View source for Non anion gap acidosis

==Background==
*Non-anion gap metabolic acidosis (NAGMA) = metabolic acidosis with a normal anion gap (typically 8-12)
*Caused by loss of bicarbonate (GI or renal) or addition of chloride (hyperchloremic acidosis)
*Mnemonic: HARDUPS — Hyperalimentation, Acetazolamide, RTA, Diarrhea, Ureteral diversion, Pancreatic fistula, Saline infusion
*Distinguish from anion gap metabolic acidosis (AGMA) which has a different differential

==Clinical Features==
*Symptoms of underlying cause (diarrhea, polyuria)
*Kussmaul breathing (compensatory hyperventilation)
*May be asymptomatic if mild

==Differential Diagnosis==
{{Non anion gap acidosis}}

===GI Bicarbonate Loss===
*Diarrhea (most common cause)
*Pancreatic fistula or drainage
*Ureteral diversion (ileal conduit, ureterosigmoidostomy)
*Cholestyramine

===Renal Bicarbonate Loss / Impaired Acid Excretion===
*Renal tubular acidosis (RTA)
**Type 1 (distal): impaired H+ secretion, urine pH >5.5, hypokalemia
**Type 2 (proximal): impaired HCO3 reabsorption, urine pH <5.5 after bicarb depleted
**Type 4 (hypoaldosteronism): hyperkalemia, urine pH <5.5
*Early renal failure
*Carbonic anhydrase inhibitors ([[acetazolamide]], [[topiramate]])

===Iatrogenic===
*Excessive normal saline infusion (dilutional/hyperchloremic)
*Hyperalimentation (TPN)

==Evaluation==
*[[BMP]]: calculate anion gap (Na - Cl - HCO3), check potassium
*Urine anion gap (Na + K - Cl) helps distinguish GI from renal cause:
**Negative urine AG = GI loss (kidneys appropriately excreting NH4+)
**Positive urine AG = renal cause (RTA — kidneys cannot excrete acid)
*Urine pH: >5.5 suggests Type 1 RTA
*Serum potassium: low (Type 1, 2 RTA, diarrhea), high (Type 4 RTA)
*Urine electrolytes

==Management==
*Treat underlying cause (e.g., volume replacement for diarrhea)
*Sodium bicarbonate for severe acidosis (pH <7.1) or symptomatic
*Correct potassium abnormalities
*Stop offending medications (acetazolamide, excessive NS)
*Type 4 RTA: treat hyperkalemia, consider fludrocortisone

==Disposition==
*Admit if severe acidosis, hemodynamically unstable, or significant electrolyte derangement
*Discharge if mild, correctable cause identified, and electrolytes stable

==See Also==
*[[Metabolic acidosis]]
*[[Anion gap metabolic acidosis]]
*[[Hyperkalemia]]
*[[Acid-Base Disorders]]

==References==
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[[Category:FEN]]
[[Category:Renal]]