Difference between Uraemia and Azotemia

Uremic frost present on the forehead and scalp

Kidneys are very important organs of the human body as they carry out many vital functions. They produce important hormones, absorb electrolytes, maintain fluid balance, regulate blood pressure, filter out waste and form urine. All these functions are important for the smooth running of the human body.

Presence of Uraemia or Azotemia in a person indicates that his or her kidneys are not functioning well. Since the kidneys perform myriad functions they are vulnerable to diseases especially in the current times due to unhealthy eating habits and lack of exercise. Sometimes kidneys can be defective since childhood. Levels of urea and creatinine in the blood are prominent markers of deteriorating kidney function. Let us understand the difference between Uraemia and Azotemia.

Structural formula of urea

Uraemia

Uraemia literally means urine in blood. One of the main roles of kidney is to excrete nitrogenous waste formed as a result of protein and amino acid metabolism. Normally the urea and uric acid formed as a result of protein breakdown is filtered through the kidney and excreted in the urine. But when kidney function is affected due to some systemic or local infection in the body, there is presence of urea in blood. This is usually seen in end stage kidney failure or very acute kidney failure. There is total shut down of kidney function. Glomerular filtration rate falls below 60ml/min which causes very high plasma concentration of urea.

The patient presents with repeated shallow respiration, progressive energy loss, decreased exercise tolerance, decreased interest in daily activities, loss of weight, loss of appetite, whole body swelling due to fluid retention, nausea, vomiting, skin frost (as urea is secreted in sweat),  urine output falls drastically etc. If the patient is not hospitalised immediately for dialysis, he can develop metabolic acidosis, pericarditis (fluid in the outer covering of the heart), lethargy, confusion, organ failure, coma and eventually death.

Azotemia

Azotemia is defined as nitrogen in blood. It can be considered as the chemical stage of kidney failure, in the sense that patient does not present with any overt symptoms of kidney disease but his serum creatinine and blood urea nitrogen levels are elevated. It is a warning sign and should be considered as a precursor of uraemia. Protein and amino acid break down results in formation of nitrogenous by products that must be eliminated in the urine. When kidney function is compromised, these by products are not filtered out and hence find their way into the blood. Normal range of blood urea nitrogen (BUN) is between 8-20 mg/dl and serum creatinine is 0.7-1.4 mg/dl. The normal glomerular filtration rate is 125ml/min. When BUN and serum creatinine levels increase by around 20-30 % and glomerular filtration rate falls below 70ml/min, it indicates Azotemia.

There are three types of Azotemia. Pre-renal Azotemia occurs when the blood flow to kidneys are compromised due to some disease in the body. This causes an increase in the BUN and creatinine values. Intra-renal Azotemia occurs due to a primary kidney disease like glomerulonephritis, acute kidney failure etc. Post renal Azotemia occurs due to an obstruction in the ureters. This causes back flow of urine and overflow of urinary contents into the blood.   Azotemia must be identified at the earliest and fluid administration, electrolyte balance and medical intervention must be begun in time.

Azotemia and uraemia occur due to failing kidney function. Azotemia can be considered as a milder manifestation of Uraemia.

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