From the Guidelines
Urinary casts are a crucial diagnostic tool in nephrology, providing valuable information about kidney health and underlying conditions, and their presence and type should prompt further evaluation and referral to a nephrologist if necessary, as suggested by the most recent guideline 1. The type of cast observed is essential in determining the location, severity, and nature of kidney or urinary tract disorders.
- Hyaline casts, composed mainly of protein, may appear with strenuous exercise, fever, or dehydration and are generally benign in small numbers.
- Red blood cell casts strongly indicate glomerulonephritis or other conditions causing bleeding within the kidneys, as they are virtually pathognomonic for glomerular bleeding 1.
- White blood cell casts suggest kidney inflammation or infection, particularly pyelonephritis.
- Granular casts, containing degraded cellular material, can indicate acute tubular necrosis or other kidney damage.
- Waxy casts, which have a smooth appearance, typically suggest chronic kidney disease.
- Fatty casts containing lipid droplets may indicate nephrotic syndrome.
- Epithelial cell casts point to tubular damage, while bacterial casts confirm urinary tract infection. The presence of significant proteinuria, red cell casts, or renal insufficiency, or a predominance of dysmorphic red blood cells in the urine, should prompt an evaluation for renal parenchymal disease or referral to a nephrologist, as recommended by the American Urological Association (AUA) guideline 1. The most recent guideline 1 emphasizes the importance of referring patients with suspected medical renal disease for nephrologic evaluation, while still performing risk-based urologic evaluation. In clinical practice, the presence of urinary casts should be evaluated in the context of the patient's overall clinical presentation, and further testing and referral to a specialist should be considered as needed, based on the most recent and highest quality evidence available 1.
From the Research
Urinary Casts and Their Meaning
- Urinary casts are a useful predictor of acute kidney injury (AKI) in patients with acute heart failure (AHF) 2
- The presence of cellular casts in patients with AHF is associated with an increased risk of developing hospital-acquired AKI 2
- Urinary casts can be used as a simple and non-invasive method to detect impaired kidney function in patients with AHF 2
Association with Kidney Disease
- The use of angiotensin II receptor blockers (ARBs) and angiotensin-converting enzyme inhibitors (ACEIs) is recommended for patients with chronic kidney disease (CKD) and proteinuria 3
- However, the prescription rate of ARBs and ACEIs is lower in patients with CKD stage G1-G5 compared to those with CKD stage G1-G3 3
- The use of ACEIs and ARBs has been shown to preserve residual kidney function in peritoneal dialysis patients 4
Clinical Outcomes
- Exposure to ACEIs or ARBs after AKI is associated with lower risks of all-cause mortality, recurrent AKI, and progression to incident CKD 5
- Continued use of ACEIs or ARBs after AKI may have a survival benefit, but also increases the risk of hyperkalemia 5
- The impact of ACEIs and ARBs on clinical outcomes in patients with AKI or acute kidney disease (AKD) is still unclear and requires further study 6, 5