NUTRITIONAL IMAGING (TRYGVE HAUSKEN)Nutritional imaging is US imaging to study the effects of nutrition such as fat, proteins and glucose on thefunction of the GI tract. Information concerning movement of luminal contents in humans can be obtained byfluoroscopy, scintigraphy, MRI, impedance and duplex sonography. Studies based on scintigraphy and standardUS of the stomach and duodenum will indirectly measure overall rates of gastric emptying, but these methods donot have the temporal resolution to assess the rapid changes of transpyloric flow.Hausken et al showed that using pulsed Doppler combined with real-time US (Duplex sonography) it ispossible to visualize antroduodenal motility and transpyloric flow simultaneously. Antegrade and retrogradetranspyloric flow is visualized using bidirectional velocity curves. Most contractions of the proximal duodenalbulb precede closure of the pylorus (and the terminal antrum), and duodenal bulb contraction is oftenaccompanied by a short burst of duodenogastric reflux occurring immediately before closure of the pylorus.Studies of the antropyloroduodenal region are performed with the ultrasound probe positioned at thelevel of the transpyloric plane, and the antrum, the pylorus and the proximal duodenum visualizedsimultaneously. The subjects are studied in a seated position, with a 3,5 -5 MHz transducer.In order to study the relation between motility and flow in detail, techniques with a high temporal andspatial resolution are required for the assessment of antropyloroduodenal pressure waves and transpyloric flow.Subjects have to be intubated with a manometric assembly, which is introduced trans-nasally and positioned inthe antropyloroduodenal region using fluoroscopy. The Doppler/US and manometric recordings has to besynchronized.Gastric emptying of a low caloric liquid meal follows sequences of emptying-reflux-emptying pulses.About half of the sequences are peristaltic related, but both non-occluding, peristaltic related and non-peristalticrelated emptying sequences occur. Non-peristaltic related flow sequences have often more alternating emptyingrefluxepisodes than those associated with peristalsis, and the duration of non-peristaltic related emptying andreflux pulses are longer. The pressure gradients for all types of emptying are low and the pressure gradientsduring non-peristaltic related emptying are significantly lower than during peristaltic related emptying.Flow can only occur in the presence of an open pylorus. Transpyloric flow can be classified into flow associatedwith a local increase in the pressure gradient between antrum and duodenum (Pa - Pd) due to antral propagatingpressure waves, and flow associated with a common cavity pressure difference between the distal antrum and theproximal duodenum as was observed during non-peristaltic related flow. The second type of flow is independentof peristalsis and is likely to be caused by changes in gastric tone, or by pressure changes outside the stomachsuch as aortic pulsation and inspiration. The method can be used to study normal physiology andpathophysiology of the gastro-pyloro-duodenal segment and to monitor the effect of medications on transpyloricflow.Patients with functional dyspepsia often experience early satiety and discomfort after a meal. Usingduplex sonography it is possible to relate timing of symptoms and early postprandial emptying in patients withfunctional dyspepsia(44). Meal related discomfort was experienced after commencement of transpyloricemptying. An inverse relationship was found between the duration of the tasting period and symptom intensitysuggesting that the time allowed for duodenal tasting might be too short in patients with functional dyspepsia.In another study the effects of healthy aging on transpyloric flow and gastric emptying were evaluatedby the use of Doppler ultrasonography and scintigraphy together with the relationship between the glycemicresponse to oral glucose and transpyloric flow(45). Ten healthy “young” and 8 healthy “older”, subjects hadsimultaneous measurements of transpyloric flow, gastric emptying, and blood glucose after a 600-ml drink (75 gglucose labelledPostprandial hypotension frequently occurs in the elderly. The hypotensive response to a meal istriggered by the interaction of nutrients with the small intestine. Information relating to the effects of differentmacronutrients on blood pressure (BP) is limited and inconsistent.The effects of intraduodenal glucose, fat, and protein were determined on blood pressure, heart rate(HR), and superior mesenteric artery (SMA) blood flow in healthy older subjects. Eight subjects receivedintraduodenal glucose (64 g), fat (10% oil emulsion), protein (72 g whey), or saline (0.9%) at a rate of 2.7mL/min for 90 min, followed by intraduodenal saline for 30 min. Blood pressure, heart rate, and SMA blood flowwere measured. The falls in systolic BP during infusions of glucose, fat, and protein did not differ significantly (P= 0.97); however, the fall occurred significantly earlier during the glucose infusion; than during the fat (P=0.02)and protein min; P=0.04) infusions. The increases in HR during glucose, fat, and protein infusions (P=0.0001 forall) did not differ significantly. SMA blood flow increased significantly after all infusions (P = 0.001 for all), butthe increase was significantly (P =0.05) lower after protein than after the other infusions. Intraduodenal glucose,fat, and protein decrease systolic BP in healthy older subjects, but the onset of the hypotensive response is earlierafter glucose, and the effect of protein on SMA blood flow is less than that of the other nutrients.Eight health women had gastric emptying measured using 2D ultrasound. Antral area was measuredfasting and in intervals of 15 minutes. After 120 minutes most of the meal had emptied. This method wasevaluated against the paracetamol test.
CEUS ved Crohns sykdomKIM NYLUND Institutt for indremedisin, Universitetet i BergenKontrastforsterket ultralyd (CEUS) er en relativ ny undersøkelsesmodalitet og i EFSUMBsretningslinjer fra 2008 inngår ikke undersøkelse av tarm ved IBD. Siden 2001 er imidlertiden rekke studier publisert hvor man har undersøkt om CEUS kan brukes for å forbedre ogsupplere diagnostikken ved Crohns sykdom.De første studiene ble gjort med mikrobobler med kort halveringstid og powerDoppler ogkontrasten gav et øyeblikksbilde som hovedsaklig ble brukt for å øke sensitiviteten fordeteksjon av små kar. Når mer stabile mikrobobler og scanning med lav mekanisk index(MI) kom på markedet, kom mulighetene for å undersøke kontrastintensitet over tid ogdermed også indirekte perfusjonsmål.CEUS med lav MI kan brukes til å kartlegge vaskularitet i tarmveggen. Det gjør metodenspesielt egnet til å skille høyt vaskularisert vev fra avaskularisert vev og dermedinflammatoriske infiltrater fra abscesser. Noen studier viser dessuten at kontrastfunnkorrelerer med klinisk sykdomsaktivitet mens det er mer usikkert om kontrast kan brukestil å skille inflammasjon fra fibrose i stenotiske tarmpartier.CEUS av Crohn–pasienter brukes i dag som et supplement til en vanligultralydundersøkelse i tilfeller hvor man trenger ekstra informasjon for å skilleinflammatoriske infiltrater fra abscesser. Øvrig bruk er i relasjon til forskningsprosjekter.Forbedringer i metode og utstyr kan i nær fremtid gjøre CEUS mer anvendelig. Bedreteknikker for avbildning av kontrast kan gi kvalitativt bedre informasjon om vaskularitet itarmveggen. Automatiserte analyser av av tids-intensitets data med bevegelseskorreksjonog bedre kurvetilpasninger kan øke reliabiliteten av slike data. Stabile mikrobobler medmindre diameter vil være bedre egnet i kombinasjon med høyfrekvente ultralydprober.Mikrobobler med spesifikke antistoffer for endotelreseptorer gir dessuten mulighet for åkartlegge mikrovaskularitet over større områder ved hjelp av en enkelt injeksjon. Mens detekniske forbedringer er nært forestående vil sannsynligvis introduksjonen av nyemikrobobler ta lengre tid.
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