Medical treatment endoscope with a positioning mechanism

1. A medical treatment endoscope comprising:

an insertion portion which has a lumen formed along a longitudinal axis of the insertion portion and is configured to be inserted into a body cavity;

a lateral opening portion which extends in a lateral surface of the insertion portion, from a distal end surface of the insertion portion to a proximal end side of the insertion portion, the lateral opening portion having a lateral opening which extends from the distal end surface of the insertion portion to the proximal end side of the insertion portion and communicates with the lumen;

an elastic member which is provided in an inner wall of the lumen at a position separated from an edge of a proximal end of the lateral opening portion in a direction toward the distal end surface of the insertion portion, wherein the elastic member includes a first end fixed to a concave portion of the inner wall of the lumen and a second end configured to be capable of protruding from and accommodated into the concave portion of the inner wall of the lumen in a radial direction of the lumen; and

a tubular arm which includes a bendable bending part provided at a distal end side of the tubular arm, the tubular arm being inserted through the lumen and capable of holding a treatment tool used for treating a treatment target tissue so that the treatment tool is capable of being inserted through the tubular arm, wherein

in a first state in which at least part of the elastic member is pressed by an arm distal end part of the tubular arm which is inserted through the lumen, at least part of the elastic member is accommodated into the concave portion of the inner wall of the lumen; and

in a second state in which the arm distal end part of the tubular arm is between the elastic member and a proximal end edge of the lateral opening portion, and the bending part is bent, the second end protrudes from the inner wall of the lumen inward in the radial direction of the lumen such that the first end and the second end are arranged in that order from the distal end surface toward the proximal end of the insertion portion.

2. The medical treatment endoscope according to claim 1 , further comprising an image capturing unit which is provided at a distal end of the insertion portion.

3. The medical treatment endoscope according to claim 1 , wherein

the bending part of the tubular arm is provided with a first bending part and a second bending part which continues to the first bending part at a proximal end side of the bending part, and

in the second state, the second bending part is positioned between the elastic member and the proximal end edge of the lateral opening portion, and the tubular arm is engaged with the insertion portion so that movement of the tubular arm relative to the insertion portion in a longitudinal axis direction and a circumferential direction around a longitudinal axis of the insertion portion is restricted.

4. The medical treatment endoscope according to claim 3 , wherein

a pair of the lumens are disposed symmetrically in a radial direction of the insertion portion with respect to a center axis of the insertion portion,

a pair of the lateral opening portions are disposed symmetrically in the radial direction of the insertion portion with respect to the center axis of the insertion portion,

a pair of the elastic members are disposed symmetrically in the radial direction of the insertion portion with respect to the center axis of the insertion portion, and

a pair of the tubular arms are disposed,

in the first state, at least part of each of the pair of the elastic members is accommodated into the inner wall of the corresponding lumen, and

in the second state,

each of the second bending parts of the pair of the tubular arms is bent so that each of the second bending parts of the pair of the tubular arms is positioned between the corresponding elastic member and the proximal end edge of the corresponding lateral opening portion,

the pair of the elastic members protrude from the inner walls of the pair of the lumens outward in the radial directions of the lumens, and

the pair of the tubular arms are engaged with the insertion portion so that movement of each of the pair of the tubular arms relative to the insertion portion in the longitudinal axis direction and the circumferential direction around the longitudinal axis of the insertion portion is restricted.

5. The medical treatment endoscope according to claim 4 , wherein

the distal end part of each of the pair of the tubular arms is formed such that thickness of the distal end part becomes thinner in an elongated direction toward a distal end of each of the pair of the tubular arms, and

in the first state, at least part of one of the pair of the elastic members is pressed to be accommodated into the concave portion of the inner wall of the corresponding lumen by the distal end part of the corresponding tubular arm.

6. The medical treatment endoscope according to claim 4 , wherein the distal end part of each of the pair of the tubular arms is formed in a tapered shape such that the thickness of the distal end part becomes thinner gradually in the elongated direction toward a distal end of each of the pair of the tubular arms.