Inulin's usefulness as a diagnostic agent is based on the method of its elimination from the body. Inulin is biologically inert, unbound by plasma proteins, freely filtered at the glomerulus, and is neither reabsorbed, metabolized nor secreted by the kidneys. It is excreted almost entirely by glomerular filtration. Inulin clearance is considered to be identical to glomerular filtration rate (GFR).

1. Main inclusion criteria: Pediatric OPD, age < 18 y/o.
2. Main exclusion criteria: Acute renal failure, edema, muscular dystrophy, pleural effusion, ascites, malnutrition, neurogenic bladder, heart failure and ketoacidosis. And taken cimetidine or trimethoprim, and accepted renal replacement therapy.

Pediatric OPD, age < 18 y/o.