Hydronephrosis describes swelling of one or both kidneys that occurs when urine cannot drain normally and backs up into the kidney's collecting system. It is not a disease in itself but rather a finding — usually seen on imaging — that signals something downstream is blocking or slowing the normal flow of urine. Because hydronephrosis can range from mild and incidental to severe and threatening to kidney function, understanding its common causes and the drainage options available helps explain why physicians approach each case differently.
What Actually Happens Inside the Kidney During Hydronephrosis?
Under normal circumstances, urine produced in the kidney flows through the renal pelvis, down the ureter, into the bladder, and out through the urethra. When something obstructs this pathway — partially or completely — urine accumulates behind the blockage, and pressure builds within the renal pelvis and calyces, causing them to dilate. This dilation is what appears as kidney swelling on ultrasound, CT, or MRI imaging. Mild hydronephrosis may cause no symptoms at all, while more significant obstruction can produce flank pain, changes in urination, or signs of infection. The degree of swelling and how quickly it developed both factor into how urgently it needs to be addressed.
What Are Common Causes of Obstruction Behind Hydronephrosis?
Hydronephrosis has many potential causes, and identifying the specific one is central to treatment planning. Commonly reported causes include kidney stones lodged in the ureter, strictures or narrowing from prior surgery or scarring, tumors pressing on or growing within the urinary tract, and congenital conditions affecting the junction where the kidney meets the ureter. In some cases, hydronephrosis is temporary and resolves once the underlying obstruction — such as a passing stone — clears on its own. In others, the cause is more persistent and requires ongoing management or intervention to protect kidney function over time.
Why Does the Cause of Obstruction Matter So Much for Management?
Because hydronephrosis is a symptom of an underlying blockage rather than a standalone condition, treatment is generally directed at the cause once it is identified through imaging and clinical evaluation. A stone causing obstruction may be managed differently than a stricture or a mass, and the urgency of treatment often depends on how much the swelling is affecting kidney function, whether infection is present, and whether the obstruction is partial or complete. A qualified physician determines the appropriate diagnostic workup and treatment sequence based on these individual findings rather than a generic protocol.
What Drainage Options Are Considered for Significant Hydronephrosis?
When hydronephrosis is significant enough to threaten kidney function or is associated with infection, temporary urinary drainage is often used to relieve pressure while the underlying cause is addressed or further evaluated. Two commonly used approaches are internal drainage with a ureteral stent, which is placed endoscopically to bridge the obstructed segment of the ureter, and external drainage with a percutaneous nephrostomy catheter, which is placed directly into the kidney's collecting system through the skin under imaging guidance. The choice between these two general approaches depends on factors such as the location and cause of the obstruction, whether infection is present, and overall patient anatomy — a decision a treating urologist makes on a case-by-case basis.
How INVAMED Devices Support Drainage in Obstructive Cases
Percutaneous nephrostomy — the image-guided placement of a drainage catheter directly into the renal collecting system — is one of the established methods for relieving obstructive hydronephrosis when internal drainage is not suitable or not yet possible. The Bionovus Nephrectomy Percutaneous Nephrostomy Catheter (Pigtail) is designed for temporary external drainage of upper ureteral and renal obstructions, using a soft, biocompatible polyurethane construction that the manufacturer describes as highly radiopaque to support visualization during and after placement. It is part of INVAMED's broader urology and incontinence management product line.
Is hydronephrosis always caused by a kidney stone?
No. While kidney stones are a commonly reported cause of hydronephrosis, other causes include strictures, tumors, and congenital abnormalities of the urinary tract. Identifying the specific cause typically requires imaging and clinical evaluation by a physician.
Can mild hydronephrosis go away without treatment?
Mild hydronephrosis, particularly when caused by a temporary obstruction such as a small passing stone, may resolve once the blockage clears. Persistent or worsening hydronephrosis generally warrants further evaluation to identify and address the underlying cause.
What symptoms of hydronephrosis require immediate medical attention?
Symptoms such as fever, severe flank pain, or signs of significant urinary obstruction are generally considered indications to seek immediate medical care. These findings can suggest infection behind an obstruction or worsening kidney compromise that may need urgent drainage.
Device availability and regulatory status vary by country. Please contact INVAMED or your authorized local distributor for current regulatory information applicable to your region.