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Urinary tract obstruction 

Urinary tract obstruction

Chapter:
Urinary tract obstruction
Author(s):

Muhammad M. Yaqoob

and Islam Junaid

DOI:
10.1093/med/9780199204854.003.2117

July 30, 2015: This chapter has been re-evaluated and remains up-to-date. No changes have been necessary.

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date: 25 March 2017

Obstructive nephropathy can manifest as either a sudden or an insidious decline in renal function, which can be can halted or even reversed by relief of obstruction. Obstruction can be due to anatomical or functional abnormalities of the urethra, bladder, ureter, or renal pelvis, which may be congenital or acquired, and it can also occur as a consequence of diseases extrinsic to the urinary tract. Although dilatation of the outflow system proximal to the site of obstruction is a characteristic finding, widening of the ureter and/or pelvicalyceal system does not necessarily indicate the presence of obstruction, and flow may be obstructed without such dilatation.

Calculi and pelviureteric junctional obstruction are common causes of unilateral obstruction, while prostatic enlargement, stone disease, and bladder and pelvic tumours account for about 75% of cases of bilateral obstruction in developed countries.

Acute upper urinary tract obstruction

Clinical features—typically gives rise to pain in the flank, which may radiate to the groin. Ultrasonography is useful for determining the presence or absence of obstruction, but not good for determining its cause, with unenhanced spiral CT the investigation of choice (or intravenous urography if CT is not available).

Management—this depends on the cause, and whether or not there is accompanying infection. Drainage must be established as a matter of urgency if the patient has clinical features of local or systemic sepsis, usually by percutaneous antegrade nephrostomy. Urinary stones less than 5 mm in maximum diameter will usually pass spontaneously: extracorporeal shock-wave lithotripsy and/or endoscopic manoeuvres are used when colic is persistent.

Acute lower urinary tract obstruction

Clinical features and management—symptoms of bladder outflow obstruction with hesitancy, poor urinary stream, and terminal dribbling often precede acute urinary retention. Suprapubic pain along with a palpable bladder is sufficient evidence for immediate catheterization, although ultrasonography will confirm or refute the presence of bladder distension if there is doubt about the diagnosis.

Chronic upper urinary tract obstruction

Clinical features and management—obstruction must be excluded in all patients with unexplained renal failure. Ultrasonography is the usual screening test, but this cannot distinguish between an obstructed distended system and a baggy, low-pressure dilated system. Furosemide renography can be helpful when there is doubt, but the ‘gold standard’ to determine whether or not there is functionally significant obstruction remains a trial of drainage (usually by antegrade nephrostomy). Specific management will depend upon the cause of obstruction.

Retroperitoneal fibrosis

Epidemiology and aetiology—this is a rare condition characterized by the presence of fibro-inflammatory tissue which typically surrounds the abdominal aorta and iliac arteries and extends into the retroperitoneum to entrap the ureters, causing unilateral or bilateral obstruction. Two-thirds of cases are idiopathic; the remainder are attributable to drugs, malignant diseases, or other causes.

Clinical features—early symptoms are constitutional upset, often accompanied by dull back, flank, and abdominal pain; later disease is characterized by symptoms related to the entrapment of retroperitoneal structures, most commonly ureteric obstruction.

Diagnosis—CT reveals findings typical of urinary tract obstruction together with a periaortic mass. CT-guided needle biopsy may be sufficient to diagnose lymphoma or carcinoma with confidence, but laparotomy is typically required to obtain a sufficiently large sample to exclude these conditions, the microscopic appearance of idiopathic retroperitoneal fibrosis being characterized by fibrotic tissue infiltrated with a mixture of mononuclear cells.

Management—the objective is to relieve ureteric obstruction (when present), suppress the acute phase reaction, halt the progression of fibrosis, and prevent relapse. Urgent relief of obstruction is generally recommended if there is significant renal dysfunction: this may be achieved by antegrade nephrostomy, retrograde insertion of ureteric stents, or open surgical ureterolysis, but these are not required if renal function is stable and normal. Standard medical treatment is to give corticosteroid therapy, typically beginning with prednisolone 1 mg/kg per day (maximum 60 mg/day) for 4 to 6 weeks and then gradually reducing at a rate determined by monitoring of the patient’s symptoms, inflammatory markers (erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), etc.) and repeated imaging. Recurrence of disease occurs in 10% to 30% of cases, usually within the first year but sometimes many years later, hence long-term surveillance is required.

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