The smell of the urine of a healthy and well-hydrated person is normally "sui generis" and as such lacking in bad fragrances. We are in fact talking about a normally aseptic liquid, which contains variable concentrations of waste substances depending on the diet, health and hydration status, and the use of any drugs.
Food and smell of urine
Some foods of normal consumption can alter, sometimes in a very unpleasant way, the smell of urine. Asparagus (which also changes its color, moving it towards greenish), cauliflower and garlic are typically accompanied by foul-smelling urine.
Other causes of urine odor
Variations in the smell of urine are generally temporary and are not always a sign of pathological conditions. Among the innumerable causes responsible for these alterations we recall:
Dehydration (because the solute responsible for bad smell increase its concentration; the urine takes on a particularly dark complexion and a characteristic aroma of ammonia);
Cystitis, urinary infections, pyelonephritis (kidney infections), urethritis, prostatitis and vaginitis (in this case the problem may not be related to the urinary tract, given the anatomical proximity - to learn more see: vaginal odor);
Hepatic failure;
Diabetic ketoacidosis and ketonuria (also typical of prolonged fasting, is accompanied by abundant sweet-smelling urine, similar to acetone);
Rectovaginal fistula;
Phenylketonuria (rare disease present since birth);
Taking vitamin B-6 supplements;
Metabolic disorders;
Maple syrup urine disease (rare);
Trimethylaminuria or fish odor syndrome (rare);
Also some drugs can alter the smell of urine; among these we mention some antibiotics such as amoxicillin, ampicillin, nitrofurantoin, ciprofloxacin, norfloxacin, ofloxacin and trimethoprim.
The causes of the bad smell of urine can be investigated through a simple examination of the urine and their culture (to look for possible bacterial infections).
