NERv's traditional feasibility clinical trial is a multi-center, pre-market, single-arm, and non-randomized trial. This study will involve the retrospective analysis of prospectively collected data. The trial is intended to establish the safety of NERv's Inline Device and collect preliminary data to illustrate the change in pH and electrical conductivity during normal postoperative recovery and in the event of a complication.

The purpose of NERv's feasibility study is to establish a clinical model that shows the progressive change in pH and electrical conductivity during a normal post-operative recovery and in the event of an anastomotic leak in colorectal, hepatobiliary (HPB), trauma, and general surgery patients. Upon analyzing data collected from NERv's Inline Device, a clinical model of change in pH and conductivity over time will be created. The clinical model can be used in future stages to determine if a complication is developing. For instance, boundaries (reading thresholds) can be established to detect a complication when readings exceed such boundaries.

Inclusion Criteria:

• Age ≥ 18 years - male or female
• Subject understands and has voluntarily signed and dated Informed Consent Form (ICF)
• Subjects must be willing to comply with trial requirements
• Subject has a peritoneal drain, such as Jackson Pratt drain attached post abdominal surgery

Exclusion Criteria:

• Plans that the subject will be discharged in less than 8 hours post-surgery
• Involvement in the planning and conduct of the clinical investigation
• Subject is participating in another investigational drug or device study which may interfere with the endpoints of this study
• NERv's Inline Device does not attach to drain used on the subject