When it comes to healthy breeds, the Norwich Terrier is close to the top of the list. Many websites will actually claim that this breed is not particularly prone to any health issues at all; while this is not entirely true, serious health issues in the breed are rare and the Norwich is definitely a hardy little dog. One of the most concerning health issues to be found in the breed has only recently become a problem, due to its seemingly increasing appearance in a few lines.
Indeed, more and more Norwich are displaying respiratory problems, which include mainly a number of upper airway issues, and which have now become grouped under the heading of Upper Airway Syndrome. Norwich Terriers with this syndrome can suffer from a soft palette that is too long or too short, a trachea that is too narrow, not shaped correctly, or prone to collapsing, small nasal passages that make breathing difficult, tonsils that are swollen and, finally, everted laryngeal saccules; a dog can even suffer from more than one of these problems at one time.
Breeders are most concerned about the everted laryngeal saccules, once thought to be common only in dog breeds with characteristic "smushed" faces, like the Shih Tzu and the Bulldog. In these dogs, the saccules normally situated in the folds of the larynx, or voice box, that aid in resonating sound actually protrude into the airway, blocking the passage of air to varying degrees. There are essentially two types of problematic saccules, though both are thought to be the result of chronic inflammation and each time they are irritated, scar tissue builds up. Treatment usually involves removing the saccules and this surgery usually poses little risk to the dog; in some cases, though, so much scar tissue has already built up that the airway will forever be compromised, even in the absence of the saccules. In these cases, you must monitor your Norwich Terrier's lifestyle well, avoiding heat intolerance, limiting excitement and maintaining proper weight.
One of the most obvious indications of everted saccules is a tendency to breathe in a raspy or moist manner, especially after exertion, though many Norwich do not make these sounds. Your best bet is to simply have your dog checked on a regular basis. You can discuss with your vet what type of exams should be done and what type of surgery will resolve the problem in the case that saccules are indeed found. Depending on whether the respiratory problems are due to everted saccules or some other respiratory condition, your veterinarian may first suggest drug therapy to avoid risks associated with certain types of surgery. Something like an elongated soft palate or a tracheal collapse, for example, if not serious, may be alleviated with corticosteroids, bronchodilators, or cough suppressants.
Unfortunately, such a large number of Norwich seem to be affected by some type of respiratory issue that breeders claim it is impossible to exclude all compromised individuals from breeding programs, or the Norwich may face extinction. It has become such a concern that the Norwich and Norfolk Terrier Club have created a committee to research the problem.