PRESENTING SIGNS

Dacryocystitis is inflammation within the lacrimal sac and nasolacrimal duct. Affected animals are presented with ocular discharge – usually this is mucopurulent in nature. Alternatively, a unilateral red eye due to conjunctivitis with conjunctival hyperaemia and a variable discharge can be the initial presenting sign. It is quite common for the patient not to be brought to the surgery when the signs first develop, but only when they change and become persistent with a chronic mucopurulent discharge. The discharge is most copious at the medial canthus and reforms frequently following cleansing and removal by the owner. Sometimes the medial canthal skin is erythematous or swollen and the patient is uncomfortable. The condition is rarely encountered in cats but occurs occasionally in dogs and quite frequently in rabbits. The latter are discussed separately in Chapter 19.

CASE HISTORY

The patient may have history of a wet eye 1–3 weeks prior to the development of the chronic discharge and the discharge itself could have changed from serous to purulent in nature. A previous conjunctivitis or even removal of a conjunctival foreign body might have occurred. The patient can be any age or breed. Although normally unilateral in dogs, the condition can be bilateral on occasion (this is more common in rabbits, as discussed in Chapter 19).

CLINICAL EXAMINATION

General clinical examination is usually normal in dogs. Ophthalmic examination reveals a unilateral ocular discharge centred around the medial canthus (Figure 18.1). Evidence of pain with blepharospasm or self-trauma though rubbing is variable. Conjunctival hyperaemia is normally present in the nictitans conjunctiva but can be widespread. Schirmer tear test readings are normal. No corneal disease is usually present and the rest of the ocular examination is unremarkable. On cleaning the discharge (after taking a swab for culture and sensitivity testing and cytology for Gram stain) gentle pressure at the medial canthus will often result in the appearance of further purulent material at the nasolacrimal punctae (often just the lower one but sometimes the upper as well). Fluorescein passage to the nostril is absent on the affected side (Figure 18.2); remember to compare both sides, and also that false negatives are common.

Figure 18.1 Right eye of a 5-year-old golden retriever with mucopurulent discharge at medial canthus plus elevation and hyperaemia of nictitans membrane.

Figure 18.2 Another golden retriever with a blocked left nasolacrimal duct – notice the fluorescein at the right nostril but not the left, while it pools below the left eye.

CASE WORK-UP

Nasolacrimal duct flushing is necessary to reach a definitive diagnosis and to assist with establishing the underlying aetiology, if possible. Often this can be done conscious but sedation or general anaesthesia will be required if the condition is painful or if further diagnostic tests are to be undertaken. Some purulent material can be flushed between upper and lower punctae (depending which one is cannulated). Initially there is likely to be resistance to the passage of saline down the nasolacrimal duct to the nose; however, with persistence, and using steadily increasing pressure, it might be possible to establish drainage. Purulent material should be collected from the nasal ostium for bacterial culture and sensitivity testing. If the nasolacrimal flush is not successful under topical anaesthesia or sedation, then the patient should undergo general anaesthesia. Sometimes flushing from one punctum to the other in dogs will lead to the expulsion of fragments of foreign material (most commonly pieces of grass awn) which will suggest similar material down the nasolacrimal duct itself. Care should be exercised to prevent damage to the duct by overzealous flushing. If sharp pieces of foreign material are present, then exerting excessive pressure could result in rupture of the duct. If any bloodstained material is encountered, then further attempts at flushing should be discontinued.

If it is not possible to establish drainage, then there are several options available. The first is to attempt retrograde flushing. This is really only feasible in medium and large sized dogs. The nasal ostium of the duct is located on the ventrolateral nasal meatus approximately 1 cm inside the external meatus. An otoscope or small vaginal speculum is useful to provide magnification and illumination when trying to locate the opening. Initial cannulation with monofilament nylon (e.g. 2/0) is achieved and this is passed up the duct as far as possible – occasionally it is stiff enough to dislodge any inspissated material as the duct widens as it approaches the lacrimal sac. A narrow gauge catheter can be introduced over the nylon thread into the nasal ostium such that retrograde flushing can be attempted.

If retrograde cannulation or flushing is not feasible, then further case work-up will involve radiography – both plain and contrast studies (dacryocystorhinography). Plain radiographs might reveal bony fractures or neoplastic processes which were not clinically noted. Periodontal disease involving the upper premolars or canine teeth might be present, leading to a localized inflammation in the nasolacrimal duct and subsequent obstruction. Contrast studies, using water-soluble contrast agents, can locate the exact blockage and help identify whether surgical intervention is feasible. In dogs, small amounts (1–2 ml) of contrast are injected into the upper punctum while holding the lower one closed, such that the contrast material is forced down the duct. Care should be taken to ensure that no excess contrast material is spilled as this could easily confuse interpretation of the radiographs. It is sensible to take a lateral radiograph after injecting the affected side, followed by dorsoventral or intraoral views after injecting both sides for comparison. Cystic dilations can be delineated by this method, as well as locating radiolucent foreign material. If the blockage is anterior – within the lacrimal bone for example – then referral for surgical removal can be considered.

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