[A man with dyspnoea after a kidney transplant]. / Een man met kortademigheid na niertransplantatie.

We present a 62-year-old man with a kidney transplant in the past. Because of progressive dyspnoea a CT-scan was made, which showed ground glass in the upper fields with calcifications. He was diagnosed with metastatic pulmonary calcification, which is mostly seen in patient with renal failure and secondary hyperparathyroidism.

Wall shear stress at the initiation site of cerebral aneurysms.

Hemodynamics are believed to play an important role in the initiation of cerebral aneurysms. In particular, studies have focused on wall shear stress (WSS), which is a key regulator of vascular biology and pathology. In line with the observation that aneurysms predominantly occur at regions of high WSS, such as bifurcation apices or outer walls of vascular bends, correlations have been found between the aneurysm initiation site and high WSS. The aim of our study was to analyze the WSS field at an aneurysm initiation site that was neither a bifurcation apex nor the outer wall of a vascular bend. Ten cases with aneurysms on the A1 segment of the anterior cerebral artery were analyzed and compared with ten controls. Aneurysms were virtually removed from the vascular models of the cases to mimic the pre-aneurysm geometry. Computational fluid dynamics (CFD) simulations were created to assess the magnitude, gradient, multidirectionality, and pulsatility of the WSS. To aid the inter-subject comparison of hemodynamic variables, we mapped the branch surfaces onto a two-dimensional parametric space. This approach made it possible to view the whole branch at once for qualitative evaluation. It also allowed us to empirically define a patch for quantitative analysis, which was consistent among subjects and encapsulated the aneurysm initiation sites in our dataset. To test the sensitivity of our results, CFD simulations were repeated with a second independent observer virtually removing the aneurysms and with a 20 % higher flow rate at the inlet. We found that branches harboring aneurysms were characterized by high WSS and high WSS gradients. Among all assessed variables, the aneurysm initiation site most consistently coincided with peaks of temporal variation in the WSS magnitude.

Does Arterial Flow Rate Affect the Assessment of Flow-Diverter Stent Performance?

BACKGROUND AND PURPOSE: Our aim was to assess the performance of flow-diverter stents. The pre- and end-of-treatment angiographies are commonly compared. However, the arterial flow rate may change between acquisitions; therefore, a better understanding of its influence on the local intra-aneurysmal hemodynamics before and after flow-diverter stent use is required. MATERIALS AND METHODS: Twenty-five image-based aneurysm models extracted from 3D rotational angiograms were conditioned for computational fluid dynamics simulations. Pulsatile simulations were performed at different arterial flow rates, covering a wide possible range of physiologic flows among 1-5 mL/s. The effect of flow-diverter stents on intra-aneurysmal hemodynamics was numerically simulated with a porous medium model. Spatiotemporal-averaged intra-aneurysmal flow velocity and flow rate were calculated for each case to quantify the hemodynamics after treatment. The short-term flow-diverter stent performance was characterized by the relative velocity reduction inside the aneurysm. RESULTS: Spatiotemporal-averaged intra-aneurysmal flow velocity before and after flow-diverter stent use is linearly proportional to the mean arterial flow rate (minimum R2 > 0.983 of the linear regression models for untreated and stented models). Relative velocity reduction asymptotically decreases with increasing mean arterial flow rate. When the most probable range of arterial flow rate was considered (3-5 mL/s), instead of the wide possible flow range, the mean SD of relative velocity reduction was reduced from 3.6% to 0.48%. CONCLUSIONS: Both intra-aneurysmal aneurysm velocity and flow-diverter stent performance depend on the arterial flow rate. The performance could be considered independent of the arterial flow rates within the most probable range of physiologic flows.

Comparative Survival among Older Adults with Advanced Kidney Disease Managed Conservatively Versus with Dialysis.

BACKGROUND AND OBJECTIVES: Outcomes of older patients with ESRD undergoing RRT or conservative management (CM) are uncertain. Adequate survival data, specifically of older patients, are needed for proper counseling. We compared survival of older renal patients choosing either CM or RRT. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: A retrospective survival analysis was performed of a single-center cohort in a nonacademic teaching hospital in The Netherlands from 2004 to 2014. Patients with ESRD ages ≥70 years old at the time that they opted for CM or RRT were included. Patients with acute on chronic renal failure needing immediate start of dialysis were excluded. RESULTS: In total, 107 patients chose CM, and 204 chose RRT. Patients choosing CM were older (mean±SD: 83±4.5 versus 76±4.4 years; P<0.001). The Davies comorbidity scores did not differ significantly between both groups. Median survival of those choosing RRT was higher than those choosing CM from time of modality choice (median; 75th to 25th percentiles: 3.1, 1.5-6.9 versus 1.5, 0.7-3.0 years; log-rank test: P<0.001) and all other starting points (P<0.001 in all patients). However, the survival advantage of patients choosing RRT was no longer observed in patients ages ≥80 years old (median; 75th to 25th percentiles: 2.1, 1.5-3.4 versus 1.4, 0.7-3.0 years; log-rank test: P=0.08). The survival advantage was also substantially reduced in patients ages ≥70 years old with Davies comorbidity scores of ≥3, particularly with cardiovascular comorbidity, although the RRT group maintained its survival advantage at the 5% significance level (median; 75th to 25th percentiles: 1.8, 0.7-4.1 versus 1.0, 0.6-1.4 years; log-rank test: P=0.02). CONCLUSIONS: In this single-center observational study, there was no statistically significant survival advantage among patients ages ≥80 years old choosing RRT over CM. Comorbidity was associated with a lower survival advantage. This provides important information for decision making in older patients with ESRD. CM could be a reasonable alternative to RRT in selected patients.

Accuracy and reproducibility of patient-specific hemodynamic models of stented intracranial aneurysms: report on the Virtual Intracranial Stenting Challenge 2011.

Validation studies are prerequisites for computational fluid dynamics (CFD) simulations to be accepted as part of clinical decision-making. This paper reports on the 2011 edition of the Virtual Intracranial Stenting Challenge. The challenge aimed to assess the reproducibility with which research groups can simulate the velocity field in an intracranial aneurysm, both untreated and treated with five different configurations of high-porosity stents. Particle imaging velocimetry (PIV) measurements were obtained to validate the untreated velocity field. Six participants, totaling three CFD solvers, were provided with surface meshes of the vascular geometry and the deployed stent geometries, and flow rate boundary conditions for all inlets and outlets. As output, they were invited to submit an abstract to the 8th International Interdisciplinary Cerebrovascular Symposium 2011 (ICS'11), outlining their methods and giving their interpretation of the performance of each stent configuration. After the challenge, all CFD solutions were collected and analyzed. To quantitatively analyze the data, we calculated the root-mean-square error (RMSE) over uniformly distributed nodes on a plane slicing the main flow jet along its axis and normalized it with the maximum velocity on the slice of the untreated case (NRMSE). Good agreement was found between CFD and PIV with a NRMSE of 7.28%. Excellent agreement was found between CFD solutions, both untreated and treated. The maximum difference between any two groups (along a line perpendicular to the main flow jet) was 4.0 mm/s, i.e. 4.1% of the maximum velocity of the untreated case, and the average NRMSE was 0.47% (range 0.28-1.03%). In conclusion, given geometry and flow rates, research groups can accurately simulate the velocity field inside an intracranial aneurysm-as assessed by comparison with in vitro measurements-and find excellent agreement on the hemodynamic effect of different stent configurations.

Approximating hemodynamics of cerebral aneurysms with steady flow simulations.

Computational fluid dynamics (CFD) simulations can be employed to gain a better understanding of hemodynamics in cerebral aneurysms and improve diagnosis and treatment. However, introduction of CFD techniques into clinical practice would require faster simulation times. The aim of this study was to evaluate the use of computationally inexpensive steady flow simulations to approximate the aneurysm's wall shear stress (WSS) field. Two experiments were conducted. Experiment 1 compared for two cases the time-averaged (TA), peak systole (PS) and end diastole (ED) WSS field between steady and pulsatile flow simulations. The flow rate waveform imposed at the inlet was varied to account for variations in heart rate, pulsatility index, and TA flow rate. Consistently across all flow rate waveforms, steady flow simulations accurately approximated the TA, but not the PS and ED, WSS field. Following up on experiment 1, experiment 2 tested the result for the TA WSS field in a larger population of 20 cases covering a wide range of aneurysm volumes and shapes. Steady flow simulations approximated the space-averaged WSS with a mean error of 4.3%. WSS fields were locally compared by calculating the absolute error per node of the surface mesh. The coefficient of variation of the root-mean-square error over these nodes was on average 7.1%. In conclusion, steady flow simulations can accurately approximate the TA WSS field of an aneurysm. The fast computation time of 6 min per simulation (on 64 processors) could help facilitate the introduction of CFD into clinical practice.

Dutch guideline for the management of electrolyte disorders--2012 revision.

Electrolyte disorders are common and often challenging in terms of differential diagnosis and appropriate treatment. To facilitate this, the first Dutch guideline was developed in 2005, which focused on hypernatraemia, hyponatraemia, hyperkalaemia, and hypokalaemia. This guideline was recently revised. Here, we summarise the key points of the revised guideline, including the major complications of each electrolyte disorder, differential diagnosis and recommended treatment. In addition to summarising the guideline, the aim of this review is also to provide a practical guide for the clinician and to harmonise the management of these disorders based on available evidence and physiological principles.

Intra-aneurysmal pressure and flow changes induced by flow diverters: relation to aneurysm size and shape.

BACKGROUND AND PURPOSE: Effects of blood flow modification by flow diverters are observed to lead often to aneurysm thrombosis and reverse remodeling. For this process, to further understand the potential roles of intra-aneurysmal blood pressure changes and aneurysm morphologies, 23 patients were studied by numeric simulation. MATERIALS AND METHODS: 3D imaging of aneurysms of different sizes and shapes, all located at the supraclinoid segment of the ICA (n=23), was prepared for CFD simulations. Hemodynamic variables were calculated for conditions before and after virtual FD implantation, reconstituting a vessel wall scaffold across the aneurysm neck. WSS, velocity, residence time, turnover time, and intra-aneurysmal pressure were assessed statistically. RESULTS: After placement of FDs, significant reductions inside the aneurysm were observed for most hemodynamic variables (P<.01) except mean intra-aneurysmal pressures. For minimum/maximum intra-aneurysmal pressure values, small but significant changes were found; however, they were considered too small to be of relevance. CONCLUSIONS: Calculations in 23 cases did not reveal significant intra-aneurysmal mean or peak pressure changes, indicating a minor role of pressure changes in the rare event of secondary ruptures after FD use. Other hemodynamic variables (WSS and velocity) exhibited more significant changes, indicating their role in intra-aneurysmal thrombus formation. Size-dependent, significantly higher reduction in WSS (P=.069) and velocity (P=.013) was observed in small aneurysms compared with larger ones. When it came to shape, there were significantly higher reductions in WSS (P=.055) and velocity (P=.065) and a significantly higher increase in turnover time in fusiform aneurysms compared with saccular aneurysms.

Binary ultrasonography for the internist: yes or no, that's the question!

The authors discuss the pros and cons with regard to ultrasound for the internist. They state that ultrasonography is seldom used by internists and they suggest several reasons for this. After a brief review of the literature they conclude that using ultrasound would probably benefit patients and would lead to a more rapid diagnosis and an increase in safety while performing invasive diagnostic and therapeutic interventions. The authors suggest that internists use ultrasound in a different way compared with radiologists, cardiologists, etc. They introduce the term binary ultrasound: ultrasound should be used to answer clinical questions with a yes or a no.

Patient-specific computational hemodynamics of intracranial aneurysms from 3D rotational angiography and CT angiography: an in vivo reproducibility study.

BACKGROUND AND PURPOSE: Patient-specific simulations of the hemodynamics in intracranial aneurysms can be constructed by using image-based vascular models and CFD techniques. This work evaluates the impact of the choice of imaging technique on these simulations. MATERIALS AND METHODS: Ten aneurysms, imaged with 3DRA and CTA, were analyzed to assess the reproducibility of geometric and hemodynamic variables across the 2 modalities. RESULTS: Compared with 3DRA models, we found that CTA models often had larger aneurysm necks (P = .05) and that most of the smallest vessels (between 0.7 and 1.0 mm in diameter) could not be reconstructed successfully with CTA. With respect to the values measured in the 3DRA models, the flow rate differed by 14.1 ± 2.8% (mean ± SE) just proximal to the aneurysm and 33.9 ± 7.6% at the aneurysm neck. The mean WSS on the aneurysm differed by 44.2 ± 6.0%. Even when normalized to the parent vessel WSS, a difference of 31.4 ± 9.9% remained, with the normalized WSS in most cases being larger in the CTA model (P = .04). Despite these substantial differences, excellent agreement (κ ≥ 0.9) was found for qualitative variables that describe the flow field, such as the structure of the flow pattern and the flow complexity. CONCLUSIONS: Although relatively large differences were found for all evaluated quantitative hemodynamic variables, the main flow characteristics were reproduced across imaging modalities.

AngioLab: integrated technology for patient-specific management of intracranial aneurysms.

AngioLab is a software tool developed within the GIMIAS framework and is part of a more ambitious pipeline for the integrated management of cerebral aneurysms. AngioLab currently includes three plug-ins: angio segmentation, angio morphology and stenting, as well as supports advanced rendering techniques for the visualization of virtual angiographies. In December 2009, 23 clinicians completed an evaluation questionnaire about AngioLab. This activity was part of a teaching course held during the 2(nd) European Society for Minimally Invasive Neurovascular Treatment (ESMINT) Teaching Course held at the Universitat Pompeu Fabra, Barcelona, Spain. The Automated Morphological Analysis (angio morphology plug-in) and the Endovascular Treatment Planning (stenting plug-in) were evaluated. In general, the results provided by these tools were considered as relevant and as an emerging need in their clinical field.

Comparison of steady-state and transient blood flow simulations of intracranial aneurysms.

Hemodynamics play an important role in the pathogenesis of intracranial aneurysms and patient-specific computational hemodynamic simulations could provide valuable information to clinicians. Transient simulations that capture the pulsatility of blood flow are commonly used for research purposes. However, steady-state simulations might provide enough information at a lower computational cost, which could help facilitate the introduction of hemodynamic simulations into clinical practice. In this study, we compared steady-state simulations to transient simulations for two aneurysms. The effect of a change in flow rate waveform was investigated and virtual treatment techniques were employed to compare post-treatment flow reduction predictions. We found that the difference in the time-averaged wall shear stress on the aneurysm was less than 5% and the distribution of wall shear stress was qualitatively assessed to be very similar.

Toward integrated management of cerebral aneurysms.

In the last few years, some of the visionary concepts behind the virtual physiological human began to be demonstrated on various clinical domains, showing great promise for improving healthcare management. In the current work, we provide an overview of image- and biomechanics-based techniques that, when put together, provide a patient-specific pipeline for the management of intracranial aneurysms. The derivation and subsequent integration of morphological, morphodynamic, haemodynamic and structural analyses allow us to extract patient-specific models and information from which diagnostic and prognostic descriptors can be obtained. Linking such new indices with relevant clinical events should bring new insights into the processes behind aneurysm genesis, growth and rupture. The development of techniques for modelling endovascular devices such as stents and coils allows the evaluation of alternative treatment scenarios before the intervention takes place and could also contribute to the understanding and improved design of more effective devices. A key element to facilitate the clinical take-up of all these developments is their comprehensive validation. Although a number of previously published results have shown the accuracy and robustness of individual components, further efforts should be directed to demonstrate the diagnostic and prognostic efficacy of these advanced tools through large-scale clinical trials.

Extremely high serum ferritin levels as diagnostic tool in adult-onset Still's disease.

The diagnosis of adult-onset Still's disease (ASD) is difficult to establish due to the nonspecific clinical and laboratory findings. A markedly raised serum ferritin level is a typical finding, although it is not well understood why ferritin levels are extremely high in ASD. We discuss several possible explanations leading to the extremely high levels of ferritin.

Catheter replacement in continuous arteriovenous hemodiafiltration: the balance between infectious and mechanical complications.

OBJECTIVE: To assess the optimal moment of central vascular catheter replacement balancing infectious and mechanical complications in continuous renal replacement therapies in critically ill patients with acute renal failure. METHODS: Prospective sequential trial with historical controls to compare liberal catheter replacement when clinically indicated with routine catheter replacement every 5 days in consecutive patients treated by continuous arteriovenous hemodiafiltration in a level I secondary referral intensive care unit of a university-affiliated teaching hospital. Intention-to-treat analysis. MEASUREMENTS AND MAIN RESULTS: Twenty-two patients underwent catheter replacement when clinically indicated (group II), and 21 patients served as historical controls (group I). The groups were comparable for sex, age, Acute Physiology and Chronic Health Evaluation II scores, comorbidity, and creatinin and urea levels at the start of continuous arteriovenous hemodiafiltration. In group I, 71 catheters were used for 346 treatment days, and in group II, 68 catheters were used for 495 treatment days. The mean duration of catheterization was 4.9 +/- 2.0 days vs. 7.3 +/- 4.5 days, respectively (Student's t-test p <.001). There was no significant difference between the incidence of colonization of catheters (46.8% in group I vs. 39.1% in group II; chi-square p =.35) In group I, bacteremia and catheter sepsis occurred in two patients, whereas this did not occur in group II. The occurrence of mechanical complications was comparable in both groups (15.5% in group I vs. 19.1% in group II). There were significantly more mechanical complications with arterial vs. venous catheters (17 vs. 7; chi-square p =.027). CONCLUSION: When catheters were changed as clinically indicated, they remained significantly longer in situ vs. being replaced routinely every 5 days; infectious and mechanical complications were comparable. The incidence of catheter sepsis was low (2.2%), and no prosthesis infection occurred. Catheter replacement when clinically indicated seems to be as safe as routine replacement every 5 days.

Analysis of narrative ability in children with cochlear implants.

PURPOSE: The purposes of this study were to: 1) develop a scoring system to assess narrative ability in children; 2) evaluate the impact of auditory speech perception with a cochlear implant on narrative ability; and 3) evaluate the importance of narrative ability to reading comprehension in deaf children. DESIGN: Narrative productions prompted from an eight-picture sequence story were elicited from 8 and 9 yr olds; 87 who had at least 4 yr of cochlear implant experience and 28 who had normal hearing. The stories were transcribed and a scoring system for narrative ability was developed based on the use of complete narrative structure, conjunctions linking semantic relations, and referents that served to identify and distinguish characters in the narrative. Narrative ability scores of cochlear implant users were examined in relation to their age, IQ, speech perception, language, and reading test scores. In addition, narrative ability scores for children with normal hearing were compared with two groups of cochlear implant users, those with above average speech perception scores and those with below average speech perception scores. RESULTS: Within the sample of hearing-impaired children, narrative ability scores correlated significantly with speech perception, language syntax, and reading test scores. A multiple regression analysis was conducted to predict reading comprehension scores from four predictor variables (age, IQ, language syntax, and narrative ability). Results reflected the independent contribution of discourse-level language skills, as measured by the narrative ability score, as well as sentence-level language skills in predicting reading test scores. Analysis of stories obtained from 8- and 9-yr-old children with normal hearing revealed the classic pattern that included a high point, a resolution, and one or more evaluative statements. Their stories achieved cohesion from correct use of both conjunctions and referents. Deaf children who received above-average speech perception scores with a cochlear implant (i.e., scored above 48% on the Word Intelligibility by Picture Identification speech perception test) told narratives that were similar in structure and use of referents to those of age mates with normal hearing. Although their use of subordinate conjunctions was not as well developed as normal-hearing children, it was significantly above that of deaf children who received less speech perception benefit after a similar period of implant use. These below-average speech perceivers exhibited significantly poorer use of narrative structure and cohesive devices than either normal-hearing age mates or children who achieved above average speech perception with a cochlear implant. CONCLUSIONS: Narrative ability is an important predictor of reading comprehension ability in deaf children above and beyond IQ and syntactic competence. Children who receive a cochlear implant under 5 yr of age and obtain above average speech perception benefit from the device construct narratives that are similar in structure and cohesion to those of their hearing age mates by age 8 to 9.

Some measures of verbal and spatial working memory in eight- and nine-year-old hearing-impaired children with cochlear implants.

OBJECTIVE: The purpose of this study was to examine working memory for sequences of auditory and visual stimuli in prelingually deafened pediatric cochlear implant users with at least 4 yr of device experience. DESIGN: Two groups of 8- and 9-yr-old children, 45 normal-hearing and 45 hearing-impaired users of cochlear implants, completed a novel working memory task requiring memory for sequences of either visual-spatial cues or visual-spatial cues paired with auditory signals. In each sequence, colored response buttons were illuminated either with or without simultaneous auditory presentation of verbal labels (color-names or digit-names). The child was required to reproduce each sequence by pressing the appropriate buttons on the response box. Sequence length was varied and a measure of memory span corresponding to the longest list length correctly reproduced under each set of presentation conditions was recorded. Additional children completed a modified task that eliminated the visual-spatial light cues but that still required reproduction of auditory color-name sequences using the same response box. Data from 37 pediatric cochlear implant users were collected using this modified task. RESULTS: The cochlear implant group obtained shorter span scores on average than the normal-hearing group, regardless of presentation format. The normal-hearing children also demonstrated a larger "redundancy gain" than children in the cochlear implant group-that is, the normal-hearing group displayed better memory for auditory-plus-lights sequences than for the lights-only sequences. Although the children with cochlear implants did not use the auditory signals as effectively as normal-hearing children when visual-spatial cues were also available, their performance on the modified memory task using only auditory cues showed that some of the children were capable of encoding auditory-only sequences at a level comparable with normal-hearing children. CONCLUSIONS: The finding of smaller redundancy gains from the addition of auditory cues to visual-spatial sequences in the cochlear implant group as compared with the normal-hearing group demonstrates differences in encoding or rehearsal strategies between these two groups of children. Differences in memory span between the two groups even on a visual-spatial memory task suggests that atypical working memory development irrespective of input modality may be present in this clinical population.

The impact of equations on calculation of lean body mass by bioelectrical impedance analysis in RDT patients.

Several equations are available to derive lean body mass (LBM) from bioelectrical impedance analysis (BIA). The purpose of this study was to investigate in dialysis patients the impact of the equation used on the outcome of LBM assessment. To avoid dyshydration as a confounder, vena cava diameter measurement was used to assess normohydration in the 21 patients studied. Five equations were compared. In a previously published study to assess total body water using antipyrine as a gold standard, Deurenberg's formula was advocated to be used in the estimation of LBM by BIA. Therefore, this formula was used as a basis for comparison with the other four equations. One equation gave results comparable to those obtained by Deurenberg's formula. Despite high correlations and agreement according to Bland and Altman analysis, the other three equations showed a significant difference with Deurenberg-derived LBM. Thus, the equation used has a major impact on the outcome of LBM estimations.