USMLE USMLE Certifications USMLE-STEP-3 Questions & Answers

• Question 571:

  A 45-year-old man presents with suprapubic tenderness, fevers, and nausea. After a thorough evaluation, he is found to have acute cystitis and bladder stones. Which of the following bacteria is most likely responsible for this infection?

  A. Staphylococcus aureus

  B. Pseudomonas

  C. Escherichia coli

  D. Proteus mirabilis

  E. Klebsiella species

  Correct Answer: D Section: (none)

  Explanation:

  E. coli is the most common culprit for acute cystitis, although it is often caused by enterococci, S. aureus, Klebsiella, Pseudomonas, and Streptococcus epidermis. P. mirabilis can split urea, which results in alkaline urine and precipitation of calcium. Patients with this organism often present with bladder calculi.

• Question 572:

  Which of the following statements is true about primary hyperparathyroidism?

  A. It is associated with chronic renal failure and is the result of hypocalcemia caused by hyperphosphatemia.

  B. Seen most commonly in patients with renal failure who undergo kidney transplantation.

  C. Commonly seen as a result of an adenoma in one of the parathyroid glands.

  D. Most patients present with renal stones, bone pain, or mental status changes.

  E. Is more common in men than women.

  Correct Answer: C Section: (none)

  Explanation:

  Primary hyperparathyroidism is usually the result of a parathyroid adenoma. It can also be associated with multiglandular hyperplasia. Secondary hyperparathyroidism is associated with the hyperphosphatemia, and resultant hypocalcemia, in chronic renal disease. Tertiary hyperparathyroidism is seen after kidney transplant. Most patients (about 80%) with primary hyperparathyroidism are asymptomatic. Symptoms can include renal stones, bone abnormalities, peptic ulcer disease, and mental status changes. It is more common in females, and the incidence increases with age.

• Question 573:

  A patient presents with a new neck mass. On examination, she has a palpable thyroid nodule and a

  palpable cervical lymph node on the same side. Needle biopsy of the thyroid nodule shows amyloid in the

  stroma.

  The treatment for this patient is which of the following?

  A. total thyroidectomy and modified neck dissection

  B. resection of the involved thyroid lobe, isthmusectomy, and removal of the palpable lymph node

  C. total thyroidectomy and radiation therapy

  D. resection of the involved lobe and part of the contralateral lobe, isthmusectomy, and removal of the palpable lymph node

  E. radioactive iodine administration

  Correct Answer: A Section: (none)

  Explanation:

  The needle biopsy revealing amyloid makes the diagnosis of medullary thyroid cancer. Patients often present with a neck mass and palpable lymph nodes (1520%). Because of the aggressive nature of the malignancy and the fact that it is often multicentric, total thyroidectomy is the treatment of choice. Modified radical neck dissection is indicated in patients with palpable lymphadenopathy and in patients with tumors larger than 2 cm (since 60% of these patients will have lymph node involvement). Because medullary carcinoma originates from the thyroid C-cells, they do not respond to thyroxine or radioactive iodine therapy.

• Question 574:

  A 45-year-old woman undergoes an uncomplicated thyroidectomy for a goiter. Later that night, she becomes agitated and complains of difficulty breathing. The surgeon notices some neck swelling at the incision site, but the dressing is clean.

  What should the next step be?

  A. start oxygen by nasal cannula

  B. check STAT serum calcium level

  C. endotracheal intubation to protect her airway

  D. open the incision

  E. administer propranolol and morphine

  Correct Answer: D Section: (none)

  Explanation:

  One of the most feared complications of neck surgery is postoperative hemorrhage causing airway compromise. Any patient with neck swelling and dyspnea must be assessed for this emergently. The treatment is to immediately open up the neck wound to release the hematoma and relieve the tracheal compression.

• Question 575:

  A 22-year-old male presents complaining of a 1-month history of progressive dysphagia. He reports occasional regurgitation of undigested food at night. His past medical history is noncontributory. The condition has worsened to the point that he is on a liquid diet. A contrast swallow study is shown in Figure. What is the best treatment for this patient?

  

  A. proton pump inhibitors

  B. referral to a surgeon for a Nissen fundoplication

  C. calcium channel blockers

  D. serial esophageal sphincter dilations

  E. referral to a surgeon for esophagomyotomy

  Correct Answer: E Section: (none)

  Explanation:

  This patient has achalasia. This disorder is defined by a nonrelaxing lower esophageal sphincter (LES) and decreased peristalsis of the esophageal body. The "bird's beak" deformity is a classic sign with a dilated esophagus which tapers to a small area at the LES. Esophagomyotomy is the treatment of choice for longstanding disease. Serial botox injections and dilations can be used early in the disease process, however their long-term results are inferior to myotomy. Proton pump inhibitors can be used for gastroesophageal reflux disease (GERD). A Nissen fundoplication is also a treatment for GERD. Calcium channel blockers are sometimes used to treat other esophageal motility disorders.

• Question 576:

  A75-year-old man undergoes a right colectomy for stage 3 colon cancer. He has a history of emphysema

  requiring chronic steroid use. He also has diabetes and coronary heart disease. On postoperative day 2,

  the surgeon is called because the patient acutely began to have a large amount of pinkish, serous drainage

  from the wound.

  There is no evidence of infection. Which of the following factors probably contributed to this complication?

  A. the surgeon used a running stitch to close the fascia instead of interrupted sutures

  B. coronary artery disease

  C. early mobilization of patient

  D. aggressive abdominal examination performed on postoperative day 1 by a medical student

  E. pulmonary disease

  Correct Answer: E Section: (none)

  Explanation: Dehiscence refers to a separation of the fascial layer. Evisceration is when peritoneal contents extrude through the fascial separation. Malnutrition, obesity, diabetes, uremia, malignancy, immunologic abnormalities, steroid use, infection, and coughing which increases intraabdominal pressures are all factors that increase the risk of wound dehiscence. Technical factors are also very important in preventing the dehiscence, but there is no proof that interrupted sutures are better than a running stitch for fascial closure

• Question 577:

  A50-year-old man undergoes a sigmoid colectomy and colostomy for perforated diverticulitis of the midsigmoid colon. The surgeon reports a difficult dissection in the pelvis secondary to adhesions of the sigmoid colon to the abdominal wall. On postoperative day 1, the patient reports appropriate abdominal pain. His pulse is 100 and BP 120/60. He has made 400 mL of urine over the past 8 hours. The urine in the Foley bag is blood-tinged.

  He reports no problems with his urination preoperatively. What is the appropriate management?

  A. Remove the Foley catheter. The irritation of the catheter is probably causing the hematuria.

  B. Increase his IV fluids and add bicarbonate in case this is rhabdomyolysis.

  C. Start antibiotics for a urinary tract infection.

  D. Order an intravenous pyelogram to assess for ureteral injury.

  E. Send a prostate-specific antigen (PSA) to screen for a prostatic process.

  Correct Answer: D Section: (none)

  Explanation:

  Ureteral injuries are a well-known complication of pelvic surgery. The risk is greatly increased in the setting of inflammation, which can make the ureters difficult to identify. Intravenous pyelogram is a sensitive test for injury. CT scan and retrograde pyelogram are also diagnostic options. Injuries identified early are usually amenable to primary surgical repair, making early diagnosis essential. Delayed recognition usually results in a staged repair requiring urinary diversion with percutaneous nephrostomy tubes.

• Question 578:

  A 45-year-old male receives a cadaveric liver transplant for alcoholic cirrhosis. Postoperatively, the patient is taken to the surgical intensive care unit (SICU). There is concern for primary nonfunction of the allograft.

  Which of the following is a sign of this?

  A. coagulopathy with an INR of 2

  B. normalizing albumin level

  C. hyperglycemia requiring an insulin drip

  D. initial rise of transaminases

  E. high urine output

  Correct Answer: A Section: (none)

  Explanation: Early clinical decline in a transplant patient is concerning for primary organ failure. This can be related to donor issues, technical issues, or donor organ ischemia. Signs of liver dysfunction include hypoglycemia (as the liver is unable to perform gluconeogenesis), coagulopathy with elevated prothrombin times, elevated ammonia levels, acid-base changes (unable to clear lactate via the Cori cycle), hyperkalemia, and oliguria. All liver transplant patients have an initial rise in transaminases which should decrease over the first 48 hours.

• Question 579:

  A 45-year-old male was involved in a motor vehicle collision. He was a restrained passenger in a high speed, head-on collision with a death at the scene. He is brought to the ED unresponsive with a pulse of 140, a BP of 70/30, and a SpO2 of 80%. He has multiple facial lacerations, a dilated right pupil, a contusion on his chest, and a distended abdomen. The medic team has placed two large-bore IVs and given him 2 L of lactated Ringer's solution.

  The initial step in the care of this patient is:

  A. Given the mechanism, low oxygen saturation, and the presence of a contusion on his chest, the patient likely has a pneumothorax. A chest tube should be placed immediately.

  B. The patient should be taken to the OR immediately for laparotomy since he is hemodynamically unstable with abdominal distention indicating an abdominal source of life-threatening hemorrhage.

  C. The patient should be intubated using in-line traction to protect his cervical spine before continuing the assessment.

  D. Because of the facial lacerations, there is a possibility of facial fractures making endotracheal intubation risky. An emergent cricothyroidotomy should be performed.

  E. A central line should be placed immediately to continue the resuscitation.

  Correct Answer: C Section: (none)

  Explanation:

  The first step in any trauma assessment is the primary survey. This consists of: A--airway maintenance B--breathing and ventilation C--circulation D--disability/neurologic status E--exposure/environment The first priority in any trauma patient is to establish an airway. In an unconscious patient with decreased saturations, endotracheal intubation is indicated. While facial lacerations may indicate fractures, these patients can often be successfully orally intubated. This should be attempted first, but if this technique is unsuccessful, a cricothyroidotomy should be performed to secure the airway. Once an airway has been established, you can address breathing/ ventilation by auscultating breath sounds and evaluating for end-tidal CO2 using a capnometer. It is at this point where a life-threatening tension pneumothorax can be identified and treated. The next step is to evaluate the circulation. This includes getting adequate intravenous access. The patient described has two large-bore IVs, which should be sufficient for the initial resuscitation. Central venous access is indicated only if adequate access cannot be established peripherally. It is here that evaluation for intra-abdominal hemorrhage can be conducted using ultrasound or diagnostic peritoneal lavage.

• Question 580:

  Which of the following is a contraindication to sentinel lymph node biopsy in breast cancer?

  A. clinically negative axillary examination

  B. multicentric disease

  C. lesion under the nipple

  D. history of previous breast biopsy

  E. patient preference for breast conservation

  Correct Answer: B Section: (none)

  Explanation:

  Sentinel lymph node biopsy offers an alternative to full axillary dissection as a diagnostic tool in breast cancer with clinically negative axillary lymph nodes. Patients are injected with technetium-labeled sulfur colloid and isosulfan blue dye. A gamma probe is used along with the visual cues of the blue dye to identify the "sentinel node." The theory is that if this node is negative for malignancy, the rest of the axilla will be negative as well. This spares these patients from an unnecessary axillary lymph node dissection and the morbidity that it entails. Patients with a positive sentinel lymph node require further therapy. Contraindications to the procedure include palpable axillary lymph nodes (because the diagnosis of axillary metastasis is apparent), multicentric disease, and a history of reaction to the blue dye (anaphylaxis and urticaria have been reported). If the lesion is very close to the axilla, there may be too much background radiotracer activity to discern the sentinel node. Lesions under the nipple are quite amenable to this procedure. There are several studies showing that the accuracy and success of this technique is related to surgeon experience. Surgeons are required to perform 2030 procedures with some supervision or confirmation of results before relying completely on sentinel node biopsy