Lower urinary tract obstruction

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•148• Chapter 13 Lower Urinary Tract Obstruction M. Y. Kyei Introduction Lower urinary tract obstruction (LUTO) refers to conditions that may block the flow of urine from the bladder leading to difficulty with voiding and associated poor urinary stream. The lower urinary tract, comprising the bladder and urethra, acts as a functional unit that allows low pressure storage of urine and subsequent emptying (i.e. voiding) at intervals when appropriate. The urinary bladder acts as a reservoir for urine, storing the urine at low pressures. The first sensation of bladder distension occurs when the bladder gets filled with about 150mls of urine. However, voluntary control through the pontine micturition centre allows further storage to about 300-450mls of urine. Thereafter, there is an intense desire to void that causes the spinal micturition reflex to override that of the voluntary control leading to spontaneous voiding. At the time of voiding, there is contraction of the detrusor (or bladder) muscles, relaxation of the bladder neck and the external urethral sphincter allowing urine to flow. Urethral distention which results from the flow of urine through the urethra stimulates stretch receptors in the urethral wall which reflexly reinforce detrusor contraction and facilitate complete bladder emptying (urethrovesical reflex).1 In the presence of poor bladder contraction, abnormal sphincter function (i.e. non-relaxation) and anatomic obstructions, urine flow is impeded, leading to the symptoms and signs of lower urinary tract obstruction. LUTO results in the development of some secondary changes in the bladder. These include hypertrophy of the bladder/ detrusor muscles and increase collagen deposition in the bladder wall leading to the •149• Lower Urinary Tract Obstruction development of trabeculations and saccules. In severe cases there is the formation of bladder diveticula. The increase in intravesical pressure results in a back pressure effect leading to hydroureteronephrosis and subsequent renal failure. Materials This review considers primarily publications on various aspects of LUTO as have been undertaken in the Urology Unit of the Department of Surgery, Korle Bu Teaching Hospital. Reference has also been made to the preliminary findings of ongoing research work in the Unit. International publications as pertain to lower urinary tract obstruction have also been cited as deemed appropriate. Causes The causes of lower urinary tract obstruction include the following: benign prostatic hyperplasia, prostate cancer, urethral stricture and bladder neck tumours. It may also be caused by neurologic dysfunction emanating from disease or injury to the central or peripheral nervous systems such as spinal cord compression and radiculopathies due to osteoarthritis of the thoracolumbar spine and spondylolisthesis. The neurologic dysfunction may take the form of bladder weakness or incoordination between the bladder and external urethral sphincter, known as detrusor-sphincter-dyssynergia. Generally, the causes of lower urinary tract obstruction show some variation according to age. The Ghanaian experience is also in support of this assertion. Urethral strictures Urethral stricture is the narrowing and loss of distensibility of the urethra resulting from fibrosis which may be due to infection, trauma or malignancy. Rarely, it may be congenital in origin. Infection is the commonest cause of urethral strictures in Ghana. Trauma as a cause results from road traffic accidents and instrumentation such as urethral catheterization. The infective conditions comprise gonococcal and non-gonococcal urethritis. This is reflected in the fact that the majority of patients are relatively young. •150• Chapter 13 The patients present with lower urinary tract obstructive symptoms which include hesitancy, straining at micturition, poor or weak urinary stream (or dribbling stream when severe), intermittency and feeling of incomplete bladder emptying. They also present with irritative symptoms such as frequency of micturition, urgency, nocturia and urge incontinence. Others may present with symptoms suggestive of complications. These include haematuria, dysuria or an intense spasmodic pain felt at or just after micturition; they are usually secondary to urinary tract infection or bladder/ urethral calculi. Acute urinary retention (i.e. inability to pass urine despite the urge and in the presence of painful distended bladder) is also a common mode of presentation. On physical examination the following signs, some of which are also complications of urethral stricture, may be found, namely: urethral induration, paraurethral abscess and urethrocutaneous fistula. Examination may also show a grossly swollen scrotum, the result of extravasation of urine, which may progress to Fournier’s gangrene. The passage of a urethral catheter is unsuccessful in the presence of a urethral stricture, with the catheter being arrested at the site of the stricture. In patients presenting with acute retention...