7 Common Questions On Kidney Stones Answered by a Urologist

Our body has two kidneys, which are bean-shaped organs located near the upper back of our body below the chest, with one on each side of the spine. The kidneys are joined to our bladder via the ureter, which is a long, narrow tube that helps to carry urine from the kidney to the bladder.

Our kidneys are important for our survival, and their functions include producing urine, removing waste and extra water from our body, and the production of hormones.

A kidney stone refers to hard crystals formed from minerals found in the urine. There are many types of kidney stones, the 4 most common ones are: uric acid, struvite (staghorn calculi), cystine, and calcium oxalate stones.

Kidney stones typically form when there is a high concentration of certain minerals in the urine. This can happen when there is too much minerals in the urine, and too little fluid. Small crystals form as a result, and the crystals typically combine with other substances to form a larger solid crystal that eventually becomes a kidney stone.

Causes of kidney stones include drinking too little water, dehydration, a diet high in salt/sugar, obesity, and medical conditions such as gout and polycystic kidney disease.

1. How common are kidney stones?

Each year, more than half a million people around the world go to the emergency room for kidney stones. In Singapore, up to 10% of Singaporeans will develop kidney stones at some point in their lives.

2. What are the warning signs of kidney stones?

Some kidney stones can be as small as a grain of sand and as large as a golf ball. Typically, smaller kidney stones do not cause any symptoms and can be passed out of the urine with no issues.

However, larger stones that get stuck as they travel down from the kidney to the bladder may cause symptoms such as:

Severe pain on either side of the lower back
Vague abdominal pain
Blood in the urine
Nausea and vomiting
Fever
Difficulty urinating or other urinary symptoms

The best way to manage this would be to seek medical attention as soon as you can to eradicate the blockage.

3. What are the effects of kidney stones?

Aside from obstructing the flow of urine, kidney stones may also cause damage by scratching and irritating the urinary tract as they pass through, which can lead to bleeding and irreversible scarring. Kidney stones may also cause the tubes within the urinary tract to perforate and burst due to pressure built up from obstruction.

In addition, blocking the urinary tract may cause bacteria to build up which can lead to severe urinary tract infections (UTI) and sepsis, which can be potentially life-threatening.

4. Do all kidney stones need surgical removal?

Not all kidney stones need surgical removal, especially the smaller and non-obstructing ones. In fact, some may pass on their own without treatment.

However, stones that cause pain and get stuck in the urinary tract may need to be removed via surgery or other treatment modalities.

5. What foods cause kidney stones?

Food associated with kidney stones includes high-oxalate foods such as:

Chocolate
Soybean
Most nuts
Black tea
Grapes
Liver
Marmalade

A good rule of thumb would be to stay adequately hydrated and also to avoid eating food with too much salt or sugar, and consume more vegetables and fruits, whole grains and low-fat dairy products.

6. Can stress cause kidney stones?

Stress is not known to directly cause kidney stones. However, stress could indirectly lead to poor diet choices, which, in turn, cause chronic dehydration, which are risk factors for kidney formation.

7. How are kidney stones treated?

Depends on the stones’ location, composition and size, among other factors, like the patient’s pre-existing conditions.

Medical Expulsion Therapy (MET)

For small stones, conservative management may suffice — that is to say, you may be advised to drink plenty of water to help move the stone along the urinary tract, and the stone may pass out in the urine within 2 weeks. Medications known as alpha blockers can also be prescribed to help with stone passage.

Up to 75% of stones < 5mm and 50% of stones > 5mm may pass out in the urine spontaneously within two weeks. However, the chance of spontaneous stone passage decreases if the stone does not pass within 2 weeks and may warrant further management.

Oral chemolysis

Oral chemolysis refers to taking certain medications to dissolve urinary stones. However, this only applies to uric acid stones. Oral chemolysis involves taking medications that will raise the pH of the urine, creating an alkaline environment that will, in turn, dissolve the uric acid stones.

For larger stones, other treatment modalities may be required, often involving procedures that break these stones into smaller particles:

Extracorporeal Shockwave Lithotripsy (ESWL)

ESWL is a non-invasive procedure that involves using shock waves to fragment kidney stones into smaller pieces that can be passed through urine. The shock waves are generated by a machine called a lithotripter, and are targeted onto the stones using an x-ray or ultrasound guidance.

Ureteroscopic laser lithotripsy (ULL)

Ureteroscopy is used to remove stones located in the ureter. A small scope known as a ureteroscope with a video camera attached to its end will be passed through the urethra, into the bladder, and up the ureter. The stone will be located and a laser fibre will be passed through the scope to help break the stone into smaller fragments.

Retrograde intrarenal surgery and laser lithotripsy (RIRS)

RIRS involves the use of a flexible ureteroscope. This procedure is suitable for stones located in the kidney and works very well for stones <10mm. The use of high powered lasers in this process enables the removal of larger stones up to 20-25mm as well.

A thin laser fibre is inserted through the ureteroscope to break stones into smaller pieces, and the fragments will then be removed with a flexible stone basket. A larger plastic tube (a ureteral access sheath) is often used to facilitate this removal of stones.

RIRS is done under general anaesthesia and may require the insertion of a stent for 1-2 weeks before the procedure to facilitate the insertion of the access sheath.

Percutaneous nephrolithotomy (PCNL)

PCNL is used for larger stones that cannot be broken down by ESWL or by laser with ureteroscopy. In this procedure, a tiny incision is made through the skin in the back and a small passageway is punctured to gain access to the kidney. The urologist will then pass a small scope, known as a nephroscope, through the incision to locate and fragment the stones, usually with ultrasonic energy. The fragments are usually removed via a suction device.

Surgical removal of urinary stones

Surgical removal of urinary stones is typically the last resort for the removal of stones these days, due to advances in ESWL and endoscopic procedures that have enabled the successful removal of most urinary stones. Very rarely, stones may need to be removed surgically especially if they are very large and complex, or if there are anatomical abnormalities in the patient that may not allow for the removal via ESWL/ endoscopy.

Minimally invasive surgery (MIS) such as laparoscopic surgery and robotic surgery are generally preferred over the traditional open surgery method in such complex cases whenever feasible.

Summary

Kidney stones are fairly common urological issues seen in the general population. Prompt recognition of symptoms and seeking medical attention will be the best way to help manage kidney stones and prevent complications.

The best way to prevent kidney stones will be to drink enough water, eat more fruits and vegetables, reduce salt intake, and lose weight to maintain a healthy BMI.