The ureters are narrow, muscular tubes that connect the kidneys to the bladder, contracting in waves to push urine downward. A ureteral blockage, or ureteral obstruction, is a physical interruption in this pathway that stops the flow of urine from the kidney into the bladder. This interruption can occur at any point along the length of the ureter, ranging from a partial restriction to a complete stoppage. When the flow is blocked, the urine backs up toward the kidney. If not resolved, this condition can lead to serious complications and compromise the long-term health of the affected kidney.
Identifying the Cause of Obstruction
The most frequent reason for a ureteral blockage is the passage of a kidney stone. These hard deposits, formed from crystallized minerals and salts, can dislodge and travel down the narrow ureter, becoming lodged at a constricting point.
Other internal factors, or intrinsic obstructions, include scar tissue called strictures, which narrows the ureteral channel. These strictures can arise following previous infections, surgical procedures, or injury to the urinary tract.
Obstructions can also originate from outside the ureter, classified as extrinsic causes, where surrounding tissues compress the tube. Tumors or cysts developing in organs near the urinary tract, such as the prostate, colon, or uterus, can press against the ureter and restrict the flow of urine. In men, an enlarged prostate gland (benign prostatic hyperplasia) can cause compression near the bottom of the urinary tract, leading to a backup that affects the ureters.
The Immediate Physiological Consequences
When the flow of urine is halted by an obstruction, the immediate result is a backup of fluid and an increase in pressure within the urinary collecting system. The urine accumulates in the renal pelvis and the calyces, causing the structures to swell, a condition termed hydronephrosis.
The rising hydrostatic pressure inside the kidney directly works against the organ’s ability to filter blood and produce urine. This mechanism leads to a rapid decline in the glomerular filtration rate (GFR), which is a measure of kidney function.
If the blockage is not quickly relieved, this sustained high pressure causes the kidney tissue to stretch and become damaged. Over time, prolonged hydronephrosis can lead to irreversible scar tissue, a process known as obstructive nephropathy. The extent of permanent functional loss is directly linked to the duration and severity of the obstruction, potentially leading to acute kidney injury or chronic kidney disease if left untreated.
Recognizable Symptoms of Blockage
A ureteral blockage often presents with severe, spasmodic pain known as renal colic. This pain results from the ureter’s muscular walls contracting intensely in an attempt to push the obstruction downward. The sensation typically begins in the flank area, located between the ribs and the hip, and radiates down to the groin or inner thigh.
The intense pain often comes in waves, corresponding to the peristaltic spasms of the ureter, though it can also be constant. Secondary symptoms commonly include nausea and vomiting, related to the shared nerve pathways between the kidneys and the digestive tract. Many individuals also notice hematuria (blood in the urine), which may be visible or only detectable upon laboratory testing.
A more serious warning sign requiring immediate medical attention is the onset of fever and chills alongside the pain. These symptoms indicate a urinary tract infection (UTI) has developed behind the blockage, trapping infected urine within the kidney. This condition, known as pyelonephritis, can quickly progress to a life-threatening systemic infection or sepsis.
Resolving the Blockage and Recovery
Diagnosing a ureteral obstruction begins with a physical examination and laboratory tests, including a urinalysis to check for blood or signs of infection, and blood tests to assess kidney function by measuring creatinine levels. Imaging studies are essential for confirming the presence and location of the blockage, with a computerized tomography (CT) scan being the most common and detailed method. An ultrasound may also be used to quickly visualize the degree of hydronephrosis in the kidney.
The primary goal of treatment is to quickly restore the flow of urine to prevent permanent kidney damage. For obstructions caused by small ureteral stones, medical management may be used to facilitate their natural passage, often with pain medication and specific drugs that relax the ureteral muscle. Larger or more complex blockages require procedural intervention to either remove or bypass the obstruction.
Procedural interventions include:
- Temporary placement of a ureteral stent, a hollow tube inserted into the ureter to hold it open and allow urine to drain from the kidney into the bladder.
- Lithotripsy, which uses focused shock waves to break the stone into smaller fragments that can be passed more easily.
- Percutaneous nephrostomy, where a tube is inserted through the skin directly into the kidney to drain the urine externally (used in cases of severe infection or when a stent cannot be placed).
Following the successful removal of the blockage and drainage of the kidney, recovery focuses on monitoring kidney function to ensure it returns to or stabilizes at its best possible level.