Calcium Balance

Calcium Balance in a Healthy Body

Calcium is the most abundant mineral in the body. In a healthy person, each Kg of body weight includes about 22 gms of calcium. 99% of this calcium is in the bones.

Normal diet contains about 1000 mg of calcium in a day. About 400 mg is absorbed from the intestines. Intestines secrete about 150 mg and thus 750 mg is passed in stools.

About 9000 mg of calcium is filtered from the kidney. 8750 mg is reabsorbed and 250 mg is passed in the urine.

Approximately 800 mg of bone calcium moves into the extracellular space (intestinal secretions, blood, fluid in the space outside blood vessels, lymph etc) and similar amount moves back into bones.

Calcium Requirements

Requirements in health change with age.

Requirements in children are

  • Birth to 1 yr about 200- 250 mg,
  • 1 to 3 yrs about 700mg,
  • 4 to 8 yrs 1000 mg and
  • during puberty 1300mg.

In adults upto 50 yrs of age about 1000 mg is sufficient. Man older than 70 yrs and pregnant woman under 18 yrs may require 200 mg extra.

Functions of calcium in the body

Calcium is required for bone formation.

It is also required essentially

for nerve and muscle function

( this includes cardiac rhythm and muscle activity),

various enzymatic processes in the cells,

and blood clotting.

Calcium is maintained in a very narrow range in the blood. The level in the cells is very low. Movement of calcium from outside to inside is required for electric current generation and contraction of muscles.

Low calcium level in the blood is called hypocalcemia.

A low calcium level in the blood gives rise to twitching of muscles, fits, spasm of hand and feet muscles etc. Reduced minerals in the bones cause rickets in children and weak bones in adults (osteomalacia) which can be painful and get fractured easily. This can happen with Vitamin D deficiency or if calcium is deficient in diet.

High levels of calcium are designated as hypercalcemia. High levels reduce kidneys ability to concentrate urine and more urine is passed. This can cause renal failure, deposition of calcium in kidney tissue (nephrocalcinosis) and stone formation. Recurrent stones may be a result of this.

Sources of calcium in the diet are milk, yoghurt (dahi, lassi, chhachh), Cheese, Tofu, almonds, cabbage, broccoli, turnip, green leafy vegetables and some varieties of fish (salmon, sardines)

Calcium supplements are available as calcium carbonate and calcium citrate. Usually, not more than 500 mg is taken daily. It can cause constipation and hence plenty of fluids should be taken with it. Very high doses of calcium can cause confusion, irritability, fits, stones, renal failure etc. These can interfere with antibiotics like ceftriaxone and antihypertensive drugs (calcium channel blockers).

There are large no of genetic and acquired diseases which result in abnormal calcium metabolism. These may need a consultation with a doctor for diagnosis and treatment.

Water Balance

Water Balance

Life on earth began in water. Water is the largest molecular constituent of the body. It makes up for about 60% of the total body weight in males and 55% in females.

It provides a medium for metabolic functions in the body. Enzymatic reactions occur in aqueous media. It maintains the form of cells, tissues and organs, helps in digestion, evacuation of body wastes, maintenance of body temperature, lubrication in joints, prevention of infections and many more such functions.

Water Distribution in the body

Of the total body water, 2/3 is in the cells and 1/3 is extracellular. Of the extracellular water, 2/3 is outside the vascular system and 1/3 is in blood.

Regulation of water balance

The osmolality( a measure of solute concentration in water) is held in a very narrow limit in the human body. This typically is 280 to 295 mosm/kg. If the osmolality increases in the body fluids, a hormone called ADH is produced at the base of the brain. This hormone increases thirst and decreases water excretion in the urine thus restoring osmolality.

If excess water is taken, in healthy humans, it is promptly excreted in urine. Even an intake of 8-10 liters in healthy persons may be tolerated.

Water quantities for balance in the body

Body losses of  water

Water is required for cooling down of the body by formation and evaporation of sweat. About 1 ml of sweat is required for losing .58 ml kcal of body heat. Thus about 400-500 ml of water is used in this way depending on environmental temperature, wind velocity, dryness of air etc. 100 -200 ml may be lost in the formation of stools. Small amounts are also lost in vapour form during breathing.

Kidneys excrete about 800 mosm of daily solutes in salt and electrolytes, urea etc. Since maximum urine concentration in healthy adults is about 1200 mosm, 2/3 litre of water is lost in this way daily.

Gains of water from outside

Apart from water ingested directly in fluids and beverages, water is also contained in food. Some fruits may have almost 100% water while most will have 50 to 60% water content. Thus 500 ml to 600 ml of water is ingested in foods. Water in similar quantity is produced by metabolism of proteins and carbohydrates in the body.

Thus to maintain a balance a minimum of about 600-800 ml of water is required to be ingested in the liquid form. An intake of 1.5 to 3 l is sufficient for most cases for healthy living. In old people a litre more water results in better function of the kidney and bladder.

Kidney Biopsy

Kidney Biopsy

Kidney Biopsy is a procedure in which a very tiny piece of the kidney is removed for examination under a microscope for diagnosis of the kidney disease. It may also inform us about prognosis (future course ) of the disease, severity of disease and suggest ways of treatment. The information given below is relevant for cases of native kidney biopsy.

Indications for kidney biopsy:

When urine shows high levels of protein, RBCs or other abnormalities like casts.

Unexplained acute kidney injury

Some cases of chronic kidney disease

renal transplant dysfunction

The procedure of kidney biopsy:

Patients consent is taken.

Blood group is checked.

Tests are done to see that the bleeding and clotting is normal

Ultrasonography to confirm that both kidneys are

present ,

normal or large,

more or less symmetrical,

there is no stone disease, tumour or cyst etc.

The person is made to lie down on his abdomen with the back facing up. After cleaning the area with antiseptics, the site of biopsy is injected with local anesthetic drugs. After a few minutes, a biopsy needle is gradually inserted till it is lying very close to the cortex of the kidney and the site is confirmed by  USG. Then the trigger is pressed. This inserts the needle for a distance of 10-15 mm in the kidney and a piece of tissue (16 to 18 gauge in core diameter ) is trapped in the needle. The needle is then withdrawn and the site dressed in clean sterile gauze. It is pressed for a few minutes with compression of about 1to 2 kgs and patient then turned to lie on his back. His USG is checked for any bleeding after biopsy and shifted to the ward.

He is kept under observation for 24 hrs (sometimes only 6 hrs) for any complications. If none, he or she is discharged and called to attend the hospital with biopsy report.

Processing and transport of biopsy:

The tissue is sent in formalin/ glutaraldehyde or cold saline for different tests. It is usually seen by light microscope and immunofluorescent staining and if available, electron microscopy.

Risks of kidney biopsy:

The common risk is bleeding. It occurs in most cases but usually is insignificant. If a large amount of blood is lost, patient may require blood transfusion and rarely if bleeding is not controlled, the kidney may have to even be removed. Nowadays such occurrences are rare.

The biopsy site or kidney may get infected, lacerated and even deaths after biopsy have been reported. The risk of death is about 1in 1000 to 1 in 10000 at various centers.