Complicated total esophagogastric dissociation: case report

The Authors describe a case of massive haemorragic gastritis in a child who previously underwent total oesophagogastric dissociation without complementary pyloroplasty. The complication was successfully treated by an emergency resection of the fundus. The Authors believe that the complication was probably related to vagal denervation with consequent gastric stagnation and hypergastrinaemia.

Microsurgical spermatico-epigastric venous anastomosis in the treatment of varicocele in children: assessment of long-term patency

AIM

To demonstrate the long-term patency of microsurgical anastomoses between the internal spermatic vein and the inferior epigastric vein, constructed in the treatment of essential varicocele in paediatric patients to supplement ligation of the spermatic veins.

MATERIALS AND METHODS

We submitted 66 patients to inguinopelvic colour-flow Doppler ultrasonography. The patients had been treated 18 - 36 months earlier for essential varicocele by microsurgical inguinal ligation of the testicular venous pedicle and anastomosis between the internal spermatic vein and the inferior epigastric vein.

RESULTS

Preoperatively, the 66 patients operated on at ages ranging from 10 to 16 years (13 +/- 1.4) presented with Dubin and Amelar grade II (14 patients) or grade III (52 patients) left varicocele with ipsilateral testicular hypotrophy. The postoperative follow-up showed 2 cases of persistence of disease and 3 cases of persistence of "medium" spermatic vein reflux without clinical evidence of varicocele. Seven patients developed left hydrocele which resolved spontaneously in 5 cases, whereas in 2 cases it proved necessary to perform an eversion of the tunica vaginalis of the testis. The results obtained in patients treated for Coolsaet type I varicocele (64 patients) were as follows: long-term patency of the anastomosis was observed in 58/64 patients (90.6 %); in 4 patients (6.2 %) the left inferior epigastric vein presented a position in relation to the homologous artery that prevented adequate sampling and thus made it impossible to assess the patency of the anastomosis; in 2 patients (3.1 %) the anastomosis was closed. In the two patients who had submitted to anastomosis for Coolsaet type III varicocele, colour-flow Doppler failed to identify the shunt.

CONCLUSIONS

The results of this study demonstrate that microsurgical anastomosis between the internal spermatic vein, and the inferior epigastric vein remains competent in the long term, thus confirming the validity of this technique for the treatment of essential varicocele in children.

Treatment of neonatal chylous ascites using a modified Denver peritoneovenous shunt: a case report

Chylous ascites is rarely observed in newborns. Its etiology is not always readily identifiable. The authors report a patient with idiopathic chylous ascites resistant both to conservative treatment with total parenteral nutrition plus diuretics and to dietary treatment (milk with a low-fat content and medium-chain triglycerides). Surgical correction of an associated intestinal malrotation and an annular pancreas failed to resolve the ascites and we therefore placed a modified Denver peritoneovenous shunt. Six months after placement of the shunt, the patient was in good general condition, with restoration of normal oral feeding and regular growth in terms of height and weight. Clinical and ultrasonographic follow-up examinations have not revealed the presence of ascitic fluid in the peritoneal cavity.

Chromosome aberrations as biomarkers of radiation exposure: modelling basic mechanisms

The space radiation environment is a mixed field consisting of different particles having different energies, including high charge and energy (HZE) ions. Conventional measurements of absorbed doses may not be sufficient to completely characterise the radiation field and perform reliable estimates of health risks. Biological dosimetry, based on the observation of specific radiation-induced endpoints (typically chromosome aberrations), can be a helpful approach in case of monitored exposure to space radiation or other mixed fields, as well as in case of accidental exposure. Furthermore, various ratios of aberrations (e.g. dicentric chromosomes to centric rings and complex exchanges to simple exchanges) have been suggested as possible fingerprints of radiation quality, although all of them have been subjected to some criticisms. In this context a mechanistic model and a Monte Carlo code for the simulation of chromosome aberration induction were developed. The model, able to provide dose-responses for different aberrations (e.g. dicentrics, rings, fragments, translocations, insertions and other complex exchanges), was further developed to assess the dependence of various ratios of aberrations on radiation quality. The predictions of the model were compared with available data, whose experimental conditions were faithfully reproduced. Particular attention was devoted to the scoring criteria adopted in different laboratories and to possible biases introduced by interphase death and mitotic delay. This latter aspect was investigated by taking into account both metaphase data and data obtained with Premature Chromosome Condensation (PCC).

Estimating mixed field effects: an application supporting the lack of a non-linear component for chromosome aberration induction by neutrons

The action of neutron fields on biological structures was investigated on the basis of chromosome aberration induction in human cells. Available experimental data on aberration induction by neutrons and their interaction products were reviewed. Present criteria adopted in neutron radiation protection were discussed. The linear coefficient alpha and the quadratic coefficient beta describing dose-response curves for dicentric chromosomes induced by neutrons of different energies were calculated via integration of experimental data on dicentric induction by photons and charged particles into the Monte Carlo transport code FLUKA. The predicted values of the linear coefficients for neutron beams of different energies showed good agreement with the corresponding experimental values, whereas the data themselves indicated that the neutron quadratic coefficient cannot be obtained by 'averaging' the beta values of recoil ions and other nuclear reaction products. This supports the hypothesis that neutron induced aberrations increase substantially linearly with dose, a question that has been object of debate for a long time and is still open.

Modelling the influence of shielding on physical and biological organ doses

Distributions of "physical" and "biological" dose in different organs were calculated by coupling the FLUKA MC transport code with a geometrical human phantom inserted into a shielding box of variable shape, thickness and material. While the expression "physical dose" refers to the amount of deposited energy per unit mass (in Gy), "biological dose" was modelled with "Complex Lesions" (CL), clustered DNA strand breaks calculated in a previous work based on "event-by-event" track-structure simulations. The yields of complex lesions per cell and per unit dose were calculated for different radiation types and energies, and integrated into a version of FLUKA modified for this purpose, allowing us to estimate the effects of mixed fields. As an initial test simulation, the phantom was inserted into an aluminium parallelepiped and was isotropically irradiated with 500 MeV protons. Dose distributions were calculated for different values of the shielding thickness. The results were found to be organ-dependent. In most organs, with increasing shielding thickness the contribution of primary protons showed an initial flat region followed by a gradual decrease, whereas secondary particles showed an initial increase followed by a decrease at large thickness values. Secondary particles were found to provide a substantial contribution, especially to the biological dose. In particular, the decrease of their contribution occurred at larger depths than for primary protons. In addition, their contribution to biological dose was generally greater than that of primary protons.

Low-dose radiation action: possible implications of bystander effects and adaptive response

Several experimental studies performed in the last decade have suggested the occurrence of low-dose-specific phenomena such as the bystander effect (BE, damage induction in cells not directly hit by radiation) and adaptive response (AR, induction of resistance to subsequent irradiation with higher doses). Although the underlying mechanisms are still not known in detail, cellular communication is widely regarded as a key factor. BE and AR may have a non-negligible role in modulating low-dose radiation effects not only in cells, but also in tissues and organs. Whether these phenomena would imply an increase or a decrease of low-dose cancer risk is still an open question. In this context a few representative findings are discussed, focusing on their possible implications for low-dose risk.

Nuclear detecting systems at LNL and LNS: foreseen experiments to provide basic data for heavy-ion risk assessment

The use of existing detecting systems developed for nuclear physics studies allows collecting data on particle and ion production cross-sections in reactions induced by Oxygen and Carbon beams, of interest for hadrontherapy and heavy-ion risk assessment. The MULTICS and GARFIELD apparatus, together with the foreseen experiments, are reviewed.

A Monte Carlo code for a direct estimation of radiation risk

An example of pragmatic approach for predicting mixed field effects is presented. The method was initially applied adopting the following, commonly used, assumptions: a) radiation risk (typically cancer) is correlated with chromosome aberration induction; b) radiation-induced chromosome-exchange yield can be well described by a linear-quadratic dependence on particle fluences (mostly linear with high-LET radiation), with parameters depending on particle types and energies. Information on monochromatic field radiobiological effects was integrated in a condensed-history Monte Carlo transport code (FLUKA), able to simulate nuclear interactions. The integrated code provides the chromosome aberration yield (and thus an estimation of radiation risk) in each voxel of any irradiated volume, given any external mixed-field irradiation; in the present work, the method was tested for neutron irradiation of a water phantom. FLUKA was then coupled with a geometrical human phantom provided with different radiation shielding, in order to apply this approach to estimate radiation risk in manned space missions.

Mechanistic bases for modelling space radiation risk and planning radiation protection of astronauts

The approaches generally adopted for planning radiation protection in ground-based facilities cannot be applied straightforward for astronaut protection in space. Indeed in such extreme conditions, modelling methods and shielding design must be based on a detailed mechanistic knowledge of the peculiar astronauts irradiation conditions. Great help can derive from mechanistic modelling, generally aimed to better understand the intermediate steps leading from the initial energy depositions to different biological endpoints, up to organ and organism level. In the present work, criteria will be illustrated for using mechanistic approaches in developing practical tools for astronauts radioprotection, once the external field and the interaction cross sections with the spacecraft walls are known; particular attention will be given to the treatment of mixed fields. Techniques for integrating into condensed-history codes stochastic information provided by event-by-event simulations will be presented.

Cellular communication and bystander effects: a critical review for modelling low-dose radiation action

Available data suggesting the occurrence of "bystander effects" (i.e. damage induction in cells not traversed by radiation) were collected and critically evaluated, in view of the development of low-dose risk models. Although the underlying mechanisms are largely unknown, cellular communication seems to play a key role. In this context, the main features of cellular communication were summarised and a few representative studies on bystander effects were reported and discussed. Three main approaches were identified: (1) conventional irradiation of cell cultures with very low doses of light ions; (2) irradiation of single cells with microbeam probes; (3) treatment with irradiated conditioned medium (ICM), i.e. feeding of unexposed cells with medium taken from irradiated cultures. Indication of different types of bystander damage (e.g. cell killing, gene mutations and modifications in gene expression) has been found in each of the three cases. The interpretations proposed by the investigators were discussed and possible biases introduced by specific experimental conditions were outlined. New arguments and experiments were suggested, with the main purpose of obtaining quantitative information to be included in models of low-dose radiation action. Implications in interpreting low-dose data and modelling low-dose effects at cellular and supra-cellular level, including cancer induction, were analysed. Possible synergism with other low-dose specific phenomena such as adaptive response (AR) (i.e. low-dose induced resistance to subsequent irradiation) was discussed.

Secondary omental torsion in children: report of two cases and review of the literature

Torsion of the greater omentum (TGO) may be due to a congenital abnormal attachment of its free edge. There are no specific symptoms that allow a preoperative differential diagnosis of this condition from common pathologies such as acute appendicitis. Attachment of the omentum to the large bowel and the absence of concomitant diseases make it possible to distinguish TGO secondary to a congenital attachment anomaly from omental infarction, primary TGO, and TGO secondary to an acquired attachment anomaly (attachment to cysts, tumours, hernias, surgical scars, or perforated bowel segments). Resection of the ischaemic portion of the omentum permits complete resolution of the clinical symptoms. The authors report two cases of TGO in children due to abnormal attachment of the greater omentum to the ascending and transverse colon, respectively.

[The role of continent perineal colostomy in surgical emergencies of the distal bowel]

Diverting colostomy is commonly required in surgical emergencies of the distal colon, especially if the patient is in poor condition. This paper shows that the colostomy could be unnecessary in most cases. In the last 10 years, 6 patients (4 with high-risk or postoperative complicated Hirschsprung disease, 1 with intestinal neuronal dysplasia and 1 with iatrogenic rectal stenosis obstruction) have been submitted to primary continent perineal colostomy-modified Duhamel's procedure. The modified technique consists of the exteriorization of the normal colon or ileum by a retrorectal and trans-anal way, while the excision of redundant tissue and rectal spur section are postponed at least for 10 days. In personal experience this peculiar surgical approach allows to avoid not only the complications due to the fashioning of a contraindicated primary anastomosis, but even those due to stomy performance and its closure, promoting good anatomo-functional results in all patients. The advantages of modified Duhamel's operation compared to other procedures (Swenson-Pellerin or Soave pull-through) depend on the rapidity of execution and on the quality of short and long term outcome.

Congenital true pancreatic cyst in pediatric age: case report

Congenital pancreatic cysts are rare lesions in pediatric age. We present a case of congenital true pancreatic cyst in otherwise asymptomatic boy aged 4 years. Clinical history, laboratory, imaging, immunohistological findings and surgical treatment are also described.

Nuclear architecture and radiation induced chromosome aberrations: models and simulations

Knowledge of radiation track structure and its interaction with biological targets is a fundamental starting point in understanding the mechanisms underlying the induction of biological damage. In this context Monte Carlo codes are a powerful tool of investigation, allowing one to simulate both track structure and the features of the target(s) of interest at different scales, from nanometres (linear dimensions of DNA) to micrometres (linear dimensions of human cell nuclei and interphase chromosome territories). In the light of recent experimental findings on nuclear architecture, different approaches in modelling chromosome structure and aberration induction are discussed. In particular, a model is presented in which chromosome territories were explicitly described as subnuclear regions and aberration induction was modelled by coupling the structure of the target with that of the radiation track. Comparisons between model predictions and experimental results from the literature are also reported.

[Cryptohypospadias: Surgical approach and long-term results]

BACKGROUND

Chordee without hypospadias is a rare morphological abnormality of the penis capable of interfering with sexual function. Usually, cases of chordee without hypospadias require surgical correction, and the aim of this study is to assess the efficacy of the techniques normally used in this pathology.

METHODS

The authors analyze the surgical outcomes achieved in 34 patients presenting various degrees of ventral or lateral curvature of the erect penis and operated on in our department over the past 22 years. Twenty-nine subjects attended for follow-up, including 13 who have now reached adulthood.

RESULTS

The milder forms of chordee without hypospadias (Horton and Devine type III and lateral deviations of the penis) all benefited from minor surgery (dermal grafts and Nesbit dorsal plication of the contralateral penile tunica albuginea) and were corrected with a single operation. The most serious forms of chordee without hypospadias where the hypoplasia variously affected the corpus spongiosum, Buck's fascia and the dartos fascia (Horton and Devine types I and II), were submitted to a supplementary extensive urethral mobilization or occasionally a urethroplasty and one-third of them presented persistent residual curvature.

CONCLUSIONS

The authors advocate a more aggressive surgical approach (urethroplasty and/or patches on the ventral tunica albuginea as an alternative to urethral mobilisation) in subjects with more pronounced defects.

Modelling chromosomal aberration induction by ionising radiation: the influence of interphase chromosome architecture

Several advances have been achieved in the knowledge of nuclear architecture and functions during the last decade, thus allowing the identification of interphase chromosome territories and sub-chromosomal domains (e.g. arm and band domains). This is an important step in the study of radiation-induced chromosome aberrations; indeed, the coupling between track-structure simulations and reliable descriptions of the geometrical properties of the target is one of the main tasks in modelling aberration induction by radiation, since it allows one to clarify the role of the initial positioning of two DNA lesions in determining their interaction probability. In the present paper, the main recent findings on nuclear and chromosomal architecture are summarised. A few examples of models based on different descriptions of interphase chromosome organisation (random-walk models, domain models and static models) are presented, focussing on how the approach adopted in modelling the target nuclei and chromosomes can influence the simulation of chromosomal aberration yields. Each model is discussed by taking into account available experimental data on chromosome aberration induction and/or interphase chromatin organisation. Preliminary results from a mechanistic model based on a coupling between radiation track-structure features and explicitly-modelled, non-overlapping chromosome territories are presented.

Surgical treatment of chordee without hypospadias

OBJECTIVE

The aim of this study was to retrospectively assess the efficacy of the surgical techniques commonly used in three types of chordee without hypospadias (Devine and Horton classification).

METHODS

Twenty-six patients, ranging in age from 3 to 14 years, had chordee without hypospadias and underwent Nesbit dorsal plication (9 cases out of 12, type III), associated extensive mobilization of the urethra (10 cases out of 10, type II), and vascularized neourethra (3 cases out of 4, type I).

RESULTS

Eleven subjects undergoing follow-up investigation for the milder forms of chordee were satisfied with the outcome achieved; there was no impediment of any kind in the sex lives of 5 adult subjects. Of the 11 patients undergoing follow-up after more complex surgery for Devine and Horton type I-II chordee without hypospadias, a residual abnormal curvature was present in 4 subjects. These patients were submitted to one or more reoperations with outcomes defined as satisfactory.

CONCLUSION

To avoid the risks of persistent chordee, the authors suggest more radical and accurate operations for the treatment of type I and II pseudohypospadias.

Stochastic aspects and uncertainties in the prechemical and chemical stages of electron tracks in liquid water: a quantitative analysis based on Monte Carlo simulations

A new physical module for the biophysical simulation code PARTRAC has recently been developed, based on newly derived electron inelastic-scattering cross-sections in liquid water. In the present work, two modules of PARTRAC describing the production, diffusion and interaction of chemical species were developed with the specific purpose of quantifying the role of the uncertainties in the parameters controlling the early stages of liquid water radiolysis. A set of values for such parameters was identified, and time-dependent yields and frequency distributions of chemical species produced by electrons of different energies were calculated. The calculated yields were in good agreement with available data and simulations, thus confirming the reliability of the code. As the primary-electron energy decreases down to 1 keV, the *OH decay kinetics were found to get faster, reflecting variations in the spatial distribution of the initial energy depositions. In agreement with analogous works, an opposite trend was found for energies of a few hundred eV, due to the very small number of species involved. The spreading effects shown at long times by *OH frequency distributions following 1 keV irradiation were found to be essentially due to stochastic aspects of the chemical stage, whereas for 1 MeV tracks the physical and pre-chemical stages also were found to play a significant role. Relevant differences in the calculated e(aq) -yields were found by coupling the physics of PARTRAC with descriptions of the pre-chemical and chemical stages adopted in different models. This indicates a strict interrelation of the various stages, and thus a strong dependence of the parameter values on the assumptions made for the preceding and subsequent stages of the process. Although equally acceptable results can be obtained starting from different assumptions, it is necessary to keep control of such uncertainties, since they can significantly influence the modeling of radical attack on DNA and, more generally, radiobiological damage estimation. This study confirms the need for new, independently derived data on specific steps of water radiolysis, to be included in comprehensive biophysical simulation codes.

Radiation pneumonitis after breast cancer irradiation: analysis of the complication probability using the relative seriality model

BACKGROUND

Toxicity of the respiratory system is quite common after radiotherapy of thoracic tumors; breast cancer patients represent one of the groups for which there is also a long expected survival. The quantification of lung tissue response to irradiation is important in designing treatments associated with a minimum of complications and maximum tumor control.

METHODS

The study population consisted of 68 patients who received irradiation for breast cancer at Stage II. Radiation pneumonitis was retrospectively assessed on the basis of clinical symptoms and radiological findings. For each patient, a measure of the exposure (i.e., the lung dose-volume histogram [DVH]) and a measure of the outcome was available. Based on these data, a maximum likelihood fitting to the relative seriality model was performed. The uncertainties of the model parameters were calculated and their impact on the dose-response curve was studied. The optimum parameter set was then applied to 5 other patient groups treated for breast cancer, and the normal tissue complication probability (NTCP) was calculated. Each group was individuated by the radiotherapy treatment technique used; the dose distribution in the lung was described by a mean DVH and the incidence of radiation pneumonitis in each group was known. Lung radiosensitivity was assumed to be homogeneous through all of the calculations.

RESULTS

The relative seriality model could describe the dataset. The volume effect was found to be relevant in the description of radiation pneumonitis. Age was found to be associated with increased risk of radiation pneumonitis. Two distinct dose-response curves were obtained by splitting the group according to age. The impact of the parameter uncertainties on the dose-response curve was quite large. The parameter set determined could be used predictively on 3 of the 5 patient groups.

CONCLUSION

The complication data could be modeled with the relative seriality model. However, further independent datasets, classified according to the same endpoint, must be analyzed before introducing NTCP modeling in clinical practice.

Simulation of DNA fragment distributions after irradiation with photons

The Monte Carlo track structure code PARTRAC has been further improved by implementing electron scattering cross-sections for liquid water and by explicitly modelling the interaction of water radicals with DNA. The model of the genome inside a human cell nucleus in its interphase is based on the atomic coordinates of the DNA double helix with an additional volume for the water shell. The DNA helix is wound around histone complexes, and these nucleosomes are folded into chromatin fibres and further to fibre loops, which are interconnected to build chromosomes with a territorial organisation. Simulations have been performed for the irradiation of human fibroblast cells with carbon K and aluminium K ultrasoft x-rays, 220 kVp x-rays and 60Co gamma-rays. The ratio single-strand breaks to double-strand breaks (ssb/dsb) for both types of ultrasoft x-rays is lower than for gamma-rays by a factor of 2. The contributions of direct and indirect effects to strand break induction are almost independent of photon energy. Strand break patterns from indirect effects reflect differences in the susceptibility of the DNA helix to OH* attack inside the chromatin fibre. Distributions of small DNA fragments (<3 kbp) are determined by the chromatin fibre structure irrespective of whether direct or indirect effects are causing the breaks. In the calculated fragment size distributions for larger DNA fragments (>30 kbp), a substantial deviation from random breakage is found only for carbon K irradiation, and is attributed to its inhomogeneous dose distribution inside the cell nucleus. For the other radiation qualities, the results for larger fragments can be approximated by random breakage distributions calculated for a yield of dsb which is about 10% lower than the average for the whole genome. The excess of DNA fragments detected experimentally in the 8-300 kbp region after x-ray irradiation is not seen in our simulation results.

Modelling radiation-induced biological lesions: from initial energy depositions to chromosome aberrations

The development of biophysical models of chromosome aberration induction has undergone considerable improvements in the past few years. This is mainly due to the development of new experimental techniques, such as fluorescence in situ hybridization (FISH) and premature chromosome condensation (PCC), and to a better knowledge of track structure characteristics (both in the physical and chemical stages). In particular, track structure simulations, providing a detailed description of the spatial distribution of energy depositions and relevant DNA lesions, represent a useful starting point for the development of 'ab initio' models. Various aspects of the processes determining the induction and the formation kinetics of chromosome aberrations are still under debate, concerning in particular the target description (interphase chromosome organization), the characterization of relevant DNA lesions, the possibility of inducing exchanges starting from single radiation-induced lesions, the rejoining mechanisms (proximity effects and possible induction of incomplete exchanges, i.e. one-way exchanges) and the influence of specific scoring criteria adopted both in experiments and models. Starting from Lea's breakage-and-reunion theory and Revell's exchange theory, an overview is given of various models recently reported in the literature. The assumptions adopted by the authors concerning the various processes involved in aberration formation are analysed in detail, in order to clarify the different approaches adopted in treating the open questions outlined above.

Chromosome aberrations induced by light ions: Monte Carlo simulations based on a mechanistic model

PURPOSE

To investigate the mechanisms underlying the induction of chromosome aberrations by ionizing radiation, focusing attention on DNA damage severity, interphase chromosome geometry and the distribution of DNA strand breaks.

METHODS

An ab initio biophysical model of aberration induction in human lymphocytes specific for light ions was developed, based on the assumption that 'complex lesions' (clustered DNA breaks) produce aberrations, whereas less severe breaks are repaired. It was assumed that interphase chromosomes are spatially localized and that chromosome break free-ends rejoin pairwise randomly; the unrejoining of a certain fraction of free-ends was assumed to be possible, and small fragments were neglected in order to reproduce experimental conditions. The yield of different aberrations was calculated and compared with some data obtained using Giemsa or FISH techniques.

RESULTS

Dose-response curves for dicentrics and centric rings (Giemsa) and for reciprocal, complex and incomplete exchanges (FISH) were simulated; the ratio between complex and reciprocal exchanges was also calculated as a function of particle type and LET. The results showed agreement with data from lymphocyte irradiation with light ions.

CONCLUSIONS

The results suggest that clustered DNA breaks are a critical damage type for aberration induction and that interphase chromosome localization plays an important role. Moreover, the effect of a given particle type is related both to the number of induced complex lesions and to their spatial distribution.