Types of turbidities

1.Urates: ammonium urate may precipitate, from alkaline urine whereas other urates are found only in acid urines. Ammonium urates dissolve on acidification, whereas other urates on warming.

2. Phosphates: calcium PO4 and NH4-Mg-PO4 (or so called Triple phosphates) are found only in alkaline urine or they may form a cloudy precipitate from an alkaline urine on warming. They dissolve on acidification.

Note:

(i) it is essential that a urine sample is slightly acidified, when making a test for heat-coagulable proteins.

(ii) Furthermore, the iso-electric points (pI) of most proteins that may appear in urine are slightly acidic.

3. Cellular deposits: a sediment in urine that may account for turbidity and does not dissolve on adding acid or on heating is most likely made up of cellular matter, “organised deposit” eg. Pus cells leukocytes, R.B. Cells, epithelial cells or microorganisms etc.

INORGANIC CONSTITUENTS

I. Chlorides

Normal value: next to urea, clorides make up the chief solid constituents of urine, generally amounting to 6.0 to 9.0gm per day of Cl, and equivalent to 10-15gms of NaCl, which is the predominant chloride present. However, the daily excrtetion varies with the dietary intake.

Clinical significance

(a) Decrease of urinary chlorides:

1. Markedly decreased by excessive sweating by loss of chlorides in sweat.

2. During fasting, chloride excretion may fall to a trace, even though the concentration of blood chlorides is approximately normal. This shows the remarkable capacity of the kidneys to conserve electrolytes for the maintenance of the osmotic pressure of the body fluids.

3. Excretion of chlorides in urine is also decreased, when blood chlorides levels are lowered by loss through diarrohoea and excessive vomiting.

4. Oedema – patients with oedema from practically any cause (nephrotic syndrome, nephritis, malnutration, or cardiac decompensation) show decreased urine chlorides rather independent of blood chlorides concentration.

5. Diabetes insipidus – urine chlorides may be extremely low in cases of severe D.insipidus.

6. Infections – during pneumonia and other infectious diseases, hypochloraemia, results from the withdrawal of blood chlorides into exudates, and the excretion of chlorides in urine falls. Upon resolution of exudates, excretion of chlorides increases.

7. Urinary excretion of chlorides is decreased in Adrenocortical hyperfunction (Cushing’s syndrome).

(b) Increase of urinary chlorides