Rhythmic electrical signal is present in the human small intestine and may be recorded using surface electrodes. The surface electrical recording of the small intestine (SERSI) contains severe interferences which obscure the electrical signal of the small intestine. An adaptive system is proposed in this paper for the enhancement of small intestinal signal. To obtain better performance, adaptive signal enhancement is performed in transform domain using discrete cosine transform (DCT). A fast recursive algorithm is developed for the calculation of running DCT. The computational complexity of the proposed recursive algorithm is only 2/N (N:length of adaptive filter) of the direct calculation of the running DCT. No pagination in original publication.