The epidemiology of plunging ranula in South Auckland

Estimate the incidence rate and provide basic descriptive epidemiologic characteristics of plunging ranulas in a multi-ethnic population.

Case series with chart review.

The study group comprised all Counties Manukau Health (CMH, Manukau City, Auckland, New Zealand) patients presenting to the CMH Department of Otolaryngology with a diagnosis of plunging ranula from January 2001 to December 2013, as recorded in the departmental case register. Non-CMH domicile patients were excluded. South Auckland comprised the base population, as serviced by CMH. The 2006 New Zealand census data was used for population demographics.

A total of 134 cases of plunging ranula were identified. The overall annual crude incidence rate was 2.4 per 100,000 person-years. The gender specific incidence rate for males was 3.2 per 100,000 (95% confidence interval [CI]: 2.5. 3.9) and for females was 2.0 per 100,000 (95% CI: 1.5, 2.6). The overall age-adjusted annual incidence rate was 2.6 per 100,000 (95% CI: 2.1, 3.0). The age-adjusted incidence was highest among Maori (6.7 per 100,000, 95% CI 4.9, 8.4), followed by Pacific Island (4.4 per 100,000, 95% CI 3.2, 5.6), Asian (0.7 per 100,000, 95% CI 0.2, 1.2), and European population (0.6 per 100,000, 95% CI 0.3, 0.8).

We have quantified for the first time the age-specific and age-adjusted incidence rates for plunging ranula by gender and ethnicity. The results show a likely underlying genetic predisposition for this condition, possibly with a superimposed environmental acquired factor relating to external, minor blunt trauma to the neck.

4. Laryngoscope, 126:2739-2743, 2016.