Weakness in the US pathology market is causing headaches for Sonic Healthcare (ASX:SHL), which is grappling with the deteriorating outlook for the domestic pathology sector after government funding cuts and deregulation.

A number of US rivals including Quest Diagnostics, have reduced their earnings guidance following a drop in the number of patient visits to doctors.

Sonic downgraded its full year earnings guidance by 8 per cent earlier this year.

Sonic recently turned its attention offshore by making a number of acquisitions as it is tries to mitigate the impact of Australian government funding cuts.

But the acquisition of international companies is now believed to have slowed because of concerns about the Australian healthcare outlook.

Sonic Healthcare reported a $171 million net profit in 2009, which was down on the result the financial year before.