Guttural Pouch Empyema
Introduction
Guttural pouch empyema is a the infection and accumulation of purulent material within the guttural pouch (GP). It most commonly occurs secondary to one of the following:
- URT infections, especially pathogenic Streptococcus equi equi - the horse can be an asymptomatic carrier
- Retropharyngeal abscess
- Trauma (e.g. stylohyoid fracture)
As the purulent material accumulates, the GP distends - forming a palpable, fluctuating visible swelling behind the jaw. This can be seen as a fluid line in standing lateral radiograph of guttural pouches. The pouches can be drained by catheter or surgically. Chronic cases may develop chondroids (inspissated pus with the appearance of 'cottage cheese')
Clinical Signs
Common clinical signs of guttural pouch empyema:
- Firm retropharyngeal swelling
- Purulent nasal discharge
- Respiratory noise
- Dysphagia
- Lymphadenopathy of local lymph nodes
Diagnosis
The history and clinical signs may be suggestive of GP empyema but it can be confirmed by one of the following methods:
Endoscopy
Endoscopy of the GP should show purulent material and tympanitis. Chondroids may be seen if the infection is chronic.
Radiography
Standing lateral radiographs of the skull should show retropharyngeal swelling and thickening of the ventral wall. The presence of pus is confirmed by fluid lines across the guttural pouch and chondroids are visible as multiple small opacities. Any fracture or osteomyelitis should also be visible.
Culture
Swabs should be taken from the guttural pouch and cultured. This can confirm the origin of infection and guide any antibiotic therapy.
Treatment
In cases of GP empyema, the guttural pouches should be drained and lavaged daily with copious amounts of water, sterile saline or dilute antiseptic administered by indwelling Foley catheters until the infection resolves. The horse should be fed from the ground to encourage drainage of the pouches.
If chondroids are present they must be removed by one of two methods:
- 1) Endoscopic snare removal - where individual chondroids are grabbed and removed via endoscopy. Lavage should not be attempted prior to this as it will soften the chondroids, making them more breakable and harder to remove. Although non-invasive it is a time consuming process as only one chondroid can be removed at a time.
- 2) Surgical removal using the Modified Whitehouse technique. This involves entering the guttural pouches through the floor of the medial compartment following an incision ventral to the linguofacial vein. It requires simultaneous endoscopy. Once all the chondroids have been removed and the GP lavaged, the wound should be left open to heal by second intention. The disadvantages of this procedure are that the lateral compartment is hard to reach, and if the case is chronic them the GP wall may be very thickened and hard to penetrate. As it is an invasive procedure, recovery time is also longer and it is necessary to use good surgical technique to avoid important structures.
If the infection is found to be Strep equi equi then penicillin beads should be place in the guttural pouches and oral trimethoprim sulphate should be given to clear the infection. Otherwise antibiotic treatment should not be necessary.
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References
Dixon, P (1991) Swellings of the head region in the horse In Practice 1991;13:257-263
Mair, TS & Divers, TJ (1997) Self-Assessment Colour Review Equine Internal Medicine Manson Publishing Ltd
RVC staff (2009) Respiratory System RVC Intergrated BVetMed Course, Royal Veterinary College
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