Diffusion-weighted imaging as predictor of therapy response in an animal model of Ewing sarcoma.

OBJECTIVES: To evaluate the potential of diffusion-weighted imaging (DWI) for monitoring dose-dependent tumor response in a mouse-xenograft model of Ewing sarcoma after administration of treosulfan in different dosages. MATERIALS AND METHODS: Ewing sarcoma implanted orthotopically into the left thigh of non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice were evaluated with a 9.4 T MR unit by using a specific mouse whole body coil. Transverse T2-weighted fast spin-echo sequences, T1-weighted spin-echo sequences, and transverse echo-planar DWI examinations were performed at baseline, 24 hours and 72 hours after intraperitoneal injection of treosulfan in 2 different doses. The apparent diffusion coefficient (ADC) in the viable parts of the tumor was automatically calculated from DWI imaging findings. These findings were correlated with histopathologic results at each time point. Volumetric measurements were performed by summing up the regions of interest in consecutive slices. RESULTS: T1- and T2-weighted images before administration of treosulfan showed viable tumor tissue with small necrotic areas. At 24 hours after treosulfan injection, a significantly higher increase in ADC in the viable parts of the tumor could be observed in tumors of mice that had been injected with the higher dose of treosulfan compared with mice injected with the lower dose treosulfan, whereas no significant volumetric differences between the 2 different doses could be observed. Seventy-two hours after injection of treosulfan the ADC values in the viable parts of the tumor of mice treated with the high dose of treosulfan further increased and the tumor volume in the high-dose group was now significantly lower than in the low-dose group. CONCLUSION: Compared with volumetric measurements, DWI of the viable tumor parts could be used to discriminate between the effects of 2 different dosages at an earlier time point than volumetric measurements in an animal model in vivo. This method could be especially useful for monitoring drug effects in phase I/II clinical trials.

Impact of different crystalloid volume regimes on intestinal anastomotic stability.

BACKGROUND: Anastomotic insufficiency still remains an unsolved problem in digestive surgery. Little clinical data, regarding the impact of perioperative volume management exist, which suggest lower complication rates in intestinal surgery under restrictive volume regimens. The aim of our study was to investigate the effect of the extent of intraoperative fluid administration with crystalloids on the stability of intestinal anastomoses. MATERIAL AND METHODS: Twenty-one rats were randomly assigned to 3 experimental groups (n = 7 rats/group): control group CO (9 mL kg h crystalloid infusion), volume restriction group V (-) (3 mL kg h), and animals with volume overload V (+) (36 mL kg h). After midline incision, all animals received the corresponding infusion for a 30-minute period. Infusion was continued for further 30 minutes whereas an end-to-end small bowel anastomosis was performed 15 cm proximal to the Bauhin valve with 8 nonabsorbable interrupted inverting sutures. At reoperation on the 4th postoperative day, the anastomotic segment was dissected and the bursting pressure [mmHg] was measured. As a second parameter for the quality of anastomotic healing, hydroxyproline concentration was examined with a spectrophotometric method [microg/g dry tissue]. Histologically, structural changes of the anastomotic segments were assessed by 2 pathologists. Data are given as mean +/- SEM. RESULTS: Anastomotic insufficiency was not seen in all animals. Bursting pressure of CO animals was 102 +/- 8 mmHg. Bursting pressure was lowest in V (+) with high volume exposure at 77 +/- 6 mmHg and significantly lower than V (-) (112 +/- 9 mmHg; P = 0.01) whereas the difference compared with the CO group did not reach significant values. Hydroxyproline concentration in V (+) (64.4 microg/g dry tissue +/- 7.7) was significantly lower compared with V (-) (91.7 microg/g dry tissue +/- 9.1) animals (P < 0.05). In all animals with volume overload a marked submucosal edema was found. CONCLUSION: We could demonstrate for the first time in a systematic investigation, that the quantity of crystalloid infusion, applied intraoperatively, has a significant impact on functional (bursting pressure) and structural (hydroxyproline) stability of intestinal anastomoses in the early postoperative period. Because the stability and quality of an intestinal anastomosis have an impact on insufficiency rates, it should be noted that volume overload may have deleterious effects on anastomotic healing and postoperative complications in digestive surgery, possibly because of a marked bowel wall edema.

Complete pancreatic encasement of the portal vein--surgical implications of an extremely rare anomaly.

BACKGROUND: Due to the complex embryologic development, pancreatic anatomy can be very variable. DISCUSSION: The authors present the second ever reported case in the literature of a complete pancreatic encasement of the portal vein which forced us to alter the standard operative procedure of pancreatic head resection, thus enabling possible dangerous complications.