Final answer:
Frequent vomiting, signs of dehydration, and diarrhea lasting more than three days are all clinical signs that warrant immediate veterinary attention due to the risk of serious underlying conditions.
Step-by-step explanation:
There are several clinical signs that indicate a patient should be seen by a veterinarian immediately. One of these signs is frequent vomiting, which can quickly lead to dehydration. This condition is particularly concerning if the vomiting prevents the patient from keeping liquids down. Secondly, signs of dehydration itself are a critical indicator, including a marked decrease in urination, a very dry mouth and throat, or feeling dizzy when standing up. Lastly, diarrhea that persists for more than three days can be a symptom of a serious underlying condition and warrants immediate veterinary attention. Each of these symptoms can signify potentially life-threatening issues requiring prompt and thorough medical assessment.