<prompt> Normal anion gap is seen in all exceptUreterosigmoidoscopyMethanol poisoningRenal tubular acidosisDiarrhoea  <response>: Ans: b Methanol poisoning Ref: Harrison 17th edition Page 291-292Anion gap is the measure of unmeasured anions.AG Na-Normally anions cationsAny increase in anions other than Cl- or HCO3- will cause decrease in Cl- or HCO2 so that total anions is same in quantity. Eg increase in acetate, lactate, methanol, phosphate, albumin will increase AGDecrease in unmeasured cation Ca, Mg K will also have same result - increase AGExample of high anion gap acidosis:Lactic acidosis, Ketoacidosis, Ethylene glycol, Methanol, Salicylates, and Renal failure.Normal anion gap: 10-12 mmolLNormal anion gap acidosis:Loss of HCO3- from GIT or kidney will result in reciprocal change in - No change in anion gap and vice versaEg : 1 RTA UreterosigmoidoscpyCaCl,2 Renal failure with drug induced hyperkalemia3 Cation exchange resins 