Conditions · Nephrology and urology
Fluid volume overload (hypervolaemia) !
Fluid volume overload means the body holds too much salt and water, causing swelling, weight gain and, when severe, fluid in the lungs.
Updated 2026-11-01
Structures involved
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- Kidneys
- Inferior vena cava
- Left ventricle
- Right ventricle
- Superior vena cava
- Internal jugular vein
- Pleura
- Liver
In the clinical exam
Why it happens
- Edema and effusions: the four mechanisms
- Dehydration and fluid overload
- The renin–angiotensin–aldosterone system
- Starling forces at the capillary
- Sodium and extracellular volume regulation (with natriuretic peptides)
- Physiology of pulmonary edema
What it is
An excess of isotonic fluid (sodium and water together) in the extracellular space, both in the blood vessels and in the tissues. It is a clinical state and a core nursing diagnosis rather than a single disease: it reflects heart, kidney or liver failure, or more fluid and sodium given than the body can excrete.
Who gets it
Very common in hospitals, especially in older adults, people with heart failure or chronic kidney disease, patients on dialysis and patients receiving intravenous fluids or blood products. In Colombia and Latin America, the high burden of heart failure, hypertension, diabetes and chronic kidney disease makes it a daily problem on medical wards and in emergency departments.
Causes
- Heart failure: low cardiac output triggers renal sodium and water retention
- Acute kidney injury or chronic kidney disease, including missed dialysis sessions
- Liver cirrhosis with ascites, and nephrotic syndrome (low albumin plus sodium retention)
- Excess intravenous fluids or rapid infusion of sodium-containing solutions
- Transfusion-associated circulatory overload (TACO) after blood products
- High dietary salt intake in a person with heart or kidney disease
- Medicines that retain sodium: glucocorticoids, NSAIDs, some calcium channel blockers and thiazolidinediones
Risk factors
- Age over 65 and low body weight
- Heart failure, chronic kidney disease, dialysis or cirrhosis
- Large-volume or fast intravenous fluid and blood transfusion
- Pregnancy with pre-eclampsia
- Poor adherence to salt or fluid restriction or to diuretics
Pathophysiology
When the kidneys sense low effective circulating volume (failing heart, low albumin, splanchnic vasodilation) or cannot excrete sodium (kidney failure), the renin-angiotensin-aldosterone system and antidiuretic hormone retain sodium and water. Venous and capillary hydrostatic pressures rise, so fluid moves into the interstitium as oedema, into the alveoli as pulmonary oedema and into serous cavities as effusions or ascites. Because sodium and water are gained together, serum sodium is often normal, although it can be diluted (low) when water is retained in excess.
Symptoms and signs
- Rapid weight gain over days (the most sensitive bedside sign)
- Pitting oedema of the ankles and legs, or of the sacrum in bedridden patients
- Shortness of breath, orthopnoea and crackles in the lungs
- Distended neck veins and a positive hepatojugular reflux
- High blood pressure and a bounding pulse
- Ascites, pleural effusion, or generalised swelling (anasarca)
- Intake greater than output on the fluid balance chart
Diagnosis
- Clinical
- Daily weight on the same scale, intake and output, oedema, jugular venous pressure, lung crackles, respiratory rate and oxygen saturation. Look for the cause: heart, kidney and liver history, recent fluids or transfusions, salt intake and medicines.
- Tests
- Serum sodium, potassium, urea and creatinine; albumin and liver tests; natriuretic peptides (BNP or NT-proBNP) for heart failure; urinalysis and urine protein; arterial blood gas when breathless. Haematocrit may be low from dilution.
- Imaging
- Chest X-ray (vascular congestion, interstitial oedema, Kerley B lines, effusions); point-of-care ultrasound of the lungs (B lines) and inferior vena cava (wide, non-collapsing); echocardiography for heart function.
Differential diagnosis
- Localised oedema from deep vein thrombosis, venous insufficiency or lymphoedema
- Hypoalbuminaemia from malnutrition without true sodium excess
- Pneumonia or acute respiratory distress syndrome (non-cardiogenic lung infiltrates)
- Drug-induced oedema (calcium channel blockers) with normal circulating volume
- Hypothyroidism (myxoedema)
Goal of treatment
Remove excess sodium and water safely, restore normal breathing and oxygenation, treat the underlying cause and avoid overcorrection into dehydration, kidney injury or electrolyte disorders.
Treatment
- Acute
- Acute pulmonary oedema: sit the patient upright, give oxygen, stop or slow intravenous fluids or transfusion, and start an intravenous loop diuretic; vasodilators (nitrates) and non-invasive ventilation in selected cases.
- Medical
- Loop diuretics are first-line; thiazides or mineralocorticoid antagonists are added for resistance or for cirrhosis. Treat the cause: heart failure therapy, cirrhosis care, nephrotic syndrome treatment.
- Procedure
- Dialysis or ultrafiltration when diuretics fail or the kidneys do not work; therapeutic paracentesis for tense ascites and thoracentesis for large effusions.
- Lifestyle
- Sodium restriction, and fluid restriction when serum sodium is low or in dialysis patients; review medicines that retain salt.
- Follow-up
- Nursing care: daily weight, strict intake and output, vital signs, lung sounds and oxygen saturation, oedema and skin care with repositioning, head of bed raised, and potassium, sodium and creatinine during diuresis.
Complications
- Acute pulmonary oedema and respiratory failure
- Pleural effusion and ascites
- Skin breakdown and pressure injury over oedematous areas
- Dilutional hyponatraemia
- Electrolyte disorders and kidney injury from aggressive diuresis
- Worsening heart failure
Prognosis
It usually responds within hours to days to diuresis and correction of the cause. The outlook depends on the underlying disease: repeated episodes in heart failure or kidney failure signal advanced disease and higher mortality.
Prevention
- Calculated, regularly reviewed intravenous fluid prescriptions, especially in older adults
- Slower transfusion and monitoring in people at risk of TACO
- Salt restriction, diuretic adherence and daily home weights in heart failure
- Keeping dialysis sessions and fluid limits
Test yourself
Think of the answer, then tap the question to see it.
What is the most sensitive bedside measure of a change in fluid volume?
Daily weight on the same scale at the same time; a rapid gain over a few days reflects retained fluid.
Which physical signs suggest fluid volume overload?
Pitting oedema, distended neck veins, lung crackles, hypertension, bounding pulse and weight gain.
What is the first nursing action for a patient who becomes acutely breathless during an infusion?
Stop or slow the infusion, sit the patient upright, give oxygen and alert the medical team.
Which drug class is first-line to remove excess fluid?
Loop diuretics.
What is TACO?
Transfusion-associated circulatory overload: pulmonary oedema from too much or too fast transfusion, typically with hypertension.
Related conditions
- Heart failure
- Acute kidney injury
- Chronic kidney disease
- Cirrhosis
- Nephrotic syndrome
- Transfusion reactions
- Pleural effusion
- Preeclampsia
- Hyponatraemia
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Fluid imbalance: MedlinePlus Medical Encyclopedia (MedlinePlus (U.S. National Library of Medicine), 2025).
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Representative model, for educational purposes only.
