6. Urinary tract obstruction

Question 1

Definition of urinary tract obstruction

Answer 1

Obstruction of the urinary tract, leads to hydronephrosis

Question 2

Causes of urinary tract obstruction

Answer 2

1. Congenital anomalies
   - Ureteropelvic junction obstruction or narrowing
   - Bladder neck obstruction
   - Urethral valve or strictures
2. Acquired obstructions
   - Urolithiasis
   - Benign prostatic hyperplasia
   - Tumours (prostate, bladder, cervix, uterus, ureter)
   - Inflammation of prostate, ureter or urethra
   - Slough papillae in papillary necrosis
   - Pregnancy
   - Uterine prolapsed (kinks ureters)
3. Functional obstruction
   - Spinal cord damage
   - Diabetic autonomic neuropathy

Question 3

Anatomical changes due to urinary tract obstruction

Answer 3

1. Hydronephrosis
   - Dilation of renal pelvis & calyces with progressive enlargement of the kidney with parenchymal atrophy due to obstruction of urine outflow
2. Hydroureter
   - Dilated ureter upstream of obstruction
3. Pyonephrosis
   - Infected hydronephrosis with frank pus in the dilated calyces & pelvis

Question 4

Morphology of hydronephrosis

Answer 4

1. [Grossly]
   - Enlarged kidney, dilated pelvis & calyces, atrophy & thinning of renal cortex
2. [Histologically]
   - Dilated tubules & Bowman’s capsules, flattened tubular epithelium; later on, tubular atrophy with interstitial fibrosis & disappearance of glomeruli

Question 5

Pathological Effects & complications of hydronephrosis

Answer 5

1. Unilateral hydronephrosis typically clinically silent
   - Other kidney can compensate
2. Bilateral hydronephrosis
   - Oliguria, anuria
   - After relief of obstruction, post-obstructive diuresis occurs