What is hydronephrosis bilateral and how is it treated?

Bilateral Hydronephrosis: Definition and Treatment

Bilateral hydronephrosis is urine-filled dilation of both kidneys' collecting systems (renal pelvis and calyces) that requires urgent evaluation and intervention regardless of normal laboratory values, because both kidneys are simultaneously at risk without contralateral functional reserve, and progressive obstruction causes irreversible nephron loss even when initially asymptomatic. 1, 2

What Bilateral Hydronephrosis Means

Bilateral hydronephrosis represents a critical urologic emergency because it eliminates the safety net of contralateral kidney compensation that exists in unilateral disease. 1, 2 This means:

• Serum creatinine can remain deceptively normal initially because both kidneys deteriorate together, but this does not exclude significant obstruction. 1
• Upper urinary tract deterioration is often clinically silent and detected incidentally with nonspecific symptoms. 3, 1
• Progressive dilation leads to acute kidney injury and permanent nephron loss if not corrected promptly. 3

Common Causes

The differential diagnosis includes lower urinary tract obstruction and bilateral upper tract processes: 3

• Bladder outlet obstruction: prostatic hyperplasia, urethral stricture 3, 1
• Pelvic pathology: malignancy, uterine prolapse, pelvic organ prolapse 3, 1
• Retroperitoneal processes: retroperitoneal fibrosis, malignancy 3, 1
• Bladder dysfunction: neurogenic bladder, severe cystitis causing vesicoureteric junction obstruction 3, 1
• Bilateral ureteral obstruction: stones, strictures, extrinsic compression 3

Diagnostic Approach

MAG3 renal scan with diuretic administration represents the de facto standard of care for diagnosing true obstructive uropathy and differentiating functional obstruction from non-obstructive dilation. 1, 2

Imaging Algorithm:

• First-line functional assessment: MAG3 renal scan provides both perfusion and excretion phase information to determine if true functional obstruction exists. 1, 2
• Anatomic evaluation: CT urography without and with IV contrast provides morphological and functional information to identify the underlying etiology, including nephrographic and excretory phases acquired at least 5 minutes after contrast injection. 3, 1
• If renal impairment develops: MR urography with IV contrast is preferred as it avoids nephrotoxic contrast while providing comprehensive genitourinary tract evaluation. 1, 2

Treatment Strategy

Immediate percutaneous nephrostomy (PCN) or retrograde ureteral stenting is indicated when bilateral hydronephrosis presents with infection/sepsis, acute kidney injury, or significant pain. 2

Treatment Algorithm Based on Presentation:

For bladder outlet obstruction:

• Immediate bladder catheterization for decompression 2
• Followed by definitive surgical correction of the underlying cause (transurethral resection of prostate, urethral dilation, etc.) 2

For confirmed obstructive uropathy on MAG3 scan:

• Surgical pyeloplasty is indicated when T1/2 >20 minutes, differential renal function <40%, deteriorating function (>5% change on consecutive scans), or worsening drainage on serial imaging 2

For bilateral ureteral obstruction:

• Bilateral ureteral stent placement or percutaneous nephrostomy tubes 2
• Address underlying cause (stone removal, stricture repair, treatment of malignancy) 2

Critical Pitfalls to Avoid

• Do not assume normal renal function excludes significant obstruction - bilateral disease can present with preserved creatinine until late stages. 1, 2
• Do not assume negative urinalysis excludes obstruction - infection is a complication of obstruction, not a prerequisite for its presence. 1
• Do not delay imaging based on "minimal" grading - ultrasound grading of hydronephrosis severity does not reliably predict functional significance or reversibility. 1
• Do not perform bilateral robot-assisted laparoscopic ureteral reimplantation simultaneously due to risk of transient urinary retention. 2

Follow-Up Management

After initial decompression and definitive treatment: 2

• Regular monitoring of renal function with serial creatinine and estimated GFR 2
• Ultrasound monitoring at least once every 2 years in patients with chronic or persistent hydronephrosis to assess for progression 2
• Repeat MAG3 renal scan to monitor differential function over time, with >5% decrease serving as an indicator for intervention 2
• Prophylactic antibiotics should be considered in patients with severe hydronephrosis to prevent urinary tract infections 2