Urinary tract calculi or stones, also termed as urolithiasis refers to stones in the kidney, ureters or bladder.

How are urinary tract stones formed?
Normally, waste products and other toxins formed in our body (that can dissolve in water) are eliminated outside the body via the urine. Obviously, if there is less of solvent (urine) or an excess of solute (the waste product eg. calcium, uric acid, etc), then a supersaturated solution results. The solute thus crystallises within the kidney and forms a solid mass (stone). Urine normally contains chemicals that inhibit stones formation. In some people with kidney stones, these inhibitors do not function properly.

Urinary tract calculi begin to form in a kidney and may pass into and enlarge in the ureter or the bladder. Depending on where a stone is located, it can be a kidney stone, ureteral stone, or bladder stone.

Types of Urinary Tract Stones
Stones are made of minerals that have crystallised. Nearly 85% of the stones are composed of calcium and oxalate or phosphate and uric acid stones. Struvite stones—a mixture of magnesium, ammonium, and phosphate, also called infection stones, form only in infected urine.

Causes of Urinary Calculi
• Lack of inhibitors in urine such as citrate
• Metabolic disorders – hyperparathyroidism, hyperuricosuria
• Inherited conditions – renal tubular acidosis, cystinosis, hyperoxalosis
• Excessive intake of vitamin D, calcium
• Diet rich in animal protein
• Drug induced – diuretics, corticosteroids (prednisolone), indinavir

Risk factors of Urinary stones
• Men are more likely to develop urinary stones
• Family history
• Tropical climate with excess sweating and inadequate fluid intake
• Following bariatric or weight loss surgery

Signs and Symptoms of Urinary Calculi
• Small stones may not cause any symptoms and may be detected incidentally
• Renal colic – movement of stone from the kidney causes irritation and may block the flow of urine resulting in pain. The pain of renal colic is felt at the back and side of the abdomen, and may travel down to the groin (“loin to groin” pain). The pain typically increases in intensity to a peak and then decreases, each cycle lasting 20-60 minutes
• Blood in urine due to injury to lining of the urinary tract from the stone
• Difficulty and discomfort while passing urine
• Nausea, vomiting
• Fever may be present if there is associated urinary tract infection

Diagnosis of Urinary Stones
History and physical examination
History of renal colic, tenderness over the loin radiating to the genital area, passing blood in the urine. Presence of urinary calculi may be suspected based on history and further tests may be
required to confirm the diagnosis and rule out other causes of acute abdominal pain

Urinalysis:
Analysis of urine may be done to look for presence of red cells, pus cells and urine microscopy may reveal the presence of crystals

X-ray abdomen (KUB film)
If calcium stone s suspected, x-rays can confirm the presence of a stone or to see how far a stone has travelled down the ureter.

Ultrasound abdomen
Abdominal ultrasound is an alternative to CT and does not expose people to radiation. However, ultrasonography often misses small stones (especially when located in the ureter), misses pinpointing exact site of blockage within the urinary tract, and other, serious disorders that could be causing the symptoms.

CT scan
Helical (or spiral CT that is done without the use of radiopaque contrast material is usually the best diagnostic procedure. CT scans precisely locate a stone and also indicate the degree to which the stone is blocking the urinary tract. CT can also diagnose other conditions that can cause pain similar to the pain caused by stones. The main disadvantage of CT is that it exposes people to radiation. Newer CT devices and methods that limit exposure to radiation are now available.

Treatment of Urinary tract Calculi
Pain relief
Measures to relieve colic pain are very effective. These are given either by mouth or injection into the muscle or vein. This is achieved with anti-inflammatories (eg. diclofenac). Pethidine is also frequently used for severe pain.

? NON-SURGICAL TREATMENT
Fortunately most stones do not require treatment and can be managed conservatively as follows

Stone Passing Measures
Drinking plenty of fluids or administration of large amounts of fluids intravenously has been recommended to help stones pass, but the efficacy of such measures is uncertain. Alpha-adrenergic blockers (such as tamsulosin) may aid in the passage of stone. If the stone passes with these measures, no other immediate treatment is needed.

Dissolving Stones
Certain types of stones (eg. uric acid stones) can be dissolved by either taking oral medications (potassium citrate); or a tube being placed through the skin into the kidney and a solution being injected.

Stone Bypass Procedures
Sometimes when a blockage is severe, a temporary tube (stent) may be inserted in the ureter to bypass the obstructing stone. The stent is inserted via a telescopic viewing instrument (cystoscope, a kind of endoscope) introduced into the bladder and passed through the cystoscope into the opening of the ureter. The stent is then pushed up past the obstructing stone. The stent is left in place until the stone can be removed at a later date(for example, by surgery).
Alternatively, the blockage may be overcome by inserting a drainage tube through the back into the kidney (nephrostomy tube) to drain the urine.

Stone Removal in Renal Pelvis/Upper Ureter – Extracorporeal Shortwave Lithotripsy (EWSL)
Extracorporeal Shockwave Lithotripsy (ESWL) uses sound waves transmitted through the skin to break up the stones in the renal pelvis or upper ureter into pieces that can be passed out in the urine. The procedure can be painful and pain relief is usually given before the procedure. Occasionally, a laser can be used to break up the stone, and the procedure is called holmium laser lithotripsy.

Removal of Lower Ureteric Stones
An ureteroscope can be inserted into the urethra and through the bladder to remove small stones in the lower part of the ureter that require removal. In some instances, the ureteroscope can also be used with a device to break up stones into smaller pieces that can be removed with the ureteroscope or passed in the urine (a procedure called intracorporeal lithotripsy). Most commonly, holmium laser lithotripsy is used. In this procedure, a laser is used to break up the stone.

? SURGERY
Sometimes when the stone is too large to break up with ESWL, and causing obstruction, open surgery may be required. Several weeks are usually required to fully recover from major stone surgery. Usually struvite stones are removed by endoscopic surgery

Prevention of Urinary Tract Stones
• Increasing fluid intake particularly water to maintain an urinary output of 2 litres per day
• Reduce salt intake
• Reduce intake of oxalate containing foods (for oxalate stones) eg tea, spinach
• Reduce acid producing foods eg meat, fish and poultry (for uric acid stones)
• Change in drug or dosage for drug induced stones
• Drugs to reduce stone formation eg allopurinol (uric acid stones), bendroflumethiazide (calcium stones), potassium citrate (to alkalinise urine) or penicillamine (cystine stones)