USMLE USMLE Certifications USMLE-STEP-3 Questions & Answers

• Question 551:

  Which of the following is characteristic of Hirschsprung's disease?

  A. Constipation is the most frequent presenting feature.

  B. Severity of the symptoms corresponds with the extent of bowel involvement.

  C. Acetylcholinesterase activity is decreased in the aganglionic segment.

  D. The proximal colon is most commonly affected.

  E. It presents most commonly in young adults.

  Correct Answer: A Section: (none)

  Explanation:

  Although constipation is the most common presenting feature of Hirschsprung's disease, some patients suffer from diarrhea. The severity of symptoms does not correlate well with the extent of bowel involvement. Enterocolitis, a major cause of death, requires vigorous treatment. This complication can occur even after removal of the aganglionic segment of the bowel. Increased acetylcholinesterase activity has been noted in the serum, affected aganglionic bowel, and erythrocytes of afflicted persons. Eighty percent of affected infants are male.

• Question 552:

  A 25-year-old male presents to your office for evaluation of a testicular mass that he found in the shower. On examination, his left testicle is larger than his right with a firm palpable mass. Ascrotal ultrasound confirms the presence of a solitary intraparenchymal testicular mass. The most likely diagnosis in this patient is which of the following?

  A. benign fibroma

  B. epididymitis

  C. seminoma

  D. teratocarcinoma

  E. androblastoma

  Correct Answer: C Section: (none)

  Explanation:

  Testicular cancer is the most common malignancy in men between the ages of 15 and 35. It typically presents as unilateral scrotal swelling. On examination, it is important to distinguish intraparenchymal masses (usually malignant) from extraparenchymal masses (usually benign). This is easily done with scrotal ultrasound. Upon the diagnosis of an intraparenchymal testicular mass, a staging CT scan of the chest, abdomen, and pelvis should be obtained. It is reasonable to evaluate the serum levels of beta-HCG and AFP as they may be elevated in 8085% of patients with nonseminomatous germ cell tumors. LDH, on the other hand, can be elevated in patients with seminomas and can be of prognostic significance. Finally, if elevated, these serum markers can serve as a means to monitor the presence of residual disease and should be measured after resection of the tumor. Additionally, the mass should be excised in order to establish a histologic diagnosis. Aradical orchiectomy should be performed from an inguinal approach. Less invasive approaches such as biopsies or a scrotal approach to the tumor should be avoided as they can alter the lymphatic drainage and potentially adversely affect overall outcomes

• Question 553:

  A 25-year-old male presents to your office for evaluation of a testicular mass that he found in the shower. On examination, his left testicle is larger than his right with a firm palpable mass. Ascrotal ultrasound confirms the presence of a solitary intraparenchymal testicular mass. Further management of his condition would include which of the following?

  A. close observation and repeat ultrasound in 3 months

  B. serum beta-human chorionic gonadotropin (HCG), alpha-fetoprotein (AFP), and lactate dehydrogenase (LDH)

  C. fine needle aspiration to determine if the mass is malignant

  D. transscrotal orchiectomy

  E. a 2-week course of antibiotics with follow-up clinical examination after completion

  Correct Answer: B Section: (none)

  Explanation: Testicular cancer is the most common malignancy in men between the ages of 15 and 35. It typically presents as unilateral scrotal swelling. On examination, it is important to distinguish intraparenchymal masses (usually malignant) from extraparenchymal masses (usually benign). This is easily done with scrotal ultrasound. Upon the diagnosis of an intraparenchymal testicular mass, a staging CT scan of the chest, abdomen, and pelvis should be obtained. It is reasonable to evaluate the serum levels of beta-HCG and AFP as they may be elevated in 8085% of patients with nonseminomatous germ cell tumors. LDH, on the other hand, can be elevated in patients with seminomas and can be of prognostic significance. Finally, if elevated, these serum markers can serve as a means to monitor the presence of residual disease and should be measured after resection of the tumor. Additionally, the mass should be excised in order to establish a histologic diagnosis. Aradical orchiectomy should be performed from an inguinal approach. Less invasive approaches such as biopsies or a scrotal approach to the tumor should be avoided as they can alter the lymphatic drainage and potentially adversely affect overall outcomes

• Question 554:

  Apatient is operated on with the presumptive diagnosis of acute appendicitis. However, at operation, the appendix and cecum are found to be normal. The terminal ileum though is red, edematous, and thickened with creeping of the mesenteric fat onto the ileum for a distance of approximately 30 cm. There is no dilation of the bowel proximal to the area of inflammation. The remainder of the small bowel is normal.

  What is the appropriate operative procedure?

  A. closure of the abdomen

  B. appendectomy

  C. ileostomy proximal to the area of involvement

  D. side-to-side ileotransverse colostomy

  E. right hemicolectomy

  Correct Answer: B Section: (none)

  Explanation:

  From the description, the diagnosis in this patient is acute regional enteritis. The incidental finding of regional enteritis in patients operated on for the presumed diagnosis of acute appendicitis is treated medically unless there is proximal obstruction. The risk of operating on patients with regional enteritis is the formation of a fistula and/or abscess, especially if the area to be resected is involved with the disease process. However, if the cecum and the appendix are not involved, it is advisable to perform an appendectomy. In this instance, it would be safe and eliminate acute appendicitis from the differential if his symptoms recurred.

• Question 555:

  Gastrin secretion is enhanced by which of the following?

  A. antral distention

  B. antral acidification

  C. presence of fat in the antrum

  D. sympathetic nerve stimulation

  E. duodenal acidification

  Correct Answer: A Section: (none)

  Explanation:

  Gastrin secretion is increased by vagal stimulation, antral distention, and by the presence of protein in the antrum. Antral acidification (pH = 1.5) decreases gastrin secretion by a feedback mechanism. The same is true with duodenal acidification.

• Question 556:

  A 50-year-old man comes to the emergency room (ER) with a history of vomiting of 3 days' duration. His past history reveals that for approximately 20 years he has been experiencing epigastric pain that lasts for 23 weeks during spring and autumn. He remembers getting relief from pain by taking milk and antacids. Physical examination showed a fullness in the epigastric area with visible peristalsis, absence of tenderness, and normal active bowel sounds. What is the most likely diagnosis?

  Which of the following metabolic abnormalities are typically found in the above patient?

  A. decreased antidiuretic hormone

  B. hypercalcemia

  C. hypokalemia

  D. hyperchloremia

  E. decreased aldosterone secretion

  Correct Answer: C Section: (none)

  Explanation: In a patient who is known to have had symptoms of peptic ulcer disease for many years and presents with nausea and vomiting, one should consider gastric outlet obstruction. The bstruction can be the result of an exacerbation of the ulcer and subsequent edema or it can be secondary to scar tissue formation. These patients typically describe the sensation of epigastric fullness and demonstrate visible peristalsis going from left to right. A succussion splash may be audible. The history of periodicity and pain relief by taking antacids also favors a diagnosis of previous peptic ulcer disease. Patients with an umbilical hernia will have a mass in the region of the umbilicus. Patients with acute cholecystitis usually present with the sudden onset of pain, radiating to the back, with fever and chills. Volvulus of the sigmoid colon presents with constipation and abdominal distention but vomiting is a late feature. Small bowel obstruction would be associated with a history of colicky abdominal pain, nausea, and vomiting. Additionally, patients with small bowel obstruction usually have hyperactive highpitched bowel sounds on examination

• Question 557:

  A 50-year-old man comes to the emergency room (ER) with a history of vomiting of 3 days' duration. His past history reveals that for approximately 20 years he has been experiencing epigastric pain that lasts for 23 weeks during spring and autumn. He remembers getting relief from pain by taking milk and antacids. Physical examination showed fullness in the epigastric area with visible peristalsis, absence of tenderness, and normal active bowel sounds.

  What is the most likely diagnosis?

  A. gastric outlet obstruction

  B. small bowel obstruction

  C. volvulus of the colon

  D. incarcerated umbilical hernia

  E. cholecystitis

  Correct Answer: A Section: (none)

  Explanation:

  In a patient who is known to have had symptoms of peptic ulcer disease for many years and presents with nausea and vomiting, one should consider gastric outlet obstruction. The bstruction can be the result of an exacerbation of the ulcer and subsequent edema or it can be secondary to scar tissue formation. These patients typically describe the sensation of epigastric fullness and demonstrate visible peristalsis going from left to right. A succussion splash may be audible. The history of periodicity and pain relief by taking antacids also favors a diagnosis of previous peptic ulcer disease. Patients with an umbilical hernia will have a mass in the region of the umbilicus. Patients with acute cholecystitis usually present with the sudden onset of pain, radiating to the back, with fever and chills. Volvulus of the sigmoid colon presents with constipation and abdominal distention but vomiting is a late feature. Small bowel obstruction would be associated with a history of colicky abdominal pain, nausea, and vomiting. Additionally, patients with small bowel obstruction usually have hyperactive highpitched bowel sounds on examination.

• Question 558:

  A38-year-old man, previously in good health, suddenly develops severe abdominal pain radiating from the left loin to the groin and associated with nausea, perspiration, and frequent urination. He is restless, tossing in bed, but has no abnormal findings. The most likely diagnosis is which of the following?

  A. herpes zoster

  B. left ureteral calculus

  C. sigmoid diverticulitis

  D. torsion of the left testicle

  E. retroperitoneal hemorrhage

  Correct Answer: B Section: (none)

  Explanation: Contraction of hollow organs against obstruction or excessive contraction causes colic. Typical ureteral colic is severe, sudden in onset, radiates from the loin to the groin, and is associated with an urge to urinate. Blood clots and calculi in the ureter can cause colic, the latter being more common. Urine examination demonstrates macroscopic or microscopic hematuria

• Question 559:

  Avascular necrosis is most likely to occur in fracture dislocations involving which of the following?

  A. the femoral head

  B. the shaft of the femur

  C. the shaft of the humerus

  D. the scapula

  E. the clavicle

  Correct Answer: A Section: (none)

  Explanation:

  Avascular necrosis occurs following a fracture when the blood supply to a bone fragment is disrupted. The femoral head, humeral head, scaphoid, and talus are particularly vulnerable to this complication because of their precarious blood supply. A dense appearance of the bone on x-ray is a diagnostic clue. Radioisotope scanning can detect avascular necrosis at an earlier stage than is possible with roentgenography.

• Question 560:

  Which of the following is the most common site for a gastrinoma?

  A. gastric antrum

  B. duodenum

  C. pancreas

  D. spleen

  E. gallbladder

  Correct Answer: C Section: (none)

  Explanation:

  A gastrinoma, a gastrin-secreting tumor, produces Zollinger-Ellison syndrome, which is associated with markedly elevated gastric acid secretion and ulcer disease of the upper GI tract. The most common location for these tumors is the pancreas. However, they can be found in the gastric antrum, duodenum, spleen, and ovary. Removal of the gastrinoma can result in a cure. Athorough search must be made at the time of surgical exploration to locate the tumor, which in early stages will be small. The gastrinoma triangle, where 90% of gastrinomas are located, is defined as the area between the junction of the cystic and common bile ducts, the junction of the second and third portions of the duodenum, and the junction of the pancreatic neck and body