Pressure Gradient discretisation in MAC curvilinear grids
 

Hi everybody,
I'm writing my FV code for incompressible NS on general curvilinear MAC grids. In cartesian formulation the pressure gradient at shifted cells faces only involves the pressure values of the 2 corresponding adjacent cells but in general coordinates surrounding cells are also involved meaning that when I'm near the boundaries the stencil is large enough to include extra boundary cells. Do I have to assign some sort of BC for the pressure here (and in case which?) or use a different discretisation for gradient that only involves interior cells?

Thank you in advance =)
JODO