Advances in kidney stone treatment

Kidney stones are common. About 15% of men and 5% of women in the UK will be affected by kidney stones at some stage in their life.1 They typically strike people between the ages of 20 and 40, and when an individual has had one stone, there is roughly a 50% chance that he or she will develop another stone within the next 5-10 years. Kidney stones develop when chemicals crystallise that are normally dissolved in the urine. The tendency for this to happen is dependant on a number of factors including the inherent solubility of the chemical; the concentration of each component in the urine; and the presence or absence of various inhibiting or initiating factors. For example, calcium oxalate is extremely insoluble and crystallises fairly readily. Urate is relatively soluble in alkaline urine but relatively insoluble in acidic urine. Small crystals frequently develop in the urine, particularly when the urine is concentrated, but are typically flushed from the system and expelled before they are large enough to cause any substantial problem. If crystals are retained within the collecting system then they may aggregate together or act as a nucleus for further deposition of either the same or a different chemical and so stones are born. The most common kind of stone is calcium oxalate; but others such as calcium phosphate and uric acid are also reasonably common. Stones within the collecting system of the kidney may cause little in the way of symptoms and may grow to a very large size (Staghorn calculi may fill the entirety of the collecting system). Stones typically cause problems when they move into a position in which they obstruct the flow of urine from the kidney to the bladder, typically in the ureter. This causes renal colic, resulting in acute pain. The severity and location of the pain can vary based on the size and location of the stone and its degree of severity. A stone blockage for a prolonged period of time may cause irretrievable loss of function in the kidney. Obstruction accompanied by infection will destroy renal function very quickly and may be accompanied by significant sepsis. Other symptoms may include haematuria (blood in the urine), vomiting, stranguary (the feeling of needing to pass urine continuously) and pain radiating from the loin to the flank and testicle or penis. Most patients with renal colic will present to medical services, which includes either their primary care physician or Accident & Emergency department.

Current treatments

Small stones in the ureter may be treated conservatively in the expectation that with time they will pass on their own. Stones ?4 mm in the lower ureter have a very good chance of passing in a reasonably short time frame. Stones larger than 6mm are much less likely to pass and will often require surgical intervention. There are a number of treatment options available. For stones in the ureter, in-situ lithotripsy and ureteroscopy, using a flexi ureteroscope for access to the upper ureter if required, and laser lithotripsy with the Holmium laser are both highly effective treatments. Lithotripsy in the lower ureter can sometimes be problematic due to the positioning of the stone. Although ureteroscopic access is usually very reliable below the iliac vessels, above them access above them may be more difficult, making it easier to use lithotripsy to target the stone. With the arrival of flexible scopes and reliable laser technology, a very high stone clearance rate can be achieved with a single procedure. There are several treatments for stones in the kidneys. However, the choice is largely determined by the success rate and complication rate for each of the different options. Of particular note is that the complication rate/re-treatment rate for stones in the kidney treated with lithotripsy (ESWL) increases substantially as the stone gets larger. If a steinstrasse1 develops, this can require multiple treatments and ancillary procedures such as the insertion of a stent or ureteroscopic clearance of the ureter. In addition to this, the clearance of stones from the lower pole calyx is very poor when compared to upper and mid pole calyces even if successfully fragmented. This is due to stone fragments remaining in situ and not clearing due to the dependant position of the calyx relative to the renal pelvis and Pelvi-Ureteric Junction (PUJ) obstruction. If lithotripsy is ineffective in fragmenting the stone or it generates a complication (such as a steinstrasse), then surgery will be required to deal with them. There is a demand from patients for low risk surgical procedures that has rapidly gained ground over the last decade. Minimally invasive techniques satisfy both the surgeon and patient’s desire for a swift recovery, shortening the time from treatment to resolution and reducing the time spent in hospital without the need for multiple return visits. A recent report by Frost & Sullivan,2 found that minimally invasive surgery is one of the biggest trends in healthcare and that innovation in this sector is of great importance. Many advances in technology are being made to reflect the demand for speedy operations and recovery times, and improve the success rate across various specialties to advance patient treatment and care.