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

USMLE USMLE-STEP-3 Online Questions & Answers

• Question 551:

  A61-year-old man comes to your office for a checkup. He currently feels well and has no focal complaints. He has a past medical history significant for wellcontrolled hypertension, and his gallbladder was removed 3 years ago in the setting of acute cholecystitis. He does not smoke and drinks one to two alcoholic beverages per day. Family history is remarkable for colon cancer in his mother at age 45 and a brother at age 49. He has a sister who developed endometrial cancer at age 53. He has never undergone colon cancer screening and is interested in pursuing this. Which colorectal cancer screening test would be best for this patient?

  A. virtual colonoscopy (aka CT colography)
  B. barium enema alone
  C. barium enema with flexible sigmoidoscopy
  D. fecal occult blood testing three times
  E. colonoscopy
  E. colonoscopy

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  Explanation

  The patient should undergo screening colonoscopy, especially with his strongly positive family history of first-degree relatives developing colon cancer before age 50. Colonoscopy is the only test that can directly evaluate the entire colon and rectum. Most polyps can be removed completely at colonoscopy, and large lesions or masses can be directly biopsied. Virtual colonoscopy and barium enema combined with flexible sigmoidoscopy are good tests, but any positive findings on either of these tests would warrant further examination with colonoscopy. Barium enema alone is insufficient for screening. Fecal occult blood testing is helpful as a screening tool, but would be inadequate alone in this patient given his family history. The patient satisfies criteria for HNPCC, a syndrome seen in patients with germline mutations in DNA mismatch repair (MMR) genes. He has three first-degree relatives with cancer of the colorectum, endometrium, small bowel, ureter, or renal pelvis (all of whom are first-degree relatives of each other). The colorectal cancers involve at least two generations and at least one case was diagnosed before age 50. FAP involves a mutation of the APC gene and results in dense colonic polyposis, mandibular osteomas, and universal colon cancer at a young age unless colectomy is performed. Peutz Jeghers syndrome results in hamartomatous polyps of the gut as well as mucocutaneous pigmentation changes. Cronkhite-Canada syndrome manifests as GI polyposis, alopecia, cutaneous hyperpigmentation, malnutrition, and dystrophic fingernails. Turcot syndrome is a variant of FAP in which patients can also develop medulloblastoma, glioblastoma multiforme, and hypertrophy of retinal pigmented epithelium.

• Question 552:

  Which of the following statements regarding vaccinations of pregnant women is true?

  A. Women who will be beyond the first trimester of pregnancy during flu season should routinely receive the inactivated influenza vaccine.
  B. Pregnancy is an absolute contraindication to the hepatitis B vaccine.
  C. Women who test negative for rubella at their initial prenatal visit should routinely receive a rubella vaccine during their second trimester of pregnancy.
  D. Pregnant women who have not completed a Td primary series should start this series in the immediate postpartum period.
  E. Women who receive a rubella vaccination within 4 weeks of becoming pregnant should be advised of the high risk having a baby with congenital rubella syndrome.
  A. Women who will be beyond the first trimester of pregnancy during flu season should routinely receive the inactivated influenza vaccine.

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  Explanation

  Explanations:

  There is an increased risk of influenzarelated complications in pregnant women who contract influenza, therefore the influenza vaccine is recommended for all pregnant women who will be beyond the first trimester during influenza season. The live, attenuated influenza vaccine is contraindicated during pregnancy but the inactivated influenza vaccine is recommended. The hepatitis B vaccine contains only noninfectious hepatitis B surface antigen particles and poses no real or theoretical risk of fetal infection, whereas the disease hepatitis B may cause severe illness for the pregnant woman and chronic disease for the newborn. For these reasons, neither pregnancy nor lactation is a contraindication to vaccination with hepatitis B vaccine. All pregnant women should routinely be tested for immunity to the rubella virus and should be immunized postpartum if they have no measurable immunity. The rubella vaccine, like other live- virus vaccines, is contraindicated during pregnancy due to the theoretical risk of causing fetal infection. In reality, studies of women who were pregnant or soon became pregnant after receiving rubella vaccination showed that the risk is extremely small. Aregistry of 226 usceptible women who received the rubella vaccine between 3 months before and 3 months after conception showed no evidence of congenital rubella syndrome. Women who inadvertently receive this vaccine should be counseled about the theoretical risk involved, however this would not be considered a reason to terminate a pregnancy. Finally, Td toxoid is routinely indicated for pregnant women.

• Question 553:

  A 55-year-old woman with recurrent major depressive episodes presents for medical clearance prior to receiving electroconvulsive therapy (ECT) as she is deemed to be treatment refractory. She complains of pervasive depressive feelings and neurovegetative symptoms as well as suicidal ideation. She denies any physical complaints but is taking felodipine 5 mg daily for her hypertension, which has been well- controlled. Despite receiving a detailed explanation of the procedure, she remains "nervous" about receiving ECT and its potential complications. What should she be told is the most likely side effect from ECT?

  A. broken teeth
  B. fractures
  C. hypertension
  D. memory loss
  E. vomiting
  D. memory loss

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  Explanation

  ECT is considered a very safe procedure overall. The mortality rate is comparable to general anesthesia and childbirth. Unlike in years past, the routine use of muscle relaxants makes broken teeth and fractures unlikely. ECT should not raise BP appreciably in a patient with controlled hypertension. Nausea and vomiting are uncommon and can be minimized with antiemetics given during the ECT sessions. By far, the most common side effect is memory loss, which almost always resolves.

• Question 554:

  A 22-year-old female (G3P0020) presents to your office for an initial obstetric visit in her third pregnancy. She reports a sure LMP date approximately 6 weeks ago, with a history of regular cycles. Her two previous pregnancies ended in spontaneous abortions. She denies any significant medical or surgical history. She denies use of alcohol, tobacco, or illicit drugs, though she does report a history of IV drug use as a teenager. She is a full-time student. She reports that twins run in her family, but she does not have any family history of diabetes, hypertension, or congenital anomalies. On review of her prenatal labs that have already been drawn, you find that her human immunodeficiency virus (HIV) antibody test (enzyme-linked immunosorbent assay [ELISA]) is positive. Her test results are otherwise normal

  Which of the following is recommended to reduce the risk of perinatal transmission of HIV from mother to infant?

  A. A scheduled cesarean delivery can reduce the risk of transmission if the maternal viral load is greater than 1000 copies/mL.
  B. All pregnant women with HIV should receive highly active antiretroviral therapy regardless of severity of HIV infection.
  C. No treatment is required; the risk of perinatal transmission of HIV is quite low.
  D. All patients with HIV should be required to have a cesarean delivery.
  E. Treatment of opportunistic infections such as Pneumocystis carinii pneumonia in the mother is most important in reducing the perinatal transmission of HIV.
  A. A scheduled cesarean delivery can reduce the risk of transmission if the maternal viral load is greater than 1000 copies/mL.

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  Explanation

  Screening for HIV should be offered to all pregnant women as part of routine prenatal care. Screening for HIV infection is done using an enzyme immunoassay (EIA). If the screening test is positive, it may be repeated. Once the screening test is determined to be positive, a Western blot assay or immunofluorescent antibody assay (IFA) is done as a confirmatory test. If the confirmatory test is positive, the patient is then considered to be infected with HIV. Pregnant patients should be treated for HIV by the same standards as any other adult with HIV, though some consideration is given to selection of antiretroviral medications that are safest in pregnancy. Appropriate HIV-related care should not be deferred because of pregnancy. For patients with significant HIV disease, the combination of elective scheduled cesarean and antiretroviral therapy has been shown to be more effective than antiretrovirals alone at reducing perinatal transmission of HIV. In the absence of any therapy, the risk of vertical transmission is estimated at 25%. With zidovudine therapy, the risk is decreased to approximately 58%. When zidovudine is given in combination with elective cesarean for appropriate patients, the risk is decreased to approximately 2%. In a recent meta-analysis, perinatal transmission occurred in only 1% of treated women with RNA viral loads less than 1000 copies/ mL. Given the low risk of transmission in this group, it is unclear whether cesarean delivery would provide additional benefit. After reviewing this data, the American College of Obstetricians and Gynecologists Committee on Obstetric Practice has issued a Committee Opinion concerning route of delivery, recommending consideration of scheduled cesarean delivery for HIV-1-infected pregnant women with HIV- 1 RNA levels >1000 copies/mL near the time of delivery.

• Question 555:

  A previously healthy 34-year-old man, a lifelong nonsmoker, sought medical care at an Urgent Care Center for an upper respiratory infection. A chest x-ray was obtained, which revealed a peripherally located right lower lobe lung nodule. A follow-up CT of the chest showed the 1.8 cm nodule with multiple nonspecific calcifications, and no associated hilar or mediastinal adenopathy.

  What is the most appropriate next step?

  A. Refer the patient to a thoracic surgeon to evaluate for wedge resection for suspected malignancy.
  B. Repeat the CT chest in 3 months to assess for stability of the nodule.
  C. Refer the patient for a percutaneous needle biopsy of the lesion to rule out malignancy.
  D. Refer the patient to a pulmonologist to evaluate for possible bronchoscopy with transbronchial biopsy.
  E. Treat with empiric antibiotics for possible pneumonia and repeat the chest x-ray in6 weeks to see if the nodular opacity has resolved.
  B. Repeat the CT chest in 3 months to assess for stability of the nodule.

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  Explanation

  This patient has a solitary pulmonary nodule. Overall, 35% of these lesions are malignant, usually primary lung cancers. In patients under 35 years of age without a smoking history, <1% of such lesions are malignant. Certain patterns of calcification within the nodule suggest a benign cause ("bulls-eye" pattern in granulomas, and "popcorn ball" in hamartomas), but these features alone cannot exclude malignancy. For low-risk patients such as this man, if the lesion remains stable on serial imaging studies (such as serial CT every 36 months) for 2 years, then no biopsy is deemed necessary to exclude malignancy.

• Question 556:

  A 25-year-old nulligravid female, whose LMP was 4 weeks ago, is seen by her OB/GYN for a left breast mass. The patient discovered it 2 weeks ago while in the shower. Her maternal aunt died of breast cancer at age 60, and the patient is very worried about this new finding. On examination, a mobile, nonerythematous, 3-cm nonsolid feeling mass is palpated in the left upper outer quadrant of her left breast. There is no nipple discharge, and the axillary lymph nodes are nonpalpable. Her right breast examination is normal. The patient wants you to schedule a mammogram that same day.

  Your response is which of the following?

  A. A surgical biopsy should be performed instead.
  B. A needle core biopsy can be done at the same time of her mammogram.
  C. Ultrasound would be a better imaging modality for her situation.
  D. In-office cyst aspiration is reassuring i the fluid is bloody.
  E. Antibiotics can treat her mastitis.
  C. Ultrasound would be a better imaging modality for her situation.

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  Explanation

  By history and physical examination, this patient most likely has a breast cyst. Given her age, mammography is not helpful due to the density of her breast tissue. Ultrasound is more helpful in detecting fluid-filled breast masses. In-office aspiration would be both diagnostic and therapeutic if the fluid was not bloody.

• Question 557:

  The patient is an 18-year-old male brought into the emergency room in the early morning by his friends after attending a dance party. He is agitated, pacing the hallway but unsteady. Despite this, he claims that he feels "wonderful" and states, "Everything will be all right." He also seems focused on seeing many colored flashes and hearing "all conversations at once." He has no known medical problems and is not taking any medication. He does admit to ingesting something early on, which he was told would help him "party all night." On physical examination, he has an elevated BP and pulse, dilated pupils, and significant diaphoresis.

  This same patient is eventually admitted for detox and successfully completes a drug treatment program. He is attending college and performing well. He returns to the urgent care clinic with complaints of reoccurring experiences similar to those he had when he was "high," such as flashing lights, intensified sounds, and halos. He is greatly upset about these and feels that they interfere with his studying. A complete physical examination and blood work (including toxicology screen) are negative.

  Administration of which of the following medications may worsen his symptoms?

  A. carbamazepine (Tegretol)
  B. clonazepam (Klonopin)
  C. fluoxetine (Prozac)
  D. haloperidol (Haldol)
  E. valproic acid (Depakene)
  D. haloperidol (Haldol)

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  Explanation

  This patient most likely ingested MDMA (3, 4-methylenedioxymethamphetamine, ecstasy) at a rave. Cocaine likely causes its effects through blockade of dopamine reuptake, which is responsible for its reinforcing and, therefore, highly addicting nature. PCP intoxicated individuals can often be agitated, but they typically will also display nystagmus and, not infrequently, violent behavior. PCP works through blockade of glutamate receptors. Hallucinogens are thought to increase the activity of the serotonin system, and they do not necessarily cause the feeling of euphoria seen in the above case. Amphetamine intoxication, by causing the release of dopamine, can appear similar to the above case, but florid perceptual disturbances are not as frequent. Ecstasy, classically taken at raves, acts as an amphetamine and a hallucinogen, thereby creating feelings of well-being or euphoria as well as causing hallucinations.

  Its dual nature is likely due to its neurophysiologic effects of releasing both dopamine and serotonin in the brain. This patient gives a history consistent with hallucinogen persisting perception disorder (flashbacks), characterized by the reexperiencing of perceptual disturbances after cessation of use. Although there is no medication which definitively treats the flashbacks, various drugs may be helpful. These include anticonvulsants, such as carbamazepine and valproic acid, or benzodiazepines such as clonazepam. Antidepressants such as fluoxetine would be indicated if the patient displayed a depressive disorder in addition. Antipsychotics such as haloperidol are to be avoided as they have been shown to actually worsen the symptoms of flashbacks.

• Question 558:

  A42-year-old man without prior significant medical history comes to your office for evaluation of chronic diarrhea of 12 months duration, although the patient states he has had loose stools for many years. During this time he has lost 25 lbs. The diarrhea is large volume, occasionally greasy, and nonbloody. In addition, the patient has mild abdominal pain for much of the day. He has been smoking a pack of cigarettes a day for 20 years and drinks approximately five beers per day. His physical examination reveals a thin male with temporal wasting and generalized muscle loss. He has glossitis and angular cheilosis. He has excoriations on his elbows and knees and scattered papulovesicular lesions in these regions as well Which of the following is the best test to confirm the suspected diagnosis?

  A. abdominal CT scan with contrast
  B. small bowel x-ray
  C. esophagogastroduodenoscopy with small bowel biopsy
  D. colonoscopy with colonic biopsy
  E. 72-hour fecal fat quantification
  C. esophagogastroduodenoscopy with small bowel biopsy

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  Explanation

  The patient has chronic diarrhea superimposed on a long history of loose stools, steatorrhea, and significant weight loss. While these features could be seen in several diseases, the presence of the pruritic vesiculopapular lesions on his extensor surfaces makes the diagnosis highly likely to be celiac sprue, with its frequently accompanying skin manifestation dermatitis herpetiformis. Crohn's disease is not usually associated with steatorrhea, and ulcerative colitis is often associated with bloody stools. Chronic pancreatitis and Whipple disease could cause a similar clinical picture but would not have the associated skin findings. A small bowel biopsy would confirm histopathologic features consistent with celiac sprue, such as villous atrophy and crypt hyperplasia. A small bowel biopsy could also diagnose or rule out Whipple disease by looking for the pathognomonic PAS (periodic acid-Schiff) positive organism Tropheryma whippelii. Colonic biopsies would be unhelpful in celiac sprue. A fecal fat quantification would likely confirm and assess the degree of steatorrhea, but would offer little other diagnostic information. A small bowel x-ray is too nonspecific to confirm the diagnosis and an abdominal CT scan would likely be normal unless the patient had developed a complication of advanced sprue, such as intestinal lymphoma. Patients with celiac sprue are at increased risk for malignancies of the small bowel with adenocarcinoma and lymphoma being the two most commonly encountered. Patients with celiac sprue are not at greatly increased risk of the other malignancies listed. Limited data suggest that strict adherence to a glutenfree diet may decrease the incidence of malignancy in these patients.

• Question 559:

  A45-year-old man undergoes a distal esophagectomy for Barrett's esophagus. During his hospital course, a left chest tube is placed for an effusion. Milky white fluid is found to come out through the tube.

  Which of the following statements is most accurate about this condition?

  A. Diagnosis can be confirmed by checking the lymphocyte count and triglyceride level in the fluid.
  B. This condition requires immediate surgical intervention to repair.
  C. The chest tube should be removed due to the possibility of an iatrogenic source of infection.
  D. Usually found on the right if due to a traumatic source.
  E. The use of TPN is contraindicated until the condition resolves.
  A. Diagnosis can be confirmed by checking the lymphocyte count and triglyceride level in the fluid.

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  Explanation

  Damage to the thoracic duct can be seen as a complication following distal esophagectomy or any procedure that involves dissection into the cervical region. It is most commonly seen on the left if iatrogenic. Aspiration of an odorless, milky fluid from the chest cavity is diagnostic, although increased lymphocyte counts nd triglyceride levels in the fluid help confirm the diagnosis. Normal chyle flow is around 2 L a day. Therefore, a chylous leak can result in nutritional depletion as well as decreased systemic lymphocytes to fight infection. The first therapy is placement of a chest tube to drain the chyle and to allow for approximation of the lung against the mediastinum. Stopping oral intake and starting total parental nutrition is usually tried for 710 days to see if there is spontaneous resolution of the leak. If conservative measures fail, ligation of the thoracic duct can be performed.

• Question 560:

  A 60-year-old male with a history of chronic schizophrenia and multiple hospitalizations checks into the emergency room with complaints of "funny movements." He has been compliant with risperidone (Risperdal) 3 mg bid, and he has been taking that dose for the last 6 years while living at a group home. He appears overweight but with adequate hygiene. His thoughts are somewhat tangential but not grossly disorganized. He denies any paranoia, ideas of reference, or delusions. He denies perceptual disturbances or suicidal/homicidal ideation. His physical examination is unremarkable except for occasional involuntary blinking and grimacing, as well as rotation of his left ankle. He is greatly distressed about these "habits" and wishes something to be done about them.

  The same patient is brought back to the emergency room via ambulance 1 month later due to "catatonia." According to his chart, he was maintained on his current dose of risperidone by his outpatient psychiatrist. On examination, he is unresponsive to questions. His vital signs demonstrate a temperature of 103.5, BP of 180/95, pulse of 105, and respirations of 20. His physical examination is notable for significant diaphoresis, muscular rigidity, and lack of cooperation with much of the examination.

  Which of the following would be the most appropriate management for this patient?

  A. add benztropine (Cogentin) to the risperidone
  B. continue the current dose of risperidone
  C. decrease the dose of risperidone
  D. discontinue the risperidone
  E. increase the dose of risperidone
  D. discontinue the risperidone

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  Explanation

  The patient has likely developed tardive dyskinesia (TD), a late-occurring movement disorder associated with chronic antipsychotic use. Adding an anticholinergic agent like benztropine would be indicated for treating an acute dystonia but is not effective for TD. Continuing the current dose of his antipsychotic will not lessen his movements, and increasing it will more than likely worsen them over time. Discontinuing his psychotropic will not reduce his dyskinesia, and it will provide a high risk for relapse of his psychosis. Once an individual has TD, reducing the dose (if clinically indicated) may minimize the progression or even improve the abnormal movements. The patient displays features consistent with neuroleptic malignant syndrome (NMS), a life-threatening condition associated with antipsychotic therapy. Adding benztropine will not treat NMS. Immediate discontinuation of the antipsychotic is recommended. Initiation of dantrolene, a muscle relaxant, as well as bromocriptine, a dopamine receptor agonist, may also be used to manage the patient.