Hemostasis and transection of tissue

1. A laparoscopic cautery instrument comprising:

an elongate shaft that:

is sized and shaped for passage through a laparoscopic trocar port;

defines at least one lumen along its length; and

defines an aperture at a distal end of the shaft;

a handle coupled to the shaft and moveable with respect to the shaft;

an insulation ring that:

has a ribbon shape;

is formed at least in part by an electrical insulator;

extends in a loop emanating from the shaft distal end; and

is so operatively coupled to the handle as to be progressively expandable from and retractable into the shaft as the handle is moved with respect to the shaft, thereby increasing and decreasing the loop's size, respectively; and

a monopolar cautery wire that:

comprises an electrical conductor;

has connector ends extending from a proximal end of the shaft and through the shaft lumen to form a wire loop emanating from the shaft distal end;

is selectively operably coupled to the handle such that:

when coupled to the handle:

the wire loop is progressively expandable from and retractable into the shaft as the handle is moved with respect to the shaft, thereby increasing and decreasing the wire loop's size, respectively; and

the wire loop contacts an inward-facing side of the ring loop during such progressive expansion and retraction; and

when not coupled to the handle, at least one of the wire's ends is progressively retractable through the shaft, thereby decreasing the wire loop's size independently of movement of the ring loop.

2. The instrument of claim 1 , further comprising an electrical power source to which the connector ends of the monopolar cautery wire are so coupled as to apply monopolar current to the monopolar cautery wire.

3. The instrument of claim 1 , further comprising an electrical conductor affixed to the inward-facing side of the ring loop.

4. The instrument of claim 3 , further comprising an electrical power source to which the wire connector ends and the electrical conductor are so coupled as to apply bipolar current between the wire loop and the electrical conductor.

5. The instrument of claim 4 , wherein the electrical conductor comprises a pair of electrodes positioned at opposing locations of the ring loop.

6. The instrument of claim 4 , wherein the electrical conductor comprises a conductor loop extending along at least half of the inward-facing side of the ring loop.

7. The instrument of claim 1 , wherein a proximal portion of the wire is embedded in an electrical insulator.

8. The instrument of claim 1 , a distal portion of the wire loop is free of electrical insulator.

9. The instrument of claim 1 , wherein the insulation ring defines one or more apertures and a channel in fluid communication with the apertures.

10. The instrument of claim 9 , further comprising a suction source in fluid communication with the channel.

11. The instrument of claim 1 , further comprising a steering mechanism so coupled to the insulation ring as to permit deflection of the ring relative to the elongate shaft.

12. A laparoscopic cautery instrument comprising:

an elongate shaft that:

is sized and shaped for passage through a laparoscopic trocar port;

defines at least one lumen along its length; and

defines an aperture at a distal end of the shaft;

a monopolar cautery wire that:

comprises an electrical conductor; and

has connector ends extending from a proximal end of the shaft and through the shaft lumen to form a wire loop emanating from the shaft distal end, and wherein at least one of the wire's ends is progressively retractable through the shaft, thereby decreasing the wire loop's size;

an electrical conductor positioned at least in part proximate the monopolar cautery wire; and

an electrical power source to which the wire connector ends and the electrical conductor are coupled, the electrical power source being operable in two modes such that:

in a first mode, the electrical power source delivers monopolar current through the monopolar cautery wire and no current through the electrical conductor; and

in a second mode, the electrical power source delivers bipolar current between the monopolar cautery wire and the electrical conductor.

13. The instrument of claim 12 , wherein the electrical conductor comprises a pair of electrodes positioned at opposing locations.

14. The instrument of claim 12 , wherein the electrical conductor comprises a conductor loop.

15. The instrument of claim 14 , further comprising an insulation ring that:

has a ribbon shape;

is formed at least in part by an electrical insulator;

extends in a loop emanating from the shaft distal end; and

is so operatively coupled to the handle as to be progressively expandable from and retractable into the shaft as the handle is moved with respect to the shaft, thereby increasing and decreasing the loop's size, respectively;

wherein the conductor loop extends along at least half of an inward-facing side of the ring loop.

16. A laparoscopic cautery method comprising:

advancing the instrument of claim 1 through a laparascopic trocar so that the shaft distal end approaches a surgical site requiring cautery;

expanding the ring and wire;

fitting the ring and wire over an anatomical structure so that the ring loop and wire loop surround a portion of the anatomic structure;

applying monopolar current to the monopolar cautery wire; and

pulling at least one of the wire's ends, while the wire is not coupled to the handle, thereby:

retracting the wire;

pulling the wire through the surrounded anatomic structure; and

severing the anatomic structure by cautery.

17. The method of claim 16 , wherein the instrument further comprises an electrical conductor affixed to the inward-facing side of the ring loop, and the method further comprises applying bipolar current between the wire and the electrical conductor.

18. The method of claim 16 , wherein the insulation ring defines one or more apertures and a channel in fluid communication with the apertures, and the method further comprises suctioning fluid away from the surgical site.

19. The method of claim 16 , wherein fitting comprises so snugly cinching the ring about the portion of the anatomic structure as to cause severed portions of the anatomic structure to be held by the ring following the severing.

20. A laparoscopic cautery method comprising:

advancing the instrument of claim 12 through a laparascopic trocar so that the shaft distal end approaches a surgical site requiring cautery;

expanding the wire;

fitting the wire over an anatomical structure so that the wire loop surrounds a portion of the anatomic structure;

applying bipolar current between the wire and the electrical conductor to cauterize another portion of the anatomic structure or another anatomic structure;

applying monopolar current to the monopolar cautery wire; and

retracting the wire, thereby:

pulling the wire through the surrounded anatomic structure; and

severing the anatomic structure by cautery.