A system for treating a patient comprising: an elongate shaft comprising a distal portion, wherein the elongate shaft is constructed and arranged to be introduced into the duodenum of the patient; an expandable reservoir positioned on the elongate shaft distal portion, wherein the expandable reservoir is constructed and arranged to receive a first fixed amount of ablative fluid and to deliver a first thermal dose of energy to a first portion of target tissue; and a fluid delivery assembly in fluid communication with the expandable reservoir, wherein the fluid delivery assembly is constructed and arranged to deliver the first fixed amount of ablative fluid to the expandable reservoir; an ablative fluid reservoir fluidly connected to a first input of a manifold having an output for fluid attachment to a pumping assembly such that liquid provided by the ablative fluid reservoir can be directed through the manifold to the expandable reservoir and an evacuation reservoir fluidly connected to a second input of the manifold, the manifold being configured to selectively connect the evacuation reservoir to the pumping assembly, such that the pumping assembly can propel fluid in a reverse direction into the evacuation reservoir to remove fluid from the expandable reservoir, wherein the first fluid reservoir is configured to provide at least the first fixed amount of ablative fluid to the fluid delivery assembly and the second fluid reservoir is configured to receive at least the first fixed amount of ablative fluid after the delivery of at least the first thermal dose of energy, and wherein the expandable reservoir is further constructed and arranged to receive a second fixed amount of ablative fluid and to deliver a second thermal dose of energy to a second portion of target tissue. an elongate shaft comprising a distal portion, wherein the elongate shaft is constructed and arranged to be introduced into the duodenum of the patient; an expandable reservoir positioned on the elongate shaft distal portion, wherein the expandable reservoir is constructed and arranged to receive a first fixed amount of ablative fluid and to deliver a first thermal dose of energy to a first portion of target tissue; and a fluid delivery assembly in fluid communication with the expandable reservoir, wherein the fluid delivery assembly is constructed and arranged to deliver the first fixed amount of ablative fluid to the expandable reservoir; an ablative fluid reservoir fluidly connected to a first input of a manifold having an output for fluid attachment to a pumping assembly such that liquid provided by the ablative fluid reservoir can be directed through the manifold to the expandable reservoir and an evacuation reservoir fluidly connected to a second input of the manifold, the manifold being configured to selectively connect the evacuation reservoir to the pumping assembly, such that the pumping assembly can propel fluid in a reverse direction into the evacuation reservoir to remove fluid from the expandable reservoir, wherein the first fluid reservoir is configured to provide at least the first fixed amount of ablative fluid to the fluid delivery assembly and the second fluid reservoir is configured to receive at least the first fixed amount of ablative fluid after the delivery of at least the first thermal dose of energy, and wherein the expandable reservoir is further constructed and arranged to receive a second fixed amount of ablative fluid and to deliver a second thermal dose of energy to a second portion of target tissue.