The incidence rate of kidney stones is making a big scene in the medical stage right now. There are more and more people who visit the hospital complaining of flank pain thinking that it is just another type of urinary tract infection. However, kidney stones is something that can be considered more life threatening. The formation of renal stones is primarily brought about by the human diet. So, what are the foods to avoid for kidney stones?
Kidney stones or renal calculi are solid crystals that are formed in the kidneys. These stones are from the minerals found in the urine. Kidney stones are classified according to their locations and chemical composition. If it is found in the kidneys, it is called nephrolothiasis. If it is found in the ureter, it is called ureterolithiasis and cystolithiasis if it is found in the bladder. Kidney stones can be classified in accordance to their composition such as calcum, struvite, uric acid or other compounds.
In the United States, kidney stone has an incidence rate of 1-2 per 1000 Americans with a lifetime prevalence of 3-5%. Majority of those affected with kidney stones are male which is about 80% of all cases. Kidney stones in women are commonly caused by either infection or metabolic defects. Men usually have their first episode of renal stones at the age of 30-40 years old while women have it later in life. Recurrence rate of renal stone is high with about 50% over a 10 year period and 70% over 20 years.
Classification of kidney stones in accordance to their chemical composition:
1. Calcium containing stones. This is the most common type of kidney stones. In the United States, it represents 80% o all kidney stones cases. This type of stones contains calcium oxalate alone or in combination with calcium phosphate in the form of brushite or apatite. The formation of calcium stone is associated with conditions such as renal tubular acidosis and hyperparathyroidism.
2. Struvite stones. This type of renal stone comes after calcium stones in terms of its incidence rate which represents 10-15% of all urinary calculi cases. This is often referred to as “infection stones” because it forms in the presence of urea splitting bacteria. This type of bacteria metabolizes urea into ammonia and carbon dioxide. This results to urine alkalinization which provides a favorable environment for struvite stone formation. The most common type of organisms that contribute to the formation of struvite stones are Proteus mirabilis, Morganella morganii and Proteus vulgaris. This type of renal stone is often seen in people with metabolic disorders such as gout.
3. Uric acid stones. This type of stone accounts for 5-10% of all renal stone cases. This is common for those who are obese and with metabolic abnormalities. High level of uric acid in the blood and urine can predispose one to this type of renal stone. Also, low urine pH can result in the precipitation of uric acid crystals.
4. Other types. Other types of renal stones are seen in people with inborn errors of metabolism. For example, those with cystinosis or cystinuria are high risk of acquiring cystine stones while those with xanthinuria are high risk of acquiring xanthine renal stones.
Signs and Symptoms of Renal Stones:
• Oliguria or reduced urine volume. This is caused by obstruction of the ureter or bladder by stone.
• Hematuria or blood in the urine. This is caused by abrasions in the urinary tract during formation or passage of renal stones.
• Renal colic or pain. This type of pain can sometimes be referred to as the strongest pain humans can feel. The pain comes in waves that last to about 20 to 60 seconds. This is due to the contractions made by the ureter in an attempt to expel the renal stone. The pain usually starts at the lower back and often radiates to the groin and testis. Nausea, vomiting, fever, and pain in urination are often associated with renal colic.
Before diagnosing renal stones, physical assessment, laboratory works and imaging studies are done. The best way to diagnose renal stones is through imaging studies. Ultrasound of the kidneys, Ureters and bladder or KUB, Intravenous pyelogram (IVP) and non contrast helical CT scan are some of the imaging studies that can best detect renal stones.
Ultrasound is useful in detecting hydronephrosis or the distention and dilatation of the renal pelvis and calyces which suggests a stone blocking he outflow of urine. Radiolucent stones are best seen in ultrasound than in CT scan.
In IVP, a contrast is injected on the vein followed by a KUB film. This is best to detect uroliths in the KUB. The modality of choice in diagnosing kidney stones is the non contrast helical CT scan. If positive for renal stones, Xray of the KUB is advised in order to determine the exact size and shape of the urolith.
Management for renal stones includes pain control with opiods and non steroidal anti inflammatory drugs, medical intervention and surgical intervention. Medical intervention includes the intake of medicines that can reduce the size of the stone and allow it to be passed on the urinary tract. If medical intervention is found ineffective, surgical intervention is the last choice. However, huge stones that could not be dealt with medical intervention are automatically managed by surgical interventions. Some of the surgical options are as follows: extracorporeal shock wave lithotripsy, laser lithotripsy, percutaneous nephrolithotomy, and stent placement to allow the passage of the renal stone.
Prevention of renal stones is always better than treating it. One way to prevent acquiring renal stones is through proper diet. Foods that should be avoided are those that are high in salt and oxalate content which are Blackberries, beans,chocolate, Celery, Dark leafy greens, legumes, leeks, fruit cake, nuts, parsley, red currants, okra, strawberries, Swiss chard, spinach, tea and wheat germ. Milk, poultry and meat can also predispose one to renal stones. One technique when eating foods such as stated above is to have them in moderation and to load the body with lots of fluid everyday in order to prevent the urine from become concentrated and to allow urine minerals to be flushed out of the body.