What are urinary stones?
Urinary stones are one of man’s oldest known diseases – the ancient Egyptians recorded them in their writings. They usually form in the kidney or bladder, but it is usually when they pass from the kidney into the ureter that they cause the main problems – severe pain (renal colic) and renal obstruction (the kidney is blocked). The medical terminology for urinary stones is calculi (calculus is the singular)
How common are they?
The lifetime risk of developing stones is about 1 in 10 for Australian men and 1 in 35 for women. Kidney stones account for about 1 of every 100 hospital admissions. 10% of all first time stone formers will get another episode within 1 year and 50% within 10 years.
What kind of stones are there?
There are different types of kidney stones, but an individual tends to form the same type when they recur. Types of stones include:
Calcium oxalate – the most common.
Calcium phosphate and magnesium phosphate.
Struvite stones – usually large stones that take the shape of the inner kidney (Staghorn Calculus).
What causes kidney stones?
In the vast majority of cases there is no specific reason why a urinary stone forms. Individuals seem to have a propensity to form stones without a specific single causative factor being identified. There are a few specific conditions that are precursors for stone formation and a few theories.
High protein intake is associated with stone formation. Thus, it is quite prevalent in first world, industrialised countries but also in third world countries where sufficient water may not be available or there is excessive fluid loss and dehydration.
Certain foods, especially in higher volumes pre-dispose to stone formation e.g. meat (purines); salt; calcium and oxalate are groups of food that promote stone formation.
Inadequate consumption of fluid on a daily basis also predisposed to stone formation, as does inadequate intake of fruits – especially citrus varieties.
Cystine stones tend to be familial. They are very hard stones, tend to be recurrent and difficult to treat. They form in acidic urine and can be influenced by active alkalinisation of the urine.
High urinary levels of the following pre-dispose to stone formation:
Calcium – high parathyroid levels, sarcoidosis, lack of physical activities (e.g. post-trauma, spinal injury etc.) that can lead to bone “resorption”, that is calcium leaks from the bones.
Oxalate – some bowel conditions change absorption.
Cystine – see above.
Uric Acid – more common in people who suffer from gout, though can also result from certain chemotherapy regimes.
Low urinary levels of the following pre-dispose to stone formation:
Citrate – can be dietary, but can also occur with inflammatory bowel disease, chronic diarrhea and malabsorption.
Urinary Tract Infections
Recurrent UTIs can trigger stone formation, which in turn often makes the infections difficult to treat as bacteria become imbedded within the stones. Obstruction or poor throughput of urine pre-dispose to these types of stones.
What are the symptoms?
Pain is the classic symptom of urinary stones. It tends to be very severe, in fact, most women who experience stone pain usually comment they would rather go through childbirth again rather than have another stone! The pain presents as:
Renal colic – a severe cramping pain felt in the loin (high back area). It comes in unrelenting waves.
Radiation – that is where the pain is often also felt in the groin and genitalia (labia, penis, testes).
Nausea – many people experience nausea, especially if the stone is on the right.
Frequency and urgency to pass urine – this usually occurs as the stone passes into the bladder – the pain stops then.
Some stones cause no pain, especially if in the kidney. Occasionally such a stone will damage the kidney despite causing no symptoms.
What tests might I need?
The CT scan has become the standard test in the investigation of urinary stones. It can identify all types of stones (some can’t be seen on standard X-ray), as well as determining the position of the stone and whether it is causing obstruction to the kidney. There is also the advantage of viewing all the other abdominal organs to ensure there are no other problems.
An ultrasound is useful for demonstrating obstruction to the kidney and some stones in the kidney. It cannot identify stones in the ureter and often misses stones within the kidney itself.
Blood and other tests
The following tests are usually performed at some time during the investigation of urinary stones:
Full blood count.
Renal function tests.
Serum Uric Acid.
24-hour urinary tests – usually performed if the stones are recurrent or there is an abnormality in the previous tests.
Nuclear scan – occasionally required to determine the presence of obstruction and the degree of renal damage.
How are stones treated?
The majority of stones will actually pass without the need for any surgical intervention. Approximately 85% of stone ≤ 5mm will pass. The CT scan usually allows the doctor to estimate the likelihood of spontaneous stone passage, after which an appropriate management plan is instituted.
The first priority is usually analgesia (relieving the pain). Many patients attend the Emergency Department – as the pain is strong enough to require narcotic analgesia. Once the initial pain is controlled, often it can be kept in abeyance with non-steroidal suppositories (e.g. Indocid suppositories) inserted once or twice a day. If necessary they can be supplemented with other medication.
These are only necessary if an infection is suspected in addition to the stone.
There is some evidence that alpha-blockers can aid the passage of ureteric stones. Many patients will be placed on a drug such as Tamsulosin to aid the passing of the stone.
In some instances, when a stone has been identified and neither severe pain or kidney obstruction is present then a patient may be placed on alkalinisation therapy in an attempt to dissolve the stone – this is only a possibility for Uric Acid & Cystine stones.
Surgery may be required in the following circumstances:
Persistent pain and the stone is not passing.
An obstructed kidney.
Evidence of infection or sepsis.
The stone is doing damage to the urinary tract.
There are quite a number of different surgical options for the treatment of urinary tract stones. The significant change that has occurred over time is that they are nearly all minimally invasive and it is extremely rare that major open surgery is required to treat stones.
If a stone is causing significant obstruction to a kidney or there is associated sepsis then the affected kidney may need to have the obstruction caused by the stone relieved. There are two options commonly used:
This is a technique in which a small tube is passed directly into the kidney through the back. It is usually performed in the Radiology Department under X-ray guidance.
A JJ stent is a small “plastic” tube inserted into the kidney, beside the stone, from the bladder. This bypasses the obstruction and drains the kidney. It is usually performed under a light anaesthetic in the operating theatre.
Standard Surgical Procedures
The procedures listed below are the standard operations performed for the treatment of urinary tract stones. Your doctor will discuss what options suit your particular stone. It is important to remember that not all techniques suit all stones.
Extracorporeal Shock Wave Lithotripsy is the most minimally invasive surgical option. It utilises special technology that focuses a “shock wave” on the stone that causes it to fragment into small pieces that are passed in the urine.
This technology revolutionised the treatment of urinary tract stones, as no incision or invasive equipment was necessary. The main disadvantage is that the small stone fragments need to be passed and this can be quite painful. Occasionally the stone fragments themselves can block the kidney requiring further surgery. For the appropriate stone it is very successful.
Ureteroscopy / Pyeloscopy
These techniques are essentially variations of the same surgery. A flexible or semi-rigid tube is passed through the natural urinary passages to the bladder and on to either the ureter (Ureteroscopy) or kidney (Pyeloscopy). These techniques allow the stone to be visualised and then usually a laser is used to fragment the stones into small enough pieces to be removed.
After the stone fragments have been removed the ureter is inspected for any damage caused by the stone. Occasionally a JJ stent is left in place to allow healing without scarring. This is usually removed after 2-3 weeks.
This stands for PerCutaneous NephroLithotripsy. This therapy is usually performed for larger stones in the kidney. Utilising X-ray guidance a small calibre tube (about the size of your ring finger) is inserted into the kidney through the skin in your back. This allows direct access to the stone that can be fragmented and removed. This technique is regarded as having the highest stone clearance rate, though it also usually entails 1-2 nights in hospital.
A nephrostomy tube is often left in the kidney for 24 hours after the procedure. It is removed before discharge from the hospital.
It is extremely rare these days that open surgery (that is surgery that uses a formal incision) is required for the treatment of kidney stones.