It is possible to have kidney stones without experiencing the intense pain often associated with them. Kidney stones are hard masses composed of crystallized minerals and salts that form inside the kidneys, and they can vary significantly in size and composition. While the severe, cramping sensation known as renal colic is the most recognized symptom, a stone can exist quietly within the urinary tract for an extended period.
The Reality of Asymptomatic Kidney Stones
The pain associated with kidney stones, known as renal colic, is not caused by the stone forming in the kidney itself. Pain begins only when the stone moves out of the kidney and becomes lodged in the narrow ureter, the tube connecting the kidney to the bladder. This obstruction of urine flow causes pressure to build up, distending the kidney’s collecting system and triggering pain signals.
A kidney stone remains asymptomatic when it is not actively causing this blockage. This occurs when the stone is either very small, allowing it to pass through the urinary tract undetected, or when it is large but remains stationary within the kidney’s collecting system. Stones resting in the kidney’s lower pole are particularly unlikely to cause symptoms because gravity holds them in place, preventing them from entering the ureter.
Even some relatively large stones, such as staghorn calculi, may not cause acute pain if they do not obstruct urine drainage. The lack of acute obstruction is the most important factor determining whether a stone causes pain or remains silent.
How Silent Stones Are Discovered
Since there is no pain to prompt a doctor’s visit, these asymptomatic stones are almost always discovered by chance. They are typically found incidentally during medical imaging procedures conducted for unrelated health concerns. A patient may undergo an abdominal computed tomography (CT) scan or an ultrasound for back pain, digestive issues, or other screenings, and the stone is spotted in the background.
Ultrasound is a common imaging modality that frequently leads to the incidental discovery of silent kidney stones. This is especially true when a complete abdominal ultrasound is performed for issues not related to the urinary tract. The increased use of advanced cross-sectional imaging has contributed to the higher rate of these unexpected findings.
Risks Associated with Undetected Stones
Despite the absence of pain, a silent kidney stone is not always benign and can pose long-term risks to kidney health. The most significant concern is the potential for chronic, low-grade obstruction of the urinary tract. Over time, even a partial blockage can cause a condition called hydronephrosis, where urine backs up and causes the kidney to swell.
This persistent pressure can gradually lead to scarring and irreversible damage to the kidney tissue, resulting in a decline in kidney function. Additionally, stones act as a protected surface where bacteria can colonize, increasing the risk of recurrent urinary tract infections (UTIs). These infections can escalate into pyelonephritis, a severe kidney infection, or urosepsis, a systemic infection.
Furthermore, a silent stone resting in the kidney can shift its position suddenly. If the stone moves into the ureter, it immediately converts from an asymptomatic finding to a painful episode of renal colic. This unpredictable event can necessitate an emergency room visit and urgent medical intervention.
Management and Monitoring of Asymptomatic Stones
Once a silent stone has been identified, the medical approach involves a decision between active surveillance, also known as the “wait and watch” approach, and proactive intervention. Active surveillance is often appropriate for small, non-obstructing stones, especially those located in the lower pole of the kidney, which are less likely to become symptomatic. This strategy involves regular follow-up imaging, typically with ultrasound, to monitor the stone’s size and position over time.
The decision to intervene proactively is based on several factors, including the stone’s size, its location, and the patient’s general health status. Stones larger than 10 millimeters, or those causing any degree of obstruction or frequent infections, are more likely to require treatment. Intervention methods can include shockwave lithotripsy (SWL), which uses external shockwaves to break the stone into fragments, or ureteroscopy, which involves passing a small scope through the urinary tract to remove or fragment the stone.
The final management plan is a shared decision between the patient and the healthcare provider, weighing the low risk of a stable stone becoming symptomatic against the potential complications and risks of a surgical procedure.