This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urology, Subject name: Anatomy
Not true about bladder stones is - 
Select and explain. 
A. Primary stones are rare, B. Max stones are radio opaque, C. Rare in Indian children, D. Small stones can be removed per urethra
C: Rare in Indian children
Answer: C: Rare in Indian children 
Explanation: " Vesical calculi are common in some pas of the country, eg. Rajasthan, Andhra Pradesh and some noheastern states. These stones are usually single and composed of ammonium acid urate and calcium oxalate (ie radioopaque stones). These calculi usually occur in boys below 5 yrs. of age." " Bladder stones are relatively uncommon in the U.S, but they do occur in children in pas of India, Indonesia, China and the middle east where diets low in phosphate and protiens result in ammonium urate stones. Primary bladder stone is one that develops in sterile urine & originates in kidney and passes down the ureter to the bladder, where it enlarges. Secondary bladder stones occur in presence of some infection, bladder outflow obstruction, impaired bladder emptying or a foreign body such as nonabsorbable sutures, metal staples or catheter fragments. Most of the bladder stones are secondary. Only some stones are primary. Kidney stones which are small enough to pass through the ureter into baldder are easily passed out through the urethra. Most bladder stones contain calcium and are therefore radiopaque.