Fluorescein endoscopy. A technique for noninvasive assessment of intestinal ischemia

Progress in the diagnosis and treatment of acute mesenteric ischemia

Acute mesenteric ischemia (AMI) is a life-threatening vascular emergency that requires early diagnosis and intervention to adequately restore mesenteric blood flow and prevent bowel necrosis and patient's death. The underlying cause of AMI is varied, and the prognosis depends on the precise pathologic findings. Despite the progress in understanding the pathogenesis of mesenteric ischemia and the development of modern treatment modalities, AMI remains a diagnostic challenge for clinicians, and the delay in diagnosis contributes to the continued high mortality rate. Early diagnosis and prompt effective treatment are essential to improve the clinical outcome.

Laparoscopic evaluation of intestinal ischemia using fluorescein and ultraviolet light in a porcine model

BACKGROUND

The laparoscopic use of fluorescein and ultraviolet light may be a useful diagnostic tool that potentially could reduce the time until diagnosis and the subsequent mortality of mesenteric ischemia.

METHODS

Eight pigs were subjected to a pneumoperitoneum pressure of 7 mmHg, and another eight pigs were exposed to a pressure of 14 mmHg. A segment of small bowel was devascularized. Two filters were used to create ultraviolet light. Pigs from each pressure group were given various intravenous fluorescein doses. The ischemic segment of the small intestine and other structures were inspected laparoscopically with the filters attached. A videotape was evaluated by resident and attending surgeons.

RESULTS

Ischemic bowel was seen as a darkened silhouette against the viable fluorescent tissue. Overall, the results show that the use of ultraviolet light and fluorescence in the laparoscopic model is adequate for allowing the identification of ischemic bowel.

CONCLUSIONS

The laparoscopic use of ultraviolet light combined with intravenous fluorescein dye is an effective diagnostic tool for evaluating mesenteric ischemia in pigs.

Use of a fluorescent bile acid to enhance visualization of the biliary tract and bile leaks during laparoscopic surgery in rabbits

BACKGROUND

We set out to determine whether intravenously administered cholylglycylaminofluorescein (CGF), a fluorescent bile acid, would enhance the visualization of the biliary tract and bile leaks in rabbits undergoing laparoscopic cholecystectomy (LC).

METHODS

CGF was infused at doses of 1, 5, and 10 mg/kg b.w. Biliary recovery was determined spectrophotometrically (six rabbits). For LC (seven rabbits), a blue (fluorescein) filter was attached to the light source, and a fluorescein-emission filter was attached to the charge coupled device (CCD) camera. The biliary tract and bile leak (made by incising the gallbladder) was observed under standard and fluorescent illumination.

RESULTS

Apple-green fluorescence appeared in 2 min and persisted for 30-60 min, enhancing visualization of bile duct anatomy as well as the bile leak. Biliary recovery of CGF at 90 min was high (86-96% of the infused dose).

CONCLUSION

In rabbits, CGF is secreted quantitatively in bile, induces biliary fluorescence, and enhances visualization of the bile ducts and bile leaks when viewed with appropriate filters.

Bowel ischaemia and organ impairment in elective abdominal aortic aneurysm repair

In 30 patients undergoing elective repair of abdominal aortic aneurysm the intramucosal pH (pHi) of the sigmoid colon was measured. Blood for endotoxin assay was taken at intervals before, during and after surgery. Daily measurements were made of liver transaminase activity and of arterial partial pressure of oxygen (PaO2). The mean (s.e.m.) peak systemic endotoxin concentration in those who developed intramucosal acidosis (pHi below 7.00) was 90(14) pg/ml, compared with 42(5) pg/ml in those who did not (P < 0.01). In the 14 patients whose pHi fell below 7.00, the mean (s.e.m.) postoperative rise in aspartate transaminase activity was 346(74) per cent, compared with 181(20) per cent in those whose pHi remained above this level (P < 0.05). The mean (s.e.m.) postoperative ratio of PaO2 to the fraction of inspired oxygen was 177(11) mmHg in those with intramucosal acidosis, compared with 260(24) mmHg in those whose pHi remained above 7.00 (P < 0.01). These results demonstrate a relationship between bowel ischaemia, endotoxaemia and organ impairment following elective aneurysm repair.

Laparoscopic procedures for small bowel disease

Small bowel procedures such as placement of feeding jejunostomy, diagnosis of small bowel ischaemia and obstruction, bowel resection and lysis of adhesions can all be performed laparoscopically. Diagnostic laparoscopy can be performed with low complication rates, and can help avoid unnecessary laparotomy. The open method of trocar placement is preferred in patients with adhesions or distended bowel due to obstruction or ileus. Feeding jejunostomy can be placed by laparoscopically assisted methods, pulling the jejunum out or completely laparoscopically. The latter requires fixation of the jejunum to the abdominal wall by transabdominal sutures or T-fasteners. The T-fastener technique for feeding jejunostomy is simple to perform, safe and effective. Small bowel ischaemia can be difficult to diagnose laparoscopically. Fluorescein and ultrasound Doppler examination of the small bowel may be as useful as in laparotomy, but there is little clinical experience with these techniques. Laparoscopically assisted small bowel resection involves intraperitoneal division of the mesenteric vessels and exteriorization of the small bowel through a small abdominal incision, followed by resection and anastomosis. The causes of small bowel obstruction can be diagnosed laparoscopically, and adhesions can be lysed under laparoscopic guidance. The laparoscopic approach is replacing laparotomy for many small bowel procedures. Improvements in instruments and experience in laparoscopic procedures will continue to make these procedures easier and safer to perform.

Ischemic colitis

Colon ischemia is a well-recognized clinical entity that often occurs spontaneously in patients over the age of 50 years. Many previous cases of nonspecific colitis are now felt to have been secondary to an ischemic event. In contrast to patients with acute mesenteric ischemia and extensive necrosis of the small bowel, the majority of patients with isolated colon ischemia follow a benign clinical course. Most patients present days, weeks, or months after the initial ischemic insult, and many may not have any recognizable antecedent episode of colon ischemia. However, some patients develop a fulminant form of the disease that causes colon infarction and death if not treated early. A high index of suspicion is necessary to make the diagnosis in the hospitalized patient. Endoscopy is recommended to confirm the diagnosis and the extent of injury and to monitor progression or resolution of disease. Aggressive management is of paramount importance to minimize the damage to the ischemic colon and reduce the otherwise high in-hospital mortality rate. Surgical intervention is indicated for patients with evidence of peritonitis or transmural infarction or perforation of the colon and for patients with chronic symptomatic colitis or stricture.

Endotoxaemia, the generation of the cytokines and their relationship to intramucosal acidosis of the sigmoid colon in elective abdominal aortic aneurysm repair

Ischaemia of the large bowel occasionally occurs following abdominal aortic aneurysm repair and may lead to multiple system organ failure (MSOF). Intramucosal acidosis of the sigmoid colon is a good indicator of sigmoid colonic ischaemia. Intramucosal pH of the sigmoid colon was measured using the silicone tonometer in 21 patients undergoing abdominal aortic aneurysmectomy. Samples were taken for plasma endotoxin, tumour necrosis factor (TNF) and interleukin-6 (IL-6) measurements preoperatively, half-hourly during the operation, 2-hourly for the next 12 h, 4-hourly for a further 48 h and 8-hourly thereafter until the fifth day. The intramucosal pH of the sigmoid colon fell to less than 7.00 peri-operatively in 10 patients, four of whom developed diarrhoea; in comparison, this did not occur in any of the 11 whose pH remained greater than 7.00 (p = 0.036). Higher peak concentrations of endotoxin, TNF and IL-6 were found in those patients whose intramucosal pH fell to less than 7.00 compared to those whose pH remained greater than 7.00 (mean +/- S.E.M. pg/ml, endotoxin = 112 +/- 24 vs. 58 +/- 6, p < 0.05; TNF = 26 +/- 8 vs. 7 +/- 2, p < 0.05; IL-6 = 213 +/- 59 vs. 87 +/- 12, p = 0.09). In the two patients who died, both from the group with pH level less than 7.00, concentrations of IL-6 were considerably higher than that in most of the other patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Celiac territory ischemic syndrome in visceral artery occlusion

Abdominal angina that is characterized by postprandial pain, and often associated with weight loss, is a well-recognized symptom complex of mesenteric artery insufficiency (mesenteric territory symptoms). In the past 5 years, we have observed six patients with atypical symptoms who had mesenteric artery occlusion combined with stenosis or occlusion of the celiac artery. Atypical symptoms included severe nausea and vomiting at the sight or smell of food, anorexia, weight loss, and right upper quadrant or epigastric discomfort (celiac territory symptoms). An extensive work-up to rule out gastric, pancreatic, biliary, or colonic pathology was undertaken in these patients. The findings included gallbladder dysfunction, diffuse micro-ulceration of gastric mucosa, and colonic mucosal ulceration. The diagnosis of visceral artery occlusion was initially missed in all six patients. Four patients had cholecystectomy. Visceral angiography confirmed occlusion of the celiac, superior, and inferior mesenteric arteries. Five patients had dramatic resolution of symptoms after restoration of visceral circulation. One patient who developed intestinal infarction before revascularization died. Symptoms suggesting upper abdominal visceral pathology may be a manifestation of celiac artery stenosis/occlusion coexisting with mesenteric artery occlusive disease. Visceral angiography should be part of the work-up in these patients for early diagnosis and prompt management.

Fluorescein-assisted laparoscopy in the identification of arterial mesenteric ischemia

Accurate identification of acute mesenteric ischemia remains a challenge. It was hypothesized that fluorescein-assisted laparoscopy (FAL) may have a role in the identification of acute arterial mesenteric ischemia. Arterial ischemic small-bowel segments were prepared in 11 dogs. Following 2.5 h of ischemia, laparoscopy was performed with a standard light source followed by FAL with an argon laser. These two techniques were immediately compared with open inspection. Standard laparoscopy correctly identified 10 ischemic segments. FAL correctly identified 9 ischemic segments and the combination of the 2 techniques allowed laparoscopy to correctly identify all 11 ischemic segments. Standard laparotomy with and without fluorescein correctly identified 10 ischemic segments. The difference between laparoscopy and laparotomy was not significant (P > 0.6, Fisher's exact test). The combination of laparoscopic evaluation with and without fluorescein allowed identification of small-bowel ischemia in all subjects in this canine model. Further studies are warranted to delineate the accuracy of laparoscopy in other patterns of mesenteric insufficiency before clinical application.

Diagnostic tests for intestinal ischemia

Mesenteric ischemia is a devastating disease. Without early diagnosis and intervention, the process proceeds to intestinal gangrene with its associated high morbidity and mortality rates. Although newer operative techniques and better intensive care unit management may improve patient outcome, it is only by obtaining an earlier diagnosis that greater patient survival rates will be possible. In an attempt to improve diagnostic accuracy, many modalities have been explored. These include serum biochemical markers, peritoneal fluid analysis, tonometry, radionuclide imaging, laparoscopy, and endoscopic techniques. At present, no single test has enabled the clinician to improve the patient's outcome. We are hopeful that the newer techniques, including radionuclide-labeled antibodies, tonometry, and reflectance spectrophotometry, may in the future be of assistance in improving the results for patients sustaining intestinal ischemia.