Obstruction of the Urinary Tract

An obstruction of the urinary tract disrupts the flow of urine through it. Obstruction can occur anywhere along the urinary tract, from  the kidney to the urethral meatus. There are many different potential causes. The obstruction may be acute or chronic. The severity of the obstruction varies, from a partial obstruction to a complete obstruction.

Causes
The causes of urinary obstruction are generally categorised according to their location: 

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Obstruction in the ureter

  • kidney stone – a stone formed in the kidney can travel down and obstruct the ureter
  • tumor – a tumor can compress the ureter
  • pregnancy – the gravid uterus can compress on the ureters

Obstruction in the bladder  

  • bladder stone  – a stone formed in the bladder can obstruct the bladder neck
  • bladder cancer – tumor can obstruct the bladder neck
  • neurogenic bladder – dysfunction of the bladder due to damage of the nervous system, such as cerebrovascular accident, brain tumor, spinal cord injury, tumor causing spinal cord compression. Damage to the nervous system may occur because of neurologic diseases, such as multiple sclerosis or Parkinson’s disease. Certain medication can also cause bladder dysfunction, such as anticholinergic medications.

Obstruction in the urethra

  • benign prostatic hyperplasia – an enlarged prostate can compress the urethra
  • stricture – injury to the ureter can cause scarring to develop. Scarring can lead to narrowing of the ureter. The most common cause of urethral stricture is traumatic placement of a urethral urinary catheter

Signs and Symptoms
Signs and symptoms vary, depending on the specific cause, the location of obstruction, the speed of onset (acute or chronic) and the severity (partial or complete obstruction).

Depending on the location and severity of the obstruction, there may or may not be urinary retention and bladder distention.

Complications
Obstruction to the flow of urine causes the urine to accumulate in the urinary tract. In severe cases, the urine can backup and fill the ureters, and eventually fill the kidney. If the kidney is full with urine, it will be swollen. It is a condition called hydronephrosis. If both kidneys are swollen, due to the backup of urine, it is called bilateral hydronephrosis. If a single kidney is swollen, due to the backup of urine, it is called unilateral hydronephrosis. Irreversible loss of function can occur in the affected kidney. 

Another potential complication of urinary tract obstruction is urinary tract infection. This is because the urine that accumulates is static in the urinary tract. Static urine predisposes infection, which can then develop into pyelonephritis or even urosepsis.

Investigations
The investigations required depend on the suspected cause. Investigations may include various physical examinations, such as palpating the bladder or prostate examination. Laboratory studies include analysis of the urine and blood tests. Imaging studies may include ultrasound and abdominal x-ray.

Treatment
Treatment depends on the specific cause, but generally aims to restore the flow of urine.