In This Article
- Advantages over urinalysis
- Testing a Urine Sample
- Abnormal findings
- Finishing off
- 24 hour urine sampling
- Example of a Urine Dipstick chart
Advantages over urinalysis
- No risk of infection
- Not precise
You should only perform it after a full history and thorough examination!
- Diabetes Mellitus – polydipsia, polyuria, weight loss, fatigue, infection, DKA
- UTI – dysuria, frequency, back pain, haematuria
- Pregnancy – for monitoring purposes; pre-eclampsia
- Renal and CVD – hypertension, oedema, suspected heart failure
- Drugs – gold, penicillamine, recreational
- Others – anxiety, hysterical polydipsia
Mid-stream sample – means that the urine is not-contaminated from any bacteria on the skin
Men – retract the foreskin, clean the glans penis with a swab. Start to pass urine, and pass the first part into the toilet, then, without stopping the flow, catch some of the middle of the sample in a bottle. Once the bottle is full to the line, then you can continue to pass urine into the toilet
Women – hold back the labia, and clean the vulva with a sterile swab. Start to pass urine, and pass the first part into the toilet, then, without stopping the flow, catch some of the middle of the sample in a bottle. Once the bottle is full to the line, then you can continue to pass urine into the toilet
- Don’t open the bottle until you are ready to take the sample.
- The amount of urine is not that important. Tell patients they don’t have to completely fill the bottle!
- The sample should be tested within 2 hours. If this is not possible, you may be able to preserve the sample to some extent by keeping in the fridge
Testing a Urine Sample
- Wash hands, put on gloves
- Look at the bottle – check it is the right patient and the right date. You also want to know if it was taken in the last 2 hours – a crude way to know if it is recent is to see if it is warm!
- Look in the bottle – are there any precipitations?
- Does it look a normal colour?
- Normal – straw yellow
- Dark – bile pigments may be present due to dehydration
- Red – haematuria, menstrual blood?, food; e.g. beetroot and blackberries
- Green/blue – Pseudomonal UTI, triamterene (this is a potassium sparing diuretic), asparagus
- Orange – dehydration (bile pigments), phenothiazines, carrots
- Clarity – how clear is the sample?
- Cloudy – can be normal (especially in males), may also be bacterial infection (check the smell), WBC, lipids
- Frothy – this suggests proteinurea
- Is there anything in there that shouldn’t be in there?
- Make sure you keep the bottle on the tray, or trolley that it is given to you on! – e.g. in OSCE’s don’t lift it up and put it on the table!
4) Open it and have a smell
- Ketones – smell like nail polish remover – diabetes
- Sweet smelling –remember the renal threshold – some people naturally excrete glucose in their urine. Other wise could be a sign of DM
- Foul smelling – bacterial infection, GI-bladder fistula
Check your dipsticks:
- Are they in-date?
- Check silica gel crystals are present in the container to ensure the sticks have been kept dry
- Dip it – stick the stick all the way in, no need to leave it in for very long. Shake off the excess, and perhaps dab it on a paper towel.
- Wait the desired amount of time and note down the results! Hold the dipstick parallel to the ends of the tube, not to the length of the tube. The times down the side of the bottle are the time from 0, not the time between each result.
- Check normal values – see if there are any irregularities – remember nitrites show infection!
- Say what irregularities are present, and what would you do to test them furthur
Put the lid back on, put the sample back. Take gloves off (yellow bin) and wash your hands.
- Contamination from menstrual bleeding ≪ this is THE most common cause of ‘haematuria’!
- Recent trauma
- Recent prostate exam
- Recent urological examination (e.g. cystoscopy)
- Glomerular or tubular pathology
- Urologic pathology – this present with haematuria without proteinuria
- Exercise induced – long distance runner. Result will be negative if repeated after 72 hours with no further exercise
- Dipstick test is 90% sensitive, but less specific. However, only 0.5-6% of patient have significant underlying pathology
- Healthy adults excrete 80-120mg protein / day. This can be up to 1g per day.This usually occurs at night. This is generally too small to be detected on dipstick. The dipstick can detect 20-30mg / dl.
- Proteinuria above normal levels on a urine dipstick may indicate; renovascular, glomerular or tubular interstitial renal disease, or it can be a sign of diseases that cause overproduction of urine, such as myeloma.
- False negatives can occur when there is very diluted urine and / or when the primary protein is not albumin. They can also occur in very alkaline conditions.
- Transient proteinuria – in young patients this is usually not a problem, and resolves within a few days, or after >8 hours lying down. In older patients it may be a sign of congestive heart failure.
- Intermittent proteinuria – can be present in young adults as a result of prolonged vertical posture, exposure to cold, pregnancy and hypertension. This usually produces about 1g of protein per day. This is asymptomatic, and should only ever be treated in renal problems are detected.
- Persistent – due to underlying disease, most commonly; glomerular. This often produces in excess of 2g protein per day. Can also be due to overflow proteinuria (myeloma), connective tissue disorders, DM, hypertension.
- Pre-eclampsia - a condition in pregnant women characterised by hypertension and proteinuria.
- Small amounts of urine are naturally excreted. The actual amount varies with the renal threshold from patient to patient. Generally these levels are too small to be detected on dipstick.
- Can be caused by diabetes, Cushing’s syndrome, liver and pancreatic disease, Fanconi’s syndrome
Bilirubin and urobilogen
- Normal urine contains no bilirubin, and very little urobilogen
- Conjugated bilirubin may appear in the urine in the presence of liver disease, or bile duct obstruction.
- This test has lower accuracy than for nitrites, and thus testing for nitrites is seen as a better test. However, if present, they likely indicate a UTI
- should be between 4.5 and 5.3
- A metabolic acidosis and alkaloid urine suggests a renal tubular acidosis. These patients have a risk of stone formation and nephrocalcinosis
- Acidic urine can be caused by diet and uric acid calculi
- Note that stale urine can become alkaline – thus you should check if the urine has been left fro any period of time
- These re produced by bacteria; and thus raised levels indicate UTI. Accuracy may be affected in symptomatic patients, and patients on antibiotics.
- This shows the concentration of solutes in the urine; and is thus a measure of the ability of the kidneys to concentrate fluids.
- If the value is high:
- Renal artery stenosis
- If the value is low
- Excess fluid intake
- Renal failure
- Diabetes insipidus
Say you would do the following:
- If anything suspicious to a FBC and U+E’s
- If glucose is present; do a random/fasting blood glucose, or a glucose tolerance test. Refere onto diabetes specialist.
- If protein is present; rule out benign causes (e.g. the postural cause, you could do an early morning urine sample, or you could to a 24hr glucose monitoring. Refer to renal specialist
- If blood is present; send the urine sample to microscopy, refer to renal/oncology/urology
- Bacteria; send for microbiology, culture and sensitivity, and if symptoms present, then start on broad spectrum antibiotics.
24 hour urine sampling
- Volume - water overload / depletion
- total protein excretion – glomerular function
- creatinine clearance – renal function
- Cortisol – Cushings
- Na/K – renal failure, aldosteronism / Conn’s syndrome
- Catecholamines - phenochromocytoma
- Pick a start time, e.g. 9am. The patient should completely empty their bladder before they start
- After this time, they should collect all their urine. They are often given two containers; a small one to urinate in and a larger one to collect it all in
- If possible, urine should be kept refrigerated
- at the end of the 24hrs, the patient should urinate and collect it one last time, before taking the sample for analysis as soon as possible
- Volume – normal production is about a minimum of 30ml/hour. In a 24 hour period you should be worried if the total volume is less than 500-600ml (technically 720ml/day is normal ‘minimum’)
- <2.0g – may indicate tubulointerstitial problems
- 2.0-3.0g – this is considered in the normal range
- >3.0g – may indicate nephrotic syndrome
Example of a Urine Dipstick chart