EPIDEMIOLOGY AND PATHOGENESIS OF RENAL CALCULI (KIDNEY STONES)
The formation of urinary calculi or kidney stones is a common condition characterized by the presence of solid aggregates of varying shape and structure that might be located inside the kidneys, urinary tract or bladder. This pathology is more frequent between the ages of 50 and 60, although it can occur at any age and affects males more than females. During their lifetime, approximately one person out of ten will experience stones-related problems. Although various metabolic disorders, alterations in the pH and urinary electrolytes seem to be involved in the pathogenesis, in most cases it is not possible to distinguish a real cause.
The onset symptoms is predominantly colic-type with pain in the flank and / or lumbar region(s). This can also be very intense and be accompanied by nausea, vomiting, fever, pain when urinating and, sometimes, the presence of blood in the urine. Most of the times, the colic starts at night or in the early morning, waking up the patient who suddenly feels acute pain in the lumbar area which is typically “poussé” (i.e. that comes and goes) and that reaches its maximum quickly but can just as quickly disappear. The diagnosis, beyond the symptomatology, can be made through an ultrasound of the abdomen which can identify the presence of the stone. In cases where there is a strong suspicion of calculosis but the ultrasound is not suitable to identify its position, it may be necessary to undergo an abdominal CT scan without contrast medium.
MEDICAL THERAPY OF RENAL CALCULOSIS
If the stone is less than one centimeter in diameter and there are no signs of a concomitant infection or kidney damage, conservative therapy can be attempted by educating the patient to drink a lot of water and to do a lot of physical activity to encourage spontaneous expulsion of the calculus. Additionally, drugs normally used for prostatic hypertrophy (tamsulosin, silodosin) are often prescribed in order to promote the relaxation of the ureteral musculature and therefore increase the probability of success.
SURGICAL THERAPY OF KIDNEY STONES: LITHOTRIPSY
Extracorporeal lithotripsy: Extracorporeal lithotripsy consists in the fragmentation of the calculation through the application of shock waves generated externally by a lithotripter. Shock waves are conveyed towards the target with intensity and frequency that can be modulated according to the characteristics of the patient and the stone. Several sessions may be needed to reduce the stone to small fragments that are susceptible to spontaneous expulsion in the urine. This procedure can also be performed on a day hospital basis in selected patients, with a high success rate.
Laser lithotripsy ureterorenoscopy (RIRS)
According to the latest studies, retrograde intrarenal surgery (RIRS) is the technique that is mostly used for the treatment of urinary stones, representing more than 60% of the surgical procedures performed in Europe for this pathology. These data are confirmed in the guidelines of the European Association of Urology, which consider RIRS to be the gold standard treatment for stones located in the ureter and kidney. Surgery involves accessing the ureter and renal pelvis with a retrograde technique, passing through the urethra and bladder. A flexible endoscopic instrument is used, through which the laser fiber passes which will subsequently be used for the fragmentation of the calculation. Once the lithiasic formation has been identified, it is possible to proceed with direct lithotripsy using a Holmium laser which, thanks to the low penetrance in the tissues and the high energies delivered, allows to fragment any type of stone, minimizing the risk of damaging the surrounding tissues. This technique is characterized by a high percentage of patients in whom the “stone-free” state is reached, that is, the complete fragmentation of the stone without the need for further surgical interventions. This is true even in the presence of large stones or multiple lithiasic formations.
SURGICAL THERAPY OF KIDNEY STONES: PERCUTANEOUS NEPHROLITHOTOMY
Percutaneous nephrolithotomy is usually offered to patients with bulky and complex renal calculi, in which a pure retrograde endoscopic approach would not guarantee a good result in terms of complete reclamation of the lithiasic mass. The European guidelines recommend considering this treatment in the case of stones> 2 cm. This technique allows to directly reach the intrarenal cavities and the calculation through a puncture of the kidney and the creation of a small cavity between the skin and the renal parenchyma. Once the access to the intrarenal cavities has been created, a dilation of the passage is performed which allows the insertion of the operative instruments, or the nephroscope, and of the lithotripsy sources (Holmium laser), to fragment the calculation and then remove the residual fragments with pliers and baskets. Percutaneous nephrolithotomy can be performed also in the supine position. The main advantage of this approach consists in being able to operate simultaneously retrogradely through a flexible ureterorenoscope. Furthermore, our center has been involved in the development and use of very small operating tools, which work through a very small medium (about 3-5 mm) and which allow the so-called mini-PNL to be carried out, limiting the invasiveness of the procedure and the risk of complications and bleeding for the patient with comparable success rates.
FOLLOW-UP: WATER INTAKE AND DIET
Urolithiasis is a disease that has a marked tendency to relapse (40-50% of patients have a recurrence at 5 years and more than 50-60% at 10 years). This might be attributable to imbalances in the composition of the urine, such as the increased excretion of calcium (hypercalciuria), uric acid (hyperuricuria) or oxalate (hyperoxaluria) and the reduced excretion of citrate (hypocitraturia). Knowledge of the composition of the stone and of certain urinary parameters is fundamental for the therapeutic setting. A proper diet is the ‘first cure’ for the prevention of kidney stones, as the composition of the urine is directly related to the diet: this is aimed to reduce the precipitation of the urinary salts in question and / or the increase of substances that prevent its precipitation.
Dietary therapy must therefore be specific to the type of stone even if general indications apply (such as that of drinking 2-3 liters of water per day to be distributed evenly over 24 hours) and to maintain, or reach if necessary, a certain body weight through a balanced dietary approach with low salt content, animal proteins and simple sugars, high consumption of fruit and vegetables and cereals. The choice of water should also be personalized, considering the overall contribution of micronutrients such as calcium, sodium, potassium, chlorine and magnesium. Yet, all sugary carbonated drinks, concentrated tea (rich in oxalates) and alcohol (avoid the levels of excretion of oxalic acid and uric acid) should be avoided.