A urinary tract infection caused by urea-splitting bacteria will emit an ammoniacal odor Rectum Stool odors vary with diet, medications, and microbiologic flora Various malabsorptive syndromes, such as sprue, cystic fibrosis, and Whipple disease, are associated with foul-smelling stool The blood in the stool has a distinctive pungent odor, as does the pus Shigella and Salmonella have distinctive rank odors Systemic Diseases Several nutritional syndromes ( Table 50.1 ), such as pellagra’s stench of sour or musty butter and the putrid or fetid smell of scurvy and gout, have unique odors Schizophrenia has a characteristic body odor described as heavy, unpleasant, and pungent The odor-producing substance is trans- 3-methyl-2-hexenoic acid, which is produced in the sweat Uremic breath is produced by secondary and tertiary amines, dimethylamines, and trimethylamines that produce a fishy odor Malignancy, especially when associated with an expanding external mass, bleeding, and necrosis, gives off a trenchant odor because of tissue and cellular breakdown plus gas formation Hepatic failure gives an odor of “fetor hepaticus” (described as musty, rotten eggs, or garlic) and is noted in the breath or urine In Crohn disease, the development of gastric fistulae is often heralded by a feculent odor