Kidney stones, also called renal calculi, are one of the most common disorders of the urinary tract. They are hard rock-like crystals (of varying sizes and shapes) which form when certain chemicals in the urine aggregate and then gradually increase in size. Normal urine contains chemicals called stone inhibitors which reduce this crystal formation.
Four major types of stones:
- Stones formed from calcium combined with oxalate or phosphate – the most common types
- Uric acid stones
- Stones caused by urine infection – (struvite stones)
- Cystine stones which are rare and hereditary.
Causes of kidney stones
- A number of different factors can contribute to stone formation:
- Excess calcium, phosphate, oxalate and uric acid in the urine
- Insufficient amounts of stone inhibitors in the urine
- Low fluid intake resulting in concentrated urine and a higher probability of crystal formation
- Recurrent urine infections.
- Rare inherited conditions.
The symptoms of kidney stones
- Persistent ache in the lower back, which is sometimes also felt in the groin – men may have pain in the testicles and scrotum
- Periods of intense pain in the back or side of your abdomen or occasionally in your groin, which may last for minutes or hours
- Feeling restless and unable to lie still
- Nausea (feeling sick)
- Needing to urinate more often than normal
- Pain when you urinate
- Blood in your urine, which may be caused by the stone scratching the kidney or ureter.
Investigations are required to confirm the presence of a stone and to identify the site of the stone and degree of obstruction.
- RADIOGRAPHY – plain x-ray (KUB) helps to diagnose 90% of renal stones. It can be visualized as an opacity which overlies the urinary tract and keeps a relatively constant position during respiration. Enlarged renal shadow can also be made out.
- INTRAVENOUS PYELOGRAPHY OR EXCRETORY UROGRAPHY – This helps to locate the stone exactly in relation to kidney & ureter & to assess renal function. A radiolucent stone can be seen as a filling defect. Hydronephrosis can also be made out.
- ULTRASONOGRAPHY – is the most valuable to diagnose the stone, its size & exact location. It also confirms the enlarged kidney.
- URINE CULTURE & SENSITIVITY – Examination of urine for protein, R.B.C, W.B.C, micro organisms reveals abnormalities of urinary tract, infection etc.
- INVESTIGATION OF RENAL FUNCTION – Blood examination for urea, creatinine, creatinine clearance etc to rule out renal failure.
- INVESTIGATION TO DETERMINE UNDERLYING CAUSES – plasma calcium, phosphate, parathormone, plasma urate, 24 hour urine urate, cystine & oxalate & calcium.
- STONE ANALYSIS – analysis of any stone that has been passed.
- Drink at least 3 litres of water every day and even more in hot weather.
- Avoid or eat sparingly, food containing calcium oxalate (spinach, strawberries, tomatoes, grapefruit juice, apple juice, chocolate, celery, bell peppers, beans, asparagus, beets, soda, and all types of teas and berries).
- Reduce uric acid by eating a low-protein diet.
- Reduce salt; higher amounts may raise the level of calcium oxalate in your urine.
- Avoid vitamin D supplements which can increase calcium oxalate levels.
- Davidson’s Principles & Practice of Medicine.