The role of hydrogen bond defects for cluster formation and distribution in ionic liquids by means of neutron diffraction and molecular dynamics simulations

Defects fundamentally govern the properties of all real materials. Correlating molecular defects to macroscopic quantities remains a challenge, particularly in the liquid phase. Herein, we report the influence of hydrogen bonds (HB) acting as defects in mixtures of non-hydroxyl-functionalized ionic liquids (ILs) with an increasing concentration of hydroxyl-functionalized ILs. We observed two types of HB defects: The conventional HBs between cation and anion (c-a), and the elusive HBs between cations (c-c) despite the repulsive Coulomb forces. We use neutron diffraction with isotopic substitution in combination with molecular dynamics simulations for measuring the geometry, strength, and distribution of mobile OH defects in the IL mixtures. In principle, this procedure allows relating the number and stability of defects to macroscopic properties such as diffusion, viscosity, and conductivity, which are of utmost importance for the performance of electrolytes in batteries and other electrical devices.

Three in One: The Versatility of Hydrogen Bonding Interaction in Halide Salts with Hydroxy-Functionalized Pyridinium Cations

The paradigm of supramolecular chemistry relies on the delicate balance of noncovalent forces. Here we present a systematic approach for controlling the structural versatility of halide salts by the nature of hydrogen bonding interactions. We synthesized halide salts with hydroxy-functionalized pyridinium cations [HOCn Py]+ (n=2, 3, 4) and chloride, bromide and iodide anions, which are typically used as precursor material for synthesizing ionic liquids by anion metathesis reaction. The X-ray structures of these omnium halides show two types of hydrogen bonding: 'intra-ionic' H-bonds, wherein the anion interacts with the hydroxy group and the positively charged ring at the same cation, and 'inter-ionic' H-bonds, wherein the anion also interacts with the hydroxy group and the ring system but of different cations. We show that hydrogen bonding is controllable by the length of the hydroxyalkyl chain and the interaction strength of the anion. Some molten halide salts exhibit a third type of hydrogen bonding. IR spectra reveal elusive H-bonds between the OH groups of cations, showing interaction between ions of like charge. They are formed despite the repulsive interaction between the like-charged ions and compete with the favored cation-anion H-bonds. All types of H-bonding are analyzed by quantum chemical methods and the natural bond orbital approach, emphasizing the importance of charge transfer in these interactions. For simple omnium salts, we evidenced three distinct types of hydrogen bonds: Three in one!

Quantification of residual pneumoperitoneum after robotic-assisted laparoscopic surgery

Objective

Laparoscopic surgery improves the postoperative recovery process and relies on CO2 insufflation to establish the operative field. Most residual CO2 is expelled prior to port and incision closure. Computed tomography (CT) is often used to assess an acute abdomen and is highly sensitive in detecting free intra-abdominal air – the hallmark sign of a bowel injury. Yet, the clinical significance of free air in the early postoperative period is confounded by residual CO2 and is not usually due to a visceral injury. The aim of this prospective study was to systematically quantify the residual pneumoperitoneum (RPP) at varying timepoints after robotic-assisted laparoscopic surgery.

Methods

Patients undergoing robot-assisted laparoscopic intervention, both radical prostatectomies and left hemicolectomies, were prospectively enrolled in the study. At the conclusion of each operation, manual abdominal pressure was applied to aid in exsufflation of residual CO2. Very-low-dose CT scans were performed on postoperative days (POD) 3, 5, and 7, with subsequent volumetric quantification of RPP. To investigate potential factors influencing the quantity of RPP, correlation plots were made against BMI, age, operative time, total insufflation volume, intra-abdominal pressure, time to flatus and first bowel movement, pain score, and postoperative analgesic requirement.

Results

Thirty-one patients undergoing robotic assisted laparoscopic prostatectomy were untill now enrolled in the study, of which only one experienced a Clavien-Dindo 2 complication; all others were free of any complications during post-operative assessment period. On POD3, 5, and 7, 97%, 94%, and 68% of patients, respectively, demonstrated RPP. The RPP volumes were noted to be 9.6 mL (IQR = 3.9-31.8; maximum = 247 mL) on POD3, 1.0 mL (0.1-5.1; maximum = 221 mL) on POD5, and 0.08 mL (1-1.2; maximum = 112 mL) on POD7. A significant correlation was only appreciated between RPP volume and BMI; those with higher BMIs had lower initial volumes of RPP on POD3 and exhibited a more rapid decrease in RPP over one week.

Conclusion

One week after robot-assisted laparoscopic operations, a majority of patients will exhibit clinically insignificant RPP, even with volumes as high as 250 mL. Larger patients tend to have smaller residuals of CO2. Our data provide new basic knowledge regarding RPP and may help to interpret postoperative CT-scans.

Freezing the Motion in Hydroxy-Functionalized Ionic Liquids-Temperature Dependent NMR Deuteron Quadrupole Coupling Constants for Two Types of Hydrogen Bonds Far below the Glass Transition

We measured the deuteron quadrupole coupling constants (DQCCs) for hydroxy-functionalized ionic liquids (ILs) with varying alkyl chain length over the temperature range between 60 and 200 K by means of solid-state NMR spectroscopy. For all temperatures, the ²H spectra show two DQCCs representing different types of hydrogen bonds. Higher values, ranging from 220 to 250 kHz, indicate weaker hydrogen bonds between cation and anion (c-a), and lower values varying from 165 to 210 kHz result from stronger hydrogen bonds between the OD groups of cations (c-c), in agreement with recent observations in infrared, neutron diffraction, and NMR studies. We observed different temperature dependencies for (c-a) and (c-c) hydrogen bonding. From the static pattern of the ²H spectra at the lowest temperatures, we derived the true DQCCs being up to 20 kHz larger than recently reported values measured at the glass transition temperature. We were able to freeze the librational motions of the hydrogen bonds in the ILs. The temperature dependence of the (c-a) and (c-c) cluster populations in the glassy state is opposite to that observed in the liquid state, partly anticipating the behavior of ILs tending to crystallize.

Effect of Hydrogen Bonding between Ions of Like Charge on the Boundary Layer Friction of Hydroxy-Functionalized Ionic Liquids

Atomic force microscopy has been used to measure the lubricity of a series of ionic liquids (ILs) at mica surfaces in the boundary friction regime. A previously unreported cation bilayer structure is detected at the IL-mica interface due to the formation of H-bonds between the hydroxy-functionalized cations [(c-c) H-bonds], which enhances the ordering of the ions in the boundary layer and improves the lubrication. The strength of the cation bilayer structure is controlled by altering the strength of (c-c) H-bonding via changes in the hydroxyalkyl chain length, the cation charge polarizability, and the coordination strength of the anions. This reveals a new means of controlling IL boundary nanostructure via H-bonding between ions of the same charge, which can impact diverse applications, including surface catalysis, particle stability, electrochemistry, etc.

Chain Length Dependence of Hydrogen Bond Linkages between Cationic Constituents in Hydroxy-Functionalized Ionic Liquids: Tracking Bulk Behavior to the Molecular Level with Cold Cluster Ion Spectroscopy

Hydroxy functionalization of cations in ionic liquids (ILs) can lead to formation of contacts between their OH groups [so-called (c-c) interactions]. One class of these linkages involves cooperatively enhanced hydrogen bonds to anionic partners that are sufficiently strong to overcome the repulsion between two positively charged centers. Herein, we clarify how the propensity for the formation of (c-c) contacts depends on the alkyl chain length between two cationic rings and their OH groups by analyzing the temperature-dependent IR spectra of bulk ILs as well as the vibrational predissociation spectra of ∼35 K complexes comprised of two cations and one anion. This study compares the behavior of two cationic derivatives with ethyl and propyl chains complexed with two different anions: bis(trifluoromethylsulfonyl)imide and tetrafluoroborate. Only the bulk ILs with the longer chain propyl derivative [HPMPip⁺ = 1-(3-hydroxypropyl)-1-methylpiperidinium] display (c-c) interactions. Molecular-level aspects of this docking arrangement are revealed by analyzing the OH stretching fundamentals displayed by the ternary complexes.

Controlling "like-likes-like" charge attraction in hydroxy-functionalized ionic liquids by polarizability of the cations, interaction strength of the anions and varying alkyl chain length

We provide comprehensive understanding of "like-likes-like" charge attraction in hydroxy-functionalized ionic liquids (ILs) by means of infrared spectroscopy (IR), quantum chemistry and differential scanning calorimetry (DSC). We show that hydrogen bonding between cation and cation (c-c) is possible despite the repulsive forces between ions of like charge. Already at room temperature, the (c-c) hydrogen bonds can compete with the regular Coulomb-enhanced hydrogen bonds between cation and anion (c-a). For a large set of well-selected ILs, we show that "like-charge attraction" between the OH-functionalized cations is controllable by the polarizability of the cation, the interaction strength of the anion and the length of the hydroxyalkyl chain. In particular, we clarify whether tethering the OH group away from the positive charge center of the cationic ring with longer hydroxyalkyl chains compensates for unfavourable cation/anion combinations with respect to (c-c) cluster formation. For that purpose, we synthesized and characterized twelve ionic liquids including the differently polarizable cations, 1-(n-hydroxyalkyl)-1-methylpiperidinium [HOC_nMPip]⁺ and 1-(n-hydroxyalkyl)-pyridinium [HOC_nPy]⁺, as well as the weakly and strongly interacting anions, bis(trifluoromethanesulfonyl)imide [NTf₂]^- and methanesulfonate [OMs]^-, respectively. On top, we varied the hydroxyalkyl chain length (HOC_n) (n = 2-5). We systematically show how these three molecular ion parameters affect like-charge attraction. The use of polarizable cations, weakly interacting anions, and long alkyl chain tethers results in (c-c) clustering already at room temperature. Kinetic trapping is not a prerequisite for the existence of (c-c) cluster species in ILs. Moreover, we demonstrate that micro structuring affects macroscopic behavior of this type of ILs. We observed that substantial (c-c) interaction prevents ILs from crystallizing. Instead, these ILs supercool and finally form a glass.

Counting cations involved in cationic clusters of hydroxy-functionalized ionic liquids by means of infrared and solid-state NMR spectroscopy

Sensitive probe of like-charge attraction: analyzing infrared spectra allows counting the number of cations involved in clusters of opposite (c–a) and like-charged (c–c) ions in ionic liquids. This approach is also applicable to molecular liquids.

Influence of Hydrogen Bonding between Ions of Like Charge on the Ionic Liquid Interfacial Structure at a Mica Surface

Ionic liquids (ILs) have attracted increasing interest in science and technology because of their remarkable properties, which can be tuned via varying ion structures to control the relative strengths of Coulomb interactions, hydrogen bonding (H-bonding), and dispersion forces. Here we use atomic force microscopy to probe the interfacial nanostructures of hydroxy functionalized ILs at negatively charged mica surfaces. H-bonding between hydroxy functionalized cations (c-c) produces cation clusters and a stronger interfacial nanostructure. H-bond stabilized cation clusters form despite opposing electrostatic repulsions between charge groups, cation-anion (c-a) electrostatic attractions, and (c-a) H-bonds. Comparison of ILs with and without OH functionalized cations shows directional H-bonding enhances interfacial structure more strongly than the dispersion forces between alkyl groups. These findings reveal a new means of controlling IL interfacial nanostructure via H-bonding between like-charged ions, which impact diverse areas including electrochemical charge storage (batteries and catalysis), electrodeposition, lubrication, etc.

Hydrogen Bonding Between Ions of Like Charge in Ionic Liquids Characterized by NMR Deuteron Quadrupole Coupling Constants-Comparison with Salt Bridges and Molecular Systems

We present deuteron quadrupole coupling constants (DQCC) for hydroxyl‐functionalized ionic liquids (ILs) in the crystalline or glassy states characterizing two types of hydrogen bonding: The regular Coulomb‐enhanced hydrogen bonds between cation and anion (c–a), and the unusual hydrogen bonds between cation and cation (c–c), which are present despite repulsive Coulomb forces. We measure these sensitive probes of hydrogen bonding by means of solid‐state NMR spectroscopy. The DQCCs of (c–a) ion pairs and (c–c) H‐bonds are compared to those of salt bridges in supramolecular complexes and those present in molecular liquids. At low temperatures, the (c–c) species successfully compete with the (c–a) ion pairs and dominate the cluster populations. Equilibrium constants obtained from molecular‐dynamics (MD) simulations show van't Hoff behavior with small transition enthalpies between the differently H‐bonded species. We show that cationic‐cluster formation prevents these ILs from crystallizing. With cooling, the (c–c) hydrogen bonds persist, resulting in supercooling and glass formation.

The Double-Faced Nature of Hydrogen Bonding in Hydroxy-Functionalized Ionic Liquids Shown by Neutron Diffraction and Molecular Dynamics Simulations

We characterize the double-faced nature of hydrogen bonding in hydroxy-functionalized ionic liquids by means of neutron diffraction with isotopic substitution (NDIS), molecular dynamics (MD) simulations, and quantum chemical calculations. NDIS data are fit using the empirical potential structure refinement technique (EPSR) to elucidate the nearest neighbor H⋅⋅⋅O and O⋅⋅⋅O pair distribution functions for hydrogen bonds between ions of opposite charge and the same charge. Despite the presence of repulsive Coulomb forces, the cation-cation interaction is stronger than the cation-anion interaction. We compare the hydrogen-bond geometries of both "doubly charged hydrogen bonds" with those reported for molecular liquids, such as water and alcohols. In combination, the NDIS measurements and MD simulations reveal the subtle balance between the two types of hydrogen bonds: The small transition enthalpy suggests that the elusive like-charge attraction is almost competitive with conventional ion-pair formation.

Isolating the role of hydrogen bonding in hydroxyl-functionalized ionic liquids by means of vaporization enthalpies, infrared spectroscopy and molecular dynamics simulations

Hydrogen bonding in hydroxyl-functionalized ionic liquids (right) prevents favourable dispersion interaction between cation and anion (left). We analyze this subtle balance of interactions by combining calorimetry, IR spectroscopy and MD simulations.

When hydrogen bonding overcomes Coulomb repulsion: from kinetic to thermodynamic stability of cationic dimers

Quantum chemical calculations have been employed to study the kinetic and thermodynamic stability of hydroxy-functionalized 1-(3-hydroxyalkyl)pyridinium cationic dimers. For [Py-(CH2)n-OH+]2 structures with n = 2-17 we have calculated the robust local minima with clear dissociation barriers preventing their "Coulomb explosion" into separated cations. For n = 15 hydrogen bonding and dispersion forces fully compensate for the repulsive Coulomb forces between the cations allowing for the quantification of the pure hydrogen bond in the order of 20 kJ mol-1. The increasing kinetic stability even turns to thermodynamic stability with further elongated hydroxyalkyl chains. Now, quantum-type short-range attraction wins over classical long-range electrostatic repulsion resulting in negative binding energies and providing the first thermodynamically stable cationic dimers. The electronic, structural and spectroscopic signatures of the cationic dimers could be correlated to NBO parameters, supporting the existence of anti-electrostatic hydrogen bonds (AEHB) as recently suggested by Weinhold. In principle, these pure cationic dimers should be detectable in gas-phase experiments at low temperatures without the need of mediating molecules or counteranions.

Cooperatively enhanced hydrogen bonds in ionic liquids: closing the loop with molecular mimics of hydroxy-functionalized cations

The combined experimental and theoretical approach for the gas and the liquid phases provides a quantitative understanding of the competition between differently H-bonded and charged constituents in liquids.

Spectroscopic Evidence for an Attractive Cation-Cation Interaction in Hydroxy-Functionalized Ionic Liquids: A Hydrogen-Bonded Chain-like Trimer

We address the formation of hydrogen bonded domains among the cationic constituents of the ionic liquid (IL) 1-(3-hydroxypropyl)pyridinium tetrafluoroborate [HPPy][BF₄ ] by means of cryogenic ion vibrational predissociation spectroscopy of cold (ca. 35 K) gas-phase cluster ions and quantum chemistry. Specifically, analysis of the OH stretching bands reveals a chain-like OH⋅⋅⋅OH⋅⋅⋅OH⋅⋅⋅BF₄ ^- binding motif involving the three cations in the cationic quinary cluster ion (HPPy⁺ )₃ (BF₄ ^- )₂ . Calculations show that this cooperative H-bond attraction compensates for the repulsive Coulomb forces and results in stable complexes that successfully compete with those in which the OH groups are predominantly attached to the counter anions. Our combined experimental and theoretical approach provides insight into the cooperative effects that lead to the formation of hydrogen bonded domains involving the cationic constituents of ILs.

Cationic clustering influences the phase behaviour of ionic liquids

“Unlike charges attract, but like charges repel”. This conventional wisdom has been recently challenged for ionic liquids. It could be shown that like-charged ions attract each other despite the powerful opposing electrostatic forces. In principle, cooperative hydrogen bonding between ions of like-charge can overcome the repulsive Coulomb interaction while pushing the limits of chemical bonding. The key challenge of this solvation phenomenon is to establish design principles for the efficient formation of clusters of like-charged ions in ionic liquids. This is realised here for a set of well-suited ionic liquids including the same hydrophobic anion but different cations all equipped with hydroxyethyl groups for possible H-bonding. The formation of H-bonded cationic clusters can be controlled by the delocalization of the positive charge on the cations. Strongly localized charge results in cation-anion interaction, delocalized charge leads to the formation of cationic clusters. For the first time we can show, that the cationic clusters influence the properties of ILs. ILs comprising these clusters can be supercooled and form glasses. Crystalline structures are obtained only, if the ILs are dominantly characterized by the attraction between opposite-charged ions resulting in conventional ion pairs. That may open a new path for controlling glass formation and crystallization. The glass temperatures and the phase transitions of the ILs are observed by differential scanning calorimetry (DSC) and infrared (IR) spectroscopy.

Like-likes-Like: Cooperative Hydrogen Bonding Overcomes Coulomb Repulsion in Cationic Clusters with Net Charges up to Q=+6e

Quantum chemical calculations have been employed to study kinetically stable cationic clusters, wherein the monovalent cations are trapped by hydrogen bonding despite strongly repulsive electrostatic forces. We calculated linear and cyclic clusters of the hydroxy-functionalized cation N-(3-hydroxypropyl) pyridinium, commonly used as cation in ionic liquids. The largest kinetically stable cluster was a cyclic hexamer that very much resembles the structural motifs of molecular clusters, as known for water and alcohols. Surprisingly, strong cooperative hydrogen bonds overcome electrostatic repulsion and result in cationic clusters with a high net charge up to Q=+6e. The structural, spectroscopic, and electronic signatures of the cationic and related molecular clusters of 3-phenyl-1-propanol could be correlated to NBO parameters, supporting the existence of "anti-electrostatic" hydrogen bonds (AEHB), as recently suggested by Weinhold. We also showed that dispersion forces enhance the cationic cluster formation and compensate the electrostatic repulsion of one additional positive charge.

Structural Motifs in Cold Ternary Ion Complexes of Hydroxyl-Functionalized Ionic Liquids: Isolating the Role of Cation-Cation Interactions

We address the competition between intermolecular forces underlying the recent observation that ionic liquids (ILs) with a hydroxyl-functionalized cation can form domains with attractive interactions between the nominally repulsive positively charged constituents. Here we show that this behavior is present even in the isolated ternary (HEMIm⁺)₂NTf₂^- complex (HEMIm⁺ = 1-(2-hydroxyethyl)-3-methylimidazolium) cooled to about 35 K in a photodissociation mass spectrometer. Of the three isomers isolated by double resonance techniques, one is identified to exhibit direct contact between the cations. This linkage involves a cooperative H-bond wherein the OH group on one cation binds to the OH group on the other, which then attaches to the basic N atom of the anion. Formation of this motif comes at the expense of the usually dominant interaction of the acidic C₍₂₎H group on the Im ring with molecular anions, as evidenced by isomer-dependent shifts in the C₍₂₎H vibrational fundamentals.

The influence of like-charge attraction on the structure and dynamics of ionic liquids: NMR chemical shifts, quadrupole coupling constants, rotational correlation times and failure of Stokes–Einstein–Debye

The formation of clusters of like-charge influences the structure and dynamics of ionic liquids.

Controlling the kinetic and thermodynamic stability of cationic clusters by the addition of molecules or counterions

We discuss the stability of cationic clusters when adding molecules or counterions, and predict their occurrence in gas phase experiments.

Computed tomography for pulmonary embolism: assessment of a 1-year cohort and estimated cancer risk associated with diagnostic irradiation

BACKGROUND

The principal concern of any radiation exposure in computed tomography (CT) is the induction of stochastic risks of developing a radiation-induced cancer. The results given in this manuscript will allow to (re-)calculate yield of chest CT.

PURPOSE

To demonstrate a method to evaluate the lifetime attributable risk (LAR) of cancer incidence/mortality due to a single diagnostic investigation in a 1-year cohort of consecutive chest CT for suspected pulmonary embolism (PE).

MATERIAL AND METHODS

A 1-year cohort of consecutive chest CT for suspected PE using a standard scan protocol was analyzed retrospectively (691 patients, 352 men, 339 women). Normalized patient-specific estimations of the radiation doses received by individual organs were correlated with age- and sex-specific mean predicted cancer incidence and age- and sex-specific predicted cancer mortality based on the BEIR VII results. Additional correlation was provided for natural occurring risks.

RESULTS

LAR of cancer incidence/mortality following one chest CT was calculated for cancer of the stomach, colon, liver, lung, breast, uterus, ovaries, bladder, thyroid, and for leukemia. LAR remains very low for all age and sex categories, being highest for cancer of the lungs and breasts in 20-year-old women (0.61% and 0.4%, respectively). Summation of all cancer sites analyzed raised the cumulative relative LAR up to 2.76% in 20-year-old women.

CONCLUSION

Using the method presented in this work, LAR of cancer incidence and cancer mortality for a single chest CT for PE seems very low for all age groups and both sexes, but being highest for young patients. Hence the risk for radiation-induced organ cancers must be outweighed with the potential benefit or a treatment and the potential risks of a missed and therefore untreated PE.

[Inicidental finding: patient with cervical spine trauma]

An ossification of the posterior longitudinal ligament, often presenting asymptomatically, can cause a symptomatic myelopathy after trauma. Keeping this entity in mind in daily clinical routine will help in making the correct diagnosis and in administering the corresponding therapy.

Detection of urolithiasis using low-dose CT--a noise simulation study

How does an acquisition at reduced doses using automatic tube current modulation techniques compare to the normal standard dose CT? Does it affect the sensitivity for detection of calcifications? CT raw data of 54 patients with suspected urolithiasis acquired with automatic tube current modulation techniques were used for image noise simulations with 100%, 50% and 25% dose simulated. Data were analyzed by independent readers with regard to the presence of urolithiasis, stone location, size, density and differential diagnoses. The mean effective dose per standard examination/50%/25% simulation was 7.3 mSv/3.8 mSv/1.9 mSv. Sensitivities/specificities for detection of urolithiasis were calculated for all dose simulations and resulted in 0.94/0.98 in the 50% dose level group and 0.82/0.97 in the 25% dose level group. Low-dose CT with tube current modulation can be used as a standard procedure for the evaluation of patients with suspected acute renal colic.

[Confusion, gait ataxia and ophthalmoplegia in a patient with chronic alcohol consumption]

Wernicke encephalopathy is a neurological disorder, often caused by a lack of thiamine. Immediate diagnosis and therapy are important to prevent significant morbidity and mortality. Based on a clinical case radiologic imaging features on MRI are demonstrated.

[Alcoholism and possible consequences for the central nerval system - pontine and extrapontine myelinolysis]

The central pontine and extrapontine myelinolysis is an important entity in the neurology disorders in the context with alcohol abuse. Though often first based on clinical characteristics, the diagnosis can be often supported with radiologic imaging.

Transthoracic sonography for the detection of pulmonary embolism--a meta-analysis

PURPOSE

Radiation protection is a major issue since the implementation of MSCT technology and its widespread indication for the detection of various diseases. In a European-wide trial (SECT) meta-analyses of imaging alternatives to CT have been initiated. This paper focuses on the diagnostic performance of transthoracic ultrasound (TUS) for the diagnosis of pulmonary embolism (PE) (5 studies, 652 patients).

MATERIALS AND METHODS

Medical literature (from 1990 to 2006) in PubMed and EMBASE databases was searched for articles on studies that used TUS as diagnostic tests for PE. Studies were included if they reported the positive and negative rates of PE diagnoses from TUS compared with the rates of PE in CT, MRI or a combination of diagnostic tests. Two readers assessed the quality of the studies.

RESULTS

Pooled sensitivity and specificity of TUS for PE were 80 % (95 % CI: 75 %, 83 %) and 93 % (95 % CI: 89 %, 96 %), respectively.

CONCLUSION

In the time of MSCT, TUS is an imaging modality that is no longer part of recent diagnostic algorithms for the diagnosis of PE. Considering the increasing number of requested CT examinations and therefore increasing collective radiation dose, this meta-analysis shows that TUS is a diagnostic alternative for special clinical settings in the work-up of suspected PE that seems to have fallen into oblivion.

[Surgical strategies in the treatment of acute diverticular disease--a retrospective analysis of surgical patients at the hospital "Städtisches Klinikum Brandenburg an der Havel"]

BACKGROUND

Depending on the degree of severity of acute diverticular disease, operative therapy is performed as an emergency, urgent or elective resection. A challenge is posed not only by the decision on whether to opt for conservative therapy or speedy resection, but also, when resection is indicated, by choosing the most suitable procedure (primary anastomosis or discontinuity resection). The frequency of use of the various therapeutic concepts and their success rates were studied in our clinic.

METHODS

All cases of acute sigmoid diverticulitis (108) surgically treated in the Klinikum Brandenburg from 2003 to 2005 were analysed retrospectively.

RESULTS

17 patients (15.7 %) underwent emergency resection with primary anastomosis (8) (of these, 4 were with additional protective stoma) or Hartmann procedure (9). 17 patients (15.7 %) required urgent laparotomy, 11 needed primary anastomosis (protective stoma in 8 patients) and the Hartmann procedure was performed in 3 patients. In 2 patients the laparotomy was limited to colostomy with drainage without resection because of the high cardiac risk under anaesthesia. Of 49 patients (45.4 %), 25 underwent elective resection via laparotomy, and 24 via laparoscopy, with protective stomas in 4 and 3 patients, respectively. 25 patients (23.1 %) were treated conservatively: in 8 cases a later resection was recommended. Revision was necessary in 10 cases due to anastomosis dehiscence (4), bleeding (1), stoma necrosis (2), ileus (1), wound dehiscence (1) or for programmed lavage after free perforation with faecal peritonitis (2). 3 multimorbid patients died after emergency laparotomy.

CONCLUSION

A concept of staged treatment can reduce the number of emergency laparotomies; it provides for early focus removal in cases which cannot be managed adequately with conservative treatment and aims for the largest possible number of elective resections.

[Kissing osteochondroma of the lower limb]

As definition, a "kissing" osteochondroma is a typical new bony formation with erosion on the adjacent paired bone, provoked by pressure of the outgrowth. Further diagnostics for incidentally diagnosed solitary osteochondroma should be performed only in cases where malignant transformation is suspected.

[Portal vein thrombosis in a young patient with severe abdominal pain: a case report]

Wir berichten über einen Patienten mittleren Alters mit gürtelförmigen Oberbauchschmerzen, bei welchem nebst einer chronischen zusätzlich eine subakute Thrombose der kavernös transformierten und stark verkalkten Portalvene duplexsonographisch und computertomographisch nachgewiesen wurde. Eine Vollliqueminisierung und anschliessende Marcoumarisierung führte zur Besserung der Symptomatik.

[Intercostal tumors: diagnostic pitfalls]

Aussagen in radiologischen Befunden über die Dignität asymptomatischer interkostaler Raumforderungen sind mit Vorsicht zu treffen. Auch radiologisch zunächst benigne erscheinende Läsionen können sich, wie in beiden vorliegenden Fällen, als bösartig entpuppen. Metastasen eines malignen Melanoms können sich atypisch präsentieren und dadurch leicht verkannt werden. Schwannome im Rahmen einer Neurofibromatose Typ 1 können maligne entarten. Generell ist bei einer interkostalen Raumforderung die Differentialdiagnose eines malignen Tumors immer in Betracht zu ziehen, nicht zuletzt um den Weg für eine adäquate Therapie zu ebnen.

Survival trends among Danish patients undergoing coronary angiography for known or suspected ischaemic heart disease: a population based follow up study, 1992-2000

OBJECTIVE

To determine, from population based clinical data, changes in the survival of Danish patients examined by coronary angiography for known or suspected ischaemic heart disease (IHD) during the 1990s.

DESIGN

Follow up study.

SETTING

The departments of cardiology at Rigshospitalet, Copenhagen University Hospital, and Skejby Hospital, Aarhus University Hospital, Denmark.

PATIENTS

Patients with IHD (n = 7021) who underwent first time coronary angiography in 1992, 1996, or 2000.

MAIN OUTCOMES MEASURES

Three year survival was compared between cohorts and with that of the general population. Cox proportional hazards regression was used to estimate mortality ratios adjusted for differences in patient characteristics.

RESULTS

Survival improved substantially--for example, adjusted mortality ratio was 0.69 (95% confidence interval (CI) 0.55 to 0.87) when comparing patients from 2000 with patients from 1992. The absolute standardised survival rates after three years of follow up were 87.1% (95% CI 85.4% to 88.8%), 89.9% (95% CI 88.5% to 91.3%), and 91.2% (95% CI 90.3% to 92.1%) among patients examined in 1992, 1996, and 2000, respectively. The improvement was not explained by the improvement in overall survival in the general population during the study period.

CONCLUSIONS

The survival of Danish patients with known or suspected IHD appears to have improved substantially during the 1990s.

Prognostic impact of different regional referral practices for interventional investigation and coronary treatment after exercise testing: a population-based 5-year follow-up study

OBJECTIVE

To examine the association among different centres' referral practices for coronary angiography (CAG) after exercise testing, with 1- and 5-year outcomes.

DESIGN

Observational population-based cohort study.

SETTING

All 10 hospitals and six private practising consultants in Aarhus and Ringkjoebing counties (900 000 inhabitants), Denmark.

SUBJECTS

All patients who in 1996 had an abnormal bicycle exercise test (n = 736).

MEASUREMENTS

Referral for CAG, coronary intervention, cardiovascular and all-cause mortality, and myocardial infarction (MI).

RESULTS

As an immediate consequence of the exercise test, 60.7% of subjects were referred for CAG. Based on the centres' fraction of patients referred for CAG, three categories of centres were defined: low (<33%), intermediate (33-66%) and high (>66%). A low compared with a high referral fraction was associated with a similar 5-year mortality and MI ratio [all-cause/cardiovascular mortality rate ratio (RR) = 1.33, 95% confidence interval (CI): 0.45-3.92/RR = 0.62, 95% CI: 0.25-1.57; and MI RR = 0.92, 95% CI: 0.45-1.86]. The same was found for an intermediate compared with a high fraction (all-cause/cardiovascular mortality RR = 0.92, 95% CI: 0.49-1.72/RR = 0.74, 95% CI: 0.42-1.33; and MI RR = 1.07, 95% CI: 0.68-1.70). Estimates were about the same after 1 year of follow-up with no major differences among centres in mortality or MI.

CONCLUSIONS

Centres' different referral practices for interventional investigation and treatment were not associated significantly with short-term or long-term mortality or MI among patients with an abnormal exercise test.

Ovarian 'tumor' of the adrenogenital syndrome: the first reported case

We report the case of a 36-year-old woman with congenital adrenal hyperplasia from 21-hydroxylase deficiency who had been receiving replacement therapy with corticosteroids since birth. At the age of 35 years, she developed abrupt aggravation of her virilizing symptoms and underwent an adrenalectomy and partial left oophorectomy. Persistent virilization and high testosterone levels led to right oophorectomy and completion left oophorectomy 6 months later. Each adnexa contained ovarian or paraovarian soft brown masses that on microscopic examination were identical to the testicular tumor of the adrenogenital syndrome. This represents the first reported case of this pathology (well known in the testis) in the ovary.

Epigenetic PTEN silencing in malignant melanomas without PTEN mutation

A tumor suppressor gene at 10q 23.3, designated PTEN, encoding a dual specificity phosphatase with lipid and protein phosphatase activity, has been shown to play an important role in the pathogenesis of a variety of human cancers. Germline mutations in PTEN cause Cowden syndrome (CS), which is characterized by multiple hamartomas and a high risk of breast and thyroid cancers. Frequent loss of heterozygosity at 10q is found in both early and advanced-stage sporadic melanomas; however, mutations or deletions in PTEN are detected mainly in melanoma cell lines. In this study, we examined PTEN expression in 34 unselected sporadic melanomas (4 primary melanomas, 30 metastases) using immunohistochemistry and correlated this with the results of structural studies of this gene. Immunostaining of 34 melanoma samples revealed no PTEN expression in 5 (15%) and low PTEN expression in 17 (50%), whereas the rest of the tumors (35%) had high levels of expression. Hemizygous deletion was found in 32% of the tumors but neither intragenic PTEN mutation nor biallelic deletion was found in any of the samples. Of the 5 melanomas showing no PTEN expression, 4 had no mutation or deletion of PTEN. Of the 13 tumors having weak PTEN immunoreactivity and informative loss of heterozygosity results, 6 had evidence of hemizygous allelic loss of PTEN while the remaining 7 had intact PTEN. These results strongly support PTEN as a major tumor suppressor on 10q involved in melanoma tumorigenesis and suggest an epigenetic mechanism of biallelic functional inactivation not previously observed in other cancers where PTEN might be involved.