Renal  calculi, commonly referred to as kidney stones affect about 5% of population. It is said that in more than 50% of patients, it is a recurrent problem. Men are more affected than women. This condition can develop at any age but average is around 30 years.

Stone formation begins when the urine becomes supersaturated with insoluble components, i.e. quantity of disposable salts becomes more than that which can be handled. It is said to be due to a genetic predisposition, modified by dietary habits.

Low volume, low acid content or excess excretions of the salts in urine are the underlying factors responsible for the stone formation. Majority of the stones are composed of calcium oxalate (70%).

A small number is of calcium phosphate, uric acid or struvite (formed by bacteria in people with recurrent urinary tract infections).Cystine stones develop very rarely due to a rare hereditary condition.

Drinking less water predisposes to low urine volume and can lead to stone formation. Acidic urine makes one more susceptible to urinary infection and also stone formation.

Consumption of excess meat particularly poultry and red meat also make one more prone to renal calculi. Metabolic conditions like Gout, insulin resistance, renal tubular acidosis, are also said to be risk factors implicated in formation of renal stones.

Inflammatory   Bowel diseases   lead to formation of stones in urinary system. 

Some hormonal diseases like hyperparathyroidism are also the cause for stone formation. Drugs like thiazide diuretic increase blood levels of uric acid and hence stone formation.

Bed ridden patients tend to suffer from renal stones because increased bone turn over increases passing of calcium in urine. Obesity is also a contributory factor to kidney stones. Added to all these factors is of course a genetic predisposition.

A person who has a family history of kidney stones is more susceptible to stones in kidney. 

Initially there is microscopic crystal deposition, in some part of the kidney. Further crystal deposition adds on the size, it may   enlarge, fragment and spread out to surrounding part. Stones may pass on to ureter (tube connecting kidney and urinary bladder) and bladder

In initial stages the stones are silent and produce no symptoms.

But as they multiply and grow in size, they tend to produce pain, which is intermittent and colicky, i.e. cramp like in character. This pain is typically present in the loin, may radiate to groin.

There may be associated nausea and vomiting. Intensity of the pain depends on size of stone and whether it is producing obstruction to passage of urine.

This renal colic may be acute, episodic or chronically present. With time the stones tend to get infected causing severe pain, fever   and other features of urinary tract infection like painful, frequent and urgent urination.

Pain can be associated with haematuria or passing blood in urine. If the stones persist, gradually kidney function gets deranged and kidney failure sets in which is a terminal event.

Renal calculi are diagnosed by means of plain and contrast  X-rays of abdomen and C.T. scans. Urine analysis gives a clue to the presence of stones and their type.

Drinking plenty of water ( 2.5 -3 L/day)  helps to augment urine volume. This   flushes out extra salts deposited, thus preventing stone formation.

It also removes   small stones less than 5 mm. in size. Low salt, low fat and moderate protein intake in diet is usually recommended for prevention of urinary stones.   A high calcium intake may help to reduce oxalate absorption and stone risk.

If stones are due to some medical cause, treatment of that cause is useful. But fluid intake and dietary measures should continue to prevent relapse.

Drugs are also used for associated conditions like, antibiotics for infection, analgesics for pain and fever, e.t.c. If kidney failure has started due to urinary calculi, dialysis is needed.

Larger stones or multiple stones causing severe pain or obstruction to urine passage need to be removed surgically.

Urinary stones are nowadays removed by lithotripsy a minor surgical procedure with minimal risk. Therefore one should not hesitate to undergo surgery if advised.

The author is a specialist in Internal Medicine

E-mail : rachna212002@yahoo.co.uk