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 Kidney

September 2011
Stones in the kidney
Dr Mohammed A Rafey
 
In a majority of patients, kidney stones are small and do not cause any symptoms. Such stones are often found incidentally when the person has an X-ray or ultrasound of abdomen done for some other ailment. In some patients, these small stones pass into the urine without causing any symptoms.

Kidney stones are formed when an imbalance occurs in various chemicals that are present in the urine. The most commonly involved chemicals are calcium, oxalate, citric acid, uric acid and cysteine. When there is an abnormal composition of urine, some of these chemicals can precipitate and form crystals that later result in the formation of stones. In addition, certain medications can also cause formation of kidney stones.

At other times, these stones can get bigger and press on adjoining tissues and structures causing severe pain. Sometimes the stones cause an obstruction to urinary flow and if left untreated can damage the kidney permanently.

Pain due to kidney stones can vary in intensity and is usually present in the flank or lower abdomen area. The pain may be associated with nausea and vomiting and may be more prominent when passing urine. Another common presentation of kidney stones is the appearance of blood in the urine.

Types of kidney stones
Calcium stones are the most common stones and occur in about 80% of patients with kidney stone disease. Among calcium stones, the most common form of stones found are calcium oxalate stones followed by calcium phosphate stones. Other important stones are those composed of other chemicals like uric acid, struvite (magnesium ammonium phosphate) and cysteine stones.

Calcium stones
High calcium levels in urine and high oxalate levels in the urine can cause formation of calcium stones. A chemical called citric acid generally helps in inhibiting kidney stone formation. In some patients who have a lower citric acid level in the urine, calcium crystals precipitate leading to formation of calcium stones. Patients who do not drink enough water are also at risk to develop calcium stones.

Some medical conditions like hypothyroidism, renal tubular acidosis and inflammatory conditions of bowel are at increased risk for formation of calcium kidney stones.

Struvite stones
Recurrent urinary tract infections with certain bacteria, e.g. Proteus or Klebsiella, create an environment in the upper urinary tract that is favourable for formation of a fast growing stone composed of magnesium ammonium phosphate.

Cysteine stones
Some patients have a genetic abnormality that causes them to excrete excessive cysteine in urine leading to the formation of cysteine stones.

Precautions to prevent kidney stone formation
Biochemical analysis of the stone that is passed in the urine, and the 24 hour biochemical profile of a patient’s urine helps the physician to tailor therapy for each individual. Some general precautions for a patient diagnosed with kidney stone disease are mentioned below:
  • Increase your daily fluid intake (water intake should exceed 2 litres per day)
  • Lower the content of animal protein in your diet (reduce meat intake)
  • Lower your daily salt intake (2000 mg sodium restriction per day)
  • Lower intake of high oxalate content foods (eg., spinach, beets and chocolate)
  • Limit your coffee, tea and cola intake
  • Do not take excess of Vitamin D supplements
  • Reduce your daily sugar intake
  • Lemon and cranberry juice are considered safe
Dr Mohammed A. Rafey Consultant Nephrologist at Apollo Hospitals Hyderguda, Hyderabad.  


    
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