Mitral annular calcification
Here is parasternal long axis view obtained from a patient with diabetes mellitus and chronic kidney disease with altered bone mineral metabolism. Note the hyperechoic calcification along the posterior mitral annulus with prominent shadowing. Labeled image and a few points pertinent to nephrology below.
Here are similar images from an end-stage renal disease patient. In addition to mitral annular calcification, you can see concentric left ventricular hypertrophy and aortic stenosis (valve is not opening completely and has some calcification). Images obtained using a handheld ultrasound machine.
Another example with chest X-ray for comparison.