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

USMLE USMLE-STEP-2 Online Questions & Answers

• Question 161:

  A 6-year-old boy presents to the emergency department with a cough, sore throat, and malaise of 4 days' duration. Examination reveals a temperature of 101.5°F, erythematous pharynx, and a tender right neck mass with overlying erythema. For the above patient with a neck mass, select the most likely diagnosis.

  A. thyroid carcinoma
  B. cystic hygroma
  C. acute suppurative lymphadenitis
  D. thyroglossal duct cyst
  E. lipoma
  F. carotid artery aneurysm
  G. mixed parotid tumor (pleomorphic adenoma)
  H. laryngeal carcinoma
  I. parathyroid adenoma
  J. branchial cleft cystK. tuberculosis
  C. acute suppurative lymphadenitis

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  Explanation

  Acute suppurative lymphadenitis is related to bacterial pathogens and most often accompanies an infectious illness, such as an upper respiratory tract infection. The nodes enlarge rapidly, are tender, and demonstrate overlying erythema of the skin.

• Question 162:

  A47-year-old man is postoperative day number 2 after an open cholecystectomy. He becomes short of breath and a medicine consultation is called to evaluate. Vital signs include a temperature of 100°F, pulse rate of 110/min, blood pressure (BP) of 110/60 mmHg, and respiratory rate of 24/min. Blood gas shows a pH of 7.52, carbon dioxide of 28, PO2 of 58, and calculated bicarbonate of 20. What is the primary acid- base disorder in this patient?

  A. metabolic acidosis
  B. respiratory acidosis
  C. metabolic alkalosis
  D. respiratory alkalosis
  E. metabolic and respiratory acidosis
  D. respiratory alkalosis

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  Explanation

  This patient has an elevated pH (normal is 7.40) indicating alkalosis. Alow carbon dioxide level is consistent with a respiratory etiology of the alkalosis. This occurs when alveolar ventilation is increased relative to CO2 production. Causes may include fever, anxiety, pain, pulmonary, and/or neurologic conditions. In a metabolic alkalosis, a high bicarbonate is seen (a bicarbonate of 20 is low normal).

• Question 163:

  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 modal reading?

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

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  Explanation

  The modal reading is the most frequently occurring observation in a group of data. (On a graph of frequency of different observations, this would be where the peak is.) This reading generally is not very useful for statistical calculations, and when the series is small, no modal reading may even occur. When drawn in graph form, the determination of unimodal or bimodal distribution may be a helpful concept from which conclusions may be drawn. The distribution in the example that accompanies the question is unimodal.

• Question 164:

  Identify the defense mechanisms of a person becoming angry with one's spouse at a party and calling him or her a name in front of everyone

  A. acting out
  B. altruism
  C. displacement
  D. intellectualization
  E. passive-aggressive behavior
  F. projection
  G. rationalization
  H. reaction formation
  I. sublimation
  J. suppression
  A. acting out

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  Explanation

  Defense mechanisms provide a means for dealing with anxiety and affect. The mechanisms chosen range from the very narcissistic and immature to mature. In suppression, a person makes a conscious decision to put the conflict aside until it can be dealt with more appropriately. On the other hand, in acting out, there is little or no attempt to contain the affect, and it is directly expressed, as in name calling. Sublimation provides a channel for the indirect expression of a need or affect. Its use is positive and socially acceptable. In reaction formation, the person acts as if the strong need or affect did not exist and acts out the opposing feeling. In projection, unacceptable feelings and thoughts are denied as part of the self and instead are "put on" the other person.

• Question 165:

  Select the organism associated with the Chronic diarrhea in a homosexual male

  A. aureus
  B. beta-hemolytic Streptococcus
  C. perfringens
  D. Mycoplasma pneumoniae
  E. Haemophilus pertussis
  F. Helicobacter pylori
  G. Escherichia coli
  H. Rickettsia prowazekii
  I. Giardia lamblia
  I. Giardia lamblia

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  Explanation

  Giardiasis may cause cramping and a chronic diarrheal syndrome, with malabsorption and weight loss. Its distribution is worldwide, particularly where hygienic standards are not high. It also occurs sporadically in high-risk individuals. Streptococcal pyoderma, including erysipelas and impetigo, has been demonstrated to precede acute glomerulonephritis. Even when appropriate antibiotics are given in adequate dosage and duration for these conditions, renal damage may still result. Prevention thus consists of wound care, including cleaning wounds well and removal of crust. Mycoplasma infections are particularly common in families with younger children. They are frequently imported to the family by school-aged children, leading to a low-grade fever and persisting tracheobronchitis in the parents, or more acutely, an atypical pneumonia. G. lamblia is found in up to 20% of homosexual males, and may cause chronic diarrhea, although in these patients it tends to be asymptomatic. E. coli was first reported as a cause of watery diarrhea in nurseries in the 1940s. Although nursery epidemics with enteropathogenic serotypes had decreased in recent years in the United States, the increase of infant- child day care centers has resulted in their relatively frequent occurrence. Furunculosis is most frequently caused by coagulase-positive staphylococcal infections. The public health significance of this largely relates to the hazards of skin infections in food handlers and subsequent staphylococcal toxin in the food, leading to staphylococcal intoxication food-borne disease. H. pylori has been associated with gastric ulcers, but not with duodenal ulcers. Otitis media, whether acute or with effusion, commonly results from viral infection, such as by RSV. Various other organisms may be responsible including Streptococcu pneumoniae, H. influenzae, and others. C. perfringens, with rare exceptions, is transmitted in a meat dish prepared in bulk. Under propitious circumstances for the organism, especially on cooling of the food, bacterial multiplication can be very rapid. Symptoms begin to occur in the affected population in about 12 hours. Epidemic typhus is a rickettsial illness. Man is the host and long-term reservoir. The vectors are body lice (P. humanus corporis). The rickettsia are not present in human excretions and cannot be transmitted by person-to-person contact.

• Question 166:

  A 5-year-old boy has a history of bed-wetting about four to five times a week. He has recently begun to attend kindergarten. He was toilet trained (dry during the day) by age 3 but has never been consistently dry at night. He denies any dysuria or frequency. There is no history of increased thirst or frequent urination. The urinalysis is negative for blood, protein, glucose, or ketones; there are no white cells or bacteria; the specific gravity is 1.020. Which of the following is the most likely diagnosis?

  A. a urinary tract infection (UTI)
  B. primary nocturnal enuresis
  C. secondary enuresis caused by stress of the new school
  D. diabetes mellitus
  E. diabetes insipidus
  B. primary nocturnal enuresis

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  Explanation

  Enuresis may be primary (75%) where nocturnal control was never achieved; secondary enuresis (25%) is when the child was dry at night for at least a few months. Nocturnal enuresis is more common in boys, and family history is positive in at least 50%. This may affect as much as 20% of children at age 5 years, and it spontaneously stops in at least 15% of affected children every year. Psychological factors are often involved in secondary enuresis. A careful history should be obtained to rule out such organic factors as UTI (dysuria, frequency, urgency). Children with diabetes insipidus or diabetes mellitus have polydipsia and polyuria. Urinalysis should be considered to rule out an organic cause. In diabetes mellitus, urinalysis may reveal glycosuria and ketonuria. Aurinespecific gravity of >1.015 makes diabetes insipidus unlikely.

• Question 167:

  A 22-year-old woman and her 24-year-old partner have been attempting to conceive for 12 months. They have sexual intercourse two to three times per week and use no contraception or coital lubricants. She has never been pregnant and her husband has fathered no pregnancies. She has no history to suggest damage to her Fallopian tubes and her menses occur at 28- to 31-day intervals. What is the probability of conception per ovulation in normally fertile couples?

  A. 5%
  B. 10%
  C. 20%
  D. 35%
  E. 50%
  C. 20%

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  Explanation

  Fecundability is the ability to achieve a pregnancy, and the rate per ovulation in couples with no impediment to fertility is approximately 2025%. This figure is reduced as the woman enters her early 30s, if sexual intercourse occurs fewer than one to two times per week, or if the couple use coital lubricants in the periovulatory part of her menstrual cycle. Using the 20% fecundability rate, 20 of 100 couples will achieve a pregnancy in the first menstrual cycle of effort. In the second cycle, 20% of the remaining 80 couples will achieve a pregnancy, that is 16 women. This is a cumulative pregnancy rate of 36%. Twenty percent of the remaining 64 women will conceive in the third cycle, approximately 13 women. The cumulative conception rate after three cycles is approximately 49%. Continuing this calculation, 9095% of normally fertile couples will achieve a pregnancy within 12 ovulations. Based on this calculation, infertility is defined as the inability to conceive after 12 ovulatory cycles.

• Question 168:

  A 25-year-old man has the sudden onset of chest pain on the right side and dyspnea. On CXR, his trachea is deviated to the left. Which of the following should be anticipated on examination?

  A. rales on the left
  B. rales on the right
  C. hyperresonance on the left
  D. distant breath sounds on the right
  E. pleural friction rub on the left
  D. distant breath sounds on the right

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  Explanation

  In the patient described in the question, the movement of the trachea to the left suggests a difference between right and left pleural pressures, either a reduction in pressure on the left or a rise in pressure on the right. The acute onset of right-sided chest pain in an otherwise healthy young man suggests a pneumothorax. On the side of the pneumothorax, we would expect increased resonance and distant or absent breath sounds because of the air trapped in the pleural space between the lung and chest wall and possible compression of the normal lung. No rales or rhonchi would be expected. Apleural friction rub suggests an inflammatory process involving the left chest, a finding not likely on the basis of the patient's presentation.

• Question 169:

  A 50-year-old woman with a history of essential hypertension presents to the emergency department with sudden onset of a severe headache, nausea and vomiting, and photophobia. On examination, her BP is 160/100 mmHg. She is mildly confused and has nuchal rigidity, without focal neurologic signs. Once the diagnosis has been confirmed, which of the following is the next most important step in patient management?

  A. admission to the ICU, close monitoring, and aggressive treatment of hypertension
  B. urgent surgical intervention with aneurysm clipping
  C. admission to the ICU, close monitoring, and IV antibiotics
  D. serial lumbar punctures to drain cerebrospinal fluid (CSF)
  E. anticoagulation and antiplatelet therapy
  B. urgent surgical intervention with aneurysm clipping

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  Explanation

  Ruptured cerebral aneurysms often occur in the setting of hypertension. The severe headache, nausea and vomiting, photophobia, and nuchal rigidity are the result of meningeal irritation from subarachnoid blood. Subarachnoid hemorrhage is visualized on CT scan, with definitive diagnosis of the aneurysm and its location by cerebral angiography. Early surgical clipping is the current neurosurgical approach because of the significant risk of rebleeding in the first 24 hours after initial presentation.

  Hydrocephalus may occur as a late complication of subarachnoid hemorrhage and require serial lumbar puncture to drain CSF and control ICP. A hemorrhagic stroke can occur in association with malignant hypertension and may have concurrent subarachnoid hemorrhage. Focal neurologic signs are usually present. Meningitis will produce similar signs of meningeal irritation, but usually with other systemic signs of infection and a clinical prodromesuggesting an infectious etiology. Lumbar puncture is diagnostic, and if a bacterial source is suspected, systemic antibiotics are initiated pending culture of CSF. Ischemic cerebrovascular accidents and transient ischemic attacks are not associated with subarachnoid hemorrhage and, hence, do not present with signs of meningeal irritation. Focal neurologic signs are usually present. Evaluation of a possible cause includes Doppler examination of the carotid arteries. Management includes anticoagulation and antiplatelet therapy. EEG measures brain electrical activity and is indicated in the diagnostic evaluation of seizures.

• Question 170:

  A 40-year-old man has been unsuccessfully treated for depression with two different medications for the past 3 months. He has a number of medical problems, and he recently was hospitalized after threatening suicide. His psychiatrist is considering the use of ECT for the patient.

  The patient has consented to ECT, and the pre ECT workup has been completed. Which of the following medications could routinely be continued through a course of ECT?

  A. lithium
  B. divalproex
  C. bupropion
  D. clonazepam
  E. risperdal
  E. risperdal

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  Explanation

  Risperdal and high potency neuroleptics slightly decrease the seizure threshold and would enhance the seizure and can typically be continued through a course of ECT. Lithium can result in increased postictal delirium, divalproex and clonazepam would typically be withdrawn due to their anticonvulsant effect. If a benzodiazepine is required a short-acting medication should be used. Bupropion has been associated with late appearing seizures.