Most people have some sediment in their urine. Whether this is normal depends upon what is in the sediment and how much sediment is present.
Sediment in urine consists of cells, debris and other solid material. When a patient provides a urine specimen to a medical provider, labs often spin the specimen down in a centrifuge and examine the sediment under a microscope.
Urinary sediment from healthy people "contains a small number of cells and other debris shed from the inside of the urinary tract," according to the "Merck Manual." The Texas Collaborative Group confirms this and adds that urine from healthy people contains substances that form in the kidney, ureter, bladder and urethra.
People with urinary tract infections have more sediment than do healthy people. This sediment includes protein, leukocytes, or white blood cells, and bacteria. Protein in the urine can be found with many other disorders, but the presence of bacteria is unique to persons with infections. In this instance, doctors consider the urine sediment to be abnormal.
Red Blood Cells
According to the Texas Collaborative Group, microscopic analysis of sediment from healthy people reveals two to three red blood cells per high-powered field. The presence of more red blood cells than this is called hematuria, which is commonly known as blood in the urine. Hematuria may be caused by kidney disease, urinary tract infections, renal infarcts, glomerular disease or tumors involving any part of the urinary tract.
A large number of red blood cells in the urine is also associated with trauma related to placement of a catheter or passage of a kidney stone.
The presence of casts in urine sediment is never normal. Casts are abnormally shaped cells, parts of cells and general crud. There are seven distinctly different types of casts: hyaline, red cell, white cell, granular, epithelial, waxy and fatty. While all suggest that the patient has kidney disease, different types of casts may predominate during different stages of the disease. For example, hyaline casts are seen in patients with very mild kidney disease, but waxy casts are seen in those with advanced disease.
If abnormal sediments are present, some type of follow-up is necessary. If the results are not far out of normal range, doctors may order routine urinalysis to be performed at regular intervals. If the urine sediment is very abnormal, doctors may order a kidney biopsy. This latter step is more common if the patient has extremely high levels of urine protein.