Table 2

Differential diagnosis for metabolic acidosis (decreased SID)

Renal tubular acidosis:
Nonrenal:
urine SID (Na+ + K+ – Cl) > 0
urine SID (Na+ + K+ – Cl-) < 0

Distal (type I): urine pH >5.5
Gastrointestinal: diarrhea, small

bowel/pancreatic drainage
Proximal (type II): urine

pH <5.5/low serum K+
Iatrogenic: parenteral nutrition,

saline, anion exchange resins
Aldosterone deficiency (type IV):

urine pH <5.5/high serum K+


SID, strong ion difference.

Kellum Critical Care 2000 4:6   doi:10.1186/cc644