A primary bladder stone is one that develops in sterile urine; it often originates in the bladder. A secondary stone occurs in the presence of infection, outflow obstruction, impaired bladder emptying or a foreign body. Incidence Until the twentieth century, bladder stone was a prevalent disorder among poor children and adolescents. As a result of improved diet, especially an increased protein: carbohydrate ratio, primary vesical calculus is rare.
COMPOSITION AND CYSTOSCOPIC APPEARANCE
Most vesical calculi are mixed. An oxalate calculus is a primary calculus that grows slowly; usually, it is of moderate size and solitary, and its surface is uneven (Figure 77.24). Although calcium oxalate is white, the stone is usually dark brown or black because of the incorporation of blood pigment. Uric acid calculi are round or oval and smooth, and vary in colour from yellow to brown. They occur in patients with gout but are also found in patients with ileostomies or bladder outflow obstruction. A cystine calculus occurs only in the presence of cystinuria and is radio-opaque because of its high sulfur content. A triple phosphate calculus is composed of ammonium, magnesium and calcium phosphates and occurs in urine infected with urea-splitting organisms. It tends to grow rapidly. In some instances it occurs on a nucleus of one of the other types of calculus; more rarely it occurs on a foreign body. It is dirty white in colour and of chalky consistency. A bladder stone is usually free to move in the bladder and it gravitates to the lowest part of the bladder. Less commonly, the stone is wholly or partially in a diverticulum, where it may be hidden from view. Clinical features Men are affected eight times more frequently than women. Stones may be asymptomatic and found incidentally.
Frequency is the earliest symptom and there may be a sensation of incomplete bladder emptying. Pain (strangury) is most often found in patients with a spiculated oxalate calculus. It occurs at the end of micturition and is referred to the tip of the penis or the labia majora; more rarely it is referred to the perineum or suprapubic region. The pain is worsened by movement. In young boys, screaming and pulling at the penis with the hand at the end of micturition are indicative of a bladder stone. Haematuria is characterised by the passage of a few drops of bright-red blood at the end of micturition, and is due to the stone abrading the vascular trigone. Interruption of the urinary stream is due to the stone blocking the internal meatus. Urinary infection is a common presenting symptom.
Examination Rectal or vaginal examination is normal; occasionally, a large calculus is palpable in females. Examination of the urine reveals microscopic haematuria, pus or crystals that are typical of the calculus, e.g. envelope like in the case of an oxalate stone or hexagonal plates in the case of cystine calculi. In most patients the stone is visible on an ultrasound scan or a plain radiograph. Imaging of the whole of the urinary tract should be undertaken to exclude an upper tract stone. Nearly all stones can be dealt with endoscopically. In men with bladder outflow obstruction, endoscopic resection of the prostate should be performed at the same time as the stone is dealt with.