What Is Azotemia?
Azotemia is defined as the biochemical abnormality characterized by elevated blood urea nitrogen levels, serum creatinine levels as well as other secondary waste products in the body.
What Are the Types of Azotemia?
There are three types of azotemia, that includes,
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Prerenal Azotemia- It is caused due to the decreased blood flow to the kidneys as a result of damage or injury to the components supplying the kidneys.
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Intrinsic Azotemia- It is caused as a result of damage to the structures within the kidney, such as damage to the glomeruli, renal tubules, interstitium, and the blood vessels of the kidneys.
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Post-renal Azotemia- It is caused due to any obstruction or damage to the ureter and the urinary bladder.
What Is the Epidemiology of Azotemia?
Studies suggest that the incidence of azotemia is quite common in patients with kidney diseases and other associated conditions. It accounts for 8 to 16 % of hospital admissions and has a high risk of mortality.
What Is the Etiology of Prerenal Azotemia?
Prerenal azotemia manifests as a result of hypoperfusion (reduced amount of blood flow) to the kidneys, the etiologies that lead to decreased renal blood flow include,
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Dehydration - It is the increased fluid loss from the body resulting in decreased blood flow to the kidneys.
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Shock - This is a life-threatening condition characterized by a sudden drop in blood flow to the organs in the body.
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Burns - Burns would result in hypovolemic shock as a result of increased loss of fluid from the body.
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Hemorrhage - It is bleeding inside the body due to damaged blood vessels.
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Overdiuresis - This is characterized by excessive urination due to the kidney's hyperfiltration activity.
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Congestive Heart failure - Blood flow to the heart is decreased, resulting in low cardiac output, thereby reducing blood flow to the kidneys.
What Is the Etiology of Intrinsic Azotemia?
It is caused as a result of damage to the structures within the kidneys; it includes,
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Infections - From various sources or originating within the kidneys can damage the structures of the kidney.
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Renal Vasculitis - This is an autoimmune inflammatory condition in which antibodies are directed against the glomeruli and the small blood vessels in the kidney.
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Toxins - Toxins such as pesticides, fertilizers, and exposure to heavy metals like cadmium, lead, etc., can cause damage to kidney structures.
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Drugs - Certain drugs like Cocaine, Heroin, and Amphetamines cause kidney damage.
What Is the Etiology of Post-renal Azotemia?
It is caused as a result of any obstruction to the ureter or bladder, that includes,
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Renal Stones - Calculi or stones in the ureter or bladder may serve as a secondary cause of kidney damage.
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Benign Prostatic Hyperplasia - It is the enlargement of the prostate gland in men, causing pressure or obstruction to the urinary bladder.
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Hydronephrosis - It can be due to any blockage in the ureters, causing swelling of one or both kidneys.
What Is the Pathogenesis of Azotemia?
The main pathogenesis behind all three types of azotemia is the decreased blood flow and oxygenation to the kidney as a result of various etiological factors that will result in acute kidney injury. The kidney is very sensitive to changes such as hypoxia (decreased oxygen supply) and hypoperfusion (decreased blood flow) as it receives 25 % of cardiac output in the body. Any sudden or chronic reduction in the oxygen or blood supply would definitely damage the components as well as the functional ability of the kidneys. Thereby affecting the filtration rate of the kidneys, causing accumulation of nitrogenous waste products, creatinine, and other waste products in the kidneys and subsequently increasing their levels in the blood.
What Are the Symptoms of Azotemia?
The symptoms are mainly attributed to the signs of kidney damage or renal failure, and that includes,
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Tiredness.
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Chills.
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Nausea.
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Vomiting.
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Delirium.
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Shortness of breath.
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Weakness.
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Edema of the legs and feet.
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Numbness of hands and feet.
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Itching.
How Is Azotemia Diagnosed?
The steps in diagnosis include,
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Medical History
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Asking for medical history is important to understand the symptoms as well as to gain knowledge about the usage of drugs, toxins, systemic diseases, etc.,
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Clinical Examination
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To check for elevation in temperature, blood sugar, and blood pressure levels and to check for the signs of dehydration such as dryness of the skin and mucous membranes, signs of edema in the hands and feet, etc.,
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24-hour Urine Output Monitoring
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This is done to monitor the kidney function as decreased urine output indicates diminished kidney function or any obstruction.
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Blood Examination
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Basic Metabolic Panel- This test is to evaluate blood urea nitrogen, creatinine, sodium, potassium, etc.,
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Blood Urea Nitrogen (BUN) Levels - Levels greater than 21 mg/dl indicate azotemia.
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Blood Urea Nitrogen: Creatinine Ratio - A ratio greater than 20:1 indicates prerenal azotemia; less than 20:1 is a sign of intrinsic and post-renal azotemia.
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How Is Azotemia Managed?
The treatment of azotemia depends on the etiology, type, and stage of progression of the disease.
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Intravenous Fluid Administration - It is indicated in cases with decreased blood flow to the kidneys or increased blood or fluid loss from the body. This helps in reestablishing the blood flow to the organs.
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Vasopressors - Are given to the patients to increase the blood flow, drugs such as Epinephrine act by constricting the blood vessels, thereby increasing the arterial pressure and helping in reestablishing the blood flow to the kidneys.
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Withdrawal of Toxins or Drugs - Immediate stoppage of any offending drugs or toxins is indicated to prevent further damage.
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Dialysis - Can be carried out to remove any offending toxins in the blood.
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Removal of Obstructions or Blockage - Post renal azotemia is treated by removing any obstruction or blockage in the ureter or bladder. Any type of benign or cancerous growth within or in the surrounding structures should be removed to provide relief.
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Proper Control of Systemic Diseases - Diseases such as diabetes, hypertension, and heart problems are risk factors that impair kidney function. Proper checks and control of blood sugar and pressure levels are necessary to decrease the risk.
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Antibiotics - Are given to treat any infections in the kidney.
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Permanent Hemodialysis or Renal Transplantation - In case of acute or chronic renal failure.
What Is the Prognosis of Azotemia?
The prognosis is reported to be good with early diagnosis and prior treatment. The cells of the kidney undergo repair with the restoration of normal physiological functions.
What Are the Differential Diagnoses of Azotemia?
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Prolonged Use of Corticosteroids - This can increase the blood urea nitrogen levels, which should be differentiated from azotemia.
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Gastrointestinal Bleeding- This can result in hypovolemia (decreased blood volume), thereby causing azotemia.
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Ketoacidosis - Mainly caused as a result of uncontrolled or poorly controlled diabetes would result in azotemia due to volume depletion and electrolyte imbalance.
Conclusion
Azotemia is not a disease but a condition that denotes the increased levels of blood urea nitrogen and creatinine levels in the blood. It is one of the classic signs of both acute and chronic kidney failure. Azotemia shows a good prognosis with prompt treatment; on the other end, untreated cases may progress to renal failure.
