Introduction
Acute Renal Failure (ARF), also known as Acute Kidney Injury (AKI), happens when the kidneys suddenly lose their ability to filter waste products from the blood. This leads to the rapid build-up of nitrogenous wastes and disturbance in fluid and electrolyte balance. AKI develops within a few hours or days and is common in hospitalized and critically ill patients.
Epidemiology
- Seen in 3–7% of hospitalized patients.
- Occurs in about 25–30% of ICU patients.
Causes of Acute Renal Failure
1) Reduced Blood Flow to Kidneys (Prerenal Causes)
- Blood or fluid loss
- Heart attack or heart disease
- Severe dehydration
- Infection or sepsis
- Liver failure
- Severe allergic reaction (anaphylaxis)
- NSAIDs (aspirin, ibuprofen, naproxen)
- Severe burns
2) Direct Damage to the Kidneys (Intrinsic Causes)
- Blood clots in kidney vessels
- Cholesterol emboli
- Glomerulonephritis
- Hemolytic uremic syndrome
- Lupus nephritis
- Nephrotoxic drugs (chemotherapy, antibiotics, contrast dye)
- Multiple myeloma
- Scleroderma
- Toxins (alcohol, heavy metals, cocaine)
- Vasculitis
3) Obstruction of Urine Flow (Postrenal Causes)
- Bladder cancer
- Blood clots in urinary tract
- Cervical or colon cancer
- Enlarged prostate
- Kidney stones
- Nerve damage affecting bladder
- Prostate cancer
Etiologic Mechanisms in Acute Renal Failure
Prerenal Failure
Mechanism: Reduced renal blood flow.
- Severe dehydration or shock
- Cardiac failure
- Renal artery stenosis
- Renal artery embolism
- Sickle cell crisis
Intrarenal Failure
Mechanism: Damage to renal parenchyma.
- Ischemic necrosis
- Nephrotoxicity
- Autoimmune disorders
- Hypertensive nephropathy
- Diabetic nephropathy
- Renal trauma
- Glomerulonephritis
- Vasculitis
- Acute interstitial nephritis
- Rhabdomyolysis
Postrenal Failure
Mechanism: Obstruction preventing urine filtration.
- Urolithiasis
- Renal tumors
- Congenital obstructive defects
- Ureter injury
- Lymphatic obstruction
Risk Factors
- Hospitalization, especially ICU care
- Older age
- Peripheral artery disease
- Diabetes
- High blood pressure
- Heart failure
- Chronic kidney disease
- Liver diseases
Pathophysiology of Acute Renal Failure
The main driving force for filtration is the pressure gradient between the glomerulus and Bowman’s capsule. This depends on renal blood flow and the resistance of afferent and efferent arterioles.
All types of AKI share a common mechanism: reduced renal blood flow leading to decreased GFR.
- Prerenal AKI: Reduced perfusion → low GFR, normal tubules.
- Intrinsic AKI: Direct kidney tissue damage (most commonly ischemia).
- Postrenal AKI: Obstruction increases tubular pressure → reduced GFR.
Symptoms of Acute Renal Failure
- Reduced urine output
- Swelling of legs, ankles and feet
- Drowsiness
- Shortness of breath
- Fatigue
- Confusion
- Nausea
- Seizures or coma in severe cases
- Chest pain or pressure
Complications of Acute Renal Failure
- Fluid accumulation in lungs (pulmonary edema)
- Chest pain due to pericarditis
- Muscle weakness due to electrolyte imbalance
- Permanent kidney damage (end-stage kidney disease)
- Death in severe cases
Diagnosis of Acute Renal Failure
- Urine output: Helps determine cause.
- Urine tests: Detect abnormalities.
- Blood tests: Check rising urea and creatinine.
- Imaging tests: Ultrasound, CT scan.
- Kidney biopsy: Used in selected cases.
Treatment of Acute Renal Failure
- Fluid balance: IV fluids or diuretics as required.
- Control potassium: Calcium, glucose, sodium polystyrene sulfonate.
- Treat low calcium: Calcium infusion.
- Treat end-stage kidney disease: Dialysis or kidney transplant.
Dialysis
Hemodialysis removes waste using a machine. Peritoneal dialysis uses dialysis fluid inside abdominal cavity.
Kidney Transplant
Healthy kidney from donor; lifelong immunosuppressive drugs required.
Prevention
- Regular check-ups with blood and urine tests
- Stay hydrated
- Avoid nephrotoxic drugs
- Control diabetes and hypertension
- Manage kidney-related risk factors
Chronic Renal Failure (Chronic Kidney Disease)
Introduction
Chronic Kidney Disease (CKD) is the irreversible loss of kidney function over months or years. As healthy nephrons are replaced by scar tissue, the kidneys gradually lose their ability to filter waste and regulate fluid, electrolytes and hormones.
CKD progresses slowly and may not show symptoms until significant kidney damage has occurred. End-stage renal disease requires dialysis or kidney transplant.
Causes of Chronic Renal Failure
- Type 1 and Type 2 diabetes
- High blood pressure
- IgA nephropathy
- Repeated kidney infections (pyelonephritis)
- Polycystic kidney disease
- Long-term urinary obstruction (stones, enlarged prostate, cancers)
- Autoimmune diseases (lupus)
- Atherosclerosis
- Vesicoureteral reflux
- Overuse of nephrotoxic medicines
Pathophysiology of Chronic Renal Failure
A normal kidney has about 1 million nephrons. When nephron loss begins, remaining nephrons enlarge (hypertrophy) and work harder (hyperfiltration) to maintain GFR.
Waste products (urea, creatinine) increase only when GFR drops below 50%. Plasma creatinine doubles when GFR halves.
Over time, increased glomerular pressure damages capillaries → focal segmental glomerulosclerosis → global glomerulosclerosis → progressive renal failure.
Symptoms of Chronic Renal Failure
- Nausea and vomiting
- Loss of appetite
- Fatigue and weakness
- Sleep problems
- Urine output changes
- Reduced concentration
- Muscle twitching
- Hiccups
- Swollen feet and ankles
- Persistent itching
- Chest pain (fluid around heart)
- Shortness of breath (fluid in lungs)
- High blood pressure
Diagnosis of Chronic Renal Failure
- Blood tests: Creatinine and urea levels.
- Urine tests: Detect protein or RBC leakage.
Treatment
- Dialysis
- Kidney transplant
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