Urinary Tract Obstruction Flashcards
Describe the epidemiology of urinary tract obstruction.
Occurs most often in the very young and old.
Young most frequently due to anatomical abnormalities.
Old most likely prostatic enlargement or malignancy within pelvis or Retroperitoneum.
Describe the pathogenesis of urinary tract obstruction.
Obstruction of the urinary tract at any level can result in increased hydrostatic pressure - this is transmitted back to renal tubules.
Increased tubular pressure leads to fall in glomerular filtration rate and, if obstruction is prolonged, a reduction in renal blood flow + loss of nephrons.
What clinical features would you find in in a patient with urinary tract obstruction?
Depend on site, degree and speed of onset of obstruction.
Total Anuria is suggestive of complete bilateral obstruction (or complete obstruction of the single functional kidney).
Normal urine output does not exclude partial obstruction
Polyuria can occur as a result of impaired concentrating ability in renal tubules.
If obstruction develops over a long period of time it can be asymptomatic.
Renal examination in males may reveal an enlarged or abnormal prostrate gland.
What investigations would you request for a patient with suspected urinary tract obstruction?
USS of renal tract can usually identify level of obstruction
Cannot distinguish between an obstructed urinary system and a low-pressure chronically dilated system.
Radionuclide renogram may show delayed drainage of isotope if functional obstruction is present.
How would you manage a patient with a urinary tract obstruction?
Rapid relief of obstruction is important.
—Probability of recovering renal function decreases with time.
Insertion of a urethral or suprapubic catheter may be sufficient in lower urinary tract obstruction.
More proximal obstruction requires external drainage of urine via a nephrostomy.
Relief of obstruction may be followed by a large diuresis resulting in loss of sodium and water, necessitating fluid and electrolyte replacement.
Subsequent management depends on underlying cause
•Surgery often required
•Retroperitoneal fibrosis may respond to medical management alone.
Provide examples of causes for urinary tract obstruction.
Within the lumen: •Blood clot •Sloughed papilla •Rumour of renal pelvis or ureter •Bladder tumour
Within the tract wall: •Pelviuretic neuromuscular dysfunction •Ureteric or urethral stricture •Congenital megaureter •Neuropathic bladder
Pressure from outside: •Prostatic obstruction •Phimosis •Retroperitoneal fibrosis •Aberrant vessels/bands across ureter •Tumours (eg colon or cervical).
