Cystic dystrophy in heterotopic pancreas.

Cystic dystrophy in heterotopic pancreas, or paraduodenal pancreatitis, is a rare and complicated presentation involving heterotopic pancreatic tissue in the duodenal wall. This condition is present in 5% of the general population but disease mainly affects middle-aged alcoholic-smoking men with chronic pancreatitis (CP). It may be purely duodenal or segmental (pancreatico-duodenopathy). Its pathophysiology arises from alcohol toxicity with obstruction of small ducts of heterotopic pancreatic tissue present in the duodenal wall and the pancreatic-duodenal sulcus, leading to repeated episodes of pancreatitis. The symptomatology includes episodes of acute pancreatitis, weight loss, and vomiting due to duodenal obstruction. Imaging shows thickening of the wall of the second portion of the duodenum with multiple small cysts. A stepwise therapeutic approach is preferred. Conservative medical treatment is favored in first intention (analgesics, continuous enteral feeding, somatostatin analogues), which allows complete symptomatic regression in 57% of cases associated with a 5% rate of complications (arterial thrombosis and diabetes). Endoscopic treatment may also be associated with conservative measures. Surgery achieves a complete regression of symptoms in 79% of cases but with a 20% rate of complications. Surgery is indicated in case of therapeutic failure or in case of doubt about a malignant tumor. Pancreaticoduodenectomy and duodenal resection with pancreatic preservation (PPDR) seem to be the most effective treatments. PPDR has also been proposed as a first-line treatment for purely duodenal location of paraduodenal pancreatitis, thereby preventing progression to an extended segmental form.

Determining Water Transport Kinetics in Limestone by Dual-Wavelength Cavity Ring-Down Spectroscopy.

Water plays a major role in the deterioration of porous building materials such as those widely found in built heritage, influencing many physical, chemical, and biological decay processes. This article details a proof-of-principle study using near-infrared cavity ring-down spectroscopy (CRDS) to monitor the release of water and its artificially enriched isotopologues from small (ca. 25 × 25 × 5 mm) samples of limestone subject to drying by a fixed flow of nitrogen with varying levels of humidity and at room temperature and atmospheric pressure. Under low-humidity conditions, the drying kinetics are consistent with the well-established two-phase drying process exhibited by porous materials, namely, an initial constant drying rate period (phase I) followed by a falling drying rate period (phase II). The water diffusivity during phase II, DII, was measured (for Clipsham limestone) to be 3.0 × 10-9 ± 1 × 10-10 m2 s-1. The CRDS measurements allow spectroscopic determination of the total mass of water released by the sample, and the calculated values are in excellent agreement with gravimetric analysis. Importantly, the selectivity and sensitivity afforded by CRDS allows isotope analysis to be carried out, such that the flux of isotopically labeled water out of the sample can be determined under conditions of humidified flow where there may be a simultaneous ingress of water from the environment. Dual-wavelength CRDS distinguishes isotopic species, and it is demonstrated that the drying kinetics and physical properties of the samples are self-consistent when monitoring both HDO and H2O (for HDO, DII was 3.2 × 10-9 ± 4 × 10-10 m2 s-1). As the humidity levels in the flow increase, a departure from the distinct two-phase behavior is observed in the HDO drying curves. These new measurements of isotopically resolved mass fluxes will help refine models for drying mechanisms in porous media.