High-resolution, time-resolved MRA provides superior definition of lower-extremity arterial segments compared to 2D time-of-flight imaging.

PURPOSE: To evaluate a novel time-resolved contrast-enhanced (CE) projection reconstruction (PR) magnetic resonance angiography (MRA) method for identifying potential bypass graft target vessels in patients with Class II-IV peripheral vascular disease. MATERIALS AND METHODS: Twenty patients (M:F = 15:5, mean age = 58 years, range = 48-83 years), were recruited from routine MRA referrals. All imaging was performed on a 1.5 T MRI system with fast gradients (Signa LX; GE Healthcare, Waukesha, WI). Images were acquired with a novel technique that combined undersampled PR with a time-resolved acquisition to yield an MRA method with high temporal and spatial resolution. The method is called PR hyper time-resolved imaging of contrast kinetics (PR-hyperTRICKS). Quantitative and qualitative analyses were used to compare two-dimensional (2D) time-of-flight (TOF) and PR-hyperTRICKS in 13 arterial segments per lower extremity. Statistical analysis was performed with the Wilcoxon signed-rank test. RESULTS: Fifteen percent (77/517) of the vessels were scored as missing or nondiagnostic with 2D TOF, but were scored as diagnostic with PR-hyperTRICKS. Image quality was superior with PR-hyperTRICKS vs. 2D TOF (on a four-point scale, mean rank = 3.3 +/- 1.2 vs. 2.9 +/- 1.2, P < 0.0001). PR-hyperTRICKS produced images with high contrast-to-noise ratios (CNR) and high spatial and temporal resolution. 2D TOF images were of inferior quality due to moderate spatial resolution, inferior CNR, greater flow-related artifacts, and absence of temporal resolution. CONCLUSION: PR-hyperTRICKS provides superior preoperative assessment of lower limb ischemia compared to 2D TOF.

Imaging patients with "post-cholecystectomy syndrome": an algorithmic approach.

AIM: To assess the role of ultrasound (US), magnetic resonance cholangiopancreatography (MRCP) and liver function tests (LFTs) in the evaluation of selected patients presenting with late post-cholecystectomy syndrome (PCS) who were referred for endoscopic retrograde cholangiopancreatography (ERCP). MATERIALS AND METHODS: In a retrospective study a final group of 42 patients with PCS referred for diagnostic ERCP underwent MRCP and abdominal US. ERCP and MRCP images were assessed for bile duct diameters and the presence of strictures and stones. A common bile duct (CBD) diameter of < 10mm was considered normal, whereas > or = 10mm was considered abnormal on US. Findings were correlated to LFTs with contingency table results performed for single techniques and combination of methods. RESULTS: In total 14 stones and one stricture were seen. US had a high negative predictive value (86.4%). MRCP had a sensitivity of 100% and specificity of 88.0%. ERCP is the most accurate test but failed in 11 patients, five of whom had a stone. The accuracy of US and LFTs increases to 93.8% if test results agree in either negative or positive outcome. CONCLUSION: US and LFTs are first-line tests in PCS. If the CBD on US is > or = 10mm, but no cause is identified, MRCP should be performed. If US and LFTs are normal then MRCP is not necessary. The availability of LFTs raises the diagnostic value of imaging.

High-resolution multistation peripheral MR angiography using undersampled projection reconstruction imaging.

A novel protocol for three-station MR angiography (MRA) of the lower extremities is described. A time-resolved undersampled projection reconstruction (PR) acquisition was used to image the calf station during a first injection, and non-time-resolved PR acquisitions were used with the bolus-chase technique to image the abdomen and thigh stations during a second injection. The streak artifacts resulting from undersampling the PR data were reduced with the use of a spatial Fermi filter based on the sensitivity of each coil element in a peripheral vascular phased-array coil. This novel technique provided high spatial resolution and a broad range of coverage, and depicted the contrast dynamics in the most distal station of the lower extremities.

Artifact reduction in undersampled projection reconstruction MRI of the peripheral vessels using selective excitation.

The projection reconstruction (PR)-HyperTRICKS (time resolved imaging of contrast kinetics) acquisition integrates the benefits of through-plane Cartesian slice encoding and in-plane undersampled PR. It provides high spatial resolution both in-plane (about 1 mm(2)) and through-plane (1-2 mm), as well as relatively high temporal resolution (about 0.25 frames per second). However, undersampling artifacts that originate from anatomy superior or inferior to a coronal imaging FOV may severely degrade the image quality. In coronal MRA acquisitions, the slice coverage is limited in order to achieve high temporal resolution. In this report we describe an artifact reduction method that uses selective excitation in PR-HyperTRICKS. This technique significantly reduces undersampling streak artifacts while it increases the slice coverage.

Hepatic metastases from an unknown primary neoplasm (UPN): survival, prognostic indicators and value of extensive investigations.

AIM: The objectives of this study were to identify prognostic features for patients with hepatic metastases and unknown primary neoplasms (UPN), determine the common primary tumours, assess the value of diagnostic tests in finding these tumours, and evaluate the impact of therapy and knowledge of the primary tumour on patient survival. MATERIALS AND METHODS: Eighty-eight patients with UPN and liver biopsy proven hepatic metastases over a 10-year period were reviewed (M:F, 58:30; age range 27-91 years, median 64.5 years). Histopathology, diagnostic investigations and success at identifying the primary neoplasm were recorded. In addition, in 70 patients with adenocarcinoma histology (M:F, 48:22; age range 27-91 years, median 65 years), treatment and survival data from the date of biopsy were recorded. RESULTS: The histological spectrum included adenocarcinoma in 70, neuroendocrine in four, squamous cell carcinoma in four, small cell carcinoma in four, carcinoid in two, hepatoma in one and three others. Extensive investigation identified a primary neoplasm in 16/88 patients (18%) including colorectal in six, gastric in two, lung in four, oesophageal in two, prostate in one and carcinoid in one. In the adenocarcinoma group survival data were available for 62/70 patients. Sixteen of 62 patients received active treatment with either surgery, chemotherapy, radiotherapy or a combination protocol. Forty-six of 62 patients received palliative care alone. Median survival for the adenocarcinoma group overall was 49 days. The median survival for treated patients (49 days) versus untreated patients (52 days) was not significantly different (P=0.128). Patients <65 years were more likely to receive active treatment than those >65 years (P=0.006). Age with a hazard ratio (HR) of 1.01 (P=0.178), active treatment (HR=0.65;P=0.194), knowledge of the primary neoplasm (HR=0.60;P=0.213) and male gender (HR=0.88;P=0.642) had no significant effect on survival. CONCLUSION: Although hepatic metastases are associated with poor prognosis, it is essential that a liver biopsy be performed to obtain a histological diagnosis. Adenocarcinoma metastases carry a dismal prognosis, and no prognostic factors, including knowledge of the primary tumour, are significant for patient survival. Extensive investigation is not warranted in patients with adenocarcinoma liver metastases.

Percutaneous radiologic gastrostomy with and without T-fastener gastropexy: a randomized comparison study.

PURPOSE: T-fastener gastropexy is used by many interventional radiologists during percutaneous radiologic gastrostomy (PRG) placement. Whether gastropexy is a prerequisite to safe gastrostomy placement is uncertain. We evaluated the use of T-fastener gastropexy versus no gastropexy for PRG in a prospective, randomized study. METHODS: Of 90 consecutive patients referred for PRG, 48 were randomly selected to receive T-fastener gastropexy (M:F, 35:13; mean age 62 years, range 20-90 years) and 42 to receive no gastropexy (M:F, 31:11; mean age 63 years, range 40-90 years). Technical difficulties and fluoroscopy times were recorded for both groups and all patients were followed up for postprocedural complications. T-fasteners were removed between 3 and 7 days after gastrostomy insertion. RESULTS: A major complication was encountered in four patients from the non-gastropexy group (10%). In these cases the guidewire and dilator "flipped" out of the stomach into the peritoneal cavity. This resulted in misplacement of the gastrostomy tube in the peritoneal cavity in two of the patients. This was discovered at the end of the procedure when a test injection of contrast medium was performed. In three of these patients the procedure was rescued and completed radiologically. One patient underwent endoscopic gastrostomy placement. Five of 48 patients (10%) who received a gastropexy had pain associated with the T-fastener sites. Six patients (13%) had skin excoriation at the T-fastener sites. No skin complications were seen in the non-gastropexy group. No statistical difference in fluoroscopy time was observed between the two groups. CONCLUSION: Our experience of PRG without T-fastener gastropexy involved a 10% incidence of serious technical complications. We suggest that T-fastener gastropexy should be performed routinely for all PRG procedures. T-fastener gastropexy has an associated minor complication of pain and skin excoriation at the gastrostomy site which resolves on removing the T-fasteners.

Helical CT evaluation of the perirenal space and its boundaries: a cadaveric study.

PURPOSE: To determine whether the perirenal spaces communicate across the midline and with the pelvic extraperitoneal spaces. MATERIALS AND METHODS: Helical CT was used to guide the sequential injection of 100-mL intravenous boluses of dilute contrast medium, up to 300 mL, into the perirenal space of eight embalmed cadavers (three male, five female; mean age at death, 82 years; range, 72-93 years), with four left-sided and four right-sided injections. All images were acquired after the final injection (300 mL total) to facilitate coronal and sagittal reconstruction of relevant images. All images were reviewed to assess the flow pathways of contrast medium from the perirenal space to other retroperitoneal spaces. RESULTS: In three cadavers that received left perirenal space injections and in two cadavers that received right perirenal space injections, communication was seen with the contralateral perirenal space through an area anterior to the aorta and inferior vena cava. In three cadavers that received right perirenal space injections, contrast material flowed from the right perirenal space to outline the bare area of the liver. Communication between the perirenal and pelvic extraperitoneal spaces was seen in all eight cadavers; contrast material extended into the pelvic extraperitoneal and presacral spaces. CONCLUSION: These findings show that the perirenal spaces communicate with each other across the midline and with the pelvic extraperitoneal spaces. Clinical implications are that perinephric collections can potentially flow into the pelvis or across the midline.

Tophaceous gout of the lumbar spine in a renal transplant patient: a case report and literature review.

Tophaceous gout of the spine is rare. We report the case of a 27-year-old male, renal transplant recipient, who presented with an acute onset of lower back pain. Radiological, biochemical and histo-pathological findings confirmed a diagnosis of tophaceous gout of the lumbar spine. We present the case history with the radiological findings and discuss the literature.

Percutaneous gastrostomy in patients who fail or are unsuitable for endoscopic gastrostomy.

PURPOSE: Percutaneous endoscopic gastrostomy (PEG) is not possible or fails in some patients. We aimed to categorize the reasons for PEG failure, to study the success of percutaneous radiologic gastrostomy (PRG) in these patients, and to highlight the associated technical difficulties and complications. METHODS: Forty-two patients (28 men, 14 women; mean age 60 years, range 18-93 years) in whom PEG failed or was not possible, underwent PRG. PEG failure or unsuitability was due to upper gastrointestinal tract obstruction or other pathology precluding PEG in 15 of the 42 patients, suboptimal transillumination in 22 of 42 patients, and advanced cardiorespiratory decompensation precluding endoscopy in five of 42 patients. T-fastener gastropexy was used in all patients and 14-18 Fr catheters were inserted. RESULTS: PRG was successful in 41 of 42 patients (98%). CT guidance was required in four patients with altered upper gastrointestinal anatomy. PRG failed in one patient despite CT guidance. In the 16 patients with high subcostal stomachs who failed PEG because of inadequate transillumination, intercostal tube placement was required in three and cephalad angulation under the costal margin in six patients. Major complications included inadvertent placement of the tube in the peritoneal cavity. There was one case of hemorrhage at the gastrostomy site requiring transfusion and one case of superficial gastrostomy site infection requiring tube removal. Minor complications included superficial wound infection in six patients, successfully treated with routine wound toilette. CONCLUSION: We conclude that PRG is a safe, well-tolerated and successful method of gastrostomy and gastrojejunostomy insertion in the technically difficult group of patients who have undergone an unsuccessful PEG. In many such cases optimal clinical evaluation will suggest primary referral for PRG as the preferred option.

Enhancement of fibroblast collagen synthesis by nitric oxide.

Fibroblasts can be stimulated by cytokines to synthesize nitric oxide (NO, nitrogen monoxide), while wound-derived fibroblasts synthesize NO spontaneously. Since wound fibroblasts are phenotypically characterized by greater collagen synthesis when compared to fibroblasts derived from noninjured tissue, we hypothesized that there may be a correlation between wound-induced NO synthesis and enhanced collagen production. To study the role of NO on collagen metabolism, normal dermal fibroblasts were cultured in the presence or absence of the NO donor S-nitroso-N-acetyl-penicillamine (SNAP) and their collagen metabolism was studied on the transcriptional as well as translational level. Fibroblast collagen synthesis was enhanced by 74.3 +/- 18.2 and 87.5 +/- 28.2% in the presence of 100 and 400 microM SNAP, respectively. This effect was not due to increased collagen type I or type III gene transcription. Cellular proliferation measured by thymidine incorporation was significantly decreased in the presence of SNAP, indicating that the increased collagen production was due to a net increase of collagen synthesis by the cells. Investigation of the collagen breakdown pathway showed that neither collagenase gene expression nor collagenase protein expression was affected by SNAP. The results of this study demonstrate for the first time that NO enhances collagen synthesis, most likely at a posttranslational level.

Expression and function of inducible nitric oxide synthase during rat colon anastomotic healing.

Nitric oxide plays a significant but incompletely understood role in fibroblast function and cutaneous wound collagen synthesis; however, the participation of inducible nitric oxide synthase (iNOS) in gastrointestinal anastomotic healing has not been studied. Male Sprague-Dawley rats underwent single-layer left colonic anastomosis. Animals were killed at 24-hour intervals postoperatively and the anastomosis was excised. Parallel uninjured colon tissue samples were also analyzed. Reverse transcriptase-polymerase chain reaction confirmed the absence of iNOS messenger RNA in control colon and expression of the gene in anastomotic tissue on all study days. Northern hybridization demonstrated maximal iNOS messenger RNA transcription on day 1 with decreased levels on days 3 and 5. iNOS enzyme activity, measured biochemically by the conversion of [(3) H-arginine to [(3) H]-citrulline ex vivo, was also maximal on day 1 (7.35 +/- 1.34 pmol/mg protein/min [+/- standard error of the mean], n = 10) and decreased on days 3 (4.37 +/- 2.32 pmol/mg protein/min; n = 6) and 5 (2.80 +/- 0.92 pmol/mg protein/min; n = 6). Immunohistochemical staining demonstrated that (1) iNOS expression is confined to a discrete cell population in the region of the anastomosis containing inflammatory cells; (2) those cells assume a highly conserved position on the luminal edge of the proliferating scar; and (3) the iNOS-expressing cells are present throughout the fibroplastic phase of healing. To functionally assess the role of iNOS in colonic healing, rats were treated with a continuous intravenous infusion of S-methylisothiourea (a selective inhibitor of iNOS) at a dosage of 200 mg/kg/day for 5 days after anastomosis. There was a significantly reduced anastomotic bursting pressure in rats treated with the inhibitor as compared to rats treated with intravenous normal saline solution (108.4 +/- 13.2 mm Hg vs. 148.4 +/- 10.3 mm Hg; P <0.05). These results suggest that iNOS gene expression is induced during colonic anastomotic healing, that it is present through all phases of healing but is maximal through the inflammatory phase, and that iNOS activity is required for optimal anastomotic healing.

Inhibition of nitric oxide synthesis in wounds: pharmacology and effect on accumulation of collagen in wounds in mice.

OBJECTIVE: To investigate the effect of systemic inhibition of nitric oxide (NO) synthesis in wounds on collagen accumulation. DESIGN: Randomised experimental study. SETTING: Teaching hospital, USA. MATERIAL: 240 Balb/C mice divided into groups of 10 animals each. INTERVENTIONS: Polyvinyl alcohol sponges were inserted subcutaneously through a dorsal skin incision. Beginning on the day of wounding, N omega-nitro-L-arginine-methylester (L-NAME), NG-L-monomethyl-arginine (L-NMMA), aminoguanidine hemisulphate (AGU), and S-methyl isothiouronium (MITU) were given orally or intraperitoneally. The mice were killed 10 days later. MAIN OUTCOME MEASURES: Nitrite and nitrate concentrations, both stable end products of NO, were measured in wound fluid. Sponge hydroxyproline content was assayed as an index of reparative collagen deposition. RESULTS: NOS inhibitors given orally in the drinking water or by daily intraperitoneal injection had no effect on wound nitrite/nitrate concentrations or deposition of collagen in wounds. When given continuously through intraperitoneally-placed osmotic pumps, AGU (500 mg/kg/day) (p < 0.001) and MITU (p < 0.01) significantly reduced wound fluid nitrite/nitrate concentrations in a dose dependent manner. Inhibition of wound nitric oxide synthase by 500 mg AGU/kg/day and 100 mg MITU/kg/day was paralleled by lowered accumulation of collagen in wounds (p < 0.01). CONCLUSION: NO is beneficial in wound healing.

The route of nutrition support affects the early phase of wound healing.

BACKGROUND: Nutrition support via the enteral route has been shown to be superior to parenteral administration in maintaining immune function, decreasing septic complications, and increasing survival after severe trauma and surgical injury. Whether the route of nutrition support affects wound healing, another important determinant of outcome following injury, is not known. METHODS: Forty-nine Sprague-Dawley rats, 290 to 360 g body wt, underwent identical surgical manipulation consisting of central venous catheterization, fashioning of gastrostomy and dorsal skin incision, and placement of polyvinyl alcohol sponges into subcutaneous pockets. Identical infusates of 25% dextrose, 4.25% amino acids, and vitamins were given, half the animals receiving the infusion via the gastrostomy and the other half via the venous catheter. Animals were killed on day 5, 7, or 10. Wound breaking strength, sponge hydroxyproline content (an index of wound collagen deposition), and types I and III collagen gene expression were measured. RESULTS: There were no nutritional differences between the two groups in terms of energy intake, body weight gain, and plasma levels of albumin, total protein, or urea nitrogen. On day 5 wound breaking strength was significantly higher in the enterally supported group (89.3 +/- 90.7 vs 64.9 +/- 40.2 g for the parenteral group, p < .05). This was paralleled by enhanced wound collagen accumulation (182 +/- 19 vs 132 +/- 13 microg, p < .05). Gene expression of type I, but not type III, collagen also was increased in the enterally fed group. There were no differences noted between the two groups in wound healing parameters 7 and 10 days after injury. CONCLUSIONS: The data demonstrate that the route of nutrition administration can influence wound healing. The beneficial effect of the enteral feeding route is limited to the early phases of healing.

Metalloproteinase inhibitors and wound healing: a novel enhancer of wound strength.

BACKGROUND: Wound strength is a balance between collagen synthesis and degradation. The role of collagen breakdown in wound healing is still not well understood. We investigated the role of collagenases (metalloproteinases [MMPs]) in wound healing in using GM6001, a novel inhibitor of MMPs. METHODS: We used the dorsal skin incision model with implantation of polyvinyl alcohol sponges. Twenty male Sprague-Dawley rats were randomly assigned to receive either GM6001 (10 mg/kg body weight) or 2 mL saline subcutaneously. Ten days after operation the animals were killed and fresh wound breaking strength, scar and sponge hydroxyproline content, and collagen type I gene expression in sponges were assayed. In addition, the inflammatory response and the wound fluid cytokine (tumor necrosis factor-alpha [TNF-alpha] and transforming growth factor-beta 1 [TGF-beta 1]) profile were studied. RESULTS: GM6001 significantly increased wound strength (422 +/- 59 vs 302 +/- 33 g, P < .05), whereas scar collagen content did not differ. In the sponge granulomas the inflammatory infiltrate, the collagen content, and the collagen type I gene expression were all significantly decreased by GM6001. CONCLUSIONS: Inhibition of MMP activity during acute wound healing enhances wound strength even though new collagen synthesis and the inflammatory response are significantly decreased. This could be achieved by decreasing collagen turnover or increasing collagen maturation and crosslinking, or both.

Enhanced collagen accumulation following direct transfection of the inducible nitric oxide synthase gene in cutaneous wounds.

Inducible nitric oxide synthase (iNOS) is expressed during cutaneous wound repair. Mounting evidence suggests that wound nitric oxide (NO) augments collagen accumulation. We hypothesized that in vivo transfection of wound cells with the iNOS gene would increase physiological wound NO levels and thus augment collagen accumulation. Polyvinyl alcohol sponges were instilled with a mammalian expression plasmid (pMP6) containing either the chloramphenicol acetyl transferase (CAT) reporter or murine iNOS gene driven by a CMV immediate-early promoter. Plasmid DNA was injected alone or in complex with cationic liposomes, and the sponges were placed subcutaneously in male Sprague-Dawley rats which had received a longitudinal dorsal midline incision. Animals were sacrificed at different time points post-wounding and the sponges assayed for CAT activity, transfected iNOS mRNA, total nitrate and nitrite concentration (NOx) (as an index of wound NO synthesis), and hydroxyproline content (as an index of sponge collagen accumulation). The results demonstrate that wound cells were more efficiently transfected by naked DNA than by liposome mediated transfection and that maximal expression of both iNOS and CAT occurred at 48 hrs with a rapid decline after this time point. After 7 days, iNOS transfected sponges had accumulated significantly more collagen than those transfected with CAT. We conclude that cutaneous wounds can be successfully transfected by direct injection of naked DNA and that increased iNOS expression precedes an increase in collagen synthesis.

Healing in the gastrointestinal tract.

Healing in the GI tract is rapid when free of complications: Unlike cutaneous healing, in which progress can be observed on a daily basis and intervention instituted early if necessary, healing of the intestinal anastomosis is anatomically obscured from inspection, allowing the surgeon only the patient's parameters of general well-being to judge the success of the operation. For the same reason, complications usually require re-operation, with the associated morbidity of a laparotomy and additional general anesthetic. This places a great responsibility on the surgeon to be cognizant of all the preoperative, intraoperative, and postoperative factors relating to anastomotic healing that might compromise the healing process. Bearing these in mind, along with attention to technical detail, should limit complications to an acceptable level. Patients most at risk are (1) those who perioperatively develop physiologic problems that lead to shock, hypoxia, and resultant anastomotic ischemia, (2) those with radiation-induced tissue injury, (3) those with sepsis, and (4) those with preoperative bowel obstruction. Malnourishment, malignancy, diabetes, steroids, and age also influence outcome to varying degrees. Future advancement in the field of GI healing lies in our ability to manipulate the early struggle between collagen synthesis and collagen breakdown. A profound understanding of the molecular and biochemical pathways and the factors that control them will bring us closer to this goal. Clinically, this may be accomplished by the introduction of wound healing enhancers into the anastomotic site, possibly by incorporating them into suture materials, biofragmentable anastomotic rings, or staple materials. Already much is known about the influence of different cytokines and growth factors on collagen regulation, knowledge that will help resolve many of the long-standing problems associated with GI surgery.

Diabetes-impaired healing and reduced wound nitric oxide synthesis: a possible pathophysiologic correlation.

BACKGROUND: Nitric oxide (NO) is synthesized in wounds, but its role in the healing process is not fully understood. The inhibition of NO production during wound healing is accompanied by decreased wound reparative collagen deposition. To further define the role of NO in reparative collagen accumulation, we studied its production during diabetes-induced wound healing impairment. METHODS: Male Sprague-Dawley rats (290 to 310 gm) were rendered diabetic by intraperitoneal streptozotocin administration. Seven days after induction of diabetes (blood glucose greater than 300 mg/dl), the rats underwent dorsal skin incision and subcutaneous implantation of polyvinyl alcohol sponges. Beginning on the day of wounding, 21 diabetic animals were treated with 3 units/day insulin via intraperitoneally implanted miniosmotic pumps. Ten days after injury, wound breaking strength was determined, and wound collagen accumulation and types I and III collagen gene expression were measured in subcutaneously implanted polyvinyl alcohol sponges. NO-synthesis, as measured by nitrite/nitrate accumulation, was determined in wound fluid and in supernatants of wound cell cultures. RESULTS: Streptozotocin-induced diabetes markedly impaired wound breaking strength and collagen deposition. A parallel decrease occurred in wound NO synthesis as reflected by decreased nitrite/nitrate concentration in wound fluid and in diminished ex vivo NO production by wound cells. Insulin treatment partially but significantly improved wound mechanical strength (p < 0.01) and collagen accumulation (p < 0.001). Decreased wound NO accumulation and ex vivo NO production by wound cells were also partially restored by insulin treatment. CONCLUSIONS: Impaired diabetic wound healing is paralleled by decreased wound NO synthesis, supporting the hypothesis that NO plays a significant role in wound reparative collagen accumulation.

Sepsis impairs anastomotic collagen gene expression and synthesis: a possible role for nitric oxide.

Although intra-abdominal sepsis is known to impair colon healing by inhibiting anastomotic collagen synthesis, the effect of systemic sepsis on this process is unknown. Endotoxins and cytokines associated with sepsis induce nitric oxide synthesis both systemically and locally within colonic tissue. We hypothesized that systemic sepsis impairs colonic healing and examined a possible correlation with nitric oxide expression. Male Sprague-Dawley rats received intraperitoneal injections of either saline (sham group) or Escherichia coli endotoxin (lipopolysaccharide 1 mg/100 g body weight) at Times -24 and -12 hr (LPS group). All animals underwent laparotomy and left colonic anastomosis at Time 0. At 24 and 96 hr postlaparotomy rats were sacrificed, the anastomoses excised, and [3H]-proline incorporation into protein measured as an index of total new protein synthesis (TNP). Digestion with purified collagenase yielded incorporation into the collagen fraction (CDP). Additional sham and LPS-treated rats were sacrificed at 24, 72, and 120 hr, the anastomoses excised, and nitric oxide synthase activity in the tissue measured by the conversion of [3H]-arginine to [3H]citrulline in an ex vivo culture system. Finally, sham and LPS rats were sacrificed at 120 hr for measurement of colon anastomotic bursting pressure. Systemic sepsis significantly impaired new collagen synthesis in anastomotic tissue at 24 hr compared to control samples (P < 0.02). No difference was noted at 96 hr. TNP synthesis was similar in both groups at 24 or 96 hr. Northern blot analysis confirmed a significant decrease in Type I and Type III collagen mRNA expression at 24 hr in septic rats. Anastomotic bursting pressure was also decreased in the septic group (P < 0.003). Sepsis elevated nitric oxide synthase activity in anastomotic tissue 24 hr postanastomosis, when compared to sham tissue (P < 0.0001). These data suggest that systemic endotoxin induces nitric oxide synthesis at the anastomotic site. The simultaneous dysregulation of collagen gene expression and synthesis with decreased anastomotic strength suggests a possible regulatory role for nitric oxide in gastrointestinal healing.

Nitric oxide, an autocrine regulator of wound fibroblast synthetic function.

Nitric oxide (NO) is synthesized in wounds, but its exact role and cellular source are not known. Wound fibroblasts (WF) are phenotypically characterized by increased collagen synthesis and contractility. We hypothesized that WF may be also phenotypically altered during wound healing to synthesize NO. WF were isolated from polyvinyl alcohol sponges implanted in male Lewis rats and harvested 10 days later. Proliferation in response to 10% fetal bovine serum was assessed by [3H]thymidine incorporation in a microculture system. A fibroblast-populated collagen lattice was used for assaying contractility. Collagen synthesis was determined by measuring the collagenase-sensitive fraction of protein-incorporated [3H]proline. Fibroblasts were incubated in the presence or the absence of 0.5 mM S-methyl-isothio-uronium or 0.5 mM N-monomethyl-L-arginine, both competitive inhibitors of NO synthase. WF spontaneously synthesize and release NO (4.60 +/- 0.29 nmol nitrite/microg DNA/48 h). Normal dermal fibroblasts do not synthesize NO. WF NO synthesis was limited to the first and second passages postharvest and was inhibitable by S-methyl-isothio-uronium (96%) and N-monomethyl-L-arginine (84%). In vivo iNOS expression by WF was confirmed by in situ hybridization and immunohistochemistry. Inhibition of endogenous NO synthesis had no effect on fibroblast proliferation. However, fibroblast-mediated collagen contraction was enhanced (p < 0.01), and collagen synthesis was significantly decreased (p < 0.05) by inhibiting NO synthase. The data show that WF are phenotypically altered during the healing process to synthesize NO, which, in turn, regulates their collagen synthetic and contractile activities.

Wound healing in sepsis and trauma.

Wound healing represents a dynamic and immediate response of the body to tissue injury with the purpose of restoring anatomical continuity, structure and function. Success or failure of this complex cascade of events is determined largely by competence of the host's immune system. Sepsis represents one of the most formidable threats to successful wound healing. It can present as a local bacterial colonization of the injury site with minimal systemic reaction or the "systemic inflammatory response syndrome," a primary cause of mortality among critically ill patients. Trauma also predisposes patients to wound complications especially as a result of post-traumatic immunosuppression. This phenomenon exposes the patient to the risk of microbial infection and ultimately the sepsis syndrome. The immune system, therefore, represents a vulnerable gateway through which trauma and sepsis exert their deleterious effect on the wound healing process resulting in increased morbidity and mortality for the surgical patient.