Urolithiasis in Small Ruminants

By Barry Whitworth

Urolithiasis, commonly called urinary calculi, is a condition familiar to most small ruminant producers. Urolithiasis is the formation of calculi or stones in the urinary tract. The urinary tract includes the kidneys, ureters, bladder, and urethra.

Many factors can be causes of stone formation. It is most unlikely that one single factor causes urolithiasis. Formation is more likely the result of several factors occurring at the same time. Urinary stones may form in any part of the urinary tract, but most problems seen by producers involve stones that lodge in the urethra and prevent the animal from urinating.

Urinary stone formation occurs with equal frequency in male and female animals; however, the clinical signs are most often seen in castrated males. The obstruction in males is most often found in the urethra process at the end of the penis or in the sigmoid flexure.

Several factors can cause stone formation. Stones can form when damage occurs to the epithelial tissue. The epithelium is tissue that lines the urinary tract and provides a physical barrier to foreign invaders such as bacteria. When the epithelial tissue is damaged, cells slough and may form a nidus. This provides a place for crystals to a form a stone. Urinary tract infections are one of the major factors that damaged the epithelial tissue. Vitamin A deficiency may also play a contributing role in stone formation since Vitamin A is important in maintaining healthy epithelial tissue.

Another cause leading to stone formation is diets high in protein. Feeding excess protein or grazing legumes high in estrogenic compounds result in increase sediment in the urine. Sediment known as mucoprotein provides the building blocks for stones to form. Estrogenic compounds may be high in legumes such as clovers and alfalfa.

Learn more in the March issue of OKFR!