UPDATE 1-Intuitive Surgical Q4 revenue miss Street; shares tank

* Q4 rev below analyst estimates

* 2009 rev forecast below Street view * Shares fall as much as 18 pct

Jan 7 (Reuters) - Intuitive Surgical Inc (ISRG.O) reported lower-than-expected preliminary fourth-quarter revenue, and also forecast 2009 revenue below Wall Street expectations, sending its shares crashing as much as 18 percent after the bell.

While both accessory and service revenue for its robotic surgical systems increased by about 45 percent, sales of its main products such as the da Vinci systems rose by only 5 percent.

"Our system sales in the quarter reflect the challenging global economic and financial market environment," Chief Executive Lonnie Smith said.

For 2009, the company expects revenue to increase about 15 percent over expected 2008 sales of about $875 million. Analysts on average expect the company to post revenue of $1.10 billion, according to Reuters Estimates.

2008 fourth-quarter revenue was estimated at about $232 million, compared with analyst expectations of $255.08 million.

Shares of the Sunnyvale, California-based company's were trading down 14.3 percent at $101 in trading after the bell, after closing at $117.88 on Nasdaq Wednesday. (Reporting by Anuradha Ramanathan in Bangalore; Editing by Anthony Kurian) ((anuradha.ramanathan@thomsonreuters.com; within U.S. +1 646 223 8780; outside U.S. +91 80 4135 5800: Reuters Messaging: anuradha.ramanathan.reuters.com@reuters.net))