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

USMLE USMLE-STEP-2 Online Questions & Answers

• Question 521:

  A 23-year-old pregnant woman at 5 postmenstrual weeks took coumadin until about 3 days after her menses was due. She has monthly menses. A home pregnancy test was positive on the day she took coumadin. She takes coumadin because of a history of deep vein thrombosis and pulmonary embolism. She is concerned that the coumadin will cause birth defects.

  You advise this woman to do which of the following?

  A. Abort the pregnancy because the fetus is likely to have birth defects.
  B. Have an ultrasound in 12 weeks to search for fetal anomalies.
  C. Have a genetic amniocentesis at 16 postmenstrual weeks.
  D. Begin prenatal care because the probability of birth defects is low.
  E. Take 10 mg vitamin K to reverse the effects of coumadin.
  D. Begin prenatal care because the probability of birth defects is low.

• Question 522:

  A 2-year-old girl presents with fever of 39.3°C and irritability. She has had an upper respiratory tract infection for 4 days. On examination, the right ear is bulging and has poor movement on insufflation. Which of the following organisms is most likely responsible for these findings?

  A. S. pneumoniae
  B. S. aureus
  C. M. pneumoniae
  E. group A Streptococcus
  A. S. pneumoniae

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  Explanation

  Nontypeable H. influenzae, S. pneumoniae, and M. catarrhalis are the most common bacterial pathogens in otitis media of children. S. aureus, E. coli, and group A Streptococci each account for 2% or less of all cases of otitis media in children beyond the neonatal period. Mycoplasma is thought to be an uncommon cause of otitis media

• Question 523:

  A 6-month-old infant is diagnosed with her first episode of otitis media. She does not have any allergies to medications. Which of the following medications would be the recommended initial therapy for this infant?

  A. amoxicillin
  B. amoxicillin-clavulanic acid
  C. cephalexin
  D. ceftriaxone
  E. erythromycin
  A. amoxicillin

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  Explanation

  H. influenzae,

  S. pneumoniae, and Moraxella catarrhalis are the most common bacterial pathogens in otitis media of children. Amoxicillin is still the initial drug to use in uncomplicated otitis media because of its good coverage, except for beta-lactamase-positive organisms, and its excellent safety profile. The other drugs (except for erythromycin) are acceptable second-line medications

• Question 524:

  A44-year-old secretary presents with a fever of 103°F, headache, and stiff neck. You entertain a diagn osis of bacterial meningitis and begin antibiotics immediately. With bacterial meningitis, which of the following is a likely finding in the cerebrospinal fluid (CSF)?

  A. leukocytes between 100 and 500/mm
  B. CSF pressure between 100 and 120 mmH2O
  C. negative Gram stain
  D. glucose >120 mg/dL
  E. protein levels >45 mg/dL
  E. protein levels >45 mg/dL

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  Explanation

  The Gram stain is positive in three-fourths of bacterial meningitis cases. Leukocyte counts average between 5000 and 20,000; CSF pressure is consistently elevated usually above 180 mmH2O; glucose levels are usually lower than 40 mg/dL, or less than 40% of blood glucose; and protein levels are higher than 45 mg/dL in 90% of cases

• Question 525:

  Which regulatory agency has the authority to control the use of pesticides in the United States?

  A. Food and Drug Administration (FDA)
  B. United States Department of Agriculture (USDA)
  C. Environmental Protection Agency (EPA)
  D. United Nations Food and Agriculture Organization (FAO)
  E. World Health Organization (WHO)
  C. Environmental Protection Agency (EPA)

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  Explanation

  In the United States, the organization of food and water control is complex. Among the federal control agencies, the EPA is the most recent, and in many ways the most active and powerful. This agency has now set up an elaborate system of regulation and control of the use of pesticides (which until 1970 was the responsibility of the USDA) and has banned the marketing of chlorphenothane (DDT) for use in the home. The FDA has authority to remove food from the market if it contains pesticides (e.g., PCBs in fish) in excess of the action levels set by the EPA. The FDA also retains the authority to remove from the market any food with inappropriate additives, that contains substances harmful to human health, that is stored in unsanitary conditions, that has decomposed, or that is not fit for consumption.

  The USDAenforces wholesomeness standards that it sets for the production and sale of meat. International control is assisted by the WHO. This agency has mounted control programs for the eradication of communicable disease with conspicuous success in the case of smallpox. It also publishes the International Statistical Classification of Disease (ICD-9).

• Question 526:

  You participate in the global effort to eradicate poliomyelitis. A poliomyelitis outbreak has been identified in a community in Africa. You advise your outbreak investigation team that they must focus on transmission from which one of the following sources?

  A. green monkeys
  B. mosquitoes of the species Aedes aegypti
  C. contaminated vaccine
  D. polluted water sources
  E. poorly cooked food
  D. polluted water sources

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  Explanation

  The poliovirus is excreted in stools and pharyngeal secretions. Transmission occurs mainly by the fecal- oral route, particularly where sanitation and personal hygiene are poor, as in developing countries. The WHO, with the assistance of Rotary International, is progressing toward global eradication. There is no known reservoir for poliovirus except humans. By 2000, the Americas were polio free.

• Question 527:

  A23-year-old woman develops painful vulvar vesicles that contain intranuclear inclusions on cytologic examination. She is 22 weeks' pregnant. Which of the following statements about genital herpes is correct?

  A. Acyclovir should be prescribed from 36 gestational weeks until after delivery in women with primary herpes anytime during pregnancy.
  B. Herpes cultures from the cervix should be obtained weekly beginning at 36 weeks' gestation.
  C. An active genital herpetic lesion any time after 20 weeks' gestation requires a cesarean section.
  D. Intrauterine infection with herpes is common after 20 weeks in women with primary herpes.
  E. Pitocin induction of labor should be started within 4 hours after ruptured amniotic membranes in a woman at term with active genital herpes.
  A. Acyclovir should be prescribed from 36 gestational weeks until after delivery in women with primary herpes anytime during pregnancy.

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  Explanation

  Acyclovir prescribed from 36 gestational weeks until after delivery reduces the probability of a cesarean section, although in one study of a small number of patients there were no cases of neonatal herpes in either the treatment or control group. Nonetheless, acyclovir (a class C drug) and newer antiviral drugs (valacyclovir, famciclovir, both class B) should be given to women with either a primary outbreak or a recurrence during pregnancy. Weekly cultures are unreliable to exclude active herpes lesions in pregnancy and are not recommended for basing a decision to perform a cesarean section. A cesarean section should be performed if a woman develops an active cervical or vaginal lesion at term. However, genital herpetic lesions before 36 weeks do not necessitate a cesarean section, because there is no evidence that vertical transmission to the fetus is increased until the pregnancy is within 24 weeks of delivery. Intrauterine infections via transplacental or transmembrane transmission of the herpesvirus are rare. Most infections of the infant occur after passage through an infected birth canal. A cesarean section should be performed at term if the amniotic membranes rupture in a woman with an active herpetic lesion in the genital area, regardless of the duration of membrane rupture.

• Question 528:

  For each newborn with vomiting and illustrated radiographs, select the most likely diagnosis. A1-day- old infant with Down syndrome, feeding intolerance, bilious vomiting, and a double bubble on plain radiographs

  A. congenital hypertrophic pyloric stenosis
  B. annular pancreas
  C. duodenal atresia
  D. midgut volvulus
  E. intussusception
  F. imperforate anus
  G. Meckel's diverticulum
  H. meconium ileus
  I. Hirschsprung's disease
  J. jejunal atresia
  C. duodenal atresia

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  Explanation

  Pyloric stenosis presents with nonbilious vomiting and gastric distention. An annular pancreas does not result in obstruction, except when it is associated with an underlying duodenal abnormality. Duodenal atresia is associated with Down syndrome. It results in early onset of bilious vomiting from complete duodenal obstruction distal to the ampulla. There is a "double bubble" sign on plain abdominal radiographs from air in the stomach and proximal duodenum. Midgut volvulus is a life-threatening complication of malrotation. It presents with acute onset of bilious vomiting, usually in infants in the first year of life. There is a paucity of gas on plain radiographs, with evidence of duodenal obstruction. UGI contrast study will confirm the abnormal position of the duodenaljejunal junction and may demonstrate a corkscrew of the duodenum from volvulus. Intussusception is uncommon in newborns. Bilious vomiting is unusual at the outset, but may develop if the intussusception has been present for a significant time.

  Imperforate anus can be excluded by clinical examination.

  If unrecognized, the infant will develop a clinical picture of a distal bowel obstruction, with dilated small and large bowel. Meckel's diverticulum can present with obstruction secondary to volvulus around a Meckel's band, with a distal small-bowel obstruction. Contrast enema will demonstrate a normal-caliber decompressed colon, with proximal dilated small bowel. Meconium ileus is associated with cystic fibrosis. Obstruction occurs from inspissated meconium in the terminal ileum. Plain radiographs may demonstrate a "soap bubble" pattern in the right lower quadrant, with a decompressed colon on contrast enema. Hirsch- sprung's disease presents with a distal bowel obstruction and delayed passage of meconium. A contrast enema may demonstrate a transition zone, with a narrow distal aganglionic segment, and proximal colonic dilatation. Jejunal atresia is a result of an intrauterine vascular accident. Infants present with bile- stained vomiting and abdominal distention early after birth. The colon is unused, and characteristically, on contrast enema, it is abnormally small in caliber

• Question 529:

  For each of the following scenarios, select the gas exposure responsible for the signs and symptoms.

  A sewer worker has acute onset of nausea, headache, and shortness of breath, and has anosmia.

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

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  Explanation

  Hydrogen sulfide is a colorless gas that rapidly paralyzes the nasal receptors, and is found in sewers. Hydrogen sulfide produces nausea, headache, and shortness of breath. Because it paralyzes the nasal receptors at a concentration of 150 ppm and cannot be smelled shortly after exposure, it is highly dangerous, with instant death from a concentration as low as 1000 ppm.

• Question 530:

  A group of male workers between the ages of 20 and 39 years are being screened for lung disease by spirometry. Nine subjects are examined. Their forced expiratory volume in 1 second (FEV1) divided by forced vital capacity (FEV1/ FVC %) results are 80, 76, 73, 61, 64, 79, 64, 64, and 78. What is the mean?

  A. 61
  B. 64
  C. 71
  D. 73
  E. 76
  C. 71

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  Explanation

  The mean, or average, is the total of all readings divided by the number of readings, or (x)/n. In the example described in the question, the total of all readings equals 639; the number of readings is 9.

  Therefore, the mean is 639 divided by 9, or 71.