Figure 1 Identification and quantitation of l‐2‐hydroxyglutaric acid (HG) in canine urine. (A) Total ion chromatogram following organic acid extraction demonstrating accumulation of 2‐HG in an affected dog. Control dogs demonstrated minimal or no detectable 2‐HG. Stable‐isotope‐dilution gas chromatography‐mass spectrometry of an affected dog (B) and control dog (C), with the ratio of the l‐2‐HG versus d‐2‐HG expressed as a ratio relative to an internal standard. Marked increase of l‐2‐HG is evident in the affected dog.