Urinary Tract Obstruction

Impaired urinary flow due to physical obstruction may occur at any point in urinary tract from renal calyces to external urethral meatus. It causes proximal distention of the urinary tract associated with pain and decreased renal function, and urinary stasis carries the attendant risk of UTI and sepsis.
Certain points along the urinary tract are more susceptible to obstruction:

• Pelvi-ureteric junction (PUJ)
• Where the ureters cross the pelvic brim, at the level of the iliac vessels
• Vesico-ureteric junction (VUJ)

Obstruction can be unilateral or bilateral:

• Unilateral - commonest causes are calculi and neuromuscular malfunction at the junction of the renal pelvis and ureter.
• Bilateral - in developed world, 75% due to prostate, calculi and bladder tumours.

Age

Occurs most commonly in young and the old:

• In older men, it is a relatively common condition due to prostatic enlargement. In a general postmortem study from 0-80 years, the incidence of hydronephrosis (indicating chronic obstruction and back pressure) was 3.1%.¹ Incidence of lower urinary tract symptoms/benign prostatic hyperplasia (BPH) in men averages 15 per 1,000 man-years. In the age range 45-49, it is 3 per 1,000 man-years, increasing to 38 per 1,000 man-years by age 75-79.² Acute urinary retention (AUR) is a rather uncommon sequelae with a cumulative incidence of 2% over almost 5 years in men with symptomatic BPH.³
• In children, hydronephrosis due to a congenital abnormality is relatively common. Prenatally, 1 in 100 fetuses are found to have hydronephrosis on ultrasound, most resolve. It is more common in boys. An analysis of children presenting incidentally after renal tract trauma found an incidence of congenital renal tract abnormalities of 8.3%, most commonly PUJ obstruction.⁴

Sex

In men, urinary tract obstruction is most commonly a consequence of BPH or urethral stricture whilst in women, it tends to be related to pelvic tumours (particularly gynaecological malignancies), prolapse of pelvic structures or pregnancy.

Acute upper tract obstruction

• Flank pain:
  • Dull, sharp or colicky; intermittent or persistent but usually of varying intensity.
  • Often radiates to iliac fossa, inguinal area, testis or labium.
  • May be provoked by alcohol, diuretics or high fluid intake.
• On palpation, loin tenderness, occasionally enlarged kidney. Clinical presentation may be dominated by symptoms of UTI and signs of septicaemia.
• Complete anuria suggests bilateral or unilateral complete obstruction.

Chronic upper tract obstruction

• Presents with flank or abdominal pain and/or renal failure.
• Polyuria may be a feature.

Acute lower tract obstruction

• Often follows history of symptoms of obstruction of bladder outflow.
• Usually severe suprapubic pain (but not if superimposed on chronic retention or underlying neuropathy).

Chronic lower tract obstruction

• Usual signs and symptoms include:
  • Urinary hesitancy
  • Narrow and weak urine stream
  • Dribbling at end of micturition
  • Feeling of incompletely emptied bladder.
• With large volume of residual urine in bladder, may present with frequent passage of small volumes possibly with incontinence.
• May be complicated by acute retention associated with UTI.

Idiopathic retroperitoneal fibrosis

• Presents with girdle like distribution of pain from low back to lower abdomen.
• 50% have hypertension.
• Anaemia, raised ESR and C-reactive protein are typical findings.

• Check U&Es:
  • After relieving chronic obstruction there may be sodium and potassium loss, so Na⁺ and K⁺ levels should be checked subsequently.
  • Involve a general/renal physician early on in management if there is evidence of renal impairment.
  • Note, normal creatinine and urea do not exclude early mild to moderate renal impairment.
  • Consider checking creatinine clearance by 24-hour urine collection after acute phase.
• FBC - looking for anaemia of renal failure and evidence of infection.
• Urine microscopy and culture in chronic obstruction and after relieving acute obstruction.
• Blood cultures if septic symptoms/signs.
• Ultrasound is the first line choice for imaging in suspected chronic upper tract obstruction.
• IV urography or unenhanced spiral CT, renal scintigraphy, antegrade pyelography and ureterography (contrast agent injected directly into renal pelvis or calyx) by retrograde ureterography are used to investigate suspected acute upper tract obstruction.
• Ultrasound of distended bladder or a transrectal ultrasound of prostate are used to investigate acute lower tract obstruction. Ascending urethrogram is an option where urethral catheterisation has been unsuccessful following suprapubic catheterisation.
• Ultrasound with plain abdominal X-ray and measure of urinary flow rates is used to investigate chronic lower tract obstruction.
• Suspected prostatic enlargement - serum PSA, ultrasound, biopsy as appropriate.
• Children with recurrent UTI or possible obstruction should be assessed rapidly to prevent obstructive renal failure.⁵

• Urethral or suprapubic catheterisation
• Stenting the ureter
• Nephrostomy

Acute upper tract obstruction^6,7

• With renal and ureteric colic, most patients with a stone <5mm diameter, in the lower third of ureter can be managed conservatively:
  • Acute symptoms rarely last more than 72 hours.
  • Give pain relief with NSAIDs (usually im diclofenac 75 mg, repeated after 30 minutes if no response or alternatively diclofenac suppositories 100 mg pr) or morphine (where NSAID contraindicated).
  • Discourage use of anticholinergics and high fluid intake.
• With larger stones or those in the upper ureter consider lithotripsy. In persistent colic, consider endoscopic investigation.
• If clinical evidence of infection above with obstruction, need to establish drainage as soon as possible. Normally, use percutaneous insertion of needle above obstruction to provide nephrostomy. This can be left in place for weeks or even months. A retrograde ureteric catheter will provide drainage for only a few days.
• With other causes eg sloughed papillae and blood clots or tumours, need to treat underlying cause as well as relieve obstruction as above.

Chronic upper tract obstruction

It is now usually possible to avoid open surgery for renal stones:

• Extracorporeal shockwave lithotripsy can shatter the stone within the kidney and the fragments pass spontaneously in many cases.
• Alternatively, create a nephrostomy to the calculus and then either remove it endoscopically or disintegrate it with an ultrasound probe.

PUJ obstruction

Options for treatment include:

• Endopyelotomy (percutaneous procedure with full thickness incision through the stenosis leaving stent in situ) although multiple minimally invasive procedures are evolving.⁸
• Open pyeloplasty in primary idiopathic obstruction.
• Ureteroscopic endoureterotomy is used to treat ureteric strictures.⁹

Malignant obstruction

In addition to treatment of underlying condition, ureteric stenting or percutaneous nephrostomy is required to relieve the obstruction.

Idiopathic retroperitoneal fibrosis¹⁰

• Ureterolysis or stent placement is undertaken to relieve obstruction.
• Any provoking medication should be stopped and adjunctive corticosteroids or immunosuppressive medication (eg azathioprine, tamoxifen) considered.
• Biopsy (US-guided or via laparotomy) of peri-aortic mass to exclude malignancy.

Benign prostatic hyperplasia¹¹

Acute retention requires urinary catheterisation.
With mild symptoms (little impact on quality of life and no evidence of complications), watchful waiting is justified. Advice to reduce fluid intake, avoid caffeine and alcoholic drinks may be appropriate.

Medical treatment¹²

• Alpha-blockers - rapid therapeutic onset with about 70% men responding. They do not alter disease progression. Side effects include postural hypotension, headaches, sleepiness, dizziness, abnormal ejaculation. Tamsulosin and once daily extended release alfuzosin have the lowest risk of cardiac side-effects and are, therefore, suitable for first line agents in high risk or elderly patients.
• 5-alpha reductase inhibitors - slow disease progression and the development of acute urinary retention as they 'shrink' the prostate. Note, no symptom improvement may occur for the first six months of treatment. Side-effects include erectile dysfunction, reduced libido, ejaculatory disorders and gynaecomastia. They are particularly beneficial for patients with risk factors for disease progression (eg high prostate volume, PSA>1.4 μg/l and prostate cancer excluded, high post void volume).
• Combination therapies - combination of finasteride and doxazosin reduces the risk of progression to acute urinary retention or need for surgery but had more side-effects than using finasteride alone (doxazosin not effective alone).¹³

Alternative treatments

Several plant extracts have been reported to improve lower urinary tract symptoms - most widely-known is saw palmetto (from the berry of the american dwarf palm tree). Some studies have suggested efficacy equivalent to that of finasteride but they are often of poor quality, not long-term and concerns over side-effects and interactions exist.^14,15 WHO urological disease consensus group does not recommend treatment with these extracts until more substantial evidence exists.¹⁶

Surgical treatments

Surgery is less frequent now given more effective medical treatment, and increasingly offers less invasive options compared to the standard transurethral resection of the prostate (TURP).¹⁷ These include:

• Transurethral incision of the prostate
• Transurethral microwave thermotherapy - uses heat generated by a microwave antenna passed through the urethra to coagulate prostate tissue. It can be performed in an outpatient setting.
• Various laser procedures - interstitial laser coagulation, transurethral laser ablation, laser prostatectomies (resection and enucleation), high-power potassium titanyl phosphate laser vaporization.
• Transurethral needle ablation (TUNA) uses heat generated by radio frequency energy from two intraprostatic needles to coagulate the prostate tissue. Some practitioners advocate TUNA as a first line therapy for BPH, suggesting it compares favorably to medical treatment in terms of outcome and cost¹⁸ but others point to the high re-treatment rate.¹⁹

Congenital obstructive nephropathy

Since the advent of fetal ultrasound, many cases of hydronephrosis are now found on routine antenatal scanning. About half are due to PUJ obstruction. Depending on the severity of findings, cases are monitored in utero and after birth - some will require corrective surgery but many will resolve spontaneously. Fetal treatments such as fetal cystoscopy²⁰ (allows endoscopic visualisation and obliteration of obstructions such as posterior urethral valves) and vesico-amniotic shunts²¹ (a decompression procedure) remain experimental.²²

Complications of untreated urinary tract obstruction include:

• Infection (cystitis, pyelonephritis, abscess formation and sepsis)
• Urinary extravasation
• Fistula formation
• Renal insufficiency or failure
• Bladder dysfunction
• Pain

Prognosis is dependant on the cause, location, degree, and duration of obstruction. Bad prognostic factors are longer duration and worse severity of obstruction, together with concomitant infection.