What are urinary stones?
Urinary stones, also called urinary lithiasis, are hard concretions that form in the urinary tract from crystals present in the urine. They can be in the kidney (kidney stones), in the ureter (ureteral stones), in the bladder (bladder stones) or, more rarely, in the urethra.
The size of stones varies widely, from a few millimeters to several centimeters. Their composition is also variable: calcium oxalate (the most frequent), uric acid, struvite, cystine, etc. The composition of the stone influences both its mode of formation and the appropriate preventive treatment.
Causes and risk factors
Several factors favor the formation of urinary stones:
- Insufficient hydration: a low daily intake of water concentrates the urine and promotes crystallization.
- Diet: excessive consumption of salt, animal proteins, oxalates (spinach, chocolate, nuts) or sugars.
- Family history: a hereditary predisposition is observed in some patients.
- Metabolic pathologies: gout, hyperparathyroidism, certain digestive diseases.
- Recurrent urinary infections, for struvite stones.
- Anatomical abnormalities of the urinary tract that hinder urine flow.
Symptoms of urinary stones
A urinary stone may remain silent for a long time, particularly when it is in the kidney. Symptoms appear when the stone migrates into the ureter and obstructs the flow of urine.
The most characteristic symptom is renal colic: intense, sudden flank pain radiating to the lower abdomen and the genital organs. Other signs may be associated:
- Blood in the urine (hematuria).
- Frequent urge to urinate, burning when urinating.
- Nausea, vomiting.
- Fever in case of associated infection.
The presence of fever associated with renal colic constitutes a medical emergency requiring rapid management.
Diagnosis
The diagnosis of urinary stones is based on the clinical examination, complemented by imaging tests. The non-injected abdomino-pelvic CT scan is currently the reference test: it visualizes all stones, regardless of their composition, and specifies their location, size, and any complications (urinary tract dilatation).
Renal-vesical ultrasound can also be used, particularly in pregnant women or for follow-up.
Treatments for urinary stones
Treatment depends on the size of the stone, its location, the composition (when known), and the symptoms.
Medical treatment
For small stones (less than 5 mm), spontaneous passage in the urine is often possible. Treatment consists of:
- Abundant hydration.
- Analgesic and anti-inflammatory medications.
- Medications facilitating passage (alpha-blockers).
Extracorporeal shock wave lithotripsy (ESWL)
This non-invasive technique uses external shock waves to fragment the stone. The fragments are then eliminated naturally in the urine. It is indicated for kidney or upper ureteral stones of moderate size.
Flexible ureteroscopy with laser
A reference technique for stones not accessible to lithotripsy, or after its failure. A flexible endoscope is introduced through natural channels up to the stone, which is then fragmented by Holmium laser. The fragments are removed or eliminated naturally.
Percutaneous nephrolithotomy (PCNL)
Reserved for large kidney stones. It consists of accessing the kidney through a small skin incision in the lumbar region to fragment and extract the stone.
Prevention of recurrence
After an episode of urinary stones, prevention of recurrence is essential. It is based on:
- Abundant hydration (at least 2 liters of water per day, evenly distributed throughout the day).
- A balanced diet, low in salt and animal proteins.
- Treatment of any associated metabolic factor.
- Regular urological follow-up.
A morphoconstitutional analysis of the stone, when one is recovered, makes it possible to determine its precise composition and to adapt prevention.
Dr Adam Vardi, a urological surgeon in Paris, is a specialist in the management of urinary stones. He performs the most modern techniques: flexible ureteroscopy with Holmium laser and percutaneous nephrolithotomy.