question 504:

  For each of the following scenarios, select the gas exposure responsible for the signs and symptoms. A garage worker turns on the ventilation system in the winter time while testing a motor, and now complains of a headache and vertigo

  A. carbon monoxide
  B. methane
  C. hydrogen sulfide
  D. ozone
  E. sulfur dioxide
  C. hydrogen sulfide

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  Explanation

  Carbon monoxide is an odorless, colorless, tasteless gas produced by partial combustion of tobacco and fuels. The amounts produced by cigarette smoking are not insignificant. The gas combines with hemoglobin preferentially to form carboxyhemoglobin, which makes the patient appear pink. This diminishes the oxygen-carrying capacity of the blood. The resulting anoxia is the major hazard. The onset of symptoms is insidious. Individuals exposed to carbon monoxide may not voluntarily take the action necessary to remove themselves from the toxic fumes

• Question 505:

  A 25-year-old woman has a positive cervical culture for Neisseria gonorrhoeae. She has had at least two positive cultures for gonorrhea treated in the past. She is afebrile and has no symptoms. The incidence of penicillin-resistant gonorrhea in some areas of the United States is currently as great as 10%. Because of this, the recommended treatment for gonorrhea includes which of the following?

  A. 125 mg intramuscular ceftriaxone as a single dose
  B. 1 g spectinomycin
  C. 2 g ampicillin orally as a single dose
  D. 2 g intramuscular cefoxitin
  E. 2 g metronidazole as a single dose
  A. 125 mg intramuscular ceftriaxone as a single dose

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  Explanation

  The current treatment guideline from the Centers for Disease Control and Prevention for uncomplicated gonococcal infections is ceftriaxone 125 mg IM one time. Cefixime 400 mg orally is an alternative. Each is given as a single dose. Importantly, the quinolone class, for example, ciprofloxacin is no longer considered appropriate treatment for gonococcal infections due to drug resistance. To the chosen drug is added azithromycin, 1 g orally, or doxycycline, 100 mg orally twice daily for 7 days. The second drug is added to treat C. trachomatis, which is present in almost 50% of women with gonorrhea. Sexual partners should be treated at the same time

• Question 506:

  A 35-year-old woman is seen by her primary care physician for a physical examination. She tells him she has a twin brother who has bipolar disorder and has been worried that she will develop it. Which of the following would be most helpful for her to hear?

  A. "You're past the age when bipolar disorder develops, so don't worry about it."
  B. "There is no clear evidence that a bipolar disorder is genetically determined."
  C. "The concordance rate for bipolar disorder for dizygotic twins is 19%."
  D. "The concordance rate for bipolar disorder for dizygotic twins is 79%."
  E. "Prophylactic treatment with lithium is advisable."
  C. "The concordance rate for bipolar disorder for dizygotic twins is 19%."

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  Explanation

  There is strong evidence for a genetic predisposition to bipolar disorder. Some of the evidence comes from twin studies. The concordance rate for monozygotic twin is 79%, but for dizygotic twin it is 19%. Advising the patient that she is past the age when bipolar disorders develop, using lithium to prevent the disorder, or saying that no genetic link has been determined is very misleading and clinically incorrect.

• Question 507:

  A2-year-old child is brought to the emergency department with sudden onset of nresponsiveness, miosis, bradycardia, and muscle fasciculations. These findings are most suggestive of poisoning with which of the following?

  A. acetaminophen
  B. organophosphates
  C. salicylates
  D. tricyclic antidepressants
  E. vitamin A
  B. organophosphates

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  Explanation

  Organophosphate poisoning is a leading cause of fatal ingestions of nonpharmaceutical compounds. Common components of insecticides, organophosphates are readily absorbed across skin and mucous membranes. They bind irreversibly to cholinesterase, which results in prolongation of the effects of acetylcholine, centrally and peripherally. Symptoms include muscle fasciculations, paralysis (nicotinic effect) and miosis, salivation, diarrhea, bradycardia, lacrimation (muscarinic effect) and obtundation, seizures, or apnea (central effect).

  Acetaminophen ingestion can present with vomiting and then later signs of liver failure if it is severe enough. Patients with salicylate overdose present with hypoglycemia, respiratory alkalosis followed by metabolic acidosis, hypokalemia, and mental status changes. Tricyclic antidepressants poisoning causes arrhythmias, mental status changes, and anticholinergic symptoms. Patients with acute vitamin Atoxicity have mental status changes, nausea, and vomiting.

• Question 508:

  Schedules for the routine immunization of young children are developed jointly by the Advisory Commission on Immunization Practices (a federal commission) and the American Academy of Pediatrics. Which of the following vaccines is recommended for routine vaccination for all children in the United States?

  A. anthrax vaccine
  B. rabies vaccine
  C. Haemophilus influenzae b (Hib) vaccine
  D. hepatitis A vaccine
  E. typhoid vaccine
  C. Haemophilus influenzae b (Hib) vaccine

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  Explanation

  Hib vaccine is recommended for routine immunization of children. Introduction of the Hib conjugate vaccine in the late 1980s was followed by a spectacular decrease in the incidence of H. influenzae meningitis. Anthrax vaccine is used to vaccinate military troops in selected overseas deployment. Rabies vaccine is used for postexposure prophylaxis when children are bitten by potentially rabid mammals. Hepatitis Avaccine is used for children at special risk of such infection. Typhoid vaccine is not routinely recommended for use in the United States but may be indicated for travelers to areas in the developing world where typhoid fever is endemic.

• Question 509:

  For each of the following scenarios, select the gas exposure responsible for the signs and symptoms. A patient working with an electric arc noted a pungent odor, and now has signs of asthma or early pulmonary edema.

  A. carbon monoxide
  B. methane
  C. hydrogen sulfide
  D. ozone
  E. sulfur dioxide
  D. ozone

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  Explanation

  Ozone is a colorless, pungent gas occurring naturally in the stratosphere, which can be produced by electric arcs. Ozone is generated by electrical storms and UV light and electric arcs and some forms of fuel combustion. In the stratosphere, it is protective by blocking solar radiation. At 10 ppm, it can cause pulmonary edema and tracheal pain and is believed to cause asthma. Based on animal tests and observations of gases trapped during inversions, an action level of 10 ppm has been set for work-place exposure.

• Question 510:

  A 58-year-old woman with a history of chronic paranoid schizophrenia, who has been continuously treated with antipsychotics for the past 20 years, lives in a community-based residential facility. She has recently suffered an increase in auditory hallucinations, and her haloperidol dose has been increased from 2.5 to 10 mg/day. Four days later, she is brought by a visiting nurse to the emergency room, where she presents with confusion, marked flexor and extensor rigidity in her legs and arms, and a temperature of 103.5°F. Her blood pressure is160/120 mmHg, her pulse is 120/min and irregular. Which of the following is the most important laboratory test to evaluate the possibility of the diagnosis?

  A. serum creatine phosphokinase (CPK) level
  B. serum sodium level
  C. serum potassium level
  D. serum glucose level
  E. serum calcium level
  A. serum creatine phosphokinase (CPK) level

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  Explanation

  Patients with NMS typically demonstrate tachycardia, labile blood pressure, severe muscle rigidity, and severe fever. Serum CPK levels, which can be elevated to more than 100 times normal levels as a result of muscle damage, are the most consistently noted abnormalities in patients with NMS. Although the white blood cell count may be elevated, and blood levels of calcium, iron, and magnesium may be decreased in patients with the syndrome, serum CPK is the most important laboratory study to obtain in a patient with suspected NMS