Kidney stones (nephrolithiasis): why they form and how they are treated

“Kidney stones (or nephrolithiasis) are solid formations, similar to small pebbles, that develop within the cavities of the kidney,” explains Dr. Corrado.

These formations can vary greatly in size, from a few millimeters to stones that completely fill the renal cavities, known as staghorn calculi. Kidney stones may also be:

• single or multiple;
• present in one or both kidneys;
• located in the kidney or along the ureter.

Stone formation is a multifactorial process.

“At its origin is the crystallization of substances normally present in urine, such as calcium, oxalates, and uric acid, combined with a reduced presence of substances that inhibit this process, such as citrate,” explains the Villa Erbosa urologist.

The main factors that promote kidney stone formation include:

• genetic predisposition, which may make the condition familial;
• urinary tract infections, often related to urine stagnation;
• congenital abnormalities of the urinary tract.

“Poor hydration and the resulting excessive concentration of urine play a major role in stone formation. For this reason, proper hydration is one of the most important preventive measures, especially in predisposed individuals,” the specialist emphasizes.

Kidney stones may remain asymptomatic for long periods while they stay inside the kidney. Symptoms more commonly appear when the stone moves and travels down the ureter, the duct connecting the kidney to the bladder.

“When the stone obstructs the ureter and blocks the normal flow of urine, dilation of the renal cavities occurs, a condition called hydronephrosis, which causes the typical pain of renal colic,” explains the urologist.

The main symptoms include:

• renal colic, with sudden and intense flank pain;
• blood in the urine, visible or detected through testing;
• fever, when a bacterial infection is present.

A specialist urological evaluation is recommended whenever a kidney stone is detected.

“It is advisable to consult a urologist even when the stone is asymptomatic and discovered incidentally during an ultrasound, because these formations tend to grow over time, making treatment more complex later on,” the doctor states.

A urological consultation is also recommended:

• in the presence of renal colic;
• if fever or signs of urinary infection occur;
• in cases of persistent abdominal pain or blood in the urine.

Diagnosis is based on both clinical evaluation and specific imaging tests.

     Urinary tract ultrasound

“The first-line test usually prescribed when nephrolithiasis is suspected is urinary tract ultrasound, which allows us to:

• identify the stone;
• assess the presence of obstruction.

It is a simple but essential exam that helps determine whether pain is caused by a stone moving through the ureter,” explains the specialist.

     CT urography (Uro-CT scan)

When ultrasound is insufficient, for example, when the stone is not visible or more detailed imaging is required, a CT urography scan is performed. This exam accurately defines:

• the location of the stone;
• its size;
• the number of stones;
• the degree of urinary tract obstruction.

Treatment choice mainly depends on the characteristics of the stone.

     Treatment for small stones

If the stone is small (up to 3–4 mm), spontaneous passage may be attempted. This can be facilitated through:

• adequate hydration (without excess);
• physical activity and movement;
• medications that relax the ureter;
• anti-inflammatory or antibiotic therapy when indicated.

     Treatment for larger stones

When stones are larger and cannot pass spontaneously, treatment is mainly endoscopic, performed under general anesthesia using miniaturized instruments to:

• fragment the stone with a laser;
• remove fragments through the natural urinary pathways.

“In selected cases, extracorporeal shock wave lithotripsy may still be indicated, an outpatient procedure that breaks the stone using shock waves without surgical incisions.

For very large or complex stones, more invasive procedures such as percutaneous or laparoscopic treatments may be necessary,” adds the urologist.

After stone removal, symptoms usually resolve within 24–48 hours, and kidney function generally recovers just as quickly. Minimally invasive treatments also shorten recovery times, allowing a relatively rapid return to daily activities.

However, treatment outcomes may vary depending on factors such as:

• stone size and number;
• location;
• the patient’s overall clinical condition.

An important aspect not to underestimate is the risk of recurrence, which is higher in predisposed individuals.

“For this reason, treatment does not end with stone removal. After therapy, periodic follow-up and personalized preventive measures, starting with proper hydration, are essential to reduce recurrence risk and protect kidney health over time,” concludes Dr. Corrado.