Kidney stones are solid masses formed in the kidney due to crystallization and aggregation of stone forming products within the urine. It is a common condition which is estimated to affect one in 10 adults worldwide. Chronic kidney disease (CKD) is a long-term condition where the kidneys are not functioning as well as they should. It is a progressive condition that can lead to end-stage kidney disease, which is a lethal condition without dialysis treatment or kidney transplant. While the main causes of CKD such as diabetes, hypertension and glomerulonephritis (inflammation of the kidney tissue) are well known, kidney stones are a significant but often overlooked contributor.
As a urologist with a subspecialty focus on kidney stones, I often treat patients with not only large or complex stones, but also preexisting CKD from chronic illnesses, and with anatomical or structural abnormalities. This article aims to increase awareness about complications arising from kidney stones that can adversely affect kidney function. It highlights the importance of early detection and management in order to preserve long-term kidney function.
TYPES OF KIDNEY STONES
In Singapore, the most common type of kidney stone is calcium oxalate stone, which is estimated to comprise about 70% of all cases. Other types of stones include calcium phosphate, uric acid, struvite (infection) and cysteine stones. Roughly 50% of patients will suffer from kidney stones again within the next 10 years of their life.
CAUSES
The causes of kidney stones are multifactorial. For some individuals, certain factors are more important than others. One of the main causes is having low volume of (concentrated) urine due to inadequate intake of fluids or excessive loss of fluids (e.g. through sweating or diarrhoea). Hence, those who do not drink enough (less than 2L of fluids a day) or those who work in a hot environment are at higher risk of forming kidney stones.
Another important reason why individuals develop kidney stones lies in what they eat. Individuals with a high intake of salt (sodium), and/or consume large amounts of food rich in oxalate content (such as chocolate, nuts and spinach) and animal protein like organ meats and seafood (which contains high amount of purine which is converted to uric acid) are at risk. Eating these foods leads to a high content of stone-forming products in the urine, which can precipitate into crystals when the concentration is high enough.
Other risk factors include having certain medical conditions such as obesity, hypercalcemia, hyperuricaemia (high amounts of calcium and uric acid in the blood) and recurrent urinary tract infection (UTI) or having structural abnormalities of the kidneys, such as pelviureteric junction obstruction, horseshoe kidney and medullary sponge kidney also predispose an individual to form kidney stones.
SYMPTOMS
When a stone is first formed within the kidney, it does not cause any symptoms. However, when the stone increases in size, migrates and drops to the ureter, it can cause intense pain. Many patients who have experienced this say that it is the worst kind of pain they have ever experienced. Typically, the pain starts in the flank (side of the upper abdomen) and can radiate down to the groin. Other times, kidney stones can cause blood in the urine (haematuria) or cause UTI to occur.
LONG-TERM KIDNEY DAMAGE AND CHRONIC KIDNEY DISEASE
Kidney stones cause long-term damage to the kidneys in several ways. Firstly, kidney stones can obstruct the flow of urine from the kidney to the ureter and bladder. This most commonly happens in the ureter, especially when the stone is more than 5mm in diameter. Larger stones may even cause blockage within the kidney. This leads to a condition known as hydroureter and hydronephrosis. This results in increased pressure and swelling within the kidney, which can damage the kidney tissue and may be permanent if not relieved in an expedient manner. Although rare, I have seen cases where patients with bilateral stone disease present with bilateral ureteric obstruction, leading to complete cessation of urine production (a condition known as anuria) and acute renal failure.
Secondly, kidney stones are a source of bacteria, which can predispose an individual to have UTI. Recurrent infections can lead to scarring of the kidney, which can cause lasting damage to kidney function.
Thirdly, direct injury to the kidney (mechanical damage due to direct contact with the inner lining of the kidney) may lead to inflammation, fibrosis and scarring of the kidney tissue, leading to functional loss over time. This typically occurs with large stones called staghorn stones that can fill up almost the entire kidney. Furthermore, conditions which predispose individuals to kidney stones, such as hypercalciuria and hyperuricaemia, may also damage the tubules of the kidney, further affecting kidney function.
Lastly, individuals with kidney stones may have concurrent conditions such as obesity, diabetes and hypertension, all of which also contribute to the development of CKD.
TREATMENT
In the acute stage where the stone has migrated to the ureter and causes intense pain, pain relieving medications (oral or injection) are prescribed. The patient is also advised to drink lots of water to expel the stone. In addition, where suitable, I will prescribe medications to help in expelling the stone. This medication works by relaxing the ureter, thereby enlarging the ureter so that the stone may pass out through the urine.
If the stone fails to pass or is deemed highly unlikely to pass at the outset, or if complications occur such as obstruction (hydronephrosis or hydroureter) and infection, the urologist may offer the following minimally invasive treatments to remove the stone.
• Extra Corporeal Shockwave Lithotripsy (ESWL)
This is the least invasive procedure to remove kidney stones. Shockwaves are generated by a machine from outside the patient’s body and targeted towards the stone. The shockwaves break the stone into smaller pieces, thereby allowing the stones to pass out through the urine more easily.
• Ureteroscopy (URS)
This is an endoscopic procedure where a thin tube with a camera is inserted into the patient’s urine passage through the bladder and up the ureter to reach the stone. The stone is typically broken into smaller pieces with the use of a laser and can then be easily removed.
• Renoscopy or Retrograde Intra-Renal Surgery (RIRS)
Similar to URS, but this time, a longer, flexible endoscope is inserted into the patient’s urine passage, up the bladder and ureter to reach the stone within the kidney.
• Percutaneous Nephrolithotomy (PCNL)
This is a surgical procedure for larger stones, usually 2cm or more in size. It involves getting direct access to the kidney through a small incision (1cm or less) in the flank or lower back. An endoscope is used to locate the stone within the kidney, which can then be fragmented into smaller pieces and removed.
Recent advancements in laser technology and endoscopic equipment have led to the development of minimally invasive PCNL (mini PCNL) and tubeless PCNL which allows even smaller incisions (6mm or less) into the kidney. I offer these new techniques for suitable patients with large stones who are keen for a less invasive approach with faster recovery.
• Laparoscopic Surgery Or Open Surgery
When the stone disease is associated with a structural abnormality or as part of treatment for another condition, laparoscopic surgery or even open surgery may be employed. However, such instances are not common.
CONSIDERATIONS FOR TREATMENT
There are two main considerations when deciding on the most appropriate treatment: the stone factor as well as the patient factor. The stone size, location, type (and therefore hardness) and presence of other stones are key considerations. With regards to the patient factor, preexisting medical conditions as well as the current kidney function, medications such as blood thinners, or existence of structural abnormalities are also taken into account.
A customised or tailored treatment plan with a urologist who is able to offer all treatment options will ensure the best outcome in terms of removing the stone completely with the minimum number of procedures and complications.
PREVENTING RECURRENCE
As part of a holistic approach to kidney stone treatment, I also recommend strategies to prevent further stone formation in the future. It is estimated that up to half of patients with kidney stones will have recurrent stones within the next 10 years of their life. A full metabolic evaluation, as well as dietary and lifestyle assessment, are part of a comprehensive treatment plan for my patients with kidney stones.
Asian Healthcare Specialist Clinic @ Novena
Asian Healthcare Specialist Clinic @ Alvernia
CONCLUSION
Kidney stones are a common condition that can sometimes affect the normal functioning of the kidneys and thereby lead to CKD. Having an awareness of this relationship ensures that individuals suffering from kidney stones are able to recognise signs of complications and seek treatment early, which will go a long way towards protecting their long-term kidney function.
