Stefan M. Niehues

Prediction of Postoperative Outcome After Hepatectomy With a New Bedside Test for Maximal Liver Function Capacity

Objective:To validate the LiMAx test, a new bedside test for the determination of maximal liver function capacity based on 13C-methacetin kinetics. To investigate the diagnostic performance of different liver function tests and scores including the LiMAx test for the prediction of postoperative outcome after hepatectomy. Summary Background Data:Liver failure is a major cause of mortality after hepatectomy. Preoperative prediction of residual liver function has been limited so far. Methods:Sixty-four patients undergoing hepatectomy were analyzed in a prospective observational study. Volumetric analysis of the liver was carried out using preoperative computed tomography and intraoperative measurements. Perioperative factors associated with morbidity and mortality were analyzed. Cutoff values of the LiMAx test were evaluated by receiver operating characteristic. Results:Residual LiMAx demonstrated an excellent linear correlation with residual liver volume (r = 0.94, P < 0.001) after hepatectomy. The multivariate analysis revealed LiMAx on postoperative day 1 as the only predictor of liver failure (P = 0.003) and mortality (P = 0.004). AUROC for the prediction of liver failure and liver failure related death by the LiMAx test was both 0.99. Preoperative volume/function analysis combining CT volumetry and LiMAx allowed an accurate calculation of the remnant liver function capacity prior to surgery (r = 0.85, P < 0.001). Conclusions:Residual liver function is the major factor influencing the outcome of patients after hepatectomy and can be predicted preoperatively by a combination of LiMAx and CT volumetry.

Low-dose computed tomography to detect body-packing in an animal model

OBJECTIVE To assess the possible extent of dose reduction for low-dose computed tomography (CT) in the detection of body-packing (ingested drug packets) as an alternative to plain radiographs in an animal model. MATERIALS AND METHODS Twelve packets containing cocaine (purity >80%) were introduced into the intestine of an experimental animal (crossbred pig), which was then repeatedly examined by abdominal CT with stepwise dose reduction (tube voltage, 80 kV; tube current, 10-350 mA). Three blinded readers independently evaluated the CT datasets starting with the lowest tube current and noted the numbers of packets detected at the different tube currents used. In addition, 1 experienced reader determined the number of packets detectable on plain abdominal radiographs and ultrasound. RESULTS The threshold for correct identification of all 12 drug packets was 100 mA for reader 1 and 125 mA for readers 2 and 3. Above these thresholds all 3 readers consistently identified all 12 packets. The effective dose of a low-dose CT scan with 125 mA (including scout view) was 1.0 mSv, which was below that of 2 conventional abdominal radiographs (1.2 mSv). The reader interpreting the conventional radiographs identified a total of 9 drug packets and detected 8 packets by abdominal ultrasound. CONCLUSIONS Extensive dose reduction makes low-dose CT a valuable alternative imaging modality for the examination of suspected body-packers and might replace conventional abdominal radiographs as the first-line imaging modality.

Liver volume measurement: reason of the difference between in vivo CT-volumetry and intraoperative ex vivo determination and how to cope it

PurposeVolumetric assessment of the liver regularly yields discrepant results between pre- and intraoperatively determined volumes. Nevertheless, the main factor responsible for this discrepancy remains still unclear. The aim of this study was to systematically determine the difference between in vivo CT-volumetry and ex vivo volumetry in a pig animal model.Material and MethodsEleven pigs were studied. Liver density assessment, CT-volumetry and water displacement volumetry was performed after surgical removal of the complete liver. Known possible errors of volume determination like resection or segmentation borders were eliminated in this model. Regression analysis was performed and differences between CT-volumetry and water displacement determined.ResultsMedian liver density was 1.07 g/ml. Regression analysis showed a high correlation of r2 = 0.985 between CT-volumetry and water displacement. CTvolumetry was found to be 13% higher than water displacement volumetry (p < 0.0001).ConclusionIn this study the only relevant factor leading to the difference between in vivo CT-volumetry and ex vivo water displacement volumetry seems to be blood perfusion of the liver. The systematic difference of 13 percent has to be taken in account when dealing with those measures.

Miniature pigs as an animal model for implant research: bone regeneration in critical-size defects

OBJECTIVE Standardized experimental investigations determining the critical-size defect (CSD) in the mandible of miniature pigs are still lacking. The aim of the present study was to obtain information about the new bone formation in created defects of varying sizes. STUDY DESIGN Marginal resection of the alveolar crest of the lower jaw was performed in 3 female miniature pigs. The animals used in the study were 3 years of age and weighed approximately 55 kg. For histologic evaluation the dental implants were harvested with the surrounding bone tissue 10 weeks after implant placement. For this, bone segments including the implants were removed from each side of the mandible. The sizes of the resected bone blocks varied, showing the following volumes: 10.1 cm(3), 4.2 cm(3), and 1.9 cm(3). Periosteal coverage of the defects was performed. Computerized tomography (CT) of the skull of the miniature pig was performed immediately after the surgical procedure as well as 6 weeks later using a 64-channel mult-slice scanner. RESULTS The CT showed that 6 weeks after obtaining the biopsies, the filling of the defects with new bone varied. The percentage of newly formed bone in relation to the size of the original defect was 57.4% for the small- and 87.2% for the middle-sized defect. The large-sized defect showed 75.5% newly formed bone compared with baseline. CONCLUSION Considering the amount of new bone formation found within this study, it is questionable if the critical defect size of 5 cm(3) stated in the literature is valid. Further research concerning the mandibular model in minipigs is required and more refinement needed to assure a standardized CSD, allowing qualitative and quantitative evaluation of bone grafts and bone graft substitutes.

Successful repair of post-transplant mycotic aneurysm of iliac artery with renal graft preservation: a case report.

OBJECTIVE To describe the successful repair of a post-transplant iliac artery aneurysm with renal graft preservation. METHODS An aneurysm was detected in an asymptomatic 47-year-old male recipient on routine Doppler ultrasonography that involved the right external iliac artery and the distal portion of the renal artery. Aneurysm resection was performed immediately after diagnosis 3 months after transplantation. A polytetrafluorethylene tube graft was used for reconstruction of the right external iliac artery. Reconstruction of the renal artery required interposition of a vena saphena graft between the proximal portion of the renal artery and the polytetrafluorethylene tube. RESULTS The total warm ischemia time used for aneurysm repair and renal transplant revascularization was 90 minutes. The postoperative Doppler ultrasound scan showed homogeneous graft perfusion. Pathologic and microbiologic examination of the resected aneurysm revealed Candida albicans arteritis. The center in which the contralateral donor kidney was transplanted had previously reported Candida albicans contamination of the preservation solution. The recipient of the contralateral kidney lost his graft owing to bleeding complications. Information on this incident was acquired by our center only after aneurysm repair. Postoperatively, our recipient was given systemic antifungal therapy. At 6 months, the serum creatinine level was 1.7 mg/dL. CONCLUSION Although a high-risk procedure, repair of a mycotic aneurysm with renal graft preservation is feasible. Routine microbiologic screening of the preservation solution might help to detect and treat donor-transmitted infections in renal transplant recipients.

The impact of the emergence of internet hospital rating sites on patients’ choice: a quality evaluation and examination of the patterns of approach

Internet healthcare rating has become a viable tool for guiding patients in making health decisions and already established for medical practitioners. Rating has recently been extended to hospitals. The aim of this study is to describe the basic features of internet healthcare rating sites, to show different approaches and their implementation, and to reveal the possible risks associated with such rating sites. By way of example, we analysed three German and one US hospital rating site to illustrate the various viewpoints and to outline a possible future for rating structures. As a result, we showed that a broad range of information is available concerning the quality of care of hospitals. However, the information provided differs significantly on each site. Several challenges are remaining which have to be addressed in the future. Those include legal issues, technical issues, and the possibility of manipulation.

Automated lung volumetry from routine thoracic CT scans: how reliable is the result?

RATIONALE AND OBJECTIVES Today, lung volumes can be easily calculated from chest computed tomography (CT) scans. Modern postprocessing workstations allow automated volume measurement of data sets acquired. However, there are challenges in the use of lung volume as an indicator of pulmonary disease when it is obtained from routine CT. Intra-individual variation and methodologic aspects have to be considered. Our goal was to assess the reliability of volumetric measurements in routine CT lung scans. MATERIALS AND METHODS Forty adult cancer patients whose lungs were unaffected by the disease underwent routine chest CT scans in 3-month intervals, resulting in a total number of 302 chest CT scans. Lung volume was calculated by automatic volumetry software. On average of 7.2 CT scans were successfully evaluable per patient (range 2-15). Intra-individual changes were assessed. RESULTS In the set of patients investigated, lung volume was approximately normally distributed, with a mean of 5283 cm(3) (standard deviation = 947 cm(3), skewness = -0.34, and curtosis = 0.16). Between different scans in one and the same patient the median intra-individual standard deviation in lung volume was 853 cm(3) (16% of the mean lung volume). CONCLUSIONS Automatic lung segmentation of routine chest CT scans allows a technically stable estimation of lung volume. However, substantial intra-individual variations have to be considered. A median intra-individual deviation of 16% in lung volume between different routine scans was found.

Comparison of bipolar radiofrequency ablation zones in an in vivo porcine model: Correlation of histology and gross pathological findings

BACKGROUND Continuing research ex vivo and in vivo with animal models is performed to advance the oncological safety of radiofrequency ablation (RFA) of liver tumors. In these experiments, frequently imaging modalities (e.g. MRI or CT) or macro-morphological measurements are used to determine the full extent of the different ablation zones inside of RFA lesions. However, no systematic study has been performed so far, which verified the accuracy of the macro-morphological findings. Therefore, the present study aimed to correlate histological and gross pathological findings of bipolar radiofrequency ablation zones of porcine livers with regard to cell viability in vivo. METHODS Bipolar RFA was performed in the liver of anaesthetized female domestic pigs under CT-guidance using an internally cooled 20 mm RFA applicator. Afterwards RFA cross sections of the liver were made in a perpendicular orientation to the applicator. Ablation zones were initially documented by photography and thereafter prepared for histological analysis. Latter was based on HE-staining and NADH-diaphorase cell viability staining. Micro- and macro-morphological sections were digitally analyzed along the cross-section area for statistical correlation. RESULTS Three different RF ablation zones could be differentiated. A central zone showing no cell viability (white zone) was surrounded by a red zone. The red zone could be divided into an inner zone of viable and non-viable cells (red zone 1), followed by a zone of edema with mostly viable cells (red zone 2).Micro- and macro-morphological data showed a strong correlation for the white zone (r = 0.95, p < 0.01), the red zone 1 (r = 0.85, p < 0.01), and the red zone 2 (r = 0.89, p < 0.01). CONCLUSION White zone and red zone could clearly be distinguished in gross pathology and histology after bipolar RFA of porcine liver tissue in vivo. The red zone could be differentiated into an inner zone of viable and non-viable cells and an outer zone with high cell viability and intercellular edema. A strong correlation of micro- and macro-morphology could be shown for all three ablation zones. With this knowledge, gross pathological examination can be used as a reliable indicator of lethally damaged tissue in bipolar RFA of in vivo porcine liver.

Measuring and optimizing results in multipolar RFA: Techniques and early findings in an experimental setting

Radiofrequency ablation (RFA) has shown to be a reasonable alternative for the treatment of hepatic tumors and metastases although multiple limitations remain. Cooling effects due to larger vessels can prevent complete coverage and may lead to early tumor relapse. This preliminary in vivo pig study combines the use of multipolar RFA with three applicators (six electrodes) and interrupted liver perfusion using Pringles maneuver to overcome the most serious limitations. Furthermore, immediate detection of incomplete RFA is important to revise ablation. We used contrast enhanced computed tomography (CECT) to evaluate post ablation results in comparison to macroscopic images in healthy pig liver. We found significantly (p = 0.001) larger ablation zones and no affection by larger vessels with interrupted liver perfusion. This allows effective RFA for larger tumors. Immediate postinterventional CECT provided comparable results (r = 0.985) to macroscopic evaluation.

The effect of prone versus supine positioning of Goettingen minipigs on lung density as viewed by computed tomography

Minipigs are frequently used for scientific research as they are easy to handle and the dimensions of their vascular system do not change after 20 months of age. Although surgical interventions under anaesthesia are often performed in the supine position the effects of this positioning on lung functionality in minipigs have not been systematically described. This study aimed to analyse the influence of supine positioning on the macrostructure of the lung and the pulmonary density by the use of computed tomography imaging in pre-adult Göttingen minipigs. Twelve pre-adult female minipigs were used in the study and lung density was investigated in both the prone and the supine positions. The time between the scans in prone and supine positions was less than 5 minutes (296 ± 6 sec). In the prone position lung density did not differ between the dorsal and ventral part of the lung (-641 ± 72 Hounsfield units [HU]). However in the supine position there was a ventrodorsal gradient of decreasing density (ventral part of the lung: -497 ± 106 HU, dorsal part of the lung: -723 ± 51 HU). The changes in lung density were not accompanied by changes in lung volume (829 ± 191 ml). These results suggest an influence of the body position on the ventilation/perfusion (V(A)/Q) matching of the lung which could possibly result in lowered lung oxygenation as well as in an increased heart activity in the supine position. Additionally, due to the steep course of the vena cava caudalis from the caval foramen in the diaphragm across to the heart (in contrast to the more shallow course in the prone position) the activity of the heart necessary to pump the venous blood to the right atrium has to be higher in the supine position than in the prone position. In pigs the capacity of the heart to increase frequency is limited due to a diastolic/systolic (D/S) ratio <1. Supine positioning may possibly increase their risk of cardiovascular complications.