Laboratory Tests for Patients Presenting with Generalized Swelling
The initial laboratory evaluation for patients with generalized swelling should include complete blood count, urinalysis, serum electrolytes, blood urea nitrogen, serum creatinine, liver function tests, and thyroid-stimulating hormone. 1
Core Laboratory Tests
- Complete blood count (CBC) - Evaluates for anemia which may contribute to high-output heart failure and assesses for hematologic disorders 1
- Serum electrolytes - Identifies electrolyte imbalances that commonly accompany edema, including sodium, potassium, calcium, and magnesium 1
- Blood urea nitrogen (BUN) and serum creatinine - Essential for evaluating kidney function and detecting acute kidney injury or chronic kidney disease 1, 2
- Urinalysis - Assesses for proteinuria, hematuria, and other abnormalities that may indicate renal disease 1, 3
- Liver function tests - Evaluates for liver disease which can cause hypoalbuminemia and subsequent edema 1, 4
- Serum albumin and total protein - Low levels may indicate protein-losing conditions, malnutrition, or liver disease leading to decreased oncotic pressure 1, 5
- Thyroid-stimulating hormone (TSH) - Rules out hypothyroidism as a cause of generalized edema 1
Additional Tests Based on Clinical Suspicion
For Suspected Cardiac Etiology
- Brain natriuretic peptide (BNP) or NT-proBNP - Evaluates for heart failure 1
- Electrocardiogram (ECG) - Assesses for cardiac abnormalities 1
- Chest radiograph - Evaluates for pulmonary congestion, cardiomegaly, and pleural effusions 1
- Echocardiography - Indicated if heart failure is suspected based on elevated BNP/NT-proBNP or clinical findings 1
For Suspected Renal Etiology
- Urine protein-to-creatinine ratio - Quantifies proteinuria 3
- Fractional excretion of sodium - Helps differentiate between prerenal, intrinsic renal, and postrenal causes of acute kidney injury 2
- Renal ultrasound - Evaluates kidney size, echogenicity, and rules out obstruction 2
For Suspected Hepatic Etiology
- Serum albumin - Low levels suggest decreased hepatic synthesis 4
- Prothrombin time - Prolongation indicates impaired hepatic synthetic function 4
- Abdominal ultrasound - Evaluates for ascites, splenomegaly, and portal hypertension 4
Special Considerations
- Medication review - Evaluate for medications that can cause edema, such as calcium channel blockers, NSAIDs, thiazolidinediones, and hormonal therapies 1
- In pregnant patients - Consider preeclampsia workup including liver enzymes and platelet count if edema is accompanied by hypertension 5
- In pediatric patients - Consider additional causes such as congenital anomalies or malignancies depending on the pattern and progression of swelling 6
- In patients with malignancy - Evaluate for tumor lysis syndrome with uric acid, phosphate, calcium, and potassium levels 7
Common Pitfalls to Avoid
- Not checking TSH - Hypothyroidism is a reversible cause of generalized edema that can be easily missed 1
- Focusing only on cardiac causes - Multisystem evaluation is essential as edema can result from cardiac, renal, hepatic, or endocrine disorders 1
- Neglecting medication review - Many commonly prescribed medications can cause or exacerbate edema 1
- Missing protein abnormalities - Low serum protein levels can be an early warning sign of significant pathology 5