What are kidney and ureteral stones?
Kidney stones, also known as renal calculi, nephrolithiasis, or urolithiasis, 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. Ureteral stones refer to stones that are stuck in the ureter, which is a tube that transports the urine to the bladder. Kidney stones are the most common disease of the urinary tract and affect about 12% of the world population. Although it can affect anyone at any age, it is more prevalent in men than women.
Kidney stones can lead to serious health complications, such as the increased risk of chronic kidney diseases and end-stage renal failure. The lack of physical activity and dietary habits are believed to contribute to the increasing prevalence of kidney stones.
Affects 12% of the world’s population
Affects anyone at any age
More prevalent in men than women
What are the symptoms of kidney and ureteral stones?
The initial stage of stone formation can be asymptomatic. In general, as the stones travel down from the kidney through the ureter and then to the bladder, there may be cramps and intermittent abdominal and flank pain. Intense pain may be accompanied by nausea, vomiting, fever, and chills. Blood may also appear in the urine as the body tries to push the stones out. Sometimes, the symptoms are so mild that the patient is unaware of the condition and this can potentially lead to renal dysfunction.
The symptoms may also vary according to the stone’s location:
- Kidney: Vague flank pain, hematuria (blood in urine)
- The proximal section of the ureter: Flank pain, upper abdominal pain, renal colic
- Middle section of the ureter: Flank pain, anterior abdominal pain, renal colic
- The distal section of the ureter: Flank pain (pain at the back), anterior abdominal pain, dysuria (painful urination), change in urinary frequency, renal colic (intense cramping pain due to stones stuck in the urinary tract)
When should I visit a 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 a visit to the doctor for diagnosis and treatment.
What causes kidney and ureteral stones?
The formation of kidney stones is a complex biochemical process. In general, the process of stone formation starts with supersaturation and chemical imbalance in the urine.
Low intake of water
Supersaturation
It occurs when a solvent contains more of the dissolved 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 are the steps involved in stone formation.
High concentration of chemicals in urine
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 concentration of certain chemicals such as uric acid, calcium, oxalate, and phosphate and low concentration of certain chemicals such as citrate and magnesium can lead to stone formation.
What are the risk factors for kidney and ureteral stones?
The risk factors for kidney and ureteral stones have been studied extensively due to their increasing prevalence around the world. Risk factors for kidney stones include intrinsic factors such as age, sex, and heredity, and extrinsic factors such as climate, dietary habit and water intake.
1. Age and sex
Generally, the prevalence of kidney stones increases as age increases and men are more likely to develop stones compared to women.
2. Genetic predisposition
There is an increased risk of stone formation in those who have a family history of kidney stones. Positive family history also increases the risk for early and multiple recurrences of kidney stones.
3. Geographical factors
Places with high humidity and temperature appear to be associated with an increased risk of kidney stones. Individuals living in hotter climates are more prone to dehydration and, consequently, increasing the risk of developing kidney stones.
4. Dietary habits
Excessive intake of animal proteins and sodium-rich food and a diet low in fibre and vegetables can increase the risk of kidney stones. Inadequate water intake also increases the risk of stone formation.
5. Metabolic disorders
Individuals with metabolic disorders such as hypercalciuria (high calcium), hypocitraturia (low citrate), and gout may contribute to the increased risk of kidney stones.
6. Comorbidities
Other comorbidities such as hypertension and obesity are associated with an increased risk of kidney stones.
How are kidney and ureteral stones diagnosed?
Diagnosis of kidney stones begins with a thorough understanding of your symptoms – its duration and evolution, as well as your personal and family medical history. Urinalysis and imaging tests are also essential in helping to determine the size and location of the kidney stones.
1. Urinalysis
This urine test involves the examination of the physical and chemical composition of the urine. It gives useful information such as the urine pH, the presence of microhematuria, and the presence of crystals.
2. Urine culture
This is a lab test to check for any bacteria in the urine. It can help to rule out any coexisting urinary tract infections.
3. Abdominal/Kidney/Bladder ultrasonography
It is an imaging test that uses ultrasound to look at the abdominal area and its organs. It is readily available and sensitive to pick up any kidney stones or obstructed kidneys. However, it may not be very useful in detecting ureteral stones.
1. Plain radiography
(X-ray)
This imaging test is useful for 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 the most difficult to detect.
5. Intravenous pyelography
This x-ray exam uses an injection of contrast material into the veins to look at the kidneys, ureters and bladder as the contrast travels down. It provides useful information on stones with regards to their size, location, radiodensity and degree of obstruction. It has greater sensitivity and specificity for kidney stones compared to ultrasonography and radiography.
6. Non-contrast helical computerised tomography (CT)
This imaging test is fast and accurate. It is useful in detecting and identifying all stones in all locations. It also helps to rule out or detect non-urologic causes of abdominal pain.
What can I expect during my first consultation?
During the first consultation, a detailed medical history will be taken and questions such as the location of the pain and dietary habits will be asked in order to get a better understanding of your condition.
This may be followed by physical examinations to rule out other underlying diseases. If a kidney stone or ureteral stone is suspected, urinalysis, urine culture, and other diagnostic imaging tests will be ordered for further evaluation.
How are kidney and ureteral stones treated?
Treatment after a confirmed diagnosis of kidney or ureteral stones are largely dependent on the stone size and location.
Conservative management with a focus on pain relief is usually indicated when an emergency such as sepsis is ruled out and adequate analgesia is obtained. About 86% of kidney stones pass spontaneously and this proportion is lower for stones larger than 6mm. Generally, less conservative modes of treatment, such as active stone removal, are recommended when the kidney stones have not passed within 2-4 weeks.
Active stone removal includes procedures such as medical expulsive therapy, oral dissolution therapy, shockwave lithotripsy, ureteroscopy, and percutaneous nephrolithotomy.
Medical management
- Medical expulsive therapy
Non-steroidal anti-inflammatory drugs (NSAIDS) are used for pain relief in the absence of other contraindications. Certain medications such as alpha-adrenergic receptor antagonists and calcium channel blockers may help stones to pass spontaneously by dilating/relaxing the distal ureter.
- Oral dissolution therapy
Oral dissolution works mainly on uric acid stones by dissolving them through the use of oral agents. Uric acid stones are susceptible to oral chemolysis by modulating the pH of urine to 7, increasing urinary volume, and decreasing uricosuria.
Lithotripsy
- Shockwave lithotripsy
This is a non-invasive procedure done under sedation that involves the use of high energy waves to break stones into smaller pieces which can be passed out naturally by urination. The shock waves are created 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.
- Ureteroscopy
This procedure involves the use of an endoscope to access the stone from the urethra up to the ureter and kidney. It also allows the delivery of other devices such as guidewires and laser fibres. Ureteroscopy may be necessary for ureteral and renal stones. The stone is fragmented by laser energy and removed using a cage-like basket or simply passed out as sand.
- Percutaneous nephrolithotomy
This procedure is often done with stones larger than 2cm or in a location that makes shockwave lithotripsy ineffective or difficult. In this procedure, a small 1cm incision at the back is made which allows direct passage of the endoscope into the kidney. A nephroscope is used to locate and remove the stone using lithotriptors/lithotripsy or lasers. Percutaneous nephrolithotomy allows the stones to be removed surgically rather than relying on their natural passage from the kidney.
Prevention
Due to the increasing prevalence of kidney stones and recurrence rates, preventive strategy is a low-cost public health initiative with huge societal impacts. Lifestyle modifications remain the most important preventive measure for kidney stones. Some are:
- Increase fluid intake to about 2.5L to 3L a day
- Diet high in fibre, fruits, and vegetables
- Diet low in animal protein, sodium, and oxalate (such as nuts, tea, and chocolate)
- Citrate supplementation
Summary
Although kidney stones are a common urinary disease with considerable improvement in the development of management therapies, its incidence is increasing globally. The formation of kidney stones is a complex process generally believed to involve supersaturation of urine due to a decrease in fluid intake and chemical imbalance, possibly due to dietary habits. Several risk factors for kidney stones include genetic disposition, geographical factors, dietary habits, and certain metabolic disorders.
Kidney stones can be treated through a variety of procedures and proper nutritional management. If you suspect you have kidney stones or any other urological conditions, please do not hesitate to visit us for proper diagnosis and treatment.
