Functional versus radiological assessment of chronic intestinal ischaemia

Improvement of the splanchnic blood flow and hepatic vein oxygenation following revascularization in patients with chronic mesenteric ischaemia

OBJECTIVES

Chronic mesenteric ischaemia (CMI) is an underdiagnosed but severe condition. Access to functional testing is often limited and the diagnosis is usually based primarily on symptoms and imaging. One of the functional tests available is measurement of the splanchnic blood flow (SBF). The purpose of the present investigation was to evaluate if changes in the splanchnic perfusion after revascularization can be detected by measuring the SBF and hepatic vein oxygenation.

MATERIALS AND METHODS

The SBF was measured in 10 patients before and after revascularization of the mesenteric arteries by either percutaneous transluminal angioplasty (n = 9) or open revascularization (n = 1). The SBF was measured indirectly using Fick's principle and using the tracer Tc-99m Mebrofenin along with assessment of hepatic blood oxygenation, before and after a standard meal, following catheterization of a hepatic vein and the femoral artery.

RESULTS

Nine of 10 patients (90%) achieved a profound increase in SBF after revascularization (mean increase in postprandial response to meal stimulation from 71 ± 95 to 531 ± 295 ml/min, p = 0.001), and an increase in postprandial hepatic vein oxygen saturation (from 52 ± 14% to 59 ± 13%, p = 0.006). The symptoms of the patients diminished accordingly. One patient had no symptom relief, and no increase in postprandial SBF, but an angiographic result with no significant stenosis postrevascularization.

CONCLUSIONS

Revascularization increased the SBF and hepatic vein oxygen saturation significantly concurrent with symptom relief and according with the angiographic successful result in the vast majority of patients. A satisfying angiographic result post vascular intervention does not rule out CMI.

Chronic mesenteric ischaemia: the importance of the individual mesenteric artery

BACKGROUND

Chronic mesenteric ischaemia (CMI) is a vastly underdiagnosed condition that typically leads to postprandial abdominal pain and weight loss. The aim of the study was to explore the involvement of various mesenteric vessels in total splanchnic blood flow (SBF) and hepatic vein oxygenation.

METHODS

Single-blinded comparative trial of 476 patients clinically suspected of CMI. Routine investigation included measurement of hepatic vein oxygen saturation, indirect measurement of the total splanchnic blood flow (SBF), using Fick's principle and the tracer [^99m Tc]Mebrofenin, before and after a meal, and digital subtraction angiography.

RESULTS

A total of 176 of the 476 patients (36%) had at least one angiographically significant stenosis (lumen reduction ≥70%). In patients with a significant one-vessel disease, the percentage having CMI according to SBF was 10% for a celiac trunk stenosis (n = 60), 50% for a superior mesenteric stenosis (n = 24) and 6% for an inferior mesenteric artery stenosis (n = 34). In patients with a significant two-vessel disease, the percentage with CMI according to SBF response was 92%, 18% and 79%, for no significant stenosis of the celiac trunk (n = 13), superior mesenteric artery (n = 17) and inferior mesenteric artery (n = 19), respectively.

CONCLUSION

Patients with significant one- or two-vessel stenosis involving the superior mesenteric artery have a higher likelihood of CMI according to flow criteria and a greater postprandial decrease in hepatic vein saturation on average than patients with no involvement of the superior mesenteric artery.

Gastroscopy assisted laser Doppler flowmetry and visible light spectroscopy in patients with chronic mesenteric ischemia

Mucosal pathology due to chronic mesenteric ischemia (CMI) is rarely seen during upper endoscopy. Combining Laser Doppler Flowmetry (LDF) and Visible Light Spectroscopy (VLS) may aid in detection of CMI at an early stage. We aimed to investigate the utility of LDF and VLS in detecting microcirculatory changes in patients with CMI during upper endoscopy. In a single center, prospective study, 104 patients were evaluated for mesenteric ischemia during a 24 months period. Patients with a consensus diagnosis of CMI (n = 40) were examined with LDF and VLS. Thirty-two were successfully treated and had a definitive diagnosis of CMI. Results were compared with controls (n = 38) with normal intestinal circulation evaluated with duplex ultrasonography (DUS). Treatment response was evaluated clinically and with DUS at 1 month and with VLS and LDF at 3 months. A significant reduction in mucosal capillary hemoglobin oxygen saturation (SO₂) was found in CMI patients compared to controls before treatment: mean ± SD: 67 ± 9%, 81 ± 4%, respectively (p < .001). A significant reduction was also seen for the relative hemoglobin (rHb) amount, flow and velocity (p < .001). The sensitivity of SO₂ measured by VLS for diagnosing CMI was 94% and the specificity 72% (cut-off 78%), calculated with ROC curve analysis. A combination of SO₂ and rHb increased the test sensitivity and specificity to 97% and 79%, respectively. Conclusion: CMI patients have significantly reduced microcirculation in the stomach and duodenum compared to controls. The results suggest that VLS should be included when performing an upper endoscopy in patients with suspected CMI.

Functional testing in the diagnosis of chronic mesenteric ischemia

Chronic mesenteric ischemia (CMI) results from insufficient oxygen delivery or utilization to meet metabolic demand. Two main mechanisms may lead to mesenteric ischemia: occlusion in the arteries or veins of the gastrointestinal tract, or reduced blood flow from shock states or increased intra-abdominal pressure, so-called non-occlusive mesenteric ischemia. Severe stenoses in the three main mesenteric vessels as demonstrated with CT-angiography or MR-angiography are sufficient to proof mesenteric ischemia, for example in patients who present with weight loss, postprandial pain and diarrhea. Still in many clinical situations mesenteric ischemia is only one of many possible explanations. Especially in patients with a single vessel stenosis in the celiac artery or superior mesenteric artery with postprandial pain, mesenteric ischemia remains a diagnosis of probability or assumption without functional proof of actual ischemia. This review is aimed to provide an overview of all past, present and future ways to functionally proof CMI.

The influence of the gastrointestinal tract and the liver on cystatin C serum concentrations

OBJECTIVE

The purpose of this study in humans was to examine the influence of the gastrointestinal tract and liver on the serum concentrations of cystatin C.

METHODS

Eighteen healthy volunteers and 28 patients suspected of having chronic intestinal ischemia underwent catheterization of the abdominal aorta and the central hepatic vein. Blood samples were taken simultaneously from the abdominal aorta and the central hepatic vein 60, 90 and 120 minutes after the start of the investigation. After the first blood sample, a standard liquid meal was ingested. Measurement of splanchnic blood flow was performed using the Fick principle with constant infusion of (99m)Tc-Bridatec. Angiography was performed at the end of the investigation.

RESULTS

The splanchnic blood flow increased significantly postprandially in the healthy volunteers and in the patients with normal angiography by 0.613-0.698 L/min and increased non- significantly in the patients with abnormal angiography (n = 5) by 0.135 L/min on average. ANOVA and the Bonferroni's multiple comparison test showed no significant difference between the means of cystatin C, creatinine or urea in the samples taken 60, 90 and 120 minutes after the start of the investigation in the abdominal aorta and the hepatic vein in the healthy volunteers or in the patients suspected of chronic intestinal ischemia with normal angiography.

CONCLUSION

There was no indication of hepatic elimination of cystatin C, creatinine or urea. The serum concentrations of cystatin C, creatinine and urea in the central hepatic vein and the abdominal aorta were independent of the splanchnic blood flow.

Validation of ⁹⁹mTechnetium-labeled mebrofenin hepatic extraction method to quantify meal-induced splanchnic blood flow responses using a porcine model

The aim of this study was to evaluate the measurement of the total splanchnic blood flow (SBF) using a clinical diagnostic method based on Fick's principle and hepatic extraction of 99mTc-mebrofenin (99mTc-MBF) compared with a paraaminohippuric acid (pAH) dilution method in a porcine model. Another aim was to investigate whether enterohepatic cycling of 99mTc-MBF affected the SBF measurement. Five indwelling catheters were placed in each pig (n = 15) in the portal, mesenteric, and hepatic veins, as well as in the aorta and the vena cava. The SBF was measured using both methods. The portal blood flow; the intestinal and hepatic oxygen uptake; the net fluxes of oxygen, lactate, and glucose; and the extraction fraction (EF) of 99mTc-MBF were measured before and for 70 min after feeding. The mean baseline SBF was 2,961 ml/min vs. 2,762 ml/min measured by pAH and 99mTc-MBF, respectively, and increased significantly to 3,977 ml/min and 3,981 ml/min postprandially. The hepatic EF of 99mTc-MBF decreased from 40% at the start of the investigation to 16% 70 min after feeding. The arterial-portal difference in 99mTc-MBF concentration was 0.21% (P = 0.48), indicating no intestinal extraction or metabolism. The clinical method for measuring the SBF based on hepatic 99mTc-MBF extraction is robust compared with the indicator dilution method, despite the decrease seen in hepatic extraction of 99mTc-MBF. Because there was no difference in the content of 99mTc-MBF between the arterial and portal vein plasma, the SBF can be calculated from an arterial and a hepatic vein sample.