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                                                                     EXHIBIT 4.3

                                 SONOSITE, INC.

                          AMENDMENT TO RIGHTS AGREEMENT



     This Amendment to Rights Agreement (this "Amendment") is made as of the
24th day of October 2001 by and between SonoSite, Inc., a Washington corporation
(the "Company"), and EquiServe Trust Company, N.A, a trust company organized
under the laws of the United States and having a principal place of business in
the state of New Jersey ("EquiServe"), the successor in interest to First
Chicago Trust Company of New York, a New York corporation ("First Chicago").

                                    RECITALS
                                    --------

     WHEREAS, the Company and First Chicago are parties to that certain Rights
Agreement dated as of April 6, 1998, and as subsequently amended on August 8,
2001 (the "Agreement"). Any capitalized terms not specifically defined herein
shall have the meanings ascribed to them in the Agreement.

     WHEREAS, First Chicago has the intent to cease operation of business and
EquiServe is its successor in interest.

     WHEREAS, the Company has approved the assignment to EquiServe of the
Agreement and all of First Chicago's rights and obligations thereunder.

     WHEREAS, the Company wishes for EquiServe to continue as the Rights Agent
pursuant to the Agreement.

     WHEREAS, the parties wish to amend the Agreement as provided herein.

                                    AGREEMENT
                                    ---------

     NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which is hereby acknowledged, the parties hereto agree as
follows:

     1.   The Agreement is amended as follows:

          a.   Section 2 of the Agreement is amended in its entirety and
replaced with the following:

               Section 2. Appointment of Rights Agent. The Company hereby
          appoints the Rights Agent to act as agent for the Company and the
          holders of the Rights (who prior to the Distribution Date shall also
          be the holders of the Common Stock) in accordance with the terms and
          conditions hereof, and the Rights Agent hereby accepts such
          appointment. The Company may from time to time appoint one or more
          co-Rights Agents as it may deem necessary or desirable upon ten days
          prior written notice to the Rights Agent. The Rights Agent shall have
          no duty to supervise and shall in no event be liable for the acts or
          omissions of any such co-Rights Agent. The term "Rights Agent" is
          being used herein to refer, collectively, to

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          the Rights Agent together with any such co-Rights Agents. In the event
          the Company appoints one or more co-Rights Agents, the respective
          duties of the Rights Agent and any co-Rights Agents shall be as the
          Company shall determine.

          b.   Subsection (c) of Section 21 of the Agreement is amended in its
entirety and replaced with the following:

               (c) The Rights Agent shall be liable hereunder only for its own
          gross negligence, bad faith or willful misconduct.

          c.   Section 22 of the Agreement is amended in its entirety and
replaced with the following:

               Section 22. Change of Rights Agent. The Rights Agent or any
          successor Rights Agent may resign and be discharged from its duties
          under this Rights Agreement upon 30 days' notice in writing mailed to
          the Company and to each transfer agent of the Common Shares or
          Preferred Shares by registered or certified mail and to the holders of
          the Rights Certificates by first-class mail. The Company may remove
          the Rights Agent or any successor Rights Agent upon 30 days' notice in
          writing, mailed to the Rights Agent or successor Rights Agent, as the
          case may be, and to each transfer agent of the Common Shares or
          Preferred Shares by registered or certified mail, and to the holders
          of the Right Certificates by first-class mail. If the Rights Agent
          shall resign or be removed or shall otherwise become incapable of
          acting, the Company shall appoint a successor to the Rights Agent. If
          the Company shall fail to make such appointment within a period of 30
          days after giving notice of such removal or after it has been notified
          in writing of such resignation or incapacity by the resigning or
          incapacitated Rights Agent or by the holder of a Right Certificate
          (who shall, with such notice, submit such holder's Right Certificate
          for inspection by the Company), then the registered holder of any
          Right Certificate may apply to any court of competent jurisdiction for
          the appointment of a new Rights Agent. Any successor Rights Agent,
          whether appointed by the Company or by such a court, shall be a
          corporation or trust company organized and doing business under the
          laws of the United States or of a state of the United States, in good
          standing, which is authorized under such laws to exercise corporate
          trust or stock transfer powers and is subject to supervision or
          examination by federal or state authority and which has, individually
          or combined with an affiliate at the time of its appointment as Rights
          Agent, a combined capital and surplus of at least $100 million
          dollars. After appointment, the successor Rights Agent shall be vested
          with the same powers, rights, duties and responsibilities as if it had
          been originally named as Rights Agent without further act or deed, but
          the predecessor Rights Agent shall deliver and transfer to the
          successor Rights Agent any property at the time held by it hereunder
          and execute and deliver any further assurance, conveyance, act or deed
          necessary for the purpose. Not later than the effective date of any
          such appointment, the Company shall file notice thereof in writing
          with the predecessor Rights Agent and each transfer agent of the
          Common Shares or Preferred Shares and mail a notice thereof in writing
          to the registered holders of the Right Certificates. Failure to give
          any notice provided for in this Section 22, however, or any defect
          therein, shall not


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          affect the legality or validity of the resignation or removal of the
          Rights Agent or the appointment of the successor Rights Agent, as the
          case may be.

     2.   Each party represents and warrants to the other party that it has full
power and authority to execute and deliver this Amendment and to perform the
transactions contemplated hereunder.

     3.   The terms and provisions of the Agreement, as amended hereby, shall
remain in full force and effect. All references to the "Agreement" contained
therein shall mean the Agreement, as amended by this Amendment.

     4.   This Amendment may be executed in one or more counterparts, all of
which shall be considered one and the same agreement.



                            [Signature Page Follows]


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     IN WITNESS WHEREOF, each of the parties hereto has caused this Amendment to
be signed by their respective officers duly authorized as of the date first
written above.

                                       SONOSITE, INC.


                                       By:  /s/ Michael J. Schuh
                                          --------------------------------------
                                       Name:  Michael J. Schuh
                                            ------------------------------------
                                       Title:  Chief Financial Officer
                                             -----------------------------------


                                       EQUISERVE TRUST COMPANY, N.A.


                                       By:  /s/ Thomas A. Ferrari
                                          --------------------------------------
                                       Name:  Thomas A. Ferrari
                                            ------------------------------------
                                       Title:  Senior Managing Director
                                             -----------------------------------

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