A case report of intersigmoid hernia treated using laparoscopic surgery.

INTRODUCTION AND IMPORTANCE: Intersigmoid hernia (ISH) is a rare disease that is difficult to diagnose preoperatively and sometimes causes intestinal necrosis that requires emergency surgery. CASE PRESENTATION: The patient was an 87-year-old male with no history of abdominal surgery who visited our emergency outpatient service due to left lower quadrant pain and vomiting as chief complaints. Abdominal findings showed tenderness with the severest point in the left lower quadrant of the abdomen. Contrast-enhanced CT showed poor imaging of the dorsal sigmoid colon and an expanded proximal small intestine, with regional ascites around the small intestines. The patient was diagnosed with small bowel obstruction associated with ISH incarceration and underwent emergency surgery. Invagination of the small intestine into the intersigmoid fossa was found by laparoscopy. The incarcerated part was removed and the hernia orifice was sutured and closed. Mild congestion was seen in the incarcerated small intestine, but with no findings of ischemia. Thus, intestinal resection was determined to be unnecessary. The postoperative course was good and the patient was discharged on postoperative day 6. CLINICAL DISCUSSION: ISH is often diagnosed as simple ileus at the initial visit, which can result in delayed surgery. There are no case reports of complete remission of ISH with conservative therapy, and treatment with surgery is generally required. Our patient underwent early surgery because of CT findings that were characteristic of ISH and allowed diagnosis before surgery. CONCLUSION: Early diagnosis of ISH and performance of laparoscopic surgery can avoid the need for intestinal resection.

Calculation of solvation free energy utilizing a constrained QM/MM approach combined with a theory of solutions.

In an extended QM/MM (quantum mechanical/molecular mechanical) description of a solution, the solvent molecules surrounding the solute are incorporated into the QM region besides the solute. In a recent development, we introduced a simple and efficient method, referred to as boundary constraint with correction (BCC), to prevent the diffusion of the QM solvent into the bulk. The major purpose of the present work is to develop a method to compute the solvation free energy of a QM solute in an extended QM/MM simulation by means of the BCC method. The strategy of our development is to utilize the QM/MM-ER method which combines the QM/MM simulation and the theory of solutions termed energy representation (ER) to expedite the free energy calculation. A theory is, then, formulated to couple QM/MM-ER and the BCC method on the basis of the statistical mechanics. A notable feature of our method is that the effect of the constraint potentials on the free energy completely vanishes when the force field of the QM solvent coincides with that of the MM solvent. The method is applied to the calculations of the solvation free energies of a water molecule and a hydronium ion in water solutions. It turns out that the present method can offer a significant improvement in describing the free energy Δν of the hydronium ion, in particular, as compared with the conventional QM/MM approach. Explicitly, Δν is obtained as -98.0 kcal/mol showing a good agreement with an experimental value of -103.5 kcal/mol, while -86.1 kcal/mol by the conventional method.

A simple and effective solution to the constrained QM/MM simulations.

It is a promising extension of the quantum mechanical/molecular mechanical (QM/MM) approach to incorporate the solvent molecules surrounding the QM solute into the QM region to ensure the adequate description of the electronic polarization of the solute. However, the solvent molecules in the QM region inevitably diffuse into the MM bulk during the QM/MM simulation. In this article, we developed a simple and efficient method, referred to as the "boundary constraint with correction (BCC)," to prevent the diffusion of the solvent water molecules by means of a constraint potential. The point of the BCC method is to compensate the error in a statistical property due to the bias potential by adding a correction term obtained through a set of QM/MM simulations. The BCC method is designed so that the effect of the bias potential completely vanishes when the QM solvent is identical with the MM solvent. Furthermore, the desirable conditions, that is, the continuities of energy and force and the conservations of energy and momentum, are fulfilled in principle. We applied the QM/MM-BCC method to a hydronium ion(H3O+) in aqueous solution to construct the radial distribution function (RDF) of the solvent around the solute. It was demonstrated that the correction term fairly compensated the error and led the RDF in good agreement with the result given by an ab initio molecular dynamics simulation.