Calculi n. pl. : See Calculus.

Calculi pl. : of Calculus

Example:
Could I possibly have UTI or urinary Calculi?

Taxonomy
Calculi, stones, stone type, free encyclopedia, lithiasis, salivary duct calculus, infection, surgery, kidney stones, organ, duct, body, medical conditions, Treatment, gallstones, mineral type, stone formation, The Oxford Illustrated Companion to Medicine.

Defination from the web:
Calculi in the renal system (kidneys, ureters, urinary bladder, urethra) can be of any one of several compositions, including mixed. ... Enteroliths are a type of calculus found in the intestines of animals (mostly ruminants) and humans, and may be composed of inorganic or organic constituents. ...