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

USMLE USMLE-STEP-3 Online Questions & Answers

• Question 281:

  Which of the following is a contraindication to sentinel lymph node biopsy in breast cancer?

  A. clinically negative axillary examination
  B. multicentric disease
  C. lesion under the nipple
  D. history of previous breast biopsy
  E. patient preference for breast conservation
  B. multicentric disease

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  Explanation

  Sentinel lymph node biopsy offers an alternative to full axillary dissection as a diagnostic tool in breast cancer with clinically negative axillary lymph nodes. Patients are injected with technetium-labeled sulfur colloid and isosulfan blue dye. A gamma probe is used along with the visual cues of the blue dye to identify the "sentinel node." The theory is that if this node is negative for malignancy, the rest of the axilla will be negative as well. This spares these patients from an unnecessary axillary lymph node dissection and the morbidity that it entails. Patients with a positive sentinel lymph node require further therapy. Contraindications to the procedure include palpable axillary lymph nodes (because the diagnosis of axillary metastasis is apparent), multicentric disease, and a history of reaction to the blue dye (anaphylaxis and urticaria have been reported). If the lesion is very close to the axilla, there may be too much background radiotracer activity to discern the sentinel node. Lesions under the nipple are quite amenable to this procedure. There are several studies showing that the accuracy and success of this technique is related to surgeon experience. Surgeons are required to perform 2030 procedures with some supervision or confirmation of results before relying completely on sentinel node biopsy

• Question 282:

  A 45-year-old male comes to your office for his first annual checkup in the last 10 years. On first impression, he appears overweight but is otherwise healthy and has no specific complaints. He has a brother with diabetes and a sister with high blood pressure. Both of his parents are deceased and his father died of a stroke at age 73. He is a long-standing heavy smoker and only drinks alcohol on special occasions. On physical examination, his blood pressure is 166/90 in the left arm and 164/88 in the right arm. The rest of the examination is unremarkable. He is concerned about his health and does not want to end up on medication, like his siblings

  In the initial evaluation of a patient such as this, which of the following should be routinely recommended?

  A. a urine microalbumin/creatinine ratio
  B. an echocardiogram
  C. thyroid function tests
  D. renal function tests (serum creatinine and blood urea nitrogen [BUN])
  E. an exercise stress test
  D. renal function tests (serum creatinine and blood urea nitrogen [BUN])

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  Explanation

  Although this is the first time that your patient has been noted to have an elevated blood pressure reading, given his family history and obesity, it is important to consider the coexistence of other cardiovascular risk factors. His evaluation should include, among other things, screening for DM and dyslipidemia along with an ECG. It is reasonable to ask the patient to submit himself to a strict diet (low in fat and salt) and to increase his exercise and activity, since these lifestyle modifications will likely result in weight loss, decreased blood pressure, and improve his risk profile for cardiovascular disease. Nonetheless, it is rarely enough to normalize blood pressure in all but the earliest stages of hypertension. Provided that no other comorbidities exist, the patient should return to clinic in no more than 2 months for a repeat blood pressure check. There is no need to consider secondary causes of hypertension, given his age and presentation.

  You should not start antihypertensive medications until further evaluation is completed, and a second elevated reading confirms your diagnosis of hypertension. In the initial evaluation of hypertension (as per the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure [JNC-7], 2003), it is important to evaluate the patient for end-organ damage. This should include the heart, kidneys, eyes, and nervous system. It is recommended to obtain a urinalysis to assess for proteinuria, glucosuria, or hematuria; to obtain an ECG to evaluate the heart for potential hypertrophy or early signs of cardiovascular disease; to obtain a fasting lipid profile, particularly after the age of 35, to assess the cardiovascular risk profile; and to check the patient's renal function to assess for damage or dysfunction. Thyroid function tests are only indicated in the workup of secondary causes of hypertension. According to the JNC-7, this patient's blood pressure falls into the stage 2 hypertension classification in which either systolic blood pressure (SBP) is at least 160 mmHg or diastolic blood pressure (DBP) is at least 100 mmHg.

  Stage 1 hypertension is characterized by a SBP of 140159 mmHg and a DBP of 9099 mmHg. Prehypertension is characterized by a SBP of 120139 mmHg and a DBP of 8089 mmHg. Normal blood pressure is characterized by a SBP of less than 120 mmHg and a DBP of less than 80 mmHg. In classifying a patient's blood pressure and determining appropriate therapy, the higher of the two categories corresponding to the SBP and DBP is the one that is used. Per JNC-7 guidelines, treatment of stage 2 hypertension should involve the consideration of a two-drug regimen initially. The goal blood pressure in patients with diabetes is a SBP less than 130 mmHg and a DBP less than 80 mmHg. An ACE inhibitor should be used as the drug class has been shown to slow the progression of diabetic nephropathy and reduce albuminuria. Thiazide diuretics, betablockers, and calcium channel blockers are appropriate choices to consider in this patient in addition to an ACE inhibitor.

• Question 283:

  A 29-year-old woman presents to the primary care clinic complaining of frequent headaches for several months. During the interview she appears tearful and withdrawn, with minimal eye contact and reluctance to answer questions. With further encouragement and support, she is able to describe intense feelings of sadness, along with significant insomnia, poor concentration, fatigue, anhedonia, and little appetite with a 20-lb weight loss.

  Before she leaves the office, what is the most important question to ask her?

  A. "Have you been drinking alcohol or using illicit drugs recently?"
  B. "Have you been taking any over-thecounter medications?"
  C. "Have you been treated for any medical conditions?"
  D. "Have you ever felt like this before?"
  E. "Have you had thoughts of hurting yourself?"
  E. "Have you had thoughts of hurting yourself?"

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  Explanation

  This woman likely suffers from a major depressive episode. While asking about substance abuse, current medications, medical problems, and a past history of depression are very important in a complete psychiatric evaluation, assessment of suicidality is essential. The risk of suicide in patients with major depressive disorder is about 20 times higher than those without the illness. The estimated lifetime risk of suicide is approximately 15% in those individuals with major depressive disorder. The choice of a specific antidepressant may be influenced by many factors, including prior response in the patient or a family member and comorbid medical problems or substance abuse in the family (and, therefore, potentially the patient). If a patient or family member has a history of manic symptoms or bipolar disorder, consideration should be given to beginning a mood stabilizer prior to initiating antidepressant therapy, as antidepressants can cause a switch into mania in those individuals.

• Question 284:

  The patient is a 70-year-old man brought to the primary care clinic by his family over concerns that he has Alzheimer's disease. They have noticed a worsening of his memory over the past 6 months. He does not seem to want to get out of bed, and he appears to have difficulty providing for his basic needs such as cleaning, dressing, and cooking for himself. He is hesitant when talking, but it is unclear whether he is unable or unmotivated to speak. His family has also noticed that he appears depressed and is often seen crying. A MSE of the patient is performed to help determine whether he is suffering from a dementing illness or a depressive illness (pseudodementia).

  Which of the following characteristics on MSE is most consistent with pseudodementia?

  A. appears unconcerned during examination
  B. attends poorly to questions on MSE
  C. displays poor insight into symptoms
  D. gives "don't know" answers to questions
  E. consistently performs poorly to tasks
  D. gives "don't know" answers to questions

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  Explanation

  Older patients with cognitive decline due to depression, sometimes called pseudodementia, display characteristic findings on MSE. They usually are greatly concerned about their problems, even emphasizing their difficulties when compared with demented patients, who attempt to hide or minimize their deficits and appear unconcerned. Patients with pseudodementia are able to attend well to tasks despite their cognitive complaints. Individuals with dementias, however, have significant difficulty with attention and concentration. Patients with depression are more likely to demonstrate good insight into their presumed memory loss than those with dementia, who will commonly deny that there is anything wrong with them. On tests of cognition, those individuals with pseudodementia will show inconsistent results, performing better at some times and worse at others. Patients with dementia, however, will consistently perform poorly on various tests that address the same function. This patient displays characteristics of Lewy body disease, a dementia which may be related to Alzheimer's dementia. The classic triad of Lewy body dementia is a fluctuating course, peduncular hallucinations (visual hallucinations of small people, animals, or objects), and parkinsonian features. These patients tend to be very sensitive to extrapyramidal side effects and, therefore, antipsychotics such as risperidone should be avoided or sparingly used.

• Question 285:

  Ayoung college student is brought to your office by his fianc?for evaluation of weight loss. He tells you that, over the past few months, he seems to be unable to gain any weight despite having a ferocious appetite and that he is steadily losing weight. He has also noticed increased thirst and urination. Over the past few nights, he has awakened several times to go to the bathroom. You suspect that he may have developed diabetes.

  Which of the following is a diagnostic criterion for diabetes mellitus (DM)?

  A. a single fasting plasma glucose level of140 mg/dL in an asymptomatic person
  B. a plasma glucose level of >175 mg/dL measured at least 8 hours after a meal
  C. a plasma glucose level of >124 mg/dL measured at least 4 hours after a meal
  D. a blood glucose level of 200 mg/dL, 2 hours after completing a glucose tolerance test with a 75-g oral glucose load
  E. a serum glycosylated HgbA1C level higher than 7%
  D. a blood glucose level of 200 mg/dL, 2 hours after completing a glucose tolerance test with a 75-g oral glucose load

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  Explanation

  The symptoms of polydipsia, polyuria, and weight loss are suggestive of new-onset diabetes in this young man. Adiagnosis of DM can be made in any of the following ways: (1) A fasting plasma glucose level of at least 126 mg/dL; (2) a nonfasting plasma glucose level of at least 200 mg/dL in the presence of symptoms; or (3) an oral glucose tolerance test (OGTT) that yields a plasma glucose level of at least 200 mg/dL after 2 hours. Fasting is considered adequate at 8 hours. If unequivocal hyperglycemia is absent, testing should be repeated on a different day for confirmatory purposes before a diagnosis is made. Even though a glycosylated Hgb (A1C) of greater than 6% is suggestive of diabetes, the American Diabetes Association does not recommend the routine use of A1C in the diagnosis of diabetes.

• Question 286:

  A 26-year-old G2P1 female comes to your office for her initial obstetric visit. The first day of her last menstrual period was 6 weeks ago. Other than some mild morning sickness, she is feeling fine. Her first pregnancy was 40 weeks in gestation and uncomplicated. She has no significant medical history. The result of the test that you ordered is positive. What would be appropriate management for the neonate to reduce the risk of perinatal transmission of the hepatitis B virus?

  A. hepatitis B vaccine within 2 days of birth
  B. hepatitis B immune globulin within 2 days of birth
  C. hepatitis B immune globulin and hepatitisB vaccine within 12 hours of birth
  D. deliver the baby by scheduled caesarian section
  E. advise the mother not to breast feed
  C. hepatitis B immune globulin and hepatitisB vaccine within 12 hours of birth

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  Explanation

  At the initial prenatal visit, a complete history and physical examination is performed along with a panel of laboratory studies. Routinely, a complete blood count, blood type, and Rh group with antibody screen, rubella antibody, rapid plasma reagin (RPR), HIV, pap smear, cervical swab for gonorrhea and chlamydia, urinalysis, and urine culture are performed. Pregnancy is one of the few conditions in which treatment of asymptomatic bacteruria would be recommended. Neither a basic metabolic panel nor a TSH measurement would be indicated unless the patient had an underlying medical condition that warranted further evaluation. Screening for gestational diabetes with a glucose measurement after ingestion of 50 g of glucose is performed in many pregnancies, but not until 2428 weeks' gestation. Routine screening for vaginal or rectal colonization with group B Streptococcus is also performed, but not until 34 weeks of gestation or later. It is recommended that all pregnant women be screened for hepatitis B at their initial prenatal visit by obtaining a hepatitis B surface antigen. This helps to determine if the woman has hepatitis B that could put her baby at risk for the infection. Hepatitis B surface antibody may be a sign of previous infection or of previous vaccination with the hepatitis B vaccine. The presence of core antibody and e antibody may be signs of previous infection.

  Testing for the e antigen is not useful for initial screening purposes but may be warranted if the patient were found to have chronic hepatitis B infection.

  If the mother tests positive for hepatitis B surface antigen during her pregnancy then the neonate should receive both hepatitis B immune globulin and the initial dose of the hepatitis B vaccine series. This combination has been shown to reduce risk of perinatal transmission from approximately 10% if the woman is surface antigen positive to less than 3%. There are currently no data to show that delivering a baby by caesarian section will reduce the risk of perinatal transmission of the infection. Breastfeeding has not been shown to increase the rate of transmission of infection to a nursing infant.

• Question 287:

  A 4-week-old, previously healthy male presents with projectile emesis after feeds. His mother states that he has had 2 weeks of postprandial emesis, which became projectile in the past 2 days. She states that it looks like formula and has never been bilious.

  Which of the following statements is true?

  A. Physical examination is almost always normal in patients with this condition.
  B. Upper gastrointestinal (GI) contrast study is the best diagnostic option.
  C. This patient should be taken emergently to the operating room (OR) once the diagnosis is made.
  D. If uncorrected, these infants will progress to complete obstruction.
  E. Surgical therapy involves bypassing the site of obstruction.
  D. If uncorrected, these infants will progress to complete obstruction.

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  Explanation

  Pyloric stenosis usually presents in the first 48 weeks of life. Parents usually report nonbilious emesis after feeding, which progresses to a projectile nature. Untreated, this will become a complete obstruction. On examination, an "olive sign" or mass in the right upper quadrant is often found. Ultrasound is the best radiologic test. These infants may present with dehydration and metabolic abnormalities from the emesis. The most common abnormality is hypokalemic, hypochloremic metabolic alkalosis. While surgical correction is urgent, it is not emergent. These infants should be resuscitated with IV fluids and their metabolic derangements corrected before an operation. The surgical treatment is a pyloromyotomy, which involves splitting the hypertrophic muscles of the pylorus while keeping the mucosa intact. This can be performed either open or laparoscopically. Patients are usually allowedto feed within hours of their operation.

• Question 288:

  A 53-year-old Black male, with a history of hypertension, hepatitis C, and newly diagnosed nonsmall cell lung cancer, undergoes his first round of chemotherapy, which includes cisplatin. You are called to see this patient 5 days into his hospitalization for oliguria and laboratory abnormalities. Other than the chemotherapy, he is receiving lansoprazole, acetaminophen, and an infusion of D5-- 0.9% normal saline at 50 mL/h. On examination, his BP is 98/60 and heart rate is irregular, between 40 and 50 bpm. His physical examination shows a middle-aged male in no acute distress. His cardiac examination is unremarkable, his lungs show bibasilar crackles, and the abdominal examination is positive for a palpable spleen tip without any hepatomegaly or abdominal tenderness. He has trace bilateral ankle edema. His distal pulses are irregular. The neurologic examination was unremarkable. His laboratory (serum sample) results are as follows

  

  Which electrolyte/acid-base abnormality is most likely responsible for the findings on physical examination?

  A. hypernatremia
  B. hyperkalemia
  C. metabolic acidosis
  D. hyperphosphatemia
  E. hyperuricemia
  B. hyperkalemia

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  Explanation

  The patient has tumor lysis syndrome. The destruction of malignant cells by chemotherapeutic agents will lead to the release of intracellular contents, including potassium, phosphorus, and uric acid (from nucleic acids). This can result in hyperkalemia, hyperuricemia, and hyperphosphatemia. Hyperkalemia will produce significant ECG abnormalities, including peaked T waves and widened QRS complexes. The presence of bradycardia and irregular heart rate on physical examination are suggestive of the cardiac effects of hyperkalemia, which can lead to lifethreatening arrhythmias if not addressed. Patients with tumor lysis syndrome can develop a severe hyperuricemia. The kidneys are responsible for the excretion of uric acid. In acidic urine, the uric acid can crystallize in collecting tubules, resulting in intratubular obstruction and acute kidney failure. Calcium oxalate stones are not a part of this entity. Cisplatin can cause renal potassium and magnesium losses, which is not the case in this patient. The laboratory data suggest the release of intracellular contents (high LDH, uric acid, potassium, and phosphate) and the diagnosis of urate nephropathy as the cause of his acute kidney failure. As mentioned before, hyperkalemia will produce significant ECG abnormalities, including peaked T waves and widened QRS complexes. Prominent U waves are found in hypokalemia, not hyperkalemia. Atrial fibrillation is not typically seen in hyperkalemia.

• Question 289:

  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. The patient's family history is strongly suggestive of which of the following?

  A. familial adenomatous polyposis (FAP) syndrome
  B. hereditary nonpolyposis colorectal cancer (HNPCC) syndrome
  C. Peutz-Jeghers syndrome
  D. Cronkhite-Canada syndrome
  E. Turcot syndrome
  B. hereditary nonpolyposis colorectal cancer (HNPCC) syndrome

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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 290:

  A husband and wife, both aged 30, come to the community health center for advice and evaluation prior to a month-long mission trip to central Africa. Both are in good health. She takes oral contraceptive pills and he is on no prescription medication. Review of their records shows that they have had all of the appropriate vaccinations for their ages, have completed a three dose hepatitis B series and had dT boosters 2 years ago. Their mission will involve building a school and health clinic in a rural area of Cameroon.

  How would you advise them regarding food safety?

  A. Carbonated soft drinks served with ice cubes are considered safe to drink.
  B. Locally grown oranges and bananas are safe to eat.
  C. Water is safe to drink after filtering through an absolute 1 m filter.
  D. Brushing teeth with untreated water is safe as long as it is not swallowed.
  E. Salads are generally safer to eat than cooked meats.
  B. Locally grown oranges and bananas are safe to eat.

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  Explanation

  Encounters with persons traveling to other countries are common in primary care or community health settings. The advice and interventions provided are dependent on where the person is going, what he or she will be doing, and for how long he or she will be there. The most accessible and up-to-date source of this information in the United States is at the Centers for Disease Control web site, which provides detailed recommendations on vaccinations, health, and safety risks involved in overseas travel. In this series of questions, the travelers are going to the region of central Africa and, more specifically, to a rural area of Cameroon. This is an area of the world where polio remains a risk. As most Americans have not been vaccinated against polio since childhood, booster immunization against polio is recommended. The injectable polio vaccine is recommended as it does not carry with it the risk of vaccine-induced disease that the oral (live virus) vaccine does. Smallpox has been eliminated as a naturally occurring disease, although it remains of importance in bioterrorism discussions. The smallpox vaccine is not necessary for travel to any part of the world, but is used by the military or medical first responders who may be exposed in the event of a biowarfare attack. The traveling couple is up-to-date on their dT status with boosters within the past 2 years. They have completed a series of both MMR and hepatitis B, which is felt to confer lifetime immunity. Malaria prevention is an important consideration for travel to many areas of the developing world. Different regimens may be used depending on the area to which the travel will occur. All regimens, however, require the institution of prophylaxis prior to travel and the continuation of prophylaxis for up to 4 weeks after completion of travel. This is due to the life cycle of organisms that cause the disease. Prevention of malaria also involves attempts to reduce one's risk of exposure to the Ixodes mosquito which can transmit the disease. This mosquito tends to be more active early in the morning and at dusk, and less active in the middle of the day. Wearing long sleeved clothing, using mosquito nets, and insect repellent is important. DEET-containing insect repellents are recommended as the most effective products available and are safe when used appropriately. The most common cause of injury during travel is motor vehicle accidents. The risk of injury is higher in many developing countries than in the United States due to poor roads, poor vehicle maintenance, lack of seat belts, and other issues. Very cautious driving and avoidance of driving after dark may help to reduce the risk somewhat. While swimming is an ideal exercise in such hot climates as central Africa, freshwater lake swimming should be avoided due to the risk of exposure to schistosomiasis. The Schistosoma species that cause this disease are endemic in standing freshwater bodies. Swimming or bathing in salt water or chlorinated swimming pools is safer. Traveler's diarrhea and exposure to foodborne pathogens is a common cause of illness during travel to developing countries. The guideline with food is to cook it, peel it, purify it, or forget it. Fruits that can be peeled, such as oranges or bananas, are generally safe to eat. Carbonated beverages are also safe. However, ice cubes made from local water supplies are a common, and sometimes ignored, source of infection. Water purification can be accomplished by boiling or by filtering through an absolute 1 m filter and then purifying with iodine.

  Filtering alone does not provide adequate protection. Salads that are not made of carefully cleaned vegetables should be avoided and salad dressings may also be contaminated. Meats that are well cooked and served hot would be considered less likely to transmit an infection. Finally, brushing one's teeth with unpurified water carries a significant risk of transmission of waterborne illness and should be avoided. Purified water or bottled water should be used instead.