#renal system

Creatinine

• Creatinine is a waste product produced in muscles from the breakdown of a creatine. 
• Creatine is part of the cycle that produces energy needed to contract  muscles. 
• Both creatine and creatinine are produced at a relatively constant rate. 
• Almost all creatinine is excreted by the kidneys, so blood levels are a good measure of how well your kidneys are working.

If low: 

• Low levels are not common and are not usually a cause for concern. 
• As creatinine levels are related to the amount of muscle the person has, low levels may be a consequence of decreased muscle mass (such as in the elderly) but may also be occasionally found in advanced liver disease.

If high:  

• Kidneys break down creatinine - if levels are high, they’re not working properly –>
• Damage to or swelling of blood vessels in the kidneys (glomerulonephritis) caused by, eg, infection or autoimmune diseases bacterial infection of the kidneys (pyelonephritis)
• Death of cells in the kidneys’ small tubes (acute tubular necrosis) caused, for example, by drugs or toxins
• Prostate disease, kidney stone, or other causes of urinary tract obstruction.
• Reduced blood flow to the kidney due to shock, dehydration, congestive heart failure, atherosclerosis, or complications of diabetes

Creatinine blood levels can also increase temporarily as a result of muscle injury and are generally slightly lower during pregnancy.

Urea

Urea is the final breakdown product of the amino acids found in proteins. Nitrogen in the form of ammonia is produced in the liver when protein is broken down. The nitrogen combines with other chemicals in the liver to form the waste product urea.  Healthy kidneys remove more than 90% of the urea the body produces.

If Low: 

• Low urea levels are not common and are not usually a cause for concern. They can be seen in severe liver disease or malnutrition but are not used to diagnose or monitor these conditions. Low urea levels are also seen in normal pregnancy.

·   If high: 

• High urea levels suggest poor kidney function. 
• Acute or chronic kidney disease. 
• However, there are many things besides kidney disease that can affect urea levels such as decreased blood flow to the kidneys as in congestive heart failure, shock, stress, recent heart attack or severe burns; bleeding from the gastrointestinal tract; conditions that cause obstruction of urine flow; or dehydration.

Albumin

Albumin is the most abundant protein in the blood. It keeps fluid from leaking out of blood vessels; nourishes tissues; and transports hormones, vitamins, drugs, enzymes, and ions like calcium throughout the body. Albumin is made in the liver and is extremely sensitive to liver damage. 

If low:

• Low albumin concentrations in the blood can suggest liver disease. Liver enzyme tests are requested to help determine which type of liver disease.
• Diseases in which the kidneys cannot prevent albumin from leaking from the blood into the urine and being lost.
• Also seen in severe inflammation or shock.
• Conditions in which the body does not properly absorb and digest protein such as Crohn’s disease.

If high: 

• High albumin concentrations in the blood usually reflect dehydration.

This is a very long list so click keep reading to read the rest!

Phosphate

In the body, phosphorus is combined with oxygen to form a variety of phosphates (PO4). Phosphates are vital for energy production, muscle and nerve function, and bone growth. They also play an important role as a buffer, helping to maintain the body’s acid-base balance.

If low:  (hypophosphataemia)

• Hypercalcaemia (high levels of calcium), especially when due to high levels of parathyroid hormone (PTH)
• Overuse of diuretics (drugs that encourage urination)
• Severe burns
• Diabetic ketoacidosis after treatment
• Hypothyroidism
• Hypokalaemia (low levels of potassium)
• Chronic antacid use
• Rickets and osteomalacia (due to Vitamin D deficiencies)
• Increased production of insulin

If high:  (hyperphosphataemia) 

•  Kidney failure
•  Hypoparathyroidism (underactive parathyroid gland)
•  Hypocalcaemia (abnormally low levels of calcium)
•  Diabetic ketoacidosis when first seen
•  Phosphate supplementation

Alkaline phosphatase

Alkaline phosphatase is an enzyme found in high levels in bone and liver. Smaller amounts of ALP are found in the placenta and in the intestines. Each of these makes different forms of ALP (isoenzymes).

If low

• Zinc deficiency. Magnesium deficiency. Anaemia. Poor nutrition.
• Hypophosphatasia (Metabolism disorder, in born). Hypothyroidism.  Wilsons disease. 

If High: 

• Raised levels of ALP are usually due to a disorder of either the bone or liver. 
• If other liver function tests are also raised, this usually indicates that the ALP is coming from the liver. 
• However, if calcium and phosphate measurements are abnormal, this suggests that the ALP might be coming from bone.
• In some forms of liver disease, such as hepatitis, ALP is usually much less elevated than AST or ALT. 
• However, when the bile ducts are blocked (for example by gallstones, scars from previous gallstones or surgery, or by a tumour), ALP and bilirubin may be increased much more than either AST or ALT. 
• ALP can also be raised in bone diseases such as Paget’s disease (where bones become enlarged and deformed), in certain cancers that spread to bone or in vitamin D deficiency.

Calcium

 99% of calcium is found in the bones, and most of the rest circulates in the blood. Roughly half of calcium is referred to as ‘free’ (or 'ionized’) and is active within the body; the remaining half, referred to as 'bound’ calcium, is attached to protein and other compounds and is inactive.

If low: (hypocalcaemia)

The most common cause of low total calcium is low protein levels, especially low albumin. When low protein is the problem, the 'free’ calcium level remains normal. 

• Underactive parathyroid gland (hypoparathyroidism)
• Decreased dietary intake of calcium
• Decreased levels of vitamin D
• magnesium deficiency
• too much phosphate
• acute inflammation of the pancreas
• chronic kidney disease
• calcium ions becoming bound to protein (alkalosis)
• bone disease
• malnutrition, and alcoholism.

 If high:(hypercalcaemia)

• Hyperparathyroidism (increase in parathyroid gland function) usually caused by a benign tumour on the parathyroid gland. 
• Cancer when spread to the bones, which releases calcium into the blood, or when it causes a hormone similar to PTH to increase calcium levels.
• Hyperthyroidism, Sarcoidosis, Tuberculosis, Too much Vit D, Drugs that increase diuretics.

Potassium: 

Abnormal concentration can alter the function of the nerves and muscles.

If low: (hypokalaemia)

• vomiting,
• diarrhoea, and insufficient potassium intake (rare).

In diabetes, potassium concentration may fall after insulin injection.

If high:

(hyperkalaemia)

• kidney disease
• Addison’s disease
• tissue injury
• infection
• diabetes
• excessive intravenous potassium intake (in patients on a drip)

Glucose: 

If low: (hypoglycaemia)  

• Adrenal disease (Addison’s disease)
• Alcohol/ drugs, such as: paracetamol and anabolic steroids
• Extensive liver disease
• Hypopituitarism
• Hypothyroidism
• Insulin overdose
• Insulinomas (insulin-producing pancreatic tumours)

If high: 

High levels of glucose most frequently indicate diabetes, in fasting blood glucose test: <7mmol/L is indicative and in oral glucose test ites <11 mmol/L .

• Acromegaly
• Acute stress (response to trauma, heart attack, and stroke for instance)
• Long-term kidney disease
• Cushing’s syndrome
• Drugs, including: corticosteroids, tricyclic antidepressants, oestrogens (birth control pills and hormone replacement therapy [HRT]), lithium..
• Hyperthyroidism
• Pancreatic cancer. Pancreatitis

Triglyceride: 

Most triglycerides are found in fat (adipose) tissue, but some circulate in the blood to provide fuel for muscles to work. 

If low: 

• Hyperthyroidism. Malnutrition. Certain medications and drugs can deplete fat, leading to low triglycerides. 

If high: (e.g. at least 10-15 mmol/L) –> pancreatitis. 

Parathyroid hormone: 

Part of a ‘feedback loop’ that includes calcium, PTH, vitamin D, and to some extent phosphate and magnesium.  PTH is secreted into the bloodstream in response to low blood calcium concentration. 

• If both PTH and calcium results are normal, and appropriate relative to each other, then it is likely that the body’s calcium regulation system is functioning properly.
• Low –> conditions causing hypercalcaemia, or to an abnormality in PTH production causing hypoparathyroidism. 
• High –> hyperparathyroidism, which is most frequently caused by a benign parathyroid tumour.

Calcium - PTH Relationship

• Calcium  low and PTH high, then PTH working. Low calcium may be investigated.
• Calcium  low and PTH normal or low –> hypoparathyroidism.
• Calcium high and PTH  –> hyperparathyroidism.
• Calcium  normal and PTH high –> vitamin D deficiency or chronic kidney disease.

Amylase

Released from the pancreas into the digestive tract to help digest starch. It is usually present in the blood in small quantities. When cells in the pancreas are injured or if the pancreatic duct is blocked (by a gallstone or rarely by a tumour) increased amounts of amylase find their way into the bloodstream.

If high:

•  Pancreatitis which is a severe inflammation (often 5-10 times normal)
• Cancer of the pancreas, gallbladder disease, a perforated ulcer, obstruction of the intestinal tract, mumps or ectopic pregnancy. 
• Increased blood amylase with normal or low urine amylase may indicate decreased kidney function or the presence of macroamylase.