Kidney stones are a common medical issue that cause intense pain when they become lodged in the ureter, the narrow tube connecting the kidney to the bladder. This blockage prevents urine from draining, leading to a dangerous buildup of pressure and swelling in the kidney, known as hydronephrosis. When a stone creates this obstruction, a ureteral stent is necessary to restore urine flow and protect the kidney from potential long-term damage.
Defining the Ureteral Stent
The ureteral stent is a thin, flexible, hollow tube placed entirely within the urinary tract. These devices are typically constructed from biocompatible polymers, such as polyurethane or silicone, which allow them to remain inside the body for an extended period. Some stents include coatings that reduce friction during insertion and minimize the buildup of mineral deposits, known as encrustation.
The device is often referred to as a “double-J” or “pigtail” stent due to its distinctive shape at both ends. Both the upper and lower tips are coiled into a J-shape to prevent the stent from migrating. The upper coil sits securely within the renal pelvis of the kidney, while the lower coil anchors in the bladder. Adult stents generally measure between 22 and 30 centimeters in length, ensuring they span the distance between the kidney and the bladder. This coiled design is essential for maintaining the device’s position despite the natural peristaltic movements of the ureter and the constant filling and emptying of the bladder.
The Function of the Stent in Stone Management
The stent’s primary function is to bypass the obstruction caused by the kidney stone, ensuring continuous urinary drainage. By creating an alternative channel, the stent allows urine to flow from the kidney into the bladder, relieving the pressure that causes hydronephrosis and severe flank pain. This rapid pressure relief is important, especially if the obstructed urine is infected, as it prevents the infection from ascending and causing urosepsis.
The second function is the passive dilation of the ureter. The stent’s presence gently stretches the walls of the ureter over time. This widening makes it easier for stone fragments to pass naturally after treatments like shock wave lithotripsy, or it prepares the ureter for subsequent surgical procedures, such as ureteroscopy.
The stent acts as a temporary scaffold, keeping the ureter open during periods of acute inflammation or post-operative swelling. It maintains the integrity of the ureteral lumen, protecting the tissue and promoting healing after a stone removal procedure. It effectively stabilizes the urinary tract until the stone is cleared and the ureter has recovered its normal function.
Placement and Removal Procedures
The process of placing a ureteral stent is performed endoscopically using cystoscopy. The patient is usually under general anesthesia or deep sedation. The urologist inserts a cystoscope, a small, flexible telescope, through the urethra and into the bladder.
Once the bladder is visualized, a guidewire is threaded through the cystoscope and up the ureter, past the kidney stone, and into the renal pelvis. The stent is then advanced over this guidewire into its final position. To confirm the correct placement of the double-J curls, the urologist uses real-time X-ray guidance, known as fluoroscopy.
Stent removal is also a minimally invasive procedure, though the method depends on the stent’s design. If the stent was placed with a retrieval string attached to the bladder end and exiting the urethra, removal is a simple, quick office procedure. The provider gently pulls the string, and the stent slides out.
If no string was left, removal requires another short cystoscopy, often performed in the clinic with local anesthetic gel. The urologist inserts the cystoscope to visualize the curl in the bladder and uses a small grasping instrument to secure and pull the stent out through the urethra.
Patient Experience While Stented
While a stent resolves the issue of obstruction, its presence often introduces bothersome symptoms known as stent-related discomfort. One common complaint is bladder irritation, which manifests as urinary frequency and urgency, similar to a urinary tract infection. This is due to the lower coil of the stent irritating the sensitive lining of the bladder as it fills and empties.
Many patients also experience hematuria, or blood in the urine, which appears as a pink or reddish tint. This happens because the stent constantly rubs against the inner wall of the ureter and bladder, causing minor irritation and bleeding. Strenuous physical activity or exertion can temporarily increase this visibility of blood.
Another characteristic symptom is flank pain, often called “stent pain” or reflux. This pain is typically felt in the side or lower back and is most noticeable during or immediately after urination. When the bladder contracts, urine can be forced back up the stent and into the kidney, causing a transient increase in pressure that results in cramp-like discomfort. Stenting is usually a temporary measure, remaining in place for a few days to several weeks, depending on the treatment plan.