Ancient doctors used to attach even greater significance to examination of the urine than do moderns, but actually they knew very little about it. They based their judgments largely on color, odor, and quantity, which were easily determined.
Painful urination is usually associated with infection, irritation, or inflammation in the lower part of the urinary tract and to the passages of stones. Any obstruction to the flow of urine may be painful. Such conditions may also cause frequent urination, but that may be due as well to excitement or anxiety. Hesitancy in urination may also be due to psychological causes. Failure to control the flow of the urine, which is called incontinence, may come in times of great fright or during unconsciousness, but children may fail to control the urine for a variety of both physical and mental causes.
Increase in the amount of urine associated with frequent urination may be due to increased intake of fluids, or to failure of sweating. A sudden change from warm to cold weather causes a rise in the volume because of lessened perspiration.
Certain diseases that affect the urinary mechanism, including conditions affecting the pituitary gland and diabetes, cause an increase in amount of urine. People with dropsy or collection of fluid in the body may respond to rest, or treatment with certain drugs that rid the body of large amounts of fluid through the urine. Similarly a diminished output may result from failure of the heart to put enough blood through the kidney and from collection of fluid in the tissues and cavities of the body.
Usually the quantity of urine is diminished during sleep. Anything that disturbs sleep may result in urination at night. Irritations along the tract may also cause awakening and urination at night.