Oblong endoscope sheath

An endoscope sheath comprising:

• a sheath having:
• a proximal end,
• a distal end, and
• a tube extending between the proximal end and the distal end with a single passage;
• wherein the sheath is configured to receive all or a portion of an endoscope and provide inside the tube a conduit for communicating fluid between the proximal end of the sheath and the distal end of the sheath when the endoscope is inserted inside the sheath, and
• wherein the tube has a non-cylindrical shape that has a cross-section with a circular portion having a diameter substantially matching a diameter of the endoscope and one or more tangent portions that have one or more segments that are tangent to the circular portion at one or more points,
• wherein at least a part of a side of the endoscope contacts the circular portion when the endoscope is inserted into the tube, so that the conduit is formed between the side of the endoscope and inside of the tube opposite the circular portion in which the endoscope contacts, and
• wherein a cross-sectional shape of the sheath that is orthogonal to a longitudinal axis is varied along a length of the sheath.