USMLE USMLE Certifications USMLE-STEP-3 Questions & Answers

• Question 481:

  A42-year-old male with extensive Crohn's disease undergoes a near complete resection of the ileum. Adeficiency of which of the following vitamin is likely to result?

  A. niacin

  B. thiamine

  C. vitamin B12

  D. vitamin C

  E. vitamin B6

  Correct Answer: C Section: (none)

  Explanation:

  The distal small bowel (ileum) is the site of absorption of fat-soluble vitamins (vitamins A, D, E, and K) as well as vitamin B12. Vitamin B12 binds with intrinsic factor, a glycoprotein secreted from parietal cells of the gastric fundus and body. Specific receptors in the terminal ileum take up the B12 intrinsic factor complex. Vitamin B12 deficiency leads to megaloblastic anemia. The patient will require monthly vitamin B12 injections

• Question 482:

  Several days following an uneventful laparoscopic cholecystectomy, the pathology report reveals gallbladder cancer that is invasive into the submucosa of the specimen. The most appropriate management is which of the following?

  A. observation and close follow-up

  B. chemotherapy with a 5-fluorouracil (5-FU)-based regimen

  C. laparotomy with 23 cm wedge resection of the gallbladder liver bed

  D. laparotomy with 23 cm wedge resection of the gallbladder liver bed and regional lymphadenectomy including the portal and hepatic nodal basins

  E. radiation to the gallbladder liver bed

  Correct Answer: A Section: (none)

  Explanation:

  Carcinoma of the gallbladder accounts for 24% of GI malignancies. Fewer than 1% of patients undergoing biliary tract operations have carcinoma either as an anticipated diagnosis or as an incidental finding. The calcified "porcelain" gallbladder is associated with a 20% incidence of gallbladder carcinoma. Signs and symptoms of carcinoma of the gallbladder are generally indistinguishable from those associated with cholecystitis and cholelithiasis. They include abdominal discomfort, right upper quadrant pain, nausea, and vomiting. Most long-term survivors are patients who underwent cholecystectomy for cholelithiasis and in whom the malignancy was an incidental finding on the pathology report. The management of these patients is based on the depth of tumor penetration into the wall of the gallbladder

• Question 483:

  Which of the following is the most appropriate treatment for a 32-year-old male with a toxic nodular goiter and compressive airway symptoms?

  A. radioactive iodine therapy

  B. propranolol

  C. propylthiouracil

  D. Lugol's solution

  E. total lobectomy

  Correct Answer: E Section: (none)

  Explanation:

  Toxic nodular goiter, also known as Plummer's disease, is a consequence of one or more thyroid nodules secreting inappropriately high levels of thyroid hormone independently of thyroid-stimulating hormone (TSH) control. Hyperthyroidism in patients with toxic nodular goiter is milder than in those with Graves' disease, and the condition is not accompanied by extrathyroidal manifestations such as ophthalmopathy, pretibial myxedema, vitiligo, or thyroid acropathy. Patients with toxic multinodular goiter are older at presentation than those with Graves' disease. The thyroid gland characteristically has one or more nodules on palpation. Local symptoms of compression, such as dysphagia and dyspnea, may occur. The diagnosis is suggested by a thorough history and physical examination and confirmed by documenting suppressed serum TSH level and raised serum thyroid hormone level.

• Question 484:

  You are asked to see a 64-year-old man with left lower quadrant abdominal pain that was admitted to the medicine service after a CT scan demonstrated diverticulitis of the sigmoid colon. There was no evidence for gross perforation and no abscess was identified. He had been admitted 6 months ago for the same problem and had an uneventful recovery. Which treatment do you recommend?

  A. antibiotics only

  B. antibiotics and sigmoidectomy prior to discharge

  C. emergent sigmoidectomy

  D. antibiotics and sigmoidectomy 12 weeks after discharge

  E. antibiotics, interval colonoscopy, and subsequent sigmoidectomy

  Correct Answer: E Section: (none)

  Explanation:

  Diverticulitis is categorized based on its complications. Uncomplicated diverticulitis is defined as inflammation of colonic diverticuli that does not involve free intraperitoneal perforation, abscess formation, fistula formation, or colonic obstruction. This entity can be managed as an outpatient but may require inpatient admission if the pain is severe. The treatment of choice is broad-spectrum antibiotics. The majority of patients will respond well to this intervention. However, as the incidence of recurrence increases the rate of complications also rises. Therefore, it is recommended that surgical resection be performed after the second episode of diverticulitis. Prior to the operative intervention, it is important to rule out the presence of cancer. A colonoscopy should be performed after resolution of the inflammation and prior to surgical resection. It is much more sensitive than a barium enema. The operation is typically delayed until 46 weeks following discharge from the hospital. This provides adequate time for resolution of the inflammation and enables an adequate workup, which includes a colonoscopy.

• Question 485:

  You had previously seen a 24-year-old male in your office for evaluation of a suspicious looking mole. He had undergone a punch biopsy, which demonstrated a melanoma. He has no prior history of skin cancer, no family history of skin cancer, nor any history of blistering sunburns. Which of the following results in the pathology report are most predictive of outcome?

  A. size of the melanoma

  B. color of the melanoma

  C. depth of the melanoma

  D. presence of ulceration

  E. site of the melanoma

  Correct Answer: C Section: (none)

  Explanation: When assessing the prognosis for a patient diagnosed with melanoma, there are many factors that are involved. Tumor thickness, the presence of ulceration, the location of the lesion, the age of the patient, and the gender can all contribute. The most predictive factor is the tumor thickness. There are two measurement systems that have been developed to classify melanoma. The Clark level refers to the depth of invasion of the melanoma in terms of the anatomical layers of the skin. A second system, known as the Breslow depth, simply measures the overall tumor thickness in millimeters. Since the Breslow depth is more reproducible among pathologists, it has proven to be more accurate in the prediction of outcomes.

• Question 486:

  A 52-year-old female has been referred to you for consultation following a core biopsy of an area of calcifications seen on a screening mammogram. She has no family history of breast or ovarian cancer. She has not been taking hormone replacement therapy and has no reproductive risk factors. On physical examination, there is no palpable mass. The core biopsy results demonstrate atypical ductal hyperplasia. What should be the next step in her treatment?

  A. close observation with semiannual mammograms and clinical examinations

  B. treatment with tamoxifen for 5 years

  C. needle localized excisional biopsy

  D. unilateral mastectomy

  E. bilateral mastectomy

  Correct Answer: C Section: (none)

  Explanation:

  The management of a breast lesion has become more complex as our knowledge regarding breast cancer development and treatment has continued to grow. The gold standard for evaluation of a suspicious lesion on mammogram is a core needle biopsy. This can be performed on palpable lesions directly, but can also be used on nonpalpable lesions using ultrasound or stereotactic guidance. A diagnosis of atypical ductal hyperplasia cannot be established on core biopsy alone. Studies have demonstrated that nearly 20% of patients with this diagnosis on core biopsy go on to have evidence of ductal carcinoma in situ or invasive ductal carcinoma after excisional biopsy. As such, if a core biopsy demonstrates evidence for atypical ductal hyperplasia, the standard of care is to proceed with an excisional biopsy to establish the diagnosis. Once this diagnosis has been confirmed, management decisions can be made including close observation with frequent screening mammograms, chemoprevention with tamoxifen, or prophylactic bilateral mastectomy.A unilateral mastectomy is not an option as a diagnosis of atypical ductal hyperplasia increases the risk of breast cancer in both breasts

• Question 487:

  You are seeing a 48-year-old female in followup in your clinic. She originally presented for evaluation of a suspicious nonpalpable lesion in her right breast that was seen on her annual mammogram. A stereotactic core biopsy was done. She now returns to your office to review the results of the pathology report that confirms the presence of lobular carcinoma in situ (LCIS).

  How do you counsel her at this time?

  A. Tamoxifen can prevent this cancer from spreading but may increase your risk of developing cancer in the other breast.

  B. You can consider nonoperative treatment with close observation, annual mammograms, and semiannual clinical examinations.

  C. The recommended treatment is a right breast mastectomy.

  D. Further staging workup at this time will include a chest x-ray and bone scan.

  E. Because you are at such high risk for future cancers, bilateral mastectomies should be performed to prevent this from happening.

  Correct Answer: B Section: (none)

  Explanation:

  LCIS is a benign diagnosis and alone does not have a risk of progression to an invasive cancer. However, a diagnosis of LCIS does increase the risk for development of future breast cancer at a rate of about 1% per year. It is important to remember that the risk is increased for both breasts. It has been shown that chemoprevention with tamoxifen can decrease the incidence of breast cancer by 49%. It is also sufficient to follow this population closely with annual mammograms and semiannual clinical examinations. Prophylactic bilateral mastectomies are an option and result in a 90% decrease in the risk of subsequent breast cancer. Since a diagnosis of LCIS increases the risk of cancer in both breasts, a mastectomy of the affected side is insufficient treatment

• Question 488:

  You are asked to see a 74-year-old man who has been admitted for evaluation of abdominal pain. During his workup, he was found to have hemoccult positive stool and a CT scan that was concerning for a mass in his sigmoid colon.

  Which should be the next step in his treatment?

  A. cardiology consultation for preoperative clearance

  B. contrast enema to evaluate the lesion

  C. colonoscopy to biopsy the mass and rule out synchronous lesions

  D. sigmoidectomy to resect the mass and obtain mesenteric lymph nodes for staging

  E. positron emission tomography (PET) scan to determine if the lesion is cancerous

  Correct Answer: C Section: (none)

  Explanation:

  In the workup of a lesion identified within the colon, the gold standard for diagnosis is colonoscopy. Colonoscopy allows for biopsy of the tissue to establish a diagnosis of cancer prior to removing the mass. Furthermore, it also enables examination of the rest of the colon to rule out synchronous lesions. Barium enemas continue to have a role in diagnosis, but are more useful identifying the level of the lesion particularly in the setting of obstruction. You would not proceed straight to surgical resection unless the patient presented with an obstruction. Finally, PET scans have no role in the diagnosis of colon cancer

• Question 489:

  You have been called to the ER to evaluate a 58-year-old female who presented to the hospital for evaluation of a painful left foot. She noticed the pain when she awoke in the morning. She has a history of painful calf muscles when she walks. On your examination, you notice that she has an irregular heart beat, and that she has no palpable pulses and no audible Doppler signals in her left foot. It is cool to the touch and she has some decreased sensation ather toes. Which of the following is the next best step in this patient's management?

  A. an echocardiogram looking for atrial thrombus

  B. initiation of a heparin infusion

  C. duplex imaging of her arterial vessels in her left leg looking for acute occlusion

  D. aortogram with left lower extremity runoff to determine the level of the vascular occlusion

  E. initiate infusion of thrombolytics to dissolve the clot

  Correct Answer: B Section: (none)

  Explanation:

  Acute arterial occlusion is a surgical emergency. However, the most important intervention is immediate heparinization. The infusion of heparin will help prevent extension of the clot. Furthermore, it will help to keep collateral vessels open. If the patient is stable enough to undergo operative intervention, a catheter embolectomy would be the procedure of choice. Physical examination findings including vascular examination and level of temperature change and altered sensation can help identify the level of the occlusion prior to operative intervention. Duplex ultrasound is not necessary to isolate the occlusion. Arteriograms are more useful in the OR following the embolectomy. Finally, if small vessel occlusion occurs, catheter-directed thrombolytics can help restore distal perfusion. Once perfusion to the threatened limb has been restored, the workup to identify the thromboembolic source should be obtained. Typical sources for emboli include atrial thrombus, valvular disease, aortic aneurysms, or iliac artery atherosclerotic disease.

• Question 490:

  You are called to the ER to assist with a series of trauma patients who arrived following a multiple vehicle accident. You are assigned to a 22-year-old male who was an unrestrained driver involved in a head-on collision. After you confirm the presence of an adequate airway and equal breath sounds bilaterally, you address his hypotension and tachycardia by giving 2 L of lactated Ringer's solution. His pulse remains elevated at 130 and his blood pressure is 92/55. His pelvic x-ray returns and demonstrates a widening of the pubic symphysis. In addition to continued fluid resuscitation, what is your next step in management?

  A. reduce the pelvic volume with a sheet or pneumatic compression garment

  B. exploratory laparotomy to isolate and control the hemorrhage

  C. CT scan to evaluate for other source of hemorrhage

  D. angiography to embolize pelvic vasculature E. obtain additional pelvic x-rays for preoperative planning

  Correct Answer: A Section: (none)

  Explanation:

  The x-ray described demonstrates an open book pelvic fracture. This type of injury can often be associated with significant hemorrhage. It is most commonly seen in frontal impacts involving anterior-posterior compression. The majority of the bleeding occurs from the tearing of pelvic veins in the posterior of the pelvis. The initial treatment for open book pelvic fractures is to reduce the pelvic volume to decrease the amount of hemorrhage. In the trauma bay, this can easily be accomplished by wrapping a sheet around the superior iliac crests and twisting the sheet tight using a dowel or by applying the pneumatic compression garment. These are useful techniques in the short term, but definitive treatment will be necessary. This involves formal repair of the pelvis with external fixation or open reduction and internal fixation. If hemorrhage persists despite reduction of the pelvic fracture, pelvic angiography would be the next step in the treatment algorithm to attempt to identify the source of the hemorrhage and embolize the vessel. Given the difficulty of identifying a bleeding vessel in an expanding pelvic hematoma, exploratory laparotomy is not recommended. Finally, an unstable patient should never be transported for imaging studies.