Chronic visceral ischemia

The radiologist's guide to duplex ultrasound assessment of chronic mesenteric ischemia

OBJECTIVE

This article reviews the relevant anatomy and physiology of the mesenteric vasculature, familiarizes the radiologist with the accepted diagnostic criteria for mesenteric artery stenosis and its role in the diagnosis of chronic mesenteric ischemia, describes Doppler imaging techniques, and provides protocols for the assessment and surveillance of the mesenteric vasculature before and after revascularization. It also discusses expected changes following revascularization and reviews common post-procedural complications.

RESULTS

Duplex sonography plays an important role in the diagnosis and management of chronic mesenteric ischemia (CMI). Establishing a successful diagnosis is dependent upon knowledge of mesenteric arterial anatomy and physiology as well as sufficient expertise in image optimization and scanning techniques. Although there has been a trend toward utilization of other noninvasive [computed tomographic angiography (CTA), magnetic resonance angiography (MRA), and invasive (digital subtraction angiography (DSA)] imaging modalities for assessment of the mesenteric vasculature, a new era of "imaging wisely" raises legitimate concerns about the effects of ionizing radiation as well as potential effects of CT and MR contrast agents. These concerns are obviated by the use of ultrasound, and recently developed techniques, such as contrast-enhanced ultrasound and vascular applications focused on the evaluation of slow flow, have revealed the vast potential of vascular ultrasound in the evaluation of chronic mesenteric ischemia.

CONCLUSION

Duplex sonography is a cost-effective and powerful tool that can be utilized for the accurate assessment of mesenteric vascular pathology, specifically mesenteric arterial stenosis, and for the evaluation of mesenteric arterial system post revascularization.

Doppler ultrasonography criteria of superior mesenteric artery stenosis

PURPOSE

The techniques mostly used for the diagnosis of superior mesenteric artery (SMA) stenosis are computed tomography angiography (CTA), and magnetic resonance angiography. We aimed to evaluate color-coded Doppler Ultrasonography (CDUS) for the detection of SMA stenoses and to determine Doppler criteria.

METHODS

We identified retrospectively 65 patients with CTA images of SMA stenosis and examined them with CDUS for the Doppler measurement of SMA peak systolic flow velocity (PSV), end-diastolic velocity (EDV), and mesenterico-aortic ratio (MAR). Results were analyzed with receiver-operating characteristic curve analysis.

RESULTS

The optimal threshold values for determining 50%-69% SMA stenoses were PSV >280 cm/s, EDV >45 cm/s, and MAR >3.6. For identifying 70%-99% SMA stenoses, they were PSV >395 cm/s, EDV >74 cm/s, and MAR >3.6.

CONCLUSION

CDUS is a convenient method with high accuracy for identifying SMA stenosis. PSV yielded better results than EDV and MAR.

Transaortc Endarterectomy for Primary Mesenteric Revascularization

The optimal approach to revascularization for chronic mesenteric ischemia has not been firmly established during the past three decades. The present study was undertaken to evaluate the safety and results of primary mesenteric revascularization for chronic mesenteric ischemia by transaortic endarterectomy. A descriptive retrospective analysis of 14 patients who underwent trap-door transaortic endarterectomy for primary mesenteric revascularization was performed. Clinical presentations of the patients included abdominal pain (n = 13) and weight loss (n = 7). All patients underwent preoperative aortography and subsequent elective reconstruction. Demographic features, perioperative, and long-term outcomes were analyzed. The study population consisted of 12 females and two males with a mean age of 67 years. The mean operative duration was 3 hours with an ischemic time of 33 minutes. The initial success rate of mesenteric revascularization was 93%. One early graft failure was salvaged with urgent embolectomy without bowel resection. There was no hospital mortality, but the overall postoperative morbidity rate was 50% (n = 7). Thirteen patients (93%) were discharged within 2 weeks. Late recurrent ischemia and intestinal infarction developed in one patient, requiring emergency bowel resection. Sustained relief of symptoms was achieved in 13 of 14 patients (93%). The overall survival rates were 85% ± 10.0% and 77% ± 11.7% at 1 and 3 years, respectively. Transaortic endarterectomy is a safe and effective technique for elective primary mesenteric revascularization for patients with chronic mesenteric ischemia. This approach allows simultaneous revascularization of multiple visceral arteries and achieves durable relief of symptoms.

Doppler sonographic criteria for the diagnosis of inferior mesenteric artery stenosis

OBJECTIVE

The purpose of this study was to define the optimal Doppler criteria for the diagnosis of inferior mesenteric artery (IMA) stenosis in patients with suspected chronic mesenteric ischemia (CMI).

METHODS

A retrospective review of 205 dedicated color and pulsed Doppler sonographic studies of mesenteric arteries was performed in 205 patients. All studies were performed in patients with suspected CMI. Correlative angiography was available in 50 patients.

RESULTS

The IMA was visualized in 176 of 205 Doppler sonographic examinations (86%) and in 92% of the correlative studies. The visualization rate for the detection of a patent IMA by Doppler sonography in this series was 90%. The ranges of the peak systolic velocity (PSV), end-diastolic velocity (EDV), and mesenteric-aortic velocity ratio (MAR) in the nonstenotic IMA were 70 to 200 cm/s, 0 to 33 cm/s, and 0.7 to 3.7, respectively. The ranges of the PSV, EDV, and MAR in IMA stenosis were 200 to 485 cm/s, 0 to 177 cm/s, and 0.69 to 8.1. The threshold values for severe IMA stenosis by logistic regression analysis (n = 42) were as follows: PSV, greater than 200 cm/s; EDV, greater than 25 cm/s; and MAR, greater than 2.5, with sensitivities of 90%, 40%, and 80%; specificities of 97%, 91%, and 88%; positive predictive values (PPVs) of 90%, 57%, and 67%; negative predictive values (NPVs) of 97%, 83%, and 93%; and accuracy of 95%, 79%, and 86%, respectively.

CONCLUSIONS

We found that a PSV of greater than 200 cm/s was the best criterion for the diagnosis of IMA stenosis. The sensitivity, specificity, PPV, NPV, and accuracy for the PSV were 90%, 97%, 90%, 97%, and 95%, respectively.

Management of chronic mesenteric ischemia. The role of endovascular therapy

Chronic mesenteric ischemia is an uncommon disorder manifested most commonly as abdominal pain. Surgical revascularization has traditionally been the treatment of choice. Endovascular management of this entity was originally attempted as an alternative for high-risk patients. Improvements in stent technology, refinement in technique, and increased efficiency of antiplatelet regimens have, over time, increased the popularity of this minimally invasive approach. We present a review of the available series on endovascular treatment of chronic mesenteric ischemia, with emphasis on short- and long-term outcome and morbidity and mortality results. Principles of operative technique and controversial issues and topics of interest are also discussed.

MR imaging of apparent small-bowel perfusion for diagnosing mesenteric ischemia: feasibility study

The purpose of this study, which was approved by the institutional review board, was to assess the differentiation of individuals with from those without mesenteric ischemia. All subjects provided written informed consent. Six healthy volunteers and six patients with documented chronic mesenteric ischemia underwent magnetic resonance (MR) imaging with and without oral caloric stimulation. After intravenous administration of paramagnetic contrast material, signal intensity values of the small-bowel wall were measured up to 130 seconds after contrast material injection. Volunteers and patients, respectively, had maximum enhancement of the bowel wall between 70 and 85 seconds after contrast material administration that amounted to 269% and 267% without and 425% and 333% with caloric stimulation. MR imaging assessment of small-bowel perfusion is possible and seems feasible for differentiating individuals with from those without mesenteric ischemia.

Evaluation of suspected mesenteric ischemia: efficacy of radiologic studies

Mesenteric ischemia is a common problem with protean causes. In patients with suspected mesenteric ischemia, early recognition of ischemic bowel and prompt management are crucial and directly connected to patients' prognosis. Because of its cross-sectional capability offering direct visualization of both enteric and perienteric changes, CT has become an essential diagnostic tool in these clinical settings. Although imaging features in mesenteric ischemia often are relatively nonspecific, understanding of the pathophysiology and clinical features of this disorder in various conditions, and radiologic findings, help the radiologist recognize the ischemic bowel and arrive at a correct diagnosis.

Asymptomatic chronic intestinal ischemia caused by idiopathic phlebosclerosis of mesenteric vein

Phlebosclerosis of the mesenteric vein is a rare condition causing chronic intestinal ischemia, it has only been reported in Japan. A 56-year-old man with liver cirrhosis and hepatic tumor presented with phlebosclerosis of mesenteric vein without any abdominal symptoms. He was admitted for examination of suspected hepatic tumor. Abdominal plain x-ray films and computed tomography revealed calcification of the mesenteric vein. Barium enema revealed narrowing and thumbprinting from the cecum to transverse colon. On colonoscopic examination, blue-black vessels were visible in the terminal ileum, and hyperemic nodular mucosa with small irregular ulcers surrounded by dark purple mucosa was found from the cecum to transverse colon. The etiology of mesenteric vein phlebosclerosis is unknown, although a physical mechanism rather than inflammatory changes appear to be involved in this rare and usually progressive condition of chronic intestinal ischemia.

Radiologic diagnosis and treatment of gastrointestinal hemorrhage and ischemia

Major breakthroughs in catheter, guidewire, and other angiographic equipment currently allow interventional radiologists to diagnose massive life-threatening upper and lower GI hemorrhage and to stop the bleeding safely and effectively using superselective catheterization and microcoil embolization. Similarly, the interventional radiologist can treat acute intestinal ischemia safely and effectively with selective catheterization and papaverine administration and treat chronic mesenteric ischemia by percutaneous angioplasty and stent placement. A multidisciplinary approach, including the gastroenterologist, radiologist, and surgeon, is critical in managing GI bleeding and intestinal ischemia, particularly in patients at high risk or presenting as diagnostic dilemmas.

Drug therapies for mesenteric vascular disease

Mesenteric vascular disease has been increasingly diagnosed in the past 25 years. This rise in incidence has been attributed to the advanced mean age of the population and increasing number of critically ill patients, and to a greater clinical recognition of the condition. While surgical revascularization and resection has long been the standard of treatment, medical management also plays an important role. Early diagnosis before irreversible bowel damage, which may occur within 6 to 8 hours after insult, is the goal of successful medical treatment without surgical intervention. Even in the presence or irreversible bowel ischemia, perioperative medical treatment may reduce the progression of further ischemia, and bowel resection may be limited. This article outlines the appropriate medical management of ischemic disorders of the intestine, with an emphasis on the drug treatments presently used in clinical practice and those being studied in the laboratory.

In vivo flow-independent T2 measurements of superior mesenteric vein blood in diagnosis of chronic mesenteric ischemia: a preliminary evaluation

RATIONALE AND OBJECTIVES

The authors attempted to determine whether the T2 relaxation time of superior mesenteric vein (SMV) blood would decrease in patients with chronic mesenteric ischemia after a meal.

MATERIALS AND METHODS

Thirty-two patients without chronic mesenteric ischemia and eight patients with symptomatic chronic mesenteric ischemia underwent magnetic resonance (MR) imaging. All examinations were performed with a 1.5-T unit, a modified Carr-Purcell-Meiboom-Gill sequence, final section-selective pulse of 180 degrees, and spiral readout gradients. Measurements of SMV blood T2 were obtained after at least 6 hours of fasting and 15 and 35 minutes after ingestion of 240 mL of a liquid nutritional supplement. Maximal change of the SMV blood T2 was expressed as a percentage of the fasting T2 in all patients.

RESULTS

In control patients, SMV blood T2 increased postprandially by 9.4% +/- 1.3 (95% confidence level; range, 6.8%-11.9%) (data range, -7.3% to 25.6%) compared with fasting T2. In symptomatic patients, SMV blood T2 decreased postprandially by 15.8% +/- 2.2 (95% confidence level; range, -20.1% to -10.7%) (data range, -7.9% to -25.3%). The difference between the two groups was statistically significant (P < .0001 by Student unpaired t test).

CONCLUSION

Measurement of SMV blood T2 is a promising test for chronic mesenteric ischemia diagnosis. Therefore, conversion of T2 measurements to estimate oxygen saturation may not be necessary for all cases of this clinical indication.

Splanchnic arterial stenosis or occlusion: diagnosis at Doppler US

PURPOSE

To determine the diagnostic accuracy of Doppler ultrasonography (US) in the detection of high-grade stenosis or occlusion of the celiac artery (CA) and superior mesenteric artery (SMA) and validate the previously reported Doppler US criteria.

MATERIALS AND METHODS

During a recent 36-month period, 82 patients were prospectively examined with Doppler US of the splanchnic arteries and with lateral abdominal aortography, regardless of their abdominal symptoms. The previously reported diagnostic criteria with the fasting peak systolic velocity measurement were prospectively used in all patients. The results of Doppler US were compared with those of lateral aortography.

RESULTS

The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of Doppler US for the detection of 70% or greater CA stenosis or occlusion were 100%, 87%, 57%, 100%, and 89%, respectively; for 70% or greater SMA stenosis or occlusion, these values were 100%, 98%, 93%, 100%, and 99%, respectively.

CONCLUSION

Owing to its high accuracy in the diagnosis of high-grade splanchnic arterial stenosis or occlusion, Doppler US can be used as a screening method to help detect CA or SMA stenosis or occlusion and can reduce the use of unnecessary, invasive angiography.

Intestinal (mesenteric) vasculopathy. II. Ischemic colitis and chronic mesenteric ischemia

Ischemic colitis accounts for approximately half of all cases of mesenteric vasculopathy. The clinical presentation varies depending on underlying cause, extent of vascular obstruction, rapidity of ischemic insult, degree of collateral circulation, and presence of comorbidity. Ischemic colitis is usually diagnosed by colonoscopy. Only approximately 20% of patients require surgery because of signs or laboratory findings of peritonitis or because of clinical deterioration. Approximately 20% of patients develop chronic colitis from irreversible colonic ischemic injury, which manifests clinically as persistent diarrhea, rectal bleeding, or weight loss and endoscopically as a colonic stricture or mass. Chronic mesenteric ischemia is almost always caused by significant atherosclerotic stenosis involving at least two mesenteric arteries, usually the superior mesenteric artery and celiac axis. The classic symptomatic triad of postprandial pain, fear of eating, and involuntary weight loss occurs with advanced disease.

Reoperation for recurrent chronic visceral ischemia

PURPOSE

Recurrent visceral ischemia after a failed visceral revascularization occurs in up to one third of patients, yet no comprehensive report has described the management of this problem. The purpose of this study was to examine the presentation, surgical management, and outcome of patients with recurrent visceral ischemia.

METHODS

Between 1959 and 1997, 109 patients underwent primary visceral revascularization at the University of California, San Francisco. Nineteen patients (17.4%) had recurrent visceral ischemia (12 chronic visceral ischemia, seven acute visceral ischemia). Fourteen additional patients with recurrent chronic visceral ischemia were referred after failed primary revascularization (two patients underwent multiple operations before referral). Thirty visceral reoperations were performed for recurrent visceral ischemia in 24 patients (10 patients with recurrence at University of California, San Francisco, 14 referred patients). Symptom-free and overall survival rates were determined by life table analysis.

RESULTS

Of seven patients (6.4%) who had recurrent acute visceral ischemia, six (85.7%) died of bowel infarction. Twelve patients (11%) had recurrent chronic visceral ischemia. Patients with recurrent chronic visceral ischemia received their diagnoses earlier and lost less weight than at their initial presentation (p = 0.004 and 0.001, respectively). Recurrent ischemia was associated with younger age, greater weight loss, and modification of surgical technique at the time of initial operation (p = 0.5, 0.009, and 0.02, respectively). For 20 (90.9%) of the 22 first reoperations, antegrade aortovisceral bypass (n = 10) or transaortic visceral endarterectomy (n = 10) was used. Multiple techniques (four antegrade bypass, two retrograde bypass, one endarterectomy, one anastomotic revision) were used in the eight second or third reoperations. Postoperative mortality and complication rates were 6.7% and 33.3%, respectively. Symptoms recurred in six of 22 patients (27.3%) after the first reoperation, three of whom were cured or improved after additional reoperations. The life table symptom-free survival rate after reoperation was 77.3% and 62.8% at 1 and 5 years, respectively. The life table overall survival rate after reoperation was 74.6% at 5 years.

CONCLUSIONS

Recurrent visceral ischemia is not uncommon after primary visceral revascularization. These results show that reoperation for recurrent chronic visceral ischemia can be accomplished safely and effectively with established revascularization techniques. Furthermore, after repeat visceral revascularization patients achieve durable relief of symptoms and have life expectancy rates comparable with those of patients who undergo primary visceral revascularization.

Bypass grafting for chronic mesenteric ischemia

A critical analysis of the literature suggests that there is no clearly superior technique for mesenteric revascularization and that the choice of operation must be individualized. Bypass grafting using either an antegrade or retrograde technique with prosthetic or autogenous conduits should produce excellent long-term results for most patients with this complex surgical problem. In most situations multiple vessel revascularizations are preferred. Surgeons caring for such patients must have the ability to utilize all available techniques to ensure optimal outcomes.

MR angiography of abdominal ischemia

Advances during the past decade in MRI have made this modality increasingly suitable for evaluating abdominal vascular diseases. Preliminary results in canine models and humans suggest that MRI has the potential of becoming a definitive, noninvasive test for the diagnosis of both acute and chronic mesenteric ischemia. MRI can provide both morphological information about the patency or degree of stenosis in mesenteric vessels as well as quantitative functional information such as blood flow and blood oxygen saturation in these vessels. The MR techniques developed for studying the mesenteric circulation also can be used for improving the diagnosis and posttreatment evaluation of vascular diseases in other abdominal organ systems.