Hydronephrosis

Snapshot

• A 48-year-old woman presents to the emergency department due to severe back pain. Her symptoms began approximately 3 hours ago and says the pain is in her left mid-back. She describes the pain as sharp and 9/10. The pain radiates to her left groin. On physical exam, there is left-sided costovertebral angle tenderness. A non-contrast computerized tomography (CT) scan of the abdomen demonstrates left-sided urolithiasis and hydronephrosis. She is started on a nonsteroidal antiinflammatory drug (NSAID) and intravenous normal saline. (Nephrolithiasis resulting in hydronephrosis)

Introduction

• Clinical definition
  • renal calyx and pelvis distension secondary to an obstruction in urine flow distal to the renal pelvis
    • dilation of the ureter describes hydroureter
• Epidemiology
  • demographics
    • age
      • calculi is the most common cause of hydronephrosis and hydroureter in young adults
    • sex
      • pregnancy and gynecologic causes are more common causes in women
      • prostatic hyperplasia and cancer are a major cause of hydronephrosis in men
• Etiology
  • pregnancy
    • normal finding
    • there may be a more prominent dilation on the right ureter and renal pelvis than the left
  • benign prostatic hyperplasia 
  • calculi
  • ureteral narrowing secondary to surgery 
  • malignancy
    • e.g., ureteral, cervical, and prostate
    • e.g., transitional cell carcinoma of the bladder can cause uni- or bi-lateral ureteral obstruction
  • congenital defects between the kidney, ureter, and bladder junction
  • ureteropelvic junction obstruction
  • retroperitoneal fibrosis
• Pathogenesis
  • pathologic or anatomic processes interupt urine flow which leads to
    • an increase in the hydrostatic pressure in Bowman’s space 
      
    • a decline in glomerular filtration rate 
    • impaired ability to concentrate, dilute, and transport sodium, potassium, and hydrogen ions
  • chronic hydronephrosis results in gross changes to the kidney such as
    • renal papillae compression
    • renal septa and calyx coalescence
    • peri-calyx renal parenchymal thinning
• Prognosis
• variable as it is dependent on the underlying cause

Presentation

• Symptoms
  • depends on whether the obstruction is acute or chronic
    • asymptomatic
    • pain secondary to bladder, collecting system, or renal capsule distention
    • anuria
• Physical exam
  • palpable kidney in severe cases
  • costovertebral angle tenderness
• distended bladder in lower urinary tract obstruction (e.g., benign prostatic hyperplasia)

Imaging

• Renal ultrasonography
  • indication
    • imaging test of choice for evaluating urinary tract obstruction
• Computerized tomography (CT) scan of the abdomen
  • indication
• used when results are equivocal on renal ultrasound

Studies

• Labs
  • urinalysis
    • to evaluate for infection, stone, or tumor
  • serum chemistry
    • ↑ BUN and creatinine
• In cases of unilateral ureteral obstruction, the contralateral kidney usually compensates to maintain a normal GFR and serum creatinine; if the contralateral kidney is diseased or if the obstruction is bilateral, then GFR decreases and serum creatinine rises 

Differential

• Pyelonephritis
• Peripelvic cyst
• Calyceal diverticula

Treatment

• Conservative 
  • bladder catheterization
    • indication
      • performed initially if the clinical presentation is suggestive of a bladder neck obstruction such as
        • suprapubic pain
        • palpable bladder
• Treatment ultimately depends on the underlying cause of hydronephrosis
• e.g., oral alkalinization therapy for patients with uric acid stones

Complications

• Postobstructive diuresis