FIRST, let's talk about where urine comes from, how it is formed and what are its normal content for us to say that the kidneys of the person is healthy.
An adult human has five liters (5000 ml) of blood circulating in his/her body, also called blood volume or normal cardiac output. Per minute, through the renal arteries 1/5 or 20 percent of that five liters go to the kidneys; 500 ml each to the right and to the left kidney. Glomerulus is the part of the kidneys which filters or acts as a sieve, the size of the opening strictly limits the passage of substances like sugar and proteins particularly albumin.
By then, the blood has been converted to GFR or glomerular filtration rate which now will journey to the so-called tubules of the nephron- the functional unit of the kidneys numbering 2-2.4 million, in which a lot of physical as well as chemical processes occur, so that by the time the fluid reaches the renal pelvis- the junction of the kidneys and the ureter, that fluid is already called urine.
A healthy person produces one ml of urine per minute, thus 60 ml per hour or about 1400-1500 ml per day. Doctors call it oliguria if urine output is less than 30 ml per hour or less than 400 ml per 24 hours.
Anuria is zero urine output which can be due to a lot of factors, among which is acute kidney failure. The adult urinary bladder full capacity is 500 ml but for healthy persons, they do not fill their bladder with that much volume of urine. Thru nervous mechanisms involving the S2S3S4 segment of the spinal cord, the urge to urinate occurs when the volume of urine in the bladder is from 120-150 ml.
Now since urination or micturition is basically reflexive inactivity, there is some amount of control from Higher Centers- brain- which allows the person to postpone or delay his/her going to the bathroom. However, comes a time or a volume of urine ( 300-350ml) is reached when no amount of voluntary control can prevent urine from leaking especially when the person coughs or sneeze or exert effort.
The so-called neurogenic bladder is seen in persons who had a stroke or other diseases or injuries affecting the nerves that contract the detrusor muscle thus, they reach 500 ml and only a catheter can facilitate the passage of their urine.
With the 8-10 glasses of water, urine should be clear. Turbid urine is abnormal and mostly due to infection, most common of which is by bacteria E. coli and Proteus vulgaris. It should not also be almost-water clear- it has to be straw-colored because of bile pigments in them, sourced from the normal death of red blood cells after 120 days.
Specific gravity measures the amount of substances dissolved in the urine; normal is from 1.004 to 1.024. Pyelonephritis or severe infection of the kidneys give very high sp-gravity due to microbes, diabetics too because of the sugar as well as other substances particularly ketone bodies. The other diabetes, insipidus is due to absence or deficiency of the hormone vasopressin or ADH- anti-diuretic hormone in which water is not adequately reabsorbed in the kidneys thus is lost in the urine, therefore he patient passes large amount of urine but very diluted, thus gravity is less than 1.004.
In the urine result, pus is the same as WBC, that is, in terms of indicating the presence of microbial infection and therefore should be 0-l per high power field (hpf) to be considered normal. RBC or red blood cell too should be 0-1 hpf, otherwise, here may be a stone going down the urinary tract, scraping and eroding its inner surface; or if it were a child, glomerulonephritis is a common cause.
Sugar and albumin should be negative or if traces are found, your doctor might require a repeat after several days. Cast is an unwelcome finding because they represent sloughing of the cells of the renal tubules and if they are persistently present in several urinalysis, your doctor might ask for blood tests particularly BUN- blood urea nitrogen and creatinine.
Crystals especially if they are diamonds are desirable but not in a urine specimen because they are harbingers of stone formation, if left unchecked, so note the presence of oxalates, urates and phosphates. The ph reaction should be acidic (3.5 to 6.5) because of the presence of sulfuric and phosphoric acid coupled each by sodium.
At this juncture, it is well to emphasize that the acidity of the urine has nothing to do with the hyperacidity of patients with peptic ulcer (hydrochloric acid). Sometimes, yeast is included among the urinary findings- not unusual among diabetes mellitus patients or persons who may have contracted the fungus through unprotected sexual activity. Lest we forget, a urine test is also a very practical method of establishing probable pregnancy.
Indeed, urinalysis is the most basic, practical first-line approach towards initial evaluation of kidney function. And our dear readers and friends would be nodding their heads in unison, agreeing that true enough, urinalysis is part and parcel of every basic laboratory tests.
Before there are very strict requirements in the gathering of urine specimen. However most of my pathologists-medtechnologists friends say that any urine might do but the ideal is still the early morning urine, caught midstream urine placed in a clean, sterilized bottle or container. Let's drink to that, water I mean!
Next week: Is there a male menopause?