Computed Tomography: Dacryocystography

A century ago, in 1909, Ewing performed the first dacryocystography (DCG) to visualize the lacrimal abscess cavity and passages using X-rays. He used bismuth subnitrate as the contrast material. However, the surrounding bone and soft tissue details were not discernible in this DCG. A modification of this technique, namely, digital subtraction, made the lacrimal passage stand out but failed to show the surrounding details. Nevertheless, details of the common canaliculus and nasolacrimal duct could be seen, making it a useful tool in cases with stenosis. Using X-rays was a disadvantage due to the dangers of radiation exposure. This was overcome to some extent by the advent of computed tomography dacryocystography (CT-DCG) in 1990. This allowed the documentation of the bone and soft tissue anatomy and the lacrimal drainage system (LDS). The most important use of CT-DCG was in complex nasolacrimal duct obstructions (NLDO) in craniofacial trauma. It is also useful in diagnosing and monitoring tumors and masquerades involving the LDS. Magnetic resonance dacryocystography (MR-DCG) was first performed in 1993 to study the functional and morphological aspects of the lacrimal pathways. Although the adverse effects of radiation exposure were nullified, the high cost, longer acquisition time, and motion artifacts were the limitations. CT-DCG is currently the most used technique because of its distinct advantages in delineating details of the LDS, adjacent bone and soft tissue anatomy, low acquisition time, and relatively low radiation exposure.