Physical Examination of Urine

Physical Examination of Urine

Physical examination includes examination of volume, color, odour, specific gravity and pH of the urine.

1. Volume

Normal average volume - 1.5 litre/day(600-2500ml/day)

Polyuria: Implies an increased volume of urine (>2500ml/day). It is commonly observed in

a. Diabetes mellitus

b. Diabetes insipidus

c. Medication like diuretics

d. Chronic renal disease

Oliguria: Implies decreased urinary output (<500ml/day). It is commonly observed in

a. Sweating, diarrhea, vomiting. (Excessive loss of fluid through extra renal channels)

b. Hemorrhage, dehydration and in shock (Reduced blood supply to kidneys)

c. Acute glomerulonephritis, incompatible blood transfusion, heavy metal poisoning.

Anuria: Implies complete suppression of urine (<100ml/day). It is commonly seen in

a. Acute tubular necrosis (ATN)

b. Acute kidney injury (AKI)

c. Crush injury

Nocturia: Implies excretion of >500 ml / night. 

2. Color: Normal urine is clear/ pale yellow or straw coloured due to presence of urochrome, the chief urinary pigment and small amounts of urobilins and uroerythrin.

Abnormal colors:

a. Colorless- after ingestion of large amounts of water/fluid, polyuria in diabetes mellitus and diabetes insipidus

b. Deep amber-after exercise, high grade fever

c. Deep yellow-Jaundice

d. Red/pink-due to the presence of blood as in hemoglobinuria, haematuria - this may be 

caused by urinary tract infections, malignancy or Injury to urinary tract, mismatched 

blood transfusion.

e. Milky-due to presence of chyle, fat or pus.

f. Smoky/ smoky brown – due to presence of blood along with protein/albumin as found 

in acute nephritis.

g. Green-phenol poisoning

h. Orange-medication like rifampicin, concentrated urine

i. Turbid- Due to the presence of large number of pus cells (pyuria) or due to large amount 

of amorphous phosphate crystals (phosphaturia)

3. Appearance: Normal urine is usually clear when passed fresh, but sometimes phosphates may produce turbidity in fresh urine. 

Causes of turbidity: 

a. Urine may become turbid on standing due to presence of mucus or due to the formation of amorphous or crystalline deposits or bacterial growth. 

b. Infections of bladder, prostate, urethra are sometimes associated with increased secretion of mucus which causes urinary turbidity. 

c. Pathological causes of turbidity of urine include presence of WBC, RBC, epithelial cells or bacteria which are identified by microscopy.

d. Chyluria  and lipiduria also causes turbidity of urine.

4. Odour: Normal fresh urine has either no smell or has some characteristic aromatic odor due to the presence of volatile fatty acids.

Abnormal odours and their causes include:

a. Ammoniacal / fetid odour -Extensive bacterial overgrowth

b. Fruity odour – Ketosis

c. Mousy odour- Phenylketonuria

d. Maple syrup odour -Maple syrup urine diseases

e. Cabbage odour -Methionine malabsorption

f. Fishy odour –Trimethylaminuria

g. Rancid odour -Tyrosinaemia 

5. Reaction of urine / pH:

pH is an indication of the hydrogen concentration of the blood.  

The ph of urine varies from 4.6 – 8.0 ( average-6.0) and is usually slightly acidic.

The reaction of urine is determined with the help of litmus paper/ pH meter or pH paper.  Alkaline urine turns red litmus paper blue and acidic urine turns blue litmus paper red. 

Causes of highly acidic urine:

 a. Protein rich diet/ ingestion of acidic foods

b. Urinary tract infection by E.coli

c. Uremia

d. Respiratory and metabolic acidosis

e. Febrile illness

f. Ketonuria 

g. Leukemia.

Causes of alkaline urine:

a. After a diet high in vegetables and citrus fruits. 

b. UTI with proteus and pseudomonas

c. Respiratory alkalosis and metabolic alkalosis

d. When specimen is allowed to stand at room temperature it becomes alkaline because of bacterial contamination/ infection with urea fermenting organisms or decomposition with formation of ammonia.

6. Specific gravity: Indicates relative proportions of dissolved solid component to total volume of the specimen. It is the ratio of the weight of a volume of urine to the weight of the same volume of distilled water. It is measured with an urinometer, which works on the principle of buoyancy. It can also be measured with a refractometer, using a specific gravity reagent stripor by falling drop method .

Average normal specific gravity is 1.003 to 1.030

Hyposthenuria - urine with lowered specific gravity. The causes include

a. Diabetes insipidus

b. Diuretic therapy

c. Parenteral infusion of fluids

d. Chronic nephritis

Hypersthenuria – urine with high specific gravity. The causes include

a. Nephrotic syndrome

b. Diabetes mellitus

c. Acute renal failure

d. Dehydration

Isosthenuria – refers to fixed specific gravity (0.010) and indicates a poor tubular reabsorption, failure of concentrating power of renal tubules and ADH deficiency. It is found in 

a. ADH deficiency

b. End stage kidney

c. Arteriosclerotic kidney

The urinometer consists of a glass tube. It has a thin calibrated stem at the upper side and the  lower end which expands suddenly  contains a heavy bulb. The scale in the urinometer reads from 1.000-1.060 (below upwards) and it is calibrated at a specific temperature (200C). As the specific gravity varies with temperature, the reading obtained should be corrected to the room temperature by applying temperature correction To correct for the room temperature, 0.001 is added for every 3°C above and 0.001 is deducted for every 3°C below the temperature at which the urinometer is calibrated.

Procedure: 

a. Urinometer container ( a wide mouthed deep cylinder or urine jar) is filled upto three fourths of its volume with urine

b. The urinometer is floated in the container with a gentle twist, taking care that there should be no froth and it should not touch the sides of the vessel. 

c. The specific gravity is read from a graduation which lies in level with the true surface of urine.

When, only small volumes of sample are available for measurement of specific gravity, urine may be diluted with its equal (1volume) or double (2volume) volumes of distilled water and the last 2 figures of observed values multiplied by 2 when diluted with equal vol. and by 3 when diluted with double vol. to obtain the correct value for undiluted urine.