American journal of kidney diseases : the official journal of the National Kidney Foundation
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Case Reports
The urine pH: a potentially misleading diagnostic test in patients with hyperchloremic metabolic acidosis.
The purpose of this case report is to illustrate that the urine pH may be a misleading index in the assessment of the normal renal response to metabolic acidosis. On presentation, the patient had a normal anion-gap type of metabolic acidosis; the cause of the acidosis was gastrointestinal bicarbonate loss. ⋯ However, since the kidneys generated more than 190 mmol of bicarbonate per day (urine ammonium was 190 mmol/d), reduced renal acid excretion was not the cause of the acidosis. Therefore, the urine pH of 6.0 provided a false clue with respect to a renal cause for the acidosis in this setting; in contrast, the urine anion gap provides more reliable information concerning bicarbonate generation by the kidney.