USMLE USMLE Certifications USMLE-STEP-2 Questions & Answers

• Question 661:

  A63-year-old man with chronic bronchitis presents to the emergency department with worsening shortness of breath. He is dyspneic, his respiratory rate is 32/min, and he has peripheral cyanosis. A chest examination reveals increased anteroposterior diameter and scattered rhonchi, but no wheezes or evidence of consolidation. His ABG determinations on room air are pH of 7.36, arterial oxygen pressure (PaO2) of 40 mmHg, and PaCO2 of 47 mmHg. He is given oxygen by face mask while awaiting a CXR. His respiratory rate falls to 12/min,but his ABGs on oxygen are now pH of 7.31, PaO2 of 62 mmHg, and PaCO2 of 58 mmHg. Which of the following is the most appropriate next step in the management of this patient?

  A. repeat the ABG

  B. initiate mechanical ventilation

  C. obtain a CXR

  D. check the oxygen delivery system

  E. decrease the fraction of inspired oxygen (FIO2)

  Correct Answer: E

  Patients with advanced chronic obstructive pulmonary disease (COPD) are at risk for development of acute respiratory failure. Common precipitants are infections, increased secretions, and superimposed bronchospasm. Oxygen therapy is effective in reversing the hypoxemia associated with respiratory failure. Arisk of such therapy peculiar to patients with COPD is worsening hypercapnia. Affected patients are thought to have lost their respiratory center's sensitivity to hypercapnia, so that their primary stimulus to breathe is hypoxemia. When the hypoxemia is corrected, they may lose their stimulus to breathe and develop carbon dioxide narcosis with worsening acidosis, confusion, stupor, and eventually coma. Because of this, the usual approach is to begin with a low fraction of inspired oxygen (FIO2) and increase gradually. Serial ABGs are obtained to ensure that as PaO2 improves,

• Question 662:

  A 23-year-old man presents complaining of severe crampy abdominal pain and blood in his stool over the past 2 days. Asimilar episode occurred a few months ago and spontaneously resolved. No history of travel. Abdominal x-ray shows mild colonic dilatation. Which of the following is the most likely diagnosis?

  A. ulcerative colitis

  B. viral gastroenteritis

  C. irritable bowel syndrome

  D. celiac sprue

  E. Whipple disease

  Correct Answer: A

  Ulcerative colitis typically presents between the ages of 15 and 25 years with symptoms of diarrhea with blood and abdominal pain. Involvement begins in the rectum and is limited to the colon. The recurrent episodes and hematochezia make inflammatory bowel disease most likely.

• Question 663:

  A60-year-old man presents with a nonproductive cough for a week and generalized malaise. He also has noted some abdominal pain associated with diarrhea for the past few days. His temperature is 101.5°F a nd clinical examination is unremarkable. ACXR shows a left lower lobe infiltrate. His urinalysis shows 50 RBCs, and his BUN (30) and creatinine (1.6) are both mildly elevated. In light of the extrapulmonary symptoms and signs, which of the following is the most likely cause of his pneumonia?

  A. Pseudomonas aeruginosa

  B. S. aureus

  C. H. influenzae

  D. S. pneumoniae

  E. Legionella

  Correct Answer: E

  The spectrum of infection with Legionella organisms ranges from asymptomatic seroconversion to Pontiac fever (a flu-like illness) to full-blown pneumonia. Cough is usually nonproductive initially. Malaise, myalgia, and headache are common. The diagnosis of Legionella infection is suggested by extrapulmonary signs and symptoms, including diarrhea, abdominal pain, azotemia, and hematuria.

• Question 664:

  A 63-year-old man complains of a new cough and of breathlessness after walking up a flight of stairs. Chest examination reveals late inspiratory crackles but no wheezes. There is a mild clubbing of the fingers. His CXR is shown in figure. Which of the following would be found on pulmonary function testing (PFT)?

  

  A. increased arterial carbon dioxide pressure (PaCO2)

  B. normal compliance

  C. decreased carbon monoxide diffusing capacity (DLCO)

  D. increased vital capacity

  E. increased oxygen saturation with exercise

  Correct Answer: C

  The CXR shown in Figure shows a diffuse reticulonodular pattern consistent with ILD. The hilar nodes are enlarged, suggesting lymphadenopathy. This is a nonspecific picture and may be caused by a large number of diseases. Occupational exposure to dust, gas, or fumes; sarcoidosis; idiopathic pulmonary fibrosis; and lung disease associated with the rheumatic diseases are the more common factors. Despite the diverse causes, there is a common pathogenesis: injury leads to alveolitis, which progresses to fibrosis. Abnormalities on PFT are also similar: restrictive disease characterized by decreased lung volumes (vital capacity, TLC) and decreased compliance. Loss of the alveolar capillary bed leads to decreased carbon monoxide diffusing capacity. Arterial oxygen pressure (PaO2) may be normal at rest but is decreased with exercise. Arterial carbon dioxide pressure (PaCO2) may be normal or decreased because of hyperventilation, but it is not usually elevated in pure ILD.

• Question 665:

  A50-year-old woman complains of worsening dyspnea of 1-month duration, but is otherwise asymptomatic. Lung examination is normal; her CXR is shown in the figure below. Which of the following is the most likely diagnosis?

  

  A. pulmonary tuberculosis

  B. lung metastases

  C. sarcoidosis

  D. mycoplasma pneumonia

  E. silicosis

  Correct Answer: B

  The CXR shown in figure contains multiple bilateral pulmonary parenchymal nodules varying in size and shape, most compatible with metastatic disease to the lungs. Other possibilities are bronchogenic carcinoma or fungal granulomas (e.g., histoplasmosis or coccidiosis). Sarcoidosis usually presents with bilateral hilar adenopathy and rarely with multiple pulmonary nodules. Tuberculosis presents with a cavitating lesion, pleural effusion, or miliary pattern. Typical findings in silicosis are diffuse nodular fibrosis and eggshell calcification of hilar or bronchopulmonary lymph nodes. The CXR of patients with mycoplasma pneumonia usually shows patchy infiltrates involving the lower lobes and spreading from the hila. The finding of metastatic nodules on CXR should prompt a search for the primary tumor.

• Question 666:

  In this otherwise healthy adult woman, what is the most likely infecting organism?

  A. group B Streptococcus

  B. Staphylococcus aureus

  C. Haemophilus influenzae

  D. Streptococcus pneumoniae

  E. Listeria monocytogenes

  Correct Answer: D

  S. pneumoniae is the most common cause of adult meningitis in people over 30 and accounts for about 15% of cases. H. influenzae is the most common cause in children over 1 month old. Group B Streptococcus is an important cause of neonatal meningitis, but is very rare in adults. Staphylococcus, E. coli, and Klebsiella may be seen with penetrating head wounds or postneurosurgical procedures.

• Question 667:

  In the adult neutropenic patient, which of the following is the most likely organism to cause bacterial meningitis?

  A. group B Streptococcus

  B. S. aureus

  C. H. influenzae

  D. S. pneumoniae

  E. L. monocytogenes

  Correct Answer: E

  Although Listeria still represents only a fraction of total cases (about 10%) of meningitis, it is seen in diabetes and cancer patients, alcoholic, elderly, and immunocompromised patients.

• Question 668:

  A 78-year-old woman comes to your primary care office practice with her son who is concerned about changes in her mood. She is less interested in going out to dinner and does not want to visit family or friends. Her language skills seem to have deteriorated over the last few years and her memory is not as sharp. Her gait and motor strength are normal. Which of the following is the most likely diagnosis?

  A. Parkinson's disease

  B. anxiety disorder

  C. meningioma

  D. Alzheimer's disease

  E. dysthymia

  Correct Answer: D

  Classic features of Alzheimer's syndrome include amnestic memory impairment, deterioration of language, and visuospatial deficits. Gait disturbances and motor and sensory changes are uncommon until late phases of the syndrome. Mood change and apathy are commonly seen in early stages of Alzheimer's syndrome and typically continue for the duration of the disease. Psychotic features may be seen in middle and late phases of the syndrome.

• Question 669:

  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

  Correct Answer: E

  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 670:

  A42-year-old patient suffering from alcoholism has advanced liver disease with ascites. He is hospitalized for agitation and bizarre behavior. Which of the following findings is most helpful in making the diagnosis of hepatic encephalopathy?

  In the patient above, his blood ammonia level is twice his baseline. Which of the following is a likely precipitating factor?

  A. bleeding esophageal varices

  B. noncompliance with diuretic therapy

  C. excessive lactulose therapy

  D. insufficient protein ingestion E. recent alcohol ingestion

  Correct Answer: A

  Hepatic encephalopathy is a syndrome of declining intellectual function, altered state of consciousness, and neurologic abnormalities in the setting of advanced liver disease. Other findings include hyperactivity, delirium, agitation, and personality changes, progressing to confusion, somnolence, and coma. Asterixis (lapses of sustained muscle contraction) or "flapping tremor" is common. Jaundice, spider angiomas, and ascites can be present in alcoholic liver disease without the presence of encephalopathy. Precipitating factors must be looked for and reversed if possible. GI bleeding (due to esophageal varices, gastritis, ulcer, and so forth) increases the nitrogen load in the gut and reduces cerebral perfusion. Excessive diuresis with prerenal azotemia increases extrahepatic circulation of urea and ammonia production, so noncompliance with diuretics would decrease ammonia levels. Lactulose acidifies the stool, traps ammonia and other nitrogenous substances, and decreases their absorption from the gut so excessive lactulose would decrease ammonia levels. Excessive protein intake is a common precipitant.