Renal failure (kidney failure, also referred to as end-stage renal disease) is a condition characterized by the insufficient functioning of the kidneys, which may occur suddenly due to acute kidney injury or develop gradually as the chronic kidney disease.
The kidneys play an essential role in the body, therefore, renal failure is a life-threatening condition that can occur suddenly when certain factors cause acute kidney injury or develop gradually due to various chronic damage. Acute kidney injury (in the past known as acute kidney failure) defines a condition when renal function is drastically and abruptly impaired and urine volume is significantly reduced. However, in general acute kidney injury has a favorable prognosis unless it is complicated. Chronic kidney disease (previously chronic renal failure) is a term used to define decreased renal function with glomerular filtration rate of fewer than 60 ml/min/1,73m2 for at least 3 months.
Impaired kidney function leads to the accumulation of waste products (which are normally excreted in urine) in the body, fluid overload, protein loss, and acid base imbalance – the symptoms and signs of renal failure are collectively known as uremia. Of note, for a long time person remain asymptomatic and may not know about the gradually developing disorder until eventually irreversible end-stage renal disease develops.
Acute kidney injury
Different factors may influence the kidney and cause acute kidney injury.
- Pre-renal factors damaging the kidneys include collapse, hemorrhage, severe dehydration, pancreatitis, burns, trauma, and peritonitis. These disorders impair the kidneys blood perfusion and, therefore, kidneys sustain damage;
- Renal type acute kidney injury occurs in the case of sepsis, sarcoidosis, multiple myeloma, renal vein thrombosis, renal infarction, hemolytic-uremic syndrome, rhabdomyolysis, systemic vasculitis, lupus erythematosus, etc. Nephrotoxic drugs such as NSAIDs, aminoglycosides, cisplatin, methotrexate, penicillins, PPIs may cause acute kidney injury;
- Postrenal factors cause acute kidney injury infrequently. This type of damage occurs when the urine outflow from both kidneys or one functioning kidney is obstructed due to urethral obstruction, bladder dysfunction/obstruction, and obstruction of both ureters or renal pelvises.
Acute kidney injury may have different severity:
- Stage 1 – 1.0-1.5-fold increase in serum creatinine or a decline in urinary output to 0.5 ml/kg/h over 6-12 hours;
- Stage 2 – 2.0-2.9-fold increase in serum creatinine or a decline in urinary output to 0.5 ml/kg/h over 12 hours or longer;
- Stage 3- 3-fold or greater increase in serum creatinine or decline in urinary output to 0.3 ml/kg/h for 24 hours or longer or absence of urine for 12 hours or longer;
Chronic kidney disease
In chronic kidney disease renal function declines gradually due to various chronic disorders that affect the kidneys:
- Hypertension-related nephrosclerosis or kidney damage due to another vascular disease;
- Diabetic nephropathy;
- Chronic glomerulonephritis;
- Renal amyloidosis;
- Polycystic kidney disease;
- Medullary cystic disease;
- Renal artery stenosis;
- Tubulointerstitial nephritis due to heavy metals poisoning, drug hypersensitivity, sickle cell disease;
- Collagen-vascular diseases;
- Other chronic diseases affecting the kidneys;
The kidney tissues are progressively damaged and connective tissue substitutes the injured cells until the kidney function is severely impaired (end-stage kidney disease).
Stage of the chronic kidney disease is evaluated according to the glomerular filtration rate – the speed of plasma filtration in the kidneys which is the first step of urine production.
- Stage 1 – GFR normal or high – more than 90 ml/min per 1,73 m2;
- Stage 2 – GFR mildly decreased – 60-89 ml/min per 1,73 m2;
- Stage 3 – GFR moderately to severely decreased – 30-59 ml/min per 1,73 m2;
- Stage 4 – GFR severely decreased – 15-29 ml/min per 1,73 m2;
- Stage 5 – kidney failure with GFR of less than 15 ml/min per 1,73 m2;
Initially the kidney function is apparent only based on the laboratory studies results which revealed raised urea and creatinine concentrations in blood. Usually, symptoms of chronic kidney disease develop when renal function is severely impaired and the GFR is below 30 ml/min/1,73 m2, although then almost all of the body systems and organs are involved. Relatively early occurs nocturia – excessive urination at night, which generally means that a person wakes up several times at night for voiding.
Renal failure symptoms
A person usually has pale skin with excoriations due to itching and easy bruising. Other symptoms of the disease include tiredness and fatigue, muscle weakness, headaches, breathlessness, poor appetite, nausea, vomiting, hiccups and a metallic taste in the mouth. Foul breath and unpleasant sweat odor may also be noticed as the urea is excreted through the skin by the sweat and saliva. Lower back pain in the region where the kidneys are located may also develop.
The excessive fluid which accumulates in the body causes swelling or puffiness around the eyes, arms, hands, and feet. In extremely severe cases, fluid leaks into the peritoneal cavity causing ascites (accumulation of the fluid in the abdomen), into the pleural cavity causing hydrothorax (accumulation of the fluid in the cavity around the lungs) or into the pericardium (fluid accumulates around the heart). In acute renal failure urine volume is significantly reduced (oliguria) or urine production may be ceased at all (anuria).
Toxic substances in the blood also affect the nervous system – a person is irritable, experiences seizures, muscle cramps, memory loss and inability to concentrate. Confusion and coma may also eventually develop. This condition is known as uremia.
Maintainance of a low-protein diet (0,58 g/kg/day) is recommended in order to reduce the production of waste products. Salt intake should also be restricted.
Treatment of acute kidney injury depends on the underlying cause. In addition, acid-base balance, as well as water and electrolyte balance, should be restored.
Chronic kidney disease also requires the administration of antihypertensive medications to control blood pressure and erythropoesis-stimulating agent to increase red blood cell count.
Renal replacement therapy
Renal replacement therapy (hemodyalisis, peritoneal dialysis, hemofiltration) should be considered in the case of:
- Low blood pH (metabolic acidosis);
- Severe hyperkalemia (high blood potassium levels) resistant to drugs;
- Fluid overload;
- Acute poisoning (with salicylic acid, ethanol, methanol, barbiturates, lithium, isopropanol, magnesium-containing laxatives, and ethylene glycol);
- Serositis (pericarditis, pleuritis) or encephalopathy due to uremia;
- Chronic kidney disease with GFR of less than 10-15 ml/min/1.73 m2;