<prompt> A patient of Chronic Kidney disease is having protracted vomiting. ABG repo is pH 7.4, pCO2 40 mm Hg, HCO3 25 meq, Na 145 meq and Chloride s 100 meq. Diagnosis is?Normal anion gap metabolic acidosisHigh anion gap metabolic acidosisNo acid base abnormalityHigh anion gap metabolic acidosis and metabolic alkalosis  <response>: CKD leads to metabolic acidosis while vomiting leads to metabolic alkalosis. The key to the answer is anion gap which is elevated to 25 implying unmeasured anions. Normal average of 10 meq. It points to mixed etiology of metabolic acidosis and alkalosis. Normal values of pH, pCO2 and HCO3 does not ensure absence of acid base imbalance. 