The presence of which component in a urinalysis indicates bacteria or severe renal disease?

The presence of casts in a urinalysis can indicate conditions associated with significant kidney pathology. Casts are formed in the renal tubules and consist of proteins, cells, or other substances that become entrenched in the tubular structure. Their appearance signifies that there may be a process occurring within the kidney itself, such as inflammation, infection, or injury to the renal parenchyma.

For example, red blood cell casts are indicative of glomerular disease, while white blood cell casts can suggest pyelonephritis or other renal infections. These findings point to underlying renal dysfunction, highlighting why the presence of casts is significant in diagnosing various forms of severe renal disease.

While nitrites can indicate a urinary tract infection due to the presence of certain bacteria, the presence of casts is more directly correlated with serious renal conditions. Crystals and ketones, while they may suggest other metabolic or systemic issues, do not specifically point out significant renal disease when evaluated in the context of urinalysis.