An Endoscopic Tour through the Equine Body

 

Endoscopic examinations allow for visualization of various anatomical systems that cannot be examined from the outside of the horse. This technology is minimally invasive, and the examination can usually be performed with either minimal or no sedation.

The endoscope gives the veterinarian the ability to watch the body systems in motion – doing the jobs they are intended to do. This allows the veterinarian to assess the ability of a system to function and identify abnormalities that may interfere with the horse’s health or performance. The respiratory system, the gastrointestinal system, and the urogenital ystem are well suited to examination with the flexible endoscope.

The endoscope may also be used for sample collection, treatments, and breeding. Biopsy and fluid samples are collected through a separate portal allowing the examiner to visualize the samples being collected. Certain surgical procedures and treatments may be performed through the endoscope.

Respiratory system

The most common reasons to endoscopically examine a portion of the horse’s respiratory tract are respiratory noise, nasal discharge, foul odor, persistent cough, throatlatch swelling, and exercise intolerance. Any of these symptoms can indicate a potentially serious problem that can affect the horse’s health and level of performance.

Endoscopic examination of the respiratory system begins with the upper airway. The upper airway of the horse consists of the nares, the nasal passages, and the pharynx. The nasal passages are responsible for a number of functions including warming and filtering of air. Horses are “obligate nose breathers” – meaning that they cannot breathe through their mouth. All the air a horse breathes must go through their nasal passages. The pharynx is the “transfer station.” It is responsible for passage of air from the upper airway into the lower airway and for insuring that foodstuff goes into the esophagus and not into the trachea.

PIC #1& #2 will be added soon

Portions of the horse’s lower airway that are easily accessible for endoscopic examination are the trachea and bronchi. The trachea and the bronchi are both responsible for transport, filtering and warming of air on the way to the lungs where the oxygen from the air is processed for use by the body.

Many abnormalities of the respiratory tract can be identified using endoscopy. A few of the more common problems that can be identified during an endoscopic evaluation are outlined below.

The most common problem identified involving the nasal passage is some type of obstruction. Even minor obstruction of the nasal passages may cause exercise intolerance in the horse, especially if the horse is expected to perform at a high level of speed or endurance. If even one nasal passage is significantly obstructed, the exercise intolerance experienced by the horse can be dramatic. Tumors are the most common, but not the only, cause for nasal passage obstruction.

The pharynx is the focal point for most respiratory endoscopic examinations. The most common complaint that prompts an endoscopic evaluation is “respiratory noise.” Abnormal respiratory noise is caused by turbulence in air flow as the horse breathes. There are a number of anatomical abnormalities that cause the turbulence responsible for respiratory noise – the most common are outlined in the table below, and diagrams show the anatomical abnormalities.

Anatomical abnormality	Description of noise
Dorsal Displacement of the Soft Palate (DDSP)	Gurgling with exercise - both inspiration and expiration
Epigolittic Entrapment	Noise on both inspiration and expiration, but primarily expiration
Laryngeal hemiplegia	Primarily inspiratory noise – high pitched “roarer"

Although each abnormality has a tendency to cause a particular type of respiratory noise, there is enough variability in the noise created that endoscopic evaluation is necessary for an accurate diagnosis. Anything that disrupts normal air flow can cause noise that can mimic the “classic” abnormalities – swelling of any type, tumors, masses caused by allergic reaction. In addition, some respiratory noises – especially expiratory noises – may originate from the lower airway.

PIC #3, #4, and #5 will be added soon

Abnormal nasal discharge can originate from the upper or lower airways. Discharge originating from the upper airway usually comes from one of two areas – the sinuses or from the guttural pouches. These anatomical areas are shown in diagrams below. Sinus infections usually produce a very foul smelling discharge that may appear at one or both nostrils. These horses usually do not show exercise intolerance, but may show signs of “head shaking” or other symptoms. The horse’s guttural pouches are the equivalent of the human’s Eustachian tubes and, just like ear infections in people, are a fairly common occurrence. The nasal discharge in guttural pouch infections may be unilateral (one nostril) or bilateral (both nostrils).

Bloody nasal discharge can originate from a few sources. Any blow to the head can cause hemorrhage from a sinus – which is the least significant cause of bloody nasal discharge. Other causes are outlined in a table below.

Causes	Source
Exercise Induced Pulmonary Hemorrhage (EIPH)	Rupture of capillaries (small blood vessels) in the lungs. Usually in horses that perform at high speed.
Ethmoid hematoma	Tumor of the ethmoid turbinates (see anatomical diagram)
Fungal guttural pouch infection	Guttural pouch infection which potentially involves the carotid artery that runs through the guttural pouch. Potentially fatal from a bleed out.

The lower airway (trachea and lungs) is also a common focus for endoscopic examination. Usually the complaint that prompts an endoscopic evaluation of the lower airway is either chronic cough or exercise intolerance. The complaint of “exercise intolerance” includes, and is commonly described as, a decrease in level of performance. Either of these symptoms can be infectious, irritation or allergic in nature. Treatment varies dramatically depending on the cause, so endoscopic evaluation in addition to various laboratory tests can be invaluable in getting to the appropriate treatment option.

Gastrointestinal tract

The portions of the gastrointestinal tract that are available for endoscopic examination are the esophagus and the stomach. The esophagus may require endoscopic examination for evaluation of ulcers or obstruction (choke).

Choke is a condition in the horse where a foreign object of some sort is causing obstruction of the esophagus. The horse’s symptoms include copious nasal and oral discharge (the common observation is that the horse is “throwing up”), coughing, not eating, and possibly mildly colicky. Often the choke is temporary and the horse resolves it himself within a few minutes. If the choke does not resolve quickly, the horse will need to be treated by a veterinarian. Difficult cases of choke may require endoscopic examination of the esophagus to determine the appropriate treatment for the horse.

PIC #6 & #7 will be added soon

Examination of the stomach may be recommended in cases of mild colic, weight loss, anorexia or poor performance. Some horses exhibit behavioral problems when they are dealing with gastric ulcers, so there are many possible symptoms that can indicate a clinical problem with the horse’s stomach. Recent studies suggest that up to 65% of race horses and endurance horses have gastric ulcers. Endoscopic examination is the best diagnostic tool available to the veterinarian when symptoms indicate a possible stomach problem.

Urogenital System

The bladder of the horse is easily examined with the endoscope. The entire urethra, bladder and both ureters can be examined in both the mare and gelding or stallion.

Symptoms that warrant endoscopic examination of the urinary tract include straining to urinate, urinating small amounts frequently, pain on urination, and bloody urine. Stallions that exhibit a reluctance to ejaculate or have blood in their ejaculate may benefit from an endoscopic examination of their urethra. Problems that can be diagnosed by endoscopic evaluation include tumors, bladder stones, urethral infection, urethral tear, and renal (kidney) hemorrhage or infection.

The mare’s uterus is also very accessible for evaluation by endoscopy. Although there are a number of useful diagnostic tools for use in determining problems with the mare’s uterus, endoscopic examination allows for a totally different type of evaluation. At times, evaluation of a problem mare’s uterus by conventional methods yields either no significant information or conflicting information. Endoscopic evaluation gives the veterinarian an additional and completely different method. Endoscopic breeding allows semen be deposited at the opening of the oviduct to maximize fertility.

PIC #8 to be added soon

Mares that have had problems conceiving and/or carrying to term can be extremely frustrating for both veterinarian and owner. When gathering information on these mares there are times that an endoscopic examination will be extremely important. A few of the possible scenarios where an endoscopic evaluation will help give an answer when other diagnostic methods fail are outlined below.

Problem	Traditional diagnostics	Endoscopic evaluation
Subclinical or sectional infection	Cytology: inflammatory Culture: positive or negative Ultrasound: +/- edema	Focal plaques (isolated, scattered)
Adhesions/scarring	Culture/Cytology: negative Ultrasound: slight changes in tissue density	Visualization of adhesions
Fetal remnants	Cytology: inflammatory Culture: positive or negative Ultrasound: small bright white flecks in uterus (bone)	Visualization of fetal remnants

PIC #9 to be added soon

 

Endoscopy is a very valuable tool for diagnosis and treatment of respiratory, gastrointestinal and urogenital disorders of the horse.  Endoscopic images may be stored for future comparisons and follow-up.  Please feel free to contact our office with any questions.