Dacrocystography

Introduction

A dacrocystogram is a radiographic examination of the nasal lacrimal duct(s) following administration of a contrast medium into the duct(s).

Indications

• Lacrimal duct obstruction/stricture

Contra-indications

• non-consent by patient to procedure
• contrast media or iodine allergy
• pregnancy (risk is minimal but patient may wish to delay procedure)

Anatomy

The American Journal of Managed Care, 14: S079-S087 <a class="external" href="http://www.ajmc.com/supplement/managed-care/2008/2008-04-vol14-n3Suppl" rel="nofollow" target="_blank">April 2008</a>Number 3 Suppl

Tears (lacrimal fluid) are produced by the lacrimal gland which is located at the supero-lateral aspect of the orbit. Drainage of the lacrimal fluid is achieved by the lacrimal canaliculi, lacrimal sac, and nasolacrimal duct. The lacrimal fluid drains from the nasolacrimal duct into the nasal cavity via the inferior meatus of the cavity.

adapted from original photograph by <a class="external" href="http://commons.wikimedia.org/wiki/File:Lacrimal_punctum.jpg" rel="nofollow" target="_blank">Diogo Melo Rocha</a>

"The lacrimal canaliculi, one in each eyelid, commence at minute orifices, termed puncta lacrimalia (or lacrimal punctum, or lacrimal point), on the summits of the papillae lacrimales, seen on the margins of the lids at the lateral extremity of the lacus lacrimalis. There are two lacrimal puncta in the medial (inside) portion of each eye which in turn connect to the lacrimal sac." <a class="external" href="http://www.wikidoc.org/index.php/Lacrimal_punctum" rel="nofollow" target="_blank">(www.wikidoc.org)</a>

Preparation

• patient identification (3 'C's- correct patient, correct side, correct procedure)

• completed consent form
• no diet restrictions
  
• collect/review relevant previous imaging for ease of access prior to procedure

Technique

	The patient lies supine on the fluoroscopy table with their head in a reverse occipito-mental position. Sandbags on either side of the patient's head or some other immobilisation devise will assist, particularly if a subtraction technique is employed. Select a small field of view and fine focus Select an acquisition rate (1 frame per 2 seconds) select subtraction for spot imaging (DSI) a preliminary/scout image may be required anaesthetic eye drops are used for patient comfort a fine cannula is inserted into the puncta of each eye, then the eye is closed and the catheter taped to the patient's cheek It may be necessary to dilate the puncta to facilitate insertion of the cannula It is important to remind the patient of the importance of holding their head still just prior to starting the subtraction acquisition run After the mask is acquired, ask the radiologist to commence injection A drainage image can be taken after 15 minutes if considered necessary
	Unilateral dacrocystogram demonstrating a normal lacrimal duct Subtraction has been utilised to good effect Field of view is too generous- could have been coned more tightly minimal reflux into superior lacrimal canal
	Bilateral dacrocystogram with subtraction Normal lacrimal duct on the left Slower flow of contrast on the right (this may not be pathological- may reflect partly dislodged catheter- not the amount of extravisated contrast medium on the right) demonstrated right duct appears normal reflux into superior lacrimal canal on right perfect X-ray beam collimation adequate subtraction
	Bilateral dacrocystogram with subtraction excellent X-ray beam collimation effective subtraction reflux into superior lacrimal canal on right
	Unilateral injection abnormal pooling of contrast proximally excellent beam collimation
	Bilateral dacrocystogram without subtraction Delayed drainage image abnormal accumulation of contrast on the left Compare this unsubtracted image with the subtracted image above
	Unilateral injection Subtraction technique minimal contrast filling of right lacrimal sac contrast reflux into superior lacrimal canal

Contrast or Subraction Artifact?

It will not always be clear whether you have demonstrated contrast filling or subtraction artifact

	The consistency of the arrowed structure and its similarity to the other subtraction artifacts suggests that it is not contrast medium
	It is likely that this particular subtraction artifact could be removed at the time of the subtraction procedure even if it was at the expense of the subtraction through the remainder of the image.
	The radiographer may have to make decisions about which part of the image should be the focus of the subtraction. Try not to achieve a good subtraction result in a part of the image that is not relevant.

Nuclear Medicine Lacrimal Scan

Dacrocystogaphy is often performed in conjunction with a radionuclide lacrimal study (Lacrimal dacryoscintigraphy). This is the same patient as shown above. When the findings of the two studies correlate well, there can be additional confidence in the results.

Technique Notes

• The radiologist may choose to image the two sides separately- it is preferable to inject both sides at the same time

• It is normal practice to image the affected and unaffected sides.

• Collimate the X-ray beam to include the orbits superiorly and laterally and the maxillary paranasal sinuses inferiorly

• A sialogram needle (metal or plastic tip) can be used for cannulation of the puncta (16 gauge or similar)

• It is usually not tenable for the patient to hold their breath during the DSI subtraction acquisition sequence- with respiration, the effectiveness of the subtraction will vary

• If the patient moves during the acquisition sequence, it may be possible to select a new mask from the end of the sequence.

• Dacrocystogram protocol may include adjunct nuclear medicine study

• Maximum detail achieved with selection of fine focus (smallest focal spot size)

• A focused spotlight can be a useful aid for the radiologist in locating the lacrimal punctum

• inferior punctum is often easier to canulate

• catheter should not be inserted too far into the canaliculus- need to be able to see if the contrast refluxes out the other lacrimal canal.
  

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