Porcupines have 30 000 quills largely concentrated on their tails which they swing at predators. The quills aren't thrown off but do detach easily. The quills have white tips, and the portion that penetrates the skin is black. This makes it difficult to see especially when the dogs fur is dark like this patient.
It is important not to try to remove quills at home. Pulling the quills is not only painful but they break easily and the tip can remain embedded in the skin. This can cause an infection or abscess. The pieces can also migrate through the body, risking puncturing or tearing organs.
Additionally it is important not to cut or trim the quills. The shorter pieces can make their way into the skin making them impossible to find. They can also migrate much like a broken quill.
When you bring your pet to the veterinarian they will sedate or put your pet under general anesthetic in order to safely remove the quills with minimal pain. When your pet is relaxed it is also easier to feel the entire body for quills that may have been missed. As well as remove tough to reach quills in their mouths.
If your pet ingests quills, making them vomit often causes more harm than good due to the risk of perforating the esophagus. Feeding high fiber foods such as canned pumpkin or boiled asparagus can bind to the quills and decrease the risk that they will cause damage as they pass through the digestive system.