What Is Hydronephrosis? Causes, Symptoms, and Treatment Options Explained
Hydronephrosis refers to the swelling of a kidney caused by a buildup of urine due to an obstruction in the urinary tract. When the normal flow of urine is disrupted—whether partially or completely—the renal collecting system expands, leading to fluid accumulation within the kidney. This condition can affect one or both kidneys and varies in severity depending on the underlying cause and duration of the blockage.
Common Causes of Kidney Hydration
Several medical conditions can interfere with urine drainage and result in hydronephrosis. The most frequent contributors include urinary tract obstructions, kidney stones, ureteral strictures, bladder outlet blockages, and vesicoureteral reflux (a condition where urine flows backward from the bladder to the kidneys).
1. Urinary Tract Stones
One of the leading causes of unilateral hydronephrosis is the presence of kidney stones. When a stone moves from the kidney into the ureter, it can create a partial or complete blockage. This often results in sudden, severe flank pain—typically on one side—and may be accompanied by nausea, vomiting, or blood in the urine (hematuria). The obstruction prevents urine from draining properly, causing pressure to build up in the kidney and leading to visible swelling on imaging tests like ultrasound or CT scans.
Diagnosis usually involves imaging techniques such as ultrasound or non-contrast CT to pinpoint the size and location of the stone. Treatment options depend on the stone's characteristics and may include extracorporeal shock wave lithotripsy (ESWL), ureteroscopy with laser lithotripsy, or, in some cases, surgical removal.
2. Ureteral Strictures (Narrowing)
Ureteral strictures occur when the ureter—the tube that carries urine from the kidney to the bladder—becomes narrowed, restricting urine flow. These strictures can be congenital or acquired. A common congenital issue is ureteropelvic junction (UPJ) obstruction, where the connection between the renal pelvis and ureter is underdeveloped, leading to chronic kidney swelling and impaired kidney function over time.
Acquired strictures are often linked to previous surgeries, infections, inflammation, or radiation therapy. Over time, scar tissue forms and narrows the ureter, resulting in gradual urine backup and hydronephrosis.
3. Post-Surgical Inflammation and Scarring
Inflammation following pelvic or abdominal surgery can lead to temporary or permanent damage to the ureters. Scar tissue formation may compress or constrict the ureter, disrupting normal urinary flow. In such cases, interventional procedures like ureteral stent placement can help maintain patency and allow urine to drain effectively while healing occurs.
For more severe or persistent strictures, reconstructive surgery such as ureteroplasty or end-to-end ureteral reanastomosis might be necessary to restore proper anatomy and function.
Diagnosis and Medical Evaluation
Early detection of hydronephrosis is crucial to prevent long-term kidney damage. Common diagnostic tools include renal ultrasound, CT urography, MRI, and nuclear medicine scans like a MAG3 renogram, which assess kidney function and drainage efficiency.
Symptoms may vary widely—from being completely asymptomatic in mild cases to presenting with intense back or abdominal pain, urinary frequency, fever (if infection is present), or even signs of kidney failure in advanced stages.
Treatment Approaches and Long-Term Outlook
The primary goal of treatment is to relieve the obstruction and preserve kidney function. Immediate interventions may involve placing a stent or a nephrostomy tube to drain urine externally. Once stabilized, definitive treatment targets the root cause—whether removing stones, correcting anatomical abnormalities, or managing reflux through medication or surgery.
With timely diagnosis and appropriate care, many patients recover full kidney function. However, prolonged untreated hydronephrosis can lead to irreversible renal damage, emphasizing the importance of prompt medical attention.
If you experience persistent flank pain, changes in urination, or unexplained fever, consult a healthcare provider for a thorough evaluation. Early action can protect your kidneys and improve long-term health outcomes.