ABSTRACT
Lower urinary tract calculi In most Western countries, primary bladder calculi are rare in women with normal lower urinary tracts, but they do occur in Pakistan, India, and the Middle Eastern countries where a low-protein, high-carbohydrate diet and chronic dehydration predispose to endemic stones.1 Calculi in women in industrial countries occur predominantly as a result of structural or functional abnormality of the lower urinary tract.1,2 Bladder calculi need a nidus to grow, and can develop as an encrustation on foreign bodies such as suture material (Figure 9.1), synthetic slings (Figure 9.2), and remnants of catheters. They also can occur secondary to stasis and infection, developing in bladder diverticulae (Figure 9.3), or in women with ureteroceles (Figure 9.4), outlet obstruction, and bladder trabeculation. Calculi have also been reported in women with vesicovaginal fistulae,3
as a result of migration of an intrauterine device into the bladder,4 and in women with severe vaginal prolapse5 and outlet obstruction. Women who have undergone bladder surgery such as vesicovaginal fistula repair (see Figure 9.3) or bladder augmentation procedures are at increased risk of developing calculi even in the absence of intravesical
suture fragments or other foreign bodies. Less commonly, bladder calculi can originate in the kidney. Other possible inciting factors may be poor fluid intake, a diet with high protein, calcium, phosphate, or oxalate intake, and metabolic disorders resulting in increased calcium, cystine, and uric acid urinary excretion. Urinary tract infection (UTI) can occur as a result of calculi, although urinary infection can contribute to stone formation. Bacteria, particularly urea-splitting organisms such as Proteus, Klebsiella, Serratia, and Enterobacter spp., produce an alkaline urine which promotes stone formation (struvite or infection stone). Proteus mirabilis contains the enzyme ‘urease’, which breaks urea to ammonia and causes intense alkalinization of the urine, with precipitation of calcium, magnesium, ammonium, and phosphate salts and the subsequent formation of branched struvite renal stones.
