USMLE USMLE Certifications USMLE-STEP-2 Questions & Answers

• Question 511:

  An 11-month-old girl presents to your office with a fever of 39°C she has had for 2 days. She has also vomited frequently and had decreased fluid intake. She looked tired and ill but on examination, had no apparent source of infection. She appeared to be 510% dehydrated.

  You decide to obtain a urine specimen for analysis and culture. Which of the following is the best method?

  A. Collect a midstream "clean catch" specimen.

  B. Collect a catheterized specimen.

  C. Place an adhesive bag to collect urine.

  D. Obtain urine from a diaper.

  E. Collect urine after she urinates in a potty chair.

  Correct Answer: B

  Urine for urinalysis and culture must be properly obtained. Catheterization is the most reliable method of the choices offered. Suprapubic tap is considered the "gold-standard" but is not always technically feasible, especially in an outpatient office setting. Amidstream, clean catch specimen would be acceptable in an older, toilet-trained child. "Bagged" specimens are not recommended because of possible skin or fecal contamination of the specimen. Similarly, obtaining a sample from a diaper or potty would be unacceptable. Urinalysis includes dipstick method and microscopic examination. Leukocyte esterase (an enzyme in WBC) and nitrites suggest probable infection. Microscopic analysis of unspun urine for WBC (>10/ highpower field) or bacteria is also predictive of infection. RBCs are often present in a UTI. The patient is vomiting and dehydrated; this may indicate possible pyelonephritis. The most appropriate course would be IV hydration and empiric treatment with antibiotics (ceftriaxone) while awaiting cultures. Children with pyelonephritis are at increased risk of renal scarring, especially younger children, and should be treated early. E. coli is the most common organism cultured; others include Proteus, Klebsiella, S saprophyticus, and Enterococcus. The occurrence of a UTI in a girl under age 35 years and in a boy of any age may be a marker for an underlying congenital anatomic abnormality, in particular, vesicourethral reflux. Radiologic investigation with renal ultrasound and VCUG is recommended

• Question 512:

  Amother brings in her 3-year-old girl because she felt a smooth mass on the left side of her belly when she was giving her a bath. Which of the following is the most likely diagnosis?

  A. Wilms tumor

  B. neuroblastoma

  C. acute lymphoblastic leukemia

  D. Hodgkin's disease

  E. hepatoblastoma

  Correct Answer: A

  Wilms tumor is a malignant embryonal neoplasm of the kidney. It is the second most common solid tumor of childhood. Girls are affected more frequently than boys (2:1). The incidence of Wilms tumor peaks at 13 years of age. The classic presentation is a painless abdominal mass that is usually hard, smooth, and unilateral. Hematuria occurs in 1225% of children with Wilms tumor, and hypertension has been reported in up to 60% of patients. Aniridia or hemihypertrophy may be observed in patients with Wilms tumor.

• Question 513:

  A 14-year-old boy complains of breast enlargement on the left side. He denies pain, discharge, or any drug use. He is on no medications and is otherwise healthy. On physical examination, his sexual maturity rating (Tanner) is stage II for both genitalia and pubic hair growth. Initial management should include which of the following?

  A. magnetic resonance imaging of the head

  B. urine drug screen for marijuana

  C. chromosome analysis

  D. reassurance that this is a normal condition

  E. ultrasound imaging of the abdomen and testes

  Correct Answer: D

  Gynecomastia is the enlargement of male breast tissue and occurs in approximately onethird of adolescent males during early- to midpuberty. It usually resolves spontaneously and requires no further evaluation beyond a careful history and physical examination. Features include: breast tissue <4 cm in diameter and resembling female breast budding, and pubertal development between Tanner stage II and

  IV. Pubertal development signs precede gynecomastia by at least 6 months. It may be more noticeable in obese boys. A drug and medication history should be obtained; these include estrogens, androgens, human chorionic gonadotropin (hCG), cardiovascular drugs (reserpine, methyldopa, digitalis), cytotoxic agents (busulfan, vincristine), antituberculosis drugs (INH), psychoactive drugs (tricyclic antidepressants, diazepam), ketoconazole, spironolactone, cimetidine, and phenytoin. Illegal drugs include marijuana, heroin, methadone, amphetamines, as well as alcohol. If there is evidence of precocious puberty, hypogonadism or macrogynecomastia (breast tissue >5 cm diameter), laboratory testing should be done including dehydroepiandrosterone sulfate (DHAS), FSH, and LH, hCG, estradiol, and testosterone. Thyroid- stimulating hormone (TSH) may be obtained to rule out hyperthyroidism. Boys with Klinefelter syndrome have hypogonadism (testes <3 cm in diameter), delayed pubertal development, and gynecomastia. Laboratory tests reveal increased FSH and LH, and decreased testosterone; the diagnosis is confirmed by chromosome analysis. If DHAS, hCG, or estradiol levels are increased, an MRI of the head to exclude a CNS tumor and ultrasound of abdomen and testes to rule out an adrenal, liver, or testicular tumor should be considered.

• Question 514:

  The parents request some treatment for this condition. Which of the following is the most appropriate treatment for a child of this age?

  A. bladder stretching exercises

  B. intranasal DDAVP (desmopressin acetate)

  C. imipramine

  D. conditioning therapy with a bed-wetting alarm

  E. reassurance of the parents and restriction of fluids before bedtime

  Correct Answer: E

  Active treatment should be avoided in children under age 6 years, as nocturnal enuresis is common. Parents should be reassured that the condition is self-limited. Fluid intake 1 hour before sleep should be restricted. Simple behavioral reinforcement, such as a star or sticker chart to record dry nights, may be helpful. Punitive or humiliating measures should be discouraged. Bladder-stretching exercises and encouraging children to hold urine for longer periods during the day are usually not helpful. Pharmacologic therapy is not curative. DDAVP is a synthetic analog of antidiuretic hormone. It reduces urine production overnight. Hyponatremia has been reported with use of this drug. If used, it should only be for a limited time. Imipramine is a tricyclic antidepressant which was used more often in the past. It is effective in 3060% of children, but side effects include anxiety, insomnia, and dry mouth. There is a poisoning risk, especially for younger children. Conditioning therapy may be considered in children older than 6 years. Success rates range from 30 to 60%. It involves the use of an alarm attached to electrodes in the underwear, which sounds when the child voids. Consistent use of the device is often helpful; it is more effective in older, more motivated children. A common complaint is that the alarm wakes up other family members but not the affected child

• Question 515:

  A 5-year-old boy has a history of bed-wetting about four to five times a week. He has recently begun to attend kindergarten. He was toilet trained (dry during the day) by age 3 but has never been consistently dry at night. He denies any dysuria or frequency. There is no history of increased thirst or frequent urination. The urinalysis is negative for blood, protein, glucose, or ketones; there are no white cells or bacteria; the specific gravity is 1.020. Which of the following is the most likely diagnosis?

  A. a urinary tract infection (UTI)

  B. primary nocturnal enuresis

  C. secondary enuresis caused by stress of the new school

  D. diabetes mellitus

  E. diabetes insipidus

  Correct Answer: B

  Enuresis may be primary (75%) where nocturnal control was never achieved; secondary enuresis (25%) is when the child was dry at night for at least a few months. Nocturnal enuresis is more common in boys, and family history is positive in at least 50%. This may affect as much as 20% of children at age 5 years, and it spontaneously stops in at least 15% of affected children every year. Psychological factors are often involved in secondary enuresis. A careful history should be obtained to rule out such organic factors as UTI (dysuria, frequency, urgency). Children with diabetes insipidus or diabetes mellitus have polydipsia and polyuria. Urinalysis should be considered to rule out an organic cause. In diabetes mellitus, urinalysis may reveal glycosuria and ketonuria. Aurinespecific gravity of >1.015 makes diabetes insipidus unlikely.

• Question 516:

  A 2-year-old boy has had a purulent drainage from the right nostril for a week. He is afebrile and has had no associated symptoms, such as cough. Which of the following is the most likely diagnosis?

  A. sinusitis

  B. nasal polyps

  C. an upper respiratory infection

  D. a foreign body in the right nostril

  E. allergic rhinitis

  Correct Answer: D

  Children frequently insert foreign bodies into the nose. Initial symptoms are local obstruction, sneezing, and pain. Subsequently, there is swelling and infection leading to a purulent, malodorous, and often bloody discharge. The infection clears after removal of the foreign body. Nasal polyps cause obstruction of the nasal passages, hyponasal speech, and mouth breathing; gray, grape-like masses can be visualized on nasal examination. An upper respiratory infection is usually suggested by a careful history. Initial symptoms include a scratchy throat, followed by development of thin nasal discharge and sneezing. Myalgia, low- grade fever, headache, malaise, and decreased appetite may be present. By the 2nd or 3rd day, the discharge becomes thicker and more purulent. Cough is common. Symptoms usually resolve by 710 days. Adolescents with sinusitis may have classic symptoms of headache and sinus tenderness. In children, cough and nasal discharge are common; the cough is worse when supine. If upper respiratory infection symptoms persist without improvement for >10 days, sinusitis should be considered. A more acute form may occur, with a shorter duration and more severe symptoms such as fever >39°C, purulent nasal discharge, headache, and eye swelling. Children with allergic rhinitis present with sneezing, clear watery, rhinorrhea, and itching of the nose, palate, pharynx, and eyes. Itching, redness, and tearing of the eyes may be present. This occurs in response to exposure to an allergen such as pollen, mold spores, and animal or mite antigens

• Question 517:

  A 7-year-old girl presents with hives, which developed after a bee sting. She has no other symptoms. The hives resolve with diphenhydramine. Which of the following is the most appropriate management?

  A. Write a prescription for diphenhydramine in case she is bitten again.

  B. Provide an Epi-pen Jr (epinephrine auto injector) to be carried at all times, as well as a prescription for diphenhydramine.

  C. Admit to the hospital for observation for delayed hypersensitivity symptoms.

  D. Refer her to an allergist for desensitization.

  E. Order a skin-prick test with hymenoptera venom.

  Correct Answer: B

  The insect order Hymenoptera includes ants, bees, and wasps. Their venom usually only causes a local reaction. About 14% of the population is sensitized to the venom and at risk for immediate hypersensitivity reactions. Reactions may include urticaria, angioedema, wheezing, or hypotension. Severe reactions should be treated with IV fluids, oxygen, and epinephrine. Although the child responded well to diphenhydramine, because there was a systemic reaction, it is advisable to carry an Epi-pen Jr at all times. Only children with life-threatening systemic reactions need to be referred for desensitization. Testing IgE or skinprick test with Hymenoptera venom is not predictive of future systemic reactions.

• Question 518:

  A 2-month-old infant is brought to the emergency department with irritability and lethargy. The parents state that he was well until he rolled off the couch on to the floor yesterday. On examination, he is inconsolable and afebrile. The fontanels are full and tense. He has a generalized tonic-clonic seizure. Which of the following is the most important initial diagnostic study to order?

  A. serum calcium, phosphorus, and magnesium levels

  B. analysis of cerebrospinal fluid (CSF)

  C. cranial computed tomography (CT) scan

  D. serum ammonia level

  E. serum acetaminophen level

  Correct Answer: C

  Though infection must be considered as an etiology, acute trauma is more likely in this scenario. This case represents the classic picture of the shaken baby syndrome which produces intracranial trauma without obvious external findings. This infant is critically ill and lacks preceding illness or constitutional symptoms. The tense fontanels reflect increased intracranial pressure. Acranial CT scan may show diffuse edema or a localized lesion, such as a subdural hemorrhage. Metabolic causes of seizures do not cause increased intracranial pressure. Acetaminophen toxicity does not cause CNS symptoms.

• Question 519:

  A 9-month-old male is in for a well-child checkup. He is greater than 90th percentile for height, and he

  weighs 25 lbs. He no longer fits in his infant car seat, which is only recommended for use by children

  under 20 lbs.

  Which of the following is the safest car seat option for him?

  A. to remain in the rear-facing infant seat until he is 1 year old, in the rear seat of the car

  B. turn the infant seat to face forward, in the rear seat of the car

  C. a rear-facing car seat suitable for a larger child (2040 lbs), in the rear seat of the car

  D. a forward-facing car seat suitable for a larger child (2040 lbs), in the rear seat of the car

  E. a forward-facing car seat suitable for a larger child (2040 lbs), in the front seat of the car

  Correct Answer: C

  The AAP recommends that children should face the rear of the vehicle until they are at least 20 lbs and 1 year of age to reduce the risk of cervical spine injury in the event of a crash. Infants who weigh 20 lbs before 1 year of age should ride rear facing in a convertible seat or infant seat approved for higher weights until 1 year of age. A car seat should never be placed in the front passenger seat.

• Question 520:

  A5-year-old child was hit in the right eye by a toy. He is rubbing at his eye, which is watering profusely. There is a small abrasion at the corner of the eye. He is mildly photophobic, but his pupils are equal, symmetric, and reactive to light and accommodation. His vision is normal.

  Which of the following is the most appropriate next step in the management of this patient?

  A. Perform a fluorescein dye stain of the cornea to determine if there is a corneal abrasion.

  B. Refer him immediately to an ophthalmologist.

  C. Irrigate the eye with sterile normal saline.

  D. Discharge him to home with antibiotic eye ointment.

  E. Apply a patch to the eye and follow-up in a week.

  Correct Answer: A

  Superficial corneal injuries expose underlying layers causing pain, photophobia, tearing, and decreased vision. Irrigation is recommended only if a foreign body is suspected. Abrasions are detected by instilling fluorescein dye and inspecting the cornea using blue-filtered light. Treatment consists of frequent applications of topical antibiotic ointment until the epithelium is healed. The use of a patch does not accelerate healing, and if improperly applied, may abrade the cornea. Referral to an ophthalmologist should be considered if there are significant changes in vision, or signs of deeper or more penetrating injury which often result in papillary bnormalities.