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

USMLE USMLE-STEP-3 Online Questions & Answers

• Question 221:

  You are asked to see an inpatient for a gynecologic consultation. The patient is an 85-year-old female who was admitted s/p her third stroke. She has a history of dementia, coronary artery disease, insulin- dependent diabetes, and hypertension. She resides in a local nursing home and normally requires extensive nursing assistance as she is unable to care for herself. While in the hospital, the nursing staff observed a small amount of new vaginal bleeding. Her past OB/GYN history is unknown and no family members are immediately available for clarification. On physical examination, she is lying comfortably in bed, awake but not oriented to person, place, or time. She is unable to speak coherently, and becomes combative when you attempt to examine her abdomen. She quiets down when you step out of the room.

  You then receive a telephone call from someone who says she is the patient's granddaughter, inquiring as to the patient's status and your recommendations. What should be yor response?

  A. "Your grandmother is very sick. We will be taking her to the operating room this afternoon. Would you please give us permission to do that over the telephone?"
  B. "In order to respect patient confidentiality and privacy, I am unable to discuss patient-related issues without explicit permission from her or her designated decision maker."
  C. "In her current condition, I believe that she has too many other medical problems to workup her vaginal bleeding. I will not be seeing her again unless something changes."
  D. "Please call back later after we have completed her examination."
  E. "I cannot give you information over the phone but could give you any information that you want if you come to the hospital and can prove to us that you are related to the patient."
  B. "In order to respect patient confidentiality and privacy, I am unable to discuss patient-related issues without explicit permission from her or her designated decision maker."

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  Explanation

  At this point in time, the patient would appear to be incapacitated, and unable to provide informed consent for herself. Given her baseline medical conditions, one would hope that the patient has a durable power of attorney for health care, with a designated surrogate decision maker. All attempts should be made to contact that person prior to initiating any procedures or surgery. It is unclear at this point in time as to whether or not this patient's dementia is being impacted by delirium. Restraints and/or additional sedation would not be appropriate unless the patient is posing harm to herself or others.

  In 1996, Congress enacted the Health Insurance Portability and Accountability Act (HIPAA). It provides standards for health information transactions and security of patient data. Under the HIPAA regulations, Health care providers must obtain the individual's written consent prior to disclosure of health information except in the management of emergencies or if the consent can be inferred from a patient with impaired communication. In this situation, where the patient is not capable of giving this consent, efforts should be made to identify a surrogate decision maker. As that person has not yet been identified, it would be appropriate to ask the caller if she could assist in identifying a previously designated decision maker. However, it would not be appropriate to disclose protected information to her at this time.

• Question 222:

  A recent study compared two drugs--exemestane and tamoxifen--for the treatment of estrogenreceptor positive breast cancer in postmenopausal women. At the end of the study, 91.5% of the women treated with the drug exemestane and 86.8% of the women treated with tamoxifen were disease free (P < 0.001).

  What is the absolute risk reduction (ARR) for the development of recurrent breast cancer for women taking exemestane compared to women taking tamoxifen?

  A. 95.3%
  B. 72%
  C. 64%
  D. 36%
  E. 4.7%
  E. 4.7%

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  Explanation

  Explanations:

  Relative risk is the percentage of subjects who achieve an outcome in one experimental group divided by the percentage of subjects who achieve the same outcome in another group. This statistic is used frequently in placebo-controlled trials, where the comparison occurs between the experimental group and the control group. In the study referenced in this set of questions, the comparison is between two groups who were given two different active medications exemestane and tamoxifen. The outcome studied here is the development of recurrent breast cancer. The data presented state that after the course of treatment, 91.5% of the women in the exemestane group and 86.8% of the women in the tamoxifen group were disease free. Therefore, 8.5% in the exemestane group and 13.2% in the tamoxifen group developed the outcome of recurrent breast cancer. The relative risk is then calculated as 0.085/0.132 = 0.64 = 64%. The relative risk reduction is the percentage by which the risk in one group has been reduced when compared to the other group. In other words, if the rate of an outcome in one group is 100%, the relative risk reduction is the difference between 100% and the measured relative risk. It is calculated by the formula:

  Relative risk reduction = 1 - relative risk In this example, the relative risk reduction is 1 - 0.64 = 0.36 = 36%.

  The ARR, also known as the risk difference, is calculated by subtracting the percentage of subjects who achieve an outcome in one group from the percentage who achieve the outcome in another. In this study, the ARR for those in the exemestane group compared to those in the tamoxifen group is 13.2% - 8.5% = 4.7%. The NNT is the number of subjects who need to receive an intervention (such as a medication) in order for one of them to have a beneficial outcome. In this study, the beneficial outcome would be one less case of recurrent breast cancer. The NNT is calculated as 1/ARR. In this case, the NNT = 1/0.047 = 21. In other words, 21 women need to be treated with exemestane in order for there to be one fewer case of recurrent breast cancer compared to women treated with tamoxifen.

• Question 223:

  A23 year old female presents to the emergency department (ED) with "abdominal cramping" nausea, and vaginal bleeding. Ahuman chorionic gonadotropin (hCG) level returns 5150 mIU/mL. A vaginal probe ultrasound is performed and notes no evidence of an intrauterine pregnancy, normal appearing ovaries, a mild amount of fluid in the cul-de-sac, and no evidence of ectopic gestation.

  The ED physician can exclude which diagnosis from the differential?

  A. spontaneous abortion
  B. ectopic pregnancy
  C. singleton intrauterine pregnancy
  D. ruptured ovarian cyst (corpus luteum)
  E. molar pregnancy
  C. singleton intrauterine pregnancy

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  Explanation

  Differentiating between an ectopic pregnancy, an early intrauterine pregnancy, or a miscarriage is a common dilemma for the ED physician. Transabdominal ultrasound (TAUS) requires a -hCG level of 6500 mIU/mL before an intrauterine gestation can be confidently visualized. Transvaginal ultrasound (TVUS) is the most accurate means of confirming intrauterine pregnancy and gestational age during the early first trimester. TVUS can help detect signs of intrauterine pregnancy approximately 1 week earlier than TAUS because it has a lower discriminatory zone (-hCG level between 1000 and 1500 mIU/mL). ATAUS that does not detect an intrauterine gestational sac with a -hCG level higher than 6500 mIU/mL or a TVUS examination that does not detect an intrauterine gestational sac when the - hCG level is higher than 1500 mIU/mL suggests an ectopic pregnancy. The literature provides a wide range of sensitivities and specificities for transvaginal ultrasonography in the detection of ectopic pregnancy.

  Sensitivities range from 69 to 99%, and specificities range from 84 to 99.6%.

• Question 224:

  A19-year-old college student is found to have an elevated serum calcium on routine physical examination. She has a family history of hypercalcemia that has not resulted in any known symptoms. Further workup reveals a slightly elevated serum parathyroid hormone with depressed levels of serum phosphate. A 24- hour urine calcium excretion is obtained and is low. Which of the following is the correct diagnosis?

  A. familial hypocalciuric hypercalcemia (FHH)
  B. primary hyperparathyroidism
  C. secondary hyperparathyroidism
  D. tertiary hyperparathyroidism
  E. metastatic bone cancer
  A. familial hypocalciuric hypercalcemia (FHH)

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  Explanation

  FHH, or familial benign hypercalcemia, is a rare condition characterized by asymptomatic or mildly symptomatic hypercalcemia. It is inherited as an autosomal dominant trait and the parathyroid glands are usually normal in size. The basis for the development of FHH appears to be mutations in the calcium- sensing receptor gene which regulates the parathyroid gland set point and modulates the extracellular calcium concentration. The condition may be mistaken for primary hyperparathyroidism because, in both conditions, the serum calcium and parathyroid hormone levels are elevated with a concomitant low serum phosphate. The distinction is made by obtaining a 24-hour urine calcium excretion level. In patients with FHH, the urine calcium level is low, whereas in primary hyperparathyroidism the level is high. The distinction is important, as patients with primary hyperparathyroidism benefit from surgery and those with FHH do not.

• Question 225:

  The specimen shown in Figure below, was removed during an exploratory laparotomy of a 22-year-old male who went to surgery because of an intestinal obstruction. What is the most likely diagnosis for the lesion shown in this image?

  

  A. intestinal infarction
  B. ulcerative colitis
  C. Crohn's disease
  D. intestinal tuberculosis
  E. small bowel carcinoma
  C. Crohn's disease

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  Explanation

  This image shows the typical segmental involvement of the terminal ileum seen in Crohn's disease. There is no evidence for hemorrhagic infarction. Ulcerative colitis may involve the terminal ileum, but is less likely as are intestinal tuberculosis and small bowel carcinoma.

• Question 226:

  A41-year-old woman, recently diagnosed with a 2-cm, stage IB1 cervical cancer, undergoes a radical hysterectomy, bilateral salpingooophorectomy, and retroperitoneal pelvic lymph node dissection. Her surgery and postoperative course are uncomplicated. Four weeks postoperatively, she presents to the ER complaining of left leg swelling and left lower quadrant abdominal pain. On physical examination, she is afebrile, has a normal WBC count, and you palpate a 5 4 cm mass in the left lower quadrant. You order a pelvic ultrasound that shows a 5 5 cm simple cyst in the left lower quadrant.

  Which of the following is the most likely diagnosis?

  A. deep venous thrombosis (DVT)
  B. lymphocyst
  C. ovarian cyst
  D. diverticular abscess
  C. ovarian cyst

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  Explanation

  The incidence of lymphocyst formation following radical hysterectomy and pelvic lymphadenectomy ranges as high as 30%, but is less than 5% if only symptomatic cysts are counted. Risks for lymphocyst formation include lymphadenectomy, radiation therapy, lymph node metastases, and closure of the pelvic peritoneum. From a surgical standpoint, closure of the pelvic peritoneum traps the lymph fluid in the retroperitoneal space and prevents absorption by the peritoneal membrane. Most lymphocysts are small, asymptomatic, and clinically insignificant. Large lymphocysts can produce serious consequences including venous obstruction with DVT, ureteral obstruction, leg edema, and pain. Bilateral lymphocysts can cause obstructive renal failure. The diagnosis is made most easily and accurately by pelvic ultrasound. Large or symptomatic pelvic lymphocysts can almost always be managed by percutaneous drainage with a pigtail catheter placed under CT or ultrasound guidance. A pelvic DVT following gynecologic surgery should be in the differential for this patient. Typically, DVT following pelvic surgery is asymptomatic, but the appearance of leg edema, pain, or tenderness in the calf, popliteal space, or inguinal triangle is highly suspicious. Erythema and fever are uncommon. A pelvic DVT is uncommon compared to a more distal DVT in the lower extremity venous system. Women with a pelvic DVT will not have the classic symptoms associated with a calf DVT. The diagnostic test to evaluate for a DVT would be a lower extremity venous duplex ultrasound.

• Question 227:

  A 10-year-old male has a history of seizures which are controlled with dilantin. The child also has asthma and often uses an albuterol inhaler. Which of the following asthma medications can lower the seizure threshold in children?

  A. theophylline
  B. salmeterol
  C. beclomethasone
  D. montelukast
  E. nedocromil
  A. theophylline

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  Explanation

  Theophylline, a methylxanthine, has an excitatory effect on the CNS. This serious side effect, in conjunction with its very narrow therapeutic window, has made theophylline use very uncommon. The use of any of the other medications listed would be recommended before consideration of the use of theophylline.

• Question 228:

  A65-year-old female presents with ascites, multiple peritoneal implants, and a large abdominopelvic mass. At laparotomy, she is found to have omental disease, splenic metastases, retroperitoneal lymphadenopathy, and bilateral pelvic masses with rectosigmoid involvement posteriorly and bladder involvement anteriorly. The appropriate surgical management for this patient would be which of the following?

  A. bilateral salpingo-oophorectomy, followed by postoperative chemotherapy
  B. total abdominal hysterectomy and bilateral salpingo-oophorectomy, followed by postoperative chemotherapy
  C. complete omentectomy, retroperitoneal lymphadenectomy, total abdominal hysterectomy, and bilateral salpingooophorectomy, followed by postoperative chemotherapy
  D. peritoneal stripping, splenectomy, complete omentectomy, retroperitoneal lymphadenectomy, total abdominal hysterectomy, and bilateral salpingo-oophorectomy, followed by postoperative chemotherapy
  E. rectosigmoid resection with reanastomosis, peritoneal stripping, splenectomy, complete omentectomy, retroperitoneal lymphadenectomy, total abdominal hysterectomy, and bilateral salpingooophorectomy, followed by postoperative chemotherapy
  E. rectosigmoid resection with reanastomosis, peritoneal stripping, splenectomy, complete omentectomy, retroperitoneal lymphadenectomy, total abdominal hysterectomy, and bilateral salpingooophorectomy, followed by postoperative chemotherapy

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  Explanation

  Despite decades of effort aimed at improving methods of early detection and diagnosis, the majority of cases of cancer of the ovary are not diagnosed until the disease has spread beyond the ovary. The surgical management of epithelial ovarian cancer consists of attempts at maximal surgical cytoreduction at the time of surgical exploration. The surgical goal is to remove all disease, such that at the completion of the debulking procedure no visible remaining disease is present. In order to accomplish this goal, extensive surgical procedures are often required in those patients presenting with advanced stage disease. Griffiths et al. reviewed the theoretical basis for cytoreductive surgery. Complete removal of bulky ovarian tumor masses improves patient survival when compared to inadequate or incomplete surgical cytoreduction, in three specific ways:

  1. Maximal surgical debulking enables the resection of hypoxic tumor sanctuaries in which viable tumor cells have the ability to escape exposure to adequate concentrations of chemotherapy postoperatively.

  2. Maximal surgical debulking enables the resection of large tumor masses containing chemoresistant tumor clones that do not respond well to any form of postoperative chemotherapy.

  3. Maximal surgical debulking enables the resection of large tumor masses, thereby reducing the tumor burden to such an extent that all remaining cells in the G0 resting state will now return to the actively dividing cell cycle, where they are more amenable to chemotherapeutic damage and ultimate cell kill. Numerous investigators (Griffiths, Munnell, Delclos and Quinlan, Hoskins, Eisenkop) have consistently confirmed the biggest single prognosticator predicting how well a patient will respond, and how long they will live, following treatment for ovarian cancer is the volume of disease remaining following their initial surgical debulking. Patients left with residual deposits of disease >2 cm in diameter are considered suboptimally debulked and do no better than patients who have no surgical debulking procedure performed. Optimal surgical cytoreduction, on the other hand, is defined as no residual deposit of disease remaining greater than 1 cm in maximal dimension. The smaller the residual disease remaining (no deposit >.5 cm, no deposit >.25 cm, and so on), the longer the overall survival of the patient, with those left with no visible remaining disease having the longest overall survival of all as a rule. Given the immense amount of retrospective data supporting the importance of optimal surgical debulking in the patient's overall outcome and survival, all attempts must be made at the time of initial surgical cytoreduction to obtain an optimal debulking, preferably one with no visible remaining disease at completion

• Question 229:

  Implantation of the embryo into the endometrium occurs how many days after ovulation?

  A. 1
  B. 2
  C. 4
  D. 6
  E. 10
  D. 6

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  Explanation

  Following ovulation, fertilization of the egg by the sperm occurs in the Fallopian tube. The embryo then divides and grows as it migrates down the Fallopian tube and into the uterine cavity. As early as 6 days postovulation the embryo implants in the uterine endometrium. Trophoblast invasion then occurs allowing the embryo to burrow into the endometrium. A uteroplacental circulation is established by 1112 days after ovulation allowing -hCG to be detectable in maternal serum or urine.

• Question 230:

  A 32-year-old man who is HIV-positive was found to have Burkitt's lymphoma with diffuse bulky abdominal disease. He now reports to the hospital and is scheduled to begin chemotherapy. Admission laboratory studies show elevations of his uric acid at 15 mg/dL, serum phosphorus at 8.5 mg/dL, creatinine at 2.9 mg/ dL, and potassium at 6.1 mEq/L.

  What therapy is most likely to reverse the patient's metabolic abnormalities?

  A. administration of intravenous saline with mannitol to try to keep urine output >2.5 L/day
  B. allopurinol 300 mg/day
  C. administration of intravenous sodium bicarbonate to keep urinary pH >7.0
  D. hemodialysis
  E. administration of the recombinant uricase enzyme rasburicase to lower uric acid levels
  D. hemodialysis

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  Explanation

  This patient has tumor lysis syndrome (TLS), a group of metabolic derangements due to rapid cell turnover with release of intracellular contents, such as phosphate and potassium, and increased purine metabolism, leading to hyperuricemia. It is usually seen after the initiation of cytotoxic chemotherapy, but occasionally occurs spontaneously in patients with bulky disease such as Burkitt's lymphoma. The uric acid crystallizes in the renal tubules and can cause oliguric renal failure. Once renal failure has occurred, patients usually require hemodialysis until renal function recovers. Each of the other choices may be employed to prevent the development of TLS in high-risk patients prior to beginning chemotherapy