USMLE USMLE-STEP-2 Online Practice Questions and Exam Preparation

USMLE USMLE-STEP-2 Online Questions & Answers

• Question 411:

  Monoamine oxidase (MAO) inhibitory effect. Match the antidepressants below with the effect described.

  A. amitriptyline
  B. nefazodone
  C. citalopram
  D. phenelzine
  E. duloxetine
  D. phenelzine

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  Explanation

  The drugs listed in this question are examples of the various classes of antidepressants. These classes include the tricyclics, the SSRIs, the MAOIs, the triazolopyridines, and the serotonin-norepinephrine reuptake inhibitors. Understanding the site of action, neurotransmitter( s) involved, and side effects characteristic of these classes is helpful in selecting an antidepressant for a particular patient. SSRIs that are comparable in their antidepressant effects to the older tricyclics but significantly safer when taken in larger doses, as in suicidal overdose, are frequently used as the first choice in the treatment of depression. An example here is citalopram. Drugs that both inhibit serotonin reuptake and block 5-HT2 receptors are characteristic of the triazolopyridines. The overall effect of these actions is believed to decrease both depression and anxiety in patients. There are two drugs in this class: trazodone and nefazodone. Strong sedation caused by histaminergic and anticholinergic activity is seen in the older antidepressants--the tricyclics. These also have both serotonin and norepinephrine effects that are important in decreasing depression. Amitriptyline is the drug example listed here.

  Drugs demonstrating little sedation and significant serotonin, norepinephrine, and dopamine effects are more characteristic of the serotoninnorepinephrine reuptake inhibitors. They are effective in managing depression because there is no antihistaminergic activity and little sedation is seen. Duloxetine and Venlafaxine are examples. MAOIs increase the concentrations of serotonin, norepinephrine, and dopamine by inhibiting their degradation. The MAOIs, although effective as antidepressants, are used relatively infrequently because of the potential development of a hypertensive crisis induced by consuming tyramine- containing foods while on the MAOI. An example here is phenelzine.

• Question 412:

  A large segment of the population in your community smokes. In order to convince your patient population that it would be beneficial to quit smoking in order to prevent lung cancer, you conduct a casecontrol study of cigarette smoking and lung cancer. The results from that study can be found in the table below.

  

  Using the same table, what is the relative risk?

  A. 3
  B. 6
  C. 9
  D. 12
  E. cannot be calculated
  E. cannot be calculated

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  Explanation

  A true risk ratio cannot be calculated from a case-control study.

• Question 413:

  A 4-year-old previously healthy girl presents to the emergency department with a 24-hour history of rectal bleeding and dizziness. She has no other gastrointestinal symptoms. On examination, she appears pale. Her heart rate is 140 beats/min, and she has a 20 mmHg postural drop in systolic blood pressure. The child's abdomen is nondistended and nontender, and fresh blood and clots are in the rectal vault on rectal examination.

  Which of the following is the most appropriate diagnostic study to order for this patient?

  A. colonoscopy
  B. barium enema
  C. technetium scan
  D. UGI contrast study with small-bowel follow-through
  E. laparoscopy
  C. technetium scan

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  Explanation

  Hemorrhage associated with a Meckel's diverticulum classically presents with painless rectal bleeding in the absence of other gastrointestinal symptoms. The amount of hemorrhage may be enough to result in hypovolemia, with pallor, tachycardia, and postural hypotension. Abdominal examination is usually normal. Diagnosis is confirmed by technetium scan, with the isotope concentrated in the gastric mucosa of the diverticulum. Initial management should include IV fluid resuscitation and transfusion as needed, before laparotomy and diverticulectomy with resection of the adjacent ileum. Rectal polyps, hemorrhoids, and anal fissures may be associated with rectal bleeding. The bleeding is usually small in amount and often temporally related to defecation, typically on the surface of the stool or after defecation. Colonoscopy and proctoscopy are useful adjuncts to diagnosis. Bleeding associated with intussusception is described as "currant jelly" and is secondary to mucosal ischemia of the lead point. These children are most commonly between 2 months and 2 years of age, and often have a prodromal viral illness. They present with colicky abdominal pain and dehydration. Management includes hydrostatic reduction.

• Question 414:

  A 48-year-old woman had a biopsy of a friable, bleeding lesion on her cervix. She had not had a pelvic examination or Pap smear for about 12 years. The biopsy is reported as invasive squamous cell carcinoma of the cervix. On bimanual examination, there is induration to the side wall of her pelvis.

  Which of the following is the stage of her cervical cancer?

  A. IA
  B. IB
  C. IIB
  D. IIIB
  E. IV
  D. IIIB

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  Explanation

  Cancer of the cervix that has not invaded cervical stroma is stage 0 carcinoma in situ. Cancer that has invaded the cervical stroma but has not spread beyond the cervix is stage I. Involvement of the upper vagina or parametria (but not to the pelvic sidewall) is stage II. Stage III is involvement of the lower third of the vagina (IIIA) or parametria to the pelvic sidewall (IIIB). Extension outside the reproductive tract is stage IV.

• Question 415:

  Select the organism associated with the following clinical findings:

  A male student returns from traveling to a developing country, with a complaint of eructation, abdominal cramps, and diarrhea for the past 2 weeks, and has lost 10 lbs.

  A. aureus
  B. beta-hemolytic Streptococcus
  C. perfringens
  D. Mycoplasma pneumoniae
  E. Haemophilus pertussis
  F. Helicobacter pylori
  G. Escherichia coli
  H. Rickettsia prowazekii
  I. Giardia lamblia
  I. Giardia lamblia

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  Explanation

  Giardiasis may cause cramping and a chronic diarrheal syndrome, with malabsorption and weight loss. Its distribution is worldwide, particularly where hygienic standards are not high. It also occurs sporadically in high-risk individuals. Streptococcal pyoderma, including erysipelas and impetigo, has been demonstrated to precede acute glomerulonephritis. Even when appropriate antibiotics are given in adequate dosage and duration for these conditions, renal damage may still result. Prevention thus consists of wound care, including cleaning wounds well and removal of crust. Mycoplasma infections are particularly common in families with younger children. They are frequently imported to the family by school-aged children, leading to a low-grade fever and persisting tracheobronchitis in the parents, or more acutely, an atypical pneumonia. G. lamblia is found in up to 20% of homosexual males, and may cause chronic diarrhea, although in these patients it tends to be asymptomatic. E. coli was first reported as a cause of watery diarrhea in nurseries in the 1940s. Although nursery epidemics with enteropathogenic serotypes had decreased in recent years in the United States, the increase of infant- child day care centers has resulted in their relatively frequent occurrence. Furunculosis is most frequently caused by coagulase-positive staphylococcal infections. The public health significance of this largely relates to the hazards of skin infections in food handlers and subsequent staphylococcal toxin in the food, leading to staphylococcal intoxication food-borne disease. H. pylori has been associated with gastric ulcers, but not with duodenal ulcers. Otitis media, whether acute or with effusion, commonly results from viral infection, such as by RSV. Various other organisms may be responsible including Streptococcu pneumoniae, H. influenzae, and others. C. perfringens, with rare exceptions, is transmitted in a meat dish prepared in bulk. Under propitious circumstances for the organism, especially on cooling of the food, bacterial multiplication can be very rapid. Symptoms begin to occur in the affected population in about 12 hours. Epidemic typhus is a rickettsial illness. Man is the host and long-term reservoir. The vectors are body lice (P. humanus corporis). The rickettsia are not present in human excretions and cannot be transmitted by person-to-person contact.

• Question 416:

  For each of the following scenarios, select the gas exposure responsible for the signs and symptoms.

  A man has been pulled unconscious from a mine. No odors are noted, but an experienced miner says there was coal damp in the mine.

  A. carbon monoxide
  B. methane
  C. hydrogen sulfide
  D. ozone
  E. sulfur dioxide
  B. methane

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  Explanation

  Methane is a colorless, odorless, flammable gas sometimes encountered in mines and wells. Methane (coal damp) is a frequent cause of death in inadequately ventilated mines and wells. It acts as an asphyxiant as well as being explosive. Miners used to take caged animals, especially birds, with them. The birds succumbed to the asphyxiants (methane and carbon dioxide) sooner than humans.

• Question 417:

  A 12-year-old boy comes to the clinic for a sports physical. He is new to your practice. He comes with his foster mother, who states that he was recently placed in her care because of his mother's problems with drug abuse. Although a complete medical history is not available, she knows that he has not received regular care. He does not have any chronic medical problems. She also knows that his father died of heart disease when he was 35. On physical examination, the boy's height is greater than the 95th percentile. His arm span exceeds his height.

  As you continue your physical examination, you remember that congenital heart disease is common in this particular syndrome. Which of the following is the most likely congenital heart defect in patients with this syndrome?

  A. supravalvular aortic stenosis
  B. AV canal defects
  C. coarctation of the aorta
  D. pulmonary valvular stenosis
  E. mitral valve prolapse
  E. mitral valve prolapse

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  Explanation

  Marfan syndrome is associated with mitralvalve prolapse and aortic root dilatation.

• Question 418:

  When you examine the back of an elderly gentleman, you note multiple brown papules and nodules having a "stuck on" appearance. These are shown in Figure. The patient tells you they have been there for years.

  Which of the following is the most likely diagnosis?

  

  A. melanocytic nevi
  B. actinic keratoses
  C. seborrheic keratoses
  D. seborrheic dermatitis
  E. malignant melanoma
  C. seborrheic keratoses

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  Explanation

  This man has multiple seborrheic keratoses, which are very common, benign pigmented tumors that occur after age 30, especially on the trunk and face. Melanocytic nevi are usually small, circumscribed, pigmented macules or papules, rather than large "stuck-on" nodules. Actinic keratoses are red, scaly (not dark) lesions on the face and arms that are from suninduced damage. Seborrheic dermatitis is a red, scaly rash along the scalp, eyebrows, and nasolabial folds. Malignant melanoma would be in the differential if it were a single lesion.

• Question 419:

  A 65-year-old man presents to the emergency department with sudden onset of pain and weakness of the left lower extremity of 2-hour duration. Past history reveals chronic atrial fibrillation following a myocardial infarction 12 months ago. On examination, he is found to have a cool, pale left lower extremity with decreased strength and absent popliteal and pedal pulses. The opposite leg has a normal appearance with palpable pulses.

  Which of the following is the most appropriate first step in management of this patient?

  A. echocardiography
  B. anticoagulation with heparin
  C. anticoagulation with warfarin
  D. arteriography
  E. alkalinization of the urine with IV sodium bicarbonate
  B. anticoagulation with heparin

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  Explanation

  The diagnosis of arterial embolism is suggested when the patient presents with an acute onset of severe pain, pallor, pulselessness, paresthesia, and paralysis (five P's). The presence of atrial fibrillation is strongly suggestive of a cardiac source of the emboli. The first step in management is immediate heparinization to prevent propagation of the clot and maintain patency of collaterals. The cornerstone of treatment is thromboembolectomy. Thrombolytic therapy is reserved for treatment of irretrievable clots in small vessels. Fasciotomy, alkalinization of the urine, and mannitol diuresis are adjuncts to treatment, particularly if there is a delay in operation, increasing the risk of a reperfusion injury. Anticoagulation has been shown to reduce the rate of recurrent embolism.

• Question 420:

  On the first pelvic examination of an 18-yearold nulligravida, a soft, fluctuant mass is found in the superior aspect of the right labia majora. This is asymptomatic. She tells you it has been present for several years and seems to be enlarging slightly. There is no defect in the inguinal ring. Which of the following is the most likely diagnosis?

  A. vulvar varicosities
  B. inguinal hernia
  C. femoral hernia
  D. cyst of the canal of Nuck
  E. granuloma inguinale
  D. cyst of the canal of Nuck

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  Explanation

  The most likely diagnosis is a cyst of the canal of Nuck. These arise from inclusions of the peritoneum at the inferior insertion of the round ligament into the labia majora. They are analogous to a spermatic cord hydrocele and are typically found at the superior aspect of the labia majora. Vulvar varicosities usually involve most of the labia, occur in older and parous women, and have a classical "bag of worms" appearance. Given the physical findings, a hernia is unlikely. An ultrasound may be useful to distinguish a hernial sac from a cyst of the canal of Nuck. One-third of women with a cyst of the canal of Nuck may have a coexistent inguinal hernia.