The authors thank Prof. Yu Guo and Prof. Yunpeng Hua (Department of Liver Surgery, the First Affiliated Hospital, Sun Yat-sen University) for providing advice and careful review. This work was supported by the National Natural Science Foundation of China (81201919), the Natural Science Foundation of Guangdong Province (2017A030313495).

Study protocol was approved by the ethics committee of the First Affiliated Hospital of Sun Yat-sen University and the study was conducted in accordance with the Helsinki Declaration. Written informed consents were obtained from patients.
1. Inclusion-exclusion criteria
<ol>
	<li>Include adult acute pancreatitis patients with evidence of infected necrosis that required an indication for invasive intervention. 
	NOTE: Acute pancreatitis is defined when at least two of the three following features are observed in patients 1) typical upper abdominal pain, 2) level of serum amylase or lipase above three times the upper level than normal, 3) typical findings of cross-sectional abdominal CT or MRI imaging10,11,12. Infected necrosis is defined as a positive culture obtained by fine needle aspiration or PCD of necrotic collections, or the presence of gas configurations within necrotic collections on contrast enhanced CT image.</li>
	<li>Exclude patients with previous invasive interventions for necrotizing pancreatitis, acute episode of chronic pancreatitis, recurrent acute pancreatitis and with indications for emergency laparotomy (i.e., abdominal compartment syndrome, perforation or bleeding of a visceral organ, and gastrointestinal or biliary obstruction).</li>
</ol>
2. VARD procedure
<ol>
	<li>Firstly, in acute necrotizing pancreatitis patients with above criteria, place ultrasound-guided percutaneous pigtail catheters (14 Fr or 16 Fr) into the left or right retroperitoneum to drain peripancreatic or necrotic collections, that can be located on the contrast enhanced CT image. (If condition permitted, duration of PCD placement should be maintained within about 4 weeks after the onset of AP for necrotic collections to demarcate and wall-off.</li>
	<li>If infected collections persisted and patients&#39; clinical situation deteriorates (progressive elevation of body temperature, elevated white blood cell count, C-reactive protein and procalcitonin, new onset of progressive organ dysfunction), be sure to provide surgical intervention and apply VARD in these patients1,2.</li>
	<li>Place the patient in supine position or in supine position with the left side 30-40&#176; elevated, and under general anesthesia.</li>
	<li>Make a skin incision (12 mm) at the site of previous pigtail catheter and gently dilate the tract with forceps.</li>
	<li>Insert a 12 mm laparoscopic trocar along the tract to the retroperitoneal necrotic collections followed by the removal of the pigtail catheter.</li>
	<li>Apply carbon dioxide pneumoretroperitoneum (11 mmHg to 12 mmHg) if a wider debridement space is needed by insufflating carbon dioxide through this 12 mm trocar.</li>
	<li>Place a near-infrared fluorescence laparoscopy via the observing trocar and make one additional incision (10 mm) subcostal in the left (or right) flank at the mid-axillary line, under laparoscopy monitoring (the incision can be close to the exit point of the percutaneous drain if another drainage pigtail catheter existed). The incision should be at least at a 8 cm distance from the observing trocar.</li>
	<li>Insert a 10 mm laparoscopic trocar from above the incision and remove necrotic debris using laparoscopic graspers. Necrotic debris turn out to be a retroperitoneal mass with grayish yellow under white light image or low contrasted under fluorescence image. Aspirate the collections by laparoscopic aspirator via the operative trocar. Extend the above incision to 5 cm with electrotome under laparoscopy monitoring if removal of the larger pieces of necrosis is needed.</li>
</ol>
3. ICG-guided intraoperative fluorescence imaging
<ol>
	<li>After insertion of a 10 mm operative trocar and before beginning to separate necrotic debris from adjacent normal tissue using laparoscopic forceps, switch the display mode of the laparoscopy to multi-display mode (white light image and fluorescence image are displayed separately in Picture-in-Picture mode).</li>
	<li>Inject the first bolus of ICG (0.1 mg/kg body weight) intravenously in a peripheral vein. Then, follow with a flush of 10 mL of saline. After 10 to 20 s, visualize peak perfusion of adjacent normal tissues or vessels in the fluorescence field. A clearer separating surface can be distinguished from the debris.</li>
	<li>Only remove poorly perfused and loosely adherent necrotic debris using laparoscopic graspers. Avoid tearing the underlying bowel or vessel.</li>
	<li>Inject another bolus of ICG (0.1 mg/kg body weight) intravenously if ICG fluorescence decay.</li>
	<li>After the removal of the bulk of necrotic debris, irrigate the cavity of the retroperitoneum with saline and aspirate with laparoscopic aspirator until the lavage fluid becomes clear.</li>
	<li>Place at least one pair of drainage tubes at the deepest region of the cavity after debridement. Suture the fascia and skin and close.</li>
</ol>
4. Postoperative management
<ol>
	<li>Perform continuous lavage with sterile saline and repeat CT scan 1 week after the VARD procedure.</li>
</ol>

<ol>
	<li>Trikudanathan, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Current+concepts+in+severe+acute+and+necrotizing+pancreatitis:+An+evidence-based+approach.">Current concepts in severe acute and necrotizing pancreatitis: An evidence-based approach.</a> Gastroenterology. 156 (7), 1994-2007 (2019).</li><li>Baron, T. H., DiMaio, C. J., Wang, A. Y., Morgan, K. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=American+Gastroenterological+Association+clinical+practice+update:+Management+of+pancreatic+necrosis.">American Gastroenterological Association clinical practice update: Management of pancreatic necrosis.</a> Gastroenterology. 158 (1), 67-75 (2020).</li><li>Raraty, M. G. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Minimal+access+retroperitoneal+pancreatic+necrosectomy:+improvement+in+morbidity+and+mortality+with+a+less+invasive+approach.">Minimal access retroperitoneal pancreatic necrosectomy: improvement in morbidity and mortality with a less invasive approach.</a> Annals of Surgery. 251 (5), 787-793 (2010).</li><li>Dhingra, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single+or+multiport+percutaneous+endoscopic+necrosectomy+performed+with+the+patient+under+conscious+sedation+is+a+safe+and+effective+treatment+for+infected+pancreatic+necrosis+(with+video).">Single or multiport percutaneous endoscopic necrosectomy performed with the patient under conscious sedation is a safe and effective treatment for infected pancreatic necrosis (with video).</a> Gastrointestinal Endoscopy. 81 (2), 351-359 (2015).</li><li>Gomatos, I. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Outcomes+from+minimal+access+retroperitoneal+and+open+pancreatic+necrosectomy+in+394+patients+with+necrotizing+pancreatitis.">Outcomes from minimal access retroperitoneal and open pancreatic necrosectomy in 394 patients with necrotizing pancreatitis.</a> Annals of Surgery. 263 (5), 992-1001 (2016).</li><li>Boni, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clinical+applications+of+indocyanine+green+(ICG)+enhanced+fluorescence+in+laparoscopic+surgery.">Clinical applications of indocyanine green (ICG) enhanced fluorescence in laparoscopic surgery.</a> Surgical Endoscopy. 29 (7), 2046-2055 (2015).</li><li>Nardi, P. 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The authors declare that they have no competing interests.

The present study reveals that ICG-guided real-time intraoperative near-infrared fluorescence imaging may provide benefit to perfusion assessment and visualization of adjacent normal tissues during debridement in VARD.
In the minimally invasive era, the step-up approach consisting of PCD or endoscopic transmural drainage followed by endoscopic necrosectomy or surgical debridement, such as VARD, has been regarded as standard treatment of severe acute necrotizing pancreatitis patients<sup class=...

Acute pancreatitis (AP) is one of the most common digestive diseases and brings enormous medical and economic burden to patients. About 20% of AP patients develop severe acute pancreatitis (SAP) that gets complicated with infected necrosis or persistent organ dysfunction1. SAP is usually associated with higher morbidity rate and mortality rate (up to 30%)1. In SAP patients with infected necrosis having persistent organ dysfunction or failure to recover after percutaneous drainage (PCD), or suffering from gastrointestinal or biliary obstruction, operative debridement should be considered1,2.
In the minimally invasive era, there are multiple approaches to operative debridement beside open surgery, including endoscopic transluminal necrosectomy, laparoscopic or open transgastric debridement, and video-assisted retroperitoneal debridement (VARD), which is the part of the step-up approach1,2. VARD is the preferred approach for patients with left-sided distribution of infected necrosis extended to paracolic gutter or deep to the retroperitoneum2. As there are rarely any visually clear separating surface in white light image under laparoscopy between necrotic debris and adjacent inflammatory normal tissues due to extensive retroperitoneal adhesions, VARD is inevitably accompanied by the risk of vascular injury, external pancreatico-cutaneous, or enterocutaneous fistulae3,4,5.
Real-time intraoperative near-infrared fluorescence imaging with indocyanine green (ICG) has been applied to facilitate perfusion assessment of bowel6,7 and visualization of biliary and vascular anatomy8,9. In view of the above disadvantages of VARD, we apply real-time near-infrared fluorescence imaging with ICG during VARD that enables the visualization of the well-perfused adjacent normal tissues and vascular structure. This modified technique (ICG-guided VARD) can provide a clear separating surface during operative debridement and reduced risk of vascular or enteric injury. ICG-guided VARD may facilitate surgeons to perform safer debridement in treating severe acute necrotizing pancreatitis.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>The 4K Ultra HD Fluorescence Endoscopic Navigation System</td>
			<td>Guangdong OptoMedic Technologies Inc</td>
			<td>OPTO-CAM214K</td>
			<td>fluorescence laparoscopy</td>
		</tr>
		<tr>
			<td>indocyanine green</td>
			<td>DanDong YiChuang Pharmaceutical CO., LTD</td>
			<td>H20055881</td>
			<td>indocyanine green injection for fluorescence imaging</td>
		</tr>
	</tbody>
</table>

indocyanine green-guided intraoperative imaging to facilitate video-assisted retroperitoneal debridement for treating acute necrotizing pancreatitis

Video-assisted retroperitoneal debridement (VARD) is a feasible, minimally invasive necrosectomy method for treating severe acute necrotizing pancreatitis, if it does not resolve or is accompanied with infected necrosis in the retroperitoneum. As there are rarely any visually clear separating surface in white light image between necrotic debris and adjacent inflammatory normal tissues due to extensive retroperitoneal adhesions, VARD is accompanied with the risk of vascular injury, external pancreatico-cutaneous or enterocutaneous fistulae. In view of the above disadvantages, we apply real-time intraoperative near-infrared fluorescence imaging with indocyanine green (ICG) during VARD, which enables visualization of the well-perfused adjacent normal tissues. This modified technique (ICG-guided VARD) can provide a clear separating surface during debridement and reduce the risk of vascular or enteric injury. ICG-guided VARD may facilitate surgeons to perform safer debridement in treating severe acute necrotizing pancreatitis.

ICG-guided VARD had been successfully performed in three severe acute necrotizing pancreatitis patients from June 2021. Characteristics of these patients at baseline and after VARD are included in Table 1. The first patient who received ICG-guided VARD was a male, 41-year-old patient who was admitted on 20th June 2021. He suffered from moderately acute necrotizing pancreatitis. Abdominal contrast enhanced CT scan revealed (as shown in Figure 1 and Table 1) t...

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Indocyanine Green-Guided Intraoperative Imaging to Facilitate Video-Assisted Retroperitoneal Debridement for Treating Acute Necrotizing Pancreatitis

This protocol presents Indocyanine Green-guided video-assisted retroperitoneal debridement (ICG-guided VARD) for treating severe acute necrotizing pancreatitis.

Video-assisted retroperitoneal debridement (VARD) is a feasible, minimally invasive necrosectomy method for treating severe acute necrotizing ...

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2.2K Views.  Sun Yat-sen University. This protocol presents Indocyanine Green-guided video-assisted retroperitoneal debridement (ICG-guided VARD) for treating severe acute necrotizing pancreatitis.

Video: Indocyanine Green-Guided Intraoperative Imaging to Facilitate Video-Assisted Retroperitoneal Debridement for Treating Acute Necrotizing Pancreatitis