Obstructive Uropathy

Obstructive uropathy is structural or functional blockage of urinary flow resulting in elevated pressure proximal to the obstruction.

Obstruction can be:

Upper tract

• Ureteric stone
• Ureteric stricture
• Pelviureteric junction obstruction
• Retroperitoneal tumour
• Pelvic malignancy

Lower tract

• BPH
• Prostate cancer
• Urethral stricture
• Neurogenic bladder
• Bladder neck obstruction

It can also be:

• Unilateral
• Bilateral
• Acute
• Chronic
• Partial
• Complete

Prolonged obstruction causes tubular dysfunction, reduced renal blood flow, renal fibrosis and potentially irreversible loss of renal function.

Presentation depends on site.

Acute ureteric obstruction:

• Severe flank pain
• Nausea
• Haematuria

Lower tract obstruction:

• Weak stream
• Retention
• Suprapubic distension

Bilateral obstruction can present primarily with:

• Acute kidney injury
• Hyperkalaemia
• Oliguria or anuria
• Pulmonary oedema

Infected obstruction produces:

• Fever
• Rigors
• Sepsis

Infected obstructed upper urinary tract is a drainage emergency.

Check:

• Creatinine
• Potassium
• Bicarbonate
• Urinalysis
• Urine culture

Ultrasound: identifies hydronephrosis and bladder retention.

Noncontrast CT: highly useful for ureteric calculi.

Contrast CT is used when malignancy or another structural cause requires definition.

Absence of hydronephrosis does not completely exclude very early obstruction or obstruction in a severely dehydrated patient.

Urgent drainage is required with:

• Infected obstruction
• Acute kidney injury
• Hyperkalaemia
• Bilateral obstruction
• Solitary kidney obstruction
• Anuria
• Uncontrolled pain despite medical therapy

Lower tract obstruction

Drain the bladder using:

• Urethral catheter

or

• Suprapubic catheter

Upper tract obstruction

Use:

Retrograde ureteric JJ stent

or

Percutaneous nephrostomy

Both can decompress an infected obstructed system.

The immediate objective in urosepsis is drainage, not definitive stone removal.

Do not perform prolonged ureteroscopic stone fragmentation in a septic unstable patient before source control.

After sepsis settles, treat the underlying stone or stricture definitively.

Post obstructive diuresis

Monitor closely after relieving major bilateral or chronic obstruction.

Replace fluid and electrolytes according to losses while preventing hypovolaemia.

Malignant obstruction

Drainage is appropriate when it will:

• Treat sepsis
• Reverse renal failure
• Permit systemic anticancer therapy
• Improve significant symptoms

Do not automatically insert bilateral nephrostomies in terminal malignant obstruction when decompression will not meaningfully alter treatment or quality of life.