The present study was set up to develop a new model of intraabdominal abscess (IAA) useful for hydrosaline metabolism studies based on the ligation of the appendix (AL) and wrapping of the appendix tip with omentum. Two experiments were designed: (1) to characterize the model and (2) to investigate extracellular volume (ECV) changes during parenteral nutrition (PN). Four groups of rabbits were studied at 3 (3DA) and 7 days (7DA) after AL or sham operation. PN was given for 6 days to two groups of septic rabbits: high volume HV) and low volume (LV) groups received 100 and 70 ml/kg.day of water with 7 and 0 meq/day of ClNa, respectively. Serum albumin (SA), ECV, and weight, water and sodium balances were determined. In 3DA, weight loss, reduced spontaneous intake, negative water balance, and reduction in SA were noted. Low SA, higher weight loss, and reduced intake were still observed in 7DA. SA correlated with ECV (r2 = 0.61, P = 0.003) in 7DA. Positive nitrogen balance was achieved during PN. The HV group had higher water and sodium balances than LV. In the HV group only, SA negatively correlated with sodium balance and with ECV at the end of PN (r2 = 0.87, P = 0.0007 and r2 = 0.9, P = 0.0001). The impact on hydrosaline metabolism of IAA in this model resembles that of moderate sepsis in humans. SA decrease appears to have two major components: escape around the inflammatory area and dilution. ECV expansion after PN is influenced by the initial SA concentration.