A swallowable in-vivo device comprising a shell formed with at least one inlet extending across a shell wall and configured for allowing ingress of fluid at least into the shell the shell accommodates therein a lateral flow (LF) arrangement configured for absorbing the fluid the LF arrangement comprises a test zone configured for coming into contact, in-vivo, with a predetermined N substance present in the fluid or a compound comprising the substance, thereby causing a change in at least one property of the test zone the shell further accommodates a sensor configured for sensing, in-vivo, the at least one property, at least when changed by interaction with the fluid the LF arrangement has at least one curved segment, and at least one exposure portion juxtaposed with the inlet, configured for absorbing the fluid passing through the inlet into the shell.
