What are the causes and treatment options for hydronephrosis?

Causes and Management of Hydronephrosis

Hydronephrosis is the dilation of the renal collecting system, typically resulting from urinary obstruction or reflux, which requires prompt evaluation and treatment to prevent permanent renal damage.1

Etiology

Hydronephrosis can be classified by:

• Cause (obstructive vs. non-obstructive)
• Laterality (unilateral vs. bilateral)
• Level of obstruction (complete vs. partial)
• Nature of obstruction (intrinsic vs. extrinsic)1

Common causes include:

• Urolithiasis (kidney stones) - The most common cause, accounting for 54.1% of cases, with stones most frequently located at the vesicoureteric junction (25.3%) and renal pelvis (21.5%)2
• Malignant obstruction - From tumors of the urinary tract or adjacent structures1
• Strictures - Due to inflammation, trauma, or iatrogenic causes1
• Upper urinary tract infections - Can cause temporary obstruction due to inflammation1
• Retroperitoneal fibrosis - Causing extrinsic compression of the ureters1
• Prostatic hyperplasia - Leading to bladder outlet obstruction1
• Pregnancy - Occurs in 70-90% of pregnant patients due to mechanical compression and hormonal effects1
• Congenital anomalies - Such as ureteropelvic junction obstruction or posterior urethral valves1
• Vesicoureteral reflux - Accounts for 7.3% of cases2
• Mechanical compression - From enlarged uterus, pelvic organ prolapse, or other masses1
• Drug-induced - From medications like cyclophosphamide or ketamine1

Diagnostic Approach

Initial Imaging

For asymptomatic hydronephrosis:

• Ultrasound with Color Doppler - First-line imaging that can identify and grade hydronephrosis, evaluate ureteral jets, bladder distension, and postvoid residual1
• CT Urography (CTU) - Provides comprehensive evaluation of the genitourinary tract with both morphological and functional information1
• MAG3 Renal Scan - The standard for diagnosing true functional obstruction versus non-obstructive dilation1

For symptomatic hydronephrosis:

• CT abdomen and pelvis - Particularly useful for suspected urolithiasis and when moderate to severe hydronephrosis is present1
• Ultrasound with Color Doppler - Highly specific (94.4%) for detecting symptomatic renal stones when moderate or greater hydronephrosis is present1

For pregnant patients:

• Ultrasound with Color Doppler - Preferred initial imaging to avoid radiation exposure1
• MRU without contrast - When more detailed imaging is needed during pregnancy1

Grading of Hydronephrosis

Severity is typically graded on a scale from 1-4:

• Grade 1 (mild): Slight dilation of renal pelvis without calyceal dilation
• Grade 2 (moderate): Dilation of renal pelvis and some calyces
• Grade 3 (severe): Dilation of renal pelvis and all calyces with preserved renal parenchyma
• Grade 4 (extreme): Massive dilation with thinning of renal parenchyma3

Management

Management depends on the cause, severity, and whether the condition is acute or chronic:

Acute Management

• Urinary Drainage - For severe obstruction or infection:

  • Percutaneous nephrostomy tube placement
  • Ureteral stent placement4

• Pain Management - For symptomatic patients:

  • Appropriate analgesics based on pain severity4

• Antibiotics - For associated urinary tract infections or pyonephrosis4

Definitive Treatment

• Urolithiasis:

  • Small stones (<5mm): Conservative management with hydration and pain control
  • Larger stones: Extracorporeal shock wave lithotripsy (ESWL), ureteroscopy with stone extraction, or percutaneous nephrolithotomy2

• Strictures:

  • Endoscopic dilation
  • Surgical reconstruction1

• Malignancy:

  • Treatment of the underlying malignancy
  • Palliative drainage if necessary1

• Benign Prostatic Hyperplasia:

  • Medical therapy (alpha-blockers, 5-alpha-reductase inhibitors)
  • Surgical interventions (TURP, laser procedures)1

• Pregnancy-related hydronephrosis:

  • Usually resolves after delivery
  • Temporary drainage may be needed if symptomatic or complicated1

• Congenital anomalies:

  • Surgical correction of the anatomical abnormality1

Monitoring and Follow-up

• Regular ultrasound monitoring for persistent hydronephrosis
• Renal function tests to assess for kidney damage
• Follow-up imaging based on the underlying cause and response to treatment4

Complications of Untreated Hydronephrosis

• Acute kidney injury - Can develop rapidly with complete obstruction1
• Permanent nephron loss - With prolonged obstruction1
• Urinary tract infections - More common with stasis of urine4
• Pyonephrosis - Infected, obstructed kidney requiring emergency drainage4
• Renal atrophy - End result of chronic, severe obstruction4

Special Considerations

• Silent hydronephrosis (asymptomatic) can lead to progressive renal damage if not addressed5
• Intermittent hydronephrosis presents diagnostic challenges and may require specialized testing like diuretic renography to detect the double-peak pattern indicative of intermittent obstruction6
• Post-procedural hydronephrosis occurs in approximately 8.2% of patients after ureteroscopy, with most cases being transient5