Obstructive Uropathy Flashcards
What is it?
The term obstructive uropathy refers to a blockage preventing urine flow through the ureters, bladder and urethra.
Obstruction leads to back-pressure in the urinary system, causing areas proximal to the site of obstruction to become swollen with urine. For example, obstruction at the opening of the ureters in the bladder, from a bladder tumour, will result in swelling of the ureter and kidney on that side. Swelling of the kidney is known as hydronephrosis. Vesicoureteral reflux (VUR) refers to urine refluxing from the bladder back into the ureters.
When obstructive uropathy leads to an acute reduction in kidney function, it is referred to as a “post-renal” acute kidney injury (AKI). This is different from “pre-renal” AKI, which is caused by hypoperfusion of the kidneys (e.g., due to dehydration, sepsis or acute blood loss), and “renal” AKI, which refers to damage within the kidney itself (e.g., due to glomerulonephritis or nephrotoxic medications).
Presentation
An upper urinary tract obstruction (i.e. in the ureters) presents with:
Loin to groin or flank pain on the affected side (due to stretching and irritation of ureter and kidney)
Reduced or no urine output
Non-specific systemic symptoms, such as vomiting
Impaired renal function on blood tests (i.e. raised creatinine)
Lower urinary tract obstruction (i.e. in the bladder or urethra) presents with:
Difficulty or inability to pass urine (e.g., poor flow, difficulty initiating urination or terminal dribbling)
Urinary retention, with an increasingly full bladder
Impaired renal function on blood tests (i.e. raised creatinine)
An ultrasound of the kidneys, ureters and bladder can be helpful in diagnosing obstructive uropathy.
Common Causes
Upper urinary tract obstruction:
Kidney stones
Tumours pressing on the ureters
Ureter strictures (due to scar tissue narrowing the tube)
Retroperitoneal fibrosis (the development of scar tissue in the retroperitoneal space)
Bladder cancer (blocking the ureteral openings to the bladder)
Ureterocele (ballooning of the most distal portion of the ureter – this is usually congenital)
Lower urinary tract obstruction:
Benign prostatic hyperplasia (benign enlarged prostate)
Prostate cancer
Bladder cancer (blocking the neck of the bladder)
Urethral strictures (due to scar tissue)
Neurogenic bladder
Neurogenic Bladder?
Neurogenic bladder refers to abnormal function of the nerves innervating the bladder and urethra. It can result in overactivity or underactivity in the detrusor muscle of the bladder and the sphincter muscles of the urethra.
Key causes are:
Multiple sclerosis
Diabetes
Stroke
Parkinson’s disease
Brain or spinal cord injury
Spina bifida
Neurogenic bladder can result in a variety of problems, including:
Urge incontinence
Increased bladder pressure
Obstructive uropathy
Management
Management involves removing or bypassing the obstruction.
A nephrostomy may be used to bypass an obstruction in the upper urinary tract (e.g., a ureteral stone). A nephrostomy involves surgically inserting a thin tube through the skin at the back, through the kidney and into the ureter. This tube allows urine to drain out of the body, into a bag.
A urethral or suprapubic catheter may be used to bypass an obstruction in the lower urinary tract (e.g., a urethral stricture or prostatic hyperplasia). A urethral catheter is a tube, inserted through the urethra, into the bladder. A suprapubic catheter is a tube, inserted through the skin just above the pubic bone, directly into the bladder.
Complications of Obstructive Uropathy
Pain
Acute kidney injury (post-renal)
Chronic kidney disease
Infection (from bacteria tracking up urinary tract into areas of stagnated urine)
Hydronephrosis (swelling of the renal pelvis and calyces in the kidney)
Urinary retention and bladder distention
Overflow incontinence of urine
Hydronephrosis ?
Hydronephrosis is swelling of the renal pelvis and calyces in the kidney. This occurs due to obstruction of the urinary tract, leading to back-pressure into the kidneys.
Idiopathic hydronephrosis is the result of a narrowing at the pelviureteric junction (PUJ) – the site where the renal pelvis becomes the ureter. This narrowing may be congenital or develop later. It can be treated with an operation to correct the narrowing and restructure the renal pelvis (pyeloplasty).
Typical presenting features of hydronephrosis are vague renal angle pain and a mass in the kidney area. It may be seen on an ultrasound, CT scan or intravenous urogram (x-ray with IV contrast collecting in the urinary tract).
Treatment of hydronephrosis involves treating the underlying cause. If required, pressure can be relieved with either:
Percutaneous nephrostomy – inserting a tube through the skin and kidney into the ureter, under radiological guidance
Antegrade ureteric stent – inserting a stent through the kidney into the ureter, under radiological guidance
