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Published on: May 11, 2011
Intra-Abdominal Photodynamic Therapy in a Rabbit Model of Perforated Appendicitis
Importance:
Perforated appendicitis is a common and morbid pediatric surgical condition frequently requiring prolonged antibiotic therapy. Adjunctive intraoperative strategies for local antimicrobial therapy are limited, and photodynamic therapy (PDT) may offer a targeted, resistance-independent approach.
Objective:
To evaluate the feasibility, safety, and preliminary efficacy of laparoscopic methylene blue photodynamic therapy (MB-PDT) for intra-abdominal disinfection in a rabbit model of perforated appendicitis.
Design:
Experimental preclinical animal study conducted between 2023 and 2025.
Setting:
Single-center laboratory-based animal research facility affiliated with an academic medical center.
Participants:
Nineteen New Zealand White rabbits underwent surgically induced perforated appendicitis with peritonitis via appendiceal ligation and electrocautery perforation.
Interventions:
Rabbits received laparoscopic MB-PDT (n=9) or control conditions (methylene blue only, no light; n=10) 24 - 40 hours after appendiceal perforation. MB-PDT involved peritoneal lavage with 300 µg/mL methylene blue, followed by 665 nm laser illumination to 25 J/cm 2 . Peritoneal aspirates were collected before and 24h after intervention. Bacterial burden was quantified, and isolated bacteria were submitted to in vitro PDT. Tissue samples from intraperitoneal organs were collected 24 hours post-intervention.
Main Outcomes And Measures:
Primary outcomes included feasibility of PDT delivery, safety (histologic evidence of off-target injury), and preliminary in vivo efficacy (change in bacterial burden pre-vs. post-intervention). Secondary outcomes included clinical parameter changes and in vitro MB-PDT efficacy.
Results:
Of the 14 rabbits that developed peritonitis, 10 (age 5-6 months, weight 3.1-3.8 kg) completed follow-up. Laparoscopic MB-PDT delivery was feasible and caused no off-target histologic injury. Bacterial burden increased in MB-PDT animals relative to controls, though not significantly (p=0.18). Post-intervention, body temperature showed a trend toward reduction in MB-PDT animals (-0.37 ± 1.32°C) vs controls (0.26 ± 0.76°C; p=0.27). In vitro MB-PDT significantly reduced bacterial burden for all tested species (p<0.001), with greater efficacy in Gram-positive bacteria.
Conclusions And Relevance:
Laparoscopic MB-PDT was feasible and safe in a rabbit model of perforated appendicitis, with high in vitro antimicrobial efficacy. Although in vivo bacterial reduction was not demonstrated, these results support further investigation of MB-PDT as a novel intraoperative adjunct for treating intra-abdominal infection.
Insights
Methylene blue photodynamic therapy (MB-PDT) is safe and feasible for treating perforated appendicitis in rabbits. While not reducing bacterial burden in vivo, it showed strong in vitro efficacy, suggesting potential for intra-abdominal infections.
Area of Science:
- Surgical Innovation
- Antimicrobial Therapy
- Preclinical Research
Background:
- Perforated appendicitis in children often requires prolonged antibiotics.
- Current intraoperative antimicrobial options are limited.
- Photodynamic therapy (PDT) offers a targeted, resistance-independent approach.
Purpose of the Study:
- To assess the feasibility, safety, and preliminary efficacy of laparoscopic methylene blue photodynamic therapy (MB-PDT).
- To evaluate MB-PDT for intra-abdominal disinfection in a rabbit model of perforated appendicitis.
Main Methods:
- Nineteen rabbits underwent induced perforated appendicitis and peritonitis.
- Laparoscopic MB-PDT was administered 24-40 hours post-perforation.
- Outcomes included PDT delivery feasibility, safety (histology), and bacterial burden changes (in vivo and in vitro).
Main Results:
- Laparoscopic MB-PDT was feasible and safe, with no off-target histologic injury.
- In vivo bacterial burden did not significantly decrease (p=0.18).
- In vitro MB-PDT demonstrated significant bacterial reduction (p<0.001), especially for Gram-positive bacteria.
Conclusions:
- Laparoscopic MB-PDT is a safe and feasible adjunct for perforated appendicitis in a preclinical model.
- High in vitro efficacy supports further investigation for intra-abdominal infections.
- Further research is warranted to optimize in vivo efficacy.
