26th June 2023

Urinary Tract Obstruction

Causes of urinary tract obstruction

The most common causes of urinary tract obstruction in young adults are stones in a kidney or ureter (see Renal Calculi section). In older adults, benign prostatic hyperplasia (BPH), prostate cancer, tumours (see Urinary Tract Tumours section) and stones are all common causes.

Other causes of urinary tract obstruction include tumours, abscesses, and cysts of the bladder, cervix, uterus, prostate, or other pelvic organs.

People who have slowly progressive obstruction causing hydronephrosis may have no symptoms, or they may have attacks of dull, aching discomfort in the flank on the affected side. Chronic obstructive nephropathy typically leads to the development of end stage renal disease (ESRD) and can be complicated by chronic UTI.

Benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH) typically presents with a gradual reduction in urinary flow, hesitancy, frequency, and nocturia. It may also present with acute retention of urine. Management depends on the extent to which lower urinary tract symptoms affect quality of life; this is often classified using the International Prostate Symptom Score (IPSS).

Initial management options include lifestyle changes:

• Reducing fizzy drinks and liquid input before bed
• Bladder training
• Double voiding techniques

Medical management constitutes:

• Alpha blockers, e.g. tamsulosin
  • By inhibiting alpha-1 receptors, the smooth muscle of the prostate and the base of the bladder are relaxed, making it easier for urine to flow.
  • Common side effects include orthostatic hypotension, nasal congestion, ejaculation changes, and weakness.
• Anticholinergics, e.g. oxybutynin
  • Specifically relax bladder detrusor muscle and are also used in overactive bladder.

Prostate cancer

(See Urinary Tract Tumours below)

Management of Acute Obstruction

Early diagnosis is important because most cases of obstruction can be corrected and a delay in treatment can lead to irreversible kidney damage. Doctors may suspect obstruction based on a patient’s symptoms, such as renal colic, symptoms of bladder distention, or a decrease in the volume of urine. A distended bladder can sometimes be felt in the lower part of the abdomen just above the pubic bone.

The first step in the management of acute obstruction is with urethral catheterisation.
Urethral catheterisation (insertion of a hollow, soft tube through the urethra) is often the first diagnostic test done in people with symptoms that suggest the bladder is distended, such as pelvic pressure or distention. If the catheter drains a large amount of urine from the bladder, this suggests that either the bladder outlet or the urethra is obstructed.

The next step is to investigate the cause of the obstruction with investigations which may include renal tract ultrasound, CT KUB or micturition studies.

The cause of the obstruction is targeted. If the cause of obstruction cannot be rapidly corrected or relieved by urethral catheterisation, particularly if there is infection, kidney failure, or severe pain, the urinary tract is drained via nephrostomy or suprapubic catheter, depending on the level of obstruction.