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

USMLE USMLE-STEP-3 Online Questions & Answers

• Question 11:

  A 34-year-old male undergoes an uneventful excision of a parathyroid adenoma. The following postoperative day, he complains of numbness around his lips. Which of the following is the most likely cause of this symptom?

  A. hypocalcemia secondary to hypomagnesemia
  B. hypocalcemia due to acute renal failure
  C. hypocalcemia due to hungry bone syndrome
  D. hypocalcemia due to inadvertent injury to the recurrent laryngeal nerve
  E. postoperative hematoma of the neck
  C. hypocalcemia due to hungry bone syndrome

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  Explanation

  Hungry bone syndrome refers to hypocalcemia following surgical correction of hyperparathyroidism in patients with severe, prolonged disease, as serum calcium is rapidly taken from the circulation and deposited into the bone. Symptoms usually occur within 2448 hours following parathyroidectomy, when calcium levels reach a nadir. Early symptoms include numbness and tingling in the perioral area, fingers, or toes. Advanced symptoms include nervousness, anxiety, and increased neuromuscular transmission evidenced by positive Chvostek's and Trousseau's signs, carpal pedal spasm, and hyperactive tendon reflexes. In severe cases, one may develop a prolonged QT interval on ECG. Patients who manifest any signs or symptoms of hypocalcemia always require intervention. In severely symptomatic patients, treatment should begin with intravenous calcium gluconate. Mildly symptomatic patients may be given oral calcium in the form of calcium lactate, calcium carbonate, or calcium gluconate. If hypocalcemia remains despite calcium supplementation, additional therapy with vitamin D may be needed. Supplemental calcium and vitamin D therapy should be continued until serum calcium levels return to normal

• Question 12:

  A 31-year-old female presents to her physician complaining of rapid onset of hirsutism, deepening of the voice, irregular menses, clitoral enlargement, and acne. Which of the following is the most likely cause of this clinical presentation?

  A. polycystic ovary syndrome (PCOS)
  B. Cushing syndrome
  C. type II diabetes mellitus
  D. androgen secreting tumor
  E. congenital adrenal hyperplasia
  D. androgen secreting tumor

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  Explanation

  Androgen excess syndromes are common and usually characterized by one or more of the following problems: hirsutism, acne, weight gain, or irregular menses. PCOS is the most common disorder of androgen excess. Other syndromes that often result in signs and symptoms of androgen excess in adults include Cushing syndrome and late-onset congenital adrenal hyperplasia. The classic presentation of a patient with an androgen-secreting tumor of the ovary or adrenal gland involves the rapid onset of symptoms. Late-onset congenital adrenal hyperplasia and an androgen-secreting tumor are the only disorders of androgen excess usually resulting in clitoromegaly.

• Question 13:

  A 74-year-old male with a history of hypertension, type II diabetes, myopia, and cataract surgery 2 weeks ago presents with the sudden onset of severe flashes of light and multiple new floaters in his right eye. He denies photophobia, ocular trauma, or diplopia. He also states that he feels as if there is a curtain lowering over his right eye. Your examination and a stat ophthalmology consultation confirm your clinical diagnosis. Of the choices listed below, what would be the most appropriate next step to provide definite treatment for this patient?

  A. lens removal and surgical replacement
  B. corneal transplant
  C. removal of vitreous humor (posterior vitrectomy)
  D. intraocular antibiotics
  E. stat angiogram and thrombolytics if needed
  C. removal of vitreous humor (posterior vitrectomy)

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  Explanation

  Retinal detachment is fairly uncommon but should be considered for any patient with visual loss. Risk factors for retinal detachment include advanced age, myopia, cataract surgery, focal retinal atrophy, congenital eye diseases, fibromuscular hyperplasia (FMH) retinal detachment, prematurity, uveitis, diabetic retinopathy, and hereditary vitreoretinopathy. Patients may be asymptomatic but usually present with sudden onset of flashes of light, new floaters, visual field defects, and a sensation of a "curtain" coming down over their visual field. Prompt ophthalmology evaluation, preferably by a retinal specialist, is warranted. Immediate care is paramount as often retinal tears can be managed so as to prevent retinal detachment. Symptomatic retinal tears can be managed with laser or cryo burns to create a chorioretinal scar that prevents fluid access to the subretinal space. This is effective 95% of the time to prevent progression to a retinal detachment. Retinal detachment can be surgically corrected with scleral buckling techniques (90% success rate) or posterior vitrectomy (7590% success rate).

• Question 14:

  Numerous types of cancers are associated with infectious diseases. For which of the following cancers is there a vaccine currently available against the infectious agent which leads to the tumor?

  A. Burkitt's lymphoma
  B. gastric carcinoma
  C. hepatocellular carcinoma
  D. nasopharyngeal carcinoma
  E. Kaposi's sarcoma
  C. hepatocellular carcinoma

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  Explanation

  Burkitt's lymphoma and nasopharyngeal carcinomas are associated with the Epstein- Barr virus. Gastric carcinoma is associated with H. pylori infection. Kaposi's sarcoma is associated with human herpesvirus 7. The rate of hepatocellular carcinoma is greatly increased in those with chronic hepatitis B and C. Hepatitis B virus infection is the leading cause of hepatocellular carcinoma worldwide, usually after congenital infection in Asia and Africa. Of these infections, only hepatitis B has a widely available, routinely recommended vaccine.

• Question 15:

  A patient presents to the ED complaining of abdominal pain out of proportion to her examination. Initial vital signs are: BP 70/30, HR 120. The patient does report a prior history of abdominal pain after eating. Which of the following statements regarding this condition is most accurate?

  A. A CT scan which shows superior mesenteric artery (SMA) thrombosis or bowel wall thickening requires an immediate operation.
  B. The most common site of embolic event is the SMA.
  C. Nonocclusive mesenteric ischemia is treated with arterial bypass.
  D. Patients with cardiac arrhythmias arenot at increased risk.
  E. After volume resuscitation, the initial diagnostic study for this patient is esophagogastroduodenoscopy (EGD).
  B. The most common site of embolic event is the SMA.

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  Explanation

  Severe abdominal pain is the hallmark presentation of acute mesenteric ischemia. The pain is often described as being out of proportion to examination. It is most often caused by an embolic event to the SMA. Patients with cardiac arrhythmias are at greater risk for having an embolic event. Nonocclusive mesenteric ischemia is thought to be due to reactive arterial vasoconstriction and is not a surgically correctible disease. CT scan findings of SMA thrombosis or gas in the bowel wall would necessitate emergency surgery.

• Question 16:

  A54-year-old Asian female with no significant medical history presents with frontal headache, eye pain, nausea, and vomiting. Her abdominal examination shows mild diffuse tenderness but no rebound or guarding. Her mucous membranes are dry. Her vision is blurry in both eyes, her eyes are injected but her extraocular muscles are intact. Her pupils are mid-dilated and fixed

  Which of the following is the most likely diagnosis?

  A. diabetic ketoacidosis (DKA)
  B. appendicitis
  C. angle closure glaucoma
  D. perforated colon due to inflammatory bowel disease (IBD)
  E. cerebellar malignancy
  C. angle closure glaucoma

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  Explanation

  The presence of headache, eye pain, nausea, and vomiting should prompt the consideration of the diagnosis of acute angle closure glaucoma. This is a rare but serious condition in which the aqueous outflow is obstructed, and the intraocular pressure abruptly rises. Susceptible eyes have a narrow anterior chamber and when the pupil becomes dilated, the peripheral iris blocks the outflow via the anterior chamber angle. Edema of the cornea occurs, resulting in cloudiness on examination. Diagnosis is made by measuring the intraocular pressure during an acute attack. Treatment includes medications to induce miosis in an effort to relieve the blockage or, if that fails, surgical intervention. In some patients, the headache or GI symptoms can overshadow the ocular symptoms, resulting in a delay in diagnosis and unnecessary workup for other conditions. In this case, the lack of findings on abdominal examination makes appendicitis or perforated bowel unlikely. DKA can present with primary GI symptoms, but would not explain the ocular symptoms. Similarly, cerebellar or other brain tumors may cause headache, nausea, and vomiting, but would not be causes of a painful, red eye.

• Question 17:

  A concerned mother brings her 5-year-old daughter to the ER because she noticed redness around her daughter's genital region while bathing her last night. The child has not complained of any discomfort, itching, bleeding, or inappropriate contact with other adults. On external inspection of her labia, you see the fusion of the labia minora and generalized erythema. The most appropriate treatment would be which of the following?

  A. surgical excision
  B. vaginoscopy and biopsies
  C. ice packs and sitz baths
  D. lidocaine ointment
  E. topical estrogen cream
  E. topical estrogen cream

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  Explanation

  Labial agglutination is a clinical diagnosis, with a greater prevalence occurring in pediatric or elderly patients. Forced manipulations of the genital region are to be avoided, as the condition readily responds to topical estrogen therapy.

• Question 18:

  A newborn male is brought to you in the neonatal intensive care unit (NICU). On physical examination, you notice that the infant has deficient abdominal musculature and undescended testes. Your suspicion is high for a certain condition.

  Upon further imaging, what associated finding would be expected?

  A. posterior urethral valves on a voiding cystourethrogram (VCUG)
  B. hydrocephalus on head ultrasound
  C. cardiomegaly on chest x-ray (CXR)
  D. bilateral adrenal enlargement on abdominal ultrasound
  E. tracheoesophageal fistula on an upper gastrointestinal (UGI) series
  A. posterior urethral valves on a voiding cystourethrogram (VCUG)

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  Explanation

  The constellation of cryptorchidism, posterior urethral valves, and abnormal abdominal musculature is called Eagle-Barrett syndrome. Another name is prune belly syndrome. The greatest morbidity comes from the poor amniotic fluid production, due to bladder outlet obstruction, with a resulting pulmonary hypoplasia. Cushing's triad are hypertension, bradycardia, and widened pulse pressure. This is seen as terminal findings associated with increased intracranial pressure. VATER association has multiple anomalies, none of which are the three mentioned. VATER is a mnemonic which stands for Vertebral anomalies, Anal atresia (imperforate), Tracheo-Esophageal fistula, and Renal anomalies (the R also indicated Radial anomalies). It is sometimes referred to as VACTERL association in which the C indicates Cardiac anomalies with the L indicating Limb anomalies. Potter's syndrome is bilateral renal agenesis. This condition is fatal, due to marked pulmonary hypoplasia. The Jones criteria are used in the diagnosis of ARF.

• Question 19:

  You would like to design a study to evaluate the prevalence of a certain disease in your patient population.

  Which study design would be the most appropriate?

  A. case-control study
  B. cohort study
  C. prospective, randomized-controlled trial
  D. cross-sectional study
  E. meta-analysis
  D. cross-sectional study

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  Explanation

  Explanations:

  All types of study designs have potential benefits and drawbacks and it is important to understand this when designing research or reviewing research reports. A cross-sectional study is one in which information is gathered from a certain population at one point in time with no follow-up period. This type of study is very useful for the determination of the prevalence of a disease or risk factor in a population at a certain point in time. Cross-sectional studies cannot determine cause and effect because there are no interventions being made and there is no follow-up. A case-control study is very useful and efficient at studying diseases that occur rarely. In a case-control study, persons with a disease are identified and then information is determined by looking back in time (i.e., retrospective review). Apopulation of those without the disease (controls) is also defined and studied in the same way.

  The prevalence of a risk factor in the cases and controls can then be determined and compared. A case- control study cannot prove cause and effect, but it can be a powerful tool to determine risk factors that can generate hypotheses for further study. Acohort study is one in which a population is defined and then followed over time. A cohort study may be either prospective or etrospective. Cohort studies can be used to describe the incidence of diseases over time or to determine associations between predictors and outcomes. Cohort studies are inefficient for the study of rare outcomes, as a very large sample size would be required in order to find a few events. Aprospective, randomizedcontrolled trial is the gold standard study for determining the effect of a treatment or intervention. It is not the type of study that would be used to determine the prevalence of a disease in a population or to determine what risk factors are associated with the development of a disease. A meta-analysis is a systematic review of completed research studies. By evaluating similarly done studies, the meta-analysis technique can allow for an evaluation of a body of literature and can be used to increase the overall statistical power by creating a larger sample by combining studies.

  The odds ratios given show that both risk factors X and Y occurred more often in those with the disease (cases) than they did in those without the disease (controls). Neither of the CIs given cross 1, therefore, these are statistically significant findings. We cannot use this type of study to definitively prove cause and effect, therefore option A is false. While risk factor X had a higher odds ratio for the development of the disease than risk factor Y, no prognostic data are supplied and none can be inferred from the information given, therefore B is false. The odds ratios as given in this case compare the prevalence of a risk factor in the case group with the control group, not the prevalence of one risk factor compared to another. For this reason, we cannot say which risk factor is more common in the population and option C is false. No absolute numbers are presented in this question and therefore we cannot determine how often each of the risk factors occurs in our population, so E is false as well

• Question 20:

  A20-year-old male has had a recent wide local excision of a 1.5 mm melanoma from the right ankle. There is no evidence of metastatic disease. The most important prognostic factor for this patient is which of the following?

  Which of the following is true regarding melanoma?

  A. Chest radiographs are not recommended as a part of a patient's follow-up surveillance.
  B. Timely treatment of metastatic melanoma has been shown to have an effect on mean survival.
  C. Elevated serum LDH suggests metastatic melanoma.
  D. Patients without clinical lymphadenopathy are not at risk for metastatic involvement.
  E. High mitotic rate and a lower Clark level are poor prognostic signs.
  C. Elevated serum LDH suggests metastatic melanoma.

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  Explanation

  In patients who have melanoma that is confined to the skin (i.e., no evidence of metastatic disease), the most important prognostic factor is the Breslow histologic depth of the tumor. The age of the patient and location of the tumor also play a role in prognosis, but to a lesser degree. The forearm and leg tend to have a better prognosis; scalp, hands, feet, and mucous membranes have a worse prognosis. Older persons tend to have poorer prognoses, as well. Standard treatment for melanoma involves surgical excision. Sentinel lymph node biopsy should also be performed in any patient who has a melanoma that is at least 1 mm thick. This aids in determining whether melanoma cells have metastasized to the local lymph node basin. If the sentinel lymph node biopsy is negative for melanoma cells, no further lymph node studies are necessary. However, a positive biopsy warrants complete lymph node dissection. In addition to this situation, complete lymph node dissection is indicated in the setting of clinical lymphadenopathy regardless of evident distant metastasis. High dose interferon alpha-2 therapy is aviable option for use as adjuvant therapy in patients at high risk for disease recurrence, having been shown to prolong periods of remission and possibly improve mortality. Single-agent chemotherapy is generally used in patients with stage IV melanoma and is considered more for palliative purposes.