Kidney Stones Symptoms, Diagnosis & Treatment

Kidney Stones

What are Kidney Stones?

Kidney stones, also known as renal calculi or nephrolithiasis, are hard mineral deposits that are formed within the kidneys. The stones can be found free in the renal calyces or attached to the renal papillae.

On the other hand, ureteral stones refer to stones that are stuck in the ureters, which are tubes that transport urine from the kidneys to the bladder. Conversely, bladder stones refer to stones located in the bladder, often due to incomplete emptying of the bladder, amongst other causes.

Kidney stones (Nephrolithiasis) are one of the most common diseases of the urinary tract and are dependent on geographical, climatic, ethnic, dietary, and genetic factors. It affects about 12% of the world’s population and up to 19% of Southeast Asia’s population. Kidney stones can affect all ages and are more common in men than women. It is estimated that the risk of kidney stones is about 1 in 10 for men and 1 in 35 for women. The lack of physical activity and dietary habits are believed to contribute to the increasing prevalence of kidney stones.

Kidney stones are mainly characterised by their composition. There are many possible compositions of kidney stones, but the five major types are – calcium oxalate, uric acid, calcium phosphate, struvite, and cystine stones.

Calcium oxalate (75-90%): The most common type of kidney stones is made up of calcium and oxalate. They are formed when there is too much oxalate in the urine. Oxalate is a substance naturally found in many foods, such as fruits, vegetables, and nuts.
Uric acid (5-20%): Uric acid stones are another common type of kidney stone that form when there are high levels of uric acid in the urine and when the urine is too acidic. Uric acid stones are usually caused by food that is high in purines, such as beef, poultry, pork, and eggs. Pure uric acid stones cannot be seen on normal X-ray films.
Calcium Phosphate (6-13%): Calcium phosphate stones are usually formed when urine is too alkaline. Calcium phosphate stones tend to grow faster and larger than calcium oxalate stones.
Struvite (2-15%): Struvite stones are stones made of magnesium ammonium phosphate and are associated with infections of the upper urinary tract.
Cystine (0.5-1%): Cystine stones are made of cystine and are often associated with cystinuria, an inherited condition that results in cystine build-up in the urine.

What causes Kidney Stones?

The formation of kidney stones is a complex biochemical process which is not completely understood. In general, the process of stone formation starts with supersaturation and chemical imbalance in the urine.

● Supersaturation

Supersaturation occurs when a solvent contains more of the dissolvable solutes that can be dissolved by the solvent under normal circumstances. A decrease in fluid intake can cause urine to be supersaturated. As a result, the solutes precipitated in the urine can lead to nucleation and crystallisation, which can lead to stone formation.

● Chemical imbalance

Urine contains minerals that are both urinary inhibitors and urinary promoters of crystallisation. In normal healthy individuals, urine crystallisation is prevented by inhibitory substances. High concentrations of certain chemicals such as uric acid, calcium, oxalate, and phosphate and low concentration of certain substances such as citrate and magnesium can lead to stone formation.

Why are Kidney Stones harmful? Do they increase your risk of kidney disease?

The kidneys are important life-sustaining organs with various vital functions such as eliminating waste products from the blood, maintaining pH, salt, and water balance, and secretion of various hormones.

Kidney stones can block the excretion of urine, causing pain, infection, kidney damage, or even kidney failure. It has been shown that kidney stones can eventually lead to serious health complications, such as an increased risk of chronic kidney diseases and end-stage renal failure.

What are the symptoms of Kidney Stones?

The initial stage of stone formation can be asymptomatic. In general, as the stones travel down from the kidney to the bladder, you may experience:

Cramps and intermittent abdominal and flank pain
Nausea and vomiting
Fever and chills
Blood in urine

Symptoms may also vary according to the stone location:

The distal section of the ureter: Flank pain (back) radiating to the groin area, anterior abdominal pain, dysuria (painful urination), increased urinary frequency or sensation of incomplete emptying of urine or hematuria (blood in the urine).
The middle and proximal section of the ureter: Flank pain radiating to the groin area, anterior abdominal pain or hematuria.
Kidney: Vague flank pain, hematuria or no symptoms (asymptomatic).
Bladder: Generally asymptomatic. If the bladder stones cause obstruction to urine flow, it can result in severe lower abdominal pain or pain around the penis. Bladder stones may also cause urinary symptoms like increased urinary frequency or sensation of incomplete emptying of urine, or haematuria.

When should you go to the doctor?

You should see a doctor if the pain is severe and is disrupting your daily routine. Symptoms such as vomiting, fever, chills, and blood in the urine should also prompt an immediate visit to the urologist for diagnosis and treatment.

How are Kidney Stones diagnosed?

The diagnosis of kidney stones begins with questions to understand your condition better. This includes the duration and evolution of your symptoms, family history of kidney stones, and any indication of complications such as infection or kidney function deterioration. Urinalysis and imaging tests are also essential in helping to determine the size and location of the kidney stones:

Urinalysis: A urine test which involves the examination of the physical and chemical composition of the urine. It gives useful information such as urine pH, the presence of microhematuria (blood in the urine that can only be seen under a microscope), and crystals.
Urine Culture: This lab test helps check for any bacteria in the urine and rules out any coexisting urinary tract infections.

Abdominal Ultrasonography: This imaging test uses targeted ultrasound waves to examine the abdominal area. It is readily available and may pick up larger kidney stones or any swelling of the kidneys or kidney masses. However, it may not be very useful in detecting ureteral stones.

Plain Radiography: This imaging test involves X-ray radiation. It is useful in documenting the location and size of radiopaque kidney stones. Stones that contain calcium are the easiest to detect by radiography, while pure uric acid stones are not detectable.

Intravenous Urogram: This is a series of X-rays images taken after injecting intravenous contrast to visualise the bladder, kidneys, and ureters. It is useful in determining the size and location of the kidney stones, as well as to delineate the urinary tract for other abnormalities such as ureteric strictures or cancers. Stones not normally seen on plain radiography (e.g., uric acid stones) may present as a dark shadow in certain images.

Non-contrast or Contrasted Helical Computerised Tomography (CT): This imaging test is fast and accurate. It is useful in detecting and identifying almost all stones (99.9%) in all locations. It can also identify the anatomy of the urinary tract and any other abnormalities, such as kidney cysts or cancers. Additionally, it helps to rule out or detect other non-urologic causes of abdominal pain.

How are Kidney Stones treated?

Treatment of kidney stones is dependent on the number, size and location of the stones.
The various treatment options include:

Expectant or Medical Expulsion Therapy (MET)
Oral Chemolysis
Ureteroscopy and Laser Lithotripsy
Retrograde Intrarenal Surgery and Laser Lithotripsy
Extracorporeal Shockwave Lithotripsy (ESWL)
Percutaneous Nephrolithotomy
Minimally invasive or open surgeries
Bladder stones

1. Expectant Management or Medical Expulsion Therapy (MET)

Spontaneous passage of stone may occur based on the stone’s size. It has been reported that up to 75% of stones < 5 mm and 50-60% of stones > 5 mm may pass spontaneously within two weeks. The chance of stone passage decreases with increased time intervals, but there may be a recurrence of pain or other symptoms during this period.

Certain drugs known as α-blockers may be useful in patients with distal ureteral stones between 5-10 mm in size who are suitable for expectant management. The chance of spontaneous stone passage may be increased by 10-15% in selected cases.

2. Oral Chemolysis

Oral chemolysis means taking certain medications to dissolve kidney stones. Most kidney stones cannot be dissolved by medications. The exceptions are pure uric acid stones that may be dissolved by oral chemolysis by alkalinisation of the urine to the optimal pH of 7.2 Patients will need to adjust the dosage of the medication by self-monitoring the pH of their urine as over-alkalinisation of urine may lead to the formation of calcium phosphate stones.

3. Ureteroscopy and Laser Lithotripsy

Ureteroscopy is a procedure that uses a small, thin endoscope called the ureteroscope to examine and treat urinary tract conditions. Laser lithotripsy refers to the fragmentation of the stones using lasers. This procedure is done under general anaesthesia to treat stones located in the ureters. Depending on the size and location of the ureteral stones, ureteroscopy and laser lithotripsy are associated with a high stone-free rate of >90% after treatment. Post-lasering, larger stone fragments can be removed using a cage-like basket or stone grasper. Smaller stone fragments will be passed out spontaneously through the urine.

A ureteral stent may be placed temporarily after the procedure. The stent is a soft, flexible tube with a J-shaped curvature at both ends. The purpose is to allow for adequate urine drainage and facilitate the clearance of stone fragments.

4. Retrograde Intrarenal Surgery and Laser Lithotripsy (RIRS)

This procedure is suitable for kidney stones located in the kidneys and is associated with a high stone-free rate for stones <15 mm. It involves the use of a thin and flexible ureteroscope inserted from the urethra into the bladder and all the way up the ureter into the kidney to visualise the stones. A thin laser fibre can then be inserted to break the stones into smaller pieces.

Stone fragments can then be removed with the help of a flexible stone basket. A larger plastic tube called a ureteral access sheath is often used to facilitate the passage of the ureteroscope and the removal of stone fragments. This procedure is done under general anaesthesia and may require the insertion of a ureteral stent one to two weeks prior to facilitating the insertion of the access sheath. With the use of high-powered lasers, larger stones up to 20-25 mm can be effectively fragmented.

5. Extracorporeal Shockwave Lithotripsy (ESWL)

Extracorporeal (“outside the body”) shockwave lithotripsy is a non-invasive procedure that uses high-energy waves to break stones into smaller pieces which may then be passed out naturally by urination. The shock waves are created by the machine outside the body and are focused on the stone using an acoustic lens. Some side effects, such as bruising and minor discomfort in the back or abdomen, may occur.

ESWL is generally very effective for ureteral stones <10 mm and kidney stones <10 mm located at the upper and mid poles. Stones located at the lower pole may be fragmented, but clearance may be poorer. More than one session may be required for harder and larger stones.

6. Percutaneous Nephrolithotomy

Percutaneous nephrolithotomy (PCNL) is often done for stones larger than 2 cm or in a location that makes shockwave lithotripsy ineffective. In this procedure, a small incision in the back is made, and a tract is created from the skin to the kidney with the help of ultrasound and X-ray imaging. An access sheath is subsequently inserted to allow direct passage of the endoscope into the kidney. A nephroscope is used to locate the stones, and an energy and suction device can be inserted through the nephroscope to fragment the stones and remove the fragments. A ureteral stent is inserted after the procedure for one to two weeks. Another urine tube may be inserted at the back after the procedure for one to two days.

7. Minimally Invasive or Open Surgery

Advances in ESWL and endoscopic procedures like URS/RIRS/PCNL have relegated minimally invasive or open stone surgeries to the last treatment resort after all other possibilities have been explored, attempted and failed. Very rarely are minimally invasive or Open stone surgeries performed for the largest and most complex stones or if there are anatomical abnormalities that require surgical correction or preclude endoscopic procedures, e.g., concomitant ureteral strictures.

Minimally invasive approaches, like conventional laparoscopic or robot-assisted procedures, have made the need for open surgeries exceedingly rare.

8. Treatment of Bladder Stones

Bladder stones are usually treated through cystoscopy, which involves the insertion of a cystoscope through the urethra into the bladder to visualise the stone and the use of an energy device (lasers/ultrasound device/stone crusher) to fragment the stones. The stone fragments can then be washed out from the bladder through the cystoscope.

Very large bladder stones > 4-5 cm can also be removed through open surgery or minimally invasive surgeries.

Generally, the formation of bladder stones is associated with urinary obstruction or stasis. As a result, the treatment of bladder stones may require concurrent treatment of the underlying causes, e.g., Transurethral Resection of the Prostate (TURP) in patients with obstruction and enlarged prostate.

What happens to Kidney Stones if they are left untreated?

In many cases, the kidney and ureteral stones are small enough to pass through the bladder and out of the body in the urine. They are unlikely to cause problems without treatment. However, the larger kidney and ureteral stones may get stuck while trying to get passed out from the body. When this happens, the stones can cause severe pain, and if left untreated, they can block the ureters. As a result, they can increase the risk of infection and other complications.

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Summary

Although kidney stones are a common urinary disease with considerable improvement in the development of management therapies, their incidence is increasing globally. If left untreated, these stones may block the ureters, increasing your risk of infection and adding strain to the kidney.

Thankfully, there are a variety of ways to treat kidney and ureteral stones. If you experience any of the aforementioned symptoms, please visit your urologist for a proper diagnosis and treatment plan tailored to your needs.