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

USMLE USMLE-STEP-3 Online Questions & Answers

• Question 211:

  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. Which of the following is the best initial treatment for this patient?

  A. colectomy
  B. oral prednisone
  C. oral metronidazole
  D. cortisone enemas
  E. intravenous cyclosporine
  B. oral prednisone

  ---

  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 212:

  Which of the following structures can be found outside of the spermatic cord during a hernia repair?

  A. direct hernia sac
  B. indirect hernia sac
  C. vas deferens
  D. testicular artery
  E. ovary
  A. direct hernia sac

  ---

  Explanation

  A direct hernia comes through the medial inguinal canal floor and is found behind the spermatic cord. An indirect hernia passes though the internal inguinal ring, and thus can be found within the spermatic cord. The spermatic cord also contains the vas deferens, the testicular artery, lymphatics, and nerve fibers.

• Question 213:

  A 72-year-old man comes to your clinic for the first time, accompanied by his wife. His wife states that she is concerned because he has been growing increasingly forgetful over the past year. Within the past month, he has forgotten to turn off the stove and has got lost while walking to the post office one block away from their home. His past medical history is significant for well-controlled diabetes and chronic lower back pain. He has no history of falls or traumatic injury to the head. Examination of the patient is significant for a score of 18 on a Mini Mental Status Examination (MMSE). During the administration of the MMSE, the patient blurts out that his wife brought him to the doctor because she is having an extramarital relationship.

  Which of the following accurately describes this patient's condition?

  A. There is no genetic basis for development of this disease.
  B. It is usually abrupt in onset.
  C. There is no correlation between age and prevalence of this disease.
  D. Environmental exposure is a proven risk factor for development of this disease.
  E. It is one of the most common terminal illnesses in developed nations.
  E. It is one of the most common terminal illnesses in developed nations.

  ---

  Explanation

  This patient's symptoms are most consistent with Alzheimer disease. Alzheimer disease is a prominent condition in developed nations, ranking as the third most common terminal illness behind heart disease and cancer. It is the most common form of dementia, with over 4 million Americans having the condition in the United States alone. There is a direct correlation between advanced age and increasing prevalence of Alzheimer disease. While there is an early-onset form of familial Alzheimer disease that may appear as early as the third decade of life, this accounts for only a small percentage of total Alzheimer cases. There does appear to be a genetic component to the development of Alzheimer disease, as it has been demonstrated that first-degree relatives of Alzheimer patients possess an increased risk for development of the condition. Genes on chromosomes 1, 14, and 21 have been implicated in this association. While age and family history are important risk factors, there is no evidence proving that environmental factors lead to an increased chance for development of the disease. Progression of Alzheimer dementia is typically insidious, spanning as many as several years. Anticholinergic agents and any other medication with anticholinergic effects are contraindicated in the setting of Alzheimer dementia. Their use may lead to worsening of cognition and may contribute to decreased efficacy of medications used in the treatment of Alzheimer dementia. Tricyclic antidepressants such as amitriptyline should be avoided for this reason. Risperidone, olanzapine, and quetiapine are atypical antipsychotic medications which are useful in the treatment of emotional withdrawal and delusions which may arise in Alzheimer patients. Trazodone, carbamazepine, and divalproex are moodstabilizing medications which are useful in patients who display marked agitation. While trazodone does display some anticholinergic side effects, they are far less pronounced than those seen with amitriptyline.

• Question 214:

  A 6-month-old male infant presents to your clinic because the mother is concerned that he is not eating well and he has been constipated. The mother tells you that her prenatal course and delivery were uneventful. On physical examination, the infant has a puffy face, large tongue, and persistent nasal drainage The above condition can be caused by a deficiency of which of the following?

  A. iron
  B. vitamin C
  C. vitamin D
  D. iodine
  E. cortisol
  D. iodine

  ---

  Explanation

  Hypothyroidism results from inadequate thyroid hormone production or a defect in thyroid hormone receptor activity. Hypothyroidism can be congenital or acquired. Most infants with congenital hypothyroidism are asymptomatic at birth. Feeding difficulties, choking spells, and somnolence often present during the first month of life. Respiratory distress can also occur in part due to the large tongue and nasal obstruction. On physical examination, you may find a large abdomen, umbilical hernias, subnormal temperature, cold skin, murmurs, or bradycardia. Iodine is absorbed in the GI tract as iodide. Iodide is concentrated in the thyroid gland and four atoms are incorporated into each molecule of thyroxine. Profound dietary deficiency of iodine will result in hypothyroidism and is the most common cause of goiter in the world. Rickets results from a deficiency of vitamin D.

  This condition predominately affects the long bones and skull. Vitamin C deficiency results in scurvy, a condition with impaired collagen formation. The clinical manifestations may include changes in the gums, loosening of teeth, brittle bones, and swollen joints. Pallor is the most important sign of iron- deficiency anemia. Children may also have the desire to ingest unusual substances such as ice or dirt. Finally, hyponatremia and hypoglycemia are the prominent presenting signs of adrenal insufficiency in infants

• Question 215:

  A 72-year-old previously healthy woman was diagnosed with Stage II breast cancer and was initiated on FAC chemotherapy (5-fluorouracil, doxorubicin, cyclophosphamide) 3 months ago. She now presents to the emergency room complaining of exertional dyspnea, orthopnea, and lower extremity edema. Her vital signs are normal, her EKG is normal, and her chest x-ray shows cardiomegaly and pulmonary vascular congestion.

  What is the most likely cause of the patient's new symptoms?

  A. malignant pericardial effusion with cardiac tamponade
  B. acute pericarditis due to viral infection
  C. anthracycline-induced cardiomyopathy
  D. valvular aortic stenosis
  E. acute myocardial infarction
  C. anthracycline-induced cardiomyopathy

  ---

  Explanation

  This patient has clinical signs of congestive heart failure. Cardiomyopathy may be a complication of chemotherapy containing anthracyclines (doxorubicin, daunorubicin, idarubicin, epirubicin). The cumulative anthracycline dose is the most widely recognized risk factor for this problem, although it is more common in patients over 70, patients with any other history of heart disease, or those with a history of thoracic radiation treatment. Other reversible causes of heart failure such as ischemic cardiomyopathy should be investigated. Patients with anthracycline cardiomyopathy frequently have recovery of systolic function with standard medical heart failure therapy. Lack of chest pain and a normal EKG make acute pericarditis or acute myocardial infarction unlikely. Pericardial effusion with tamponade might cause dyspnea and edema, but not pulmonary vascular congestion or pulmonary edema.

• Question 216:

  A 19-year-old woman begins chemotherapy for an acute leukemia. Although you determine that her renal function is unimpaired prior to the initiation of treatment, you feel that she may be at high risk for development of tumor lysis syndrome given her condition's typically good response to chemotherapy.

  Which of the following is an appropriate medication to use as a preventative measure prior to and during her treatment for leukemia?

  A. indomethacin
  B. colchicine
  C. allopurinol
  D. probenecid
  E. sulfinpyrazone
  C. allopurinol

  ---

  Explanation

  Tumor lysis syndrome refers to a series of metabolic disturbances resultant from cancer treatment. It generally occurs when a large number of cancer cells are killed rapidly, releasing the contents of those cells into the systemic circulation. These contents include various ions. Tumor lysis syndrome is typically characterized by a combination of hyperuricemia, hyperkalemia, hyperphosphatemia, hypocalcemia, and lactic acidosis. Besides treatment of electrolyte abnormalities, urine alkalinization and aggressive hydration are frequently included as a part of treatment. Patients with tumor lysis syndrome may also develop oliguric acute renal failure, which arises from the precipitation of uric acid, hypoxanthine, or calcium phosphate within the renal tubules. Acute tubular necrosis is generally not seen in the setting of tumor lysis syndrome. Allopurinol reduces the synthesis of uric acid by blocking the metabolism of xanthine and hypoxanthine to uric acid via xanthine oxidase inhibition. This makes it useful in reducing the risk of hyperuricemia from tumor lysis. Urinary alkalinization and aggressive hydration are also components of treatment. Probenecid and sulfinpyrazone enhance urate excretion by blocking the reabsorption of urate from the proximal tubule. Colchicine is effective in treating acute gout attacks by inhibiting leukocyte migration and phagocytosis. Indomethacin, and other NSAIDs, can be effective in treating acute gout attacks by inhibiting urate crystal phagocytosis. However, low-dose aspirin may actually increase the risk of gout.

• Question 217:

  Parents bring you a 9-month-old boy they recently have adopted from western Russia. They have sparse medical records of the child's past. They do know that the boy was the result of a sexual assault on the mother and was given up at birth. The child has been in a "baby home" for 5 months. The records which accompanied the boy indicate that there had been some testing done. These tests include HIV, hepatitis B and C serologies, and a rapid plasma reagin (RPR), all of which are negative at 8 months of age. There is what appears to be a Russian immunization record as well. It seems to indicate that the child has had three diphtheria, tetanus, pertussis (DTP), three oral polio, and three hepatitis B vaccinations. There is also an indication that BCG (Bacille Calmette-Guin) was given.

  You place a purified protein derivative (PPD) and the parents come back in 48 hours to have it read. The response is 15 mm of induration. The boy does not have any respiratory symptoms at this time.

  What is the most appropriate response to this information?

  A. Collect three morning sputum and send for acid-fast stain and TB culture.
  B. Give a repeat BCG vaccine.
  C. Do nothing as the PPD is considered negative given the prior BCG vaccination.
  D. Perform a CXR and begin isoniazid (INH) for 9 months if the x-ray is negative.
  E. Perform a CXR and begin "triples" (INH, rifampin, pyrazinamide) even if the x-ray is negative.
  D. Perform a CXR and begin isoniazid (INH) for 9 months if the x-ray is negative.

  ---

  Explanation

  Repeating all serologies is important. The prior negative testing should be included in the medical record, but should not dissuade one from confirming the result. The collection of stool for ova and parasites (O + P) is an important evaluation but should not be the only testing performed. ACBC is not an adequate screen for infections.

  The diagnosis of FAS includes findings of characteristic facies, growth retardation, and CNS impairment. The characteristic facies of FAS includes flat philtrum, thin upper vermilion border, short palpebral fissures, micrognathia, microphthalmos, and microcephaly.

  BCG is a common vaccine administered in countries outside of the United States. The presence of a positive reaction to a PPD in a child who has had a prior BCG is still concerning. The presence of a 15- mm reaction is considered positive and warrants a CXR and initiation of anti TB treatment. The negative CXR would indicate TB exposure, and INH alone is recommended. Sputum collection is usually unwarranted in asymptomatic children.

• Question 218:

  A 26-year-old HIV-positive man is admitted to the hospital for treatment of a varicella-zoster infection. On the fourth day of treatment, he develops an acute renal insufficiency. What is the most likely treatment- related mechanism accounting for the patient's acute renal insufficiency?

  A. the formation of toxic metabolites
  B. decreased glomerular filtration rate
  C. the precipitation of acyclovir in renal tubules
  D. direct tubular cytotoxic injury
  E. hypersensitivity interstitial nephritis
  C. the precipitation of acyclovir in renal tubules

  ---

  Explanation

  HIV-positive patients who develop a varicella-zoster infection require aggressive antibiotic therapy. Intravenous acyclovir should be adminstered for a period of 7 days, and oral maintenance therapy should be started for secondary prophylaxis. While acyclovir is usually well tolerated, it can be nephrotoxic when given intravenously. It may crystallize within renal tubules and cause subsequent acute tubular necrosis. Acyclovir is more likely to cause nephrotoxic effects if there is associated dehydration or a preexisting renal insufficiency. Individuals who have a preexisting renal insufficiency should have the dose and frequency of acyclovir administration adjusted according to their baseline creatinine clearance.

• Question 219:

  What is the most sensitive indicator of pneumonia in a child?

  A. tachycardia
  B. tachypnea
  C. hypotonia
  D. vomiting
  E. coughing
  B. tachypnea

  ---

  Explanation

  Tachypnea is the most sensitive clinical parameter for diagnosing a lower respiratory tract infection. The child may have tachycardia from a fever or anxiety but, typically, not simply from pneumonia. Coughing is common in children with pneumonia but it is not specific for lower respiratory tract infections, as it can also be seen in upper and lower respiratory tract infections

• Question 220:

  Afather and son come to your office because of persistent diarrhea. They relate the presence of watery diarrhea for over 2 weeks. They noted that the diarrhea began after returning from a Boy Scout camping trip in the Rocky Mountains. The diarrhea has waxed and waned for 2 weeks. It is nonbloody and foul smelling. They have had increased flatulence and mild abdominal cramping.

  What would be the most appropriate treatment?

  A. oral ciprofloxacin
  B. oral metronidazole
  C. bismuth subsalicylate (Pepto-Bismol)
  D. an antidiarrheal agent only; no antimicrobials necessary
  E. oral rehydration only
  B. oral metronidazole

  ---

  Explanation

  G. lamblia is a common protozoan which can be acquired by ingesting unfiltered water. It is seen frequently in people who drink fresh stream water. It is a cause of chronic, nonbloody diarrhea. There is typically a large amount of gas and cramping associated with Giardia infections. RMSF does not typically cause a gastroenteritis. Children with RMSF will commonly have fevers, headaches, and a petechial rash. Rotavirus and Norwalk viruses typically cause acute, self-limited gastroenteritis. The diarrhea is

  nonbloody, nonmucousy, and typically lasts a few days. The most appropriate treatment for giardiasis is oral metronidazole. Oral rehydration is an important mainstay in the treatment of diarrhea of any cause but is not a specific treatment for giardiasis. Ciprofloxacin is commonly used for traveler's diarrhea caused by E.

  coli.