Urinary stones form when minerals in the urine reach a concentration beyond which nucleation and crystallization occurs. They can be called kidney (or renal) stones, ureteric stones, or bladder stones, depending on where they are located within the system.
Surprisingly, some patients do not have symptoms (asymptomatic), while others may experience severe pain (flank pain, known as renal colic), or blood in the urine (haematuria). If left untreated, it may lead to infection and cause fever. It may also result in worsening of kidney function. While some cases of asymptomatic stones are detected incidentally during health screening, most cases present with pain and/or bleeding. If one has reason to suspect he or she has urinary stones, it is recommended that one should seek early consultation with a GP/family physician, or at the emergency department.
Presence of blood in the urine, if its not visible, can be confirmed by urine microscopy or on urine dipstick. Confirmation of the diagnosis of urinary stones is best achieved by CT scan, though ultrasound scan or X-rays may be sufficient in some cases.
Small asymptomatic stones in the kidney may be left alone, and observed. But when they are large, or when there are symptoms or complications such as bleeding or obstruction, treatment becomes necessary.
It is interesting to note that small stones in the ureter may pass out spontaneously, with or without the aid of medication (referred to as medical expulsion therapy (MET)). When too big for this to work, intervention is needed. Common treatment options include shockwave lithoptripsy and ureteroscopic laser lithotripsy. For stones larger than 2cm, percutaneous nephrolithotomy is the most effective for removal.
There are multiple causes and risk factors known for urinary stones. For some people, it may be multifactorial, contributed by diet, hydration, climate and sun exposure, as well as lifestyle and activity levels. Genetic factors have also been identified.
Geographically, there are regions in the world where the prevalence and incidence of stones are higher. For example, there is the Afro-Asian stone-forming belt, as illustrated below, which stretches across large parts of Asia and North Africa.
Flank pain as a symptom:
This may be caused by musculoskeletal (eg back muscle strain) problem or urinary (stone, kidney cancer) problem, or nerve (radicular pain). Clinical examination, urine tests and imaging studies (X-ray and/or scans) may be needed to assess the cause. If the pain is severe or persistent, one should seek consultation with a GP/family physician or at the emergency department.
Extracorporeal shockwave lithotripsy (ESWL):
High energy focussed mechanical shock waves from a machine passes through the skin and soft tissues to reach and break up small stones in the ureter and kidney. If successful, these small fragments pass out of the body, avoiding the need for more invasive procedures or surgery. The procedure does not require any incisions to be made and may be performed under general anesthesia or sedation. ESWL should not be offered in pregnancy and in patients taking blood thinning medications, or when there is infection complicating the stone.
Percutaneous nephrolithotripsy (PCNL):
For complex or large stones, PCNL is the most effective method of removal. This is performed under general anesthesia. A small (between 5mm and 10mm) cut is made on the skin overlying the kidney, instruments are passed sequentially to gain access to the kidney. The stone is fragmented to small pieces and evacuated.
Ureteroscopic Laser Lithotripsy:
One of the most effective ways to treat urinary stones is laser lithotripsy. Access to the stone is achieved with an endoscope – eg semi-rigid ureteroscope for stones in the lower ureter, and flexible ureteroscope for stones in the upper ureter and kidney.
The stones are fragmented and dusted with high energy laser pulses to the extent they can pass out easily in the urine. Though this procedure is invasive, and requires anaesthesia, it achieves the higher stone-free rates
Dr Lee Yee Mun
Senior Consultant Urologist
Kidney Stone Removal FAQs
Not all kidney stones need treatment or removal, eg, small stones without symptoms, especially in an older person.
When kidney stones are large or cause symptoms or obstruction, we recommend removal.
There are 3 methods (in order of increasing invasiveness) :
1) Extracorporeal shockwave lithotripsy (ESWL): High energy focussed mechanical shock waves from a machine passes through the skin and soft tissues to reach and break up small stones in the ureter and kidney. If successful, these small fragments pass out of the body, avoiding the need for more invasive procedures or surgery. The procedure does not require any incisions to be made and may be performed under sedation.
2) Flexible ureterorenoscopy (also referred to as Retrograde Intrarenal Surgery): Access to the stone is achieved by inserting a long flexible endoscope from the urethra, all the way up into the kidney. The stones are fragmented and dusted with high energy laser pulses to the extent that they can pass out easily in the urine. Though this procedure is invasive and requires general anaesthesia, it achieves better stone clearance than ESWL.
3) Percutaneous Nephrolithotomy (PCNL) :
For complex or larger stones, PCNL is the most effective method of removal. This is performed under general anaesthesia. A small (between 5mm and 10mm) cut is made on the skin overlying the kidney, and under X-ray and/or ultrasound guidance, instruments are passed sequentially to gain access to the kidney. The stone is fragmented into small pieces and evacuated.
In special situations, e.g. pure uric acid stones, chemical dissolution may be effective in clearing the stone.
This is uncommon, as the majority of stones are calcium-containing, and chemical dissolution does not work.
Though not without pain, the above treatment methods are minimally invasive techniques, and patients usually are able to go home on the same day after treatment. For PCNL, patients usually stay for 1-2 days, but in selected cases, it may also be suitable to be discharged on the same day.
Most patients are able to move about and perform normal activities the next day. There would usually be slight pain/discomfort when passing urine, and this can be relieved with medications. Depending on the nature of the patient’s occupational and invasiveness of surgery, the time off work can be as short as 2-3 days, to as long as 2 weeks
Stones that are 2cm or larger would generally require PCNL, while smaller stones may be treated with ESWL or RIRS.
The hardness of the stone also influences the treatment method. Assessment by a urologist is advised, for a customised treatment plan that best suits the patient
After RIRS, most cases would require a stent, which then has to be removed through a minor procedure after an interval of 1-2 weeks.
After PCNL, some cases would require a stent. ESWL patients do not require a stent.
Most times, it is non-urgent. Pain and infection can be treated with medications. However, if there is severe obstruction affecting kidney function ( and can cause kidney failure), then early surgery is advisable.
Depending on the complexity, surgery costs may range from $4500 to $8000, or more.
Some cases require staged procedures and inevitably would cost more.
Yes, small asymptomatic stones may be left alone and observed.