Laser speckle contrast imaging and quantitative fluorescence angiography for perfusion assessment.

PURPOSE: Indocyanine green fluorescence angiography (ICG-FA) is an established technique for assessment of intestinal perfusion during gastrointestinal surgery, whereas quantitative ICG-FA (q-ICG) and laser speckle contrast imaging (LSCI) are relatively unproven. The study aimed to investigate whether the techniques could be applied interchangeably for perfusion assessment. METHODS: Nineteen pigs underwent laparotomy, two minor resections of the small bowel, and anastomoses. Additionally, seven pigs had parts of their stomach and small intestine de-vascularized. Data was also collected from an in vivo model (inferior caval vein measurements in two additional pigs) and an ex vivo flow model, allowing for standardization of experimental flow, distance, and angulation. Q-ICG and LSCI were performed, so that regions of interest were matched between the two modalities in the analyses, ensuring coverage of the same tissue. RESULTS: The overall correlation of q-ICG and LSCI evaluated in the porcine model was modest (rho = 0.45, p < 0.001), but high in tissue with low perfusion (rho = 0.74, p < 0.001). Flux values obtained by LSCI from the ex vivo flow model revealed a decreasing flux with linearly increasing distance as well as angulation to the model. The Q-ICG perfusion values obtained varied slightly with increasing distance as well as angulation to the model. CONCLUSIONS: Q-ICG and LSCI cannot be used interchangeably but may supplement each other. LSCI is profoundly affected by angulation and distance. In comparison, q-ICG is minimally affected by changing experimental conditions and is more readily applicable in minimally invasive surgery.

Optimized protocol of multiple post-processing techniques improves diagnostic accuracy of multidetector computed tomography in assessment of small bowel obstruction compared with conventional axial and coronal reformations.

BACKGROUND: Axial and coronal reformations have been a widely used image post-processing protocol for the ordinary multidetector computed tomography (MDCT) examination of patients with small bowel obstruction (SBO) or other abdominal diseases. The diagnostic accuracy of MDCT for assessing SBO is expected to be further improved through the use of multiple post-processing techniques. AIM: To systemically evaluate the diagnostic accuracy and efficiency of an optimized protocol using multiple post-processing techniques for MDCT assessment of SBO and secondary bowel ischemia. METHODS: This retrospective cross-sectional study included 106 patients with clinically suspected SBO. Two readers applied three protocols to image post-processing and interpretation of patients' MDCT volume data. We compared the three protocols based on time spent, number of images, diagnostic self-confidence, agreement, detection rate, and accuracy of detection of SBO and secondary bowel ischemia. RESULTS: Protocol 2 resulted in more time spent and number of images than protocols 1 and 3 (P < 0.01), but the results of the two readers using the same protocol were not different (P > 0.05). Using protocol 3, both readers added multiple post-processing techniques at frequencies of 29.2% and 34.9%, respectively, for obstruction cause, and 32.1% and 30.2%, respectively, for secondary bowel ischemia. Protocols 2 and 3 had higher total detection rates of obstruction cause and secondary bowel ischemia than protocol 1 (P < 0.01), but no difference was detected between protocols 2 and 3 (P > 0.05). The accuracy, sensitivity, specificity, positive predictive value and negative predictive value of protocols 2 and 3 were superior to those of protocol 1 for evaluating obstruction cause and secondary bowel ischemia. CONCLUSION: Our optimized protocol of multiple post-processing techniques can both guarantee efficiency and improve diagnostic accuracy of MDCT for assessing SBO and secondary bowel ischemia.

Assessment of Bowel Wall Enhancement for the Diagnosis of Intestinal Ischemia in Patients with Small Bowel Obstruction: Value of Adding Unenhanced CT to Contrast-enhanced CT.

Purpose To determine whether adding unenhanced computed tomography (CT) to contrast material-enhanced CT improves the diagnostic performance of decreased bowel wall enhancement as a sign of ischemia complicating mechanical small bowel obstruction (SBO). Materials and Methods This retrospective study was approved by the institutional review board, which waived the requirement for informed consent. Two gastrointestinal radiologists independently performed retrospective assessments of 164 unenhanced and contrast-enhanced CT studies from 158 consecutive patients (mean age, 71.2 years) with mechanical SBO. The reference standard was the intraoperative and/or histologic diagnosis (in 80 cases) or results from clinical follow-up in patients who did not undergo surgery (84 cases). Decreased bowel wall enhancement was evaluated with contrast-enhanced images then and both unenhanced and contrast-enhanced images 1 month later. Diagnostic performance of decreased bowel wall enhancement and confidence in the diagnosis were compared between the two readings by using McNemar and Wilcoxon signed rank tests. Interobserver agreement was assessed by using κ statistics and compared with bootstrapping. Results Ischemia was diagnosed in 41 of 164 (25%) episodes of SBO. For both observers, adding unenhanced images improved decreased bowel wall enhancement sensitivity (observer 1: 46.3% [19 of 41] vs 65.8% [27 of 41], P = .02; observer 2: 56.1% [23 of 41] vs 63.4% [26 of 41], P = .45), Youden index (from 0.41 to 0.58 for observer 1 and from 0.42 to 0.61 for observer 2), and confidence score (P < .001 for both). Specificity significantly increased for observer 2 (84.5% [104 of 123] vs 94.3% [116 of 123], P = .002), and interobserver agreement significantly increased, from moderate (κ = 0.48) to excellent (κ = 0.89; P < .0001). Conclusion Adding unenhanced CT to contrast-enhanced CT improved the sensitivity, diagnostic confidence, and interobserver agreement of the diagnosis of ischemia, a complication of mechanical SBO, on the basis of decreased bowel wall enhancement. (©) RSNA, 2016.

Enhanced-reality video fluorescence: a real-time assessment of intestinal viability.

OBJECTIVE: Our aim was to evaluate a fluorescence-based enhanced-reality system to assess intestinal viability in a laparoscopic mesenteric ischemia model. MATERIALS AND METHODS: A small bowel loop was exposed, and 3 to 4 mesenteric vessels were clipped in 6 pigs. Indocyanine green (ICG) was administered intravenously 15 minutes later. The bowel was illuminated with an incoherent light source laparoscope (D-light-P, KarlStorz). The ICG fluorescence signal was analyzed with Ad Hoc imaging software (VR-RENDER), which provides a digital perfusion cartography that was superimposed to the intraoperative laparoscopic image [augmented reality (AR) synthesis]. Five regions of interest (ROIs) were marked under AR guidance (1, 2a-2b, 3a-3b corresponding to the ischemic, marginal, and vascularized zones, respectively). One hour later, capillary blood samples were obtained by puncturing the bowel serosa at the identified ROIs and lactates were measured using the EDGE analyzer. A surgical biopsy of each intestinal ROI was sent for mitochondrial respiratory rate assessment and for metabolites quantification. RESULTS: Mean capillary lactate levels were 3.98 (SD = 1.91) versus 1.05 (SD = 0.46) versus 0.74 (SD = 0.34) mmol/L at ROI 1 versus 2a-2b (P = 0.0001) versus 3a-3b (P = 0.0001), respectively. Mean maximal mitochondrial respiratory rate was 104.4 (±21.58) pmolO2/second/mg at the ROI 1 versus 191.1 ± 14.48 (2b, P = 0.03) versus 180.4 ± 16.71 (3a, P = 0.02) versus 199.2 ± 25.21 (3b, P = 0.02). Alanine, choline, ethanolamine, glucose, lactate, myoinositol, phosphocholine, sylloinositol, and valine showed statistically significant different concentrations between ischemic and nonischemic segments. CONCLUSIONS: Fluorescence-based AR may effectively detect the boundary between the ischemic and the vascularized zones in this experimental model.

Assessment of abnormal bowel perfusion using contrast-enhanced ultrasonography after small bowel transplantation: a case report.

A 59-year-old man with short-bowel syndrome received a small bowel transplantation. Because the recipient complained of severe abdominal pain 40 hours after the surgery and was highly suspected of having mesenteric vascular thrombosis, contrast-enhanced sonography (CEUS) was performed at his bedside. CEUS demonstrated that the superior mesenteric artery was patent, but the bowel graft showed hypoenhancement, indicating severely inadequate perfusion of the graft. Due to this complication, the patient underwent an exploratory laporatomy, and the bowel graft was removed. The pathologic findings support the diagnosis of acute vascular rejection after intestinal transplantation. This case suggests that CEUS can be used to assess perfusion and vascular complications after intestinal transplantation, as it is noninvasive and easily performed at bedside.

Assessment of inflammatory and fibrotic stenoses in patients with Crohn's disease using contrast-enhanced ultrasound and computerized algorithm: a pilot study.

PURPOSE: The development of stenosis is a typical complication of Crohn's disease and represents a serious diagnostic and therapeutic challenge. The aim of the present study was to define objective quantitative measures of stricture characteristics (fibrostenotic/cicartricial vs. inflammatory) using contrast-enhanced ultrasound (CEUS) in patients with stenotic Crohn's disease. MATERIALS AND METHODS: During a period of 18 months, 18 consecutive patients with Crohn's disease and manifestation of a localized significant small bowel stenosis were prospectively recruited. Standardized ultrasound (US) examination, color-coded duplex sonography and CEUS using SonoVue® were performed. Quantitative measurements of bowel wall vascularity were determined using computerized algorithms (Bracco QONTRAST software). The quality of stenosis (fibrostenotic vs. inflammatory) was classified in a 4-point scale, and the diagnostic/prognostic power of the US and clinical tests upon initial presentation were compared. RESULTS: We established a novel standardized CEUS procedure using computerized algorithms to quantitatively examine stenoses in Crohn's disease. An inflammatory origin of stenosis correlated significantly with a high Crohn's Disease Activity Index (CDAI) (p < 0.01), the length of stenosis (p < 0.01) as well as the Limberg score (p < 0.01). There was no correlation between the type of stenosis and quantitative results of CEUS. CONCLUSION: Although bowel wall vascularity can be quantitatively assessed in stenotic areas by CEUS, this analysis does not improve the diagnostic power for the objective determination of the quality of stenosis at a single measurement. Semiquantitative analysis of bowel wall vascularity, length of stenosis, and CDAI may help to discriminate the origin of small bowel stenosis in Crohn's disease.

Interobserver agreement on the diagnosis of bowel ischemia: assessment using dynamic computed tomography of small bowel obstruction.

PURPOSE: The aim of this study was to evaluate the accuracy and interobserver variability of dynamic computed tomography (CT) for diagnosis of small bowel obstruction. METHOD AND MATERIALS: A total of 115 patients with a CT diagnosis of small bowel obstruction were included. Two radiologists and two residents performed blinded, independent, retrospective reviews of CT studies. Attention was focused on the presence of reduced early enhancement of the bowel wall and closed loop obstruction. Results were correlated with surgical findings in 15 cases and clinical follow-up in 100 cases. Sensitivity and specificity were calculated, and kappa statistics were used to analyze interobserver agreement. RESULTS: In all, 13 cases were surgically confirmed small bowel ischemia. Sensitivity, specificity, positive predictive value, and negative predictive value for the diagnosis of ischemia were 85%, 96%-97%, 73%-79%, and 97%-98%, respectively, for radiologists and 69%-93%, 93%-95%, 63%-64%, and 96%-99%, respectively, for residents. For agreement in the interpretations of reduced early enhancement of bowel wall, closed loop obstruction, and presence of bowel ischemia, the values were 0.62, 0.71, and 0.80, respectively, between radiologists and 0.57-0.70, 0.63-0.74, and 0.56-0.68, respectively, between radiologists and residents. CONCLUSION: There was moderate or substantial agreement for the diagnosis of small bowel ischemia between radiologists and residents. However, there was substantial agreement for the presence of closed loop obstruction.

Portal versus systemic drainage of small bowel allografts: comparative assessment of survival, function, rejection, and bacterial translocation.

BACKGROUND: Portal venous drainage of small bowel grafts is theoretically more physiologic than systemic drainage, but is technically more demanding. Comparisons in animal models have not demonstrated a clear advantage of one technique over the other, but clinical data are lacking. STUDY DESIGN: Clinical records of 36 patients who underwent 37 small bowel transplantation procedures from January 1995 to August 2001 were reviewed. Portal drainage was performed in 19 patients (PD group). Systemic drainage was performed in 18 patients (SD group). Median followup was 531 days. RESULTS: PD and SD patients had similar ICU stays (median 7 versus 9 days) and endotracheal intubation durations (median 3 versus 5 days). All current survivors, with the exception of one patient in each group, are independent from parenteral nutrition. Liver function tests were similar in both groups. There was a twofold increase in tacrolimus dosage in the PD group to achieve similar trough levels indicating a "first-pass" hepatic clearance effect. Cumulative incidence of acute rejection episodes and OKT3-requiring rejection episodes were similar in both groups. To the contrary, a lower incidence of gram-negative rods of Enterococcus sp. in blood or bronchoalveolar lavage suggested that the clearance of translocated intestinal bacteria was more efficient in the PD group. Graft and patient survival rates were similar in both groups. CONCLUSIONS: Systemic venous drainage of small bowel transplants is a dependable technique, associated with similar results as portal venous drainage, in terms of overall mortality, morbidity, rejection, function, and patient and graft survival. But attention should be paid to an impaired clearance of intestinal bacterial translocation after systemic drainage.

An assessment of the effect of Ginkgo Biloba EGb 761 on ischemia reperfusion injury of intestine.

BACKGROUND/AIMS: The aim of this study was to determine the effect of Ginkgo Biloba (EGb 761) on reperfusion injury of the small bowel. METHODOLOGY: Forty-eight male 200-250 g Spraque-Dawley rats in six groups were used to determine the biochemical and histopathological changes after a 30-min ischemia and 30-min reperfusion. Pre-treatment with 50 mg/kg EGb 761 (Tebofortan, Karlsruhe-Germany) or 10-mL/kg saline was administered intravenously in the treatment and control groups. The superior mesenteric artery was occluded distal to the right colic artery and collateral arcades were ligated to provide complete ischemia. Ischemia was determined by the existence of pulseless or pale color of the small intestine. The return of the pulses and the reestablishment of the pink color were assumed to be the reperfusion of the intestine. Rats that were administered Egb 761 and saline were subjected to laparotomy, ischemia, or ischemia-reperfusion procedures. Mucosal lesions were graded from 0 to 5 in histopathological examination. Malondialdehyde and myeloperoxidase levels of the intestinal mucosa were measured. RESULTS: No significant difference was noted between the control and treatment groups regarding the histopathological changes. Although malonyldialdehyde and myeloperoxidase levels of the reperfusion + EGb 761 group were slightly higher than the laparotomy + saline group, they were significantly lower than the reperfusion + saline group. CONCLUSIONS: We concluded that EGb 761 pre-treatment before ischemia-reperfusion decreased malondialdehyde and myeloperoxidase levels and attenuated the mucosal damage.

Assessment of intestinal viability using a non-contact laser tissue blood flowmeter.

BACKGROUND: Intraoperative assessment of small intestinal viability following ischemic insult from arterial occlusion has remained difficult. The purpose of the present study was to assess the applicability of non-contact tissue blood flowmeter (NCLBF) with regard to intraoperative assessment of intestinal viability. METHODS: Using the ischemia-reperfusion model of rabbits, the relationship between the records of NCLBF, pulse oximetry (PO), and histological grade and the comparison of accuracy of intestinal viability among NCLBF, PO, and fluorescein (FL) were examined. RESULTS: There was a significant relationship between NCLBF and the histological grade (coefficient-0.80, P <0.0001); however, PO was not related. The accuracy and sensitivity of bowel viability of NCLBF (76%, 88%) were better than those of PO (58%, 23%) and FL (48%, 4%), respectively (P <0.001). CONCLUSIONS: NCLBF is useful to assess intestinal viability, suggesting the possibility of clinical use.

Assessment of resveratrol bioavailability in the perfused small intestine of the rat.

Resveratrol, which is present in grapes, wine and peanuts, is believed to possess chemoprotective properties such as anticarcinogenic effects and to provide protection against cardiovascular diseases. Little is known, however, about its intestinal absorption. We investigated the absorption and metabolism of resveratrol by using an isolated preparation of luminally and vascularly perfused rat small intestine. A synthetic perfusate free from blood components was used as vascular medium with a perfluorocarbon as oxygen carrier. Luminal media consisted of a bicarbonate buffered sodium chloride solution spiked with resveratrol in physiological, nutritionally relevant concentrations (28, 34 and 57 micromol/l, respectively). Viability was maintained during the entire perfusion and no significant differences between resveratrol and control perfusions for oxygen consumption, arterial pressure, lactate-pyruvate ratio and acid-base homeostasis were observed. Vascular uptake of luminally administered resveratrol was 20.5%. The majority of the absorbed resveratrol was conjugated to yield resveratrol glucuronide (16.8%), which was also the main luminal metabolite (11.2%). Lesser amounts of resveratrol sulfate, 3.0% and 0.3%, were found on the luminal and vascular side, respectively, while only minute amounts of resveratrol and resveratrol conjugates (1.9%) were found in the intestinal tissue. The structures of the resveratrol conjugates were verified by liquid chromatography coupled with mass spectometry (LC-MS). The results demonstrate an ample uptake and metabolic conversion of resveratrol. The proposed perfusion model serves as a tool to evaluate intestinal absorption and metabolic handling of phytochemicals, a pertinent input to the ongoing discussion about their health benefits.

Assessment of the effects of endothelin-1 and magnesium sulphate on regional blood flows in conscious rats, by the coloured microsphere reference technique.

There is evidence to suggest that magnesium (Mg2+) is beneficial in the treatment of a number of conditions, including pre-eclampsia and acute myocardial infarction. The mode of action of Mg2+ in these conditions is not clear, although the vasodilator properties of Mg2+ are well documented both in vitro and in vivo. Previously, we demonstrated that i.v. infusion of magnesium sulphate (MgSO4) alone, or in the presence of vasoconstrictors, caused increases in flow and conductance in the common carotid, internal carotid and hindquarters vascular beds, in conscious rats. Therefore, the objective of the present study was to investigate the regional and subregional changes in haemodynamics in response to the vasoconstrictor peptide endothelin-1 (ET-1) and MgSO4 in more detail, using the coloured microsphere reference technique. Infusion of ET-1 and MgSO4 had similar effects on heart rate and mean arterial pressure as in our previous study. Infusion of ET-1 caused a rise in mean arterial pressure and a fall in heart rate, and infusion of MgSO4 returned mean arterial pressure to control levels with no effect on heart rate. The responses to MgSO4 in the presence of ET-1 showed considerable regional heterogeneity with blood flow increasing (e.g. skeletal muscle), decreasing (e.g. stomach) or not changing (e.g. kidney). Of particular interest was the finding that MgSO4 caused increases in flow in the cerebral and coronary vascular beds. This, and our previous studies, have shown that MgSO4 can reverse vasoconstriction in a number of vascular beds, and indicate that this compound may have therapeutic benefit in conditions associated with vasospasm.

In vivo assessment of the influence of cold preservation time on microvascular reperfusion injury after experimental small bowel transplantation.

BACKGROUND: This study describes the impact of prolonged cold storage on microvascular reperfusion injury of transplanted rat small bowel isografts. METHODS: In vivo fluorescence microscopy was used to assess intestinal microcirculation after 6, 12, 18 and 24 h of cold (4 degrees C) ischaemia in University of Wisconsin solution and 20-90 min of reperfusion. Sham-operated animals served as controls. RESULTS: Whereas 6 and 12 h of ischaemia did not affect functional capillary density of the intestinal graft mucosa, villous perfusion was significantly impaired after 18 and 24 h of cold preservation. Similarly, microvascular perfusion of circular and longitudinal muscle was not affected after 6 h, but deteriorated following prolonged cold ischaemia. Leucocyte-endothelial cell interaction in submucosal venules was significantly enhanced after 6 h of ischaemia with peak values after 12 and 18 h. A progressive reduction of lymphatic capillary drainage indicated an ischaemia time-related deterioration in graft function. CONCLUSION: The results provide evidence that leucocyte-endothelial cell interaction in submucosal venules of the transplanted intestine is a primary step in the manifestation of reperfusion injury following short periods of cold ischaemia.

Assessment of blood flow in the small intestine by laser Doppler flowmetry: comparison of healthy small intestine and small intestine in Crohn's disease.

Blood flow and blood distribution were investigated in 40 patients with normal small intestine and the relation between blood flow and the morphological features of Crohn's disease was examined in 11 patients with Crohn's disease by laser Doppler flowmetry from the serosal side during surgery. In normal small intestine, blood flow was measured at six points: upper, middle, and lower small intestine, each of the mesenteric borders, and the antimesenteric surface. In Crohn's disease, macroscopically normal tissue and affected lesions were observed in detail by intraoperative endoscopy after blood flow measurement. The blood flow values in the normal small intestine gradually decreased from the upper to the lower small intestine. As the level of inflammation progressed in Crohn's disease the blood flow values gradually decreased; the exudative stage of Crohn's disease (aphthoid ulcer) showed blood flow values that were slightly below those in macroscopically normal tissue. These results are the first to demonstrate decreased blood flow in affected lesions in Crohn's disease and changes in blood flow according to the degree of inflammation in vivo.

Assessment of anastomotic reliability with pulse oximetry in graded intestinal ischemia: an experimental study in dogs.

BACKGROUND/PURPOSE: Pulse oximetry has been proposed as an appropriate and feasible technique in the assessment of intestinal ischemia in recent years. In this study the authors aimed to assess the reliability of anastomoses in the dog small intestine in which there is graded irreversible ischemia as measured by pulse oxymeter. METHODS: In a control group of four dogs, without any devascularization, three small bowel anastomoses were formed in each dog. The study group consisted of 12 dogs. In each animal three intestinal segments with different levels of ischemia were created by ligating the marginal vessels proximally and distally in sequence beginning from the midpoint of the segmental vascular arcade. Preanastomotic pulse oximeter readings between 80% and 90% were assigned to mild ischemia, 70% and 80% to moderate, and 60% and 70% to severe ischemia group. Pulse oximetry measurements were obtained from probes applied to the antimesenteric serosal surfaces at the midpoint of small intestinal segments. A total of 48 intestinal segments (12 nonischemic in the control group and 36 with three different levels of ischemia in the study group) were transected in the midpoint and anastomosed in double layers. Postanastomotic SaO2 values were also noted. The anastomoses were evaluated 48 hours later macroscopically if there was any leakage, and biopsy specimens were obtained for histopathologic ischemic gradings. All results were studied statistically. RESULTS: Histopathologic grades between each group were statistically different (P < .01 for each comparison) except for control and mild ischemia groups (P > .05), worsening as the level of ischemia increased. Pre- and postanastomotic pulse oximetry measurements correlated very well with the histological gradings (r = -0.90, P < .001 and r = -0.93, P < 0.001 respectively). Number of anastomotic leakages were none in control, one in mild, nine in moderate, and 12 (all of the anastomoses) in severe ischemia groups. In the moderate ischemia group with an average preanastomotic pulse reading of 76.75%, each of the leaking anastomoses had a postanastomotic pulse measurement of lower than 70%. The finding that the difference between histopathologic grades of control and mild ischemia groups with average preanastomotic pulse measurements of 96% and 85%, respectively is not statistically significant enables us to suggest that a saturation of at least 85% is necessary for a reliable anastomosis. CONCLUSION: These results suggest clearly that anastomotic reliability can be predicted objectively with pulse oximetry.

Energy metabolism and tissue blood flow as parameters for the assessment of graft viability in rat small bowel transplantation.

The assessment of small bowel graft viability by means of energy metabolism and tissue blood flow was investigated and compared with pathological findings. Syngeneic heterotopic small bowel transplantations were performed using male Lewis rats, which were divided into four groups according to the duration of cold preservation in University of Wisconsin (UW) solution; 6-, 12-, 24-, and 48-hour groups. The adenine nucleotide metabolism, the tissue blood flow, and the pathological profiles of the grafts were all compared among the groups. The adenosine triphosphate (ATP) levels at the end of cold storage and at 30 minutes after reperfusion, as well as the total adenine nucleotide (TAN) levels at the end of cold storage, before reperfusion, and at 30 minutes after reperfusion were significantly lower in the 48-hour group than those in the other groups, and the blood flow level at reperfusion was significantly lower in the 48-hour group than that in the others. Histological damage after reperfusion extended deep into the crypt layer in the 48-hour group but was confined to within villi in the other groups. These results suggest that the tissue ATP, TAN, and the blood flow levels are considered useful parameters for the assessment of small bowel graft viability.

In vivo fluorescence microscopy for the assessment of microvascular reperfusion injury in small bowel transplants in rats.

With the use of in vivo fluorescence microscopy we have analyzed microvascular reperfusion injury of small bowel isograft transplants in rats. Following 1 hr cold storage in University of Wisconsin solution, the small bowel was transplanted heterotopically, and the intestinal microcirculation was quantitatively analyzed 20-60 min after onset of reperfusion. The intestinal grafts' capillary perfusion of both the mucosa and the circular and longitudinal muscles was not found altered when compared with the intestinal capillary perfusion of sham-operated controls. In contrast, leukocyte-endothelial cell interaction, including leukocyte rolling (40 +/- 5%) and sticking (280 +/- 100 mm-2) in submucosal postcapillary venules, was significantly increased when compared with nontransplanted controls (12 +/- 8% and 20 +/- 10 mm-2, P < 0.01 and P < 0.05, respectively). Leukocyte-endothelial cell interaction was associated with a marked alteration of lymphatic capillary drainage, as indicated by the low functional density of lymphatic microvessels of 10.2 +/- 6.1 cm-1 (P < 0.01 vs. sham-operated controls (39.2 +/- 6.1 cm-1)). From these results we propose that leukocyte-endothelial cell interaction, not capillary "no-reflow," is the primary step in the manifestation of microvascular reperfusion injury following a short period of cold ischemia in small bowel grafts.