CALB2 and fecal incontinence: Interestingly, nerve fibers expressing calretinin (CR), which in mouse small intestine has been reported to be expressed by excitatory smooth muscle motor neurons, interneurons, and some intrinsic sensory neurons, were not changed with age.19 An increase in the thickness of the IAS with age has been described in women,20, 21, 22 although this is not associated with changes in basal tone except in women with fecal incontinence.20, 21