Physical characteristics and abnormal constituents of urine part1

Appearance: Small quantity of blood in urine is often undetectable by inspection, but it gives the urine a smoky appearance. Large quantities of blood make the urine brownish or red. Colour variation from dark red -brown-black occurs due to presence of large amount of heamoglobin from lysed red blood cells, after mismatched blood transfusion or in black water fever. Drugs like tetracyclines, anthraquinonepurgatives, desferrioxamine, pheninedione, nitrofurantoin and nitridazole rifampacin, may discolour urine. Cloudiness of urine may be due to the presence of red or white blood cells, pus from bladder or kidney infection, bacteria, mucous and chyle. Phosphates and pus make freshly passed urine cloudy.

Odour: Foul smelling urine is a common symptom of urinary tract infection. Fruity odour is associated with diabetes mellitus, starvation, dehydration or ketone body formation. Patients with maple syrup urine diseases and phenyl ketonuria may present with distinctive odour of the urine.

Specific gravity: Low specific gravity (below 1.005) associated with diabetes insipidus, acute tubular necrosis, nephrogenic diabetes insipidus and pyelonephritis. High specific gravity (above 1.035) occurs in patients who are in shock or who suffer from nephritic syndrome, dehydration, and acute glomerulo nephritis.

PH: Ranges between 4.6 -8.0.High protein diets increase the acidity of urine; vegetarian diets increase the alkalinity. (Normal fresh urine is nearly always slightly acidic, except after a meal.) Value greater than 7 may be due to metabolic/ respiratory alkalosis, Fanconi’s syndrome. Ph value below 7 may be due to fever, phenyl ketonurea, alkaptonurea and acidosis.

Blood and tissue cells: Red blood cells in the urine can be due to vigorous exercise or exposure to toxic chemicals. High number of white blood cells in the urine is usually a symptom of urinary tract infection. Certain other causes of haematurea are bacterial infections, parasitic infections including malaria, obstructions in the urinary tract, scurvy, sub acute bacterial endocarditis, traumatic injuries, and tumors. A large number of cells from tissue lining can indicate damage to the small tubes that carry material into and out of the kidneys.(In females, one should make sure that the urine sample was not contaminated with menstrual blood from vagina.)

Casts: They are small fibrous objects that are formed when protein and other materials settle in the kidney tubules and collecting ducts. Large number of casts in urine specimen is a sign of kidney disease.

Sources

Hutchison’s clinical method

Davidson's Principles and practice of medicine

Haematurea