Magnetic Resonance Imaging Availability Reduces Computed Tomography Use for Pediatric Appendicitis Diagnosis.

OBJECTIVES: To determine if introducing magnetic resonance imaging (MRI) as an imaging option for children with suspected appendicitis and an inconclusive ultrasound reduces computed tomography (CT) use. METHODS: This is a retrospective cohort study of patients aged 5 to 18 years who presented to a pediatric emergency department (ED) with suspected appendicitis. Rates of CT use 1 year before and 1 year after MRI availability are compared. Secondary outcomes include missed and negative appendectomies, imaging charges, time to antibiotics and surgery, time to radiology read, ED length of stay, and test characteristics of MRI and CT. RESULTS: Of the 981 patients screened, 499 patients met inclusion criteria. There was an absolute reduction of CT use of 25% from 38% in year 1 to 13% in year 2 (95% confidence interval, 18% to 33%). Advanced imaging charges were $371 higher in year 2 (MRI) than year 1 (CT), and median time to radiologist reads was longer in MRIs than CTs (129 versus 62 minutes; difference 53 minutes, 95% confidence interval, 23 to 74 minutes). All other secondary outcomes, including ED length of stay and test characteristics, were statistically similar. CONCLUSIONS: Introducing MRI for as an imaging option for children with suspected appendicitis and an inconclusive ultrasound markedly reduced CT use, but did result in a small increase in imaging charges and time to preliminary radiology read.

Inverse Thermoreversible Mechanical Stiffening and Birefringence in a Methylcellulose/Cellulose Nanocrystal Hydrogel.

We show that composite hydrogels comprising methyl cellulose (MC) and cellulose nanocrystal (CNC) colloidal rods display a reversible and enhanced rheological storage modulus and optical birefringence upon heating, i.e., inverse thermoreversibility. Dynamic rheology, quantitative polarized optical microscopy, isothermal titration calorimetry (ITC), circular dichroism (CD), and scanning and transmission electron microscopy (SEM and TEM) were used for characterization. The concentration of CNCs in aqueous media was varied up to 3.5 wt % (i.e, keeping the concentration below the critical aq concentration) while maintaining the MC aq concentration at 1.0 wt %. At 20 °C, MC/CNC underwent gelation upon passing the CNC concentration of 1.5 wt %. At this point, the storage modulus ( G') reached a plateau, and the birefringence underwent a stepwise increase, thus suggesting a percolative phenomenon. The storage modulus ( G') of the composite gels was an order of magnitude higher at 60 °C compared to that at 20 °C. ITC results suggested that, at 60 °C, the CNC rods were entropically driven to interact with MC chains, which according to recent studies collapse at this temperature into ring-like, colloidal-scale persistent fibrils with hollow cross-sections. Consequently, the tendency of the MC to form more persistent aggregates promotes the interactions between the CNC chiral aggregates towards enhanced storage modulus and birefringence. At room temperature, ITC shows enthalpic binding between CNCs and MC with the latter comprising aqueous, molecularly dispersed polymer chains that lead to looser and less birefringent material. TEM, SEM, and CD indicate CNC chiral fragments within a MC/CNC composite gel. Thus, MC/CNC hybrid networks offer materials with tunable rheological properties and access to liquid crystalline properties at low CNC concentrations.

Primary Primitive Neuroectodermal Tumor Arising from an Ovarian Mature Cystic Teratoma in a 12-Year-Old Girl: A Case Report.

BACKGROUND: Ovarian mature cystic teratomas (MCTs) rarely transform to primary primitive neuroectodermal tumors. This case report offers evidence that MCTs might have undetected microfoci of malignant neural tumors. CASE: We describe the case of a 12-year-old girl who presented with right-sided abdominal pain and distention. Intraoperative findings revealed a right ovarian MCT. However, pathology showed a 0.5-cm focus of malignant neural tumor within the 11-cm MCT. SUMMARY AND CONCLUSION: This patient will need close follow-up with a multidisciplinary team because the clinical implications of this transformation has yet to be defined.

Nontuberculous mycobacterial adenitis outside of the head and neck region in children: A case report and systematic review of the literature.

Nontuberculous mycobacterial (NTM) adenitis of the head and neck region is well-described in healthy children, most commonly presenting under the age of 5years. Extracervicofacial NTM adenitis is less common. We present a case of NTM inguinal adenitis in a 2-year-old girl, followed by a systematic review of the literature.

Intestinal barrier dysfunction in human necrotizing enterocolitis.

BACKGROUND: Intestinal barrier dysfunction has been implicated in necrotizing enterocolitis (NEC), but has not been directly measured in human NEC. METHODS: Small intestines removed during surgery were immediately mounted in an Ussing chamber. mRNA expression of tight junction (TJ) proteins was measured with RT-PCR. RESULTS: Fifteen infants were included, 5 with NEC and 10 with other diagnoses. Average transepithelial resistance (TER) was 11.61±1.65Ω/cm2 in NEC specimens, 23.36±1.48Ω/cm2 at resection margin, and 46.48±5.65Ω/cm2 in controls. Average flux of permeability marker mannitol was 0.23±0.06µMol/cm2 per h in NEC, 0.04±0.01 µMol/cm2 per h at resection margin, and 0.017±0.004 µMol/cm2 per h in control tissue (p<0.05). RT-PCR analysis showed marked decrease in mRNA expression of a TJ protein occludin in NEC affected tissue (p<0.03 vs. control). Additionally, mRNA expression of myosin light chain kinase (MLCK), an important regulator of TJ permeability, was increased in NEC specimens. CONCLUSION: These studies show for the first time that NEC intestinal tissue have increased intestinal permeability, even at grossly healthy-appearing resection areas. The increase in intestinal permeability in NEC appeared to be related in part to a decrease in occludin and an increase in MLCK expression. LEVEL OF EVIDENCE: Level 2.

Hybrid supramolecular and colloidal hydrogels that bridge multiple length scales.

Hybrid nanocomposites were constructed based on colloidal nanofibrillar hydrogels with interpenetrating supramolecular hydrogels, displaying enhanced rheological yield strain and a synergistic improvement in storage modulus. The supramolecular hydrogel consists of naphthyl-functionalized hydroxyethyl cellulose and a cationic polystyrene derivative decorated with methylviologen moieties, physically cross-linked with cucurbit[8]uril macrocyclic hosts. Fast exchange kinetics within the supramolecular system are enabled by reversible cross-linking through the binding of the naphthyl and viologen guests. The colloidal hydrogel consists of nanofibrillated cellulose that combines a mechanically strong nanofiber skeleton with a lateral fibrillar diameter of a few nanometers. The two networks interact through hydroxyethyl cellulose adsorption to the nanofibrillated cellulose surfaces. This work shows methods to bridge the length scales of molecular and colloidal hybrid hydrogels, resulting in synergy between reinforcement and dynamics.

Hybrid Supramolecular and Colloidal Hydrogels that Bridge Multiple Length Scales.

Hybrid nanocomposites were constructed based on colloidal nanofibrillar hydrogels with interpenetrating supramolecular hydrogels, displaying enhanced rheological yield strain and a synergistic improvement in storage modulus. The supramolecular hydrogel consists of naphthyl-functionalized hydroxyethyl cellulose and a cationic polystyrene derivative decorated with methylviologen moieties, physically cross-linked with cucurbit[8]uril macrocyclic hosts. Fast exchange kinetics within the supramolecular system are enabled by reversible cross-linking through the binding of the naphthyl and viologen guests. The colloidal hydrogel consists of nanofibrillated cellulose that combines a mechanically strong nanofiber skeleton with a lateral fibrillar diameter of a few nanometers. The two networks interact through hydroxyethyl cellulose adsorption to the nanofibrillated cellulose surfaces. This work shows methods to bridge the length scales of molecular and colloidal hybrid hydrogels, resulting in synergy between reinforcement and dynamics.

Cationic polymer brush-modified cellulose nanocrystals for high-affinity virus binding.

Surfaces capable of high-affinity binding of biomolecules are required in several biotechnological applications, such as purification, transfection, and sensing. Therein, the rod-shaped, colloidal cellulose nanocrystals (CNCs) are appealing due to their large surface area available for functionalization. In order to exploit electrostatic binding, their intrinsically anionic surfaces have to be cationized as biological supramolecules are predominantly anionic. Here we present a facile way to prepare cationic CNCs by surface-initiated atom-transfer radical polymerization of poly(N,N-dimethylaminoethyl methacrylate) and subsequent quaternization of the polymer pendant amino groups. The cationic polymer brush-modified CNCs maintained excellent dispersibility and colloidal stability in water and showed a ζ-potential of +38 mV. Dynamic light scattering and electron microscopy showed that the modified CNCs electrostatically bind cowpea chlorotic mottle virus and norovirus-like particles with high affinity. Addition of only a few weight percent of the modified CNCs in water dispersions sufficed to fully bind the virus capsids to form micrometer-sized assemblies. This enabled the concentration and extraction of the virus particles from solution by low-speed centrifugation. These results show the feasibility of the modified CNCs in virus binding and concentrating, and pave the way for their use as transduction enhancers for viral delivery applications.

Molecular engineering of fracture energy dissipating sacrificial bonds into cellulose nanocrystal nanocomposites.

Even though nanocomposites have provided a plethora of routes to increase stiffness and strength, achieving increased toughness with suppressed catastrophic crack growth has remained more challenging. Inspired by the concepts of mechanically excellent natural nanomaterials, one-component nanocomposites were fabricated involving reinforcing colloidal nanorod cores with polymeric grafts containing supramolecular binding units. The concept is based on mechanically strong native cellulose nanocrystals (CNC) grafted with glassy polymethacrylate polymers, with side chains that contain 2-ureido-4[1H]-pyrimidone (UPy) pendant groups. The interdigitation of the grafts and the ensuing UPy hydrogen bonds bind the nanocomposite network together. Under stress, UPy groups act as sacrificial bonds: simultaneously providing adhesion between the CNCs while allowing them to first orient and then gradually slide past each other, thus dissipating fracture energy. We propose that this architecture involving supramolecular binding units within side chains of polymer grafts attached to colloidal reinforcements opens generic approaches for tough nanocomposites.

Thermoresponsive Nanocellulose Hydrogels with Tunable Mechanical Properties.

Cellulose microfibrils physically bound together by soft hemicellulose chains form the scaffolding that makes plant cell walls strong. Inspired by this architecture, we designed biomimetic thermoreversible hydrogel networks based on reinforcing cellulose nanocrystals (CNC) and thermoresponsive methylcellulose (MC). Upon dissolving MC powder in CNC aqueous dispersions, viscoelastic dispersions were formed at 20 °C, where the storage modulus (G') is tunable from 1.0 to 75 Pa upon increasing the CNC concentration from 0 to 3.5 wt % with 1.0 wt % MC. By contrast, at 60 °C a distinct gel state is obtained with G' ≫ G″, G' ∼ ω0, with an order of magnitude larger G' values from 110 to 900 Pa upon increasing the CNC concentration from 0 to 3.5 wt % with constant 1.0 wt % MC, due to the physical cross-links between MC and CNCs. Therefore, simply mixing two sustainable components leads to the first all-cellulose thermoreversible and tunable nanocellulose-based hydrogels.

Polyelectrolyte brushes grafted from cellulose nanocrystals using Cu-mediated surface-initiated controlled radical polymerization.

Herein we report the synthesis of cellulose nanocrystals (CNCs) grafted with poly(acrylic acid) (PAA) chains of different lengths using Cu-mediated surface initiated-controlled radical polymerization (SI-CRP). First, poly(tert-butylacrylate) (PtBA) brushes were synthesized; then, subsequent acid hydrolysis was used to furnish PAA brushes tethered onto the CNC surfaces. The CNCs were chemically modified to create initiator moieties on the CNC surfaces using chemical vapor deposition (CVD) and continued in solvent phase in DMF. A density of initiator groups of 4.6 bromine ester groups/nm(2) on the CNC surface was reached, suggesting a dense functionalization and a promising starting point for the controlled/living radical polymerization. The SI-CRP of tert-butylacrylate proceeded in a well-controlled manner with the aid of added sacrificial initiator, yielding polymer brushes with polydispersity values typically well below 1.12. We calculated the polymer brush grafting density to almost 0.3 chains/nm(2), corresponding to high grafting densities and dense polymer brush formation on the nanocrystals. Successful rapid acid hydrolysis to remove the tert-butyl groups yielded pH-responsive PAA-polyelectrolyte brushes bound to the CNC surface. Individually dispersed rod-like nanoparticles with brushes of PtBA or PAA were clearly visualized by AFM and TEM imaging.

Acute celiac artery compression syndrome after surgical correction of Scheuermann kyphosis.

STUDY DESIGN: A case of acute celiac artery compression syndrome after spinal fusion in a patient with Scheuermann kyphosis is reported. OBJECTIVE: To describe the unusual complication of acute celiac artery compression after surgical kyphosis correction, to outline diagnostic methods, and to review the pertinent literature. SUMMARY OF BACKGROUND DATA: Chronic celiac artery compression syndrome is well described, yet there is only 1 reported case of acute celiac artery compression after surgical correction of kyphosis. There have been no previous reports of this complication leading to foregut ischemic necrosis after correction of Scheuermann kyphosis. METHODS: Case report and literature review. RESULTS: After an anterior release and posterior spinal fusion for a 106 degrees kyphotic deformity performed under 1 anesthetic, our patient developed a perforated gastric antrum on postoperative day 5, evolving to ischemic necrosis of the stomach, gallbladder, and spleen discovered on postoperative day 7. Abdominal angiography indicated that his celiac artery had been occluded at its origin. After this event, the patient required a prolonged intensive care hospital stay and required a Roux-en-Y gastro-jejeunostomy reconstruction. He is now doing well at 1-year follow-up with independent ambulation and a regular diet. CONCLUSION: Acute celiac artery compression after surgical kyphosis correction is a rare but potentially serious adverse event. Spinal deformity surgeons and intensivists should be aware of this entity, and should have a high index of suspicion for it if sepsis of unknown origin, an acute abdomen, or elevated liver enzymes are encountered after surgery after correction of a kyphotic deformity.

Evaluation of mulitprobe radiofrequency technology in a porcine model.

OBJECTIVE: We evaluated two new radiofrequency devices in an in vivo porcine model. MATERIALS AND METHODS: Multiprobe radiofrequency ablation (RFA) was used in a porcine model with an impedance-based algorithm in one experiment and clustered probes with and without switcher controllers in another; a Pringle maneuver was used with half of the ablations. RESULTS: The impedance experiment included 13 ablations, with a mean length of 7.0 cm and width of 2.9 cm (95% CI) and an average time of 596 s. Ablation volumes were significantly larger (54.1+/-11.7 cc(3) vs 34.9+/-4.8 cc(3), p<0.05) and ablation times were significantly shorter (359 s vs 834 s, p<0.05) for the Pringle group compared with the No Pringle group, respectively. The switcher controller experiment included 34 RFAs. Diameter (mm) (51.4 vs 40.3, p<0.0001), surface area (cm(2)) (22.4 vs 16.0, p<0.0002), and volume (cc) (66.1 vs 36.9, p<0.0001) were significantly larger for the combination probes with switcher controller compared with clustered probes, respectively. Ablation volumes for the Pringle vs No Pringle groups in the combination probes were 68.0 cc vs 64.3 cc and for the clustered probes 40.1 cc vs. 33.7 cc, respectively. CONCLUSION: Multiprobe ablations using RFA are promising technologies that need further study to evaluate their clinical utility.

Subphrenic and pleural abscess due to spilled gallstones.

BACKGROUND: A 70-year-old male approximately 3 years after laparoscopic cholecystectomy presented to his primary care physician with a 4-month history of generalized malaise. METHODS: A workup included magnetic resonance imaging that revealed a perihepatic abscess. The patient underwent ultrasound-guided drainage, with the removal of 1400 mL of purulent fluid and placement of 2 drains. Computed tomographic scanning showed resolution, and he was discharged home on oral antibiotics. At 2-month follow-up, the patient was asymptomatic, denying any constitutional symptoms. However, abdominal computed tomographic scanning revealed recurrence of the abscess, which measured approximately 18 x 9 x 7.5 cm, with mass effect on the liver. The patient was placed on intravenous antibiotics and scheduled for operative drainage. The abdomen was entered with a right subcostal incision, and 900 mL of purulent fluid was drained. We also noted abscess erosion through the inferolateral aspect of the right diaphragm into the pleural space. The pleural abscess was loculated and isolated from the lung parenchyma. Palpation within the abscess cavity revealed 9 large gallstones. Following copious irrigation and debridement of necrotic tissue, 3 drains were placed and the incision was closed. RESULTS: The patient had an uneventful recovery and was discharged home on postoperative day number 6. Follow-up imaging at 3 months demonstrated resolution of the collection. CONCLUSION: Spillage of gallstones is a complication of laparoscopic cholecystectomy, occurring in 6% to 16% of all cases. Retained stones rarely result in a problem, but when complications arise, aggressive surgical intervention is usually necessary.