Alternative ileal flap for bladder augmentation if mesentery is short

PURPOSE

To date the clam ileocystoplasty is the preferred method of bladder augmentation in children when the urodynamic problem is non-compliance and/or detrusor overactivity. The key to this technique is the incision of the bladder wall deep into the pelvis down to the trigone in order to avoid a diverticulum like neobladder and to provide adequate margin for augmentation. The detubularised ileum flap therefore has to reach to the bottom of the divided bladder on a reliable vascular pedicle without significant tension. A short ileal mesentery caused by previous surgery, peritonitis, peritoneal dialysis or ventriculo-peritoneal shunt may complicate surgery and compromise outcome. We hypothesized we can rely on the communication of the intramural vessels within the intestine and can detubularise the ileum adjacent to the mesentery rather than along the antimesenteric line and this could be combined with ligation of some vasa recta (VR) in order to create alternative ileum flaps, which reach further into the pelvis. Our aim was to assess the viability of the alternative flaps detubularised along the paramesenteric line and measure how many VR could be sacrificed beyond the tertiary arcades.

MATERIALS AND METHODS

After ethical approval adjacent ileal segments were detubulirased along the antimesenteric line (Group 1) and along the paramesenteric line (Group 2) in 5 minipigs in general anaesthesia. Ligation of 0,1,2,3 and 4 VR has been performed starting from the free end of the segments. The length of the ileal flaps was recorded. The microcirculation of flap edges was detected by in vivo microscopy using orthogonal polarising spectral imaging (Cytoscan A/R Cytometrics, PA, USA). Clam ileocystoplasty was performed with the ileum detubularised along the paramesenteric line without ligation of VR. Specimens of the augmented bladder were obtained after 4 weeks and stained with Hematoxilin + Eosin.

RESULTS

No alteration in capillary red blood cell velocity (RBCV) and perfusion rate (PR) was observed after paramesenteric detubularisation. The flaps in Group 2 reached 20.25 ± 0.5 mm longer vs.

CONTROL

This is 98% of the mean bowel width (20.5 ± 0.57 mm) measured in the animals. Ligation of each VR further increased the length of both flaps (mean: 10.59 ± 3.18 mm) however ligation of more than 2 VR gradually decreased the microcirculation in both groups. All animals augmented with alternative flap survived, there was no urine leak or suture break down. Histology confirmed viable bowel flaps.

CONCLUSION

Paramesenteric detubularisation of the ileum is fully tolerated and results in longer reaching ileal flap vs.

CONTROL

Only limited ligation of VR is tolerated.

DISCUSSION

This study showed the first time that clam ileocystoplasty is feasible with ileal flap detubularised along the paramesenteric line. The use of the animal model and the relative short postoperative observation are the main limitations of this study.

Flow curves of colloidal dispersions close to the glass transition. Asymptotic scaling laws in a schematic model of mode coupling theory

The flow curves, viz. the curves of stationary stress under steady shearing, are obtained close to the glass transition in dense colloidal dispersions using asymptotic expansions in the schematic F₁₂(γ)-model of mode coupling theory. The shear thinning of the viscosity in fluid states and the yielding of glassy states is discussed. At the transition between fluid and shear-molten glass, simple and generalized Herschel-Bulkley laws are derived with power law exponents that can be computed for different particle interactions from the equilibrium structure factor.

Shear stresses of colloidal dispersions at the glass transition in equilibrium and in flow

We consider a model dense colloidal dispersion at the glass transition, and investigate the connection between equilibrium stress fluctuations, seen in linear shear moduli, and the shear stresses under strong flow conditions far from equilibrium, viz., flow curves for finite shear rates. To this purpose, thermosensitive core-shell particles consisting of a polystyrene core and a cross-linked poly(N-isopropylacrylamide) shell were synthesized. Data over an extended range in shear rates and frequencies are compared to theoretical results from integrations through transients and mode coupling approaches. The connection between nonlinear rheology and glass transition is clarified. While the theoretical models semiquantitatively fit the data taken in fluid states and the predominant elastic response of glass, a yet unaccounted dissipative mechanism is identified in glassy states.