Appendix A Abnormalities of urine Urine testing by the use of observation and dipstick tests is a procedure carried out on an almost daily basis by nursing staff. Since this procedure is frequently used as a primary screening technique it is important that nurses have a knowledge of the meaning of the test results and what constitute abnormal readings. Correct interpretation and reporting of the results may not only lead to an earlier diagnosis and hence treat­ ment for the patient but also to a financial saving, since it may obviate the need for further analysis of the urine in the laboratory. Observation of the urine is a comparatively straight­ forward but nonetheless important activity. The exact nature and the range of substances which can be detected using test strips vary from manufacturer to manufacturer and this section will give an outline of the substances most commonly tested for, and how their presence in urine may be interpreted. It is important to stress that accurate testing using this method relies on following the manufacturers' instructions particularly in relation to reading the results at specific times which may be necessary for quantitative analysis . Fresh urine should always be used for the test. OBSERVATION OF THE URINE Colour The colour of normal urine varies between a very light yellow to a dark amber. Normally this is dependent on the concen­ tration of the urine and diet. Certain diseases mayaiso have an effect on this. Consistently light coloured urine may be the result of excessive urine production, as would occur in diabetes mellitus and diabetes insipidus, whereas production of very Observation of the urine 161 dark urine may be indicative of some form of hepatic or biliary disease and the presence of large amounts of urobilinogen. The other commonest form of urinary discoloration is that caused by the presence of blood which may present as frank blood or, more frequently, as a mild pink discoloration. Drug therapy, dyes used in radiological examination and diet should all be considered as potential causes of abnormal urinary discolora­ tion and exduded prior to considering any more sinister causes . Turbidity and the presence of casts Normally urine is dear and transparent in appearance. At times it may appear doudy as a result of the precipitation of phosphates and carbonates which become insoluble in alkaline urine. This cause of doudiness, which does not constitute an abnormality, can be exduded by acidifying the urine (normally done by the addition of acetic acid) which should cause the urine to become dear. The main cause of abnormal urinary turbidity is the presence of pus cells resulting from infection. Urinary casts are also responsible for causing turbidity. These consist of cells and cellular debris from the distal collecting tubules. They are indicative of inflammatory or degenerative changes in the tubules. The presence of dearly visible strings or specks of matter in the urine is often indicative of infection, but may in some cases be the result of contamination of the specimen with other secretions produced by the genitourinary tract. This is most common in men where there may be residual seminal fluid in the urinary tract which is excreted on urination. Odour It is difficult to define exactly what constitutes an abnormal or offensive odour. The smell of urine can be affected by a large number of factors, most related to concentration and diet. If left standing all urine will begin to smell ammoniacal as the result of bacterial action. This smell should not be present in freshly voided urine and could be indicative of infection. Foul smelling urine is almost always indicative of infection and is also comparatively easy to recognize. Again diet and drug therapy should be considered as possible sources of 'abnormal' odours from urine. 162 Appendix A Abnormalities 0/ urine Specific gravity (S.G.) This is determined by the relative proportions of dissolved solids in the urine and is therefore extremely variable since it is dependent on the concentration of the urine which is being produced. Single measurements of S.G. are, therefore, com­ paratively meaningless and it is only when there is a consistent deviation from the normal range (1.010-1.025) that underlying pathology should be considered. A consistently low S.G. means that there is either an exces­ sively large volume of urine being produced by the kidneys as occurs in diabetes insipidus and, it must be remembered, in patients undergoing diuretic therapy, or as a result of diseases such as glomerulonephritis where the ability of the kidney to concentrate urine is impaired. A consistently high S.G. may result from uncontrolled dia­ betes mellitus where there is a high proportion of sugar dis­ solved in the urine, or in conditions such as congestive cardiac failure which lead to oliguria and fluid retention. It is also indicative of chronic dehydration. If the S.G. remains unchanged it may still be indicative of impaired renal function, since it suggests that the kidney is unable either to dilute or concentrate the urine. pH This again is a very variable measurement because of the role of the kidneys in regulating blood pH which results in any changes being reflected in the urinary pH. Normal values range between 4.8-8.5 although readings outside this range are not necessarily indicative of any particular pathology. In general terms a consistently low pH may be associated with starvation, dehydration and diabetes mellitus, whilst a consistently high pH will accompany urinary tract infection. ABNORMAL URlNARY CONSTITUENTS Leukocytes These will be found in the urine of patients who are suffer­ ing from inflammatory conditions of the urinary tract such as Abnormal urinary constituents 163 cystitis and urethritis and may or may not be accompanied by bacteriuria. In the absence of bacteriuria other causes should be investigated since the presence of leukocytes can always be considered to be abnormal. In women particular care must be taken to ensure that the specimen has not been contaminated by vaginal secretions which will lead to a false positive reading. Nitrites The presence of nitrites in the urine can be detected by some of the test sticks available on the market. This is a particularly useful test since a positive result is indicative of bacterial activity in the urine and hence urinary tract infection. An early morning urine specimen is the ideal sampIe for this test but failing this urine which has been in the bladder for at least four hours may be used. Protein The presence of protein in the urine can always be considered to be abnormal, although it may result from non-pathological sources. These include orthostatic proteinuria and proteinuria following physical exertion. The commonest pathological cause is upper urinary tract infection. Glucose Classically the presence of glucose in the urine is considered to be indicative of diabetes mellitus and is frequently the first indi­ cation which is given of the condition when routine urinalysis is performed. There are, however, various other causes and glucose may be found in the urine following a meal particularly rich in carbohydrates, during pregnancy, in those with a low renal threshold for glucose and in certain individuals with renal damage. Ketones Ketones, or ketone bodies as they are sometimes referred to, are produced as a result of fat metabolism. This occurs primarily in two situations. The first is when there is insufficient glucose 164 Appendix A Abnormalities of urine within the body to provide the energy required for normal metabolie processes to take place. Starvation, weight reducing diets and cases of severe vomiting will cause this . In the absence of any of these ketonuria is indicative of a disturbed glucose metabolism as occurs in diabetes mellitus. The presence of ketones in this group of patients should always be treated as significant, particularly if glucose is also present, since high levels of ketones in the blood lead to ketoacidosis, coma and the potential for central nervous system damage. Urobilinogen This is produced from bilirubin in the gut as a result of bac­ terial action. Under normal circumstances aIl urobilinogen that is produced is reabsorbed and broken down by the liver. If excessive urobilinogen is produced as occurs in the case of increased haemolysis, infection of the biliary tract and certain gastrointestinal conditions (e.g. severe constipation leading to a much decreased transit time) the liver may be unable to metabolize the higher blood levels and it is then excreted in the urine. The other situation in which this can occur is acute or chronic inflammation of the liver resulting from infection or other conditions such as cirrhosis or carcinoma. Bilirubin This is an abnormal constituent of urine and is only found in cases where the serum bilirubin levels are grossly elevated. This can occur in cases of acute and chronic hepatitis, cirrhosis and biliary obstruction. It is not present in cases of prehepatic jaundice. Blood The majority of test strips now available differentiate between haematuria, the presence of intact red blood ceIls, and haemo­ globinuria, the presence of free haemoglobin resulting from the breakdown of red blood ceIls. Haematuria can be further divided into gross haematuria, where the urine is discoloured by the presence of blood, and microhaematuria, where the urine appears normal but red blood ceIls can be detected by Abnormal urinary constituents 165 microscopy or chemical tests . Haematuria may be indicative of a number of conditions including the following: • urinary tract infection • trauma • renal or bladder calculi • tumours of the urinary tract • glomerulo- and pyelonephritis • hypertension. The presence of haemoglobinuria may be the result of severe haemolytic anaemias, poisoning, bums, systemic infections and physical exertion. In some circumstances both haematuria and haemoglobinuria may be detected.