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

USMLE USMLE-STEP-2 Online Questions & Answers

• Question 541:

  A 55-year-old woman presents with a 6-month history of weight loss, abdominal cramps, and intermittent nonbloody diarrhea. On examination, her abdomen is mildly distended and there is a palpable mass in the right lower quadrant. Stool cultures yield normal fecal flora. CT scan with oral contrast demonstrates an inflammatory mass in the right lower quadrant, with thickening of the terminal ileum and ileocecal valve.

  Which of the following is the most likely diagnosis?

  A. ulcerative colitis
  B. appendicitis
  C. Crohn's disease
  D. irritable bowel syndrome
  E. lactose intolerance
  C. Crohn's disease

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  Explanation

  Crohn's disease is a chronic inflammatory disease of the gastrointestinal tract that presents with intermittent crampy abdominal pain and diarrhea. It most commonly involves the terminal ileum and right colon. Because eating can exacerbate symptoms, oral intake may be decreased, contributing to the associated weight loss. Transmural inflammation leads to bowel wall thickening, and with adjacent mesenteric inflammation, the patient may develop a palpable mass. It may be difficult to differentiate Crohn's disease from ulcerative colitis on the basis of history and clinical examination.

  However, ulcerative colitis is a mucosal disease that is limited to the colon and nearly always involves the rectum. Diarrhea is usually bloody, and hemorrhage may be significant enough to require transfusion therapy. Complicated appendicitis may present with a right lower quadrant mass and diarrhea if there is perforation with abscess formation. The history is that of an acute illness in a previously well patient. Irritable bowel syndrome is associated with intermittent crampy abdominal pain, and diarrhea alternating with constipation. There is no inflammatory process, and weight loss is not a clinical feature. Evaluation of the small bowel is best accomplished with contrast radiography, such as a small-bowel follow-through study or enteroclysis. Radiographic abnormalities of small-bowel Crohn's disease are often distinctive and can demonstrate complications such as strictures and fistulae. CT scanning does not assist in confirming the diagnosis, but is helpful in detecting such complications as abscess.

  Ultrasonography has limited value. Sigmoidoscopy may not be useful, because Crohn's disease commonly spares the rectum and may be worse on the right side of the colon. Colonoscopy may be helpful when the colon is involved and when intubation of the ileocecal valve can be achieved; however, the disease may be limited to the small bowel resulting in a nondiagnostic examination.

  The principle of initial management of Crohn's disease is relief of symptoms, nutritional therapy, and suppression of the inflammatory process. Nutritional supplementation may require TPN in conjunction with bowel rest. Acute exacerbations of the disease are initially treated with systemic steroids. The use of antispasmodics may be effective in the treatment of irritable bowel syndrome. In Crohn's disease, however, antispasmodics may lead to an ileus or toxic bowel dilatation. Surgery in Crohn's disease is indicated for the management of complications, including fistula or abscess formation, stricture with obstruction, and perforation.

• Question 542:

  For each item, select the ONE best lettered option that is most closely associated with it. Each lettered heading may be selected once, more than once, or not at all. A 55-year-old man complains of abdominal pain and is found to have a kidney stone. Laboratory evaluation reveals hypercalcemia.

  A. Cushing's syndrome
  B. Addison's disease
  C. Klinefelter syndrome
  D. hyperparathyroidism
  E. hypothyroidism
  F. pheochromocytoma
  G. acromegaly
  H. diabetes insipidus
  I. diabetes mellitus
  J. polycystic ovarian disease
  D. hyperparathyroidism

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  Explanation

  In primary hyperparathyroidism, increased levels of PTH lead to hypercalcemia and hypophosphatemia. Patient symptoms and signs on presentation include kidney stones, peptic ulcers, mental status changes and less commonly, extensive bony resorption.

• Question 543:

  For each clinical setting described below, select the set of ABG determinations with which it is most likely to be associated.

  A30-year-old woman with salicylate intoxication

  pH PaO2 PaCO2

  A. 7.23 64 80
  B. 7.39 88 40
  C. 7.22 74 33
  D. 7.54 75 24
  E. 7.37 67 52
  D. 7.54 75 24

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  Explanation

  ABG determinations are essential in the diagnosis of respiratory and acid-based disturbances. Extremely obese patients suffer from increased work of breathing, as well as elevation of the diaphragm with decrease in lung volume. The resultant hypoventilation is characterized by carbon dioxide retention leading to chronic respiratory acidosis with metabolic compensation (ABG set E in the question). When associated with somnolence, excessive appetite, and polycythemia, this is known as the pickwickian syndrome. Modest weight loss can lead to dramatic improvement in respiratory functioning. The earliest derangement in salicylate poisoning is hyperventilation, resulting in decreased PaCO2 and increased arterial pH (ABG set D). Eventually, there is CNS depression with somnolence and hypoventilation resulting in respiratory acidosis. Diabetic ketoacidosis may cause acute metabolic acidosis. In a healthy young adult with no lung disease, appropriate respiratory compensation occurs (ABG set C). Without insulin to reverse this process, the patient may go on to develop worsening acidosis and an inability to compensate adequately. ABG set A reflects acute respiratory acidosis (hypoventilation) without metabolic compensation. ABG set B is normal.

• Question 544:

  A specific pattern of abnormalities has been identified among infants born to mothers who consume moderate-to-large amounts of alcohol during their pregnancies. Which of the following abnormalities is characteristic of these infants?

  A. cataracts
  B. developmental dysplasia of the hip
  C. gonadal dysgenesis
  D. neural tube defects
  E. mental retardation
  E. mental retardation

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  Explanation

  The characteristics of fetal alcohol syndrome include: A. persistent deficient growth affecting weight, height, and head circumference and beginning in utero; B. such facial abnormalities as micrognathia, short palpebral fissures, and a thin upper lip; (C) cardiac abnormalities, commonly septal defects; (D) minor limb abnormalities with some restriction of mobility and some alteration in palmar crease patterns; and (E) mental deficiency ranging from mild to severe. There is a decided relationship between the extent of abnormalities and the degree of mental retardation. Affected infants may present with hypoglycemia and alcohol withdrawal symptoms which may last for 4872 hours. Immediate management of these infants consists of correction of the hypoglycemia. Ongoing monitoring of the child's development is essential. Prevention by restriction of alcohol consumption during pregnancy is advised.

• Question 545:

  A beekeeper's previously healthy 6-month-old son develops gradual onset of lethargy, poor feeding, constipation, and generalized weakness. On taking a history, you determine that the child has recently been placed on a homemade formula consisting of evaporated milk, water, and honey. Which of the following is the most likely explanation for this symptom complex?

  A. sodium intoxication
  B. Hirschsprung disease
  C. hypothyroidism
  D. spinal cord tumor
  E. botulism
  E. botulism

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  Explanation

  The child described in the question seems to be afflicted with infant botulism. Clostridium botulinum spores are commonly found in honey, and the toxin responsible for the symptoms described is produced in the infant's GI tract. Therefore, children younger than 1 year should not be fed honey. Hypernatremic dehydration may show some similarities to infant botulism, but the skin and mucous membranes are characteristically dry. Serum sodium level is often greater than 160. Hirschsprung disease would explain constipation but not the other findings listed. Congenital hypothyroidism shows a more insidious onset, with prolonged constipation and weakness. In addition, developmental retardation would likely be present.

• Question 546:

  After 10 days of nasal congestion and rhinorrhea, a 3-month-old infant develops a severe hacking cough during which he repeatedly turns dusky and appears to choke on or to vomit profuse thick, clear nasopharyngeal mucus. For 7 days, the coughing continues unabated. On physical examination, he is afebrile and his lungs are clear. His chest x-ray is normal. His WBC count is 24,000/mm3, with 15% polymorphonuclear cells, 82% lymphocytes, and 3% monocytes. Which of the following antibiotics should be used to treat this patient?

  A. amoxicillin
  B. amoxicillin-clavulanic acid
  C. erythromycin
  D. tetracycline
  E. no antibiotics are necessary
  C. erythromycin

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  Explanation

  Whooping cough, or pertussis, tends to have a prolonged course, with a 2-week prodrome of undifferentiated upper respiratory infection followed by approximately 2 weeks of a paroxysmal, machine gun-like cough and nasopharyngeal mucus that is strangling, thick, and clear. The typical whoop, a stridorous inspiratory gasp at the end of each paroxysm, is often absent in infants younger than 6 months. Posttussive vomiting more likely will be found in this age group. The diagnosis should be suspected in children with a paroxysmal, harsh cough and absolute lymphocytosis. Specific inquiry into the history of a severe or long-lasting cough in adult caretakers should be sought. The diagnosis is made by culture of the organism (Bordetella pertussis) or by an immunofluorescent study of throat swab material. Erythromycin is the drug of choice. It has little effect on the illness course after paroxysms are established and is used primarily to limit spread of infection to others.

• Question 547:

  You evaluate a 38-year-old man who complains of muscle weakness. Her appearance is remarkable for a periorbital heliotrope rash with edema and erythema on his upper chest, neck, and face. Which of the following is the most likely diagnosis?

  

  A. polymyositis
  B. dermatomyositis
  C. spinocerebellar degeneration
  D. vasculitis
  E. rheumatoid arthritis
  B. dermatomyositis

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  Explanation

  The heliotrope, purple periorbital rash is seen with dermatomyositis and may even precede the muscle involvement. On examination, these patients will usually show proximal muscle weakness and may complain of difficulty getting up from a chair, climbing stairs, and raising the arms over the head. Ataxia may be present with cerebellar lesions. Deep tendon reflexes should be normal and there is no joint inflammation. Polymyalgia rheumatica generally occurs in older people but is not associated with muscle weakness. Spinocerebellar degeneration, vasculitis, and rheumatoid arthritis are not associated with this rash. Creatine phosphokinase is usually markedly elevated and muscle biopsy will confirm the diagnosis. Serum creatinine, sodium, and potassium should be normal, and the rheumatoid factor should not be elevated.

• Question 548:

  A 13-year-old boy presents for evaluation of short stature. His growth chart from ages 2 through 12 years is shown in Figure. His growth in the first 2 years of life was typically at the 25th percentile. He has been healthy, has a good appetite, and is doing well in school. He lives with his parents and is an only child. His parents' heights are both at the 50th percentile. His father states that he grew several inches after he completed high school. A complete physical examination is normal. His Tanner stage is

  A. Which of the following is the most likely cause of this patient's short stature?
  B. constitutional delay
  C. deprivational dwarfism
  D. familial short stature
  E. growth hormone deficiency
  F. hypothyroidism
  A. Which of the following is the most likely cause of this patient's short stature?

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  Explanation

  Constitutional delay is a normal pattern of growth, characterized by a relatively late pubertal growth spurt. It is recognized most commonly in boys. Patients typically show a moderate degree of short stature in early to middle childhood. The growth pattern is often similar to one or both parents. Final adult height is within the expected genetic potential. The children are otherwise well. Familial short stature is also a normal growth pattern in a short but otherwise normal family. One or both parents are typically 12 standard deviations below mean height for adults. The growth pattern parallels the normal growth curve at a percentile consistent with genetic potential. Deprivational dwarfism is due to psychosocial factors. It typically presents at a younger age, and weight is affected more than the height so that these children are not proportionately small. Hypothyroidism can affect growth but would cause a decrease in growth velocity when it occurred. The patient's height curve would flatten out, instead of paralleling the normal curves. Short stature from growth hormone deficiency typically presents by 3 years.

• Question 549:

  A 53-year-old woman with five adult children complains of losing urine shortly after coughing or jumping. She occasionally loses urine while lying in bed if she happens to cough vigorously. She is unable to stop the urine once it has begun to flow.

  Which of the following is the most likely diagnosis?

  A. GSI
  B. a vesicovaginal fistula
  C. a urethrovaginal fistula
  D. an atonic bladder
  E. detrusor dyssynergia
  E. detrusor dyssynergia

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  Explanation

  Two clues to the diagnosis of detrusor dyssynergia are loss of urine in the recumbent position and inability to stop the urine loss once the stream has begun. Generally, large volumes of urine are lost because of the inability to stop the flow of urine. With GSI, urine is lost only in the upright position when intra-abdominal and intravesical pressure exceeds urethral closing pressure, such as with coughing. Women with SI are able to stop the flow of urine voluntarily and, therefore, the volume of urine lost is small.

  With GSI, urine loss with coughing is immediate. Women with a vesicovaginal or urethrovaginal fistula will complain of a watery vaginal discharge. Women with an atonic bladder typically void small amounts and complain that the bladder still feels full (which it is). This is a disorder seen in women with neurologic dysfunction of the bladder, such as multiple sclerosis and diabetic neuropathy.

• Question 550:

  An 11-year-old girl has become markedly withdrawn in the past 8 months and has complained of persisting abdominal pain and constipation, for which no organic cause has been found. Select the diagnosis with which it is most likely to be associated.

  A. childhood depression
  B. childhood schizophrenia
  C. conduct disorder
  D. ADHD
  E. infantile autism
  A. childhood depression

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  Explanation

  Infantile autism, called a pervasive developmental disorder in DSM-IV, typically is diagnosed when children do not demonstrate the acquisition of communication skills. Ability to form interpersonal relationships also is grossly impaired. Other behavioral manifestations of infantile autism include unusual repetitive mannerisms (e.g., spinning), marked anxiety during environmental changes, and high pain threshold. As to be expected, school performance is poor, though autistic children may display isolated areas (islands) of normal or superior intellectual functioning. Behavioral manipulation is useful in trying to contain the behavior of autistic children. Unlike infantile autism, childhood schizophrenia usually develops later in childhood and follows an intermittent course. Deterioration in social or school functioning is a characteristic presenting feature, along with hallucinations, delusions, and other manifestations of psychosis. Phenothiazine drugs offer effective treatment. Symptoms and signs of depression in children are similar to those in adults. However, children may not be able to recognize depressed feelings. Persistence of puzzling physical problems in association with apathetic, withdrawn behavior is a common presentation. The use of antidepressants is controversial; family and individual counseling often can be quite helpful. ADHD once was called hyperactivity and minimal brain dysfunction. Characteristic signs include impulsivity, distractibility, inattention in school, and (usually but not universally) hyperactivity.

  A variety of pharmacologic agents, including imipramine, dextroamphetamine, and methylphenidate (Ritalin), have been recommended for treatment of ADHD.