USMLE USMLE Certifications USMLE-STEP-3 Questions & Answers

• Question 541:

  A62-year-old male on total parenteral nutrition (TPN) for 2 weeks following development of a postoperative enterocutaneous fistula has developed high, spiking temperatures up to 102.2°F over the last 8 hours. The only abnormal finding on physical examination is erythema and induration around his central line. The most appropriate management is which of the following?

  A. begin broad-spectrum antibiotics and observe for 24 hours

  B. obtain blood cultures through the central line, begin broad-spectrum antibiotics and await culture results

  C. remove catheter, send tip for culture and replace with a new central line over the guide wire

  D. remove catheter, send tip for culture and establish central line at another site

  E. remove catheter, send for culture and establish peripheral intravenous line

  Correct Answer: D Section: (none)

  Explanation:

  A high index of suspicion is warranted for catheter sepsis in any patient who has had a central line for several days and suddenly spikes a high fever. The catheter site may have erythema, induration, tenderness, and purulent discharge extruding from the skin. Often, however, the skin appears normal. Athorough search for other possible sources of fever including pulmonary, intra-abdominal, urinary, and wound infections is always prudent. Catheter sepsis can be life threatening and early intervention is essential. Peripheral and central blood cultures should be obtained and the catheter must be removed promptly. It is contraindicated to replace the catheter over a guide wire because the skin tract is infected. It is not mandatory to treat with antibiotics unless the fever persists or signs of sepsis are present.

• Question 542:

  A50-year-old diabetic man is treated as an outpatient with incision and drainage and oral clindamycin for an abscess and cellulitis of the skin on his back. About a week after completing his antibiotic he develops frequent, watery diarrhea. Which of the following is the most appropriate treatment of this complication?

  A. oral levaquin

  B. intravenous metronidazole

  C. oral vancomycin

  D. oral metronidazole

  E. intravenous vancomycin

  Correct Answer: D Section: (none)

  Explanation:

  Nearly all broad-spectrum antibiotics may result in superinfection of the colon with Clostridium difficile. This anaerobic enteric pathogen produces a toxin that causes necrosis of the colonic mucous membrane resulting in enterocolitis (pseudomembranous colitis). The infection can occur several weeks after the discontinuation of the inciting antibiotic. The presentation varies from mild diarrhea to systemic illness with abdominal pain, fever, and leukocytosis. Severe cases may progress to colonic dilatation and perforation. Lower endoscopy reveals the characteristic yellow pseudomembranes, which represent ulceration and necrosis. The diagnosis is confirmed with either colonic wall biopsy for the organism, or more commonly with identification of the toxin in stool samples. Orally administered metronidazole is the treatment of choice. Oral vancomycin is also effective, but it is reserved for refractory cases due to its side effect profile and expense.

• Question 543:

  A 64-year-old diabetic male undergoes a right hemicolectomy for an adenocarcinoma of the cecum. On the first postoperative night, he becomes tachycardic and is noted to have a temperature of 102.8°F. His surgical incision is tender with erythema and murky discharge.

  Which of the following is the most important intervention?

  A. begin broad-spectrum antibiotics, Tylenol, and a cooling blanket

  B. open the wound and begin hyperbaric oxygen treatment

  C. apply sterile warm compress over the incision and replace dressing

  D. open the wound, send for Gram's stain of the fluid and emergent radical debridement

  E. postoperative fever evaluation including sputum, urine, and blood cultures

  Correct Answer: D Section: (none)

  Explanation:

  Postoperative wound infections usually occur between the fifth and eighth postoperative days. Evidence of a wound infection within the first 24 hours after surgery should alert the physician to the possibility of necrotizing fasciitis. Necrotizing fasciitis is a lifethreatening infection most commonly caused by clostridial myositis and hemolytic streptococcus. In addition to spiking temperature, the patient may be septic with tachycardia, leukocytosis, and hemodynamic instability. On examination of the wound, crepitus (gas in the soft tissue) and a dishwater-appearing effluent may be apparent. Early diagnosis by opening the wound and sending a Gram's stain is critical. The Gram's stain will reveal a mixed flora of ramnegative rods and gram-positive cocci. Although broad-spectrum antibiotics are indicated, definitive treatment requires emergent aggressive debridement of the affected tissues. Hyperbaric oxygen treatment has no role in the acute management of necrotizing fasciitis. Diabetic patients are especially prone to necrotizing fasciitis. Fournier's gangrene is a type of necrotizing fasciitis that affects the groin and perineum. The mortality rate can be as high as 75%.

• Question 544:

  Following an uneventful appendectomy for acute appendicitis, the pathology report reveals the presence of

  a 1 cm carcinoid at the tip of the appendix. The patient has been otherwise asymptomatic.

  What is the most appropriate intervention?

  A. formal right hemicolectomy

  B. partial cecectomy--excision of the base of the cecum at the appendectomy site

  C. no further operative intervention required

  D. total abdominal colectomy with ileorectal anastomosis

  E. partial small bowel resection

  Correct Answer: C Section: (none)

  Explanation:

  Carcinoids are the most common neoplasm of the appendix and arise from Kulchitsky cells, a type of enterochromafin cell. Aside from the appendix, the next most frequent site of involvement is the small bowel followed by the rectum. Appendiceal and rectal carcinoids are almost never associated with carcinoid syndrome unless metastatic disease is present. Small bowel carcinoids are more commonly multifocal, metastatic, and associated with carcinoid syndrome. The majority of appendiceal carcinoids are located at the tip and the extent of surgical resection depends on the size and resulting malignant potential. Lesions less than 1 cm rarely metastasize and therefore require only simple appendectomy as in this question. Lesions greater than 2 cm require a right hemicolectomy due to the high potential for metastasis. Partial small bowel resection is indicated for a carcinoid of the small intestine. Partial cecectomy and total abdominal colectomy are not appropriate options.

• Question 545:

  A patient presents with a 24-hour history of periumbilical pain, now localized to the right lower quadrant. An abdominal CT scan is obtained in the ER, which is shown in Figure.Which of the following is considered a physical sign often associated with this diagnosis?

  

  A. concave and empty right lower quadrant

  B. pain on flexion of the right hip

  C. flank bruising

  D. pain in right lower quadrant with palpation in left lower quadrant

  E. inspiratory arrest while palpating under the right costal margin

  Correct Answer: D Section: (none)

  Explanation: The diagnosis of acute appendicitis can often be made based on the history and physical findings. The sequence of symptoms classically begins with anorexia followed by periumbilical pain that localizes to the right lower quadrant after 612 hours. The onset on nausea and emesis occur after the development of abdominal pain. If the patient has an appetite or if bouts of vomiting begin before the onset of abdominal pain, the diagnosis should be reconsidered. In this patient, the acute appendicitis has progressed to a rupture resulting in a localized right lower quadrant abscess (marked with arrow in Figure below)

  

  The signs of acute appendicitis are also characteristic. On examination, tenderness is often maximal at McBurney's point, located approximately one-third the distance from the anterior superior iliac spine to the umbilicus. Other physical signs include Rovsing's sign (pain initiated in the right lower quadrant upon palpation in the left lower quadrant), Dunphy's sign (increased pain with coughing), the obturator sign (pain on internal rotation of the hip), and the psoas sign (pain during extension of the right hip). Dance's sign (concave and empty right lower quadrant) is associated with ileocecal intussusception. Grey-Turner's sign is bruising of the flanks and may occur in severe, acute pancreatitis due to subcutaneous tracking of inflammatory, peripancreatic exudate along the retroperitoneum. Murphy's sign is defined as inspiratory arrest secondary to pain when palpating under the right costal margin. It is associated with a diagnosis of acute cholecystitis

• Question 546:

  A 49-year-old male presents with crushing substernal pain and rules out for a myocardial infarction. He is noted to have subcutaneous emphysema of the chest and neck and precordial crackles that correlate to his heartbeat but not his respirations Which of the following approaches to management is most appropriate?

  A. This condition should always be managed operatively.

  B. The best diagnostic test is thoracic CT.

  C. Early endoscopy is contraindicated.

  D. Primary surgical repair is the first approach to treatment if the diagnosis is made within 24 hours.

  E. Anticoagulation should be started while the diagnostic workup proceeds.

  Correct Answer: D Section: (none)

  Explanation: "Hamman's crunch" is precordial crackles heard on auscultation that correlate with heart sounds in the setting of mediastinal emphysema and is suggestive of esophageal perforation. When present along with subcutaneous emphysema of the chest and neck, pneumomediastinum from an esophageal perforation is the most likely diagnosis. The most common cause of esophageal perforation is iatrogenic, but it may be spontaneous (Boerhaave's syndrome) or secondary to a malignancy or stricture. Diagnosis is often made after clinical suspicion by endoscopy or a swallow study with water-soluble contrast. If diagnosed early (within 24 hours), a primary repair is the first approach to treatment. Closure is dependent on the amount of infected or necrotic tissue, tension on the anastomosis, etiology of the perforation, and the ability to adequately drain the contaminated areas. Late perforations may be complicated in their management, requiring several procedures or diversion to provide for adequate healing.

• Question 547:

  A 49-year-old male presents with crushing substernal pain and rules out for a myocardial infarction. He is noted to have subcutaneous emphysema of the chest and neck and precordial crackles that correlate to his heartbeat but not his respirations.

  Which of the following is the most likely diagnosis?

  A. spontaneous pneumothorax

  B. esophageal perforation

  C. pericarditis

  D. pneumopericardium

  E. pulmonary embolus

  Correct Answer: B Section: (none)

  Explanation:

  "Hamman's crunch" is precordial crackles heard on auscultation that correlate with heart sounds in the setting of mediastinal emphysema and is suggestive of esophageal perforation. When present along with subcutaneous emphysema of the chest and neck, pneumomediastinum from an esophageal perforation is the most likely diagnosis. The most common cause of esophageal perforation is iatrogenic, but it may be spontaneous (Boerhaave's syndrome) or secondary to a malignancy or stricture. Diagnosis is often made after clinical suspicion by endoscopy or a swallow study with water-soluble contrast. If diagnosed early (within 24 hours), a primary repair is the first approach to treatment. Closure is dependent on the amount of infected or necrotic tissue, tension on the anastomosis, etiology of the perforation, and the ability to adequately drain the contaminated areas. Late perforations may be complicated in their management, requiring several procedures or diversion to provide for adequate healing.

• Question 548:

  Which of the following statements is true regarding Barrett's esophagus?

  A. It is three times more common in women than men.

  B. Most cases are congenital in origin.

  C. The columnar-lined epithelial changes are always in direct continuity with the gastric epithelium.

  D. Surgical antireflux therapy does not necessarily result in regression of the Barrett's changes.

  E. Once the diagnosis of Barrett's esophagus is established, the patient does not need further biopsies on follow-up endoscopy.

  Correct Answer: D Section: (none)

  Explanation:

  Barrett's esophagus is a condition in which the normal stratified squamous esophageal mucosa is replaced by a columnar-lined epithelium. It is often the result of chronic GERD. If

• Question 549:

  A 50-year-old male presents with difficulty swallowing. Esophageal manometry demonstrates absence of peristaltic waves and a nonrelaxing lower esophageal sphincter (LES). Which of the following is the most likely diagnosis?

  A. Barrett's esophagus

  B. diffuse esophageal spasm

  C. achalasia

  D. Plummer-Vinson syndrome

  E. esophageal cancer

  Correct Answer: C Section: (none)

  Explanation:

  Esophageal achalasia is characterized by the findings of aperistalsis/atony and a failure of the LES to relax normally, resulting in esophageal dilatation proximally with a functional obstruction at the LES. Longstanding achalasia results in the characteristic barium swallow finding of a "bird's beak." Iatrogenic or tumor-related elevation of LES pressure can result in a "pseudoachalasia," but should have normal peristaltic patterns on manometry. Patients with Barrett's esophagus may have a "cobblestone" appearance on barium swallow, with normal peristalsis, and do not characteristically demonstrate esophageal dilatation; LES pressures may be normal or low. Finally, patients with Plummer-Vinson syndrome develop cervical dysphagia due to irondeficiency anemia; patients often present with cervical esophageal webs and can be at higher risk for developing esophageal squamous cell carcinoma.

• Question 550:

  A 25-year-old male comes to the ER after a motor vehicle collision, complaining of vague left-sided abdominal pain. After initial evaluation, a CT of the abdomen is obtained as shown in Figure. Which of the following statements is true concerning the injury?

  

  A. Hemodynamically unstable patients can be managed nonoperatively.

  B. Patients should be vaccinated against tetanus before hospital discharge.

  C. Splenic salvage is contraindicated in the presence of other major abdominal injuries.

  D. Pseudomonas aeruginosa is the most frequent organism responsible for postsplenectomy sepsis.

  E. Most patients require operative management.

  Correct Answer: C Section: (none)

  Explanation:

  Because of the risk of postsplenectomy sepsis, attempts should be made for splenic salvage when possible. Most patients are managed nonoperatively. Nonoperative management is contraindicated in the presence of hypotension or persistent bleeding. If patients are treated operatively, attempts are still made at splenic salvage if possible instead of splenectomy. Attempts at splenic salvage are contraindicated in hemodynamically unstable patients or patients with multiple concomitant injuries, as it prolongs the operation and increases blood loss. The risk of postsplenectomy sepsis from encapsulated organisms persists throughout life, but the highest incidence is in the first 2 years following splenectomy. Patients should be vaccinated against Pneumococcus, Meningococcus, and Haemophilus influenzae prior to discharge from the hospital.