Kidney stones (renal calculi) are hard mineral deposits that form inside the kidneys. An obstructed kidney stone occurs when a stone lodges itself in the ureter, the narrow tube connecting the kidney to the bladder, halting the flow of urine. This blockage transforms a painful condition into a potentially urgent medical crisis that can threaten kidney function and even life.
Understanding the Blockage
The urinary system is designed for continuous flow from the kidney to the bladder. When a stone gets stuck in the ureter, the urine backs up. This back-pressure leads to a condition called hydronephrosis, which is the swelling and enlargement of the kidney’s urine-collecting system.
The resulting pressure buildup within the kidney can be dangerous. This sustained high pressure can rapidly compromise the kidney’s ability to filter waste and maintain normal function. If the obstruction is not relieved promptly, the kidney tissue can become damaged, leading to permanent loss of kidney function on the affected side. The obstruction is also the primary cause of the intense, wave-like pain, known as renal colic, as the body attempts to force urine past the immobile stone.
Identifying Emergency Symptoms
Recognizing the signs of an obstructed stone is important, as certain symptoms mandate immediate emergency care. The most common symptom is severe, intractable flank or back pain, often described as some of the worst pain a person can experience. This pain, which may radiate down toward the groin, does not lessen with changes in position and typically requires professional medical intervention for relief.
A fever above 100.4 degrees Fahrenheit (38 degrees Celsius) or the presence of chills alongside the pain is a particularly dangerous combination. This indicates that the trapped urine has become infected, a condition known as pyelonephritis, which can quickly progress to life-threatening sepsis. Persistent nausea and vomiting can also occur due to the extreme pain and the shared nerve pathways between the kidneys and the stomach. The presence of blood in the urine, or hematuria, is another common sign of a stone irritating the lining of the urinary tract.
How Doctors Confirm Obstruction
When a patient with suspected renal colic arrives at the hospital, doctors confirm the stone’s presence and the degree of obstruction using imaging. A noncontrast Computed Tomography (CT) scan is often considered the gold standard for stone diagnosis. It precisely determines the stone’s size, location, and density, as well as confirms the presence of hydronephrosis.
Ultrasound is also a valuable tool, particularly in the emergency setting or for patients who need to avoid radiation, such as pregnant individuals. Ultrasound is highly effective at visualizing the swelling in the kidney caused by the backup of urine. Laboratory tests are performed concurrently to evaluate the patient’s overall health and rule out infection. Blood work typically includes checking kidney function markers like creatinine, and a urine analysis checks for the presence of blood, white blood cells, or bacteria, which are indicators of infection.
Procedures to Clear the Blockage
The immediate goal in treating an acutely obstructed kidney stone, especially when infection is present, is to relieve dangerous pressure and drain the infected urine. This urgent drainage is accomplished through two main procedures.
A ureteral stent is a thin, hollow tube placed inside the ureter, extending from the kidney to the bladder, to bypass the obstruction and allow urine to flow freely. This minimally invasive procedure is often performed using a small scope passed through the urethra and bladder.
The second drainage option is a percutaneous nephrostomy tube. This involves placing a small tube directly through the skin in the patient’s back and into the kidney’s urine-collecting system. This external drain provides immediate relief from pressure and allows infected urine to exit the body. The choice between a stent and a nephrostomy tube depends on the patient’s condition and the surgeon’s preference, but both procedures are effective for urgent decompression.
These drainage procedures are temporary measures designed to stabilize the patient and resolve infection or kidney failure before definitive stone removal is attempted. Once the immediate crisis is controlled, definitive treatment focuses on removing or fragmenting the stone.
Ureteroscopy (URS) is a common procedure where a small scope is passed up the urinary tract to the stone, which is then broken up using a laser and the fragments are removed. Another approach is Extracorporeal Shock Wave Lithotripsy (ESWL), which uses focused sound waves delivered through the skin to break the stone into tiny pieces that can be passed naturally. The selection of the final procedure is determined by factors like the stone’s size, location, and composition. The urgent drainage step is performed to preserve kidney function, while the later procedure aims to permanently eliminate the stone.