Urinary stones can form throughout the urinary tract and are medically referred to as “urolithiasis.” Depending on where the urinary stones occur, they are classified as kidney stones (nephrolithiasis)—which include caliceal stones, renal pelvis stones, and staghorn stones—or ureter stones (ureterolithiasis). Bladder stones are a special group of urinary stones, as their formation is mainly associated with bladder emptying disorders and infections. Approximately 12% of the global population suffers from urinary stone formation. In Austria, this diagnosis accounts for about 20,000 hospital admissions per year, making urolithiasis one of the major public health issues alongside cardiovascular diseases and diabetes.

Urinary stone formation involves crystallized compounds forming between an organic matrix and minerals from the urine. The most common types of stones are calcium oxalates (about 75% of all stones), uric acid stones and urates (about 15%), and phosphates (about 10%). Rare types of stones include genetic stones (e.g., cystine stones) and drug-induced stones (indinavir stones, sulfonamide stones).

Crystals can form in a supersaturated solution and occur either spontaneously or on a foreign body. In a complex biological system like the human urinary tract, this process is influenced by many factors. In addition to chemical factors (concentration of stone-forming substances and inhibitors, pH value), anatomical factors (e.g., flow rate) can play an important role. The main risk factors for stone formation include genetic factors, low fluid intake, unbalanced diet (high intake of animal protein and salt), obesity, metabolic diseases, urinary tract infections, or anatomical causes such as a narrowing of the ureter.

The symptoms of urolithiasis can vary and mainly depend on the location and size of the stones. While kidney stones often cause no symptoms for a long time and even a large kidney stone may go unnoticed by the patient, ureter stones can lead to renal colic and pain in the lower abdomen, groin, and/or testicular area. Other symptoms include strong urge to urinate, problems with urination, and blood in the urine. An increased tendency to urinary tract infections may indicate the presence of stones in the urinary tract.

With typical symptoms or a history of stone formation, urolithiasis can be suspected. Clinical examination often provides further clues. Ultrasound examination can reliably depict stones in the kidney and bladder. Ureter stones are rarely visible on sonography and can only be suspected in the presence of urinary stasis. Urinalysis helps to detect an accompanying and potentially dangerous urinary tract infection.

More detailed information about the location, size, and type of stones can be determined by radiographic examinations. Currently, computed tomography without contrast medium is considered the gold standard of diagnosis. In some situations, an X-ray examination with contrast medium is indicated. Follow-up monitoring can be conducted with simple radiographs for radiopaque stones.

Treatment is based on the clinical situation and is individually tailored to each patient. Small kidney stones can be observed in some asymptomatic patients. An exception is made for professional groups where a renal colic could lead to catastrophic consequences (pilots, truck, and bus drivers, etc.). Ureter stones smaller than 5-6 mm pass on their own in most cases. Unfortunately, there is no way to accurately predict how long the stone will take to pass. Severe recurring colics often make waiting for the stone to pass agonizing. Conservative therapy with anti-inflammatory and antispasmodic medications combined with an alpha-blocker can slightly accelerate spontaneous stone passage. In cases of unbearable pain, surgical stone removal must be initiated. An accompanying urinary tract infection is potentially life-threatening and represents an immediate indication for urinary diversion.

Technical advancements in recent decades have revolutionized stone therapy. Thanks to modern technology, urinary stones can now be treated minimally invasively or even non-invasively, meaning without any skin incision or with just a small incision. Key achievements include the establishment of extracorporeal shock wave lithotripsy (ESWL), the development of modern endoscopes for the ureter (URS) and the kidney (pcNL), and the energy sources for endoscopic stone fragmentation, primarily laser technology.