Content of staghorn calculus is

Ans. is 'a' i.e., Phosphate Types of renal calculusOxalate calculus (calcium oxalate)* Oxalate stones are irregular in shape and covered with sharp projections, which tend to cause bleeding.* The surface of the calculus is discoloured by altered blood. A calcium oxalate monohydrate stone is hard and radiodense.Phosphate calculus* A phosphate calculus is smooth and dirty white.* It tends to grow in alkaline urine, especially when urea-splitting Proteus organisms are present. As a result, the calculus may enlarge to fill most of the collecting system, forming a staghorn calculus.* Even a very large staghorn calculus may be clinically silent for years until it signals its presence by haematuria, urinary infection or renal failure.* Because they are large, phosphate calculi are usually easy to see on radiographic films.Uric acid and urate calculi* These are hard, smooth and often multiple.* They vary from yellow to reddish brown and sometimes have an attractive, multi- faceted appearance.* Pure uric acid stones are radiolucent and appear on an excretion urogram as a filling defect, which can be mistaken for a transitional tumour of the upper urinary tract.* The presence of uric acid stones is confirmed by CT. Most uric acid stones contain some calcium, so they cast a faint radiological shadow.* In children, mixed stones of ammonium and sodium urate are sometimes found. They are yellow, soft and friable. They are radiolucent unless they are contaminated with calcium salts.Cystine calculus* These uncommon stones appear in the urinary tract of patients with a congenital error of metabolism that leads to cystinuria.* Hexagonal, translucent, white crystals of cystine appear only in acid urine. They are often multiple and may grow to form a cast of the collecting system.* Pink or yellow when first removed, they change to a greenish colour when exposed to air.* Cystine stones are radioopaque because they contain sulphur, and they are very hard.Xanthine calculus* These are extremely rare. They are smooth and round, brick-red in colour, and show lamellation on cross-section. These stones are radiolucent.