Background: Abdominal adhesions and abscesses are a major source of morbidity and mortality after abdominal surgery and peritonitis. Adhesions are hard to detect with standard imaging techniques. Liposomes, coated with polyethylene glycol (PEG), represent an agent developed for infection imaging. This study investigated the capacity of 99mTc-PEG-liposomes to localize early adhesion formation after peritonitis. Additionally, the value of 99mTc-PEG-liposomes for therapy evaluation of hyaluronan solution, which reduces adhesion and abscess formation in experimental peritonitis, was assessed. Methods: In 24 rats, a bacterial peritonitis was induced by performing a cecal ligation and puncture procedure. The animals were treated with sodium chloride solution or 0.4% hyaluronan solution intra-abdominally. One week later, scintigraphy was performed using 99mTc-PEG-liposomes, and abnormal focal uptake in the abdomen was scored. Thereafter, autopsy was performed and adhesions and abscesses were scored. Results: A significant correlation was found between the total adhesion score and the scintigraphic score (P < 0.01, r = 0.65). Treatment with hyaluronan significantly reduced the total adhesion score (P = 0.01). The size of abscesses significantly correlated with the scintigraphic score (P < 0.01, r = 0.65). Treatment with hyaluronan reduced the size of abscesses (P < 0.05). Conclusion: 99mTc-PEG-liposomes are able to detect early adhesions and abscesses and may be used for therapy evaluation of agents that reduce adhesions and abscesses.