Which type of cast indicates very slow glomerular filtration?

Granular casts are indicative of very slow glomerular filtration rates. The presence of granular casts in urine often signifies a degenerative process within the renal tubules. These casts form when tubule cells break down and release their cytoplasmic components into the tubular lumen, where they mix with the urine. Granular casts can be seen in conditions such as acute tubular necrosis or other forms of kidney damage, which correlate with a reduction in the ability of the kidneys to filter blood efficiently.

In contrast, hyaline casts are generally seen in normal urine or in cases of dehydration or concentrated urine, thus not indicating problems with glomerular filtration. Fatty casts are associated with nephrotic syndrome, which leads to a change in lipid metabolism rather than a slow glomerular filtration rate. Cellular casts arise from the presence of cells that become trapped in the kidney tubules but may not necessarily reflect glomerular filtration directly. Each type of cast provides specific diagnostic insights into renal pathology, but granular casts specifically highlight the issue of glomerular filtration slowing down significantly.