USMLE USMLE Certifications USMLE-STEP-3 Questions & Answers

• Question 471:

  While working in the emergency room you see a 14-month-old boy brought in with apparent leg pain. His parents tell you that he has recently been learning to walk and that this injury is the result of a fall. You obtain the following x-ray What is the mechanism that likely resulted in this injury?

  

  A. twisting on a planted leg while learning to walk

  B. forced rotation of the leg by another person (child abuse)

  C. fall from a piece of furniture or stairs

  D. inversion of the ankle

  E. motor vehicle accident while not restrained in a car seat

  Correct Answer: A Section: (none)

  Explanation:

  The x-ray provided shows a nondisplaced spiral fracture of the distal tibia. This is also known as a toddler's fracture. This fracture can occur when the toddler begins to walk and twists on a planted leg. This torque can result in a spiral fracture of the planted tibia. There usually is no dislocation of the ankle joint and minimal displacement of the fracture. A chip fracture of the metaphysis is a common fracture seen in abused infants and is commonly termed as a "bucket-handle" or "corner" fracture. A buckle fracture is a common accidental fracture seen in falls from a height.

• Question 472:

  While working in the emergency room you see a 14-month-old boy brought in with apparent leg pain. His parents tell you that he has recently been learning to walk and that this injury is the result of a fall. You obtain the following x-ray What is your interpretation of the x-ray?

  

  A. dislocation of the ankle

  B. a "chip" fracture of the proximal tibia

  C. a spiral fracture of the distal tibia

  D. a buckle fracture involving the distal tibia and fibula

  E. a transverse fracture of the distal tibia

  Correct Answer: C Section: (none)

  Explanation:

  The x-ray provided shows a nondisplaced spiral fracture of the distal tibia. This is also known as a toddler's fracture. This fracture can occur when the toddler begins to walk and twists on a planted leg. This torque can result in a spiral fracture of the planted tibia. There usually is no dislocation of the ankle joint and minimal displacement of the fracture. A chip fracture of the metaphysis is a common fracture seen in abused infants and is commonly termed as a "bucket-handle" or "corner" fracture. A buckle fracture is a common accidental fracture seen in falls from a height.

• Question 473:

  What is the most sensitive indicator of pneumonia in a child?

  A. tachycardia

  B. tachypnea

  C. hypotonia

  D. vomiting

  E. coughing

  Correct Answer: B Section: (none)

  Explanation:

  Tachypnea is the most sensitive clinical parameter for diagnosing a lower respiratory tract infection. The child may have tachycardia from a fever or anxiety but, typically, not simply from pneumonia. Coughing is common in children with pneumonia but it is not specific for lower respiratory tract infections, as it can also be seen in upper and lower respiratory tract infections

• Question 474:

  A 12-month-old male child is brought to your office for a well-child examination and immunizations. You have been following the child since delivery and are aware that he has acquired immune deficiency syndrome (AIDS) and a markedly reduced T-cell count. Which of the following vaccinations should he not receive?

  A. diphtheria, tetanus, and acellular pertussis (DTaP)

  B. diphtheria tetanus (dT)

  C. hepatitis B

  D. injectable polio vaccine (IPV)

  E. varicella

  Correct Answer: E Section: (none)

  Explanation:

  All of the vaccines mentioned, except varicella, are killed or synthetic vaccines. Varivax is an attenuated varicella strain (OKA) from Japan. Live virus vaccines are contraindicated in the case of AIDS with a markedly reduced T-cell count. The IPV is the inactivated version of the live polio vaccine, oral polio vaccine (OPV).

• Question 475:

  A newborn male is brought to you in the neonatal intensive care unit (NICU). On physical examination, you notice that the infant has deficient abdominal musculature and undescended testes. Your suspicion is high for a certain condition.

  Upon further imaging, what associated finding would be expected?

  A. posterior urethral valves on a voiding cystourethrogram (VCUG)

  B. hydrocephalus on head ultrasound

  C. cardiomegaly on chest x-ray (CXR)

  D. bilateral adrenal enlargement on abdominal ultrasound

  E. tracheoesophageal fistula on an upper gastrointestinal (UGI) series

  Correct Answer: A Section: (none)

  Explanation:

  The constellation of cryptorchidism, posterior urethral valves, and abnormal abdominal musculature is called Eagle-Barrett syndrome. Another name is prune belly syndrome. The greatest morbidity comes from the poor amniotic fluid production, due to bladder outlet obstruction, with a resulting pulmonary hypoplasia. Cushing's triad are hypertension, bradycardia, and widened pulse pressure. This is seen as terminal findings associated with increased intracranial pressure. VATER association has multiple anomalies, none of which are the three mentioned. VATER is a mnemonic which stands for Vertebral anomalies, Anal atresia (imperforate), Tracheo-Esophageal fistula, and Renal anomalies (the R also indicated Radial anomalies). It is sometimes referred to as VACTERL association in which the C indicates Cardiac anomalies with the L indicating Limb anomalies. Potter's syndrome is bilateral renal agenesis. This condition is fatal, due to marked pulmonary hypoplasia. The Jones criteria are used in the diagnosis of ARF.

• Question 476:

  A newborn male is brought to you in the neonatal intensive care unit (NICU). On physical examination, you notice that the infant has deficient abdominal musculature and undescended testes. Your suspicion is high for a certain condition.

  You presumptively diagnose the child with which of the following?

  A. VATER association

  B. Cushing's triad

  C. Potter's syndrome

  D. Jones criteria

  E. Eagle-Barrett syndrome

  Correct Answer: E Section: (none)

  Explanation:

  The constellation of cryptorchidism, posterior urethral valves, and abnormal abdominal musculature is called Eagle-Barrett syndrome. Another name is prune belly syndrome. The greatest morbidity comes from the poor amniotic fluid production, due to bladder outlet obstruction, with a resulting pulmonary hypoplasia. Cushing's triad are hypertension, bradycardia, and widened pulse pressure. This is seen as terminal findings associated with increased intracranial pressure. VATER association has multiple anomalies, none of which are the three mentioned. VATER is a mnemonic which stands for Vertebral anomalies, Anal atresia (imperforate), Tracheo-Esophageal fistula, and Renal anomalies (the R also indicated Radial anomalies). It is sometimes referred to as VACTERL association in which the C indicates Cardiac anomalies with the L indicating Limb anomalies. Potter's syndrome is bilateral renal agenesis. This condition is fatal, due to marked pulmonary hypoplasia. The Jones criteria are used in the diagnosis of ARF.

• Question 477:

  A 34-year-old male undergoes an uneventful excision of a parathyroid adenoma. The following postoperative day, he complains of numbness around his lips.

  Which of the following is the most appropriate intervention?

  A. oral calcium gluconate

  B. intravenous rehydration with normal saline

  C. intravenous magnesium sulfate infusion

  D. blood transfusion

  E. reassurance and close observation

  Correct Answer: A Section: (none)

  Explanation:

  Hungry bone syndrome refers to hypocalcemia following surgical correction of hyperparathyroidism in patients with severe, prolonged disease, as serum calcium is rapidly taken from the circulation and deposited into the bone. Symptoms usually occur within 2448 hours following parathyroidectomy, when calcium levels reach a nadir. Early symptoms include numbness and tingling in the perioral area, fingers, or toes. Advanced symptoms include nervousness, anxiety, and increased neuromuscular transmission evidenced by positive Chvostek's and Trousseau's signs, carpal pedal spasm, and hyperactive tendon reflexes. In severe cases, one may develop a prolonged QT interval on ECG. Patients who manifest any signs or symptoms of hypocalcemia always require intervention. In severely symptomatic patients, treatment should begin with intravenous calcium gluconate. Mildly symptomatic patients may be given oral calcium in the form of calcium lactate, calcium carbonate, or calcium gluconate. If hypocalcemia remains despite calcium supplementation, additional therapy with vitamin D may be needed. Supplemental calcium and vitamin D therapy should be continued until serum calcium levels return to normal

• Question 478:

  A CT scan in a patient with a temperature of 102.1°F and a history of an abdominal aortic graft reveals fluid around the graft. Which of the following is the most appropriate treatment?

  A. IV antibiotics and repeat CT scan in 2448 hours

  B. CT-guided catheter drainage of fluid collection

  C. exploration with graft excision, irrigation, and replacement with fresh graft

  D. exploration with graft excision and construction of axillobifemoral graft

  E. open exploration with debridement and drainage of fluid collection

  Correct Answer: D Section: (none)

  Explanation:

  The triad of fever, abdominal fluid collection, and history of abdominal graft surgery indicates the development of a graft infection. The most common organism isolated is S. aureus. It is a rare, but morbid, complication, with mortality rates as high as 36%. The infection may rapidly result in sepsis, hemorrhagic shock, and septic embolization. The standard treatment is early detection and surgical removal of the infected graft, with primary closure of the aorta and creation of an extra-anatomical reconstruction--most commonly an axillofemoral bypass. Such a bypass carries its own morbidities, including risk of limb loss, aortic stump blowout, and pelvic ischemia.

• Question 479:

  A 34-year-old male undergoes an uneventful excision of a parathyroid adenoma. The following postoperative day, he complains of numbness around his lips. Which of the following is the most likely cause of this symptom?

  A. hypocalcemia secondary to hypomagnesemia

  B. hypocalcemia due to acute renal failure

  C. hypocalcemia due to hungry bone syndrome

  D. hypocalcemia due to inadvertent injury to the recurrent laryngeal nerve

  E. postoperative hematoma of the neck

  Correct Answer: C Section: (none)

  Explanation: Hungry bone syndrome refers to hypocalcemia following surgical correction of hyperparathyroidism in patients with severe, prolonged disease, as serum calcium is rapidly taken from the circulation and deposited into the bone. Symptoms usually occur within 2448 hours following parathyroidectomy, when calcium levels reach a nadir. Early symptoms include numbness and tingling in the perioral area, fingers, or toes. Advanced symptoms include nervousness, anxiety, and increased neuromuscular transmission evidenced by positive Chvostek's and Trousseau's signs, carpal pedal spasm, and hyperactive tendon reflexes. In severe cases, one may develop a prolonged QT interval on ECG. Patients who manifest any signs or symptoms of hypocalcemia always require intervention. In severely symptomatic patients, treatment should begin with intravenous calcium gluconate. Mildly symptomatic patients may be given oral calcium in the form of calcium lactate, calcium carbonate, or calcium gluconate. If hypocalcemia remains despite calcium supplementation, additional therapy with vitamin D may be needed. Supplemental calcium and vitamin D therapy should be continued until serum calcium levels return to normal

• Question 480:

  A19-year-old college student is found to have an elevated serum calcium on routine physical examination. She has a family history of hypercalcemia that has not resulted in any known symptoms. Further workup reveals a slightly elevated serum parathyroid hormone with depressed levels of serum phosphate. A 24hour urine calcium excretion is obtained and is low. Which of the following is the correct diagnosis?

  A. familial hypocalciuric hypercalcemia (FHH)

  B. primary hyperparathyroidism

  C. secondary hyperparathyroidism

  D. tertiary hyperparathyroidism

  E. metastatic bone cancer

  Correct Answer: A Section: (none)

  Explanation:

  FHH, or familial benign hypercalcemia, is a rare condition characterized by asymptomatic or mildly symptomatic hypercalcemia. It is inherited as an autosomal dominant trait and the parathyroid glands are usually normal in size. The basis for the development of FHH appears to be mutations in the calcium-sensing receptor gene which regulates the parathyroid gland set point and modulates the extracellular calcium concentration. The condition may be mistaken for primary hyperparathyroidism because, in both conditions, the serum calcium and parathyroid hormone levels are elevated with a concomitant low serum phosphate. The distinction is made by obtaining a 24-hour urine calcium excretion level. In patients with FHH, the urine calcium level is low, whereas in primary hyperparathyroidism the level is high. The distinction is important, as patients with primary hyperparathyroidism benefit from surgery and those with FHH do not.