Fluorescence imaging during bowel surgery cuts dangerous leak rates by 40%

UCD Research & Innovation

Colorectal cancer is the third most common cancer worldwide. Surgery remains the primary treatment for most cases, and the operation typically involves removing the cancerous section of bowel and then joining the two remaining ends back together — a connection called an anastomosis. When that join heals properly, patients recover. When it doesn't, the contents of the bowel leak into the abdominal cavity.

Anastomotic leak occurs in as many as one in four patients after colorectal surgery. It can trigger sepsis, require emergency reoperation, extend hospital stays by weeks, and kill. It is one of the most feared complications in abdominal surgery, and for two decades surgeons have been searching for reliable ways to reduce its incidence.

A tool already exists that can help. The question was whether the evidence was strong enough to prove it.

Seeing blood flow in real time with ICG

Indocyanine green fluorescence angiography (ICGFA) works by injecting a fluorescent dye — indocyanine green — into the patient's bloodstream during surgery. When illuminated with near-infrared light, the dye glows, allowing the surgeon to see in real time whether the tissue at the planned anastomosis site has adequate blood supply. Tissue that doesn't glow brightly enough is poorly perfused and unlikely to heal well. The surgeon can then choose a different, better-supplied section of bowel for the join.

The concept is straightforward: check blood flow before you commit to a connection point, and change course if the supply is inadequate. Individual studies have been promising. But no single randomized controlled trial had produced the statistical power to definitively prove the technique reduces leaks. The trials were too small, the event rates too variable, the confidence intervals too wide.

Nine trials, 4,754 patients, one clear result

A team led by Prof Ronan Cahill, Director of the Centre for Precision Surgery at University College Dublin, pooled the data. Published in The Lancet Gastroenterology & Hepatology, their PRISMA-compliant meta-analysis combined nine randomized controlled trials enrolling a total of 4,754 patients undergoing colorectal surgery.

The result: ICGFA reduced the risk of anastomotic leak by 40%. The benefit was particularly pronounced in left-sided and rectal surgery — the anatomical regions where blood supply is most precarious and leak rates are highest.

This is the kind of evidence that changes clinical guidelines. Individual trials suggested benefit; the combined analysis confirms it with the statistical robustness that guideline committees and hospital administrators require before mandating a new standard of care.

What the surgeon sees — and what changes

ICGFA doesn't just prevent leaks passively. It actively changes surgical decisions. When the fluorescence imaging reveals poor perfusion at the intended anastomosis site, the surgeon resects additional tissue to reach a well-vascularized segment. Without the imaging, those decisions are made based on visual inspection and clinical judgment alone — assessment methods that, while experienced surgeons use them skillfully, can miss perfusion deficits invisible to the naked eye.

The tool also provides documentation. The fluorescence images create a record of the tissue's perfusion status at the time of the operation, offering an objective basis for the surgical decisions made. In an era of increasing emphasis on surgical quality assurance and medico-legal accountability, this documentation function may prove nearly as valuable as the clinical one.

Why it took this long to prove

The gap between ICGFA's clinical availability and definitive proof of its effectiveness reflects a broader challenge in surgical research. Randomized controlled trials in surgery are harder to run than drug trials. You can't blind the surgeon to whether they're using fluorescence imaging. Patient recruitment is slower. Anastomotic leak rates, while devastating, are variable enough that individual trials need large sample sizes to detect meaningful differences.

Each of the nine included trials, taken alone, fell short of conclusive proof. Some showed strong trends; others had wide confidence intervals that crossed the line of no effect. Only by combining them — with the methodological rigor of a pre-registered, PRISMA-compliant systematic review — did the signal emerge clearly from the noise.

Prof David Jayne of the University of Leeds, a co-author, described the meta-analysis as providing the evidence needed to change practice and reduce the burden of a life-threatening complication. Dr Denise Hilling of Leiden University Medical Center argued that rather than conducting more clinical trials of ICGFA itself, the focus should shift to wider adoption.

Limitations of the pooled evidence

Meta-analyses inherit the limitations of their component studies. The nine trials varied in surgical technique, patient population, ICGFA protocols, and definitions of anastomotic leak. Some included only rectal surgery; others covered the full spectrum of colorectal operations. Heterogeneity between studies, while managed statistically, means the 40% risk reduction is an average across diverse clinical settings rather than a guarantee for any individual patient or surgical approach.

The technology also requires equipment — a near-infrared camera system and the ICG dye itself — that adds cost to the procedure. In well-funded surgical centers, this is a minor consideration. In resource-constrained settings, where colorectal cancer rates are rising fastest, the economic case needs separate evaluation. The meta-analysis demonstrates clinical effectiveness, not cost-effectiveness.

There's also the question of surgeon experience. ICGFA requires interpretation of the fluorescence images, and the learning curve — how many cases a surgeon needs before reliably distinguishing adequate from inadequate perfusion — is not well characterized across the included trials. A tool is only as good as the clinician using it.

From proof to standard practice

Cahill frames the meta-analysis as settling a two-decade question: of all the innovations in colorectal surgery over the past 20 years, ICGFA is now proven as the most useful additional step surgeons can take to ensure safe outcomes during cancer and other resectional operations.

The practical implications are clear. Hospitals performing colorectal surgery should have ICGFA capability available. Surgeons should be trained in its use. Clinical guidelines should be updated to reflect the evidence. Co-author Prof Jan Watanabe of Kansai Medical University described this as a shift from proving efficacy to implementing the technology in routine practice.

The technique also opens a door. If fluorescence imaging can reduce leak rates by 40%, what happens when you layer artificial intelligence on top of the fluorescence data? Automated perfusion assessment, real-time risk scoring, decision support algorithms trained on thousands of ICGFA images — these are the next steps Cahill's group is pursuing. But they stand on a foundation that, as of this meta-analysis, is now solid.