Specific causes of obstruction

Pelviureteric junction obstruction

This appears to result from a functional disturbance in peristalsis of the collecting system in the absence of mechanical obstruction. Surgical attempts at correction of the obstruction by open or percutaneous pyeloplasty should be limited to patients with recurrent loin pain and those in whom serial excretion urography, background-subtraction isotope renography or measurements of GFR indicate progressive kidney damage. Nephrectomy to remove the risk of developing pyonephrosis and septicaemia is indicated if long-standing obstruction has destroyed kidney function.

An X-ray showing left pelviureteric junction obstruction.
An X-ray showing left pelviureteric junction obstruction.

Obstructive megaureter

This childhood condition may only become evident in adult life. It results from the presence of a region of defective peristalsis at the lower end of the ureter adjacent to the ureterovesical junction. The condition is commoner in males. It presents with UTI, flank pain or haematuria. The diagnosis is made on excretion urography or, if necessary, ascending ureterography. Excision of the abnormal portion of ureter with reirnplantation into the bladder is always indicated in children, and is indicated in adults when the condition is associated with evidence of progressive deterioration in renal function, bacteriuria that cannot be controlled by medical means or recurrent stone formation.

Retroperitoneal fibrosis (chronic periaortitis)

In this condition the ureters become embedded in dense retroperitoneal fibrous tissue with resultant unilateral or bilateral obstruction. The condition may extend from the level of the second lumbar vertebra to the pelvic brim. The incidence of the condition in men is three times that in women. An autoallergic response to leakage of material, probably ceroid, derived from atheromatous plaques is now considered to be the underlying cause of the condition. Recognized associations are with abdominal aortic aneurysm and prolonged exposure to the drug methysergide. The differential diagnosis includes retroperitoneal lymphoma or cancer.
Malaise, back pain, normochromic anaemia, uraemia and a raised erythrocyte sedimentation rate (ESR) are typical features. Excretion urography shows bilateral or unilateral ureteric obstruction commencing at the level of the pelvic brim. A periaortic mass may be seen on a CT scan.
Obstruction is relieved surgically by ureterolysis. Biopsy should be performed at operation to determine whether there is an underlying lymphoma or carcinoma. Corticosteroids are of benefit, and in bilateral obstruction in frail patients it may be best to free only one ureter and to rely upon steroid therapy to induce regression of fibrous tissue on the contralateral side, since bilateral ureterolysis  is a major operation. In some patients, surgery alone or steroid therapy alone may suffice, but in the majority both surgery and subsequent corticosteroid therapy appear to be necessary.
Response to treatment and disease activity are assessed by serial measurements of ESR and GFR supplemented by isotopic and imaging techniques including CT scanning. The latter method enables the size of the retroperitoneal mass to be assessed. Relapse after withdrawal of steroid therapy may occur and treatment may need to be continued for years. Long-term follow-up is mandatory. Benign prostatic hypertrophy Benign prostatic hypertrophy is a common cause of urinary tract obstruction. It is described.

Prognosis of urinary tract obstruction

The prognosis depends upon the cause and the stage at which obstruction is relieved. In obstruction, four factors influence the rate at which kidney damage occurs, its extent and the degree and rapidity of recovery of renal function after relief of obstruction. These are:
1 Whether obstruction is partial or complete
2 The duration of obstruction
3 Whether or not infection occurs
4 The site of obstruction
Complete obstruction for several weeks will lead to irreversible or only partially reversible kidney damage. If the duration of complete obstruction is several months, total irreversible destruction of the affected kidney will result. Partial obstruction carries a better prognosis, depending upon its severity.
Bacterial infection coincident with obstruction rapidly increases kidney damage.
Obstruction at or below the bladder neck may induce hypertrophy and trabeculation of the bladder without a rise in pressure within the upper urinary tract, in which case the kidneys are protected from the effects of backpressure.

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