Various diagnostic procedures and devices are used to perform imaging studies, mucus flow studies, air/gas flow studies, anatomic dimension studies, endoscopic studies and transillumination studies. Devices and methods for visually confirming the positioning of a distal end portion of an illuminating device placed within a patient include inserting a distal end portion of an illuminating device internally into a patient, emitting light from the distal end portion of the illuminating device, observing transillumination resulting from the light emitted from the distal end portion of the illuminating device that occurs on an external surface of the patient, and correlating the location of the observed transillumination on the external surface of the patient with an internal location of the patient that underlies the location of observed transillumination, to confirm positioning of the distal end portion of the illuminating device.