Overview
Urine pH is a measure of the acid content in urine. This often reflects the acidity of serum, however there are certain cases (e.g. renal tubular acidosis) in which the urine pH does not match the serum pH.
Normal Range
4.5 - 8.0
Aciduria
A reduction in urine pH suggests an abundance of acid in the urine. This may be due to an excess of endogenous or exogenous acid, or non-renal loss of base (e.g. diarrhoea).
Causes of Aciduria
- Dietary - high protein diet, acidic foods (e.g. cranberries)
- Metabolic acidosis - e.g. lactic acidosis, ketoacidosis, uraemia, diarrhoea
- Respiratory acidosis - hypoventilation, emphysema
Alkaluria
An increase in the urine pH suggests an abundance of base in the urine.
This is commonly a sign of infection with a urease-producing bacteria, which convert urea into the alkaline ammonia. Such urinary alkalinisation can result in the formation of struvite stones.
Causes of Alkaluria
- Dietary - low carbohydrate diet
- Urea-splitting bacteria - Proteus, Klebsiella, Pseudomonas, coagulase negative Staphylococcus
- Metabolic alkalosis - alkaline ingestion, massive transfusion, dialysis, vomiting, diuretics, Cushing's, Conn's,
- Respiratory alkalosis - hyperventilation
- Renal tubular acidosis
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