Which statement about casts is true?

Which statement about casts is true?

• A. A Casts are always formed in urine
• B. Casts are resistant to handling
• C. Casts dissolve readily in acid urine
• D. Casts may be disrupted with high-speed centrifugation and rough sample handling

Answer: (D)

Casts are fragile cylindrical structures formed in the renal tubules and shed into the urine. Because they are delicate, they can be disrupted by processing steps. This is why high-speed centrifugation and rough sample handling can break casts apart, making this statement true. The others aren’t reliable general rules: casts aren’t formed in urine itself but in the kidneys; they aren’t universally dissolved by acid urine (their stability depends on cast type and pH), and they are not resistant to handling—rough handling can disrupt them.

Casts are fragile cylindrical structures formed in the renal tubules and shed into the urine. Because they are delicate, they can be disrupted by processing steps. This is why high-speed centrifugation and rough sample handling can break casts apart, making this statement true. The others aren’t reliable general rules: casts aren’t formed in urine itself but in the kidneys; they aren’t universally dissolved by acid urine (their stability depends on cast type and pH), and they are not resistant to handling—rough handling can disrupt them.