33.2 Renal-Associated Fluid Volume Excess

Renal system dysfunction can wreak havoc on your body's fluid balance. When your kidneys aren't working right, they struggle to filter fluids properly, leading to a buildup of excess fluid in your body.

This fluid overload can cause all sorts of problems, from swollen ankles to shortness of breath. We'll look at the symptoms, causes, and tests for renal-related fluid volume excess, so you can spot the signs and understand what's going on in your body.

Renal System Dysfunction and Fluid Volume Excess

Renal dysfunction impairs fluid balance

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Top images from around the web for Renal dysfunction impairs fluid balance

• 

  Physiology of the Kidneys | Boundless Anatomy and Physiology View original

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• 

  The Urinary System and Homeostasis – Water and Electrolyte balance. | BIO103: Human Biology View original

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• 

  Renal physiology - wikidoc View original

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  Physiology of the Kidneys | Boundless Anatomy and Physiology View original

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  The Urinary System and Homeostasis – Water and Electrolyte balance. | BIO103: Human Biology View original

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• Reduced glomerular filtration rate (GFR) decreases fluid filtration in the kidneys
• Impaired tubular reabsorption and secretion disrupt the balance of fluid reabsorption and excretion leading to fluid imbalance (hypovolemia or hypervolemia)
• Renal dysfunction causes sodium and water retention
  • Decreased sodium excretion increases osmolarity of extracellular fluid triggering thirst and increased fluid intake (polydipsia)
  • Antidiuretic hormone (ADH) secretion increases promoting water retention in the collecting ducts of the nephrons
• Renal dysfunction leads to decreased urine output (oliguria) or absence of urine output (anuria) causing fluid accumulation in the body

Symptoms and signs of renal-related fluid volume excess

• Edema
  • Swelling in the extremities particularly in the legs, ankles, and feet due to fluid accumulation in the interstitial spaces
  • Facial swelling especially around the eyes (periorbital edema)
  • Generalized edema or anasarca which is severe, widespread edema throughout the body
• Weight gain due to fluid retention as the body retains excess water and sodium
• Shortness of breath or dyspnea
  • Fluid accumulation in the lungs (pulmonary edema) causes difficulty breathing and decreased oxygenation
• Elevated blood pressure (hypertension) as fluid overload increases blood volume and pressure in the cardiovascular system
• Jugular venous distension (JVD) is visible distension of the jugular veins in the neck due to increased central venous pressure from fluid overload
• Crackles or rales upon lung auscultation indicate fluid accumulation in the alveoli and interstitial spaces of the lungs (pulmonary edema)

Causes and diagnostic tests for renal fluid volume excess

• Common causes
  1. Acute kidney injury (AKI) due to ischemia, nephrotoxins, or obstruction
  2. Chronic kidney disease (CKD) from diabetes, hypertension, or glomerulonephritis
  3. Nephrotic syndrome characterized by heavy proteinuria, hypoalbuminemia, and edema
  4. Glomerulonephritis causing inflammation and damage to the glomeruli
  5. Renal artery stenosis leading to decreased renal perfusion and activation of the renin-angiotensin-aldosterone system (RAAS)
• Diagnostic tests
  • Serum creatinine and ###blood_urea_nitrogen_(BUN)_0### levels are elevated indicating impaired renal function and decreased clearance of waste products
  • Urinalysis assesses urine concentration, protein (proteinuria), and presence of blood (hematuria) or other abnormalities (casts)
  • Urine output monitoring detects oliguria (<400 mL/day) or anuria (<100 mL/day) suggesting fluid retention
  • Imaging studies like renal ultrasound or CT scan assess kidney structure and rule out obstruction (hydronephrosis)
  • Echocardiography evaluates cardiac function and presence of pulmonary edema from fluid overload
  • Pulmonary function tests like spirometry assess lung function and presence of fluid in the lungs impairing ventilation