Bladder stones are hard masses of mineral deposits that form inside the bladder. They are distinct from kidney stones primarily by location, though both share a composition of crystallized minerals found in urine. Successful treatment depends heavily on the stone’s chemical makeup, as certain types can be dissolved with medication, while others require physical removal.
Bladder Stone Formation and Composition
Bladder stones often form when the bladder cannot empty completely, leading to urinary stasis. This incomplete emptying causes stagnant urine to become overly concentrated, allowing minerals to crystallize and clump together. Common reasons for stasis include an enlarged prostate (benign prostatic hyperplasia), a neurogenic bladder that impairs nerve function, or the presence of a foreign body like a catheter.
The stone’s composition dictates whether chemical dissolution is a possible treatment path. Uric acid stones are the most common type found in adults, often accounting for over 50% of cases. They form when the urine is persistently too acidic (pH below 5.5), causing the normally soluble urate to convert into less soluble uric acid crystals.
Other common types, such as calcium stones (calcium oxalate and calcium phosphate) and struvite stones, generally resist chemical dissolution. Struvite stones (composed of magnesium, ammonium, and phosphate) are almost always associated with a urinary tract infection caused by specific bacteria that make the urine highly alkaline. Calcium stones often originate in the kidney and grow larger after migrating to the bladder.
Determining if Dissolution is an Option
Medical professionals must first confirm the stone’s composition to determine if dissolution is a viable strategy. This process starts with a physical examination and a urinalysis, checking for infection, blood, and crystals in the urine. A consistently low urinary pH strongly indicates a potential uric acid stone.
Imaging studies are necessary to visualize the stone’s size and location. X-rays may not always show uric acid stones because they are radiolucent, but computed tomography (CT) scans and ultrasounds reliably detect them. A dual-energy CT scan is a specialized technique that can sometimes predict stone composition by analyzing X-ray absorption, helping distinguish uric acid stones from other types.
The decision to attempt dissolution hinges on confirming the stone is uric acid-based. If a stone has been passed or surgically removed, a formal stone analysis provides definitive confirmation of its chemical makeup. Without this confirmation, medical dissolution is rarely attempted, as it is ineffective for calcium and struvite stones.
Medical Strategies for Stone Dissolution
The primary medical strategy for dissolving uric acid bladder stones is pharmacologic chemolysis, which involves systematically raising the urine’s pH. This method, known as urinary alkalinization, uses oral medications to make the urine less acidic. The goal is to convert the insoluble uric acid crystals back into the highly soluble urate form, allowing them to be flushed out.
The most common medication used is potassium citrate; sodium bicarbonate is an alternative if potassium citrate is not tolerated. The medication is dosed to achieve a target urinary pH level, typically maintained between 6.0 and 6.5. Maintaining the urine pH above 6.5 is optimal for dissolution, as uric acid is significantly more soluble in alkaline urine than in acidic urine.
This treatment requires careful and consistent monitoring of the urinary pH, often done by the patient at home using test strips, to ensure the level remains within the therapeutic range. Overly aggressive alkalinization (raising the pH too high) can be counterproductive, potentially causing calcium phosphate crystals to form on the existing uric acid stone, stopping the dissolution process. The timeline for successful dissolution varies, but this therapy is effective for a large percentage of uric acid stones.
Preventing Recurrence and Alternative Treatments
Preventing the recurrence of any bladder stone requires addressing the underlying cause, most often incomplete bladder emptying. For men, this frequently involves treating an enlarged prostate with medication or surgery to ensure the bladder fully empties. Maintaining a high fluid intake to ensure a large urine volume is a primary defense against stone formation.
Dietary modifications are tailored to the specific stone type identified. Patients with uric acid stones may be advised to limit foods high in purines, such as red meat and organ meats, to reduce uric acid production. Continuing potassium citrate therapy also serves a preventive role by keeping the urine alkaline, which discourages the formation of new uric acid crystals.
If the stone is not uric acid-based, or if dissolution therapy fails, alternative treatments are necessary. These non-dissolution procedures include transurethral cystolitholapaxy, where a scope is inserted through the urethra to fragment the stone using a laser or other device, and the pieces are then removed. For large or hard stones, or if the underlying cause is complex, open surgery (cystostomy) may be required to physically remove the calculus.