Mo. Rev. Stat. § 536.100
Any person who has exhausted all administrative remedies provided by law and who is aggrieved by a final decision in a contested case, whether such decision is affirmative or negative in form, shall be entitled to judicial review thereof, as provided in sections 536.100 to 536.140, unless some other provision for judicial review is provided by statute; provided, however, that nothing in this chapter contained shall prevent any person from attacking any void order of an agency at any time or in any manner that would be proper in the absence of this section. If the agency, other than the administrative hearing commission or any board established to provide independent review of the decisions of a department or division that is authorized to promulgate rules and regulations under this chapter, fails to issue a final decision in a contested case within the earlier of:
(2) One hundred eighty days after the receipt by the agency of a written request for the issuance of a final decision,
then the person shall be considered to have exhausted all administrative remedies and shall be considered to have received a final decision in favor of the agency and shall be entitled to immediate judicial review as provided in sections 536.100 to 536.140 or other provision for judicial review provided by statute.
(L. 1945 p. 1504 § 10, A.L. 2005 H.B. 576)