Many patients still die every year as a result of anastomotic leakage after surgery. The medical world needs an objective aid to detect leakage during surgery and during the critical recovery period. We propose a miniature measurement system to detect adequate tissue oxygenation pre- and postoperatively (continuously for 7 days) on the colon. The sensor chip should include an oxygen-saturation sensor, an oxygen-tension sensor, a carbon dioxide tension sensor and a temperature sensor. The work presented here focuses on the measurements done with the oxygen-tension and temperature sensors. In-vitro measurements were carried out to test the sensor system and initial in-vivo tests were performed on a rat kidney, during an ischemia-reperfusion experiment. ©2007 IEEE.