Which of the following condition is diagnosed using a positive urinary anion gap?

Positive urinary anion gap is associated with distal A, as the kidney cannot excrete H+ as NH4Cl. The urinary anion gap (Na+ + K- - Cl-) reflects the ability of the kidney to excrete NH4Cl. It is used to differentiate between gastrointestinal and renal causes of hyperchloremic acidosis. In gastrointestinal cause of hyperchloremic acidosis such as in diarrhea, renal acidification remains normal and NH4Cl excretion increases, and the urinary anion gap is negative. Ref: CURRENT Medical Diagnosis and Treatment, 2012,Chapter 21