Proximal (type 2) renal tubular acidosis (RTA) is marked by reduced proximal bicarbonate reabsorption and urinary bicarbonate wasting. This may lead to an isolated non-anion gap metabolic acidosis or may occur in conjunction with other tubular defects leading to hypophosphatemia, glucosuria with normal plasma glucose concentration, hypouricemia, and/or aminoaciduria with generalized proximal dysfunction (Fanconi syndrome).
Major causes of proximal RTA in adults include increased excretion of immunoglobulins in the setting of monoclonal gammopathies and use of carbonic anhydrase inhibitors (eg, acetazolamide, and topiramate or ifosfamide). In children, proximal RTA may be caused by an autosomal recessive mutation in the gene for the sodium bicarbonate transporter (SLC4A4) or ifosfamide use, although in many cases, no cause is identified.
Related topic: Distal renal tubular acidosis
Proximal renal tubular acidosis
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Synopsis
Codes
ICD10CM:
N25.89 – Other disorders resulting from impaired renal tubular function
SNOMEDCT:
24790002 – Proximal renal tubular acidosis
N25.89 – Other disorders resulting from impaired renal tubular function
SNOMEDCT:
24790002 – Proximal renal tubular acidosis
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Diagnostic Pearls
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Differential Diagnosis & Pitfalls
- Distal renal tubular acidosis
- Chronic diarrhea – In this case, the urine anion pH should be appropriately low, and urine anion gap should be negative.
- Diarrhea
- Ureterosigmoid fistula
- Addison disease
- Small bowel fistula
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Therapy
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Drug Reaction Data
Below is a list of drugs with literature evidence indicating an adverse association with this diagnosis. The list is continually updated through ongoing research and new medication approvals. Click on Citations to sort by number of citations or click on Medication to sort the medications alphabetically.
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References
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Last Reviewed:03/06/2018
Last Updated:01/23/2022
Last Updated:01/23/2022