Urolithiasis in the lower urinary tract

Abstract

I N COMPARISON to the upper urinary tract, lower tract calculi are infrequent. The majority are found in the urinary bladder. A ureteral calculus that spontaneously passes into the bladder may, on rare occasion, reside there for a considerable time. This is referred to as a migrant calculus. Otherwise, vesical calculi fall into three etiologic categories: primary, stasis, and foreign body nidus calculi. Primary or endemic calculi form in the urinary tract of patients, usually children, in whom obstruction, infection, or other known calculogenie factors are absent. They are especially prevalent in young boys of low socioeconomic class in the Middle and Far East, and are possibly related to deficiencies of milk or certain proteins in their diets. They are usually composed of ammonium hydrogen urate which may be admixed with calcium oxalate or, less frequently, calcium phosphate, and are nonopaque or poorly opaque.’ Radiologic discovery of calculi in the bladder or urethra occurs when evaluating such children for symptoms of lower tract irritation or intermittent involuntary interruption of the urinary stream (Fig. 1). The majority of secondary calculi occur in adults and are related to urinary stasis. The stasis is usually associated with bladder outflow obstruction in men with residual urine, vesical diverticula, or lower urinary tract infection. Women with a large cystocele and patients of either sex with neuropathic bladder dysfunction and residual urine, especially if infected, are also at risk for developing bladder calculi. These calculi may be of almost any composition, including uric acid, struvite, calcium phosphate, or