Paraclinic Usmle

4) A 10-month-old baby boy, recently adopted from Guyana, has a 5-hour history of crying, with intermittent drawing up of his knees to his chest. On the way to the emergency room he passes a loose, bloody stool. He has had no vomiting and has refused his bottle since the crying began. Physical examination is noteworthy for an irritable infant whose abdomen is very difficult to examine because of constant crying. His temperature is 38.8C (101.8F). The rectal ampulla is empty, but there is some gross blood on the examining finger. Which of the following studies would be most helpful in the immediate management of this patient?

54) A 19-year-old man with insulin-dependent diabetes mellitus is taking 30 units of NPH insulin each morning and 15 units at night. Because of persistent morning glycosuria with some ketonuria, the evening dose is increased to 20 units. This worsens the morning glycosuria, and now moderate ketones are noted in urine. The patient complains of sweats and headaches at night. Which of the following is the most appropriate next step in management?

65) A 2-year-old girl is brought to the emergency department with a fever, chills, poor appetite, and vomiting. On examination, she is irritable and diaphoretic. Her temperature is 39.2 C (102.5 F), blood pressure is 80/48 mm Hg, pulse is 88/min, and respirations are 17/min. She is tender at the left costovertebral angle. Initial laboratory tests show the following: Leukocyte count 16,300/mm3, Hemoglobin 12.5 g/dL, Platelet count 245,000/mm3, Blood urea nitrogen 6 mg/dL, Creatinine 0.5 mg/dl. Urinalysis is positive for leukocyte esterase and nitrite, with 150 white blood cells/hpf. After TV antibiotic administration and stabilization, what is the most appropriate diagnostic study?

66) A 2-year-old presents to the emergency center with several days of rectal bleeding. The mother first noticed reddish-colored stools 2 days prior to arrival and has since changed several diapers with just blood. The child is afebrile, alert, and playful, and is eating well without emesis. He is slightly tachycardic, and his abdominal examination is normal. Which of the following is the best diagnostic study to order to confirm the diagnosis?

86) A 22-year-old woman (G2POA1) is being followed by her family physician for pregnancy. She is currently at 28 weeks' gestation, feeling well, and gaining an appropriate amount of weight. She has not had sexual intercourse during her pregnancy. Her first prenatal exam at 12 weeks' gestation showed a negative HIV, Chlamydia, gonorrhea, and urine cultures. Her blood type is A negative and Rh (D) negative. She has not communicated with the father of the child during the pregnancy but is excited to raise the child with the help of her mother. She is unable to recall or confirm her immunization status for a number of vaccines. Which of the following measures is warranted at this time?

88) A 22-year-old woman comes to your office at 10 weeks gestation for her first prenatal visit. Her obstetrical history is significant for a spontaneous abortion at 12 weeks gestation one year ago. She states that her mother has hypothyroidism, and she asks you to order thyroid function tests for her. She denies any symptoms, and her physical examination is unremarkable. Ultrasound reveals an intrauterine gestation with normal fetal cardiac activity. Which of the following results is most likely to be expected in this patient?

97) A 23-year-old man comes to the emergency department because of a painful swollen left knee. The pain began after he twisted his leg while playing football. Examination shows a swollen left knee with marked tenderness of the medial side of the knee. When compared to the right knee, on valgus stressing the left knee shows exaggerated laxity at the joint line. Which of the following is the most appropriate next step to confirm the diagnosis?

106) A 23-year-old woman calls her physician for the results of her Pap test. She has a history of Chlamydia. She has never had an abnormal Pap. She occasionally has unprotected intercourse. The physician informs her that the Pap was normal. The patient is relieved, but wants to know whether this result could be wrong. The physician explains that a Pap test detects abnormal cells in roughly 4 of every 5 women who have abnormal cervical cells. Which of the following represents the sensitivity of the Papanicolaou test?

120) A 24-year-old woman comes to your office complaining of an 8-week history of amenorrhea. She is sexually active and uses OCPs for contraception. Her medical history is unremarkable. She does not have any particular complaints except moderate fatigue and a decline in mood. She denies headaches, visual disturbances, or any gastrointestinal symptoms. She denies cigarette smoking or any drug use, and drinks alcohol socially. Breast examination reveals a white, milky secretion upon expression of both nipples. A pelvic examination reveals a uterus of normal size. BMI is 28 kg/m2. Initial investigations reveal a negative serum beta-hCG level. According to these findings, which of the following is the most appropriate next step in the management of this patient?

134) A 25-year-old male presents with progressive shortness of breath over the past 6 months. His past medical history is significant only for neonatal hepatitis that resolved spontaneously when he was 6 months of age. The man has never smoked. On lung auscultation today, there are decreased breath sounds over both lower lobes. Chest x-ray demonstrates emphysematous changes in the bilateral lower lobes. Routine blood work is normal. Which of the following analyses would be most helpful in establishing this patient's diagnosis?

137) A 25-year-old nulligravid woman comes to the physician because of chronic pelvic and low sacral back pain for several months. The pain is usually worse premenstrually. She tried over the counter anti-inflammatory medications but had little relief. She has been in a monogamous relationship with her boyfriend for the past 4 years. She has no fever or abnormal vaginal discharge. Her temperature is 37.2 C (98.9 F), and blood pressure is 120/78 mm Hg. Physical examination shows tender posterior vaginal fornix and pain upon uterine motion. Complete blood count is normal. Pelvic ultrasonogram is normal. Urine pregnancy test is negative. Which of the following is most appropriate diagnostic test in her management?

150) A 26-year-old nulligravid patient presents to her physician seeking preconceptional advice. She plans to conceive in about 1 year. Her past medical history is significant for chickenpox as a child. She had an appendectomy 2 years ago. She takes no medications and is allergic to penicillin. Her complete physical examination, including a pelvic examination, is unremarkable. Which of the following is the most appropriate next step in diagnosis to prevent morbidity in this patient's offspring

152) A 26-year-old woman presents for evaluation of infertility. She describes her menstrual cycles as irregular stating that they occur anywhere between 32 to 35 days. She has no galactorrhea. She eats a balanced diet and exercises regularly. She has no other medical problems. Her BMI is 22 Kg/m2. Physical examination is unremarkable. Which of the following is the most appropriate initial test to evaluate her infertility?

155) A 27-year old woman comes to the physician for evaluation of infertility. She and her 31-year-old husband have not been able to conceive after 12 months of unprotected and frequent intercourse. She has regular 28-day menstrual cycles and during the menstrual cycles she develops mild pelvic pain and bilateral breast tenderness. She has no pain during sexual intercourse. Her blood pressure is 128/76 mm Hg and pulse is 82/min. Physical examination is completely unremarkable. Which of the following could most likely be abnormal in this patient?

158) A 27-year-old healthy woman comes to the office for evaluation of infertility. She and her 31 -year-old husband have not been able to conceive after 12 months of unprotected and frequent intercourse. Her husband is healthy and takes no medications. He has a normal semen analysis. She has regular 28-day menstrual cycles. The patient has mid-cycle pelvic pain and an egg white like consistency to her discharge mid-cycle. She has no pain during sexual intercourse. The patient does report having been hospitalized with a pelvic infection in her late teens, during which time she had pain with intercourse, discharge, and fever. Her sister was diagnosed with polycystic ovarian disease. Her blood pressure is 128/76 mm Hg and pulse is 82/min. Physical examination shows no abnormalities. Which of the following is most likely to be abnormal in this patient?

173) A 28-year-old G2, P 1woman in her 26th week of gestation comes to the office due to intermittent episodes of abdominal pain. She has been having these episodes for the past 4 days, and thinks that her fetus may be in distress. She points to her right flank when asked about the location of the pain, and says that it occasionally radiates to the groin area. She cannot identify any exacerbating or relieving factors. Her pregnancy has been uncomplicated so far. Her past medical history is significant for pelvic inflammatory disease. Her temperature is 37.5 C (99.5 F), blood pressure is 130/80 mm Hg, and pulse is 88/min. She is in considerable pain at the moment. Deep palpation of the right flank reveals tenderness. There is no CVA tenderness. Urinalysis shows: Specific gravity: 1.020, Blood: ++, Glucose: negative, Ketones: negative, Protein: negative, Leukocyte esterase: negative, Nitrites: negative. What is the best next step in the management of this patient?

174) A 28-year-old G3P2 woman at 32 weeks gestation comes to the physician because she has felt only 2 or 3 fetal movements in the past 12 hours. As in her previous pregnancies, she has gestational diabetes, which is under good control with diet and mild exercise. The patient does not use tobacco, alcohol, or illicit drugs. Vital signs are normal. Physical examination is unremarkable. Fetal heart tones are heard by Doppler. Which of the following is the most appropriate next step in management of this patient?

183) A 28-year-old woman comes to the physician for routine physical examination and a Pap smear. She has had multiple sexual partners and uses barrier methods for contraception. She was treated for chlamydial cervicitis four months ago. She has no other medical problems. Pelvic examination is unremarkable and a Pap smear was performed. A week later the result came as "satisfactory for evaluation" and shows mild dysplasia (low grade intraepitheliallesion). Which of the following is the most appropriate next step in management?

197) A 3-day-old, full-term baby boy is brought into the emergency department because of feeding intolerance and bilious vomiting. X-rays films show multiple dilated loops of small bowel and a "ground glass" appearance in the lower abdomen. The mother has cystic fibrosis. Which of the following diagnostic tests would also have therapeutic value?

222) A 3010-g (6.6-lb) boy was born to a 37-year-old primagravida by spontaneous vaginal delivery after an uncomplicated pregnancy. On examination he has cyanotic extremities and a significant right precordial heave, a single S2, and a harsh systolic ejection murmur along the sternal border. He also has a prominent squared nose and cleft palate. An echocardiogram is subsequently performed and demonstrates tetralogy of Fallot. Corrective surgery is performed without complications. At 2 months of age the infant is diagnosed with Pneumocystis jiroveci pneumonia, and at 3 months he is diagnosed with fungal septicemia. Additional work-up of this child should include which of the following tests?

224) A 31-year-old man with severe kyphoscoliosis due to cerebral palsy is experiencing worsening shortness of breath with exertion. On examination, he has a severe scoliosis to the left and decreased air entry to that side. His right lung is clear, JVP is 3 cm, and heart sounds are normal. Pulmonary function tests are performed. Which of the following is the most likely abnormality to be seen on the pulmonary function tests?

244) A 33-year-old woman, gravida 1, para 0, comes for a routine prenatal visit, for the first time. According to her history, she is at 18-weeks gestation. Her family history is significant for Down syndrome on her maternal side. She does not use tobacco, alcohol or drugs. Vital signs are normal, and physical examination is unremarkable. Initial laboratory studies show a decreased maternal serum alpha-fetoprotein (MSAFP). Which of the following is the most appropriate next step in management?

250) A 34-year-old G2P1 at 31 weeks gestation presents to labor and delivery with complaints of vaginal bleeding earlier in the day that resolved on its own. She denies any leakage of fluid or uterine contractions. She reports good fetal movement. In her last pregnancy, she had a low transverse cesarean delivery for breech presentation at term. She denies any medical problems. Her vital signs are normal and electronic external monitoring reveals a reactive fetal heart rate tracing and no uterine contractions. Which of the following is the most appropriate next step in the management of this patient?

251) A 34-year-old immigrant from Mexico presents following an episode of massive hemoptysis. He describes bringing up large amounts of bright red, foamy sputum. He denies any recent trauma. On physical examination, the patient is agitated and has difficulty speaking. His blood pressure is 100/60 mmHg and his heart rate is 110/min. On physical examination, breath sounds are audible bilaterally. You immediately initiate intravenous infusion of crystalloid. Portable chest x-ray shows opacity in the right upper lobe. Which of the following is the best next step in the management of this patient?

253) A 34-year-old man complains of severe abdominal pain. He describes the pain as "sharp" and "unbearable." It is located in the lower left abdomen and radiates to the perineum. He has vomited twice since the pain began. He denies dysuria. On exam, he is afebrile. He cannot lie still on the examination table due to his discomfort. Mucus membranes appear slightly dry. Lungs are clear to auscultation. Heart sounds are normal and there are no murmurs or gallops. His abdomen is soft and non-tender to palpation. Inspection and palpation of his genitalia is unrevealing. Extremities have no cyanosis, clubbing, or edema. Which of the following is the best test to diagnose this patient's condition?

297) A 39-year-old woman comes to the office and complains of double vision. She feels "weak all over," especially at the end of the day. She had the same complaints 8 months ago that persisted for several weeks, but she didn't see a doctor because she had no insurance then. She has no past medical history. Her mother has rheumatoid arthritis, and her brother has type 1 diabetes mellitus. Her vital signs are normal. She has diplopia and mild ptosis. Her blood profile, CBC and thyroid tests are within normal limits. Electromyography and repetitive nerve stimulation reveals a decremental response in compound action potentials. Her acetylcholine receptor antibody test is positive. Which of the following tests should be ordered next?

309) A 4-year-old child manifests symptoms of fever, sore throat, and swollen lymph nodes. The spleen tip is palpable. Throat culture and rapid slide (Monospot) test results are negative. The next logical diagnostic procedure would involve which of the following?

330) A 41-year-old woman presents to the emergency department with palpitations. On questioning she notes heat intolerance, nervousness, and insomnia. On physical examination the physician notes a fine tremor, diffuse non-pitting edema of the anterior lower leg, and bulging of both of her eyes. What finding on blood test would confirm the diagnosis?

337) A 42-year-old man is brought to the emergency department after a motor vehicle accident. He was a restrained driver and hit a car from behind on a highway. He drank one glass of wine before driving. He occasionally uses cocaine. His medical problems include mild intermittent asthma and peptic ulcer disease. On initial evaluation, his blood pressure is 112/92 mm Hg and pulse is 96/min. His pulse oximetry shows 95% on room air. Examination shows bruises on the anterior chest wall and abdominal wall. X-rays reveal a fracture of the eighth left rib but no pneumothorax or pleural effusion. Cervical C-spine series are negative. An ultrasound does not show free intraperitoneal fluid. An ECG shows normal sinus rhythm with no ST-segment or T-wave changes. He is treated with intravenous fluids and analgesics. Eight hours later, he complains of epigastric discomfort, left shoulder pain, and mild nausea. His blood pressure is 97/62 mm Hg and pulse is 112/min. His pulse oximetry shows 96% on room air. Which of the following is most likely to diagnose this patient's current condition?

325) A 40-year-old school teacher comes to the physician's office complaining of joint pain. Her symptoms began 10 days ago and consist of pain in the metacarpophalangeal (MCP) joints, proximal interphalangeal (PIP) joints, wrists, knees and ankles, bilaterally. She describes joint stiffness lasting 10 to 15 minutes after a prolonged rest. She denies fever, malaise, weight loss and skin rash. Her past medical history is insignificant. She does not take any medications. On examination, there is no evidence of swelling, redness or tenderness of the involved joints. The remainder of the physical examination is unremarkable. Which of the following is most likely elevated in this patient?

340) A 42-year-old previously well woman presents with pruritus. She is not taking any medications, and only drinks alcohol on a social basis. Her physical examination is entirely normal with no signs of chronic liver disease or jaundice. Laboratory evaluation reveals an alkaline phosphatase level of three times normal, and an ultrasound of the liver and gallbladder is normal. Which of the following is the most appropriate next step in diagnosis?

345) A 43-year-old male complains of frequent epigastric burning not relieved by antacids. The sensation is typically brought on by heavy lifting at work and takes 10-15 minutes to go away. He denies having associated arm or neck pain, cough, shortness of breath or difficulty swallowing. His past medical history is significant for systemic lupus erythematosus (SLE) diagnosed five years ago, for which he takes low-dose prednisone daily. On physical examination, his blood pressure is 140/90 mmHg and pulse is 80/min and regular. Heart, lung, and abdomen exams are unremarkable. EKG is normal. Which of the following is the best next step in managing this patient?

349) A 44-year-old unrestrained male driver is brought to the ER after a motor vehicle accident. Cervical spine is immobilized. His breathing is normal. At the scene of the accident, his blood pressure is 70/30 mm Hg. After receiving two liters of intravenous fluid, his blood pressure is 80/40 mmHg. Neck veins are collapsed. Lungs are clear to auscultation. Abdomen is mildly distended. There is no obvious source of external bleeding. No intraperitoneal blood or solid organ damage is seen on ultrasonogram or diagnostic peritoneal lavage. Imaging studies reveal a pelvic fracture and fracture of the right fourth rib. Which of the following is the most appropriate next step in management?

393) A 48-year-old white male complains of generalized bone pain after undergoing bowel surgery for inflammatory bowel disease. His pain is more severe at the lower spine, pelvis, and lower extremities. Examination shows tenderness over the lower spine, pelvis, and lower extremities. Proximal muscle weakness is noted. X-rays of the lumbar spine show decreased bone density with blurring of the spine. X-rays of the femoral neck show pseudofractures, bilaterally. Which of the following lab abnormalities is consistent with this patient's diagnosis?

403) A 5-week-old infant presents with a 1-week history of progressive nonbilious emesis, associated with a 24-hour history of decreased urine output. The infant continues to be active and eager to feed. On examination, the infant has a sunken fontanels and decreased skin turgor. The abdomen is scaphoid, and with a test feed, there is a visible peristaltic wave in the epigastrium. Electrolytes and a urinalysis are evaluated. Which of the following laboratory findings are most likely to be seen in this patient?

428) A 52-year-old Caucasian male presents complaining of diminished energy for the past three months. He appears very sad and moves slowly. He says that he has been feeling terrible after his wife died in a car accident three months ago. He is filled with thoughts of guilt because he was driving the car when the accident took place. Since then, he has been suffering from disturbed sleep and finds himself unable to focus on his favorite activities, like coin collecting or fishing. He reports being disturbed by repeated flashbacks of the event. He keeps himself aloof and isolated from others because he "just doesn't feel like socializing anymore." He adds that he has a poor appetite and has gained 20 lbs (9.1 kg). He admits to wanting to "end my life in order to escape the memories of that nightmarish day." He is able to contract for safety. What is the most appropriate next step?

463) A 56-year-old female comes to the office and complains of general malaise and headaches. Her other symptoms are episodic palpitations, throbbing headaches and diaphoresis. She feels "very anxious all the time." Her past medical history is unremarkable. Her deceased sister had very high blood pressure. Her blood pressure is 230/110 mmHg and pulse is 110/min. Initial laboratory studies reveal: WBC 7,000/cmm, Hb 11.2 g/L, Platelets 325,000/cmm, Calcium 11.9 mg/dl. What is the best next step in the evaluation of this patient?

468) A 56-year-old man presents to his urologist for continued evaluation of hypertension and hematuria. The patient has a 10-year history of hypertension and recent onset of painless hematuria for which he sought the attention of an urologist 3 months ago. On detailed questioning, the man states that he has been having severe headaches that are refractory to narcotic analgesics. Three days ago, a renal ultrasound was obtained that demonstrated bilaterally enlarged kidneys with multiple cysts. Which of the following is the most appropriate next step in diagnosis?

469) A 56-year-old man presents with progressive jaundice that he first noted 6 weeks ago. The patient has lost about 20 pounds over the past 2 months and he has persistent, nagging pain deep into his epigastrium and upper back. Except for the obvious jaundice and the signs of weight loss, physical examination is remarkable only for the presence of a vaguely palpable, nontender mass under the liver edge. His hemoglobin is 14 g/dL, and there is no occult blood in the stool. Total bilirubin is 22 mg/dL, with 16 mg/dL direct (conjugated) fraction. The transaminases are minimally elevated, whereas the alkaline phosphatase is about 8 times the upper limit of normal. A sonogram shows dilated intrahepatic ducts, dilated extrahepatic ducts, and a much distended, thinwalled gallbladder without stones. Which of the following is the most appropriate next step in diagnosis?

470) A 56-year-old previously healthy physician notices that his eyes are yellow and he has been losing weight. On physical examination the patient has jaundice and scleral icterus with a benign abdomen. Transcutaneous ultrasound of the abdomen demonstrates biliary ductal dilation without gallstones. Which of the following is the most appropriate next step in the workup of this patient?

505) A 60-year-old Hispanic laboratory technician presents with increasing fatigue and generalized weakness for the last 2 months. He also has chronic pain in the lower back and legs when he walks. He has been smoking 2-3 packs of cigarettes daily for 30 years, and drinks alcohol almost daily. His mother has diabetes, while his father died of a stroke. Physical examination reveals pallor. There is mild hepatomegaly. The neurological examination is completely normal. Complete work-up reveals: CBC: Hemoglobin 9.8 g/L, MCV 85 fl, Platelets 226,000/mm3, Leukocyte count 6,500/mm3, Neutrophils 60%, Eosinophils 1%, Lymphocytes 29%, Lvlonocytes 10%. Chemistry panel: Serum sodium 138 mEq/L, Serum potassium 4.0 mEq/L, Bicarbonate 24 mEq/L, Blood urea nitrogen (BUN) 28 mg/dL, Serum creatinine 2.1 mg/dL, Calcium 11.2 mg/dL, Blood glucose 98 mg/dL. Liver studies: Albumin 4.0 mg/dL, Total protein, serum 9.5 g/dL, Total bilirubin 1.0 mg/dL, Direct bilirubin 0.8 mg/dL, Alkaline phosphatase 110 U/L, Aspartate aminotransferase (SGOT) 58 U/L, Alanine aminotransferase (SGPT) 25 U/L. ESR is 100 mm/h. What is the best next step in the management of this patient?

507) A 60-year-old male farmer presents to the office for the evaluation of a slightly painful ulcer on the top of his lower lip. The ulcer has not healed since he first noticed it three months ago. He has always been healthy and denies any sexual activity during the past year. He is afebrile. Physical examination shows a 3x7 mm, partially encrusted ulcer in the vermilion zone near the moist line (mucocutaneous junction) of the lower lip, surrounded by a 6 x 12 mm area of induration. There are no palpable submental or submandibular lymph nodes. The remainder of the physical examination is unremarkable. Complete blood count and differential are normal. Biopsy of the ulcer will most likely to show:

532) A 63-year-old man presents with a 2-month history of dysphagia for both solids and liquids. He has had a 6.6 lb (3kg) weight loss over this time. His past medical history is remarkable for a transient ischemic attack 6 months ago, two bouts of pneumonia in the past 3 months, and chronic heartburn treated with over-the-counter antacids. Physical examination shows a supple neck without masses. Abdominal examination shows mild epigastric tenderness to deep palpation. Chest x-ray is normal for his age. Which of the following is the most appropriate next step in diagnosis?

570) A 68-year-old Caucasian male complains of right-sided leg pain over the last year. The pain is poorly controlled with over-the-counter pain medications. He also complains of frequent headaches. His past medical history is significant for hypertension and recent hearing loss. An X-ray of the skull shows areas of bone resorption and sclerosis. Which of the following are the most likely findings on laboratory work-up? (Serum calcium, serum phosphate, alkaline phosphatase, Urinary hydroxyproline)

580) A 68-year-old woman comes to the physician because of a painful lump in her vagina. She states that the lump has been there for a few months, but has recently begun to cause her pain. She has hypertension, for which she takes a diuretic, but no other medical problems. Examination shows a 4 cm cystic mass near the patient's introitus by the right labia. The mass is mildly tender. The remainder of the pelvic examination is normal. Which of the following is the most appropriate next step in management?

628) A 75-year-old woman comes to the physician because of irregular vaginal bleeding. She has been menopausal for the past 25 years, but has noted on-and-off spotting for the past 2 years, which she finds intolerable. She has a complicated past medical history including hypertension, diabetes, and severe chronic obstructive pulmonary disease. Examination is unremarkable. An endometrial biopsy is performed that demonstrates an endometrial polyp with atypical cells that are difficult to grade. Which of the following is the most appropriate next step in management?

666) A patient is seen on the first postoperative day after a difficult abdominal hysterectomy complicated by hemorrhage from the left uterine artery pedicle. Multiple sutures were placed into this area to control bleeding. Her estimated blood loss was 500 mL. The patient now has fever, left back pain, left costovertebral angle tenderness, and hematuria. Her vital signs are temperature 38.2C (100.8F), blood pressure 110/80 mm Hg, respiratory rate 18 breaths per minute, and pulse 102 beats per minute. Her postoperative hemoglobin dropped from 11.2 to 9.8, her white blood cell count is 9.5, and her creatinine rose from 0.6 mg/dL to 1.8 mg/dL. What is next best step in the management of this patient?

669) A patient with benign prostatic hyperplasia has moderately severe symptoms and is started on finasteride. After six months of treatment with finasteride, his symptoms improve remarkably and his prostate has regressed in size. Which of the following histological patterns was most likely present at the time of initiation of treatment?

711) An otherwise healthy 28-year-old man comes to his physician because of painless enlargement of the right testis. He began to feel a sensation of heaviness in the right hemiscrotum approximately 6 months ago. Physical examination reveals diffuse enlargement of the right testis, but it is difficult to determine whether this is due to an intratesticular or extratesticular lesion. Which of the following is the most appropriate next step in diagnosis?

728) On postpartum day 2 after a vaginal delivery, a 32-year-old G2P2 develops acute shortness of breath and chest pain. Her vital signs are blood pressure 120/80 mm Hg, pulse 130 beats per minute, respiratory rate 32 breaths per minute, and temperature 37.6C (99.8F). She has new onset of cough. She appears to be in mild distress. Lung examination reveals clear bases with no rales or rhonchi. The chest pain is reproducible with deep inspiration. Cardiac examination reveals tachycardia with 2/6 systolic ejection murmur. Pulse oximetry reveals an oxygen saturation of 88% on room air and oxygen supplementation is initiated. Which of the following is the best diagnostic tool to confirm the diagnosis?