Kidney stones are solid masses formed from crystallized minerals and salts within the urinary tract. These masses can be as small as a grain of sand or grow to the size of a pea or larger, forming within the kidney itself. Understanding the stone’s location is relevant because its migration from the narrow ureter into the bladder marks a significant shift in the pain profile. This change often signals that the most severe phase of discomfort is likely over, preparing for the stone’s final exit.
Understanding the Stone’s Path
A kidney stone begins its journey when it detaches from the kidney and travels through the ureter, a slender tube connecting the kidney to the bladder. The ureter is naturally narrow and transports urine using muscular contractions called peristalsis. When a stone attempts to pass through this tight space, it can block the flow of urine, causing pressure to build up in the kidney. This obstruction and the ureter’s forceful contractions are the source of the fluctuating pain known as renal colic. This pain is typically felt in the flank or side, often radiating toward the abdomen or groin as the stone descends.
Symptom Shift When the Stone Reaches the Bladder
The most noticeable sign that a stone has successfully navigated the ureter and entered the bladder is an abrupt change in the nature of the pain. The severe, colicky pain in the flank or side usually subsides considerably because the stone is no longer lodged in the narrow ureter causing a blockage. This relief indicates the stone has reached the bladder, a much wider organ. Although the sharp, radiating pain eases, the presence of the foreign body irritates the bladder’s lining, leading to a new set of symptoms.
A stone resting in the bladder can mimic the symptoms of a urinary tract infection because the organ is sensitive to irritation. People often report localized pressure or discomfort in the lower pelvic area, directly above the pubic bone. There is also an increase in urinary urgency and frequency—the constant need to urinate, even if the bladder is not full. The stone physically irritating the bladder wall triggers these nerve signals.
Another common sign is the appearance of blood in the urine, medically termed hematuria, which may make the urine appear pink, red, or brown. This bleeding occurs because the stone, especially if it has rough edges, scrapes the delicate lining of the bladder and the lower urinary tract. Unlike the initial pain, this hematuria is usually painless or accompanied by only mild discomfort. This collection of symptoms—relief from flank pain, new pelvic pressure, and urinary changes—indicates that the stone has moved to its final resting place before exiting the body.
The Final Phase of Stone Passage
Once a stone has reached the bladder, the final phase of passage begins: expulsion through the urethra. The stone may rest in the bladder for a period, sometimes days or weeks, but this time is generally much shorter than the journey through the ureter. The bladder’s muscular wall can tolerate the stone until it is flushed out with urination.
As the stone moves from the bladder into the urethra, a person may experience a brief, sharp, or burning sensation during urination. This occurs because the stone is passing through the urethra, which, while wider than the ureter, is still a tight passage. The duration of this final discomfort is usually momentary, occurring only as the stone physically exits the body. Successfully passing the stone often results in immediate and complete relief from all previous urinary symptoms and pain.
Medical Confirmation of Stone Location
Medical professionals use specific imaging techniques to definitively locate a stone and confirm its position within the urinary tract. A non-contrast computed tomography (CT) scan is frequently the preferred diagnostic tool because it provides detailed, cross-sectional images of the entire urinary system. The CT scan can precisely measure the stone’s size and pinpoint its location, confirming if it is lodged in the ureter or resting freely in the bladder.
For certain situations, such as in pregnant patients or when radiation exposure is a concern, a renal ultrasound may be used as an alternative imaging method. Ultrasound uses sound waves to create images and can effectively visualize stones, especially those causing obstruction, but it may not be accurate in detecting very small stones or those in the middle of the ureter. Less frequently, simple X-rays of the abdomen are used, though they can miss non-calcium stones, such as uric acid stones.
After the stone is passed or removed, analysis of its chemical composition is performed. Understanding the stone’s type is important for developing strategies to prevent future stone formation.