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

USMLE USMLE-STEP-3 Online Questions & Answers

• Question 71:

  Vitamin D supplementation can be helpful in treating which disease?

  A. hyperparathyroidism
  B. hypoparathyroidism
  C. alcoholic neuritis
  D. pernicious anemia
  E. scurvy
  B. hypoparathyroidism

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  Explanation

  Vitamin D is actually a hormone that, along with parathyroid hormone and calcitonin, regulates plasma calcium concentration. One action of vitamin D is to increase plasma Ca2+, which can be reduced in hypoparathyroidism. Scurvy is associated with vitamin C deficiency. Alcoholic neuritis is associated with thiamine deficiency.

• Question 72:

  A 29-year-old married male is seen in the emergency room with the chief complaint of, "I'm afraid I'm having a heart attack." He states a 2-month history of experiencing recurrent episodes of chest pain and shortness of breath that last 1020 minutes. He also describes associated tachypnea, lightheadedness, tingling in his extremities, nausea, diaphoresis, anxiety, and fears that he may die. These symptoms are now occurring almost daily but are not provoked by any situations or activities such as exertion or exercise. He is significantly worried about having future episodes and is genuinely concerned that he will suffer a myocardial infarction. He denies having any medical illnesses or taking any medications. He drinks three beers on the weekends only and does not use illicit drugs. His physical examination reveals a slightly elevated BP and pulse. An ECG demonstrates sinus tachycardia.

  Which of the following medications would be most appropriate in the acute management of this patient's symptoms?

  A. bupropion (Wellbutrin)
  B. buspirone (Buspar)
  C. imipramine (Tofranil)
  D. lorazepam (Ativan)
  E. paroxetine (Paxil)
  D. lorazepam (Ativan)

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  Explanation

  This patient is most likely experiencing panic attacks as part of panic disorder. Dopaminergic antidepressants such as bupropion have not demonstrated significant efficacy in panic disorder. Buspirone is approved in the treatment of GAD but is not useful in panic disorder. While tricyclic antidepressants, such as imipramine, and SSRIs, such as paroxetine, are both effective in the treatment of panic disorder, therapeutic benefit for both may require several weeks. Benzodiazepines, such as lorazepam and alprazolam, have been shown to be effective in the treatment of panic disorder. Their more rapid onset of action (hours to days) make them ideally suited for the immediate and acute management of panic attacks. Neither bupropion nor buspirone are considered to be first-line treatments for panic disorder. Imipramine and other tricyclic antidepressants have demonstrated their efficacy in panic disorder. The disadvantages are several: the need to increase up to a therapeutic dose over time, a significant side effect profile, and lethality in overdose. While benzodiazepines such as alprazolam are also effective in the long-term treatment of panic disorder, their potential for abuse and withdrawal if/when tapered make them less than ideal overall. It is not unusual to initiate a benzodiazepine for more immediate relief of anxiety along with another agent that will require a longer time period until its benefits become apparent. Given their proven efficacy, reduced side effects, lack of abuse potential and safety in overdose, SSRIs such as paroxetine are the most suitable choice for the long-term pharmacotherapy of panic disorder.

• Question 73:

  Which of the following patients is most likely to have symptoms of the carcinoid syndrome?

  A. patient with carcinoid tumor localized to the appendix
  B. patient with carcinoid tumor of the small intestine and a 3-cm nodule in the liver seen on CT scan
  C. patient with an apple core lesion seen on barium enema
  D. patient with adrenal mass and elevated levels of urinary vanillylmandelic acid(VMA)
  E. patient with a retroperitoneal carcinoid tumor
  E. patient with a retroperitoneal carcinoid tumor

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  Explanation

  Carcinoid syndrome is seen in less than 10% of patients with metastatic carcinoid disease. It is seen in patients with elevated serotonin levels, which is metabolized by the liver. Thus, only patients with massive hepatic metastasis or with tumors that bypass the hepatic filter--such as a retroperitoneal tumor--show symptoms. 5-Hydroxyindoleacetic acid (5-HIAA) levels can be tested in the urine to give the diagnosis (urinary vanillylmandelic acid [VMA] is indicative of a pheochromocytoma). An apple core lesion on the colon is most likely to be a large adenocarcinoma, which would not be associated with carcinoid symptoms. Common symptoms of carcinoid syndrome include flushing, diarrhea, right heart failure, and asthma.

  Weight loss and liver failure are uncommon symptoms.

• Question 74:

  Biopsy of a 4-cm sessile polyp of the cecum during a routine screening colonoscopy reveals it to be a villous adenoma with atypia. Attempt at piecemeal snare polypectomy through the colonoscope is unsuccessful. Which of the following is the most appropriate management?

  A. right hemicolectomy
  B. colonoscopy with electrocoagulation of the tumor
  C. colonoscopy with repeat biopsy in 6 months
  D. open surgery with colotomy and excision of polyp
  E. external beam radiation
  A. right hemicolectomy

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  Explanation

  Villous adenoma is a premalignant condition. The incidence of carcinoma in a polyp depends on the histology type and size of the polyp. Tubular adenomas are the most common type of polyps (6080%), but are the least likely to harbor carcinoma (less than 5% if smaller than 1 cm in diameter). Villous adenomas are the least common type, but overall the most likely to contain malignant foci (50% if greater than 2 cm in diameter). In this patient, a formal right hemicolectomy is indicated due to the high probability of finding cancer in the specimen. A lesser operation, such as open or laparoscopic polypectomy, would then require a second operative procedure if cancer is present. Colonoscopic fulguration of such a large lesion carries a high risk for perforation and would not allow histologic examination. Observation with repeat colonoscopy in 1 year is also inappropriate.

• Question 75:

  A 19-year-old woman comes in for a routine obstetrical follow-up visit at 24 weeks' gestation. She is here with her boyfriend, who is the father of the baby. She is wearing dark sunglasses in the examination room. When you ask her to remove the glasses, you see that she has a bruise around her left eye. Her boyfriend quickly states that she accidentally bumped into a door and she quietly nods in agreement. Which of the following statements about domestic violence is true?

  A. All states require that physicians report partner violence to the police.
  B. Domestic violence is rare in same sex couples.
  C. A woman cannot make a sexual assault claim against her husband.
  D. Domestic violence is less likely when one partner is ill or disabled.
  E. Psychological intimidation without violence is considered a form of abuse.
  E. Psychological intimidation without violence is considered a form of abuse.

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  Explanation

  Domestic violence is an abuse of power in a relationship in which a more powerful person exerts inappropriate control or domination over a less powerful person. Abuse is not only physical, but also can be emotional, sexual, or economic. Intimidation and psychological abuse also occur and are used sometimes by batterers in place of physical violence. Domestic, or partner, violence occurs in all types of relationships, regardless of the gender of the partners. The risk of violence increases in many situations, which exaggerate the disparity in power in the relationship, such as illness or disability in one of the partners. Pregnancy, especially unintended pregnancy, may also increase the risk of battery. Laws regarding the reporting of domestic violence vary from state to state. Many states do not require the reporting of domestic violence when the abused is a competent adult. Marriage, in and of itself, does not prevent a partner from making a sexual abuse charge against the other partner. Management in the setting of partner violence can be difficult. Providing information and referrals to appropriate shelters and services is critical. Assisting with the development of emergency plans may be of benefit as well. Asking about the availability of weapons in the home is important, as up to half of female murder victims are killed by a current male partner or ex-partner. At this time, reporting to the Child Protective Services is inappropriate, as they cannot intervene. After the baby is born, however, any sign of child abuse should be immediately reported.

• Question 76:

  A39-year-old woman with a long-standing history of normal pap smears undergoes a total abdominal hysterectomy for a large uterine fibroid and menorrhagia. Six months after her hysterectomy she had a negative vaginal pap smear from the vaginal apex. She presents to your clinic today for a routine physical examination. Based on the American College of Obstetricians and Gynecologists recommendations, when should this patient have pap smears?

  A. yearly
  B. every 3 years
  C. every 5 years
  D. never again
  E. only if she develops risk factors
  E. only if she develops risk factors

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  Explanation

  This patient, who had a hysterectomy for a benign condition, no longer needs pap smear screening as long as she is monogamous and does not develop risk factors for cervical dysplasia. The incidence for vaginal dysplasia after hysterectomy for benign disease is approximately 0.13%. Invasive carcinoma of the vagina is rare, and screening for this cancer is not cost-effective. However, women who had a hysterectomy for cervical dysplasia or cancer are at increased risk for vaginal dysplasia and should continue to have vaginal pap smears. It is also reasonable to reinitiate pap smear screening in women who had a hysterectomy for benign disease if they have new sexual partners or new risk factors. Apap test is also indicated if patients present with vaginal spotting or bleeding

• Question 77:

  You are evaluating a journal article describing a test for the diagnosis of congestive heart failure (CHF). In the study described, 250 consecutive patients were given the test. Of the 250 subjects, 106 tested positive for CHF and 144 tested negative. All 250 subjects were then evaluated by expert cardiologists who were blinded to the results of the experimental test. These cardiologists determined that of the 106 persons who tested positive, 95 actually had CHF. Further, the cardiologists found that of the 144 who tested negative, 2 truly had CHF.

  What is the sensitivity of this test for the diagnosis of CHF?

  A. 98%
  B. 93%
  C. 75%
  D. 61%
  E. 39%
  A. 98%

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  Explanation

  Explanations:

  Understanding the concepts of sensitivity, specificity, PPV, and NPV is crucial to interpreting diagnostic test results. Sensitivity is defined as the percentage of people who have a disease who test positive for that disease. Specificity is defined as the percentage of people who are free of a disease who test negative. These two concepts are considered characteristics of the specific test in question and are independent of the prevalence of the disease in the population. The PPVs and NPVs of a test are the test's clinical characteristics and these concepts are directly related to the prevalence of the disease in the population. The PPV is the percentage of people who have a positive test result who actually have the disease. Similarly, the NPV is the percentage of people who have a negative test result who don't have the disease.

  While the definitions may seem subtly different, the implications are significant. The usual way to calculate sensitivity, specificity, PPV, and NPV is with the table, using the following definitions

  

  The definitions of sensitivity, specificity, PPV, and NPV would then be:

  Sensitivity = a/(a + c) Specificity = d/(d + b) PPV = a/(a + b) NPV = d/(d + c) The specific information in this question comes from an article describing a study of B-type natriuretic peptide (BNP) for the diagnosis of CHF. The data presented show that 106 persons tested positive using the BNP test. After comparison with the "gold standard," in this case, a review by expert cardiologists, 95 of these 106 were determined to truly have CHF. Therefore, 11 of the 106 were false positives and 95 were true positives. Similarly, 144 persons tested negative using the BNP test. Of these, 142 were confirmed as true negatives and 2 were determined to be false negatives.

  Putting these numbers into a table reveals:

  

  The calculations then become:

  Sensitivity = a/(a + c) = 95/(95 + 2) = 98% Specificity = d/(d + b) = 142/(142 + 11) = 93% PPV = a/(a + b) = 95/(95 + 11) = 90% NPV = d/(d + c) = 142/(142 + 2) = 99%

• Question 78:

  A24-year-old male medical student is admitted to the hospital for the evaluation of a 3-month history of bloody stools. The patient has approximately six blood stained or blood streaked stools per day, associated with relatively little, if any, pain. He has not had any weight loss, and he has been able to attend classes without interruption. He denies any fecal incontinence. He has no prior medical history. Review of systems is remarkable only for occasional fevers and the fact that the patient quit smoking approximately 8 months ago. A colonoscopy is performed and reveals a granular, friable colonic mucosal surface with loss of normal vascular pattern from the anal verge to the hepatic flexure of the colon. Biopsies reveal prominent neutrophils in the epithelium and cryptitis with focal crypt abscesses, and no dysplasia. The patient is diagnosed with ulcerative colitis.

  In addition to an increased lifetime risk of colon cancer, the patient is also at increased risk for which of the following tumors?

  A. hepatocellular carcinoma
  B. hepatoblastoma
  C. desmoid tumors
  D. small bowel lymphoma
  E. cholangiocarcinoma
  E. cholangiocarcinoma

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  Explanation

  Oral corticosteroids are a mainstay of firstline treatment for moderate-to-severe ulcerative colitis. Starting doses of 40 mg PO daily of prednisone, with a slow taper, are often effective in reducing colonic inflammation, although some patients are unable to wean steroids or maintain remission once achieved. The patient does not have dysplasia in any biopsy specimens, nor does he have signs of systemic toxicity, so a colectomy would be premature. Oral metronidazole is ineffective in ulcerative colitis.

  Cortisone enemas would be helpful if the patient had isolated left-sided disease, but it is doubtful that enema therapy would reach his hepatic flexure. Intravenous cyclosporine would be used in severe colitis as a last measure before colectomy but this patient is not yet sick enough to warrant such therapy. PSC occurs in approximately 3% of patients with ulcerative colitis and is its major liver complication. It is a chronic inflammatory condition of the biliary tree. It can typically manifest with elevated alkaline phosphatase and bilirubin levels, and results in diffuse stricturing and pruning of the biliary tree. Wilson disease, hereditary hemochromatosis and alpha-1 antitrypsin deficiency are not associated with ulcerative colitis and are not cholestatic liver diseases. Primary biliary cirrhosis could account for these laboratory findings, but is rare in both males and patients with ulcerative colitis. Patients with PSC are at increased risk of developing cholangiocarcinoma but not the other liver tumors mentioned. Patients with celiac sprue are at increased risk for small bowel cancers (adenocarcinoma, lymphoma). Patients with FAP are at increased risk to develop desmoid tumors.

• Question 79:

  You are asked to see a 74-year-old man who has been admitted for evaluation of abdominal pain. During his workup, he was found to have hemoccult positive stool and a CT scan that was concerning for a mass in his sigmoid colon.

  Which should be the next step in his treatment?

  A. cardiology consultation for preoperative clearance
  B. contrast enema to evaluate the lesion
  C. colonoscopy to biopsy the mass and rule out synchronous lesions
  D. sigmoidectomy to resect the mass and obtain mesenteric lymph nodes for staging
  E. positron emission tomography (PET) scan to determine if the lesion is cancerous
  C. colonoscopy to biopsy the mass and rule out synchronous lesions

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  Explanation

  In the workup of a lesion identified within the colon, the gold standard for diagnosis is colonoscopy. Colonoscopy allows for biopsy of the tissue to establish a diagnosis of cancer prior to removing the mass. Furthermore, it also enables examination of the rest of the colon to rule out synchronous lesions. Barium enemas continue to have a role in diagnosis, but are more useful identifying the level of the lesion particularly in the setting of obstruction. You would not proceed straight to surgical resection unless the patient presented with an obstruction. Finally, PET scans have no role in the diagnosis of colon cancer

• Question 80:

  A30-year-old separated female with borderline personality disorder is brought in by her roommate after she admitted to feeling suicidal and taking several handfuls of "an old prescription" some hours ago. Her vitals demonstrate a slight fever, elevated BP, and tachycardia. On physical examination, her pupils are dilated, she has a tremor, and she complains of "seeing scary faces." She also has noticeably dry mucous membranes.

  Which of the following medications should be immediately administered in the above case?

  A. benztropine
  B. flumazenil
  C. naloxone
  D. phentolamine
  E. physostigmine
  E. physostigmine

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  Explanation

  Overdose of benzodiazepines such as alprazolam would cause depressed rather than elevated vitals, as well as somnolence and ataxia. Opiates such as oxycodone, taken in large amounts, cause the classic triad of miosis, respiratory depression, and coma. Risperidone may cause excess sedation or orthostasis, but in high doses it may also cause extra-pyramidal symptoms including dystonic reactions. Monoamine oxidase inhibitors (MAOIs) such as tranylcypromine, when taken with tyraminerich foods, are likely to cause a hypertensive crisis consisting of hypertension, headache, stiff neck, sweating, and nausea/ vomiting. Tricyclic antidepressants such as amitryptyline have significant anticholinergic toxicity which can cause dry skin, dry mucous membranes, hyperpyrexia, tachycardia, mydriasis, restlessness, and psychotic symptoms such as hallucinations. Benztropine is indicated for the treatment of extra-pyramidal symptoms, such as acute dystonia. Flumazenil is used in benzodiazepine intoxication.

  Naloxone is the treatment of choice for opiate overdose. Phentolamine or other alpha- adrenergic blockers are employed to treat hypertensive crisis. Physostigmine is considered the treatment of choice for anticholinergic toxicity.