POCUS cases from Mayo Clinic

A group of cases involving the use of point-of-care ultrasound.


Case 1: Cardiac tamponade secondary to malignant pericardial effusion

By Corbin Plooster, PA-C; Michael Breunig, PA-C; and Thomas Kingsley, MD, MPH, ACP Member

The patient

A 57-year-old woman with a history of pulmonary embolism and recently diagnosed metastatic lung adenocarcinoma was directly admitted to internal medicine following placement of a pleural drainage catheter for recurrent malignant pleural effusion, complicated by acute hypoxemic respiratory failure, uncontrolled pleuritic chest pain, and dyspnea.

On admission, she was afebrile, tachycardic, tachypneic, normotensive, and hypoxic, requiring 4 L of oxygen via nasal cannula. Physical exam revealed diminished breath sounds over the right lung field but was otherwise unremarkable. Of note, no elevation in jugular venous pressure was documented and heart sounds were normal. Labs were significant for a white blood cell count of 16.6 × 109 cells/L (normal range, 3.4 to 9.6 × 109 cells/L), a sodium level of 133 mmol/L (normal range, 135 to 145 mmol/L), and a potassium level of 6.0 mmol/L (normal range, 3.6 to 5.2 mmol/L). A chest X-ray demonstrated residual moderate right pleural effusion without pneumothorax and an enlarged cardiac silhouette.

Figure 1 Electrocardiogram demonstrating sinus tachycardia with electrical alternans
Figure 1. Electrocardiogram demonstrating sinus tachycardia with electrical alternans.
Figure 2 A parasternal short-axis view on POCUS demonstrating circumferential pericardial effusion white arrow
Figure 2. A parasternal short-axis view on POCUS demonstrating circumferential pericardial effusion (white arrow).

An electrocardiogram showed sinus tachycardia and electrical alternans (Figure 1), prompting a point-of-care ultrasound (POCUS), which revealed a large circumferential pericardial effusion with a swinging heart and right ventricular collapse (Figure 2), raising further concern for cardiac tamponade. Of note, visualization of the inferior vena cava on subxiphoid view with POCUS was obstructed by bowel gas pattern.

An emergent transthoracic echocardiogram confirmed the presence of a large pericardial effusion with tamponade physiology, including right ventricular diastolic collapse, right atrial systolic collapse, and plethoric inferior vena cava. The patient was emergently transferred to the coronary care unit and underwent uncomplicated pericardiocentesis for 500 mL of serosanguineous fluid and placement of a pericardial drain. She ultimately had cardiac arrest and died the following day without evidence of pericardial effusion or cardiac tamponade at time of death.

The diagnosis

The patient's diagnosis is acute cardiac tamponade, secondary to a pericardial effusion, presumed to be malignant in etiology. Malignancies have been shown to cause up to 65% of cases of pericardial tamponade, and presence of tamponade physiology carries a poor prognosis and high mortality. Cardiac tamponade cannot be diagnosed by clinical findings nor echocardiography alone, and detection using only physical exam findings has been shown to be of low sensitivity. In a meta-analysis, Beck's triad symptoms of hypotension, distended neck veins, and muffled heart sounds were present in 28%, 54%, and 22% of pericardial tamponade cases, respectively. The physiology most easily detected by POCUS includes right ventricular collapse and dilated inferior vena cava without variation in size throughout the respiratory cycle. There are limitations to echocardiography and POCUS for this diagnosis, and the presence of a pericardial effusion may be mistaken for cardiac tamponade and thereby lead to inappropriate, invasive management.

Transthoracic echocardiography has traditionally been the study of choice to diagnose pericardial effusion. However, POCUS used by ED physicians has been shown to have a sensitivity of 96% and a specificity of 98%. POCUS has also been shown to both reliably diagnose clinically significant pericardial effusions and cardiac tamponade, as well as decrease time to definitive treatment with pericardiocentesis. If readily available, transthoracic echocardiography should still be pursued if there is diagnostic uncertainty of cardiac tamponade.

Pearls

  • POCUS should always be combined with history, physical exam, and other objective clinical data to aid in the diagnosis of cardiac tamponade.
  • Hospitalists can use POCUS for rapid detection of pericardial effusion and diagnosis of cardiac tamponade, expediting definitive treatment with pericardiocentesis.

Case 2: Complicated parapneumonic effusion

By Michael Breunig, PA-C; Corbin Plooster, PA-C; and Thomas Kingsley, MD, MPH, ACP Member

The patient

A 67-year-old woman with a history of hypertension presented to the ED for evaluation of fever, shortness of breath, and left-sided pleuritic chest pain. She was mildly hypoxic with an oxygen saturation of 87% on room air, and her remaining vital signs were normal. An exam found diminished breath sounds in the left lower lung but was otherwise unremarkable.

Figure 3 A chest X-ray showing consolidation and volume loss of the left lower lobe left pleural effusion and rounded opacity in the left upper lung
Figure 3. A chest X-ray showing consolidation and volume loss of the left lower lobe, left pleural effusion, and rounded opacity in the left upper lung.

Labs showed leukocytosis with a white blood cell count of 13.0 × 109 cells/L (normal range, 3.4 to 9.6 × 109 cells/L) and a normal lactate level. A chest X-ray demonstrated consolidation and volume loss of the left lower lobe, left pleural effusion, and rounded opacity in the left upper lung laterally (Figure 3). Ceftriaxone and azithromycin were started for treatment of community-acquired pneumonia, and the patient was admitted to the general medicine service.

Figure 4 POCUS of the left lung demonstrating a dense left lower lobe consolidation white arrow and a complex left-sided pleural effusion with septations dashed white arrows
Figure 4. POCUS of the left lung demonstrating a dense left lower lobe consolidation (white arrow) and a complex left-sided pleural effusion, with septations (dashed white arrows).

Following admission, the patient developed worsening shortness of breath and increased oxygen requirements. POCUS of the lung was performed and demonstrated a dense left-lower-lobe consolidation and a complex left-sided pleural effusion, concerning for complicated parapneumonic effusion (Figure 4). Antibiotic therapy was broadened to include anaerobic coverage, and the patient underwent urgent chest tube placement with removal of purulent pleural fluid. Video-assisted thoracoscopic decortication surgery was performed during hospitalization. The patient was discharged from the hospital eight days later.

The diagnosis

The diagnosis is complicated parapneumonic effusion. Parapneumonic effusions and empyema are common complications of pneumonia, occurring in approximately 20% to 40% and 5% to 10% of patients hospitalized with pneumonia, respectively. Prompt identification of empyema is important as empiric antibiotic choice varies based on a higher propensity of anaerobic bacteria, and fluid drainage is required.

Although chest X-ray is the standard for diagnosing acute pulmonary pathology, its test characteristics are poor. It has a sensitivity of 51% and a specificity of 91% for the diagnosis of pleural effusion, compared to 94% and 98%, respectively, with POCUS. In the setting of parapneumonic effusion, chest X-ray misses up to 10% of effusions warranting thoracentesis.

Compared to chest CT, X-ray identifies 70% of loculated effusions, while POCUS identifies 94%. As defined by pleural fluid analysis, POCUS has a higher sensitivity than chest X-ray (69.2% vs. 61.5%) and a higher specificity than chest X-ray and CT (90% vs. 60% vs. 65%) for identification of complicated effusions.

The American Association for Thoracic Surgery consensus guidelines for the management of empyema recommend routine use of ultrasound for evaluation of pleural space infections.

Pearls

  • POCUS of the lung performs better than chest X-ray for identification and characterization of pleural effusions and empyema.
  • Routine use of POCUS for evaluation of pleural space infections is recommended by the American Association for Thoracic Surgery.

Case 3: Necrotizing fasciitis

By Michael Breunig, PA-C; Corbin Plooster, PA-C; and Thomas Kingsley, MD, MPH, ACP Member

The patient

A 70-year-old woman with a history significant for type 2 diabetes and left ventricular diastolic heart failure presented with pneumonia and an acute exacerbation of chronic obstructive pulmonary disease (COPD). She was admitted to the ICU due to increased work of breathing and hypercapnia requiring noninvasive positive-pressure ventilation. She was treated with antibiotics, systemic steroids, and inhaled bronchodilators. On hospital day 4, she was transferred to the hospital medicine service following resolution of her hypercapnia and improved work of breathing.

Figure 5 POCUS of the groin showing subcutaneous air as hyperechoic lines black arrows with comet tails white arrows within the soft tissue with posterior acoustic shadowing preventing visualiza
Figure 5. POCUS of the groin showing subcutaneous air as hyperechoic lines (black arrows) with comet tails (white arrows) within the soft tissue, with posterior acoustic shadowing preventing visualization of deep structures.
Figure 6 A CT of the pelvis demonstrating subcutaneous edema extending from the left groin along the anterior and medial aspect of the upper left thigh with a large amount of subcutaneous gas white arrows
Figure 6. A CT of the pelvis demonstrating subcutaneous edema extending from the left groin along the anterior and medial aspect of the upper left thigh with a large amount of subcutaneous gas (white arrows).

The following day, the patient had new-onset tachycardia and increasing leukocytosis from 15.6 × 109 cells/L to 21.8 × 109 cells/L (normal range, 3.4 to 9.6 × 109 cells/L). Physical examination demonstrated a new area of erythema and induration on the left groin. Due to the development of suspected cellulitis, and concern for an underlying abscess, POCUS was completed. It demonstrated findings consistent with subcutaneous air, concerning for necrotizing soft-tissue infection (Figure 5). Emergent surgical consultation was requested, and a CT of the pelvis was obtained, which showed a large amount of subcutaneous gas in the left groin and upper left thigh, consistent with necrotizing fasciitis (Figure 6).

The patient was started on broad-spectrum antibiotics and had emergent operative management with irrigation and debridement. The following day another irrigation and debridement was completed. She was discharged from the hospital eight days later with recommendations for local wound care and a 14-day course of antibiotics.

The diagnosis

This patient's diagnosis is necrotizing fasciitis. Skin and soft-tissue infections (SSTIs), including cellulitis, abscess, and necrotizing fasciitis, are common, with an incidence rate of 24.8 per 1,000 person-years. SSTIs account for approximately 10% of hospitalized patients. However, necrotizing fasciitis is rare, with an incidence rate of 0.04 per 1,000 person-years. Fewer than a third of patients with necrotizing fasciitis are diagnosed correctly at presentation, with 41% being diagnosed with cellulitis instead. Differentiating types of SSTI is difficult given their similar presentations. Pain, erythema, and swelling are common for all types of SSTI, with specific exam findings having limited diagnostic value.

For SSTI, POCUS has a sensitivity and specificity of 97% and 93%, respectively, for identification of abscess, compared to ranges for physical examination of 75% to 95% and 60% to 84%, respectively. POCUS has been shown to change management in up to 50% of patients presenting with SSTI by identifying previously undiagnosed abscesses or avoiding unnecessary irrigation and debridement. Use of POCUS for evaluation and treatment of SSTI decreases time to diagnosis and improves outcomes.

The reported sensitivity and specificity of POCUS for identification of necrotizing fasciitis are good. However, this is based on a small, single-center study with an unusually high rate of necrotizing fasciitis, limiting generalizability. Although literature regarding the use of POCUS in this setting is limited, the finding of subcutaneous air should prompt urgent evaluation for necrotizing fasciitis.

Pearls

  • POCUS can help assess patients with SSTI as it can enhance diagnostic accuracy, change management, and improve outcomes.
  • The role of POCUS in the setting of suspected necrotizing fasciitis remains undefined, but subcutaneous air on ultrasound should prompt urgent evaluation for necrotizing fasciitis.

Case 4: Sepsis secondary to obstructive uropathy

By Michael Breunig, PA-C; Corbin Plooster, PA-C; and Thomas Kingsley, MD, MPH, ACP Member

The patient

An 85-year-old man with a history significant for recent urinary tract infection, atrial fibrillation, and advanced Alzheimer-type dementia presented to the ED for evaluation of fever and rigors. The patient was febrile, tachycardic, and tachypneic but normotensive. He was noted to be diaphoretic and warm to the touch, and the remainder of his examination was unremarkable. Of note, suprapubic tenderness and costovertebral angle tenderness were absent.

Labs demonstrated leukocytosis, with a white blood cell count of 16.2 × 109 cells/L (normal range, 3.4 to 9.6 × 109 cells/L), an elevated creatinine level of 2.2 mg/dL (normal range, 0.74 to 1.35 mg/dL), and an elevated lactate level of 4.06 mmol/L (normal range, 0.5 to 2.2 mmol/L). A chest X-ray did not demonstrate any acute abnormalities. Urinalysis demonstrated gram-negative bacilli and pyuria with more than 100 white blood cells per high-power field.

Figure 7 POCUS of the left kidney demonstrating moderate hydronephrosis white arrow shown by anechoic fluid collection
Figure 7. POCUS of the left kidney demonstrating moderate hydronephrosis (white arrow) shown by anechoic fluid collection.

Cefepime therapy was started based on previous urine culture susceptibilities, and the patient admitted to the hospital for further management. POCUS of the bilateral kidneys demonstrated right-sided nephrolithiasis and left-sided moderate hydronephrosis (Figure 7). Given the POCUS findings, an emergent CT of the abdomen and pelvis was obtained, demonstrating right-sided renal calculus and an obstructing left uretero-vesicular junction stone with upstream hydroureteronephrosis. A left-sided nephrostomy tube was placed with rapid resolution of the patient's sepsis and acute kidney injury.

The diagnosis

The diagnosis is sepsis secondary to obstructive uropathy. Patients with sepsis should receive emergent antibiotics and fluid resuscitation. In addition, identification of a specific site of infection and treatment of the source are paramount.

POCUS can assist with evaluation and diagnosis of patients with sepsis by rapidly identifying specific sources of infection. When compared to standard of care, the addition of a POCUS assessment is associated with a 22% improvement in diagnostic accuracy for identifying the underlying cause of sepsis. POCUS decreases time to diagnosis substantially—a study found that with standard care, 52.8% of diagnoses are made in three hours compared to all diagnoses being determined in 10 minutes with POCUS. In addition, POCUS resulted in more appropriate antibiotic administration, changing the antibiotic regimen in 24% of cases.

Ultrasound is the preferred initial imaging method for patients with suspected obstructive uropathy as it has a high negative predictive value. As an initial modality for suspected nephrolithiasis, POCUS, compared to CT, is not associated with higher rates of missed diagnosis, adverse events, repeat visits to the ED, hospitalizations, or patient pain. However, further imaging for definitive diagnosis and planning of operative management may be required, especially in the setting of a positive ultrasound.

Pearls

  • POCUS can aid in the evaluation of patients with sepsis by rapidly identifying the underlying causative infection, resulting in more appropriate antibiotic regimen.
  • POCUS should be considered the preferred initial imaging modality for patients with suspected obstructive uropathy, given its quick time to diagnosis and high negative predictive value.

Case 5: Acute pulmonary edema

By Corbin Plooster, PA-C; Michael Breunig, PA-C; and Thomas Kingsley, MD, MPH, ACP Member

The patient

A 73-year-old woman with a history significant for type 2 diabetes, hypertension, and hyperlipidemia presented to the ED with acute vomiting, diarrhea, and unwitnessed syncope with a fall. She underwent a CT of the head and a CT angiogram of the chest, abdomen, and pelvis, which revealed a T2 compression fracture, a nondisplaced left first-rib fracture, and a displaced fracture of the right fifth metacarpal. No pulmonary embolism was detected. The patient's vital signs were within normal limits. Her lactate level was 3.4 mmol/L (normal range, 0.5 to 2.20 mmol/L), which was suspected to be secondary to hypovolemia. She was admitted and volume resuscitated with 3 L of IV fluids overnight.

The following morning the patient developed acute dyspnea and respiratory failure. Her respiratory status declined, requiring 10 L of oxygen by simple face mask, and the rapid response team was activated. Physical exam demonstrated moderate respiratory distress, tachypnea, and scattered rales with auscultation. An arterial blood gas was consistent with acute metabolic acidosis with a normal partial pressure of carbon dioxide. POCUS revealed sonographic B lines throughout the bilateral lung fields, consistent with acute pulmonary edema. The patient was treated with furosemide, 40 mg IV, with subsequent improvement in her respiratory status over the next six hours. A chest X-ray obtained 30 minutes after POCUS demonstrated bilateral interstitial opacities consistent with pulmonary edema, as well as cardiomegaly. A transthoracic echocardiogram was suggestive of acute-on-chronic diastolic heart failure.

The diagnosis

The diagnosis is acute pulmonary edema, secondary to acute exacerbation of diastolic heart failure. Pulmonary edema is an abnormal increase in extravascular fluid secondary to increased hydrostatic pressure in the pulmonary circulation, often due to congestive heart failure or intravascular volume overload. The signs and symptoms of acute pulmonary edema, such as acute dyspnea, presence of rales on physical exam, and hypoxemic respiratory failure, are nonspecific and associated with a broad differential diagnosis. This presents a diagnostic challenge, especially given limitations in the conventional evaluation strategies. POCUS of the chest has been shown to be comparable to or superior to chest X-ray in this setting. Two meta-analyses of patients diagnosed with cardiogenic pulmonary edema found lung ultrasonography to be superior in sensitivity compared to chest X-ray (85% to 88% vs. 57% to 73%) and comparable in specificity (90% to 92% vs. 89% to 90%).

When combined with history and physical exam, POCUS of the lung can assist in rapidly diagnosing pulmonary pathology. A study of patients presenting to the ED with acute dyspnea found that a blinded POCUS exam resulted in a time to diagnosis of 24 minutes, whereas diagnosis using chest X-ray, CT, or transthoracic echocardiogram as indicated took 186 minutes.

Pearls

  • POCUS of the lung is more sensitive than and as specific as chest X-ray in the evaluation of acute pulmonary edema.
  • When combined with history and physical exam, POCUS of the lung can lead to rapid and accurate diagnosis of this condition.

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