USMLE USMLE Certifications USMLE-STEP-3 Questions & Answers

• Question 521:

  A 65-year-old woman complains that she has become increasingly light-headed after playing golf. She also

  has had some cramping type pain in her left arm, which coincides with the episodes. She undergoes

  arteriogram and is found to have a stenotic lesion of her subclavian artery.

  Which of the following is true?

  A. The stenotic lesion is distal to the take off of the vertebral artery.

  B. It is unusual for these patients to have coronary artery disease as well.

  C. The patient's light-headedness is caused by an incomplete Circle of Willis.

  D. The operation of choice for this patient is a carotid-subclavian bypass.

  E. Radial pulses in this patient will be equal bilaterally.

  Correct Answer: D Section: (none)

  Explanation:

  This patient is presenting with subclavian steal syndrome, which is caused by subclavian stenosis proximal to the take off of the verterbral artery. Exertion of the extremity causes blood to be shunted away from the brain to the arm resulting in vertigo or even syncope. These patients usually have diminished radial pulses on the affected side and also have other evidence of atherosclerotic disease. A carotidsubclavian bypass is the operation of choice for these patients.

• Question 522:

  A patient presents to the ED complaining of abdominal pain out of proportion to her examination. Initial vital signs are: BP 70/30, HR 120. The patient does report a prior history of abdominal pain after eating. Which of the following statements regarding this condition is most accurate?

  A. A CT scan which shows superior mesenteric artery (SMA) thrombosis or bowel wall thickening requires an immediate operation.

  B. The most common site of embolic event is the SMA.

  C. Nonocclusive mesenteric ischemia is treated with arterial bypass.

  D. Patients with cardiac arrhythmias arenot at increased risk.

  E. After volume resuscitation, the initial diagnostic study for this patient is esophagogastroduodenoscopy (EGD).

  Correct Answer: B Section: (none)

  Explanation:

  Severe abdominal pain is the hallmark presentation of acute mesenteric ischemia. The pain is often described as being out of proportion to examination. It is most often caused by an embolic event to the SMA. Patients with cardiac arrhythmias are at greater risk for having an embolic event. Nonocclusive mesenteric ischemia is thought to be due to reactive arterial vasoconstriction and is not a surgically correctible disease. CT scan findings of SMA thrombosis or gas in the bowel wall would necessitate emergency surgery.

• Question 523:

  Which of these statements is true in regard to GI hormones?

  A. Vagal activation, antral distension, and antral protein are all stimuli for gastrin release.

  B. Secretin stimulates gastrin.

  C. Secretin is released from the antrum of the stomach.

  D. Cholecystokinin (CCK) release is stimulated by fat in the duodenum and results in release of insulin by the pancreas.

  E. CCK is released by the pancreas and relaxes the sphincter of Oddi.

  Correct Answer: A Section: (none)

  Explanation:

  Gastrin is the humoral mediator of the gastric phase of secretion, and the release of gastrin is stimulated by antral distention, antral protein/ amino acids, and by the vagus itself. Gastrin stimlulates gastric acid secretion, promotes gut motility, and is a trophic factor for gut mucosa. Secretin is released by duodenal mucosal S cells in response to acid and promotes water and bicarbonate secretion from the pancreas. CCK is released in the gut by intestinal mucosal I cells and stimulates emptying of the gallbladder, increases bile flow, and relaxes the sphincter of Oddi. CCK has a structure very similar to gastrin.

• Question 524:

  The family of a patient recently diagnosed with esophageal cancer requests more information regarding the

  disease.

  You tell them which of the following?

  A. The incidence of SCC of the esophagus is rising more rapidly than adenocarcinoma.

  B. Premalignant conditions include caustic esophageal burns, Plummer-Vinson syndrome, and tylosis.

  C. It is more common in women than men.

  D. Smoking is not a risk factor for esophageal cancer.

  E. Barrett's esophagus increases the risk for esophageal SCC.

  Correct Answer: B Section: (none)

  Explanation:

  Esophageal cancer is increasing in incidence in North America, largely due to the rise in incidence of esophageal adenocarcinoma. Premalignant lesions for esophageal cancer include: Barrett's changes, radiation esophagitis, caustic esophageal burns, Plummer-Vinson syndrome, leukoplakia, esophageal diverticula, ectopic gastric mucosa, and tylosis. It is more common in men, and smoking is clearly a risk factor along with alcohol. Barrett's esophagus requires frequent surveillance examinations with biopsies and increases the risk for adenocarcinomas of the esophagus at the gastroesophageal junction.

• Question 525:

  A40-year-old woman presents with epigastric pain and is diagnosed with peptic-ulcer disease. A duodenal ulcer is seen on upper endoscopy.

  How would you counsel her regarding surgical management options?

  A. The ulcer is most likely secondary to a malignancy. Further workup is needed to rule out distant metastases before considering surgery.

  B. Surgery is the most effective first-line therapy.

  C. Recurrence rate of a duodenal ulcer 15 years after vagotomy and a drainage procedure is less than 5% .

  D. Patients operated on for intractability are more prone to developing postgastrectomy symptoms.

  E. Incidence of dumping syndrome is lower after highly selective vagotomy than after truncal vagotomy.

  Correct Answer: E Section: (none)

  Explanation:

  The indications for surgery for duodenal ulcers include intractability, hemorrhage, obstruction, and perforation. Initial management includes dietary and behavior modification, H2 blockade, proton pump inhibitors, and treatment for H. pylori. Duodenal ulcers are rarely secondary to a malignancy and are related to acid production, unlike gastric ulcers, which have a higher incidence of association with malignant processes. Surgical approaches include: vagotomy (truncal, selective, highly selective), vagotomy combined with antrectomy, or subtotal gastrectomy. There are varying rates of perioperative morbidity and effectiveness reported in the literature. Recurrence rates after vagotomy and pyloroplasty alone approach 30%, in long-term followup. The complication of dumping after a highly selective vagotomy is significantly lower than truncal vagotomy. A drainage procedure after highly selective vagotomy is unnecessary, and vagal denervation of the proximal stomach reduces receptive relaxation.

• Question 526:

  A 60-year-old man with hypertension, hyperlipidemia, and peripheral vascular disease requires coronary artery bypass graft surgery.

  Which of the following vessels would be the most appropriate conduit for his coronary artery bypass graft?

  A. left axillary artery

  B. internal mammary arteries

  C. ulnar artery

  D. common femoral vein

  E. femoral artery

  Correct Answer: B Section: (none)

  Explanation:

  Finding a conduit for use in coronary artery bypass grafting can sometimes be a challenge since these patients often have diffuse atherosclerotic disease. The left internal mammary artery is most commonly used. Bilateral internal mammary arteries can be used, however this increases the chances of sternal healing problems. Saphenous vein grafts are used in patients with multivessel disease, although this may not be an option in patients with deep vein thrombosis (DVT), venous insufficiency, or arterial insufficiency to the legs (because they will not heal the harvest wound). Radial arteries, the right gastroepiploic artery, and inferior epigastric arteries have also been used.

• Question 527:

  A45-year-old man undergoes a distal esophagectomy for Barrett's esophagus. During his hospital course, a left chest tube is placed for an effusion. Milky white fluid is found to come out through the tube.

  Which of the following statements is most accurate about this condition?

  A. Diagnosis can be confirmed by checking the lymphocyte count and triglyceride level in the fluid.

  B. This condition requires immediate surgical intervention to repair.

  C. The chest tube should be removed due to the possibility of an iatrogenic source of infection.

  D. Usually found on the right if due to a traumatic source.

  E. The use of TPN is contraindicated until the condition resolves.

  Correct Answer: A Section: (none)

  Explanation: Damage to the thoracic duct can be seen as a complication following distal esophagectomy or any procedure that involves dissection into the cervical region. It is most commonly seen on the left if iatrogenic. Aspiration of an odorless, milky fluid from the chest cavity is diagnostic, although increased lymphocyte counts nd triglyceride levels in the fluid help confirm the diagnosis. Normal chyle flow is around 2 L a day. Therefore, a chylous leak can result in nutritional depletion as well as decreased systemic lymphocytes to fight infection. The first therapy is placement of a chest tube to drain the chyle and to allow for approximation of the lung against the mediastinum. Stopping oral intake and starting total parental nutrition is usually tried for 710 days to see if there is spontaneous resolution of the leak. If conservative measures fail, ligation of the thoracic duct can be performed.

• Question 528:

  A60-year-old woman presents with an abnormal cluster of microcalcifications on a routine mammogram, and undergoes a needle-localized excisional biopsy. The pathology is shown in Figure. When counseling the patient regarding her surgical options, which of the following statements would be correct?

  

  A. Modified radical mastectomy differs from a Halsted mastectomy in that the pectoralis major is spared in the modified radical approach.

  B. Modified radical mastectomy differs from Halsted mastectomy in that an axillary lymphadenectomy is not performed in the modified radical approach.

  C. The anatomic limits of the modified radical mastectomy include the sternum medially and the anterior border of the serratus anterior muscle laterally.

  D. Injury to the thoracodorsal nerve during mastectomy results in a "winged scapula."

  E. Lymphedema occurs mainly as a complication of the Halsted radical mastectomy and should not be seen after modified radical mastectomy.

  Correct Answer: A Section: (none)

  Explanation:

  The Halsted radical mastectomy involves removal of all breast tissue, lymphadenectomy, and removal of the pectoralis major. The modified radical mastectomy preserves the pectoralis major muscle thus decreasing the morbidity of the surgery with the same survival. The modified radical mastectomy does include a lymph node dissection. The anatomic limits of the modified radical mastectomy include the sternum medially, the subclavius muscle superiorly, the inframammary fold inferiorly, and the latissimus dorsi muscle laterally. The surgeon must identify the thoracodorsal nerve and the long thoracic nerve, which innervate the latissimus dorsi muscle and the serratus anterior muscle, respectively. Damage to the long thoracic nerve results in a "winged scapula." After a complete dissection of level I, II, and III lymph nodes, the use of radiation therapy needs to be critically evaluated because of the long-term morbidity of lymphedema.

• Question 529:

  A 56-year-old man comes to the hospital. For the past 5 days he has had colicky abdominal pain, vomiting, abdominal distention, and constipation

  During definitive surgical treatment of the lesion shown on the barium enema, the left ureter is accidentally transected at the level of the pelvic brim. What is the most appropriate management of this complication?

  A. ureteroneocystostomy

  B. left to right ureteroureterostomy

  C. anastomosis of the two cut ends over a "double J" stent

  D. nephrectomy

  E. ligation of the transected ends

  Correct Answer: C Section: (none)

  Explanation: This patient presents with classic symptoms of a bowel obstruction. The diagnosis is often made by a thorough history and physical examination. Following the initial evaluation, an acute abdominal x-ray series should be obtained, which includes supine and erect views of the abdomen. The diagnosis is confirmed with the presence of dilated loops of bowel with the presence of air-fluid levels. These plain films may also suggest the location of the obstruction (small vs. large intestine). Abdominal ultrasonography has limited role in the diagnosis or management of intestinal obstruction. Serum electrolyte determination helps in identifying the electrolyte disturbances that have taken place. Fluid loss needs to be corrected with rehydration, and nasogastric suction helps in decreasing abdominal distention. Upper GI endoscopy would increase distention, and is contraindicated. Antiemetics should not be given until a definitive diagnosis is made, and then only if indicated; promotility agents have little to no role in the management of a patient with bowel obstruction, and may even be contraindicated.

  An annular constricting lesion with overhanging edges is typical of annular carcinoma of the colon. Mechanical small bowel obstruction results in multiple air-fluid levels in distended small bowel loops. Intussusception produces a "corkscrew" appearance on barium enema, and sigmoid volvulus produces a "bird's beak" appearance. In diverticulitis, extravasation of barium outside the lumen of the colon typically is seen.

• Question 530:

  A 56-year-old man comes to the hospital. For the past 5 days he has had colicky abdominal pain, vomiting, abdominal distention, and constipation

  He undergoes barium enema examination. The findings on barium enema, shown in Figure, are most compatible with which of the following diagnoses?

  

  A. mechanical small bowel obstruction

  B. intussusception

  C. volvulus

  D. carcinoma of the colon

  E. diverticulitis

  Correct Answer: D Section: (none)

  Explanation:

  This patient presents with classic symptoms of a bowel obstruction. The diagnosis is often made by a thorough history and physical examination. Following the initial evaluation, an acute abdominal x-ray series should be obtained, which includes supine and erect views of the abdomen. The diagnosis is confirmed with the presence of dilated loops of bowel with the presence of air-fluid levels. These plain films may also suggest the location of the obstruction (small vs. large intestine). Abdominal ultrasonography has limited role in the diagnosis or management of intestinal obstruction. Serum electrolyte determination helps in identifying the electrolyte disturbances that have taken place. Fluid loss needs to be corrected with rehydration, and nasogastric suction helps in decreasing abdominal distention. Upper GI endoscopy would increase distention, and is contraindicated. Antiemetics should not be given until a definitive diagnosis is made, and then only if indicated; promotility agents have little to no role in the management of a patient with bowel obstruction, and may even be contraindicated.

  An annular constricting lesion with overhanging edges is typical of annular carcinoma of the colon. Mechanical small bowel obstruction results in multiple air-fluid levels in distended small bowel loops. Intussusception produces a "corkscrew" appearance on barium enema, and sigmoid volvulus produces a "bird's beak" appearance. In diverticulitis, extravasation of barium outside the lumen of the colon typically is seen.