The color of carnal hematuria varies depending on the amount of bleeding and the acidity or alkalinity of the urine. The urine is dark and concentrated when there is a lot of bleeding; acidic urine is brown-black, brown, soy sauce, or dark teal; and alkaline urine is bright red, pink, or washboard-like.
Positive urine red blood cells (i.e., hematuria) are of glomerular and non-glomerular origin. The former is seen in various glomerular diseases, such as acute glomerulonephritis, asymptomatic hematuria, IgA nephropathy, chronic nephritis, purpura nephritis, and lupus nephritis; the latter is seen in renal tuberculosis, urinary stones, tumors, polycystic kidneys, acute cystitis, malformations, and hematologic diseases.
The common causes of microscopic hematuria in children and adolescents are acute upper respiratory tract infection, acute glomerulonephritis, urinary tract malformation and obstruction, or idiopathic hypercalciuria in children; in young adults, hematuria is more common due to urinary stones and chronic nephritis, and in women of childbearing age, hematuria is more often due to urinary tract infection; in older men, hematuria is more common due to prostatic hypertrophy secondary to urinary tract infection, prostate cancer, pelvic bladder tumor, kidney or ureteral stones. The incidence of hematuria in elderly men is high, and in elderly women, bladder tumors and urinary tract infections are common.