In an 89-year-old woman with a fluid-like lung sound on auscultation, what is the most likely cause and what initial diagnostic and treatment steps should be taken?

Fluid-Like Lung Sounds in an 89-Year-Old Woman

Most Likely Diagnosis

The fluid-like lung sounds you are hearing are most likely fine crackles (rales) indicating acute pulmonary edema from heart failure, which is the most common cause of this finding in elderly patients. 1, 2

Immediate Clinical Assessment

Perform a focused physical examination to distinguish between fluid overload and infection:

• Check vital signs immediately: oxygen saturation, heart rate, blood pressure, respiratory rate, and temperature 2
• Assess for heart failure signs: elevated jugular venous pressure, hepatomegaly, peripheral edema, and S3 gallop 3, 1
• Document crackle distribution: bilateral basilar crackles progressing upward suggest heart failure, while unilateral or focal crackles suggest pneumonia 2, 4
• Have the patient cough: persistent rales after coughing are more clinically significant for acute heart failure 2
• Look for infection signs: fever, productive cough, and unilateral findings point toward pneumonia rather than heart failure 3, 2

Critical Diagnostic Steps

Obtain a chest radiograph immediately to differentiate between pulmonary edema (showing cardiomegaly, pulmonary venous congestion, peri-bronchial cuffing, pleural effusion) versus pneumonia (showing infiltrates) versus other causes 3, 1, 2

If heart failure is suspected based on bilateral basilar crackles and signs of fluid overload:

• Measure B-type natriuretic peptide (BNP or NT-proBNP): use cutoff of 100 pg/mL for BNP or 300 pg/mL for NT-proBNP 1, 2
• Perform echocardiography to assess left ventricular function and filling pressures 2
• Consider lung ultrasound if available, as it has superior diagnostic accuracy (94% sensitivity, 92% specificity) compared to auscultation for detecting pulmonary edema 1, 2

If pneumonia is suspected based on fever, unilateral findings, or productive cough:

• Obtain sputum Gram stain and culture 2
• Consider blood cultures if hospitalization is required 2

Oxygen Management

Initiate oxygen therapy immediately if oxygen saturation is <95%, with a goal of maintaining saturation ≥92% 2

Common Pitfalls to Avoid

• Do not rely solely on auscultation: the absence of crackles does not rule out significant pulmonary edema, as pronounced pulmonary edema can be present without auscultatory signs 1, 2
• Lung auscultation has limited sensitivity (only 37% pooled sensitivity despite 89% specificity), so always confirm with imaging 4
• Remember that crackles are non-specific: similar sounds occur in pneumonia, interstitial lung diseases, and pulmonary fibrosis 1, 4

Age-Specific Considerations

In elderly patients like this 89-year-old woman:

• Pneumonia may present atypically with confusion, failure to thrive, worsening of chronic illness, or falls rather than classic respiratory symptoms 3
• Fever may be absent in pneumonia, but tachypnea is usually present along with abnormal chest examination 3
• Heart failure is extremely common in this age group and should be the primary consideration with bilateral basilar crackles 1, 2