Hyaline casts are formed from the precipitation and buildup of protein in the distal and collecting tubules of the kidneys and are called casts because they assume the shape of the tubules themselves. Their presence depends on the flow of urine, urine pH, and if present the degree of proteinuria.
While they are associated with proteinuria they may also occur with dehydration, fever, concentrated acidic urine, or heavy exercise.
Dvanajscak, Zeljko et al. “A practical approach to the pathology of renal intratubular casts.” Seminars in diagnostic pathology vol. 37,3 (2020): 127-134. doi:10.1053/j.semdp.2020.02.001
Pagana, Kathleen Deska; Pagana, Timothy J.; Pagana, Theresa N. Mosby's Diagnostic and Laboratory Test Reference. Elsevier Health Sciences. 2019.
They are usually considered benign versus pathological but may be associated with glomerulonephritis.
With proteinuria, the presence of hyaline casts indicates possible damage to the glomerular membrane, which permits leakage of proteins. Consider the possibility of the following:
- Malignant hypertension
- Chronic renal disease