How are kidney stones formed?
Urinary lithiasis is a disease whose prevalence is increasing in our environment, standing at around 5-10% of the population. Moreover, it usually affects the working population and has a considerable tendency to recur, with 50% of patients having a recurrence after approximately 10 years. In a way, in many cases, urinary lithiasis should be considered as a chronic disease to which we should pay special attention in its prevention and treatment.
Human urine is supersaturated in certain salts, which are the substrate from which urinary calculus formation begins. However, our metabolism has a series of inhibiting substances that prevent the formation of lithiasis despite this oversaturation situation. Examples of these substances are citrate and magnesium, among many others. A deficit in these inhibitors will consequently favor lithogenesis.
On the other hand, there are certain situations that predispose to the formation of urinary lithiasis, which we will divide from a didactic point of view into metabolic and non-metabolic factors. Among the metabolic causes we find alterations in which our organism eliminates certain components in excess: oxalate, calcium, uric acid, cystine… or alterations in urinary pH that predispose to the formation of some types of lithiasis.
Non-metabolic causes include environmental or dietary situations such as sedentary lifestyles, low water intake, certain eating habits or professions and the temperature of the geographical area in which one lives. In addition, there are genetic alterations such as primary hyperoxaluria or cystinuria, among others. Finally, the presence of infection in the urinary tract, anatomical abnormalities in which there is some impairment in urine drainage or the presence of foreign bodies in the urinary tract, such as catheters or probes, predispose to stone formation.
What symptoms indicate kidney stones?
The clinical spectrum of urinary lithiasis is varied. The most typical form of presentation is renal colic: intense pain in the affected renal area, sometimes radiating to the genital region on that side, which can be associated with nausea and vomiting, as well as some type of urinary discomfort. However, in a considerable percentage of patients, lithiasis is detected asymptomatically when an abdominal imaging study is performed for another reason. Other forms of presentation of urinary calculi are dull lumbar pain, bleeding in the urine, repeated urinary tract infections and, in the most advanced cases, symptoms derived from renal insufficiency.
What treatment options are available to resolve urinary lithiasis?
The most favorable situation is that the patient can eliminate the lithiasis spontaneously, with greater or lesser need for analgesia, and without additional complications. In general, the size and location of the stone are factors that influence its likelihood of expulsion.
In cases in which the stone cannot be expelled, interventional treatment of the lithiasis should be proposed. Different technical options are available:
- Extracorporeal shock wave lithotripsy (ESWL).
- Ureteroscopy (URS).
- Retrograde intrarenal surgery (RIRS).
- Percutaneous nephrolithotomy (PNL).
- The combination of the last 2 in Endoscopic Combined IntraRenal Surgery (ECIRS).
ESCRS allows the fragmentation of the stone into smaller lithiasis that the patient must subsequently eliminate by himself. It is performed on an outpatient basis and its main limitation is stones with a diameter greater than 1.5-2 cm, or those that are harder due to their composition.
The rest of the technical options previously described are performed in the operating room, and some of them can also be performed in an outpatient surgery program, provided that the necessary experience is available.
URS consists of introducing an endoscope through the patient’s urethra to access the bladder and from there the ureter. The stone is located, usually fragmented by laser and the fragments are removed in the same surgical act. Its main indication is ureteral lithiasis >1 cm, of greater hardness or after failure of ESWL.
RIRS uses the same transurethral access, but here the endoscope is longer and more flexible, allowing entry into the kidney to treat lithiasis located in the renal pelvis and/or its calyces. The main limitation of this technique is also the volume of the stone, which conditions the surgical time. In fact, it is possible that more than one operation may be necessary to completely resolve lithiasis of more than 2 cm in diameter.
PNL consists of making an orifice through the patient’s flank directly into one of the renal calyces. Endoscopes are introduced through this communication to locate the stones, fragment them with different energy sources and finally extract them. It is the technique of choice for lithiasis > 2 cm, complex, or when other techniques have failed. The caliber of the percutaneous access will vary according to the characteristics of the lithiasis and the patient’s anatomy, and orifices ranging from 1.6 mm to 8 mm in diameter can currently be performed.
ECIRS combines the percutaneous access of PNL with the transurethral access of RIRS. The endoscope introduced from the patient’s flank and the flexible ureteroscope instrumented through the urethra work simultaneously, allowing more efficient stone removal and comprehensive access to the entire urinary tract. This combined approach avoids the need for more than one orifice to the kidney in complex stones.
How important is it to treat stone disease correctly and on time?
Our goal is to prevent established and unrecoverable kidney damage from occurring as a result of the stone when it obstructs the urinary tract. A ureteral or renal stone that completely obstructs urinary drainage eventually causes irreversible damage to renal function within weeks.
The concept of “time is kidney” is critical and should guide our prioritization of patients awaiting intervention. If we perform the right treatment at the right time, the lifespan of the kidneys should not be affected at all. With the techniques we are performing right now, all minimally invasive, we can even improve function in some patients. We have demonstrated in research carried out in my doctoral thesis that the damage of these surgeries on the kidney is minimal or non-existent.
What are the benefits of percutaneous nephrolithotomy and ECIRS, of which you are an international reference?
These techniques can completely eliminate renal and/or ureteral lithiasis in a patient, regardless of its volume and complexity, in a reasonable surgical time and with a minimum incidence of complications.
The possibility of individualizing the caliber of the percutaneous orifice allows us to design a tailor-made suit for each case, seeking to combine the greatest effectiveness in a single surgical act with the lowest possible incidence of complications. Furthermore, we have shown that the application of these techniques also improves the quality of life of patients, and that urinary lithiasis per se causes a considerable deterioration in this quality of life.
What are the results?
The operated patients are usually discharged within 24-48 hours, with minimal discomfort. An internal urinary catheter is usually left in place to reduce the incidence of complications, which is removed after 7-10 days on an outpatient basis.
The return to work is, therefore, very fast and without sequelae. However, the results clearly depend on the surgeon’s experience and the availability of the necessary technology to carry out these procedures. The techniques of NLP and ECIRS require a long training and learning curve, estimated at 80-100 interventions, depending on the complexity of the cases treated.
After the intervention, a comprehensive assessment of the risk of new stone formation must be performed and the patient will be worked with individually to prevent or delay the occurrence of new episodes.
What recommendations would you give to a patient with urinary calculi?
Patients with urinary calculi or a history of lithiasis should consult a urologist specialized in this disease. In many cases the development of new stones can be prevented by an individualized study of risk factors, identifying and correcting metabolic and non-metabolic causes. In patients who already have stones in the urinary tract, the risk of progression of this lithiasis should be studied and the need for treatment should be assessed, as well as the most efficient way to resolve it.
It is important to insist on the importance of not delaying the treatment of urinary calculi, especially if there is associated obstruction, since this will lead to irreversible loss of renal function. A quick resolution of the problem without sequelae is essential in the context of a chronic disease such as urinary lithiasis.
On the other hand, many of these patients with obstructive stones, prior to treatment, will have an internal (double J catheter) or external (percutaneous nephrostomy) ureteral catheter implanted, which allows temporary unblocking of the urinary tract while the lithiasis is not treated. These catheters cause discomfort in a considerable percentage of patients and have a negative impact on their quality of life. In addition, over time these devices tend to encrustation and calcification, causing more symptoms, losing their drainage function and causing damage to the urinary tract. Again, rapid resolution of lithiasis by minimally invasive techniques will reduce catheter time and morbidity.
For more information about these techniques, contact Dr. Perez Fentes, a specialist in Urology with practice in Santiago de Compostela.