Canker Sore Overview. Canker sores, also known as aphthous ulcers, are among the most common causes of painful sores in the mouth. 1  The classic lesion is a small (less than 1 centimeter) oval to round ulcer with a erythematous (red) border.2  They occur on the mucous membranes inside the mouth.anker Sore Overview. Canker sores, also known as aphthous ulcers, are among the most common causes of painful sores in the mouth. 1  The classic lesion is a small (less than 1 centimeter) oval to round ulcer with a erythematous (red) border.
Other Causes of Heavy Panting in Dogs. Heavy breathing or deep, intense panting can also be a symptom of eclampsia, also called milk fever. Eclampsia is a dangerous condition that affects nursing mothers; low blood calcium levels lead to an inability to stand or walk and tremors.
Potential Causes of a Heart Murmur in Dogs. There are a huge range of conditions that can cause a heart murmur in dogs. If your dog has a heart murmur, this is not in itself his âconditionâ. Rather the heart murmur is a symptom of another condition that your dog is suffering from. This other condition is causing the blood flow in the heart to be disturbed, either because it is changing the blood flow through the valves or because it has damaged the valves or heart chambers themselves.