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

USMLE USMLE-STEP-3 Online Questions & Answers

• Question 131:

  A 25-year-old male presents to his psychiatrist for follow-up after a lengthy psychiatric hospitalization. He was diagnosed with schizophrenia and discharged on risperidone 6 mg daily. He has no known medical problems and is without physical complaints. He continues to have some paranoia and ideas of reference regarding CNN, but he is not overtly delusional. He denies hallucinations as well. Although he feels "depressed" regarding his illness, he denies suicidal or homicidal ideation.

  Which of the following should be routinely monitored in this patient?

  A. body mass index (BMI)
  B. BP
  C. complete blood count (CBC)
  D. electrocardiogram (ECG)
  E. liver function tests (LFTs)
  A. body mass index (BMI)

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  Explanation

  Routine vital signs, ECG, and blood work such as CBC or LFTs are not required for ongoing use of second-generation (atypical) antipsychotics in healthy patients. Due to the risk of weight gain, hyperlipidemia, and diabetes ("metabolic syndrome"), regular monitoring for these is recommended. Due to variations in height, calculating a BMI is preferred when monitoring for weight gain in these patients. This patient has developed new-onset diabetes, presumably from the risperidone. Although all of the second- generation antipsychotics have Food and Drug Administration (FDA) warnings about causing metabolic syndrome, studies have demonstrated that they have varying rates of causing or exacerbating this:

  clozapine > olanzapine > quetiapine risperidone > aripiprazole ziprazidone.

  Therefore, assuming there is no contraindication to using one of the listed agents, aripiprazole would be the most appropriate choice based on its likely minimal risk of causing or exacerbating diabetes.

• Question 132:

  Which anatomic location is the most common site of extra-adrenal pheochromocytomas?

  A. duodenum
  B. inferior pole of the kidney
  C. paraaortic area
  D. parasplenic area
  E. peripancreatic area
  C. paraaortic area

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  Explanation

  Pheochromocytomas arise from neuroectoderamal cells and are most often found within the adrenal medulla. Ten percent of all pheochromocytomas are located outside of the adrenal gland along the embryologic path of the adrenal gland. The most common site of an extra-adrenal pheochromocytoma is in the paraaortic area.

• Question 133:

  A 45-year-old woman, mother of four children, comes to the ER complaining of the sudden onset of epigastric and right upper quadrant pain, radiating to the back, associated with vomiting. On examination, tenderness is elicited in the right upper quadrant, bowel sounds are decreased, and laboratory data show leukocytosis as well as normal serum levels of amylase, lipase, and bilirubin Which of the following is the most useful diagnostic test to confirm the diagnosis?

  A. two-way roentgenogram of the abdomen
  B. ultrasonography of the upper abdomen
  C. CT scan of the abdomen and pelvis with oral contrast
  D. HIDA (hydroxy iminodiacetic acid) scan
  E. magnetic resonance cholangiopancreatography (MRCP)
  B. ultrasonography of the upper abdomen

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  Explanation

  Cholelithiasis is much more common in women than men. In addition to gender, the development of gallstones can also be affected by age, weight, family history, and pregnancy. Gallstones often remain asymptomatic, but they can cause symptoms when they cause obstruction of the cystic duct. The result of this obstruction is biliary colic, which is experienced as epigastric pain radiating to the back and can be associated with nausea and vomiting. The presence of tenderness to palpation in the right upper quadrant, fever, and leukocytosis would suggest acute cholecystitis, a complication of gallstones. In a patient suspected of having complications of gallstones, the best test for evaluation is ultrasonography. Ultrasonography is highly sensitive in detecting gallstones and also provides details about the thickness of the gallbladder wall, the presence of pericholecystic fluid, and also the presence or absence of tenderness over the gallbladder during the examination (sonographic Murphy's sign). A two-way roentgenogram of the abdomen is much less sensitive, detecting only 20% of gallstones. A CT scan of the abdomen with IV and PO contrast can be sensitive in detecting the inflammatory changes associated with acute cholecystitis, but it is much more expensive and time consuming when compared to ultrasound. A HIDA scan, although sensitive and specific in the right setting, is generally reserved for more complicated cases where the diagnosis is unclear. Failure to visualize the gallbladder with HIDA scan in 1 hour indicates either partial or complete cystic duct obstruction and confirms the diagnosis of acute cholecystitis. However, this should not be the first-line test in evaluating a patient for acute cholecystitis. Finally, an MRCP can be very useful in evaluating the biliary tree and the presence of choledocholithiasis in a patient with cholecystitis and an elevated bilirubin, but does not have a role in the diagnosis of acute cholecystitis

• Question 134:

  A 54-year-old male with uncontrolled type II diabetes and well-controlled hypertension presents with complaints of erectile dysfunction. The patient requests Viagra (sildenafil), as his friends have used it with success. However, he is concerned as he was told by someone that Viagra can be fatal if used with some blood pressure medications. You would advise the patient that the use of which of the following is contraindicated in patients taking sildenafil?

  A. isosorbide mononitrate
  B. metoprolol
  C. verapamil
  D. captopril
  E. clonidine
  A. isosorbide mononitrate

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  Explanation

  Sildenafil is a phosphodiesterase inhibitor effective in the treatment of erectile dysfunction the mechanism of action of which is related to an increase in intracellular cyclic guanosine monophosphate (GMP). Nitrates increase cyclic GMP via the activation of guanylyl cyclase. When the two drugs interact, there can be a dramatic fall in blood pressure related to extreme vasodilation. The other selections can reduce blood pressure; however, since their mechanisms of action are not associated with the intracellular concentration of cyclic GMP, there is no synergistic interaction with sildenafil

• Question 135:

  A 65-year-old man presents to your office for evaluation of abdominal pain. The patient states that he has epigastric pain that radiates to his back. The pain is worse with eating and improves with fasting. The pain has been present for 6 months and is gradually worsening. The patient has lost 15 lbs but feels his oral intake has been adequate. He complains of greasy stools and frequent thirst and urination. Examination reveals a thin male with temporal wasting and oderate abdominal pain with palpation. The patient consumes approximately 1015 beers per day and smokes a pack of cigarettes per day for the past 20 years.

  On further questioning, the patient reports that he recently had a motor vehicle accident at night because he felt he could not see clearly. The most likely cause of this symptom is which of the following?

  A. vitamin B12 deficiency
  B. vitamin C deficiency
  C. vitamin D deficiency
  D. vitamin A deficiency
  E. vitamin K deficiency
  D. vitamin A deficiency

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  Explanation

  The patient's history and examination are worrisome for pancreatic disease, and he has strong signs of pancreatic insufficiency. His long history of alcohol use suggests the possibility of chronic pancreatitis or pancreatic cancer. Fecal fat studies would only confirm or quantify his steatorrhea. ACT scan would image the pancreas for changes consistent with chronic pancreatitis (duct dilation, calcifications, pseudocysts) and could look for a neoplasm of the pancreas as well. ERCP is not indicated as a first- line test in patients with abdominal pain given its risk of causing acute pancreatitis. Upper endoscopy would be helpful to rule out peptic ulcer disease and other gastric complaints, but would not provide more global information about the abdomen.

  The patient has greasy stools and weight loss, findings seen in patients with steatorrhea due to chronic pancreatitis.

  Patients with steatorrhea malabsorb fat-soluble vitamins (vitamins A, D, E, and K). "Night blindness" (poor night vision) due to vitamin Adeficiency is common among patients with advanced chronic pancreatitis and likely led to this patient's motor vehicle accident. The patient has DM as a consequence of pancreatic endocrine insufficiency, another feature of chronic pancreatitis. Diabetes develops when greater than 80- 90% of the gland has been destroyed. Patients with chronic pancreatitis have a coexisting loss of glucagon from islet cells and, thus, often become brittle diabetics, with hypoglycemia seen after insulin administration. Vitamin K and B12 deficiency, which the patient may have, do not cause hypoglycemia. The patient was previously noted to eat well, so inadequate oral intake is unlikely. Diabetic education should decrease the rate of chronic insulin overdosage.

  The patient has pancreatic exocrine insufficiency and thus cannot produce enough pancreatic enzymes to digest his food. Pancreatic enzyme replacement therapy in tablet form is a mainstay of therapy for chronic pancreatitis. It can rapidly reverse this problem by providing exogenously produced pancreatic enzymes to break down fats, carbohydrates, and proteins for absorption in the small bowel. The patient would not benefit from additional oral feedings without enzyme supplementation and would only worsen his steatorrhea by doing so. He can take food orally, so feeding via gastrostomy, TPN, or PPN are not indicated. The patient's worsening pain and weight loss despite therapy is worrisome for the development of pancreatic cancer. CA-19-9 is frequently (but not universally) elevated in pancreatic cancers, although it can be elevated in cholangiocarcinoma as well. PSA is associated with prostate cancer. CEA is associated with colon cancer. CA-125 is associated with ovarian cancer. AFP is associated with hepatocellular carcinoma.

• Question 136:

  Vital capacity is best described as the volume of air which is:

  A. inhaled during normal respiration
  B. expelled during passive expiration
  C. remaining in the lungs after passive expiration
  D. actively exchanging with pulmonary venous blood
  E. able to be expelled following maximal inspiration
  E. able to be expelled following maximal inspiration

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  Explanation

  Vital capacity is an important measure of respiratory function. It is defined as the maximum volume of air a person can expel following a maximum inspiratory effort. When vital capacity is normal, significant restrictive pulmonary disease is not present. Acutely decreased vital capacity indicates decreased ventilatory reserve.

• Question 137:

  A 22-year-old male arrives in the trauma bay via ambulance. He was intubated in the field after suffering a gunshot wound to the head. On examination, he has both an entrance and exit wound suggesting a transcranial trajectory of the bullet. On physical examination, you note that there are no brain stem reflexes present and his pupils are fixed and dilated. Given his

  A. Explain to them the process of organ transplantation and its benefits to others.
  B. Withdraw mechanical ventilator support and allow the patient to expire.
  C. Add a narcotic drip to the patient's treatment in order to ease his pain prior to withdrawing mechanical ventilation.
  D. Contact the donor services agency to have a professional trained in addressing organ donation come to speak with the family.
  E. Contact the transplant team and prepare the patient for the OR because the organs are too vital to waste regardless of the family's wishes.
  D. Contact the donor services agency to have a professional trained in addressing organ donation come to speak with the family.

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  Explanation

  Organ donation can often be a very sensitive topic. As the transplant waiting lists continue to grow, the process of approaching the family of potential organ donors has been of great interest. In this setting, it is important to provide adequate information in a nonthreatening manner. Even today with donor cards, living wills, and so on, there can still be conflict between the patient and family, or even amongst family members, with regard organ transplantation. An individual who has been trained to discuss organ transplantation with grieving families best addresses this sensitive topic. Furthermore, regardless of the decision after appropriate discussions are held, it is vital to respect the family's choice.

• Question 138:

  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 most likely diagnosis for this patient?

  A. chronic pancreatitis
  B. Crohn's disease
  C. celiac sprue
  D. Whipple disease
  E. ulcerative colitis
  C. celiac sprue

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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 139:

  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

  

  What is the mechanism that best explains this patient's hyperkalemia?

  A. DKA
  B. acute kidney failure leading to an inability to excrete potassium in the urine
  C. release of potassium from the destruction of neoplastic cells
  D. chemotherapy-induced hyperkalemia
  E. type 4 renal tubular acidosis
  C. release of potassium from the destruction of neoplastic cells

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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 140:

  You are called to see a newborn in the nursery because the nurse is concerned that the baby may have Down syndrome.

  If you were to perform an abdominal x-ray, what is the most likely finding that would be seen?

  A. "double-bubble" sign
  B. scimitar sign
  C. normal gas patterns
  D. free fluid in the abdomen
  E. pneumatosis intestinalis
  A. "double-bubble" sign

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  Explanation

  The most common finding in a newborn with Down syndrome is hypotonia. Other common findings include single palmar crease, flat facial profile, macroglossia, and wide space between the first and second toes. Hypotonia in the newborn period should prompt close evaluation and follow-up. Caf?au lait spots are associated with neurofibromatosis. High arched palates are associated with fragile X syndrome.

  Ambiguous genitalia are commonly seen in CAH.

  Children with Down syndrome are at an increased risk for hypothyroidism. It may be hard to detect without routine laboratory screening as they will commonly have mental retardation and developmental delay as part of their syndrome. Hypothyroidism may not be present in the immediate newborn period and requires, at a minimum, annual testing throughout the child's life. The other findings listed are not specifically associated with Down syndrome. Lens dislocation is commonly found with Marfan syndrome or homocysteinuria.

  Children with Down syndrome have an increased prevalence of duodenal atresia. Pyloric stenosis is uncommon to see in the newborn period. It tends to present with nonbilious vomiting usually after 24 weeks of age. Hirschsprung disease (aganglionosis coli) presents with constipation and failure to pass stool. Infants with Hirschsprung disease commonly will not pass stool in the first days of life. Biliary atresia is a progressive cause of jaundice in an infant. It is the most common cause of a cholestatic jaundice in the newborn period. Emesis is not typically associated with biliary atresia. Milk protein allergy is a common cause of bloody stools in the first few months of life, but does not have bilious emesis associated with it.