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

USMLE USMLE-STEP-3 Online Questions & Answers

• Question 751:

  A 35-year-old woman with a history of major depressive disorder is brought into the ED by her boyfriend. He believes she may have overdosed on pain medication in an effort to hurt herself. He gives you three medication bottles which he discovered empty and states that they were nearly full before leaving for work earlier that morning. However, the timing of the ingestion is unclear. All three of the bottles apparently held acetaminophen- containing medications. Examination of the patient reveals a tired- appearing woman complaining of nausea and right upper quadrant abdominal pain. Which of the following pharmacologic treatments is most appropriate at this time?

  A. no pharmacologic treatment is necessary
  B. naloxone
  C. flumazenil
  D. physostigmine
  E. N-acetylcysteine
  E. N-acetylcysteine

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  Explanation

  When acetaminophen is taken in normal doses, it is conjugated in the liver to harmless glucuronide and sulfate metabolites. These metabolic pathways become easily overwhelmed in the setting of a large overdose, however. If this occurs, the cytochrome P450 system directs conversion of the excess acetaminophen to a compound called NAPQI, which is conjugated with glutathione to form a nontoxic mercapturate metabolite. Once glutathione stores are exhausted in the liver, however, the excess NAPQI combines with proteins within hepatic cells causing hepatic cell death. Taurine is a mercaptan- containing amino acid involved in bile acid biochemistry. Citrulline aids in the detoxification and elimination of ammonia. Ornithine plays an important role in the urea cycle.

  N-acetylcysteine should be administered as promptly as possible for treatment of acetaminophen overdose. It works by helping restore hepatic glutathione stores and by providing sulfhydryl groups that bind toxic metabolites. N-acetylcysteine is administered orally in the form of an initial loading dose (140 mg/kg) followed by 17 doses (70 mg/kg each) given every 4 hours. In addition to this oral therapy, the Food and Drug Administration (FDA) approved 21-hour and 48-hour long intravenous treatment regimens in 2004. Left untreated, acetaminophen overdose carries a significant risk for hepatic failure and subsequent death depending on the amount of acetaminophen ingested, the presence of any preexisting liver disease, and interactions with any other medications that induce cytochrome P450 enzyme activity. Naloxone, flumazenil, and physostigmine are given as antidotes for toxicity related to opioid analgesics, benzodiazepines, and muscarinic receptor blockers, respectively.

  Poor prognosis is associated with elevated serum lactate levels (above 3.5 mmol/L), acidemia (arterial pH less than 7.3), renal failure, and coagulopathy. The Rumack-Matthew nomogram provides a means of determining whether an individual falls into the possible-, probable-, or high-risk categories for developing hepatotoxicity based on serum acetaminophen levels and the number of hours since ingestion. Therapy with N-acetylcysteine is most effective if begun within 8 hours of the toxic ingestion but still has proven benefit if started within 24 hours

• Question 752:

  A 23-year-old pregnant woman with type 1 diabetes was admitted to the Obstetrics service for DKA. The DKA was appropriately treated and has resolved. You were consulted for medical management of the diabetes, as her sugars have been labile throughout the hospital stay. Your history and review of records reveals that the patient has a long-standing history of noncompliance with diet and medication regimens. She currently uses any insulin she can get and does not eat regular meals. She has fluctuating blood sugars with episodes of hypoglycemia.

  You counsel the patient extensively, order nutrition and diabetic teaching consults, and discuss keeping home glucose logs. Assuming the patient will follow your advice, which regimen would you recommend to minimize fluctuating glucose readings?

  A. NPH insulin twice daily
  B. insulin glargine once daily and insulin lispro before meals
  C. Humulin 70/30 twice daily
  D. NPH twice daily and regular insulin three times daily with meals
  E. insulin glargine twice daily
  B. insulin glargine once daily and insulin lispro before meals

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  Explanation

  See Table below for onset, peak, and duration of the various types of insulin.

  

  Multiple randomized-controlled trials have shown that tight blood sugar control type I diabetics will reduce the risk of micro- and macrovascular complications, such as retinopathy, neuropathy, and cardiovascular disease.

  The Diabetes Control and Complications Trial (DCCT) showed that, compared with conventional therapy, intensive therapy significantly reduced the risk of retinopathy progression and clinical neuropathy. Other studies have shown that intensive therapy prevented one cardiovascular event for every 25 patients treated over a 10-year period in a relatively young group of patients. Intensive therapy is not without risk, however. The risk of severe hypoglycemia and subsequent coma or seizure was significantly higher in the intensive therapy group. Control of type I diabetes is dependent on controlling diet with regular low fat meals, keeping blood sugar logs (fasting/ preprandial and postprandial) and adherence to insulin. In type I diabetes, oral hypoglycemics are not useful, as patients have a lack of endogenous insulin production. Most oral hypoglycemic agents work either as insulin sensitizers, secretagogues, or a combination. Type I diabetics need insulin for glycemic control and for prevention of ketoacidosis.

  Patient acceptance and compliance is critical, for which education is key. Patients must be taught the implications of poor control, and the means to optimize control. Blood sugar testing techniques and nutrition counseling are essential features of success. Regular cardiovascular exercise is also of paramount importance. For patients with poor diet regimens, medication compliance, and blood sugar testing, a longacting agent without peaks and valleys of insulin levels would be an ideal agent for basal insulin.

  For patients who have no regular mealtimes and history of hypoglycemia, rapidacting insulin is taken at the time of meals is recommended. Patients should also be taught to count carbohydrates and adjust the insulin accordingly (1 g carbohydrate = 1 unit of lispro). Another option is to use a sliding scale for the lispro based on the premeal sugar levels (using 1 unit for every 3050 mg/dL that the blood sugar is above target). Thus, based on these recommendations, the best option for this patient would be to use insulin glargine as the basal insulin and insulin lispro at the time of meals. However, regular follow-up and compliance with lifestyle measures are key to achieve optimal short- and long-term control and reduction of complications.

• Question 753:

  As an intern on a medical consultation service, you are providing a cardiology consultation for a patient who developed a myocardial infarction while undergoing an elective cholecystectomy. Although not described in the medical record, the cardiology consultant attending stated the patient experienced the myocardial infarction because of prolonged general anesthesia. The surgical attending did not make the initial incision until the patient had been sedated for more than 1 hour. As you review the medical record, you realize the patient is the father of your college roommate. When you walk in the room, the family is very happy to see you and asks, "What happened? What went wrong?" What is your ethical responsibility?

  A. disclosure of your knowledge of the clinical circumstances to the patient
  B. disclosure of your knowledge of the clinical circumstances to your college roommate
  C. disclosure of the family's questions to the attending physician
  D. documentation in the medical record of your assessment of the iatrogenic patient injury
  E. request a random drug test of the surgeon
  C. disclosure of the family's questions to the attending physician

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  Explanation

  Disclosure of unanticipated outcomes is one of the most challenging communications that can occur in the physician-patient relationship. Determining which events require disclosure and the appropriate mechanism to provide this information is part of the professional behavior inherent in our roles as physicians. Concepts for effective disclosure include:

  Many institutions have already developed policies and mechanisms to provide this communication. The attending physician is the most appropriate person to lead this process. Your knowledge of the clinical circumstances is hearsay. It is not appropriate for you to provide unsubstantiated information to the patient or to the friend. Appropriate documentation in the medical record provides the facts surrounding the primary event. It is inappropriate to document opinions, accusations, or arguments. Medical errors are responsible for more than 98,000 excessive patient deaths per year. In order for medical errors to be reduced, there need to be mechanisms for accountability which occur within a supportive environment. Peer review, morbidity and mortality rounds, shorter work weeks, and root cause analysis are all mechanisms to prevent future errors from fatigue, impaired system processes, and inadequate knowledge. Frequently when medical errors occur, the families want to know what is being done to prevent this from happening again. Although the peer review process is confidential and not subject to subpoena, it provides an effective mechanism to honestly evaluate our colleagues and enforce necessary discipline to improve patient safety. Random drug testing is not a systemic solution.

• Question 754:

  An 18-year-old male is brought to the ED after sustaining a stab wound to the left chest that is medial and superior to the nipple. He was unresponsive at the scene and intubated by the emergency medical technician (EMT) team. His pulse is 140 and BP is 60/30 after receiving 1 L of lactated Ringers solution and 2 units of blood during his transport. On auscultation there are no breath sounds on the left. His trachea is midline. He has no evidence of neck vein distention.

  Which of the following statements is true?

  A. Cardiac tamponade is unlikely since there is no evidence of neck vein distention.
  B. A left chest tube should be placed immediately.
  C. Given the probability of a cardiac injury, an emergent thoracotomy should be performed in the ED.
  D. An aortic angiogram should be ordered immediately to assess for aortic injury.
  E. No intervention should be performed until a chest x-ray is completed to provide more information.
  B. A left chest tube should be placed immediately.

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  Explanation

  One of every four trauma deaths in North America is due to thoracic trauma. Many deaths from thoracic trauma can be prevented with prompt diagnosis and treatment of injuries. The first step in the evaluation of any trauma patient is the primary survey, or ABCDE (airway, breathing, circulation, disability, exposure). First you would evaluate the airway. In this case, an endotracheal tube was placed at the scene. It would be important to evaluate this airway's adequacy of placement using a capnometer to assess end-tidal CO2 and auscultation of the breath sounds. Next you would assess breathing. Auscultation in this patient reveals an absence of breath sounds on the left. This must be resolved before moving on to circulation. This could be the result of placing the endotracheal tube in too far into the right mainstem, which is easily checked by withdrawing the endotracheal tube 2 cm.

  The other possibilities are life-threatening emergencies, including a tension pneumothorax or a hemothorax. Given the fact that the patient is unstable and there is a history of penetrating chest trauma, a chest tube should be placed immediately without the delay of a chest x-ray. A tube thoracostomy in this patient will be diagnostic and also therapeutic. Ahypovolemic patient with cardiac tamponade may not have neck vein distension. ED thoracotomies should only be performed in a pulseless patient. All other patients requiring thoracotomy should go to the OR. This patient is unstable and as such should not be taken to angiogram.

• Question 755:

  A 34-year-old male presents with a penile lesion. Your history, physical examination, and serology confirm a diagnosis of syphilis. The patient reports that his mother told him he was "allergic" to penicillin. He does not recall any personal history of anaphylaxis or rash to antibiotics however he has never been "sick." How would you manage this patient?

  A. Admit to the ICU for penicillin desensitization as you don't want to risk anaphylaxis especially with the uncertain history.
  B. Do skin testing for penicillin allergy.
  C. Avoid penicillin or cephalosporins in future.
  D. Treat with erythromycin.
  E. Treat with penicillin as he is not likely to have a true allergy.
  B. Do skin testing for penicillin allergy.

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  Explanation

  A questionable history of penicillin allergy by a patient often incorrectly labels patients as penicillin allergic. Physicians are often afraid of a true anaphylactic reaction and turn to a second-line medication. Most patients who state they were penicillin allergic or were told by a parent they were allergic were confusing a complication of the illness, such as a rash from viral prodrome. In fact, 80 90% of patients who self-report a nonanaphylactic reaction or were informed by a parent of a penicillin allergy are not penicillin allergic when assessed with skin allergy testing. The frequency of all adverse reactions to penicillin in the general population ranges from 0.7 to 10%. Approximately 98% of patients with a reported history of penicillin allergy (except anaphylaxis) and a negative skin test can safely receive penicillin. In patients who have an unclear history of penicillin allergy (pretest likelihood greater than that of general population) and who would benefit from penicillin, skin testing should be performed and penicillin used for patients with negative results. If however, the pretest likelihood of allergy is similar to the prevalence in the general population, skin testing can be foregone, and treatment with penicillin offered. In patients with definite penicillin allergy or anaphylaxis in whom penicillin therapy is the only option, inpatient admission for penicillin desensitization is warranted.

• Question 756:

  A 23-year-old female graduate student with acne and asthma presents to you with a chief complaint of headaches. She has noted a gradual increase in the intensity and frequency of the headaches to the point where they are interfering with her daily activities and studies. Your examination shows an obese young lady with papilledema. The remainder of your physical examination is normal The test ordered above was negative. Which of the following is your most appropriate next step?

  A. instruct the patient on a weight loss program and follow-up in 3 months
  B. begin diuretic therapy
  C. start the patient on sumatriptan for migraine headaches
  D. perform a lumbar puncture to measure opening pressure
  E. obtain an MRI of the brain and orbits, with and without contrast
  D. perform a lumbar puncture to measure opening pressure

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  Explanation

  Papilledema is optic disc swelling and implies raised intracranial pressure. Headache is a common associated symptom. The initial evaluation of papilledema should involve imaging, either by MRI or CT scan with and without contrast, to exclude mass lesions. If these studies are negative, then the subarachnoid opening pressure should be measured by lumbar puncture. An ESR is unlikely to be diagnostic in this case. It would be more important in the evaluation of vision loss or headache in a person over the age of 50. Neither a pregnancy test nor a glucose tolerance test would provide information on the cause of increased intracranial pressure. Pseudotumor cerebri is a condition of idiopathic intracranial hypertension. It is a diagnosis of exclusion that would be made in the presence of papilledema, normal imaging studies, and elevated opening pressure on lumbar puncture with normal CSF studies. The majority of patients with pseudotumor cerbri are young, female, and obese. This condition is treated with a carbonic anhydrase inhibitor, such as acetazolamide, which lowers intracranial pressure by reducing the production of CSF. Weight reduction, while important, is often unsuccessful in improving the condition by itself. Steroids, tetracycline, pregnancy, and oral contraceptives are not associated with the development of pseudotumor cerbri. Pseudotumor cerebri may ultimately resolve spontaneously, but there is a significant risk for development of impaired vision or even blindness if left untreated. The goal of treatment is the reduction of intracranial pressure. This may be accomplished in a number of ways. Use of medications such as acetazolamide or furosemide is considered a first-line therapy, with the aim of reducing CSF production. If pharmacologic treatment proves unsuccessful, alternative treatment options include surgical options such as optic nerve fenestration or creation of a ventricular-peritoneal shunt. Performing serial lumbar punctures is also possible but carries a number of associated risks including development of infections or headaches

• Question 757:

  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 What is the most serious long-term complication this patient could face?

  A. pancreatic cancer
  B. small bowel cancer
  C. gastric cancer
  D. colon cancer
  E. rectal cancer
  B. small bowel cancer

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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 758:

  Gastrin secretion is enhanced by which of the following?

  A. antral distention
  B. antral acidification
  C. presence of fat in the antrum
  D. sympathetic nerve stimulation
  E. duodenal acidification
  A. antral distention

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  Explanation

  Gastrin secretion is increased by vagal stimulation, antral distention, and by the presence of protein in the antrum. Antral acidification (pH = 1.5) decreases gastrin secretion by a feedback mechanism. The same is true with duodenal acidification.

• Question 759:

  A mother brings her 21/2-year-old daughter to your office for evaluation of frequent urination. The mother relates that the daughter seems to be urinating more frequently, up to 810 times in a day, over the past week. The girl complains of pain when she urinates, but the urine does not have any different odor to it. The mother says that the girl otherwise seems fine and still loves to take her bubble bath at night. The girl does not have a fever, weight loss, diarrhea, or vomiting What is the most likely diagnosis?

  A. pyelonephritis
  B. chemical urethritis
  C. retained vaginal foreign body
  D. type 1 diabetes mellitus
  E. diabetes insipidus
  B. chemical urethritis

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  Explanation

  Polyuria in a prepubertal female may indicate the presence of a UTI. AUTI must be excluded as the first step. Polyuria may also indicate vulvovaginitis. Vulvovaginitis in a prepubertal female is usually irritation and hygiene related. The presence of dysuria with the polyuria would make the utility of checking fingerstick glucose, as a screening test for diabetes, low yield. The nightly use of bubble baths makes chemical urethritis the most likely cause of this girl's polyuria and dysuria. Diabetes mellitus would present typically with polyuria, polydipsia, weight loss, and decrease in energy. There would also be no dysuria unless there were a concomitant UTI. Diabetes insipidus is a very rare disease in childhood and would be unlikely in an otherwise healthy girl. The presence of a retained foreign body (typically toilet paper) is usually seen in conjunction with a vaginal odor and discharge as well.

• Question 760:

  A 37-year-old multiparous White female, s/p bilateral tubal ligation, reports a family history remarkable for a mother diagnosed with bilateral breast cancer at the age of 43, from which she ultimately died, and a sister diagnosed with epithelial ovarian cancer at the age of 47, for which she is currently undergoing chemotherapy. Secondary to this worrisome family history, the patient elected to undergo genetic testing and was found to be a BRCA1 carrier.

  In view of her carrier status, you inform her of which of the following?

  A. She has a 3050% lifetime risk for the development of ovarian cancer.
  B. She has a 10% lifetime risk for the development of breast cancer.
  C. If she develops ovarian cancer, it will likely be 1015 years later than the normal onset of ovarian cancer seen in the general population.
  D. She is at increased risk for the development of hereditary nonpolyposis colorectal cancer (Lynch family syndrome type II).
  E. She has a lower risk for the development of Fallopian tube cancer than the general patient population.
  A. She has a 3050% lifetime risk for the development of ovarian cancer.

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  Explanation

  Though 85% of cancers develop spontaneously, approximately1012% will arise in patients with an inherited chromosomal defect that places them at increased risk for the development of certain types of cancers. Patients with an inherited defect in a tumor suppressor gene encoded on chromosome 2, for example, have an increased risk for the development of breast, ovarian, endometrial, and ovarian cancers and suffer from a syndrome known as hereditary nonpolyposis colorectal cancer, or Lynch family syndrome type II. Patients with an inherited defect in a tumor suppressor gene encoded on chromosome 17 (BRCA1), on the other hand, have an increased lifetime risk for the development of predominantly breast and ovarian cancer.

  Patients with a BRCA1 chromosomal defect have a 3050% lifetime risk for the development of ovarian cancer (compared to a 1.4% lifetime risk in the general patient population), a 6080% lifetime risk for the development of breast cancer (compared to a 10% lifetime risk in the general patient), and an increased lifetime risk for the development of both Fallopian tube cancer as well as peritoneal carcinoma. These cancers generally arise in affected women 1015 years earlier than when seen in nonaffected women. The risk for ovarian and breast cancer in carrier women is sufficiently high to warrantbilateral salpingo- oophorectomy once childbearing is complete, or by the age of 35, whichever comes first, as well as prophylactic bilateral mastectomy. An alternative to prophylactic surgery is a more vigilant screening program, with lifetime annual mammography beginning at the age of 25 and ovarian screening with annual or biannual ultrasound, CA-125 determination, and pelvic examination beginning at the age of 35. The efficacy of these screening programs is unproven.