Diagnostic Accuracy of MRI for Differentiation of Benign and Malignant Pancreatic Cystic Lesions Compared to CT and Endoscopic Ultrasound: Systematic Review and Meta-analysis.

BACKGROUND: Differentiation of benign and malignant pancreatic cystic lesions on MRI, computed tomography (CT), and endoscopic ultrasound (EUS) is critical for determining management. PURPOSE: To perform a systematic review evaluating the diagnostic accuracy of MRI for diagnosing malignant pancreatic cystic lesions, and to compare the accuracy of MRI to CT and EUS. STUDY TYPE: Systematic review and meta-analysis. DATA SOURCES: MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, Web of Science, and Scopus were searched until February 2020 for studies reporting MRI accuracy for assessing pancreatic cystic lesions. FIELD STRENGTH: 1.5T or 3.0T. ASSESSMENT: Methodologic and outcome data were extracted by two reviewers (AU and MA, 2 years of experience each). All studies of pancreatic cystic lesions on MRI were identified. Studies with incomplete MRI technique were excluded. Risk of bias was assessed using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS)-2 tool. STATISTICAL TESTS: Sensitivity/specificity was pooled using bivariate random-effects meta-analysis with 95% confidence intervals (95%CI). Pairwise-comparison of MRI to CT and EUS was performed. The impact of gadolinium-based contrast agents, mucinous lesions, and risk of bias were explored using meta-regression. RESULTS: MRI pooled sensitivity was 76% (95%CI 67% to 84%) and specificity was 80% (95%CI 74% to 85%) for distinguishing benign and malignant lesions. MRI and CT had similar sensitivity (P = 0.822) and specificity (P = 0.096), but MRI was more specific than EUS (80% vs. 75%, P < 0.05). Studies including only contrast-enhanced MRI were more sensitive than those including unenhanced exams (P < 0.05). MRI sensitivity and specificity did not differ for mucinous lesions (P = 0.537 and P = 0.384, respectively) or for studies at risk of bias (P = 0.789 and P = 0.791, respectively). DATA CONCLUSION: MRI and CT demonstrate comparable accuracy for diagnosing malignant pancreatic cystic lesions. EUS is less specific than MRI, which suggests that, in some cases, management should be guided by MRI findings rather than EUS. LEVEL OF EVIDENCE: 3 TECHNICAL EFFICACY STAGE: 2.

Intestinal ammonia transport in freshwater and seawater acclimated rainbow trout (Oncorhynchus mykiss): evidence for a Na+ coupled uptake mechanism.

In vitro gut sac experiments were performed on freshwater and 60% seawater acclimated trout (Oncorhynchus mykiss) under treatments designed to discern possible mechanisms of intestinal ammonia transport. Seawater acclimation increased ammonia flux rate into the serosal saline (Jsamm) in the anterior intestine, however it did not alter Jsamm in the mid- or posterior intestine suggesting similar mechanisms of ammonia handling in freshwater and seawater fish. Both fluid transport rate (FTR) and Jsamm were inhibited in response to basolateral ouabain treatment, suggesting a linkage of ammonia uptake to active transport, possibly coupled to fluid transport processes via solvent drag. Furthermore, decreases in FTR and Jsamm caused by low Na(+) treatment indicated a Na(+) linked transport mechanism. Mucosal bumetanide (10(-4) M) had no impact on FTR, yet decreased Jsamm in the anterior and mid-intestine, suggesting NH4(+) substitution for K(+) on an apical NKCC, and at least a partial uncoupling of ammonia transport from fluid transport. Additional treatments (amiloride, 5-(N-ethyl-N-isopropyl)amiloride (EIPA), phenamil, bafilomycin, 4',6-diamidino-2-phenylindole (DAPI), high sodium) intended to disrupt alternative routes of Na(+) uptake yielded no change in FTR or Jsamm, suggesting the absence of direct competition between Na(+) and ammonia for transport. Finally, [(14)C]methylamine permeability (PMA) measurements indicated the likely presence of an intestinal Rh-mediated ammonia transport system, as increasing NH4Cl (0, 1, 5 mmol l(-1)) concentrations reduced PMA, suggesting competition for transport through Rh proteins. Overall, the data presented in this paper provide some of the first insights into mechanisms of teleost intestinal ammonia transport.

Quantitative and qualitative liver CT: imaging feature association with histopathologically confirmed hepatic cirrhosis.

PURPOSE: To assess the diagnostic performance of quantitative and qualitative imaging features of hepatic cirrhosis on CT. METHODS: A single-center retrospective cohort study was performed on all patients who had undergone non-targeted liver biopsy < 3 months following abdominal CT imaging between 2007 and 2020. Histopathology was required as a reference standard for hepatic cirrhosis diagnosis. Two readers independently assessed all CT quantitative and qualitative features, blinded to the clinical history and the reference standard. The diagnostic performance of each imaging feature was assessed using multivariate regression and logistic regression in a recursive feature elimination framework. RESULTS: 98 consecutive patients met inclusion criteria including 26 with histopathologically confirmed hepatic cirrhosis, and 72 without cirrhosis. Liver surface nodularity (p < 0.0001), lobar redistribution (p < 0.0001), and expanded gallbladder fossa (p < 0.0016) were qualitative CT features associated with liver cirrhosis consistent between both reviewers. Liver surface nodularity demonstrated highest sensitivity (73-77%) and specificity (79-82%). Falciform space width was the only quantitative feature associated with cirrhosis, for a single reviewer (p < 0.04). Using a recursive feature elimination framework, liver surface nodularity and falciform space width were the strongest performing features for identifying cirrhosis. No feature combinations strengthened diagnostic performance. CONCLUSION: Many quantitative and qualitative CT imaging signs of hepatic cirrhosis have either poor accuracy or poor inter-observer agreement. Qualitative imaging features of hepatic cirrhosis on CT performed better than quantitative metrics, with liver surface nodularity the most optimal feature for diagnosing hepatic cirrhosis.

An in vitro study of urea and ammonia production and transport by the intestinal tract of fed and fasted rainbow trout: responses to luminal glutamine and ammonia loading.

Digestion of dietary protein in teleosts results in high ammonia levels within the intestinal chyme that may reach concentrations that are many-fold greater than blood plasma levels. We used in vitro gut sac preparations of the ammoniotelic rainbow trout (Oncorhynchus mykiss) to investigate the role of the intestine in producing and transporting ammonia and urea, with specific focus on feeding versus fasting, and on responses to loading of the lumen with 2 mmol L-1 glutamine or 2 mmol L-1 ammonia. Feeding increased not only ammonia production and both mucosal and serosal fluxes, but also increased urea production and serosal fluxes. Elevated urea production was accompanied by an increase in arginase activity but minimal CPS III activity, suggesting that urea may be produced by direct arginolysis. The ammonia production and serosal fluxes increased in fasted preparations with glutamine loading, indicating an ability of the intestinal tissue to deaminate glutamine and perhaps use it as an energy source. However, there was little evidence of urea production or transport resulting from the presence of glutamine. Furthermore, the intestinal tissues did not appear to convert surplus ammonia to urea as a detoxification mechanism, as urea production and serosal flux rates decreased in fed preparations, with minimal changes in fasted preparations. Nevertheless, there was indirect evidence of detoxification by another pathway, as ammonia production rate decreased with ammonia loading in fed preparations. Overall, our study suggests that intestinal tissues of rainbow trout have the ability to produce urea and detoxify ammonia, likely via arginolysis.

A comparative study of platelet factor 4-enhanced platelet activation assays for the diagnosis of heparin-induced thrombocytopenia.

BACKGROUND: Functional platelet activation assays, such as the serotonin release assay (SRA), are the gold standard for the diagnosis of heparin-induced thrombocytopenia (HIT). Recently, platelet activation assays using added platelet factor 4 (PF4) have been described and suggest improved sensitivity. Direct comparisons of these assays have not been performed. OBJECTIVE: We compare the performance characteristics of three PF4-enhanced platelet activation assays, the PF4/heparin-SRA (PF4/hep-SRA), the PF4-SRA, and the P-selectin expression assay (PEA), at a single reference laboratory. METHODS: Serum samples from two cohorts of patients were used. The referral cohort (n = 84) included samples that had previously undergone routine diagnostic testing for HIT and tested positive or negative using the SRA. The clinical cohort (n = 101) consisted of samples from patients with clinically confirmed HIT whose serum contained platelet-activating antibodies. We simultaneously tested all samples in PF4-enhanced SRA-based assays (PF4/hep-SRA, PF4-SRA) and the flow cytometry-based PEA. RESULTS: In the referral cohort, the three PF4-enhanced assays identified all samples that were previously determined to be positive in the SRA. However, specificity of the PF4/hep-SRA was 96.6%, the PF4-SRA was 84.7%, and the PEA was 67.8%. In the clinical cohort of samples, all SRA-based assays displayed high performance characteristics (>92.1% sensitivity, >98.4% specificity). Sensitivity and specificity of the PEA was the lowest, 65.8% and 63.5%, respectively; but improved to 92.1% and 96.8% using preselected platelet donors. CONCLUSIONS: All PF4-enhanced assays demonstrated good performance characteristics when platelet donors were preselected. Further comparisons across multiple laboratories should be conducted for consensus on optimal HIT diagnostic testing.

An in vitro analysis of intestinal ammonia transport in fasted and fed freshwater rainbow trout: roles of NKCC, K+ channels, and Na+, K+ ATPase.

We examined mechanisms of ammonia handling in the anterior, mid, and posterior intestine of unfed and fed freshwater rainbow trout (Oncorhynchus mykiss), with a focus on the Na+:K+:2Cl- co-transporter (NKCC), Na+:K +-ATPase (NKA), and K+ channels. NKCC was localized by immunohistochemistry to the mucosal (apical) surface of enterocytes, and NKCC mRNA was upregulated after feeding in the anterior and posterior segments. NH4+ was equally potent to K+ in supporting NKA activity in all intestinal sections. In vitro gut sac preparations were employed to examine mucosal ammonia flux rates (Jmamm, disappearance from the mucosal saline), serosal ammonia flux rates (Jsamm, appearance in the serosal saline), and total tissue ammonia production rates (Jtamm = Jsamm - Jmamm). Bumetanide (10-4 mol L-1), a blocker of NKCC, inhibited Jsamm in most preparations, but this was largely due to reduction of Jtamm; Jmamm was significantly inhibited only in the anterior intestine of fed animals. Ouabain (10-4 mol L-1), a blocker of NKA, generally reduced both Jmamm and Jsamm without effects on Jtamm in most preparations, though the anterior intestine was resistant after feeding. Barium (10-2 mol L-1), a blocker of K+ channels, inhibited Jmamm in most preparations, and Jsamm in some, without effects on Jtamm. These pharmacological results, together with responses to manipulations of serosal and mucosal Na+ and K+ concentrations, suggest that NKCC is not as important in ammonia absorption as previously believed. NH4+ appears to be taken up through barium-sensitive K+ channels on the mucosal surface. Mucosal NH4+ uptake via both NKCC and K+ channels is energized by basolateral NKA, which plays an additional role in scavenging NH4+ on the serosal surface to possibly minimize blood toxicity or enhance ion uptake and amino acid synthesis following feeding. Together with recent findings from other studies, we have provided an updated model to describe the current understanding of intestinal ammonia transport in teleost fish.

An in vitro analysis of intestinal ammonia handling in fasted and fed freshwater rainbow trout (Oncorhynchus mykiss).

Ammonia transport and metabolism were investigated in the intestinal tract of freshwater rainbow trout which had been either fasted for 7 days, or fasted then fed a satiating meal of commercial trout pellets. In vivo, total ammonia concentrations (T amm) in the chyme were approximately 1 mmol L(-1) across the entire intestine at 24 h after the meal. Highest chyme pH and P NH3 values occurred in the posterior intestine. In vitro gut sac experiments examined ammonia handling with mucosal (Jmamm) and serosal (Js amm) fluxes under conditions of fasting and feeding, with either background (control ≤ 0.013 mmol L(-1)) or high luminal ammonia concentrations (HLA = 1 mmol L(-1)), the latter mimicking those seen in chyme in vivo. Feeding status (fasted or fed) appeared to influence ammonia handling by each individual section. The anterior intestine exhibited the greatest Jm amm and Js amm values under fasted control conditions, but these differences tended to disappear under typical post-feeding conditions when total endogenous ammonia production (Jt amm = Js amm - Jm amm, signs considered) was greatly elevated in all intestinal sections. Under fasted conditions, glutamate dehydrogenase (GDH) and glutaminase (GLN) activities were equal across all sections, but the ammonia-trapping enzyme glutamine synthetase (GS) exhibited highest activity in the posterior intestine, in contradiction to previous literature. Feeding clearly stimulated the total rate of endogenous ammonia production (Jt amm), even in the absence of a high luminal ammonia load. This was accompanied by an increase in GDH activity of the anterior intestine, which was also the site of the largest Jt amm. In all sections, during HLA exposure, either alone or in combination with feeding, there were much larger increases in endogenous Jt amm, most of which was effluxed to the serosal solution. This is interpreted as a response to avoid potential cytotoxicity due to overburdened detoxification mechanisms in the face of elevated mucosal ammonia. Thus T amm of the intestinal tissue remained relatively constant regardless of feeding status and exposure to HLA. Ammonia production by the gut may explain up to 18 % of whole-body ammonia excretion in vivo under fasting conditions, and 47 % after feeding, of which more than half originates from endogenous production rather than from absorption from the lumen.