Biomechanic and Hemodynamic Perspectives in Abdominal Aortic Aneurysm Rupture Risk Assessment

Abdominal aortic aneurysms (AAAs) pose a significant source of mortality for the elderly, especially if they go on undetected and ultimately rupture. Therefore, elective repair of these lesions is recommended in order to avoid risk of rupture which is associated with high mortality. Currently, the risk of rupture and thus the indication to intervene is evaluated based on the size of the AAA as determined by its maximum diameter. Since AAAs actually present original geometric configurations and unique hemodynamic and biomechanic conditions, it is expected that other variables may affect rupture risk as well. This is the reason why the maximum diameter criterion has often been proven inaccurate. The biomechanical approach considers rupture as a material failure where the stresses exerted on the wall outweigh its strength. Therefore, rupture depends on the pointwise comparison of the stress and strength for every point of the aneurysmal surface. Moreover, AAAs hemodynamics play an essential role in AAAs natural history, progression and rupture. This chapter summarizes advances in AAAs rupture risk estimation beyond the “one size fits all” maximum diameter criterion

Diagnosis of intra-abdominal injuries can be challenging in multitrauma patients with associated injuries. Our experience and review of the literature

ntroduction. Trauma is the most common cause of death and disability among patients during the first four decades of life. Abdominal trauma is reported to be the 3rd most common injured region. Clinical examination may be unreliable in the evaluation of these patients especially in the presence of associated injuries. Therefore the use of diagnostic tools is essential in the management of the injured patient with abdominal trauma and additional injuries. Patients and Methods. During 1 year period from December 2010 to November 2011 we recorded the patients that presented to the emergency department of our hospital and were found to suffer from intra-abdominal injuries. These patients were divided in two groups depending on whether they had additional comorbid injuries or not. Several parameters were recorded and compared between the two groups, such as mechanism of injury, general status and hemodynamic stability of the patient on presentation, physical examination, use of imaging modalities and concomitant findings, need for surgical intervention and mortality rates. Furthermore the discrepancy between physical findings and final diagnosis after the use of diagnostic adjuncts is reported. Results. We recorded 31 patients with abdominal trauma. 13 (42%) patients were found to suffer from abdominal trauma and associated injuries (Group I), whereas 18 (58%) presented with abdominal trauma alone (Group II). The patients of the first group presented hemodynamic instability in 38% of cases while the patients of the second in 22% of cases. Reduced consciousness was present in 38% in group I versus 17% in group II. Signs of abdominal injury during clinical examination were present in only 15% in group I versus 72% in group II that represented a remarkable difference between the two groups. Conservative treatment was possible in 15% of patients with additional injuries and in 22% of patients with abdominal injury alone. In group I there were two deaths whereas in group II all patients survived. Conclusion. In patients with abdominal trauma, associated injuries seem to add to the severity of injury and indicate a worse prognosis. Clinical examination is unreliable and misleading in the majority of these patients and the use of diagnostic tools cannot be overemphasized

Repair of an inguinoscrotal hernia containing the urinary bladder: a case report

<p>Abstract</p> <p>Introduction</p> <p>Cases of patients with inguinoscrotal hernia containing the urinary bladder are very rare. These patients usually present with frequent episodes of urinary tract infection, difficulty in walking, pollakisuria and difficulty in initiating micturition because of incarceration of the urinary bladder into the scrotum.</p> <p>Case presentation</p> <p>We describe the case of an 80-year-old Caucasian man with an incarcerated urinary bladder into the scrotum who underwent surgical repair with mesh.</p> <p>Conclusions</p> <p>Diagnosis of such cases often requires not only clinical examination but also specialized radiological examinations to show the ectopic position of the urinary bladder. Surgical repair in these patients is a real challenge for surgeons.</p

A randomized phase III study of the docetaxel/carboplatin combination versus docetaxel single-agent as second line treatment for patients with advanced/metastatic Non-Small Cell Lung Cancer

<p>Abstract</p> <p>Background</p> <p>To compare the activity and toxicity of docetaxel/carboplatin (DC) doublet vs single agent docetaxel (D) as second-line treatment in patients with advanced non-small cell lung cancer (NSCLC).</p> <p>Methods</p> <p>Patients pre-treated with front-line platinum-free regimens, were randomized to receive either docetaxel/carboplatin (DC), (docetaxel 50 mg/m²; carboplatin AUC4; both drugs administered on days 1 and 15) or docetaxel single-agent (D), (docetaxel 50 mg/m²on days 1 and 15).</p> <p>Results</p> <p>Response rate was similar between the two arms (DC vs D: 10.4% vs 7.7%; p = 0.764). After a median follow-up time of 28.0 months for DC arm and 34.5 months for D arm, progression free survival (PFS) was significantly higher in the DC arm (DC vs D:3.33 months vs 2.60 months; p-value = 0.012), while no significant difference was observed in terms of overall survival (OS) (DC vs D: 10.3 months vs 7.70 months; p-value = 0.550). Chemotherapy was well-tolerated and grade III/IV toxicities were relatively infrequent. No toxic deaths were observed.</p> <p>Conclusions</p> <p>This study has not achieved its primary objective of significant OS prolongation with docetaxel/carboplatin combination over single-agent docetaxel in patients who had not received front-line docetaxel; however, the docetaxel/carboplatin combination was associated with a significant clinical benefit in terms of PFS.</p

The evaluation of geometric and biomechanical factors to develop a patient-specific model to accurately predict risk of rupture of small abdominal aortic aneurysms

The aim of the current analysis is to examine the value of orthogonal in contrast to axial diameter measurements and those of volumetric variables during abdominal aortic aneurysms (AAAs) examination. More importantly to investigate the role of biomechanic and geometric parameters to AAAs rupture risk and hopefully develop a model which could accurately estimate the risk of AAA rupture on an individualized, patient specific level, beyond the “one-size fits all” maximum diameter criterion.Although the mean difference between maximum diameter measurements on an axial or orthogonal plane is low, there is a wide range among cases, mainly observed in asymmetrical AAAs. We introduce “ShapeIndex” which is defined as the quotient of minor/major axis at the cross section presenting the maximum diameter. This may identify those cases which are more likely to be misestimated. CT measurements performed to establish AAA growth rates should consistently use either the axial or orthogonal technique to avoid possible inaccuracies.Growth rate of aneurysms regarding 3Dimensional indices of AAA and ILT volumes is significantly associated with the need for surgical intervention while the same does not hold for growth rates determined by 2Dimensional indices of maximum diameter and ILT thickness. Aneurysm volume is more sensitive in detecting aneurysm expansion than the traditional maximum diameter criterion.Analyzing a rare case presenting extremely rapid growth we postulate that aneurysm surface area under high stress and redistribution of stress against the posterior wall due to changes in geometric configuration and thrombus deposition over time may indicate a high risk profile.With the use of ECG-gated CT scan we found that throughout the cardiac cycle, aneurysmal wall deforms significantly less than non-aneurysmal wall and aneurysmal lumen, due to altered elastic properties and reduced loading. In large AAAs with larger amounts of ILT, the lumen deformation is comparable or even exceeds that of NAA and subsequently so does the distensibility of the Wall-ILT composite, an observation suggesting a thrombus cushioning effect.Regarding pattern of thrombus deposition inside the aneurysm sac our results indicate that posterior thrombus deposition is associated with significantly lower growth rate and lower posterior maximum wall stress compared to that of aneurysms with anterior thrombus deposition and could potentially indicate a lower rupture risk.Through a multi-factorial approach to aneurysms rupture risk, susceptibility to rapid enlargement and therefore a higher rupture risk can be predicted using a statistical model that takes into account thrombus eccentric deposition and relative volume along with neck-AAA angulation with an accuracy of 85%.Σκοπός της παρούσας μελέτης είναι να εξετάσει τις διαφοροποιήσεις μεταξύ αξονικών και ορθογωνικών μετρήσεων στον προσδιορισμό της μέγιστης διαμέτρου των ανευρυσμάτων της κοιλιακής αορτής (ΑΚΑ) και τη σημασία των ογκομετρικών παραμέτρων στην καταγραφή της μεταβολής των διαστάσεων στο χρόνο. Επιπλέον να διερευνήσει τον ρόλο γεωμετρικών και εμβιομηχανικών παραμέτρων στον κίνδυνο ρήξης και ενδεχόμενα να αναπτύξει ένα μοντέλο που θα εκτιμάει με ακρίβεια τον κίνδυνο ρήξης ή ταχείας αύξησης εξατομικευμένα πέρα από το καθολικό κριτήριο της μέγιστης διαμέτρου.Όσον αφορά τον προσδιορισμό της μέγιστης διαμέτρου βλέπουμε ότι η αξονικές μετρήσεις υπερεκτιμούν τη διάμετρο και μπορεί να οδηγήσουν σε θεραπευτικές αστοχίες σε περίπου 1/5 ασθενείς. Η ασυμμετρία του ανευρύσματος όπως αυτή προσδιορίζεται από τον ShapeIndex που εισάγουμε και ο οποίος ορίζεται ως το πηλίκο ελάσσονος/μείζονος άξονα της τομής με την μέγιστη διάμετρο, μπορεί να προβλέψει τις περιπτώσεις εκείνες στις οποίες σημαντικές διαφορές θα πρέπει να αναμένονται.Σχετικά με τις ογκομετρικές παραμέτρους, τα ΑΚΑ που ήταν στην ομάδα ταχείας ογκομετρικής αύξησης παρουσίαζαν 10-πλάσιο κίνδυνο να απαιτήσουν χειρουργική αντιμετώπιση σε σχέση με αυτά στην ομάδα βραδείας αύξησης. Ο αντίστοιχος κίνδυνος μεταξύ ταχέως και βραδέως αυξανόμενων ΑΚΑ με βάση την μέγιστη διάμετρο ήταν μόλις 3. Τέλος ο όγκος ήταν περισσότερο ευαίσθητος στην ανίχνευση της αύξησης του μεγέθους στο χρόνο αφού σε 18% των περιπτώσεων όπου παρατηρήθηκε σημαντική ογκομετρική αύξηση, η διάμετρος του ανευρύσματος ήταν σταθερή.Μελετώντας μια περίπτωση ανευρύσματος με εξαιρετικά ταχεία αύξηση καταγράψαμε μια σημαντική ανακατανομή των τάσεων εις βάρος του οπίσθιου τοιχώματος με συγκέντρωση περιοχών υψηλών τοιχωματικών τάσεων στην τελική κατάσταση. Εφόσον το οπίσθιο τοίχωμα είναι η συνηθέστερη θέση της ρήξης τέτοιες παρατηρήσεις πιθανά είναι χρήσιμες στον καθορισμό της φυσικής ιστορίας των ΑΚΑ και τον προσδιορισμό παραγόντων κινδύνου που προβλέπουν αυξημένο κίνδυνο ρήξης.Στη συνέχεια με τη χρήση ΗΚΓ-καθοδηγούμενη CT αγγειογραφία μελετήσαμε τις μηχανικές ιδιότητες του ανευρύσματος και συμπεραίνουμε ότι ανευρυσματικό τοίχωμα παρουσιάζεται περισσότερο ανένδοτο από την φυσιολογική αορτή ενώ ο αυλός παραμορφώνεται σημαντικά στη διάρκεια του καρδιακού κύκλου κάτι που πιθανά υποδεικνύει έναν αποσβεστικό ρόλο του θρόμβου που απορροφά μέρος της συστηματικής πίεσης προστατεύοντας το τοίχωμα.Όσον αφορά την επίδραση της κατανομής του θρόμβου στον κίνδυνο ταχείας αύξησης, φαίνεται ότι η οπίσθια εναπόθεση ενδεχόμενα δρα προστατευτικά μειώνοντας τις τάσεις που ασκούνται στο οπίσθιο τοίχωμα του ανευρύσματος (η συχνότερη θέση της ρήξης) και σχετίζεται με βραδύτερη αύξηση των διαστάσεων του με την πάροδο του χρόνου.Τέλος με τη συνεκτίμηση γεωμετρικών, βιοχημικών και γεωμετρικών παραμέτρων ένα decision tree αναπτύχθηκε που ταξινομεί τα ανευρύσματα σε ομάδες ταχείας και βραδείας αύξησης. Η σημαντικότερη παράμετρος από όλες ήταν κατανομή του θρόμβου εντός του ανευρυσματικού σάκου. Στον αλγόριθμο ακόμα περιλαμβάνονταν ο σχετικός όγκος του θρόμβου και η γωνίωση του αυχένα του ανευρύσματος. 29/34 περιπτώσεις προβλέπονταν με ακρίβεια με βάση το παραπάνω μοντέλο (ακρίβεια 85%)