Urine Normal Composition

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Introduction

The testing and evaluation of urine composition is an essential diagnostic indicator for many diseases. It is therefore essential to have an understanding of what is the normal composition of urine.

More information can be found at urine analysis on the WikiPath section of the website.

Normal Urine Volume

Below are the normal urine volumes for the common domestic species. The units are ml/kg/day

Species
Urine Volume
Dog
20-100
Cat
10-20
Cow
17-45
Sheep
10-40
Horse
3-18
Pig
5-30

The Normal Appearance of Urine

Several pathological conditions can cause macroscopic changes to the urine. It is therefore essential to appreciate the normal appearance of urine. In many of the exotic species the urine has a very differant appearance and therefore use care when applying this to those species.

Colour

In the majority of the domestic species the urine should be yellow in colour. The colour of the urine is very dependant on the urine specific gravity so it is important to account for this. If the urine is more concentrated it will be darker in colour and visa versa as a general rule . Equine urine can become brown if left standing. Discoloured urine should be taken into consideration when carrying out tests which involve a colour change such as dipsticks. The abnormal urine colour could affect the result.

Turbidity

If the urine is not clear then this could indicate a variety of pathological states. In the horse it is normal for it to be turbid due the mucous secreted in the renal pelvis and proximal ureters.

Odour

It is normal for urine to have a slight odour from the ammonia. The odour increases with concentration and in some species such as the cat a pungent urine is normal. However a strong smelling urine could indicate a pathological state

Urine Specific Gravity

Urine specific gravity is measured using a refractometer calibrated for veterinary use.

Specific gravity relates to the concentration. It is basically a measure of the density of particles in the urine.

Below are the normal urine specific gravities for the common domestic species.

Species
Urine Volume
Dog
1.016-1.040
Cat
1.020-1.060
Cow
1.030-1.045
Sheep
1.015-1.045
Horse
1.025-1.060
Pig
1.010-1.050

Urine Chemistry

The following are common chemicals or parameters whose levels in urine change in pathological vs normal conditions. It is therefore important to appreciate their normal levels

pH

In dogs and cats an acidc pH is normal. In the ruminants and horses the opposite is true and the urine is alkali. The pH does however vary with diet and medications as well as in pathological states so this needs to be accounted for. The normal range is 5-9

Protein

It is not common to find protein in the urine of normal animals. However it can be normal for small amounts to be found in the urine of dogs with a high specific gravity. Therefore this needs to be taken into account.

Glucose

The presence of glucose in the urine is termed glucosuria and occurs when the level of glucose reaches the renal threshold for glucose reabsorption. It is not normal to find glucose in the urine.

Ketones

It is not normal for ketones to be present in the urine and they are indicative of pathological states

Bilirubin and Urobilinogen

Small amounts of bilirubin can be found in dogs with concentrated urine therefore this needs to be interpreted in light of the urine specific gravity. However as a rule it is not normal to find bilirubin in urine.

Urobilinogen is formed from bilirubin in the intestine and small quantities are normally found in the urine.

Blood

The presence of blood in the urine is not normal and is usually related to a pathological state.

Microscopic Examination of Urine

Uroliths and casts can be seem on microscopic examination. Neither of these are a normal finding. The levels of bacteria that seen are very dependent on how sterile the procedure of urine collection has been, which part of the urinary tract the urine has been collected from and if an infection is present.

References

Text adapted from the Merck Veterinary Manual online reference table entitled Urine Volume and Specific Gravity


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