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

USMLE USMLE-STEP-3 Online Questions & Answers

• Question 381:

  A 42 year old male admitted for pulmonary embolus was placed on heparin, dosed by a weight based protocol. However, later in the day, you receive a call from the floor nurse stating that the patient had spontaneous epistaxis and a very high aPTT. Use of which of the following would be best at this time?

  A. cimetidine
  B. heparinase
  C. clofibrate
  D. protamine sulfate
  E. vitamin K
  D. protamine sulfate

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  Explanation

  Protamine sulfate is a strongly basic molecule that is thought to inhibit acidic heparin electrostatically. It may not, however, affect heparin-induced platelet aggregation. Cimetidine is an H2-antagonist that increases the anticoagulant response by an as yet unknown mechanism. Clofibrate is an agent used to reduce plasma lipid levels. Vitamin K is used to reverse the effect of warfarin. Heparinase is not used clinically.

• Question 382:

  A 52-year-old male construction worker is seen in the emergency department (ED) at a local hospital with complaints of persistent cough for the past 4 months. He has been relatively healthy until a few months ago, when he lost his mother and developed severe depression which left him socially and professionally paralyzed. He has stopped doing any exercise or outdoor activity and spends most of his time at home eating, sleeping, and watching TV. In addition, he has noticed a 20-lb weight gain over this period but attributes it to his lack of exercise and increased food intake. His cough is worse at night, or any time when he lies down to sleep, and he notices a burning sensation in his throat associated with it. It is not associated with fever or chills, and his wife complains that he is constantly clearing his throat after meals. He smoked a few cigarettes per day as a young man in the Navy but quit more than 30 years ago. He denies recent travel or incarceration and has no recollection of any sick contacts. On examination, he is afebrile and appears mildly obese. His lung examination is clear. His oropharynx is red and mucosal membranes are dry and not inflamed. Which of the following therapies would be most beneficial in alleviating this patient's symptoms?

  A. an inhaled, short-acting beta-2 agonist
  B. a proton pump inhibitor (PPI)
  C. an antitussive-expectorant syrup
  D. weight loss and exercise
  E. prolonged course of antibiotics
  B. a proton pump inhibitor (PPI)

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  Explanation

  Although the most common cause of chronic cough in adults is the postnasal drip syndrome (not a choice in this question), the patient's cough is present only in the recumbent position and at night. This sign, as well as the fact that he has recently gained considerable amount of weight, point toward the correct diagnosis of GERD. All of the other answers are also potential causes of chronic cough among adults. The history and examination give some clues that point toward GERD (constant clearing of the throat, worse during recumbence, normal nasal mucosa, and worse after meals) and give some others that would make the alternative diagnoses less likely. While 4 months period is too long for a common cold, other infectious agents (including TB) are not likely given the lack of risk factors. It would be unusual for a patient to develop asthma at this age without other symptoms, and chronic bronchitis is even less likely given the remote history of smoking only a few cigarettes per day. Although nervous cough is also possible, this occurs more often as an escape from socially awkward situations or as a stress relieving method. Because the symptoms are due to GERD, they should be treated with a PPI as initial therapy. Although weight loss and exercise may be beneficial in relieving GERD symptoms, they should be considered additional therapies and not curative. Antibiotics are not necessary since the patient does not show signs or symptoms of bacterial or fungal infection. The use of cough suppressants and expectorants would temporarily improve the cough but would do nothing to address the underlying disorder. Inhaled bronchodilators such as beta-2 agonist play no role in the treatment of GERD, unless the patient was to develop pneumonitis and dyspnea.

• Question 383:

  Avascular necrosis is most likely to occur in fracture dislocations involving which of the following?

  A. the femoral head
  B. the shaft of the femur
  C. the shaft of the humerus
  D. the scapula
  E. the clavicle
  A. the femoral head

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  Explanation

  Avascular necrosis occurs following a fracture when the blood supply to a bone fragment is disrupted. The femoral head, humeral head, scaphoid, and talus are particularly vulnerable to this complication because of their precarious blood supply. A dense appearance of the bone on x-ray is a diagnostic clue. Radioisotope scanning can detect avascular necrosis at an earlier stage than is possible with roentgenography.

• Question 384:

  A 60-year-old woman arrives at your office for a routine physical examination. During the course of her examination she asks you about osteoporosis. She is concerned about her risk for osteoporosis, as her mother suffered from multiple vertebral compression fractures at the age of 60. Your patient reports that she still smokes cigarettes ("although I know they are bad for me") and has one alcoholic beverage a week. She reports having had menopause 5 years ago and experiencing a deep venous thrombosis approximately 20 years ago. She is proud of the fact that she regularly exercises at the local fitness center. She has been taking 1500 mg of calcium with 800 IU of vitamin D every day. You suspect that she is at risk for osteoporosis. After performing the appropriate imaging study, you determine that your patient has osteoporosis. Of the following choices, which is risk factor most likely contributing to her osteoporosis?

  A. active lifestyle
  B. late menopause
  C. cigarette smoking
  D. frequency of alcohol intake
  E. her intake of calcium and vitamin D
  C. cigarette smoking

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  Explanation

  DEXAis the newest, least expensive, and quickest method of assessing BMD. The precision of DEXAis approximately 12%. Standard radiography is inadequate for accurate bone mass assessment. Single photon absorptiometry is used to scan bone, which is in a superficial location with little adjacent soft tissue (e.g., radius). It may not be an accurate reflector of the density in the spine or hip, which are the sites of greatest potential risk for fracture. The quantitative CT scan and dual photon absorptiometry take more time, expose the patient to more radiation, and, in the case of quantitative CT scanning, significantly increase costs, when compared to DEXA. The major risk factors for osteoporosis are family history, slender body build, fair skin, early menopause, sedentary lifestyle, cigarette smoking, medications (corticosteroids or Lthyroxine), more than two drinks a day of alcohol or caffeine, and low calcium intake. The current recommendation for oral calcium in men and premenopausal women is 1000 mg/ day. Postmenopausal women and patients with osteoporosis should have 1500 mg calcium a day and 400800 IU of vitamin D, which promotes intestinal calcium absorption. This patient's intake of calcium and vitamin D is not a risk factor for osteoporosis.

  Alendronate is a bisphosphonate, which is approved for the prevention and treatment of postmenopausal osteoporosis. Among the many results of the WHI, it was found that combined estrogen plus progestin therapy was associated with an increased risk of nonfatal MI or death from coronary heart disease (CHD). Consequently, while it is recognized that postmenopausal women who are taking estrogen to alleviate postmenopausal symptoms may also experience skeletal benefits, the prevention of osteoporosis should not be a reason in itself to start estrogen therapy. Calcitonin inhibits osteoclastic bone resorption, but is not sufficiently potent to prevent bone loss in early postmenopausal women (within 5 years of menopause). It is best reserved for use in patients with osteoporosis unresponsive to other therapies. Raloxifene is a selective estrogen receptor modulator (SERM), which is effective for prevention of bone loss in early postmenopausal women and treatment of established osteoporosis, but it also increases the risk of venous thromboembolic disease which makes it an inappropriate choice for this patient

• Question 385:

  A 23-year-old African-American presents with acute-onset pain in the abdomen, back, and legs. On physical examination, his pulse is 115 bpm, respiratory rate is 20, blood pressure is 100/70 mmHg, and temperature is 101. There is scleral icterus, a s ystolic ejection murmur at the right upper sternal border, bilateral rhonchi, a right upper quadrant abdominal scar from a cholecystectomy, and a diffusely tender abdomen without rebound. A neurologic examination is normal. A peripheral blood smear is shown in Figure

  

  .

  Among the initial orders for this patient should be which of the following?

  A. broad-spectrum antibiotics for community-acquired pneumonia
  B. type and hold for 2 units packed RBCs
  C. an arterial blood gas
  D. a CT scan of the abdomen
  E. analgesics
  E. analgesics

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  Explanation

  This patient has sickle cell anemia. This is evident from sickle cells forms on the peripheral blood smear in Figure 1-13. Pain medication is an important initial concern. It is often difficult to determine whether a patient in sickle cell crisis has an ongoing infection. Infections can precipitate sickle cell crisis. With respect to community-acquired pneumonia, the diagnosis is difficult. A patient with sickle cell crisis can have fever as a result of the sickle crisis. They can have an increased respiratory rate, physical examination, and CXR findings which suggest pneumonia as a result of pulmonary infarctions. A white blood count can be elevated due to marrow stimulation. In the presence of the acute chest syndrome, characterized by chest pain, hypoxia, and CXR infiltrates, antibiotics would be indicated. Without further information, it is hard to decide to empirically start broad-spectrum antibiotics for community-acquired pneumonia. Transfusions should generally be avoided in patients with sickle cell anemia who are not symptomatic due to the anemia. Since patients in sickle cell crisis have intravascular hemolysis, their reticulocyte counts are usually high and they can replace their blood quickly. Repeated small transfusions will lead to autoantibodies that will make further transfusions difficult. Arterial blood gas determination should not be the first step, given the above information. A CT scan of the abdomen is not indicated given the nonspecific nature of the patient's abdominal findings. Parvovirus B19 can cause aplastic crisis in patients with hemoglobinopathies, including sickle cell disease. A tip to this diagnosis is the decreased reticulocyte count in a patient who normally would have a high reticulocyte count. Given the information listed above, there is no indication for broad- spectrum antibiotics. Splenectomy is not a reasonable alternative at this point. Patients with sickle cell disease have autosplenectomy by the time they are adults. A bone marrow biopsy maybe indicated because of the low platelet count, but not initially. GnCSF is not indicated because the patient does not have neutropenia.

  Patients with sickle cell disease typically have isosthenuria.

  This is due to repeated infarction of the renal papilli. This causes destruction and interference with the counter current mechanism that causes urine concentration. As a result, patients with sickle cell anemia have the inability to concentrate their urine. This results in fluid and electrolyte abnormalities. Patients in sickle cell crisis are usually fluid depleted. This and the sickled blood cells cause hyperviscosity and microinfarctions. There is no evidence that the patient has diabetes insipidus, which usually has a urine specific gravity less than 1.005. Patients with UTIs do not have isosthenuria due to RBCs and WBCs that increase the urine specific gravity. Sickle cell patients may have zinc deficiency, but this is not a cause of isosthenuria.

• Question 386:

  A 72-year-old male with type II diabetes, hypertension, and a history of recurrent pneumonia is admitted to the Medical intensive care unit (ICU) with a diagnosis of septic shock. His vital signs are:

  BP 80/60 mmHg, RR 24 breaths per minute, pulse 120 beats per minute (bpm), temp. 102.4, O2 saturation 99% on room air. Of the choices listed below, what would be your initial management?

  A. start IV dopamine
  B. start empiric IV broad-spectrum antibiotics
  C. bolus IV fluids
  D. intubate and start ventilator support
  E. start IV norepinephrine
  C. bolus IV fluids

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  Explanation

  Septic shock results from inflammatory effects secondary to infection that ultimately leads to hemodynamic decompensation. The treatment encompasses three primary goals. The initial priority is to maintain a reasonable mean arterial pressure and cardiac output to keep the patient alive. Then the nidus of infection must be treated and the pathogenic sequence leading to septic shock should be interrupted. While these latter goals are being pursued, adequate organ system perfusion and function must be maintained, guided by cardiovascular monitoring. Large fluid deficits exist in patients with septic shock. Up to 610 L of crystalloid solutions or 24 L of colloid solutions may be required for initial resuscitation in the first 24 hours. Volume repletion in patients with septic shock produces significant improvement in cardiac function and systemic oxygen delivery, thereby enhancing tissue perfusion and reversing anaerobic metabolism. Cardiac index will usually improve by 2540% during fluid resuscitation. In approximately 50% of septic patients who initially present with hypotension, fluids alone will reverse hypotension and restore hemodynamic stability. Fluid resuscitation with isotonic crystalloids, such as normal saline or lactated Ringers solution, should be the initial therapy in shock. When fluid resuscitation fails to maintain adequate arterial pressure and organ perfusion, vasopressor therapy should be initiated. In this patient, the initial therapy should be fluid resuscitation. If fluid resuscitation fails, then vasopressor therapy should be initiated with dopamine. If this alone fails, then adding another vasopressor/inotropic agent, such as norepinephrine, may be warranted.

  Although patients with septic shock should receive broad antibiotic coverage after being pan-cultured, this should not precede fluid resuscitation. As this patient is able to breathe independently while maintaining good O2 saturation, intubation may be held off for now. If the patient starts to deteriorate (increased respiratory rate, low O2 saturation, poor excursion, hypercapnia, hypoxia), intubation could be considered.

• Question 387:

  A 39-year-old woman presents to the office for the evaluation of a mole on her left arm. It has been present and enlarging over the past 6 months. It itches and occasionally bleeds. Which of the following statements regarding skin cancer is true?

  A. Skin types III and IV are more prone to developing melanoma.
  B. Squamous cell carcinoma only occurs in sun-exposed areas.
  C. Basal cell carcinomas do not occur in persons of African descent.
  D. Squamous cell carcinomas of the skin have a higher metastatic potential than basal cell carcinomas.
  E. A shave biopsy is recommended for the evaluation of suspicious pigmented lesions.
  D. Squamous cell carcinomas of the skin have a higher metastatic potential than basal cell carcinomas.

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  Explanation

  The mnemonic "ABCDE" is often used to remember some of the attributes of skin lesions that would make them more suspicious for being malignancies. "A" is for asymmetry; "B" for border that is irregular or indistinct from the surrounding skin; "C" for color such as dark black or variations in colors within the same lesion; "D" for diameter greater than 6 mm, or larger than the size of a pencil eraser; "E" for elevation of the presence of a diameter of greater than 6 mm would be lesion with surface irregularity. Of the choices considered a higher-risk attribute. Primary skin malignancies are divided into three major categories--basal cell carcinoma, squamous cell carcinoma, and melanoma. Basal cell carcinomas may grow large and be locally destructive, but they have the lowest metastatic potential of the three types of skin cancer. Basal cell carcinomas are more common in persons with fair complexions but they occur in all skin types and colors. Squamous carcinomas of the skin have a metastatic potential greater than basal cell carcinomas and less than malignant melanomas. Squamous carcinomas most commonly occur in sun-exposed areas but are also associated with other etiologies, such as human papilloma virus (HPV), and can occur anywhere on the body.

  Malignant melanoma has the highest metastatic potential of the primary skin malignancies. Melanoma can occur in any skin type, but is more common in skin types I and II (fair skin). Obtaining a tissue sample for pathologic studies of suspicious skin lesions is critical for diagnosis and planning of appropriate treatment of melanoma. The thickness of the lesion is an important factor in these decisions. Therefore, shave biopsy would be inappropriate for the evaluation of a pigmented lesion. Complete excisional biopsy would be preferable, or, when that is not possible, full-thickness punch biopsy is an acceptable alternative. While sun exposure is an important risk factor for all types of skin cancers, for melanomas there is some evidence that intermittent, intense sun exposure and sunburning is more of a risk than cumulative sun exposure. Actinic keratoses are sun-induced skin lesions that are considered risks for the development of squamous carcinomas. They can be treated with local destructive methods, such as cryosurgery or the topical chemotherapeutic agent 5-fluorouracil. Protection of susceptible skin from excessive sun exposure from childhood is important in reducing the risk of developing skin cancer. Precautions such as wearing broad- brimmed hats, long sleeved clothing, and avoidance of intense midday sunlight are helpful. Using chemical sunscreens with SPF of greater than 15 with frequent reapplication is also beneficial. Even "waterproof" sunscreens need to be reapplied after bathing or swimming.

  Awet cotton T-shirt provides very little, if any, protection from ultraviolet light exposure. Both the UV-A and UV-B rays play roles in skin damage from the sun and it is important to use sun protection products, which block both types of rays. Sun tanning booths are also considered risks for the induction of skin damage and skin cancer as they expose skin to potentially damaging ultraviolet rays.

• Question 388:

  During laparoscopic abdominal procedures, the abdominal cavity is usually insufflated with carbon dioxide to a pressure of 15 mmHg. Increasing the intra-abdominal pressure to these levels produces which of the following1 physiologic responses?

  A. decreased afterload
  B. depressed cardiac output
  C. hypercarbia
  D. depressed diaphragm
  E. alkalosis
  C. hypercarbia

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  Explanation

  Increasing abdominal pressures for laparoscopic procedures has several systemic effects. By increasing the carbon dioxide, patients become hypercarbic and acidotic. There is decreased venous return and increased afterload. The peritoneum is distended and the diaphragm elevated. In patients with normal cardiac function, cardiac output is not affected until the abdominal pressures reach about 20 mmHg.

• Question 389:

  An 18-year-old female presents for follow-up of a rash. She states that she has been using OTC antifungal preparations without success. She used OTC cortisone cream with mild improvement, but the lesions never disappeared. Her condition also recurred with full severity once the cortisone cream was discontinued. Her family history reveals a first degree relative with similar rash. The rash is over the elbows, trunk, and scalp .

  Which other physical finding would be consistent with your presumptive diagnosis?

  

  

  A. velvety, hyperpigmented patches over the axilla and neck
  B. pitting of the nails
  C. oily scalp
  D. subcutaneous nodules
  E. multiple tender and tense vesicles and bullae
  B. pitting of the nails

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  Explanation

  Psoriasis is a benign chronic, inflammatory skin disorder with a genetic basis that affects approximately 2% of the population in the United States. The condition varies in its presentation from person to person, with some having only local involvement and others having a severe generalized involvement. The incidence occurs in a bimodal distribution, with peaks persons in their 20s and 50s. Those with earlier onset generally will have a more severe disease over the course of their lifetime. Psoriasis has several variants, or subtypes, including plaque type (most common), eruptive (guttate), generalized pustular, and erythrodermic psoriasis. Some patients may be asymptomatic or may have only minor itching. Others may have involvement of most of their body, with severe disfigurement and poor quality of life. Psoriasis may involve any skin area; however, areas such as the scalp, extensor surfaces, palms, soles, and nails should always be examined. The typical lesions are described as erythematous, well- demarcated plaques with overlying scales. Fine stippling (pitting) of the nails is highly suggestive of psoriasis. In addition to the skin findings, patients may also have arthritis. The lesions can be reactivated with local injury or irritation of normal skin (Koebner phenomenon). The diagnosis is predominantly clinical, based on the history and examination. There are no laboratory measures that will diagnose psoriasis. Skin biopsy, although not pathognomonic, would show features consistent with psoriasis and would help to rule out other similar appearing conditions.

• Question 390:

  Asmall area of abnormality is noted on the lateral wall of the urinary bladder during a cystoscopy on a patient being evaluated for asymptomatic microscopic hematuria. Biopsy of the lesion is most likely to reveal which of the following?

  A. adenocarcinoma
  B. neuroendocrine carcinoma
  C. rhabdomyosarcoma
  D. squamous cell carcinoma
  E. papillary transitional cell carcinoma
  E. papillary transitional cell carcinoma

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  Explanation

  Papillary cancer arises most frequently from the lateral and posterior bladder walls. At cystoscopy, tumors may be small, delicate, lowgrade papillary lesions limited to the mucosal surface or larger high grade, solid, and invasive which are often ulcerated. Papillary and exophitic cancers tend to be better differentiated. Infiltrating tumors are usually more anaplastic. Nonurothelial forms of bladder cancer are squamous cell carcinomas, adenocarcinomas, neuroendocrine carcinomas, and rhabdomyosarcomas.

  The frequency of these tumors is much lower