Kidney plays an important role in excretion of many metabolic breakdown products, including ammonia, urea and creatinine from protein and uric acid from nucleic acids, drugs and toxins. Kidney also plays an important role in regulation of fluid and electrolyte balance. Kidney regulates acid base homeostasis, calcium and phosphate homeostasis, Vitamin D metabolism and production of red blood cells. It has very important role in regulation of blood pressure also.
Renal stone or kidney stone disease is common which can affect all age group and in individuals living anywhere in the world.
Kidney stone consists of aggregates of crystals, which may be either calcium or phosphate or proteins. Kidney stones form in urine and can travel from kidney to bladder through the urinary tract, so It may be anywhere from the kidney to the ureter. Size of calculi or stone may vary greatly from a minute sand particle to large round stone usually in the bladder. Usually crystal deposition occurs in concentrated urine therefore dehydration is a major risk factor for stone formation. Very small stones usually pass through urine without any problem but larger stone causes obstruction and causes pain, infection and bleeding.
The common sites of obstruction from a stone in the upper urinary tract are located at the:
• Junction where the kidney meets the upper ureter,
• Mid portion of the ureter, or
• Lower ureter at its entry into the bladder
Based on the location of stone term used, for example; stone in the kidney called as nephrolithiasis, stone in the urinary tract termed as urolithiasis, stone in the ureter termed as ureterolithiasis.
Types of stones
Most common type of kidney stone is calcium oxalate around 60% and least common type of kidney stone is cysteine which is around 1%.
|Magnesium ammonium phosphate (struvite)||15%|
|Cysteine and others||1%|
Calcium stones- when calcium combines with another mineral like oxalate or phosphate then Ca-oxalate, or Ca-phosphate insoluble crystals form. These can be easily seen on plain X –ray. Usually, no specific cause is found on why these stones develop, however they can occur in certain medical conditions such as hyperparathyroidism, certain types of weight reduction surgery, and in several types of kidney disorders.
Magnesium ammonium phosphate (struvite) – Most important cause is infection of urinary tract (by urease producing organisms), which causes rapid stone growth.
Uric acid stones– Uric acid is a product of purine metabolism. Uric acid is 100 times more soluble at a pH > 6 compared to a pH <5.5. Other than dehydration, the most common risk factor for uric acid stone is persistently acidic urine, more commonly due to excessive high protein diet, obesity or gout. These stones cannot be seen on plain X- ray.
Cysteine stones– these are rare and due to an inherited defect in amino acid transport within the kidney. An excess of cysteine crystals are found in the urine of affected patients which clump together to form stones. Patients who are affected tend to be young and develop recurrent kidney stones throughout life. Long term treatment involves close surveillance, education, dietary changes, fluids, and sometimes medications to prevent the stones from recurring.
Predisposing Factors for the Kidney Stones
1. Environmental causes– high ambient temperature and decrease fluid intake leads to dehydration which is a very important risk factor for the kidney stones.
2. Dietary causes – Diet high in protein, high in sodium and low calcium promotes the renal stone.
3. Medical causes – Hypercalcemia due to any cause, hyperparathyroidism, gout, renal tubular acidosis and urinary tract infection are major risk factors for the kidney stones.
4. Surgical causes– surgeries like ileal resection or gastrointestinal tract surgery, weight loss surgery can also promote the kidney stones.
5. Hereditary cause– If someone in the family has history of renal stone then there are more chances to develop renal stone in the individual. Some diseases like familial hypercalciuria, cysteinuria, medullary sponge kidney, primary hyperoxaluria are other conditions which can cause the kidney stones.
6. Medicines- People taking certain medications like diuretics, calcium based antacids, Indinavir (protease inhibitor used for treatment of HIV), topiramate (antiseizure) are also at increased risk of developing the kidney stones.
Symptoms are greatly vary. Sometimes patient is asymptomatic but most commonly it presents with acute severe pain at the flank (loin) which radiates to anterior abdominal wall or to the groin, it may radiate to testes or labium and anterior/lateral region of thigh. Pain intensity increases in few minutes, patient becomes restless and tries to change position, pain may be associated with vomiting, pallor and sweating. Sometimes hematuria (blood in urine), dysuria (difficulty in passing the urine), or fever with chills (if there is infection in urinary tract or in kidney) may occur due to the kidney stones. The intense pain usually subsides within 2-3 hours but constant or intermittent dull pain in the loin or back may persist for hours to days.
How to Diagnose?
1. Symptoms- Typical excruciating pain on the site of stone or loin and radiates to anterior abdominal wall or groin region, and other symptoms described above.
2. Physical exam, medical history, surgical history, family history and diet.
3. Urine analysis to know any infection, blood in urine, protein, glucose, amino acids, urea, creatinine, sodium, calcium, oxalate and uric acid.
4. Blood test will show any biochemical problem which can cause the kidney stone.
5. Imaging technique –about 90% stones contain calcium can be seen on abdominal X ray but CT scan of Abdomen(KUB-kidney ureter bladder) is the best way to diagnose the kidney stone.
6. Sometimes your doctor can ask for IVP to know the proper flow and excretion from the kidney or USG to know the stones within the kidney and if there is any obstruction in urine flow.
What is the treatment?
Treatment of the kidney stones depends on the size and location of stone, But immediate treatment is analgesic with antiemetic because renal colic is unbearably painful and demands strong analgesic.
If stone is less than 4mm diameter it may pass spontaneously through the urinary tract with increase intake of fluids. In certain situations, a tablet called tamsulosin may be beneficial in helping pass a kidney stone which is obstructing the ureter.
If an underlying infection is suspected (fever or chills), urgent medical treatment should be sought immediately with antibiotic coverage. Patients with kidney stones are at high risk for developing infection so antibiotic coverage is also important.
Stones bigger than 6 mm in diameter require endoscopic surgical intervention. Depending upon clinical presentation and site of obstruction your doctor may choose any of the following surgical procedure.
ESWL(Extracorporeal shock wave lithotripsy)– This procedure is performed by the urologist, in which shock waves generated outside the body are focused on the stone, breaking it into small pieces that can pass easily down the ureter.
PCNL (percutaneous nephrolithotomy) – This procedure is performed by urologist, by using nephroscope through small incision in the patient’s back to locate and remove the stone.
Occasionally, a temporary hollow tube called a stent will be required to assist in keeping the urinary tract unobstructed either before or after definitive stone surgery has been carried out.
Prevention is always better than cure.
1. Fluid intake- At least 3 liters of fluid intake is very important to prevent kidney stones formation. Even more oral fluids need to be consumed on hotter days due to insensible losses from perspiration (sweating). A good measure of success is the color of the urine should be clear or a very pale yellow.
2. Low salt intake- decrease sodium intake in the diet or salt restriction. The more sodium you take in and excrete, the more calcium you waste in the urine. Excess calcium in the urine can lead to new stone formation. Try to reduce dietary sources of sodium, including fast foods, packaged or canned foods, and salty snacks. Daily sodium intake should be less than 2000mg per day (around one tea-spoon of salt per day).
3. Low animal protein intake- Protein intake should be in moderate amount not very high.
4. Calcium intake- Maintain good calcium intake (calcium forms an insoluble salt with dietary oxalate, lowering oxalate absorption and excretion). The recommended daily requirement of calcium is 1000 mg, and two-thirds is consumed in dairy containing products. You are encouraged to consume two servings of dairy (but no more than two) or other calcium-rich food per day to maintain normal bone stores of calcium.
5. Oxalate- Avoid foods that are rich in oxalate (spinach, rhubarb)
6. Medicines to prevent stone formation- Diuretics, Allopurinol, Potassium citrate, Penicillamine. Avoid Vitamin D and Vitamin C supplementation.
7. Weight loss- Obesity is a risk factor for kidney stone, so maintain healthy lifestyle and weight loss can prevent kidney stone formation.
Few natural Tips to prevent kidney stones-
Drink plenty of fluids.
Apple- an apple a day keeps the doctor away. Apple has a diuretic property, which helps to prevent kidney stone.
Pomegranate –Freshly squeezed pomegranate juice helps to prevent stone formation, it has astringent property too.
Celery- celery has high fiber content and natural diuretic so it prevents kidney stone formation.
Basil- Basil is a natural kidney toner, drinking basil tea every day or basil juice with honey is very good remedy for kidney stones.
Kidney beans- Kidney beans are not only very high in fiber, they’re also a great source of non-animal protein, B vitamins, and minerals that improve urinary tracts and kidney health.
Please note: Any medical information published on this website is not intended as a substitute for informed medical advice and you should not take any action before consulting with a health care professional.
Content Source- Davidson’s Principles and Practice of Medicine (22ndedition) , stoneclinic.com.au