Urinary Tract Obstruction

Impaired urinary flow due to physical obstruction may occur at any point in the 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 urinary tract infection (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 - the most common causes are calculi and neuromuscular malfunction at the junction of the renal pelvis and ureter.
• Bilateral - in the developed world, 75% are due to prostate, calculi and bladder tumours.

Age

Urinary tract obstruction occurs most commonly in the young and the old:

• In older men, it is a relatively common condition due to prostatic enlargement. 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 75-79.¹ Acute urinary retention (AUR) is a rather uncommon sequelae with a cumulative incidence of 2% over almost 5 years in men with symptomatic BPH.²
• 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, pelvi-ureteric junction (PUJ) obstruction.³

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 the iliac fossa, inguinal area, testis or labium.
  • May be provoked by alcohol, diuretics or high fluid intake.
  • May be associated with ipsilateral back pain.
• On palpation, loin tenderness and, occasionally, enlarged kidney. Clinical presentation may be dominated by symptoms of UTI and signs of septicaemia.
• Nausea and vomiting are common with acute obstruction.
• Anuria suggests bilateral 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 a large volume of residual urine in the bladder, it may present with frequent passage of small volumes, possibly with incontinence.
• May be complicated by acute retention associated with an UTI.

Idiopathic retroperitoneal fibrosis

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

• Check U&Es and estimated glomerular filtration rate:
  • 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 the acute phase.
• FBC - looking for anaemia of renal failure and evidence of infection.
• Urinalysis to screen for infection.
• Urine microscopy and culture in chronic obstruction and after relieving acute obstruction.
• Blood cultures if there are septic symptoms/signs.
• Ultrasound is the first-line choice for imaging in suspected chronic upper tract obstruction.
• IV urography or unenhanced CT scan, 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 a distended bladder or a transrectal ultrasound of the 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 measurement of urinary flow rates are used to investigate chronic lower tract obstruction.
• Suspected prostatic enlargement - serum PSA, ultrasound, biopsy as appropriate.

• Urethral or suprapubic catheterisation
• Stenting the ureter
• Nephrostomy

Acute upper tract obstruction^5,6

See also separate articles Renal Stones (Nephrolithiasis) and Renal Colic.

• With renal and ureteric colic, most patients with a stone <5 mm in diameter, in the lower third of the ureter can be managed conservatively:
  • Acute symptoms rarely last for more than 72 hours.
  • Give pain relief with non-steroidal anti-inflammatory drugs (NSAIDs) - usually, IM diclofenac 75 mg, repeated after 30 minutes if there is no response or, alternatively, diclofenac suppositories 100 mg PR - or morphine (where NSAIDs are contra-indicated).
  • Discourage use of anticholinergics and high fluid intake.
• With larger stones or those in the upper ureter, consider lithotripsy. In there is persistent colic, consider endoscopic investigation.
• If there is clinical evidence of infection with obstruction, it is imperative to establish drainage as soon as possible. Normally, a percutaneous insertion of a needle above the obstruction is performed to provide a 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, e.g. sloughed papillae and blood clots or tumours, there is a need to treat the underlying cause as well as relieve the 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.

Pelvi-ureteric junction (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.⁷
• Open pyeloplasty in primary idiopathic obstruction.
• Ureteroscopic endoureterotomy is used to treat ureteric strictures.⁸

Malignant obstruction

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

Idiopathic retroperitoneal fibrosis⁹

See separate article Retroperitoneal Fibrosis (Peri-aortitis) for fuller discussion of management.

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

Benign prostatic hyperplasia (BPH)¹⁰

See separate articles: Benign Prostatic Hyperplasia, and Lower Urinary Tract Symptoms in Men.
In general:

• 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 treatment involves the use of alpha-blockers and 5-alpha reductase inhibitors.¹¹
• Surgery is less frequent now given more effective medical treatment and, increasingly, offers less invasive options compared with the standard transurethral resection of the prostate (TURP), such as transurethral microwave thermotherapy or various laser procedures.¹²

Congenital obstructive nephropathy¹³

See also separate article Childhood Urinary Tract Infection.

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 cystoscopy¹⁴ (allows endoscopic visualisation and obliteration of obstructions such as posterior urethral valves) and vesico-amniotic shunts¹⁵ (a decompression procedure), remain experimental.¹⁶

Children with recurrent UTI or possible obstruction (e.g. high blood pressure, poor growth, poor urine flow, antenatally diagnosed renal abnormality, a family history of vesico-ureteral reflux or renal disease, an enlarged bladder or abdominal mass or evidence of spinal lesion) should be assessed rapidly to prevent obstructive renal failure.¹⁷

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

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• Burnett AL, Wein AJ; Benign prostatic hyperplasia in primary care: what you need to know. J Urol. 2006 Mar;175(3 Pt 2):S19-24. [abstract]
• Vaglio A, Salvarani C, Buzio C; Retroperitoneal fibrosis. Lancet. 2006 Jan 21;367(9506):241-51. [abstract]