From the Guidelines
Non-anion gap metabolic acidosis is primarily caused by either excessive loss of bicarbonate or excessive retention of chloride, with common causes including gastrointestinal bicarbonate loss, renal bicarbonate wasting, and medication-induced causes. The causes of non-anion gap metabolic acidosis can be multifaceted, involving various mechanisms that lead to an imbalance in the body's acid-base homeostasis. Some of the key causes include:
- Gastrointestinal bicarbonate loss through conditions such as diarrhea, pancreatic fistulas, or small bowel drainage
- Renal bicarbonate wasting, which can occur in renal tubular acidosis (RTA), including Type 1 (distal) RTA, Type 2 (proximal) RTA, and Type 4 RTA
- Medication-induced causes, such as the use of carbonic anhydrase inhibitors like acetazolamide, which increase bicarbonate excretion, and potassium-sparing diuretics such as spironolactone
- Dilutional acidosis, which can occur with the rapid infusion of chloride-rich fluids like normal saline, as noted in patients recovering from DKA 1
- Hyperalimentation with amino acid solutions, which can contribute to non-anion gap metabolic acidosis as amino acids are metabolized to strong acids
- Recovery from ketoacidosis, which may temporarily present as a non-anion gap acidosis as ketones are cleared faster than bicarbonate is regenerated, as seen in the management of diabetic ketoacidosis (DKA) 1 Identifying the specific cause of non-anion gap metabolic acidosis is crucial for appropriate management, which typically involves addressing the underlying condition and sometimes providing bicarbonate supplementation.
From the Research
Causes of Non-Anion Gap Metabolic Acidosis
- Gastrointestinal bicarbonate loss, such as diarrhea 2, 3
- Renal tubular acidosis, including distal renal tubular acidosis (dRTA) 4, 3
- Ileal neobladder urinary diversion for the treatment of bladder cancer 5
- High-volume ileostomy output causing large bicarbonate losses 6
- Administration of large quantities of chloride-containing solutions in the treatment of hypovolemia and various shock states 2
- Chronic laxative abuse, which can mimic dRTA and result in non-anion gap metabolic acidosis 4
- Drugs-induced hyperkalemia and early renal failure 3
- Loss of bicarbonate from the kidney or gastrointestinal tract 3