Kidney stones are small, hard masses composed of crystallized minerals and salts that form inside the kidneys. These formations often remain asymptomatic while residing in the wider kidney structures. Pain typically begins when a stone detaches and attempts to pass through the narrow tubes of the urinary tract, creating one of the most intense pain experiences known. The severity of the pain changes dramatically depending on the stone’s location, which is why the discomfort level is significantly different once the stone reaches the bladder.
Why Ureteral Movement Causes Severe Pain
The most intense and well-known pain associated with passing a stone, called renal colic, happens when the formation enters the ureter. The ureter connects the kidney to the bladder and is only about four millimeters in diameter. When a stone attempts to travel down this narrow passage, it can become lodged and obstruct the flow of urine. This blockage causes urine to back up, leading to a rapid pressure increase inside the kidney, which stretches the surrounding renal capsule. The body attempts to dislodge the stone through powerful, involuntary muscular contractions in the ureter wall, which causes the characteristic cramping, wave-like pain. This severe discomfort is often felt suddenly in the flank or side, just below the ribs, and frequently radiates down toward the lower abdomen and groin area.
Pain Levels Upon Reaching the Bladder
Once the stone enters the bladder, the severe, cramping pain of renal colic typically stops or significantly eases. The bladder is built to store urine, so the stone no longer causes the obstructive pressure that led to kidney swelling. The relief from the intense flank and back pain occurs as the kidney’s plumbing system is no longer blocked. However, the stone introduces new, localized sensations that replace the systemic pain. The stone rests against the sensitive inner lining of the bladder, causing irritation to the tissue. This irritation translates into symptoms closely resembling those of a common bladder infection. Individuals often experience a sudden and increased urgency to urinate, along with a frequent need to go. They may also feel a dull pressure or mild, persistent discomfort in the lower abdomen or pelvic region.
The Final Obstacle: Urethral Passage
The stone’s journey is not complete upon reaching the bladder, as it still needs to exit the body through the urethra. The urethra is narrower than the bladder but usually wider than the ureter. The discomfort during this final expulsion is typically brief but can be sharp. As the stone passes through the urethra, people often report a stinging or burning sensation during the act of urination, a symptom known as dysuria. For very small stones, this passage may happen quickly and without significant notice. Larger stones can cause temporary discomfort as they scrape against the delicate urethral lining. It is common to see blood in the urine during this phase due to the stone irritating the lining of the urinary tract. Once the stone is fully expelled, the symptoms should resolve entirely. Capturing the stone, if possible, is helpful for later chemical analysis to determine its composition.
When to Contact a Healthcare Provider
While most small stones pass naturally with supportive care, certain symptoms require immediate contact with a healthcare provider. The presence of a fever or chills alongside pain can signal a serious infection in the kidney, which requires prompt antibiotic treatment. An infection combined with a stone obstruction is a time-sensitive medical concern. Intractable pain that cannot be managed with prescribed or over-the-counter medication is another important sign to seek medical assistance. An inability to pass any urine, known as anuria, is a serious complication that suggests a complete blockage of the urinary flow. This situation needs urgent intervention. Follow-up appointments are also important for analyzing the passed stone and developing a prevention plan to reduce the risk of future occurrences.