E. A. Deitch

There is increasing direct experimental and indirect clinical evidence to indicate that under certain conditions intestinal barrier function may be lost in trauma victims. No direct measurements, however, have been performed in patients to determine whether intestinal permeability is increased shortly after a major thermal injury in the absence of infection. Fifteen hemodynamically stable burn patients with burns on more than 20% of their body surface (39% +/- 12%) had their intestinal permeability measured within 24 hours of injury with use of the two nonmetabolizable sugars lactulose and mannitol as permeability markers. Lactulose absorption was fourfold higher in the patients (223 +/- 54 mumol) than in the controls (58 +/- 11 mumole; p less than 0.02), whereas the lactulose/mannitol ratio was threefold higher (5.2 vs 1.7; p less than 0.05). Thus intestinal permeability was increased in patients with moderate to major burn injuries shortly after injury.

The aim of this study was to test the hypothesis that the gut is capable of becoming a cytokine-generating organ following either a lethal or nonlethal inflammatory insult. Adult male rats were given an intraperitoneal challenge with saline, or with a nonlethal (.1 mg/g) or LD50 (.5 mg/g) dose of zymosan. Mesenteric lymph nodes, efferent mesenteric lymph, liver, spleen, and blood (portal and systemic) were obtained at 2, 4, 6, 8, or 10 h post challenge. Organs, lymph, and blood were tested for bacterial translocation (BT); blood and lymph were assayed for tumor necrosis factor (TNF) and IL-6. After .1 mg/g zymosan, BT was limited to the mesenteric lymph node complex only; .5 mg/g zymosan promoted BT to blood, mesenteric lymph, and organs (p < .05 vs. control or .1 mg/g zymosan). The magnitude of portal bacteremia was greater than systemic bacteremia (p < .003). Serum TNF peaked at 2 h (p < .05 vs. control), and serum IL-6 peaked at 4-6 h (p < .05 vs. control) post zymosan challenge. Portal and systemic bioactivity was similar for either cytokine, and serum bioactivity did not correlate with zymosan dose. TNF bioactivity was increased in the mesenteric lymph at 2 h post challenge with .5 mg/g zymosan only (p < .05 vs. control or .1 mg/g zymosan). IL-6 bioactivity was increased in the mesenteric lymph at 4 through 10 h post zymosan challenge (p < .05 vs. control), but was similar with either dosage of zymosan. In conclusion, the gut may be capable of producing cytokines in response to an inflammatory stimulus, even in the absence of portal or systemic spread of bacteria. The magnitude of the cytokine response does not correlate with the magnitude of bacterial translocation.

To determine whether the route and/or composition of nutritional support alters intestinal barrier function (measured as bacterial translocation), rats were divided into three groups: food (controls), intravenous total parenteral nutrition (IV-TPN) fed, and oral total parenteral nutrition (ORAL-TPN) fed. Bacterial translocation did not occur in the rats that were fed normally, but did occur in 60% of the rats fed the IV-TPN or the ORAL-TPN diets for 7 days (p less than 0.05). Since both the IV-TPN and ORAL-TPN diets induced bacterial translocation and the TPN solution (28% glucose and 4.5% amino acids) lacks fiber, two additional groups of rats were fed orally 2.5 gm cellulose powder/day plus TPN solution by either the intravenous or the oral route. The addition of cellulose powder decreased the incidence of bacterial translocation to 8% in the group fed the ORAL-TPN diet and to 0% in the group fed the IV-TPN diet. Cellulose improved intestinal barrier function, even though it did not prevent bacterial overgrowth or the loss of mucosal mass in the rats fed the IV-TPN or ORAL-TPN diets. Cellulose powder appears to have prevented bacterial translocation primarily by preventing IV-TPN- or ORAL-TPN-induced alterations in mucosal structure. Thus the oral administration of this fiber maintains intestinal barrier function and prevents bacterial translocation even in the absence of oral nutrients.

Previously, the authors documented that extrahepatic biliary obstruction promotes the systemic translocation of bacteria from the intestine to visceral tissues. The current experiments were performed to determine whether it was the absence of intestinal bile or the presence of biliary obstruction that promoted bacterial translocation. Four groups of rats were studied: 1) nonoperated controls (n = 20), sham common bile duct-ligated (n = 22), common bile duct-ligated (n = 25), and common bile duct-diverted (choledochovesical bypass) (n = 23). The sham-ligated group underwent laparotomy and manipulation of the portal region; whereas the ligated group had their common bile ducts ligated, while the choledochovesical group had a silastic tube placed from the common bile duct to the bladder. Seven days later, at death, the incidence of bacterial translocation was higher in the groups of rats subjected to common bile duct ligation (41%) or diversion (32%) than in the control (3%) or sham-ligated (5%) groups (P less than 0.05). Histologic sections of ileums of ligated and diverted animals both showed subepithelial edema. These findings suggest that it is primarily the absence of bile in the intestine that promotes mucosal injury and bacterial translocation and not biliary obstruction.

A prospective study was performed in two parts after sonographic determination of gallbladder wall thickness in 110 consecutive patients. The first part was designed to evaluate accuracy of sonographic measurements in 40 patients on whom intraoperative measurements of wall thickness were obtained. Second, the significance of wall thickness as an indicator of disease was explored by comparing the 40 surgical patients and 44 controls. Sonography was found to be accurate in determining wall thickness to within 1 mm in 93% of patients and 1.5 mm in 100%. Wall thickness greater than 3.5 mm is highly accurate in predicting disease; however, a wall thickness 3 mm or less does not rule out cholecystitis.