Renal calculi or kidney stones affect about 5 per cent of the population. It is said that in more than 50 per cent of patients it is a recurrent problem. Men are more affected than women . This condition can develop at any age but average age 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 of the urine, low acid content of the urine or excess excretion of the salts are the underlying factors responsible for 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 reduces 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 makes 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. Added to all these, 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 the crystal deposit increases in size, it may enlarge, fragment and spread out to surrounding part. Stones may pass on to the tube connecting kidney and bladder
Initially 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 they 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.
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 (< 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 helps 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.
Dr Rachna Pande, specialist – internal medicine