Bladder stones in adults usually mark bladder outlet obstruction, a foreign body, or a diversion; in children they reflect a low-protein diet. Prostatic, urethral, and preputial calculi are less common and have characteristic associations.
Bladder Stones
Primary bladder calculi form without any functional, anatomic, or infectious factor — 9–33× more common in boys, classically in children on low-protein, low-phosphate diets (producing ammonium acid urate stones). They are usually solitary, rarely recur, and are prevented by dietary modification.
Secondary bladder calculi arise from:
- Bladder outlet obstruction — the most common cause (concentrated, acidic urine).
- Neurogenic bladder / spinal-cord injury — intermittent catheterisation carries a lower risk than an indwelling catheter, and suprapubic offers no advantage over urethral.
- Augmentation or urinary diversion (incidence 10–52.5%; mostly struvite and calcium phosphate; females exceed males after augmentation), transplant, and foreign bodies (suture or clips from prior surgery).
In adults, bladder stones are usually uric acid (non-infected urine) or struvite (infected urine); calcium oxalate or cystine suggests a passed renal stone. The commonest symptom is terminal gross haematuria, and cystoscopy is the most accurate diagnostic test. Management is endoscopic (holmium laser is the modality of choice) or percutaneous cystolithotomy; endoscopy through a continent catheterisable channel is avoided because it can disrupt the continence mechanism. There is no role for medical therapy — recurrence is prevented by relieving the outlet obstruction.
Prostatic, Urethral, and Preputial Calculi
- Prostatic calculi — from inspissated prostatic secretions in the large ducts (posterior/posterolateral zones); composed of calcium phosphate and carbonate; usually asymptomatic and do not affect PSA.
- Urethral calculi — in females, nearly all are associated with a urethral diverticulum; delayed diagnosis can produce urethrocutaneous or urethrorectal fistulae. Posterior-urethral stones can be pushed back into the bladder for fragmentation, whereas anterior-urethral stones cannot.
- Preputial calculi — associated with severe phimosis; resolved by circumcision and stone removal.
Self-Test
1. Which patients form primary bladder calculi? Children, especially boys, on low-protein, low-phosphate diets — typically ammonium acid urate stones.
2. What is the typical composition of secondary bladder calculi in adults? Uric acid (non-infected urine) or struvite (infected urine); struvite and calcium phosphate in augmented bladders.
3. When should endoscopic management of bladder calculi be avoided? Through a continent catheterisable conduit, where it can disrupt the continence mechanism.
4. What abnormality is associated with female urethral calculi, and what can untreated stones cause? A urethral diverticulum; untreated stones can cause urethrocutaneous or urethrorectal fistulae.
5. How are preputial calculi treated? Circumcision with calculus removal.