Clinical Assessment of Primary Hemostasis: A Review

•Primary hemostasis consists of platelet adhesion, activation, and aggregation.•Common clinical signs caused by a primary hemostatic disorder include cutaneous bleeding, mucosal bleeding, and bleeding into the gastrointestinal tract.•A preliminary differentiation of thrombocytopenia vs. thrombocytopathia can be made using readily available testing in the clinic.•Von Willebrand disease is an inherited thrombocytopathia with 3 primary categories diagnosed by the von Willebrand factor assay.•Understanding the available platelet function tests is beneficial to clinicians. Primary hemostatic disorders such as thrombocytopenia and thrombocytopathia are commonly encountered in small animal practice. The key stages of primary hemostasis include platelet adhesion, activation, and aggregation. Understanding the interaction between tissues, platelets, and signaling molecules not only helps clinicians comprehend clot formation but also better recognize thrombocytopathias. Although congenital thrombocytopathia is rare, commercially available platelet function tests allow veterinarians to narrow differentials in many clinical settings. Thrombocytopenia can be easily diagnosed in any clinical setting. In this paper, we review the current understanding of primary hemostasis in veterinary medicine, including the clinical presentation and available diagnostics to identify platelet abnormalities.