Anjop J. Venker-van Haagen, DVM, PhD, ECVS
Obstructive nasal disease is recognized by nasal stridor--the sound produced by the passage of the respiratory airflow through a narrowed passageway--and dyspnea and nasal discharge. Sneezing and epistaxis are sometimes found. The obstruction may be unilateral or bilateral. Dyspnea is found to be less severe when the obstruction is unilateral and when the dog or cat is breathing via the mouth. Neither dogs nor cats breathe via the mouth spontaneously, but in dogs panting with an open mouth is more natural when playing and running. Information in the history about staying power in dogs should be interpreted with this in mind when nasal obstruction is said to have no influence on staying power. The loss of the sense of smell is not recognized by the owner in the home situation for dogs: the dog will find the food. Cats are more often said to have become less keen on food and sometimes have to be fed by the owner to be kept from losing weight.
Nasal polyps are focal proliferations of the mucosa which are not neoplastic but inflammatory and consist of a rounded mass attached to the mucosa by a stalk. They are most common in the nasal cavity of cats and are rare in dogs. They rarely arise in the sinuses, although extreme cases of polyps in the nasal cavity and frontal sinuses in cats have been described and illustrated. Nasal polyps consist of focal accumulations of edema fluid and proliferation of the submucosal connective tissue, with a variable inflammatory infiltrate consisting of eosinophils, plasma cells, and lymphocytes. They usually originate in the caudal part of the nasal cavity and consequently are covered by ciliated respiratory epithelium. The occurrence of nasal polyps is usually associated with chronic rhinitis. Recent studies of inflammatory nasal polyps in humans suggest an important role for proinflammatory cytokines, chemokines, and chemotactic factors in their pathogenesis, along with a variety of environmental, genetic, and biochemical factors.
The clinical signs of nasal polyps are those of obstructive rhinitis, with dyspnea and loss of olfaction, and nasal discharge during sneezing. Bilateral obstruction may be caused by bilateral polyps or by a unilateral polyp that extends into the nasopharynx. Radiographs reveal a unilateral or bilateral density with minimal loss of conchae. The diagnosis is made by rhinoscopy. The polyp is seen as a red mass in the nasal cavity and biopsy reveals it to be inflammatory tissue.
Treatment consists of surgical removal of the polyp, but locating its origin and removing it under vision can be very difficult. The alternative is to remove the polyp together with all of the conchae in the nasal cavity, which can be done via a small opening in the nasal bone.
The cat is anesthetized and with an endotracheal tube in place it is positioned in sternal recumbency. The skin on the dorsum of the nose is surgically clipped and disinfected, and an incision is made on the midline from caudal to rostral. The skin is then reflected laterally on the side on which the nasal bone is to be trephined. Trephination allows the conchae and the polyps to be removed through the opening in the nasal bone. Hemorrhage is stopped by compression with gauze pads. The subcutis is sutured together with the periosteum, taking care that the closure is air-tight, and the skin incision is closed routinely. Analgesics are administered for 5 days and antibiotics for 10 days. The cat should be assisted to eat and drink, without which fluid and nutrition must be administered. If necessary, surgery can be performed on the contralateral nasal cavity after 6 to 8 weeks, when the cat is eating normally.
Especially in the cat, the removal of olfactory epithelium results in loss of the ability to recognize food. Hence when polyps are bilateral it is advisable to remove them in two stages. After one nasal cavity has been freed of polyps the cat regains its sense of smell with the contribution of the intact side. If necessary, surgery can also be performed on that side after the cat has recovered fully and eats without hesitation.
Dogs sometimes have a single nasal polyp but they may also have multiple proliferations in the caudal nasal cavity that close the opening to the nasopharynx. Treatment consists of surgical removal of the abnormal tissues via an opening in the nasal bone. The polyps usually originate on one side but sometimes, as in cats, they extend into the nasopharynx and may obstruct the caudal nasal openings bilaterally. Using suction through the caudal nasal opening, the polyp can be drawn out of the nasopharynx into the caudal nasal cavity, from which it can be removed. Surgical treatment is similar to the surgery for nasal polyps in cats. There is usually considerate blood loss in dogs. Dogs seldom have problems in recognizing food after surgery. In both dogs and cats the excised tissue should be examined histologically for possible neoplasia, regardless of the histological findings in biopsies obtained before surgery. The polypous proliferation in dogs may recur after a year or two, but single polyps in cats and dogs seldom recur.
In cats, polyps in the nasopharynx obstruct the airflow through the nasal cavity and therefore are one of the obstructive nasal diseases. Nasopharyngeal polyps are polyps found in the nasopharynx but not necessarily originating in the nasopharyngeal mucosa. The most common polyp in the nasopharynx of the cat originates in the middle ear and descends to the nasopharynx via the auditory tube. The mucosa of the middle ear in some cats is affected by polypous inflammatory disease. Bacterial infection causes focal hypertrophy of the mucosa, leading to polyps which are not true neoplasms. These develop on a stalk and extend through the auditory tube to reach the nasopharynx, where they may grow substantially--a diameter of 3 cm is not uncommon--and thus form a nasopharyngeal polyp. A polyp that arises in the mucosa of the middle ear and grows through the tympanic membrane into the external ear canal is termed a middle ear polyp. It will be found to consist of focal accumulations of edema fluid accompanied by hyperplasia of the submucosal connective tissue and a variable inflammatory infiltrate of eosinophils, plasma cells, and lymphocytes. It is covered by ciliated columnar epithelium and goblet cells. Secondary bacterial infection and inflammation of the nasopharyngeal mucosa is to be expected.
The clinical signs of a nasopharyngeal polyp are due to obstruction of the nasopharynx, inspiratory dyspnea being the principal effect. Food intake is interrupted because of blockage of the passage of air through the nose, but there is no nasal discharge initially. After a long interval secondary inflammation in the nasal cavity may cause rhinitis. Diagnosis is based on the clinical signs and on a laterolateral radiograph of the pharyngeal area, which reveals a mass in the middle of the nasopharynx, depressing the soft palate. Oropharyngeal inspection under sedation reveals ventral depression of the soft palate, which sometimes partly blocks the view of the larynx and thus hinders endotracheal intubation. Treatment consists of removal of the polyp under anesthesia. The soft palate is retracted rostrally or incised so that a curved mosquito forceps can be inserted between the dorsal wall of the nasopharynx and the polyp in order to clamp the polyp stalk. After rotating the forceps and polyp, to be certain that no nasopharyngeal mucosa is included, the polyp is removed by a sharp tug. Bleeding is controlled by pressing a gauze sponge into the nasopharynx at the location of the openings of the auditory tubes. If it has been necessary to incise the soft palate, the nasopharyngeal mucosa and the oropharyngeal mucosa are sutured separately, the muscle layer being included with one of them. An antibiotic is prescribed only if there is severe rhinitis and nasopharyngitis. In most cases the cat awakens breathing through the nose without dyspnea, and no further care is needed.
Tumors occur in the nasal cavity of dogs and cats of all ages, but most often from the age of 5 years onwards. Almost all of these tumors are malignant. They invade the surrounding tissue but rarely metastasize before the cat must be euthanized. The most frequent tumors are squamous cell carcinoma and adenocarcinoma; less frequent are chondrosarcoma, osteosarcoma, and lymphosarcoma.
The clinical signs include sneezing, hemorrhagic discharge, and mucopurulent discharge. In most cases unilateral obstruction of the nasal cavity is recognized because of nasal stridor. No evidence of pain is observed and the cat becomes dyspneic only when the mouth is closed, which means when sleeping. As long as the tumor is unilateral the dyspnea is moderate. When the tumor obstructs both nasal cavities, dyspnea becomes a serious hindrance. Cats often stop eating, which may provide a humane end point and a reason for euthanasia. In dogs severe dyspnea and recurrent epistaxis are reason for euthanasia.
Diagnostic radiographs should be made under anesthesia. Tumor is suspected when increased density is found in one or both nasal cavities, with loss of normal conchal structures. In all cases in which the radiographic diagnosis is uncertain, rhinoscopy is the next diagnostic procedure. Under rhinoscopic visualization the tumors vary greatly in shape and firmness, and their color ranges from gray to deep red. Biopsies are always taken for histological confirmation of the diagnosis. If no therapy is planned, neither CT nor MRI is indicated. Radiation therapy could be considered.
1. Venker-van Haagen AJ. The nose and nasal sinuses. In: Ear, Nose, Throat, and Tracheobronchial Diseases in Dogs and Cats. Hannover: Schlütersche Verlagsgesellschaft, 2005: 51-79.