MKSAP quiz on ultrasound


Case 1: Hematuria and pain

A 57-year-old man is evaluated in the emergency department for a 3-day history of left inguinal pain and gross hematuria. He reports no history of kidney stones or kidney disease. Medical history is notable for hypertension and dyslipidemia. Medications are amlodipine and atorvastatin.

On physical examination, temperature is 37.2 °C (98.9 °F), blood pressure is 129/78 mm Hg, pulse rate is 96/min, and respiration rate is 12/min. BMI is 24. There is no left costovertebral angle tenderness.

Laboratory studies show normal complete blood count, serum electrolytes, blood urea nitrogen, and serum creatinine. Dipstick urinalysis reveals 3+ blood, trace protein, and negative leukocyte esterase and nitrites. Urine microscopy shows 1–2 leukocytes/hpf, too numerous to count erythrocytes, and no casts.

A kidney ultrasound shows normal-appearing kidneys, no hydronephrosis, and no nephrolithiasis.

Which of the following is the most appropriate diagnostic test to perform next?

A. Doppler ultrasonography of the renal veins
B. Kidney biopsy
C. Noncontrast helical abdominal CT
D. Urine culture

View correct answer for Case 1

Case 2: Community-acquired pneumonia

A 68-year-old man was admitted to the hospital 4 days ago for community-acquired pneumonia. He has COPD and presented with a 2-week history of fever and increasing shortness of breath, but no increase in his baseline cough. He was hypoxic, and a chest radiograph showed new patchy infiltrates in addition to his underlying interstitial changes but no pleural effusions. Empiric antibiotics were initiated, and blood and sputum cultures have shown no growth. His dyspnea and oxygenation have not improved significantly since admission. Medical history is otherwise unremarkable. He has a 45-pack-year smoking history and continues to smoke. Medications are tiotropium, fluticasone-salmeterol, and as-needed albuterol metered dose inhalers and intravenous cefotaxime and azithromycin.

On physical examination, temperature is 38.6 °C (101.5 °F), blood pressure is 128/55 mm Hg, heart rate is 97/min, and respiration rate is 33/min. Oxygen saturation is 92% with the patient breathing 6 L/min of oxygen by nasal cannula. BMI is 28. Pulmonary examination shows decreased air movement and scattered rhonchi throughout both lung fields, unchanged from admission. Cardiac and abdominal examinations are unremarkable, and no lower extremity edema is present.

Laboratory studies show a leukocyte count of 13,500/µL (13.5 × 109/L) (on admission, 14,700/µL [14.7 × 109/L]). Metabolic studies are normal.

Chest radiograph continues to show multilobar, patchy infiltrates and increased interstitial markings without pleural effusions, unchanged from admission.

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

A. Bronchoscopy
B. Chest CT
C. Chest ultrasonography
D. Thoracoscopic lung biopsy

View correct answer for Case 2

Case 3: Painful swollen thigh

A 43-year-old man is evaluated for a 2-day history of painful swelling of the left thigh just below the groin. He reports no preceding trauma, immobility, surgery, hospital stay, or long-distance airline travel. Medical history is notable for well-controlled hypertension. His only medication is losartan.

On physical examination, vital signs are normal. BMI is 28. An approximately 6-cm area of erythema and tenderness with a palpable cord is present overlying the greater saphenous vein on the proximal medial aspect of the left thigh up to the inguinal crease, consistent with superficial thrombophlebitis. Examination of the distal extremities is normal, without swelling or asymmetry. The remainder of the examination is unremarkable.

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

A. Low-dose aspirin
B. Serum D-dimer testing
C. Venous duplex ultrasonography of the left thigh
D. Warm compresses and NSAIDs

View correct answer for Case 3

Case 4: Pyelonephritis not improving on antibiotics

A 50-year-old woman is evaluated in the hospital for persistent fever and flank pain. She was admitted 3 days ago for treatment of pyelonephritis because of nausea and vomiting. Her fever is persistent after 72 hours of treatment. Medical history is unremarkable. Her only medication is intravenous ceftriaxone.

On physical examination, temperature is 39.0 °C (102.2 °F), blood pressure is 110/60 mm Hg, pulse rate is 110/min, and respiration rate is 18/min. BMI is 26. Right costovertebral angle tenderness is noted on abdominal examination. The remainder of the examination is noncontributory.

Urinalysis and culture on admission revealed greater than 100,000 colony-forming units/mL of Escherichia coli susceptible to ceftriaxone. Blood culture is negative.

Which of the following is the most appropriate management?

A. Kidney imaging
B. Repeat urine culture
C. Switch to gentamicin
D. Continued observation

View correct answer for Case 4

Case 5: Pregnant with pancreatitis

A 28-year-old woman was hospitalized 2 days ago for gallstone pancreatitis. She is in the sixteenth week of pregnancy. She now feels well and is tolerating oral intake. Approximately 2 weeks ago she had an episode of severe right upper quadrant and shoulder pain associated with nausea that lasted 2 hours and then resolved. Her medical history is otherwise unremarkable, and her only medication is a prenatal vitamin.

On physical examination, vital signs are normal. Abdominal examination reveals an enlarged uterus consistent with pregnancy, and no hepatomegaly or abdominal tenderness is noted.

Laboratory studies, including a complete blood count, serum amylase, and serum total bilirubin, are normal.

Ultrasound of the right upper quadrant reveals gallbladder stones, no bile duct dilatation, and a normal pancreas.

Which of the following is the most appropriate management?

A. Bile acid dissolution therapy
B. Cholecystectomy after delivery
C. Cholecystectomy prior to hospital discharge
D. Endoscopic retrograde cholangiopancreatography with sphincterotomy
E. Extracorporeal shock-wave lithotripsy

View correct answer for Case 5


Answers and commentary

Case 1

Correct answer: C. Noncontrast helical abdominal CT.

Noncontrast helical abdominal CT is the most appropriate diagnostic test to perform next in this patient with a clinical presentation consistent with nephrolithiasis. The findings of unilateral pain combined with hematuria without inflammation on urinalysis suggest nephrolithiasis, and the location of the pain in the inguinal region suggests that the stone may be in the distal ureter. Ultrasonography is increasingly used as an initial study for evaluation of suspected nephrolithiasis because of increased availability, lack of radiation exposure, and lower cost than CT; it is also the study of choice in pregnant patients. However, ultrasonography is less sensitive than CT for detecting kidney stones in the distal ureter or for evaluating other potential nonurologic conditions that may be responsible for the pain. Given this patient's clinical picture that is consistent with nephrolithiasis but with a negative ultrasound for kidney stones, further imaging with noncontrast helical abdominal CT is indicated. Additionally, the absence of hydronephrosis on ultrasound does not rule out nephrolithiasis.

Although renal vein thrombosis can cause hematuria, this diagnosis is less likely given the location of this patient's pain, normal kidney function, and lack of proteinuria. Therefore, Doppler ultrasonography of the renal veins is inappropriate.

Kidney biopsy may be appropriate for patients with suspected glomerulonephritis. Glomerulonephritis typically presents with evidence of decreased kidney function with inflammation and glomerular damage seen as variable proteinuria, hematuria, and possibly dysmorphic erythrocytes and erythrocyte casts on urinalysis. However, this patient's clinical history and laboratory findings are not consistent with glomerulonephritis, and kidney biopsy is not indicated.

Urine cultures are appropriate to diagnose a urinary tract infection or pyelonephritis. However, a urinary tract infection is unlikely in this patient given the absence of dysuria and a urinalysis negative for significant leukocytes, leukocyte esterase, or nitrites.

Key Point

  • Ultrasonography and noncontrast helical CT of the abdomen are testing options for evaluation of suspected nephrolithiasis; CT is indicated if initial ultrasound testing is negative in a patient with a high clinical suspicion for kidney stones.

Return to the next case

Case 2

Correct answer: B. Chest CT.

A chest CT should be obtained in this patient with nonresponsive pneumonia. He presents with severe community-acquired pneumonia (CAP) and has been treated with appropriate empiric antibiotics. Most patients with uncomplicated CAP will show improvement in clinical symptoms (fever, cough, dyspnea) within 2 to 3 days; nonresponsive pneumonia is defined as a lack of significant clinical response within 72 hours of initiating therapy. Chest CT or, possibly, high-resolution chest CT is the usual initial radiographic study used to evaluate patients with nonresponsive pneumonia. Compared with plain chest radiography, chest CT provides improved detection of parenchymal abnormalities, including foci of infection such as a lung abscess or cavitary lesions and occult empyema. These findings may help guide additional therapy, or CT may identify other causes of failure to improve that were not previously considered, particularly in a patient whose baseline plain radiograph may be difficult to interpret.

Fiberoptic bronchoscopy with bronchoalveolar lavage and transbronchial biopsy may be helpful in the diagnosis of nonresponsive pneumonia but is typically performed after chest CT, particularly if there are findings (focal areas of fluid collection or consolidation) that help guide bronchoscopic evaluation or lymphadenopathy that may be amenable to bronchoscopic biopsy.

Chest ultrasonography is used primarily to diagnose pleural effusions and guide therapeutic thoracentesis and may be helpful in diagnosing pleural abnormalities such as thickening or nodules. It is less helpful for evaluating the lung parenchyma. This patient has not had evidence of pleural effusions on chest radiography, so the diagnostic yield of chest ultrasonography would be low, particularly compared with chest CT.

More invasive biopsy procedures such as thoracoscopic or open lung biopsy are typically reserved for instances when a specific disorder requiring direct tissue evaluation is needed or if other diagnostic interventions are unrevealing in a patient requiring a diagnosis. Therefore, lung biopsy would not be an appropriate next step before additional imaging.

Key Point

  • Chest CT, which provides improved detection of parenchymal abnormalities, is the usual initial radiographic study used to evaluate patients with nonresponsive pneumonia.

Return to the next case

Case 3

Correct answer: C. Venous duplex ultrasonography of the left thigh.

This patient should undergo venous duplex ultrasonography of the left thigh to evaluate for deep venous thrombosis (DVT) associated with his superficial venous thrombophlebitis (SVT). DVT or pulmonary embolism (PE) develops in up to 3.3% of patients with isolated SVT. The risk increases in patients with SVT of the great or small saphenous vein, with extremity swelling more pronounced than would be expected from the SVT alone, and with progressive symptoms. In these situations, such as with this patient, duplex ultrasonography is indicated to assess for the possibility of an associated DVT.

The effectiveness of low-dose aspirin to treat or prevent propagation of clots in SVT has not been established. Additionally, the use of other anticoagulants for treatment of SVT is controversial. Some evidence indicates that patients with extensive SVT may benefit from a short course of anticoagulant therapy. However, because of a lack of additional data, the specific patients for whom treatment is indicated, the optimal duration of anticoagulation, and the appropriate drug dose and choice are unknown.

D-dimer testing has no utility for differentiating superficial from deep venous thrombosis because levels may be elevated in both conditions. It would, therefore, not be useful in this patient.

Nonextensive SVT, defined as less than 5 cm in length and not near the deep venous system, may be treated with only symptomatic therapy consisting of analgesics, anti-inflammatory medications, and warm or cold compresses for symptom relief, because the risk of progression into the deep venous system and of PE is low.

Key Point

  • Duplex ultrasonography is indicated to assess for the possibility of an associated deep venous thrombosis (DVT) in patients with isolated superficial venous thrombophlebitis (SVT), because DVT or pulmonary embolism risk increases in patients with SVT of the great or small saphenous vein, with extremity swelling more pronounced than would be expected from the SVT alone, and with progressive symptoms.

Return to the next case

Case 4

Correct answer: A. Kidney imaging.

This patient has had a persistent, high fever after 72 hours of appropriate antibiotic therapy; therefore, ultrasonography or contrast-enhanced CT should be performed to exclude an intrarenal or perinephric abscess. Both are acceptable imaging modalities, but CT is considered the gold standard because it offers better anatomic detail. MRI could also be performed to investigate for these complications. Abscess formation is an uncommon complication of urinary tract infection (UTI). The most common predisposing factors for perinephric abscess are diabetes mellitus and the presence of urinary tract calculi. Abscess formation within the kidney usually occurs from infective disruption of the kidney parenchyma secondary to obstruction, frequently by a stone. Perinephric abscesses may result from rupture of an abscess in the corticomedullary region of the kidney through the fascia surrounding the kidney and into the perinephric space. A smaller number of abscesses associated with UTI result from hematogenous spread of bacteria from the highly vascular kidney. Most intrarenal or perinephric abscesses are caused by gram-negative enteric bacilli, whereas gram-positive cocci are generally seen when the abscess occurs secondary to bacteremia. Infection may also be polymicrobial, and fungal organisms such as Candida may be causative in some abscesses. Abscess drainage is usually required except for very small collections or those for which the causative factor (such as a kidney stone) may be removed to allow drainage.

This patient is receiving appropriate therapy for pyelonephritis caused by Escherichia coli, and the isolate is known to be susceptible to ceftriaxone. Therefore, a change in antibiotic to gentamicin, which has significant toxicity, is not indicated, and changing the antibiotic therapy might delay diagnosis of a complication from her UTI.

Repeating the urine culture is not indicated. A culture was performed on admission and has already revealed the causative organism with susceptibility testing. It is highly unlikely that another pathogen would be identified or a resistant E. coli strain would emerge during appropriate and adequate therapy.

Because most patients respond to antibiotic therapy with defervescence within 72 hours, continued observation without any further diagnostic interventions would be inappropriate.

Key Point

  • Patients with pyelonephritis who remain febrile after 72 hours of appropriate antibiotic therapy should undergo kidney ultrasonography, CT, or MRI to investigate for complications, such as perinephric or intrarenal abscess.

Return to the next case

Case 5

Correct answer: C. Cholecystectomy prior to hospital discharge.

The most appropriate management is laparoscopic cholecystectomy prior to hospital discharge. This patient has uncomplicated gallstone pancreatitis in her second trimester. This is very likely her second symptomatic episode of gallstone disease, and cholecystectomy should be performed. Her risk of recurrent pancreatitis over the next 90 days is about 20%. Laparoscopic cholecystectomy can be safely performed during pregnancy, particularly in the second trimester.

Bile acid dissolution therapy for gallstones has not gained widespread acceptance because most patients, such as this one, are candidates for laparoscopic cholecystectomy and few are candidates for bile acid dissolution therapy. Bile acid dissolution therapy is expensive, requires long-term multiple daily dosing, necessitates repeated ultrasonography, and has a potential long-term risk for cancer in the remaining gallbladder. Finally, most nonsurgical therapies for gallstones are contraindicated in pregnant patients. The safety of bile acid therapy in pregnant women is largely unknown.

In a study of pregnant women who had complications related to gallstones during pregnancy, recurrent biliary symptoms, repeated visits to the emergency department, and recurrent hospitalizations were significantly more common in patients who received conservative treatment as compared with women who underwent laparoscopic cholecystectomy or endoscopic retrograde cholangiopancreatography (ERCP). Waiting until after delivery is not the best option for this patient.

ERCP with sphincterotomy could be used, but it should be performed only if this patient had contraindications to cholecystectomy or if there was high clinical suspicion of a persistent common bile duct stone. Neither of these conditions is present in this patient.

Extracorporeal shock-wave lithotripsy (ESWL) is reserved for patients with symptomatic gallstones who are poor candidates for surgery and in those patients with bile duct stones that are refractory to removal at ERCP owing to large size. After ESWL, the gallbladder remains in place and stones recur in about 50% of patients. This patient does not have an indication for ESWL.

Key Point

  • Laparoscopic cholecystectomy can be safely performed during pregnancy, particularly in the second trimester.