Which statement regarding casts is incorrect?

• A. Casts dissolve in acidic urine
• B. A few hyaline or granular casts may be seen in normal urine
• C. All casts are cylindric with parallel sides
• D. Casts may be disrupted with high-speed centrifugation and rough sample handling

Answer: (C)

Casts are cylindrical formations made in the renal tubules from proteins and cells, but they do not all conform to a perfect cylinder with parallel sides. In reality, casts come in a variety of shapes and sizes: some are broad and widen as they reflect dilation of tubules, others are irregular, curved, or broken pieces. That variability means the statement claiming all casts are cylindric with parallel sides is not accurate.

Understanding the other points helps solidify this: a few hyaline or granular casts can indeed be found in normal urine, so that statement is true and reflects that casts can appear even without disease. Casts are fragile and can be disrupted by rough sample handling or high-speed centrifugation, so that statement is also true. The notion that casts dissolve specifically in acidic urine isn’t a definitive or reliable rule for their behavior, so it isn’t a defining characteristic of casts.

So, the key idea is that casts are not uniformly shaped cylinders with parallel sides; their diverse forms make that statement incorrect.