Bladder stones that stay in place don’t just sit there quietly. Over time, they grow larger, cause worsening pain and urinary problems, create a breeding ground for infections, and in rare cases contribute to bladder cancer. The longer a stone remains, the more damage it can do to the bladder wall and, potentially, the kidneys.
Symptoms Get Worse Over Time
A small bladder stone may cause no symptoms at all in the early stages. But as the stone grows or shifts position, it begins to irritate the bladder lining. You may notice pain in the lower abdomen, burning during urination, blood in the urine, or a frequent urgent need to go. These symptoms tend to come and go at first, then become more persistent as the stone enlarges.
One of the more disruptive symptoms is an interrupted urine stream. The stone can roll over the bladder opening and temporarily block urine flow mid-stream, forcing you to stop and start repeatedly. Some people find they can only urinate in certain positions because gravity shifts the stone away from the opening. Over months, the bladder muscle works harder to push urine past the obstruction, which can thicken and weaken the bladder wall.
Recurrent Urinary Tract Infections
Bladder stones harbor bacteria inside their porous, mineral structure. Antibiotics can kill the bacteria circulating in urine, but they often can’t penetrate deeply enough into the stone itself. This means infections clear up temporarily with treatment, then return weeks or months later because the stone keeps reseeding the bladder with the same organisms. These recurring infections can become increasingly difficult to treat, especially if the bacteria develop resistance to common antibiotics over time.
Each infection also causes inflammation, which further irritates the already-damaged bladder lining and can worsen urinary symptoms. In older adults or people with weakened immune systems, repeated urinary infections carry a real risk of spreading to the bloodstream.
Complete Urinary Blockage
The most acute risk of an untreated bladder stone is a full blockage of urine flow. If a stone lodges in the bladder neck or the opening of the urethra, it can completely stop urine from leaving the body. This is called acute urinary retention, and it’s a medical emergency. The bladder fills and distends painfully, and without prompt intervention (usually a catheter to drain the urine), the pressure backs up toward the kidneys.
Even partial obstruction, sustained over weeks or months, forces urine to remain in the bladder longer than it should. The residual urine sitting in the bladder encourages bacterial growth and creates a cycle: the stone causes incomplete emptying, which promotes infection, which causes inflammation, which makes emptying even harder.
Kidney Damage From Backed-Up Pressure
When a bladder stone blocks or significantly restricts urine outflow for an extended period, pressure builds backward through the ureters and into the kidneys. This causes the kidneys to swell, a condition called hydronephrosis. In the early stages, hydronephrosis is reversible once the blockage is cleared. But if the obstruction persists for weeks to months, the sustained pressure damages the delicate filtering structures inside the kidney.
Severe or prolonged hydronephrosis can lead to permanent kidney damage and, in the worst cases, kidney failure. This is one of the most serious consequences of leaving a bladder stone untreated, because kidney damage is often silent. You may not feel kidney-specific symptoms until significant function has already been lost. The risk is higher in people who already have one functioning kidney or pre-existing kidney disease.
Increased Bladder Cancer Risk
Long-standing bladder stones are associated with a higher risk of bladder cancer, particularly a type called squamous cell carcinoma. The mechanism is chronic irritation: a stone sitting against the bladder wall for years causes ongoing inflammation, which over time can trigger abnormal cell changes.
A case-control study found that people with a history of bladder stones had roughly twice the risk of developing bladder cancer compared to those without stones, independent of urinary tract infections. Another analysis put the odds even higher, with patients diagnosed with bladder cancer being about 3.4 times more likely to have had a prior bladder stone than controls. These are not common outcomes, and no large-scale studies have established exactly how often squamous cell carcinoma develops alongside bladder stones. But the association is consistent enough that long-term stones are considered a recognized risk factor.
Can Bladder Stones Pass on Their Own?
Small stones sometimes pass through the urethra without intervention, but the odds depend heavily on size. Data on urinary stones shows that stones 3 mm or smaller pass on their own about 98% of the time. At 5 mm, the passage rate drops to around 65%. At 6 mm, only about a third pass spontaneously, and stones 6.5 mm or larger have roughly a 9% chance of passing without help.
These numbers come from studies of ureteral stones (stones in the tube between the kidney and bladder), and the dynamics differ slightly for stones already sitting in the bladder. Bladder stones that formed in place, rather than traveling down from the kidney, tend to be larger by the time they cause symptoms. Many are well over 10 mm. At that size, spontaneous passage is essentially impossible, and the stone will continue to grow as more minerals crystallize onto its surface. Waiting and hoping rarely works for stones that have had time to establish themselves in the bladder.
Children Face Additional Risks
In children, untreated bladder stones carry the same risks as in adults, but the stakes can be higher. Children with stones caused by genetic or metabolic conditions are at particular risk of chronic kidney damage if treatment is delayed. Their kidneys are still developing, and sustained obstruction or repeated infections during childhood can impair kidney growth and long-term function in ways that are harder to reverse than in adults. Early identification and removal of stones in pediatric patients is especially important when an underlying genetic predisposition is involved.