Milk Stones in Dairy Cattle: From Pathogenesis to Ultrasonographic Diagnosis and Clinical Management

Milk stones (lactoliths) are poorly understood structures occurring within the ductal and cisternal systems of the bovine mammary gland. Although they have been described in the veterinary literature for more than 150 years, data on their formation, composition, prevalence, and clinical significance remain limited. This review synthesizes evidence identified through searches of PubMed, Scopus, Web of Science, and Google Scholar, supplemented by screening reference lists and historical veterinary sources. Historical concepts of their pathogenesis have included precipitation of milk minerals, aggregation or coagulation of proteins, and the formation of an organic core around which organic and mineral components may subsequently accumulate. Studies of corpora amylacea, secretory concretions, and mineralization of alveolar contents confirm that protein–mineral structures can form within the mammary gland; however, their relationship to clinically recognized lactoliths has not been established. Likewise, no direct association has been demonstrated between lactolith formation and prolonged milk accumulation, incomplete emptying of the gland, or mastitis. The clinical significance of lactoliths primarily results from their potential to cause partial, intermittent, or complete impairment of milk outflow. Ultrasonography enables their localization and morphological assessment and assists in differentiating them from other causes of obstruction; however, validated ultrasonographic criteria for the definitive identification of these structures are lacking. This review summarizes current knowledge of the terminology, possible mechanisms of formation, clinical significance, diagnosis, and management of lactoliths in cattle and identifies the most important directions for future research.