URINARY SYSTEMS – Urinalysis
Somebody often complains about yellowish urine and some others about very hot urine. What is the inference?
Actually, yellowish urine denotes its concentration. It is always seen in cases of scanty urine, especially after heavy exercises or long distance travel or sunbath. Urine is scanty and concentrated due to an alternative pathway of water elimination, i.e., through sweat, to maintain the thermostat of the body. If sweat is more, then urine will be concentrated more due to less availability of water to carry solutes. If water intake is increased, the concentration automatically gets diluted and the colour will resume to normal. But if you find yellowish urine even after plenty of water intake, it is better to rule out jaundice.
Usually, morning urine is more concentrated than at other times since we do not drinking water at night. So, to maintain the water balance of our body, less water is excreted and thus the urine becomes more concentrated.
Hot urine is a reflection of the body’s internal temperature, i.e., it is felt more during the cold weather (where the body maintains internal temperature as warm as it can) or after violent exercises (where the body temperature is high due to increased body metabolism).
How to test urine? By urinalysis
What for it should be analysed in the lab? Urine tests are simplest, painless, cheapest, non-invasive and highly informative, which can guide treatment. In all urinalysis, normal value varies with age, sex, time, device used, solvents or kit used, analyser, sample collecting techniques (after fasting, before fasting, etc.), etc.
Even though urinalysis is mostly done in case of a urinary tract infection and renal complaints, it is necessary to do in all cases of prolonged complaints or diseases, to rule out any systemic complication. Also, it should be made part and parcel of routine periodic health examination to analyse our body condition.
How should urine be analysed? For analysis, urine samples must be collected in a proper way, i.e. care must be taken in collecting the sample in a clean, fresh, sterilised bottle or container without any contamination. The best urine sample is midstream of first (morning) urine.
Most of the laboratories are now doing urine test and blood test with automated analyser which gives report in printed colour strip form. They measure everything electronically.
Microscopic examination – urine should always be evaluated microscopically for the presence of casts, crystals, cells and bacteria.
Lab or chemical analysis of urine – is done for evaluating pH, specific gravity, sugar, albumin, ketone bodies, bile salts, pigments, blood, etc.
pH – (hydrogen ion concentration which helps in denoting acidity or alkalinity of the solution variation from 1-14 i.e. from most acid to most alkali). Urine is usually slightly acidic i.e. below 7 (indicated by blue litmus paper turning red on getting dipped) but normal range is between 5.5- 8.0. Occasionally, it becomes alkali (red litmus paper turns blue) during infection where pH is raised.
pH of urine in case of child – 6.2 – 6.8
pH of urine in case of adult – 5.2- 8.0
Specific gravity of the urine changes according to the volume of the urine and solute present in the urine. In case of reduced volume of the urine in normal excreting solutes, the sp gravity is raised; whereas in increased volume of urine with normal excreting solutes, it is lowered. Increased level of protein in the urine also elevates the sp gravity.
Humans are soft-skinned persons who sweat more to produce more hypertonic (highly concentrated) urine. Insects, spiders, reptiles, birds and other animals excrete less hypertonic urine since they have hard body protective surface or hair or feathers which usually protect loss of fluids from sweat. Fish and other water animals always pass hypotonic (less density) urine. Also, humans take a good amount of sodium salt in diet which will hold or retain water content in the body. The distal renal tibules in humans are also designed in such a way to reabsorb most of the water and salts to maintain our body water balance which causes urine to be more hypertonic.
Specific gravity normally ranges from – 1.001 – 1.035
Normal sp gravity of urine in children – 1.002
Normal sp gravity of urine in adult – 1.030
Protein in urine (proteinuria) – Acceptable normal excretion range of protein in urine is below 0.15 gms/24 hours of urine. This occurs usually due to day-to-day activities or exercises where protein metabolism is used for energy. Proteins occur in urine in diseases like kidney disorders (nephrotic syndrome, renal failure, pyelonephritis, etc.) heart failure, gout, malignant hypertension, toxicity of high fever, drugs, eclampsia (convulsive disease due to high BP and proteinuria in pregnant women), etc. They usually appear as casts in urine, which can be confirmed by their coagulation or white precipitation while heating.
Albumin – Normal range of albumin in urine is <3.5mg/mmol. Test for Microalbuminuria (increased elimination of albumin) is most important test to be done in diabetic patients to rule out kidney involvement or damage. Since albumin level varies with day-to-day activities and exercises, it is better to test after overnight rest. It is often traced in cases of heart failure, renal failure, hypertension, urinary tract infection, etc.
Urea – is the end product of protein metabolism. A high protein diet will increase urea level (normal 20-40 mg /100ml) in blood and urine. It will be abnormally high in cases of kidney disorders (where there is defect in filtration and elimination) and diabetes (due to use of protein metabolism for energy since glucose metabolism is impaired). Normal acceptable range of urea in urine is 180-600mmol/24 hours.
Ketone bodies (Acetone) – normal level in urine is <500mg/24 hours – starvation and uncontrolled diabetes can elevate the levels.
Bile salts and bile pigments- give yellow colour to urine when they occur during jaundice
Urobilinogen – is excreted in increased amount in case of liver disorders.
Other normal levels
Sodium – 100 -200mmol / 24 hours
Potassium – 25 – 100mmol / 24 hours
Calcium level – 0 – 300 mg / 24 hours
Phosphates – 15 -50mmol / 24 hours
Urate 1.2 -3.0mmol / 24 hours
Copper – <.6micromol / 24 hours
Pus cell and bacteria should be absent in urine. Their presence always indicates infection (pyelonephritis, urethratitis, uretitis, cystitis, etc.). If there are pus cells and bacteria, culture must be done to rule out infection. Pus cells can be easily identified after centrifuge and sedimentation.
Normally, kidney-filtered or bladder-stored urine is sterile. The small number of bacteria present in the urine while passed is due to contamination of bacterial flora in the urethra. If the result denotes more than 10,000 colonies of bacteria, then it is said to be confirmed bacterial infection or otherwise it may be due to urethral flora contamination. The common bacteria which infect are Coliforms, Enterococci, Gram negative rods, etc.
Bacteria will not sediment by centrifuge, so to identify it, culture or growth of bacteria in a medium is usually followed which can easily show the type of bacterial infection. Nowadays culture tests are done with sensitivity tests, so that the correct drug can be administered in the initial period itself.
Casts are coagulated proteins seen as sediments in urine, so proteinuria is the precursor of cast formation. The blood cells (RBCs & WBCs) and epithelial cells can get lodged to this and form erythrocyte casts, leucocyte casts and epithelial casts. In normal conditions, casts will not be seen in urine.
Hyaline casts – are protein casts which occurs usually after violent exercises and also in case of chronic kidney failure
Leucocytes casts occur after urinary tract infection
Erythrocyte casts occur in hypertension, anaemia, renal stones, urinary tract infection etc.
Epithelial casts show inflammation and degeneration of kidney
Crystal formation occurs in the urine when it gets supersaturated with the solutes. It can produce uroliathiasis: for example – stone formation from increased excretion of uric acid which may sediment and form crystals or stones. Likewise are the cystines and oxalates.
Round, brick red/orange sediment in the urine of children indicates Xanthine.
Pink or yellow colour crystals – cystines
Smooth and chalky – phosphates
Dark brown – oxalates
Red urine – The high intake of beetroot usually resemble blood in the urine;
another factor which can mimic bloody urine is dyes and chemicals used in sweets. In diseased conditions, bloody urine (Haematuria) may occur due to infection or stones in kidney or bladder or ureter or urethra or due to infection of the prostate. Everyone should be ever careful if blood cells are present during urination since it indicates that the condition is serious. Most of the time, it is passed as microscopic haematuria (i.e. blood in the urine may not be visualised normally). But sometimes, in case of massive bleeding, urine appears as bloody or pinkish or smoky or deep brown, alarming the person. Even though we might pass 1-3 RBCs (red blood cells), elevated levels will usually indicate internal diseases or complications. The RBCs occur in the urine in abnormal conditions like kidney stones, cancer of the kidney or bladder or prostate, heavy urinary tract infection, sickle cell anaemia, etc.
Gravindex test for pregnancy – following a missed period, even within a week or so, pregnancy can be confirmed by detecting the presence of HCG (human chorionic gonadotrophin) in the urine. This lab test is now simplified by colour card test where everyone can use to test urine for pregnancy at home itself.
Even though urinalysis indicates a problem, finally to evaluate and analyse the effects and complication of the disease imaging studies like ultrasound scan, IVP, CT scan and MRI may be necessary to confirm and proceed to the treatment.
Dr. S. Chidambaranathan, BHMS, MD (Homeo)
24 E. New Mahalipatti Road
Tel: +91-452-233-8833 | +91-984-319-1011 (Mob)
(Disclaimer - The contents of this column are for informational purpose only. The content is not intended to be a substitute for professional healthcare advice, diagnosis, or treatment. Always seek the advice of healthcare professional for any health problem or medical condition.)