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

USMLE USMLE-STEP-2 Online Questions & Answers

• Question 551:

  A54-year-old woman presents to her physician for an opinion regarding additional therapy following curative resection of recently diagnosed colon cancer. She underwent uncomplicated sigmoid resection for invasive colon cancer 4 weeks ago. The pathology revealed carcinoma invading into, but not through, the muscularis propria, with one of eight positive mesenteric nodes. There was no evidence of liver metastases at the time of operation. Preoperative chest x-ray and CT scan of the abdomen showed no evidence of distant disease. Preoperative carcinoembryonic antigen (CEA) level was normal. Past history is positive for diabetes and mild hypertension. Examination is unremarkable except for a healing abdominal incision. Which of the following is the most appropriate recommendation regarding adjuvant therapy?

  A. no therapy indicated
  B. 5-fluorouracil chemotherapy
  C. 5-fluorouracil chemotherapy with leucovorin
  D. doxorubicin (Adriamycin) chemotherapy
  E. Adriamycin chemotherapy with methotrexate and cytoxan
  C. 5-fluorouracil chemotherapy with leucovorin

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  Explanation

  The stage of colon cancer is based on the depth of invasion, nodal involvement, and distant metastases. Stage 0 represents carcinoma in situ, stage I invasion of the submucosa or muscularis propria without node involvement, stage II invasion through the muscularis propria or directly invading other organs without nodal involvement, stage III any depth of invasion with nodal metastasis, and stage IV any depth of invasion or nodal status with distant metastases. Adjuvant therapy has been shown to be beneficial in patients with stage III disease in randomized studies. The recommended regimen is 5-fluorouracil-based chemotherapy with leucovorin, rather than 5-fluorouracil alone. Adriamycin therapy, either alone or with other agents, has not been shown to be beneficial in patients with colon cancer. No adjuvant therapy would be indicated for patients with stage 0, I, or II disease, although some patients with stage II disease manifesting poor prognostic indicators may be candidates for adjuvant therapy.

• Question 552:

  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.

  To complete the staging of her cancer according o International Federation of Gynecology and Obstetrics (FIGO) standards, she should have hich of the following?

  A. lymphangiogram
  B. pelvic venogram
  C. cystoscopy
  D. magnetic resonance imaging (MRI) scan f her abdomen
  E. laparoscopy
  C. cystoscopy

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  Explanation

  The intent of staging is to judge the results of various treatments and to compare treatment results worldwide. Because advanced procedures such as venography, lymphangiography, MRI or CT scans, and laparoscopy are not universally available, staging of cervical cancer remains primarily clinical. Such tests as cystoscopy, proctosigmoidoscopy, barium enema, IVP, and plain radiographs of the abdomen and chest are permitted. Evidence of mucosal cancer confirmed by biopsy at the time of cystoscopy changes her diagnosis to stage IV cervical cancer.

• Question 553:

  A 68-year-old man presents to the physician's office complaining of progressive dysphagia over the last 3 months associated with mild chest discomfort. He reports a 15-lb weight loss, a 30 pack-year smoking history, and occasional alcohol intake. The physical examination, including vital signs, is unremarkable. A chest x-ray was normal, and a barium esophagogram shows an irregular filling defect in the distal third of the esophagus with distortion and narrowing of the lumen.

  Which of the following is the most likely diagnosis?

  A. esophagitis with stricture
  B. esophageal carcinoma
  C. lung carcinoma with invasion into the esophagus
  D. lymphoma
  E. achalasia
  B. esophageal carcinoma

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  Explanation

  Progressive dysphagia in an older adult warrants evaluation, especially with associated symptoms of weight loss, chest pain, or hematemesis. A barium esophagogram is the first study that should be obtained. The typical carcinoma demonstrates an irregular, rigid narrowing of the esophageal wall with distortion of the lumen. Achalasia demonstrates a narrow, tapering bird's beak appearance of the distal esophagus. Development of an esophageal stricture causes slowly progressive dysphagia, usually after a long history of gastroesophageal reflux disease (GERD). Esophagoscopy and biopsy are mandatory for evaluation of esophageal stenosis and yield a diagnosis of carcinoma in 95% of patients with malignant strictures. CT scanning is the standard technique for staging, once the diagnosis has been made. Bronchoscopy is helpful in patients with upper and middle third carcinomas to exclude invasion of the trachea or bronchi before esophagectomy.

• Question 554:

  Several groups of organic compounds are associated with serious toxic effects when highly toxic and dangerous as a solvent; used in the manufacture of rubber, dyes, and lubricating oils

  A. nitrosamines
  B. epoxy compounds
  C. PCBs
  D. formaldehydes
  E. organophosphorus compounds
  A. nitrosamines

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  Explanation

  Nitrosamines are highly toxic and dangerous to handle when used as solvents. Toxic amounts may be absorbed without warning because danger signals such as specific odor or irritant effects are lacking. The manufacture of rubber, dyes, lubricating oils, explosives, insecticides, and fungicides, as well as the electrical industry, all have associations with these substances. Nitrosamines have animal carcinogenic properties and have been transmitted transplacentally in rats.

• Question 555:

  A 22-year-old woman with cystic fibrosis is engaged to be married and asks you about childbearing.

  How should you advise her?

  A. An amniocentesis should be done to detect fetal cystic fibrosis.
  B. Pregnancy is contraindicated because maternal mortality is significantly increased.
  C. Her children have a 25% chance of having cystic fibrosis.
  D. Pregnancy and delivery are usually successful with special care and precautions.
  E. She should use nasal oxygen throughout pregnancy to minimize fetal hypoxemia.
  D. Pregnancy and delivery are usually successful with special care and precautions.

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  Explanation

  With improved care, women with cystic fibrosis now survive into the reproductive age and are capable of carrying a pregnancy successfully. No special precautions such as prolonged hospitalization, oxygen supplementation, bed rest, or others are necessary. Likewise, there is no need for routine cesarean section or other labor modifications, except ensuring adequate hydration and normal serum electrolytes. An amniocentesis is unnecessary. There is no constituent of amniotic fluid that is diagnostic of cystic fibrosis. Also, the fetus is at risk for cystic fibrosis only if the father is a carrier. If not, the fetus will be a carrier only. Chorionic villus biopsy can be done to determine whether the fetus has cystic fibrosis if the father carries one of the 150+ alleles for cystic fibrosis or the couple had a previously affected child. It is becoming the standard of care to screen routinely pregnant women for the cystic fibrosis gene. Currently, routine screening will identify approximately 80% of carriers of the cystic fibrosis gene.

• Question 556:

  An 18-month-old boy is brought to the clinic for a checkup. As part of his routine care, a serum lead level is obtained. It is 25 g/mL. Which of the following is the most appropriate next step in his management?

  A. chelation with CaEDTA
  B. chelation with succimer
  C. investigation of his home for lead hazards
  D. reassurance that this level is not a problem
  E. repeating the level in 6 months
  C. investigation of his home for lead hazards

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  Explanation

  The CDC has identified lead poisoning as one of the most common and preventable childhood health problems in the United States. Recent data indicate that undesirable behavioral and cognitive deficits can occur at levels previously thought to be "safe." Screening all children aged 672 months, by questionnaire or blood-lead level, is suggested. Children at greatest risk for lead poisoning include young inner-city children who live in housing constructed before 1960; children living near lead processing smelters, battery recycling plants, or other industries that release lead; or children with siblings or playmates diagnosed with lead poisoning. Eliminating the lead source is the cornerstone of treatment. Chelation therapy generally is reserved for those children with blood-lead levels greater than 45 g/dL.

• Question 557:

  A 2-month-old infant is brought to the emergency department with irritability and lethargy. The parents state that he was well until he rolled off the couch on to the floor yesterday. On examination, he is inconsolable and afebrile. The fontanels are full and tense. He has a generalized tonic-clonic seizure. Which of the following is the most important initial diagnostic study to order?

  A. serum calcium, phosphorus, and magnesium levels
  B. analysis of cerebrospinal fluid (CSF)
  C. cranial computed tomography (CT) scan
  D. serum ammonia level
  E. serum acetaminophen level
  C. cranial computed tomography (CT) scan

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  Explanation

  Though infection must be considered as an etiology, acute trauma is more likely in this scenario. This case represents the classic picture of the shaken baby syndrome which produces intracranial trauma without obvious external findings. This infant is critically ill and lacks preceding illness or constitutional symptoms. The tense fontanels reflect increased intracranial pressure. Acranial CT scan may show diffuse edema or a localized lesion, such as a subdural hemorrhage. Metabolic causes of seizures do not cause increased intracranial pressure. Acetaminophen toxicity does not cause CNS symptoms.

• Question 558:

  A 4-year-old previously healthy but unimmunized boy presents with sudden onset of high fever, inspiratory stridor, and refusal to drink. Of the following causes of inspiratory stridor, which best fits this clinical scenario?

  A. epiglottitis
  B. vascular ring
  C. croup
  D. foreign body aspiration
  E. laryngeal tumor
  A. epiglottitis

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  Explanation

  Croup and epiglottitis have similar presentations but need to be distinguished immediately. Croup usually results from a viral infection of the larynx and epiglottitis from a bacterial (H. influenzae type B) infection of the epiglottis. Children with epiglottitis tend to be toxic in appearance. Croup involves the airway, and epiglottitis involves the airway and the digestive tract. Children with croup usually will swallow and drink. Children with epiglottitis most often will refuse to drink and may even drool as a result of their refusal to swallow saliva. Patients with foreign bodies in their upper airways do not typically have fever. Patients with vascular rings and laryngeal tumors have more gradual onset of symptoms.

• Question 559:

  A young child finds a bat lying on the floor of his room. The child picks it up to show it to his mother, and it bites him on the hand. The bat then escapes, flying out of an open window. Which of the following diseases poses the most serious threat to the child's health?

  A. rabies
  B. lacrosse encephalitis
  C. distemper
  D. tularemia
  E. tetanus
  A. rabies

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  Explanation

  Transmission of rabies virus by a bat bite has been well documented, and in many areas of the country, bats are known to harbor the rabies virus. There are also well-documented cases of human rabies due to viral strains found in bats, but without a good history of being bitten. Therefore, presumptive treatment is recommended in the case of a bite (and in some cases for a possible bite) when the bat cannot be recovered and tested. Lacrosse encephalitis, distemper, and tularemia are not known to be transmitted by bats. Tetanus is unlikely because a child this age has probably been immunized.

• Question 560:

  A50-year-old man is admitted to the hospital with a UGI bleed from acute erosive gastritis, secondary to chronic nonsteroidal anti-inflammatory use. His hematocrit is 28%. With fluid resuscitation, his blood pressure normalizes, but he has a persistent hyperdynamic precordium, tachycardia, and flow murmur on auscultation. He complains of shortness of breath on ambulation. An ECG shows depressed ST-T segments. Which of the following is the next appropriate step in management?

  A. initiation of iron supplementation therapy
  B. supplemental oxygen
  C. continued IV fluid resuscitation
  D. initiation of a calcium channel blocker
  E. blood transfusion
  C. continued IV fluid resuscitation

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  Explanation

  This patient has symptomatic anemia. The decreased oxygen-carrying capacity has resulted in decreased tissue perfusion. The heart attempts to compensate with increased contractility and heart rate, in an attempt to improve cardiac output and oxygen delivery. In this patient, however, this is inadequate and has also placed excess metabolic demands on the myocardium with signs of ischemia. These changes can be ameliorated with a blood transfusion. Iron supplementation is indicated in the treatment of chronic iron- deficiency anemia. Restoration of iron stores and a normal red cell mass usually takes several months. Therefore, it is not appropriate in a patient with symptomatic anemia. Supplemental oxygen will not improve oxygen delivery in a patient with limited oxygen-carrying capacity and compensatory maximum oxygen extraction at the tissue level. IV fluid resuscitation will increase circulating blood volume, resulting in hemodilution and decreased red cell concentration. Calcium channel blockade is indicated for management of myocardial ischemia from primary coronary or myocardial pathology.