Cognitive routing coupled with cooperative spectrum sensing in multi-hop Cognitive Radio Ad Hoc Network (CRAHN) is investigated. Recognizing the spectrum dynamics and the problems of hidden terminal and shadow fading in CRAHNs, we propose an opportunistic routing protocol that exploits a Dual-stage Collaborative Spectrum Sensing (DCSS) scheme to improve the accuracy of spectrum available opportunity due to the effects of Primary Users' (PUs) activity. The simulation results indicate that routing access opportunity and breakage probability using the proposed DCSS, when compared to the Single Collaborative Spectrum Sensing (SCSS) scheme and Non-Cooperation Sensing (NCS) scheme, is closer to the practical value of routing establishment. Besides, it is observed that the number of available channels and hop counts also affect the success rate of routing establishment.