Stool may be radiopaque for a large number of reasons. Finding the precise cause can be challenging, especially if the patient is unwilling or unable to give a history.


Being radiopaque may be diffuse or focal.


Common causes of stool being diffusely radiopaque:

(1) radiographic contrast material

(2) iron replacement therapy

(3) bismuth subsalicylate (Pepto Bismol)


Less common causes of stool being radiopaque:

(1) mercury, lead, arrsenic or other heavy metals

(2) meconium

(3) sand or clay

(4) iodide

(5) chloral hydrate

(6) carbon tetrachloride


Causes of focal radiopaque material:

(1) intestinal transit markers

(2) foreign bodies (metal, glass, other)

(3) animal and some fish bones

(4) enteric-coated or slow-release medications

(5) many medications

(6) gravel


Interestingly aluminum is radiolucent and not radiopaque,



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