Of the routine chemical tests performed on urine, the most indicative of renal disease is the protein determination. Proteinuria is often associated with early renal disease, making the urinary protein test an important part of any physical examination. Normal urine contains very little protein, usually less than 100-300 mg/L or 100 mg per 24 hours is excreted. This protein consists primarily of low-molecular-weight serum proteins that have been filtered by the glomerulus and proteins produced in the genitourinary tract. Due to its low molecular weight, albumin is the major serum protein found in the plasma, the normal urinary albumin content is low because the majority of albumin presented in the glomerulus is not filtered, and much of the filtered albumin is reabsorbed by the tubules. Other proteins include small amounts of serum and tubular microglobulins. Uromodulin produced by the renal tubular epithelial cells and proteins from prostatic, seminal, and vaginal secretions. Uromodulin is routinely produced in the distal convoluted tube, and forms the matrix of casts.