Nasal Discharge

W. David Wilson • Jeanne Lofstedt • Jeffrey Lakritz

■ Definition Nasal discharge, which is any nongaseous material that exits the respiratory tract through the external nares, is described according to its physical characteristics (serous, mucoid, purulent, hemorrhagic [sanguineous], or a combination of these types with or without feed material); acuteness of onset (sudden or insidious); origin (unilateral or bilateral); volume (profuse or scant); and association with activity (spontaneous or 38 40

intermittent).^38-40

■ Pathophysiology

NORMAL NASAL SECRETIONS.

Serous nasal secretions in normal animals are responsible for the moist appearance of the ventral portion of the external nares.

Lacrimal secretions also drain into the nasal passages through the nasolacrimal ducts and may appear at the external nares as a thin, watery, clear, nonviscous discharge, particularly in animals with conjunctival irritation or ocular inflammatory diseases that stimulate excessive lacrimation.³⁹

ABNORMAL NASAL SECRETIONS. Inflammatory conditions involving the nasal cavity stimulate increased production of glandular secretions.⁴¹ These secretions initially are serous but later become mucoid and purulent as secondary bacterial invasion induces an influx of neutrophils.³⁸ Serous nasal dis­charge generally indicates disease conditions affecting the nasal passages or upper respiratory tract.

Inflammation, irritation, and other pathologic states affecting the trachea and bronchi increase the production of mucous and serous secretions in the tracheobronchial tree⁴¹ (Boxes 5.3 and 5.4). Initially the accompanying nasal discharge is mucoid (clear, colorless, thin, and elastic in consistency), but with chronicity and secondary bacterial invasion, neutrophils and other inflammatory cells accumulate in the tracheobronchial secretions and the nasal discharge becomes purulent, progressing

■ BOX 5.3

Causes of Serous and Mucoid Nasal Discharge in Horses

Common Causes

Influenza

Equine herpesvirus types 1 and 4 (EHV-1, EHV-4)

Other viruses (e.g., rhinitis A and B viruses, adenovirus, reovirus, EHV-2)

Pharyngitis, chronic pharyngeal lymphoid hyperplasia

Nasal or paranasal sinus infection, cysts, polyps, tumors Early bacterial pneumonia or pleuritis

Early strangles (Streptococcus equi infection)

Guttural pouch infection, mycosis

Overflow of nasolacrimal ducts

Recurrent airway obstruction (RAO or chronic obstructive pulmonary disease)

Less Common Causes

Equine viral arteritis

Burn (thermal, chemical)

Anaphylaxis or acute drug reaction

Aspiration or foreign body pneumonia, smoke inhalation

Foreign body (nasal, pharyngeal, guttural pouch, tracheal, or bronchial)

Summer pasture-associated obstructive airway disease (SPOAD)

Uncommon Causes

Nasal fungal infection (rhinophycomycosis), aspergillosis Nasal amyloidosis

Coccidioidomycosis

Restrictive pulmonary disease, pneumoconiosis

Trauma to the skull or upper airway

Tuberculosis

Tularemia

Guttural pouch neoplasia

Chlamydia psittaci pneumonia

Nocardiosis

Cryptococcosis

Fungal granuloma, maduromycosis, rhinosporidiosis, mycetoma, pythiosis

Lungworm infection (Dictyocaulus arnfieldi)

Ascarid migration

Cyst (pharyngeal, subepiglottal)

Progressive ethmoidal hematoma

Lymphosarcoma, lymphoma, leukemia

Halicephalobus (Micronema) deletrix granuloma Pulmonary edema

Pulmonary aspergillosis

Stachybotryotoxicosis

Trichloroethylene-extracted feed toxicity Pentachlorophenol toxicity

Organophosphate, carbamate toxicity

Ammonia toxicity

St.

Trypanosoma equinum, mal de caderas (exotic)

Trypanosoma hippicum, murrina de caderas (exotic) Besnoitiosis, globidiosis (exotic)

African horse sickness (exotic)

Getah virus (exotic)

Glanders (exotic)

Louping ill (exotic)

from cloudy to opaque and then to viscous with a whitish cream color (Boxes 5.5 and 5.6).

Conditions such as chronic bronchitis and RAO cause goblet cell hyperplasia and increased mucous production, which may be reflected as a discharge at the external nares, depending on the efficiency with which the animal swallows these secretions. In some cases nasal discharge is evident only early in the morning or after a period of recumbence because in these situations secretions accumulate in the trachea and pharynx, drain into the nasal passages, and exit from the nares.

Hemorrhagic (sanguineous) nasal discharge, or epistaxis, occurs secondary to trauma, coagulopathies, and erosive or invasive conditions that insult the richly vascular nasal mucosa or secondary to conditions that invade regional blood vessels such as occurs when the internal carotid artery is eroded by a mycotic plaque in horses with guttural pouch mycosis. Pulmonary disorders such as infarctive pneumonia in horses and pulmonary thromboembolism secondary to posterior vena cava thrombosis in cattle may also induce epistaxis (see the Epistaxis and Hemoptysis section later).^38-40

Foul odor (ozena) accompanying nasal discharge suggests an anaerobic infection, a necrotizing condition (e.g., fungal infection, neoplasia, turbinate necrosis, or necrotizing pneu­monia), foreign body, or communication between the oral and nasal cavities (e.g., maxillary sinusitis secondary to tooth root infection in the horse).⁴⁰

Food or water may drain from the external nares when there is communication between the oral and nasal cavities (e.g., cleft palate), in association with swallowing disorders (e.g., pharyngeal paresis secondary to botulism, cranial nerve damage secondary to guttural pouch mycosis in the horse), or in cases of obstructive dysphagia (e.g., severe pharyngitis, guttural pouch enlargement in horses, retropharyngeal abscesses, esophageal obstruction, obstructions of the gastrointestinal tract that lead to regurgitation of food from the stomach).^38-40 The respiratory position of the epiglottis dorsal to the soft palate in the horse means that except in cases of dorsal displacement of the soft palate (laryngopalatal dislocation), food regurgitated from the digestive tract enters the nasopharynx and appears at the external nares rather than at the mouth (see Chapter 7).

Chronic nasal discharges often cause scalding in the area ventral to the external nares.³⁹ Mucoid and purulent nasal discharges tend to dry and crust as an admixture with envi­ronmental dust and dirt around the external nares. In all large animal species but particularly in sheep and goats, tenacious exudates may obstruct the nasal passages and induce a snuffling noise. Horses with profuse nasal discharge often rub the nose on the dorsum of the front fetlock and cannon regions. During the physical examination, these areas should be inspected for mucoid exudate, dried crusts, or swarms of flies.

ACUTENESS OF ONSET. Sudden -onset nasal discharge is usually associated with acute infection, trauma, or esophageal obstruction, whereas nasal discharge of insidious onset generally accompanies chronic infection, progressive neurologic disease that causes dysphagia, or neoplasia.⁴²

ORIGIN OF NASAL SECRETIONS. Unilateral nasal discharge generally originates from structures located rostral to the caudal end of the nasal septum. Bilateral nasal discharge results from disease processes affecting structures caudal to the nasal septum or from conditions involving the nasal passages or paranasal sinuses bilaterally.^39,40 A discharge that appears from one nostril on some days and from the opposite nostril on others generally indicates a lesion or disease process caudal to the nasal septum.⁴⁰ The paired guttural pouches of the horse drain separately through ostia located dorsolaterally in the wall of the naso­pharynx. Exudate draining from the guttural pouches may appear unilaterally at the ipsilateral nostril if the volume of drainage is small, but moderate to profuse guttural pouch drainage appears as a bilateral nasal discharge.⁴⁰

VOLUME OF NASAL SECRETIONS. The volume of nasal discharge frequently increases when the head is lowered,

■ BOX 5.4

Causes of Serous or Mucoid Nasal Discharge in Ruminants

Common Causes

Debilitating illnesses that reduce lingual nose cleaning in cattle (B)

Mannheimia haemolytica or Pasteurella multocida pneumonia (includes shipping fever and enzootic calf pneumonia)

Histophilus somni pneumonia (B) Nose bots (Oestrus ovis) (O, C) Lungworm infection, verminous pneumonia Atypical interstitial pneumonia (B)

Infectious bovine rhinotracheitis (IBR; BHV-1) (B, C) Bovine respiratory syncytial virus (B)

Parainfluenza virus type 3 Mycoplasma species pneumonia Caprine Mycoplasma mycoides subsp.

Trauma (nasal, oral, pharyngeal, laryngeal, tracheal, bronchial, chest wall)

Abscess (oral, pharyngeal, retropharyngeal) Esophageal obstruction, foreign body, choke Septicemia (neonates)

Less Common Causes

Paranasal sinus infection

Foreign body (oral, pharyngeal, laryngeal, tracheal, bronchial, pulmonary)

Aspiration, foreign body pneumonia Ovine progressive pneumonia and arthritis, maedi (O) Bluetongue

Bovine virus diarrhea (BVD-MD) (B) Ovine adenovirus (O)

Caprine respiratory syncytial virus (C) Bovine rhinovirus (B)

Bovine adenovirus (B) Bovine malignant catarrhal fever, early (B)

Herpesvirus DN-599 (B) Bovine herpesvirus type 4 (BHV-4) (B) Pulmonary adenomatosis (Jaagsiekte) (O) Inhalation pneumonia, smoke, noxious gases Anaphylaxis or adverse drug reaction Milk allergy in cows (B)

Farmer's lung disease (hypersensitivity to Faenia rectivirgula, Aspergillus fumigatus, and other mold spores) (B)

Chlamydia psittaci pneumonia

Burns (thermal, chemical) Vagal indigestion, abomasal impaction

Nasal adenoma, adenopapilloma, adenocarcinoma, polyp (O, C)

Uncommon Causes

Familial allergic rhinitis (B) Bovine nasal granuloma, atopic rhinitis, summer snuffles (B) Fungal granuloma, maduromycosis, mycetoma, rhinosporidiosis Nasal actinobacillosis (B)

Sarcocystosis (B) Tularemia (O)

Phycomycosis, pythiosis (B) Pulmonary aspergillosis

Bronchobiliary fistula (yellow froth) (B) Zygomycosis, mucormycosis (B)

Pneumocystis carinii (renamed PneumocystisJiroveci in humans) pneumonia

Neoplasia (nasal, paranasal sinus, pharyngeal, pulmonary)

Buss disease, chlamydial sporadic bovine encephalomyelitis (B) Winter dysentery (B)

Immunodeficiency states Pregnancy toxemia (B) Border disease (hairy shaker) (O, C) Lymphosarcoma

Johne's disease Listeriosis (C)

Tetanus

Rinderpest (exotic) Theileriosis, East Coast fever (exotic)

Contagious bovine pleuropneumonia (exotic) (B) African bovine malignant catarrhal fever, early (exotic) (B) Virulent sheep and goat pox (exotic) (O, C) Peste des petits ruminants (exotic) (O, C)

Contagious caprine pleuropneumonia (exotic) (C) Rift Valley fever (exotic)

St.

Trypanosomiasis, nagana (exotic) Jembrana disease (exotic) (B) Sweating sickness (exotic) (B, O) Cestrum poisoning (exotic) Stinkweed poisoning (exotic) (B) Endemic ethmoid carcinoma (exotic) (B)

Ephemeral fever (exotic) (B) Lumpy skin disease (exotic) (B) Nasal schistosomiasis (exotic) Besnoitiosis, globidiosis (exotic) Louping illness (exotic) Theilezia rhodensis (exotic)

Cotyledon species poisoning, Krimpsiekte (exotic) (O, C) Gedoelstia hasleri nasal bots (exotic) (O, C) Nairobi sheep disease (exotic) (O, C) Schistosoma nasale (exotic) (B)

Toxic Causes

Organophosphate or carbamate Mercury (B)

Iodine (B, O) Ammonia

Sodium hydroxide (caustic soda) Trichloroethylene-extracted feed (B, O) Formaldehyde irritation

Oxalate (B, O) Thallium (O) Furazolidone Hairy vetch (Vicia villosa) (B) Ergot (Claviceps purpurea) Sneezeweed (Helenium species)

Aflatoxicosis (C)

Rubber weed (Hymenoxys species) Acorn, oak (B, O)

Perennial broomweed (Gutierrezia species) Chinese tallow (Sapium sebiferum) (B) Stachybotryotoxicosis

Slender ice plant (Mesembryanthemum nodiflorum)

B, Bovine; C, caprine; O, ovine.

regardless of the source of the discharge, because of pooling of exudate in the trachea, pharynx, or nasal passages. However, the appearance of profuse, unilateral, purulent nasal discharge when the head is lowered generally indicates sinus empyema, and profuse bilateral nasal discharge under these circumstances suggests guttural pouch empyema.²¹ This is attributed to accumulation of large volumes of exudate in the sinus cavities or guttural pouches when the head is elevated and to the fact that the ostia through which these structures drain are not located on the most dependent aspect of these cavities; thus

■ BOX 5.5

■ BOX 5.6

Causes of Purulent Nasal Discharge in Horses

Common Causes

Postviral bacterial infection of the respiratory tract Strangles (Streptococcus equi subsp. equi infection) Bacterial rhinitis

Pharyngitis

Bacterial pneumonia

Bacterial pleuritis or pleuropneumonia

Guttural pouch empyema or chondroids

Guttural pouch mycosis

Lung abscess

Pharyngeal, retropharyngeal abscess

Paranasal sinus infection, cyst, tumor (unilateral discharge)

Less Common Causes

Fungal rhinitis (rhinophycomycosis), nasal granuloma, nasal aspergillosis (unilateral discharge)

Nasal foreign body (unilateral discharge)

Conchal necrosis (unilateral discharge)

Progressive ethmoidal hematoma (unilateral discharge) Nasal tumor, polyp, cyst (unilateral discharge)

Trauma (nasal, skull, upper airway) (unilateral or bilateral discharge)

Burn (thermal, chemical)

Aspiration or foreign body pneumonia, smoke inhalation

Foreign body (pharyngeal, guttural pouch, tracheal, bronchial) Esophageal obstruction, choke, stricture, ectasia, megaesophagus Neurologic deficits affecting swallowing

Uncommon Causes

Coccidioidomycosis

Tuberculosis

Tularemia

Guttural pouch neoplasia

Chlamydia psittaci pneumonia

Nocardiosis

Cryptococcosis

Fungal granuloma, maduromycosis, rhinosporidiosis, mycetoma, pythiosis

Ascarid migration

Lymphosarcoma, lymphoma, leukemia

Halicephalobus (Micronema) deletrix granulomas

Pulmonary aspergillosis

Pneumocystis carinii (renamed PneumocystisJiroveci in humans) pneumonia

Ammonia toxicity

Hendra virus (exotic)

Trypanosoma evansi, surra (exotic)

Besnoitiosis, globidiosis (exotic)

African horse sickness (exotic)

Glanders (exotic)

Melioidosis, Pseudomonas pseudomallei (exotic)

significant drainage can occur only when the head is lowered. Nasal discharge observed only after exercise suggests an origin in the lower respiratory tract.⁴³

Approach to Diagnosis of Nasal Discharge

Because many conditions, particularly those involving the lower respiratory tract, are associated with both nasal discharge and cough, the diagnostic approach used for large animal patients presented for evaluation of nasal discharge is similar to that used for large animals presented for evaluation of cough (see the Cough section earlier). Only the components of the history and diagnostic evaluation that differ substantially from those used in patients with cough are described in depth in this section.

Causes of Purulent Nasal Discharge in Ruminants

Common Causes

Debilitating illnesses that reduce lingual nose cleaning in cattle Postviral bacterial infection of the respiratory tract

Mannheimia haemolytica or Pasteurella multocida pneumonia Histophilus somni pneumonia (B)

Necrotic laryngitis, calf diphtheria (B)

Lungworm infection, verminous pneumonia

Mycoplasma species pneumonia

Caprine Mycoplasma mycoides subsp. mycoides infection (C)

Chronic bacterial pneumonia with consolidation or abscessation (Arcanobacterium pyogenes and other bacteria)

Esophageal obstruction, foreign body, choke

Nose bots (Oestrus ovis) (O, C)

Trauma (nasal, oral, pharyngeal, laryngeal, tracheal, bronchial, chest wall)

Abscess (oral, pharyngeal, retropharyngeal)

Septicemia (neonates)

Less Common Causes

Foreign body (oral, pharyngeal, laryngeal, tracheal, bronchial, pulmonary)

Aspiration, foreign body pneumonia

Paranasal sinus infection

Pulmonary embolism from posterior vena cava thrombosis (B)

Ovine progressive pneumonia and arthritis, maedi (O)

Bovine malignant catarrhal fever (B)

Bluetongue

Pulmonary adenomatosis (Jaagsiekte) (O)

Inhalation pneumonia, smoke, noxious gases

Chlamydia psittaci pneumonia

Burns (thermal, chemical)

Vagal indigestion, abomasal impaction

Nasal adenoma, adenopapilloma, adenocarcinoma, polyp (O, C)

Uncommon Causes

Ovine nasal granuloma, atopic rhinitis, summer snuffles (B)

Fungal granuloma, maduromycosis, mycetoma, rhinosporidiosis

Nasal actinobacillosis (B)

Bovine salmonellosis (B)

Sarcocystosis (B)

Tularemia (O)

Tuberculosis

Phycomycosis, pythiosis (B)

Pulmonary aspergillosis

Bronchobiliary fistula (yellow froth) (B)

Zygomycosis, mucormycosis (B)

Pneumocystis carinii (renamed PneumocystisJiroveci in humans) pneumonia

Neoplasia (nasal, paranasal sinus, pharyngeal, pulmonary) Immune deficiency states

Lymphosarcoma

Toxic and Exotic Causes

See Box 5.4.

B, Bovine; C, caprine; O, ovine.

HISTORY. The patient history should include information about the rapidity of onset and duration of nasal discharge; whether the discharge is consistently unilateral, consistently bilateral, or intermittently bilateral; and the volume, color, consistency, and odor of the discharge.

The association of discharge with certain activities—such as initiation of exercise, when the animal is first disturbed in the morning, or when it is eating with its head lowered—can provide useful clues to the origin or cause. It should be determined if the animal is showing other signs of respiratory disease (e.g., cough, respiratory distress, or exercise intolerance), dental disease (e.g., quidding or slow eating), or systemic disease (e.g., weight loss, depression, anorexia, fever, or lymphadenopathy).

It should also be determined if in-contact animals have exhibited nasal discharge or other signs of respiratory disease. The vaccination status of affected and in-contact animals should be ascertained. Recent transportation, surgery, or weaning should be noted as supportive of stress, and a history of contact with other animals at sales, shows, or other events should be established. Environmental quality and the overall management of the affected animal and the herd should be assessed (see the Cough section earlier). Progression or improvement in the signs, attempted therapy, and response to current or previous treatments should also be ascertained.

PHYSICAL EXAMINATION. Physical examination of an animal showing nasal discharge should be complete and include inspection from a distance and close examination using ausculta­tion, palpation, and percussion techniques (see Physical Examina­tion in the Cough section earlier). The character and volume of the nasal discharge should be noted. Particular attention should be paid to whether:

• The nasal discharge is unilateral or bilateral

• The airflow from both nostrils is symmetric

• Odor emanates from the oral or nasal cavity

• Facial asymmetry is present

• Hyporesonance (dullness) or a painful response is elicited on percussion of the maxillary and frontal sinuses

• Enlargement of submandibular, parotid, retropharyngeal, or other regional lymph nodes is present

• Palpable turbulence such as a tracheal rattle is present

The depth and symmetry of chest expansion should be assessed, and the rostral end of both nasal passages should be illuminated with a penlight and examined carefully.

The roots of the third through the sixth maxillary cheek teeth (108 to 111 and 208 to 211) in the horse are contained within the maxillary sinus; therefore infection of these teeth frequently leads to sinus empyema with drainage from the nasomaxillary opening into the middle nasal meatus and ultimately to a unilateral nasal discharge. Disease involving the paranasal sinuses should be considered in horses with unilateral nasal discharge, particularly when ozena is present. Under these circumstances a thorough oral examination, which should include probing of the occlusal surfaces of the maxillary cheek teeth with a fine dental pick, is indicated. Particular attention should be paid to detecting erosive periodontal disease, fractured maxillary cheek teeth, open pulp chambers, and patent infundibula. In cattle the oral examination should include palpation of the base of the tongue, the oropharynx, and, if possible, the larynx to determine whether mass lesions or swelling of the tongue are present.

Further diagnostic evaluation of nasal discharge may include a complete blood count with determination of the fibrinogen concentration, a serum biochemistry profile, endoscopy of the upper and lower airways and the esophagus, nasal or nasopha­ryngeal swabbing for molecular diagnostic testing or virus isolation, virus serologic testing, tracheal aspiration, BAL, ultrasonography, thoracentesis, radiography, blood gas analysis, nuclear scintigraphy, fecal examination, pulmonary function testing, and lung biopsy. For further information on diagnostic procedures not discussed in the following sections, see the Cough section earlier.

ENDOSCOPIC EXAMINATION. Endoscopic examination of the upper and lower airways is a useful ancillary diagnostic procedure in all animals with nasal discharge. The nasal passages; the conchae (turbinates) including the ethmoidal conchae; the nasal septum; and the pharynx, larynx, and trachea should be examined through both nostrils. The presence, nature, and origin of exudates and the presence of anatomic or func­tional abnormalities or mass lesions should be noted. Although it is not possible to introduce standard, 8- to 12-mm-diameter endoscopes into the paranasal sinuses via the nasal passages, drainage from the sinuses may be detected by examining the middle meatus.⁴⁰ Examination of the middle meatus may also reveal turbinate necrosis or mass lesions (e.g., tumors, fungal granulomas, nasal foreign bodies). Lesions such as progressive hematomas (expanding mass lesions of variable size on the ethmoid turbinates) can be visualized by advancing the endo­scope slightly, after deflecting its tip dorsally through the common meatus, from a position in the caudal part of the ventral meatus just rostral to the choanae. In the horse the pharyngeal openings of the guttural pouches, which are located dorsolaterally on the wall of the pharynx, should be inspected for drainage. The interior of both guttural pouches can be examined for exudate, blood, mycotic plaques, and other proliferative lesions by advancing the endoscope through the pharyngeal openings of each guttural pouch. This procedure is facilitated by first introducing a biopsy instrument or similar guidewire into the guttural pouch via the biopsy channel of the endoscope.

Bronchoscopic examination may prove useful for identifying the bronchus of origin of pulmonary exudates and for facilitating appropriate BAL. In horses with intermittent bilateral nasal discharge, it may be helpful to repeat the endoscopic examina­tion after exercise, which often mobilizes secretions from the lower respiratory tract and causes them to pool in the horizontal trachea. Endoscopic examination of the esophagus is indicated in patients with a history of dysphagia or return of ingesta through the nose (Boxes 5.7 and 5.8).

RADIOGRAPHY. Radiography with lateral, dorsoventral, and oblique radiographic projections of the nasal passages, paranasal sinuses, pharynx, retropharyngeal area (including guttural pouches in the horse), larynx, and proximal trachea is indicated to confirm problems identified by clinical examination and endoscopy and to identify conditions not recognized by other diagnostic techniques. The demonstration of increases in tissue density, fluid lines, bony lysis or proliferation, distortion of normal architecture, or changes around tooth roots assists in the diagnosis and localization of disorders of the nasal passages, conchae, and paranasal sinuses. Space-occupying lesions in the oropharynx, nasopharynx, or larynx may also be demon­strated by radiographic examination of these areas. The presence of fluid lines, soft tissue densities, or thickening of the floor of the guttural pouches helps differentiate guttural pouch diseases (e.g., empyema) from other space-occupying lesions (e.g., abscesses) in the retropharyngeal region. Contrast radiographic studies such as barium swallows are indicated to evaluate aspiration during swallowing in horses suspected of having pharyngeal paresis. Carotid angiography under general anesthesia has been used to demonstrate aneurysms in the internal carotid artery of horses with guttural pouch mycosis.⁴⁴ Thoracic radiographs are indicated in patients suspected of having pulmonary, mediastinal, or pleural disease to determine the presence, pattern, and severity of radiographic changes.

COMPUTED TOMOGRAPHY SCANNING. When a definitive diagnosis is not achieved using plain radiographs, computed tomography (CT) scanning under general anesthesia has proven valuable for more accurately defining the location, nature, and extent of lesions involving the nasal passages, paranasal sinuses, and cheek teeth.^45,46 Intracarotid or IV injection of contrast material further enhances the diagnostic utility of CT for evaluation of mass lesions.

■ BOX 5.7

■ BOX 5.8

Causes of Ingesta in Nasal Discharge in Horses

Common Causes

Esophageal obstruction, choke Cleft palate, palatal hypoplasia (neonate) Pharyngitis

Strangles (Streptococcus equi infection) Dorsal displacement of the soft palate Guttural pouch infection, mycosis, neoplasia Glossopharyngeal nerve damage Botulism, shaker foal

Retropharyngeal abscess

Less Common Causes

Complications of laryngeal surgery

Laryngeal web defect

Epiglottal entrapment, subepiglottal abscess or cyst Tetanus

Fistula (pharyngeal, esophageal, esophagobronchial, esoph- agotracheal)

Esophageal stricture, ectasia, diverticulum, megaesophagus, ulcer, rupture

Gastric, duodenal ulceration (foals)

Gastric dilation, rupture Proximal enteritis, jejunitis Small intestinal obstruction

Rabies

Other neurologic deficits affecting swallowing

Uncommon Causes

Persistent right aortic arch, vascular ring anomaly Gastric tumor

Gastric stenosis

Rostral displacement of the palatopharyngeal arch Hypoplasia of the soft palate

White muscle disease, nutritional myodegeneration Rectus capitis ventralis muscle rupture Lymphosarcoma, lymphoma, leukemia

Oleander poisoning

White snakeroot (tremetol) poisoning Lead toxicity

Grass sickness (exotic)

ULTRASOUND EXAMINATION. Ultrasound examination of externally visible lesions such as possible retropharyngeal abscesses or distended guttural pouches assists in characteriza­tion of lesions and collection of samples by aspiration or biopsy. Thoracic ultrasound is indicated when lower airway, pleural, or cardiac disease is the suspected cause of nasal discharge.

PERCUTANEOUS ASPIRATION. Percutaneous aspiration, performed either blindly or with the assistance of ultrasound, followed by cytology and culture of aspirated material, is useful in the evaluation of masses such as submandibular or retro­pharyngeal abscesses that are also causing a nasal discharge.

CENTESIS. Centesis of affected paranasal sinuses helps localize the source of exudates and provides samples for cytologic examination and culture in patients with chronic unilateral nasal discharge in which sinus percussion or radiographic examination (or both) suggests the presence of a sinus lesion. In the normal horse the rostral and caudal maxillary sinuses are separated by a thin osseous septum. This septum is often eroded in horses with septic sinusitis; therefore the caudal maxillary sinus is typically entered first. If no exudate can be aspirated, either directly or after lavage of the sinus, and if

Causes of Ingesta in Nasal Discharge in Ruminants

Common Causes

Esophageal obstruction, foreign body, choke Pharyngeal, retropharyngeal abscess Pharyngeal trauma, foreign body Megaesophagus (B, C)

Less Common Causes

Rhododendron poisoning (O)

Diaphragmatic hernia

Water deprivation, salt toxicity (B, O)

Ruptured or lacerated esophagus

Tetanus

Cleft hard or soft palate Glossopharyngeal nerve damage

Uncommon Causes

Neoplasia of the esophagus or rumen (B)

Persistent right aortic arch, vascular ring anomaly (B, O) Listeriosis

Bronchobiliary fistula (yellow froth) (B)

Congenital defects of Kodiak Island calves (B) Oleander poisoning

White snakeroot (tremetol) poisoning (B, O) Crude oil toxicity (B)

Geigeria species poisoning Sneezeweed (Helenium species) poisoning Rubberweed (Hymenoxys species) poisoning

B, Bovine; C, caprine; O, ovine.

increased purulent drainage from the ipsilateral nostril is not accomplished during lavage, centesis of the rostral maxillary sinus is performed and the procedure is repeated. If the aspirated material is not malodorous and if there is no evidence of dental disease, there is a reasonable likelihood that primary (nondental) sinusitis is present. In the horse the rostral maxillary sinus can be entered at a site 2.5 cm dorsal and 2 to 3 cm caudal to the rostral end of the facial crest. The caudal maxillary sinus is entered at a point 2.5 cm dorsal to the facial crest and 2 cm rostral to the medial canthus of the eye. After shaving and surgical preparation of the skin and subcutaneous placement of a small volume of local anesthetic, a stab incision is created through the skin and extended down to the periosteum. A small hole is then drilled through the bone with a Steinmann pin in a handheld chuck or a 14-gauge needle. A 14-gauge cannula is introduced into the sinus and, if necessary, a 5-French catheter can be inserted through the cannula to facilitate sample collection and lavage (see the Diseases of the Paranasal Sinuses section in Chapter 31 for horses and the Diseases of the Sinuses section in Chapter 31 for ruminants).

CATHETERIZATION. Catheterization of the guttural pouches via the pharyngeal orifice, either blindly or under endoscopic guidance, followed by aspiration or lavage, culture, and cytologic examination of aspirated contents, is helpful in the evaluation of horses with chronic purulent nasal discharge in which guttural pouch empyema is suspected or has been confirmed by radio­graphic or endoscopic examination. In horses with large accumulations of fluid exudate, voluminous drainage of pus both through and around the catheter may occur when the pouch is first catheterized. In horses with chronic guttural pouch infection accompanied by tenacious or inspissated exudate, lavage with 250 to 400 mL of sterile saline or Ringer solution facilitates sample collection.