USMLE USMLE-STEP-3 Online Practice Questions and Exam Preparation

USMLE USMLE-STEP-3 Online Questions & Answers

• Question 31:

  A 64-year-old Hispanic female with type II DM and hypertension for 15 years comes to your office after not seeing a physician for 5 years. The HgbA1C is 9. She reports that her vision has been deteriorating but new glasses from the optometrist have helped.

  Your examination findings include all of the above. These form which of the following diagnoses?

  A. nonproliferative diabetic retinopathy
  B. proliferative retinopathy
  C. central serous chorioretinopathy
  D. microangiopathy of the retina
  E. hypertensive retinopathy
  B. proliferative retinopathy

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  Explanation

  Persons with DM are 25 times more likely to become legally blind than persons without diabetes. Blindness is primarily the result of progressive diabetic retinopathy and clinically significant macular edema. The presence of retinal vascular microaneurysms, blot hemorrhages, and cotton wool spots mark the presence of nonproliferative diabetic retinopathy. Increased retinal vascular permeability, alterations in blood flow, and abnormal microvasculature lead to retinal ischemia. In response to the ischemia, new blood vessels may form at the optic nerve and/or macula (neovascularization). This marks the presence of proliferative diabetic retinopathy. These new vessels rupture easily and may lead to vitreous hemorrhage, fibrosis, and retinal detachment.

• Question 32:

  A 54-year-old male presents to the ED with acute onset of severe abdominal pain. His history is significant for gnawing epigastric pain that radiates to the back for several months. Physical examination demonstrates mild hypertension and tachycardia as well as a rigid "board like" abdomen with generalized rebound tenderness and hypoactive bowel sounds. Rectal examination reveals dark hemoccult positive stools without gross blood. While you are in the process of working up the patient he becomes hypotensive and tachycardic. Bright red blood per rectum is now noted. The most likely explanation for his condition is which of the following?

  A. ruptured esophageal varices
  B. diverticulosis
  C. ruptured abdominal aortic aneurysm (AAA)
  D. ruptured splenic artery aneurysm
  E. erosion of the gastroduodenal artery
  E. erosion of the gastroduodenal artery

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  Explanation

  The patient's history of gnawing epigastric pain is consistent with ulcer disease. His presentation is that of a perforated duodenal ulcer. The most appropriate first step is to obtain upright plain films of the chest and abdomen to look for free intraperitoneal air. Although the patient is in mild distress, he is not toxic and it is reasonable to confirm your suspicion with radiologic studies. If the plain films did not demonstrate free air and the patient remained hemodynamically stable, a CT scan of the abdomen and pelvis may be indicated to try to make the diagnosis. However, if the patient did show signs of increasing toxicity and evidence for sepsis, such as hypotension or mental status changes, it would be reasonable to proceed with an exploratory laparotomy to make the diagnosis. Upper endoscopy is not indicated in the acute management of a perforated duodenal ulcer and this patient is currently in significant distress and discharging to home with delayed follow-up is unwise. The patient most likely has a posterior perforation of a duodenal ulcer that has eroded into the gastroduodenal artery causing bleeding per rectum, tachycardia, and hypotension. Diverticulosis is a common cause of bright red blood per rectum in elderly patients but is often painless and not consistent with the presentation of this patient. A ruptured AAA generally presents with hypotension and profound shock. A distended abdomen and pulsatile mass can be found on physical examination. Ruptured esophageal varices present with upper GI bleeding and hematemasis and are most often associated with patients who have chronic liver disease.

• Question 33:

  A mother relates seeing worms in her 3-yearold's stool. She describes them as 1-cm long white threads that seemed to be moving. What is the most likely infectious etiology for this finding?

  A. Ascaris lumbricoides
  B. Diphyllobothrium latum
  C. Taenia solium
  D. Toxocara canis
  E. Enterobius vermicularis
  E. Enterobius vermicularis

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  Explanation

  Pinworms (E. vermicularis) are common nematodes (roundworms) found in children. It usually is a benign, incidental finding, but can present with perianal pruritus or small, white, threadlike worms on visual examination. Ascariasis is the most common roundworm infection in humans, but these worms are larger. T. canis (dog roundworm) is another nematode and is the cause of visceral larval migrans. D. latum (fish tape worm) and Taenia solium (pork tape worm) are cestodes, which are long, flat worms.

• Question 34:

  A 68-year-old White male, with a history of hypertension, an 80 pack-year history of tobacco use and emphysema, is brought into the ER because of 4 days of progressive confusion and lethargy. His wife notes that he takes amlodipine for his hypertension. He does not use over-the-counter (OTC) medications, alcohol, or drugs. Furthermore, she indicates that he has unintentionally lost approximately 30 lbs in the last 6 months. His physical examination shows that he is afebrile with a blood pressure of 142/85, heart rate of 92 (no orthostatic changes), and a room-air O2 saturation of 91%. He is 70 kg. The patient appears cachectic. He is arousable but lethargic and unable to follow any commands. His mucous membranes are moist, heart rate regular without murmurs or a S3/S4 gallop, and extremities without any edema. His pulmonary examination shows mildly diminished breath sounds in the right lower lobe with wheezing bilaterally. The patient is unable to follow commands during neurologic examination but moves all his extremities spontaneously. Laboratory results are as follows:

  Blood Sodium: 109 Potassium: 3.8 Chloride: 103 CO2: 33 BUN: 17 Creatinine: 1.1 Glucose: 95 Urine osmolality: 600 Plasma osmolality: 229 White blood cell (WBC): 8000 Hgb: 15.8 Hematocrit (HCT): 45.3 Platelets: 410 Arterial blood gas: pH 7.36/pCO2 60/pO2 285 A chest x-ray (CXR) reveals a large right hilar mass.

  Which of the following would be the optimal choice of solution to infuse in order to adequately correct this patient's hyponatremia?

  A. D5W with 20 meq/L KCl at 200 mL/h
  B. 0.9% saline at 125 mL/h
  C. 0.45% saline at 100 mL/h
  D. 3% saline at 35 mL/h
  E. 0.45% saline with 30 meq/L KCl at 100 mL/h
  D. 3% saline at 35 mL/h

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  Explanation

  The patient has hypotonic hyponatremia, which can lead to increased water shifting into the brain, resulting in cerebral edema. This patient has nothing in history or physical examination to suggest a stroke or the presence of sepsis as the etiology of his altered mental status. Central pontine myelinolysis is a potentially devastating neurologic complication that can result from the treatment of hyponatremia, not hyponatremia itself. While respiratory acidosis could potentially contribute to this patient's change in mental status, cerebral edema due to hypotonicity is the most likely etiology. The patient's laboratory studies indicate a low plasma osmolality with an inappropriately increased urine osmolality. With this degree of hypotonicity, the urine should be maximally dilute (osmolality of <100 mOsmol/kg H2O). The high urine osmolality suggests the presence of antidiuretic hormone. In psychogenic polydipsia, the urine would be maximally dilute. Choice C is unlikely since his physical examination does not suggest volume depletion; furthermore, the patient is taking a calcium channel blocker, not a diuretic, for the treatment of his hypertension. Decreased expression of renal collecting duct water channels would lead to water wasting and, thus, the development of diabetes insipidus and hypernatremia. The patient has symptomatic hypotonic hyponatremia with signs of cerebral edema.

  This requires immediate attention. Choices A, C, and E are essentially hypotonic solutions which should be withheld in patients with hyponatremia. The serum sodium in this case should be increased by at least 5% for the treatment of cerebral edema. The use of 0.9% saline would require nearly 5 L of infusate to address this cerebral edema. This could lead to pulmonary edema and volume overload. The use of hypertonic saline (3% saline) is the ideal solution to use in this scenario, as the infusion of 3% saline will correct the symptoms while avoiding volume overload. As in all cases of hyponatremia management, frequent serum sodium assays are necessary in order to avoid too rapid of a correction, which could result in neurologic injury--pontine myelinolysis.

• Question 35:

  Patients with septic arthritis of the hip joint usually present with which position?

  A. internal rotation and flexion
  B. internal rotation and extension
  C. internal rotation and abduction
  D. external rotation and flexion
  E. external rotation and abduction
  D. external rotation and flexion

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  Explanation

  The joint space is most relaxed when the hip is flexed and externally rotated. This tends to be the least painful position for patients with septic arthritis

• Question 36:

  Which of the following produces the greatest increase in bone mineral density (BMD) in patients with osteoporosis?

  A. estrogen
  B. calcitonin
  C. alendronate
  D. teriparatide
  E. raloxifene
  D. teriparatide

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  Explanation

  Teriparatide is a recently approved recombinant form of parathyroid hormone that stimulates bone formation, rather than inhibiting resorption, and which is associated with a marked reduction in the incidence of bone fractures. Estrogen and the estrogen receptor modulator raloxifene, alendronate, and calcitonin all inhibit bone resorption and increase BMD, but the percent increase in bone density is less than occurs with teriparatide

• Question 37:

  You are called to see a newborn in the nursery because the nurse is concerned that the baby may have Down syndrome.

  The infant begins to have progressively large amounts of bilious emesis. The infant feeds well and has only a small amount of abdominal distention.

  What is the most likely diagnosis?

  A. pyloric stenosis
  B. Hirschsprung disease
  C. biliary atresia
  D. duodenal atresia
  E. milk protein allergy
  D. duodenal atresia

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  Explanation

  The most common finding in a newborn with Down syndrome is hypotonia. Other common findings include single palmar crease, flat facial profile, macroglossia, and wide space between the first and second toes. Hypotonia in the newborn period should prompt close evaluation and follow-up. Caf?au lait spots are associated with neurofibromatosis. High arched palates are associated with fragile X syndrome.

  Ambiguous genitalia are commonly seen in CAH.

  Children with Down syndrome are at an increased risk for hypothyroidism. It may be hard to detect without routine laboratory screening as they will commonly have mental retardation and developmental delay as part of their syndrome. Hypothyroidism may not be present in the immediate newborn period and requires, at a minimum, annual testing throughout the child's life. The other findings listed are not specifically associated with Down syndrome. Lens dislocation is commonly found with Marfan syndrome or homocysteinuria.

  Children with Down syndrome have an increased prevalence of duodenal atresia. Pyloric stenosis is uncommon to see in the newborn period. It tends to present with nonbilious vomiting usually after 24 weeks of age. Hirschsprung disease (aganglionosis coli) presents with constipation and failure to pass stool. Infants with Hirschsprung disease commonly will not pass stool in the first days of life. Biliary atresia is a progressive cause of jaundice in an infant. It is the most common cause of a cholestatic jaundice in the newborn period. Emesis is not typically associated with biliary atresia. Milk protein allergy is a common cause of bloody stools in the first few months of life, but does not have bilious emesis associated with it.

• Question 38:

  The patient is a 7-year-old boy brought in for evaluation by his father. He has been concerned with his son's behavior. At school conferences, he has been told that his son will not stay in place and moves around the room despite being informed about the rules. He neither listens at home nor at school when given feedback. For example, he continues to have difficulty waiting in line, completing his homework, and cleaning up his toys, regardless of numerous consequences. In department stores, he will run around and grab at items, and this has resulted in his breaking merchandise on many occasions. The father states that his son has been this way "since he could walk" and is worried about his son's future.

  Which of the following is his most likely diagnosis?

  A. attention deficit/hyperactivity disorder (ADHD)
  B. autistic disorder
  C. conduct disorder
  D. obsessive-compulsive disorder (OCD)
  E. oppositional defiant disorder
  A. attention deficit/hyperactivity disorder (ADHD)

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  Explanation

  This patient suffers from ADHD as evidenced by numerous inattentive and hyperactive/ impulsive symptoms and signs. Autistic disorder is a pervasive developmental disorder (PDD) consisting of impairments in social interaction and communication, in addition to stereotyped behaviors. Conduct disorder is a disruptive behavior disorder characterized by aggression and violation of the rights of others. While oppositional defiant disorder is also a disruptive behavior disorder, it is not as severe as conduct disorder, occurring at an earlier age and demonstrating a pattern of negativistic and defiant behaviors. OCD is an anxiety disorder not uncommonly seen in children, diagnosed by the presence of recurrent, distressing obsessions and/or compulsions.

  Stimulants are the first-line treatment for ADHD. However, there are many misconceptions regarding their use, which may necessitate the use of more detailed psychoeducation.

  It was previously believed that stimulants exert their clinical effect through sedation, but this is no longer considered to be true. Stimulants not only improve behavior, but there is evidence that they actually "normalize" school performance as well. The use of drug holidays, such as weekends and during the summer, is recommended in order to make up for any growth suppression.

• Question 39:

  A 12-year-old boy is brought into the office by his mother, who states, "I can't deal with this anymore!" She appears exasperated, claiming that her son has been getting into more and more trouble over the past 15 months since the finalization of a particularly long and difficult divorce. He has been leaving the house at night without notifying his mother or telling her of his whereabouts. She suspects that he is responsible for the increased vandalism in the neighborhood. He has recently been caught shoplifting at a nearby store. His grades have always been poor, but he has just been suspended for missing classes and skipping school over the past year. He has often come home with evidence of having been in fights. She suspects that he may be hanging out with gang members. She is afraid of his ending up in jail and "becoming like his father."

  If untreated, which of the following diagnoses is most likely to transpire in this patient?

  A. alcohol dependence
  B. oppositional defiant disorder
  C. panic disorder
  D. schizoid personality disorder
  E. schizophrenia
  A. alcohol dependence

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  Explanation

  This patient exhibits the criteria for conduct disorder. Antisocial personality disorder can only be diagnosed in a person who is over age 18. In fact, the diagnosis of antisocial personality disorder requires evidence of conduct disorder prior to age 15 (DSM IV-TR). Children with autism, schizophrenia, and mental retardation may display aggressive or disruptive behavior, but these illnesses do not necessarily predict future conduct disorder. Patients with ADHD and learning disorders are at an increased risk of developing conduct disorder as they get older.

  It is not uncommon for patients with conduct disorder to have a history of oppositional defiant disorder as a younger child. Indeed, the disorders are often thought of as being on a spectrum, with oppositional defiant disorder early on, followed by conduct disorder and eventually antisocial personality disorder. Having conduct disorder does not by itself predict panic disorder, schizoid personality disorder, or the development of schizophrenia. If left untreated, there is a significantly increased risk of developing a substance use disorder, which also predicts a worse prognosis

• Question 40:

  A 14-year-old nulligravid female is brought to the ER by her parents with a 12-hour history of severe, intermittent left lower quadrant pain. She has had nausea and vomiting for the past 2 hours. On history, the patient experienced menarche at age 12 and denies past or current contact with a sexual partner. Her last normal menstrual period was 3 weeks ago. On examination, she is afebrile, pulse 100, BP 110/70, respiratory rate (RR) 20. She is visibly uncomfortable. She has no costovertebral tenderness, has diminished bowel sounds, her abdomen is nondistended, and exhibits rebound and guarding in both lower quadrants. She is unable to tolerate a pelvic examination due to pain. Laboratory values are as follows:

  WBC 13, HCT 39, -hCG (-), UA (-). Apelvic ultrasound shows a normal nonpregnant uterus, normal right adnexa, and an 8-cm left adnexal mass with a 3-cm solid component

  The most likely etiology of this patient's pain is which of the following?

  A. ectopic pregnancy
  B. acute appendicitis
  C. ovarian torsion
  D. pancreatitis
  E. somatization disorder
  C. ovarian torsion

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  Explanation

  This patient is demonstrating acute peritoneal signs that require surgical intervention. Adding additional testing, either with radiology or more laboratory assessment would not alter the management at this point in time. Although some patients with chronic pelvic pain have a history of sexual or physical abuse, an assessment in the acute emergent setting does not take initial priority. Although ovarian torsion can be enigmatic in its presentation, this patient demonstrates classic signs of intermittent pelvic pain and an ovarian cyst with a solid component. The 8-cm increase in ovarian size is likely due to vascular congestion from occlusion of the blood supply. Early intervention is more likely to result in salvaging viable tissue before the onset of irreversible tissue necrosis. The absence of fever and other GI symptoms, along with a left lower quadrant mass on ultrasound goes against the possibility of appendicitis or pancreatitis. Her pregnancy test is negative which generally excludes an ectopic pregnancy.