CT of acute bowel ischemia

Utility of arterial phase of dynamic CT for detection of intestinal ischemia associated with strangulation ileus

AIM: To clarify the usefulness of arterial phase scans in contrast computed tomography (CT) imaging of strangulation ileus in order to make an early diagnosis.

METHODS: A comparative examination was carried out with respect to the CT value of the intestinal tract wall in each scanning phase, the CT value of the content in the intestinal tract, and the CT value of ascites fluid in the portal vein phase for a group in which ischemia was observed (Group I) and a group in which ischemia was not observed (Group N) based on the pathological findings or intra-surgical findings. Moreover, a comparative examination was carried out in Group I subjects for each scanning phase with respect to average differences in the CT values of the intestinal tract wall where ischemia was suspected and in the intestinal tract wall in non-ischemic areas.

RESULTS: There were 15 subjects in Group I and 30 subjects in Group N. The CT value of the intestinal tract wall was 41.8 ± 11.2 Hounsfield Unit (HU) in Group I and 69.6 ± 18.4 HU in Group N in the arterial phase, with the CT value of the ischemic bowel wall being significantly lower in Group I. In the portal vein phase, the CT value of the ischemic bowel wall was 60.6 ± 14.6 HU in Group I and 80.7 ± 17.7 HU in Group N, with the CT value of the ischemic bowel wall being significantly lower in Group I; however, no significant differences were observed in the equilibrium phase. The CT value of the solution in the intestine was 18.6 ± 9.5 HU in Group I and 10.4 ± 5.1 HU in Group N, being significantly higher in Group I. No significant differences were observed in the CT value of the accumulation of ascites fluid. The average difference in the CT values between the ischemic bowel wall and the non-ischemic bowel wall for each subject in Group I was 33.7 ± 20.1 HU in the arterial phase, being significantly larger compared to the other two phases.

CONCLUSION: This is a retrospective study using a small number of subjects; however, it suggests that there is a possibility that CT scanning in the arterial phase is useful for the early diagnosis of strangulation ileus.

Extensive colonic necrosis following cardiac arrest and successful cardiopulmonary resuscitation: report of a case and literature review

Non-occlusive colonic ischaemia is a recognized albeit rare entity related to low blood flow within the visceral circulation and in most reported cases the right colon was affected. This is the second case report in the literature of extensive colonic necrosis following cardiac arrest and cardiopulmonary resuscitation (CPR). A 83-year-old Caucasian woman was admitted to our hospital due to a low energy hip fracture. On her way to the radiology department she sustained a cardiac arrest. CPR started immediately and was successful. A few hours later, the patient developed increasing abdominal distension and severe metabolic acidocis. An abdominal multidetector computed tomography (MDCT) scan was suggestive of intestinal ischaemia. At laparotomy, the terminal ileum was ischaemic and extensive colonic necrosis was found, sparing only the proximal third of the transverse colon. The rectum was also spared. The terminal ileum and the entire colon were resected and an end ileostomy was fashioned. Although the patient exhibited a transient improvement during the immediate postoperative period, she eventually died 24h later from multiple organ failure. Histology showed transmural colonic necrosis with no evidence of a thromboembolic process or vasculitis. Therefore, this entity was attributed to a low flow state within the intestinal circulation secondary to the cardiac arrest.

Evaluation of the utility of abdominal CT scans in the diagnosis, management, outcome and information given at discharge of patients with non-traumatic acute abdominal pain

OBJECTIVES

The role of CT imaging in the diagnosis and management of acute abdominal pain is well established, but its utility is limited in a minority of cases. The aim of this study was to quantify the degree to which radiological and clinical findings differ. Interobserver variability in CT reporting was also assessed.

METHODS

Clinical data and CT reports were analysed retrospectively for any discrepancies by comparing CT diagnosis, clinical diagnosis as stated on the discharge summary and final diagnosis (based on consensus review of all information). Blinded review of all CT imaging was performed to determine interobserver variability.

RESULTS

120 consecutive scans fulfilled the inclusion criteria (114 patients; 79 women; mean age 55 years). The correct clinical diagnosis was made in 87.5% of cases based on CT findings. The lack of intravenous contrast limited diagnostic interpretation in 6 of the 15 discrepant cases. CT was unable to define early inflammatory changes in three patients and early caecal carcinoma in one. A right paraduodenal internal hernia was difficult to detect in another patient. Interobserver agreement was 93%, but with a low kappa value of 0.27. A paradox exists due to an imbalance in the positive and negative agreement of 96% and 31%, respectively.

CONCLUSIONS

The utility of CT imaging in the diagnosis and management of patients presenting with acute abdominal pain is confirmed, but is limited in a minority of cases where poor negative interobserver agreement exists. Good communication to the reporting radiologist of the relevant patient history and clinical question becomes important.

7T μMRI of mesenteric venous ischemia in a rat model: timing of the appearance of findings

OBJECTIVES

The aim of this study is to analyze the chronological development of macroscopic, microscopic and magnetic resonance imaging (MRI) findings in a rat model of Superior Mesenteric Venous (SMV) ligation, and to evaluate the role of MRI in the diagnosis of mesenteric venous thrombosis.

METHODS

Thirty adult Sprague-Dawley rats were used and divided in two different groups that underwent a different surgical model and a different monitoring of ischemic damage. Group I underwent macroscopical and histological observation; Group II underwent 7T μMRI evaluation and histological analysis.

RESULTS

The first alterations occurred 30 min after SMV ligation and progressively worsened until the eighth hour. The morphological and MRI findings showed the same course.

CONCLUSIONS

This study provides a systematic evaluation of early anatomopathological and MRI findings following the SMV ligation. MRI allows to identify the early pathological findings of venous mesenteric ischemia and allows to correlate those to the histopathological features. Our data suggest a relevant role of MRI in the diagnostic management of mesenteric venous thrombosis, allowing to non-invasively identify and characterize the histopathologic findings. So, thanks to these skills, its future application in early diagnosis of human mesenteric venous ischemia is supposable.

Ischemic colitis and large bowel infarction: A case report

Ischemic bowel disease results from an acute or chronic drop in the blood supply to the bowel and may have various clinical presentations, such as intestinal angina, ischemic colitis or intestinal infarction. Elderly patients with systemic atherosclerosis who are symptomatic for the disease in two or more vascular beds have multiple comorbidities and are particularly at risk. The clinical evolution and outcome of this disease are difficult to predict because of its pleomorphic aspects and the general lack of statistical data. In this paper, we present the case of a patient who was monitored in our unit for six years. For this patient, we encountered iterative changes in the clinical pattern, beginning with chronic “intestinal angina” and finishing with signs of acute mesenteric ischemia after an episode of ischemic colitis. This evolution is particularly rare in clinical practice, and the case is instructive because it raises discussions about the natural history of the condition and the therapeutic decisions that should be made at every stage of the disease. An important lesson is that ischemic bowel disease should always be considered in patients who have multiple risk factors for atherosclerosis and have experienced recurrent “indistinct” abdominal symptoms. In these cases, aggressive investigation and therapeutic decisions must be taken whenever possible. Despite an absence of standardized protocols, angiographic evaluation and revascularization procedures have beneficial outcomes. Current advances in endovascular therapy, such as percutaneous transluminal angioplasty with stenting, should be increasingly used in patients with chronic mesenteric ischemia. Such therapy can avoid the risks that are associated with open repair. However, technical difficulties, especially in severe stenotic lesions, frequently occur.

Acute bowel ischemia: analysis of diagnostic error by overlooked findings at MDCT angiography

To retrospectively evaluate the frequency and type of findings that were missed in the original reports of multi-detector CT angiography (MDCTA) in patients with suspected acute bowel ischemia. From January 2007 to March 2011, a series of 35 patients who underwent MDCTA of the abdomen and pelvis and had surgery were included. The reports of the initial CT were retrospectively compared with the discharge diagnosis and surgical reports. Discrepant or missing findings were re-evaluated and divided into relevant or not relevant regarding the diagnosis. In 23 of the 35 patients (66 %), all findings were correctly diagnosed in the initial MDCTA report. In the remaining 12 of the 35 patients (34 %), lesions that were not reported were present at surgery. In 10 of the 12 (83 %) patients, the overlooked findings were relevant and subtle: gas in the portal vein (n = 3), gas in the bowel wall (n = 3), gas in the portal vein and bowel wall (n = 2), thrombotic occlusion of the superior mesenteric artery (n = 1), and thrombotic occlusion of the inferior mesenteric artery (n = 1). In 2 of the 12 (17 %) patients in whom the MDCTA-overlooked findings were classified as non-relevant, bowel ischemia was found at surgery. With retrospective image interpretation, 83 % of the patients with occlusive mesenteric ischemia at surgery were correctly identified, whereas the remaining 17 % with non-occlusive mesenteric ischemia at surgery showed non-relevant findings at MDCTA. About 33 % of relevant findings of bowel ischemia were overlooked by the initial MDCTA interpretation, most were subtle findings. However, secondary reading revealed most of these findings and can serve to improve diagnostic performance.

CT findings of small bowel strangulation: the importance of contrast enhancement

The purpose of this study is to illustrate computed tomography (CT) findings suggestive of small bowel strangulation. We have performed the precontrast and postcontrast CT with single and multidetector CT scanners and evaluated the bowel wall changes and mesentery changes and correlated them with the operative findings. The direct CT findings suggestive of small bowel strangulation included high-density bowel wall on precontrast scans; lack of, or diminished contrast enhancement of the involved bowel wall; localized mesenteric fluid accumulation (mesenteric congestion); and localized pneumatosis. The indirect CT signs included C- or U-shaped loops with mesenteric vessels converging toward the obstruction site, ascites, target sign, two adjacent collapsed round loops, and whirl sign. We particularly emphasize the importance of contrast enhancement of bowel mucosa for early diagnosis to differentiate strangulation from a mechanical obstruction without bowel ischemia, and also the importance to differentiate proximal secondary gas-filled dilated small bowel loops from distal primary involved fluid-filled small bowel loops because these two types of small bowel loops are present in the single peritoneal cavity. As early recognition of small bowel strangulation may help improve the patient outcome because the involved bowel loops can be preserved without resection, it is essential to become familiar with the CT signs suggested small bowel obstruction strangulation.

CT enterography: review of technique and practical tips

CT enterography is a new non-invasive imaging technique that offers superior small bowel visualisation compared with standard abdomino-pelvic CT, and provides complementary diagnostic information to capsule endoscopy and MRI enterography. CT enterography is well tolerated by patients and enables accurate, efficient assessment of pathology arising from the small bowel wall or surrounding organs. This article reviews the clinical role of CT enterography, and offers practical tips for optimising technique and accurate interpretation.

Management of hepatic vascular diseases

Primary damage to hepatic vessels is rare. (i) Hepatic arterial disorders, related mostly to iatrogenic injury and occasionally to systemic diseases, lead to ischemic cholangiopathy. (ii) Hepatic vein or inferior vena cava thrombosis, causing primary Budd-Chiari syndrome, is related typically to a combination of underlying prothrombotic conditions, particularly myeloproliferative neoplasms, factor V Leiden, and oral contraceptive use. The outcome of Budd-Chiari syndrome has markedly improved with anticoagulation therapy and, when needed, angioplasty, stenting, TIPS, or liver transplantation. (iii) Extrahepatic portal vein thrombosis is related to local causes (advanced cirrhosis, surgery, malignant or inflammatory conditions), or general prothrombotic conditions (mostly myeloproliferative neoplasms or factor II gene mutation), often in combination. Anticoagulation at the early stage prevents thrombus extension and, in 40% of the cases, allows for recanalization. At the late stage, gastrointestinal bleeding related to portal hypertension can be prevented in the same way as in cirrhosis. (iv) Sinusoidal obstruction syndrome (or venoocclusive disease), caused by agents toxic to bone marrow progenitors and to sinusoidal endothelial cells, induces portal hypertension and liver dysfunction. Decreasing the intensity of myeloablative regimens reduces the incidence of sinusoidal toxicity. (v) Obstruction of intrahepatic portal veins (obliterative portal venopathy) can be associated with autoimmune diseases, prothrombotic conditions, or HIV infection. The disease can eventually be complicated with end-stage liver disease. Extrahepatic portal vein obstruction is common. Anticoagulation should be considered. (vi) Nodular regenerative hyperplasia is induced by the uneven perfusion due to obstructed sinusoids, or portal or hepatic venules. It causes pure portal hypertension.

Computed tomographic evaluation of mesentery: diagnostic value in acute mesenteric ischemia

OBJECTIVE

To evaluate the computed tomographic appearances of mesentery in acute mesenteric ischemia (AMI) to recognize characteristic features and their prognostic values.

METHODS

Computed tomographic examinations of 34 patients with a confirmed diagnosis of AMI were retrospectively reviewed to evaluate the number of mesenteric vessels, diameter of the superior mesenteric artery and superior mesenteric vein, mesenteric fat stranding, mesenteric vessel pneumatosis and ascites.

RESULTS

Overall, at least one of these mesenteric signs was present in all but 1 patient. In all AMI of arterial occlusive type and in 68% of nonocclusive mesenteric ischemia, the number of arterial vessels was reduced (P = 0.067). Mesenteric vessel pneumatosis and reduced number of venous vessels were significantly associated with higher mortality (P = 0.027 and P = 0.042, respectively). Reperfusion signs were associated with a reduced mortality (28.7% vs 65.5%).

CONCLUSION

Considering its characteristic features and its possible prognostic value, the evaluation of mesentery will supply additional information in the interpretation of computed tomography in AMI.

Hepatic gas: widening spectrum of causes detected at CT and US in the interventional era

The spectrum of causes of hepatic gas detected at computed tomography (CT) and ultrasonography (US) is widening. There are many iatrogenic and noniatrogenic causes of hepatic parenchymal, biliary, hepatic venous, and portal venous gas. Hepatic gas may be an indicator of serious acute disease (infarct, infection, abscess, bowel inflammation, or trauma). In other clinical scenarios, it may be an expected finding related to therapeutic interventions (such as surgery; hepatic artery embolization for a tumor or for active bleeding in acute trauma cases; percutaneous tumor ablation performed with radiofrequency, cryotherapy, laser photocoagulation, or ethanol). In some cases, hepatic gas is an incidental finding of no clinical significance. Familiarity with the expanding list of newer intervention-related causes of hepatic gas detected at CT and US, knowledge of the patient's clinical history, and a careful search for associated clues on images are all factors that may allow the radiologist to better determine the clinical relevance of this finding.

Transmural colonic ischemia: clinical features and computed tomography findings

Our purpose was to describe the computed tomography features of transmural colonic ischemia in correlation with clinical, laboratory and histopathological findings of 14 patients who underwent colectomy (9 female and 5 male; mean age, 68 years). Seven patients died (50%). Transmural necrosis involved the right colon in 10 patients (10/14, or 72%). Eleven patients showed thickened colonic wall (11/14, or 79%), 10 pneumatosis (10/14, or 71%), 5 gas in the portal venous system (5/14, or 36%), and 14 fat stranding (14/14, or 100%).

Role of multidetector CT angiography in the evaluation of suspected mesenteric ischemia

OBJECTIVE

To assess the role of multidetector CT angiography (MDCTA) in the diagnosis of acute mesenteric ischemia (AMI) and to compare the diagnostic utility of axial images with reconstructed images.

MATERIALS AND METHODS

In this Institute Review Board approved prospective study, MDCTA was performed on 31 patients who presented with the clinical suspicion of AMI (25M; 6F, age range: 16-73 years). Axial and reconstructed images of each patient were evaluated independently by two radiologists for evidence of bowel wall thickening, abnormal mucosal enhancement, bowel dilatation or obstruction, mesenteric stranding, ascites, solid organ infarcts, pneumatosis intestinalis or porto-mesenteric gas, and mesenteric arterial or venous occlusion. MDCT findings were correlated with the surgical findings and clinical outcome. Patients were later divided into two groups: a study group of patients with proven AMI and a control group of patients with an alternate diagnosis, for the purpose of statistical analysis.

RESULTS

AMI was correctly diagnosed in all 16 patients on MDCTA (100% sensitivity and specificity) of whom nine patients underwent surgical exploration. Three patients expired before surgery and the remaining 5 patients were proven based on positive clinical and laboratory findings. Mesenteric arterial occlusion was seen in 7 patients while 5 patients had portomesenteric venous thrombosis. Reconstructed images using minimum intensity projection, volume rendering and multiplanar volume reconstruction were found to perform better for the detection of vascular abnormalities and improved the diagnostic confidence of both radiologists in the evaluation of bowel and mesenteric abnormalities.

CONCLUSION

MDCTA is an effective non-invasive modality for the diagnosis of mesenteric ischemia.

Radiologists' performance in the diagnosis of acute intestinal ischemia, using MDCT and specific CT findings, using a variety of CT protocols

The aim of this study was to evaluate the performance of radiologists in the diagnosis of acute intestinal ischemia using specific multi-detector CT findings. The abdominal CT scans of 90 patients were retrospectively reviewed by three radiologists: an abdominal imaging specialist, an experienced general radiologist, and a senior resident. Forty-seven patients had surgically proven intestinal ischemia and comprised the case group, while 43 patients had no evidence of intestinal ischemia at surgery and comprised the control group. Images were reviewed in a random and blinded fashion. Radiologists' performance in diagnosing bowel ischemia from other bowel pathologies was evaluated. The sensitivity, specificity, and accuracy for diagnosing bowel ischemia were 89%, 67%, and 79% for the abdominal imager; 83%, 67%, and 76% for the general radiologist; and 66%, 83%, and 74% for the senior resident, respectively. The calculated kappa value for inter-observer agreement regarding the presence of bowel ischemia was 0.79. CT findings that significantly distinguished bowel ischemia from other bowel pathologies were decreased or absent bowel wall enhancement, filling defect in the superior mesenteric artery, small bowel pneumatosis, and gas in the portal veins or superior mesenteric vein. For most of these signs, there was good inter-observer agreement. Radiologists' performance in diagnosing bowel ischemia is good, but lower than previously reported since a significant amount of cases are evaluated using a suboptimal CT technique. Radiologists' experience and expertise have an important impact on their performance.

Seven-Tesla micro-MRI in early detection of acute arterial ischaemia: evolution of findings in an in vivo rat model

PURPOSE

Acute mesenteric ischaemia (AMI) is a life-threatening vascular emergency with a high mortality rate. Early diagnosis is the key to reducing its mortality rate and improving the quality of life. Although computed tomography (CT) is still the gold standard for acute intestinal disorders, over the last few years, magnetic resonance imaging (MRI) has become a useful alternative tool. An animal model of AMI was developed in order to study the effectiveness of MRI in early detection of this condition and to observe lesion evolution.

METHODS

Thirty Sprague Dawley rats were randomly divided into two groups (n=15): in the first group, after laparotomy, the animals underwent ligation of the superior mesenteric artery (SMA), followed by macroscopic monitoring and histological evaluation; in the second, ischaemia was induced by squeezing a loop around the SMA 3 days before evaluation with 7-T micro-MRI.

RESULTS

Macroscopically, a reflex spastic ileus followed by reflex hypotonic ileus and colour changes in some of the loops were detected. MRI evidenced luminal dilatation with air-fluid levels, free intraperitoneal fluid and bowelwall oedema. Histological analysis confirmed ischaemia and earlier damage involving the central portion of the ileum.

CONCLUSIONS

This model shows the correct sequence of events during arterial AMI and demonstrates that MRI can be recommended for early diagnosis of these lesions.

[Diagnosis and management of acute mesenteric ischemia]

The prevalence of significant splanchnic arterial stenoses is increasing, but remains mostly asymptomatic due to abundant collateral circulation. Acute insufficiency of mesenteric arterial blood flow accounts for 60 to 70% of cases of mesenteric ischemia and results mostly from a superior mesenteric embolus. Despite major advances have been achieved in understanding the pathogenic mechanisms of bowel ischemia, its prognosis remains dismal with mortality rates about 60%. The diagnosis of acute mesenteric ischemia depends upon a high clinical suspicion, especially in patients with known risk factors. Rapid diagnosis is essential to prevent intestinal infarction. However, early signs and symptoms of mesenteric ischemia are non specific, and definitive diagnosis often requires radiologic examinations. Early and liberal implementation of angiography has been the major advance over the past 30 years which allowed increasing diagnostic accuracy of acute mesenteric ischemia. CT and MR-based angiographic techniques have emerged as alternatives less invasive and more accurate to analyse splanchnic vessels and evaluate bowel infarction. The goal of treatment of patients with acute mesenteric ischemia is to restore intestinal oxygenation as quickly as possible after initial management that includes rapid hemodynamic monitoring and support. Surgery should not be delayed in patients suspected of having intestinal necrosis.

CT enterography: principles, trends, and interpretation of findings

Computed tomographic (CT) enterography is an emerging alternative to traditional fluoroscopy for the assessment of disorders of the small bowel. The greatly improved spatial and temporal resolution provided by multidetector CT scanners, combined with good luminal distention provided by negative oral contrast agents and with good bowel wall visualization, have made CT enterography the main imaging modality not only for investigating proved or suspected inflammatory bowel disease but also for detecting occult gastrointestinal tract bleeding, small bowel neoplasms, and mesenteric ischemia. CT enterography is particularly useful for differentiating between active and fibrotic bowel strictures in patients with Crohn disease, thus enabling selection of the most appropriate treatment (medical management or intervention) for an improved outcome. CT enterography allows excellent visualization of the entire thickness of the bowel wall and depicts extraenteric involvement as well, providing more detailed and comprehensive information about the extent and severity of the disease process.

Multidetector CT imaging in mesenteric ischemia--pearls and pitfalls

Mesenteric ischemia is a complex and devastating disease which still remains a diagnostic challenge to the clinicians due to non-specific clinical and laboratory findings. Several imaging features have been described with multidetector computed tomography which allows the diagnosis of mesenteric ischemia with high sensitivity and specificity. However, there are imaging features which overlap with other pathologies including benign inflammation and infection. Knowledge of imaging findings in mesenteric ischemia and its potential mimics is important in early and definitive diagnosis.

Pathophysiology of acute small bowel disease with CT correlation

The objective of this article is to review the pathophysiology of acute small bowel diseases, and to correlate the mechanisms of disease with computed tomography (CT) findings. Disease entities will be classified into the following: immune mediated and infectious causes, vascular causes, mechanical causes, trauma, and others. Having an understanding of acute small bowel pathophysiology is a useful teaching tool, and can lead to imaging clues to the most likely diagnosis of acute small bowel disorders.

Acute and chronic mesenteric ischemia: MDCT findings

Mesenteric ischemia is caused by a reduction in mesenteric blood flow. It can be divided into acute and chronic, based upon the rapidity and the degree to which the blood flow is compromised. The authors retrospectively reviewed 22 cases of mesenteric ischemia, diagnosed by multidetector computed tomography (MDCT) in our service, and confirmed by surgery or clinical follow-up. The frequency of the diagnostic findings of chronic and acute mesenteric ischemia was evaluated. The improvement of three-dimensional (3D) MDCT allows accurate assessment of mesenteric vessels. Therefore, it demonstrates changes in ischemic bowel segments helpful in determining the primary cause of the disease, and can identify the complications in patients with acute and chronic mesenteric ischemia.

Value of multislice computed tomography in the diagnosis of acute mesenteric ischemia

OBJECTIVE

To define the value of multislice computed tomography (CT) in the diagnosis of acute mesenteric ischemia (AMI).

MATERIALS AND METHODS

Two hundred patients (age range: 20-92 years) who were referred to the emergency CT department with a clinical suspicion of AMI were prospectively included in the study. CT examinations were performed with a multislice (16) CT scanner and the protocol included pre-contrast, arterial and venous phase acquisitions. Images were evaluated by using multiplanar reconstruction, maximum intensity projection and volume-rendering techniques at the CT workstation.

RESULTS

Ninety-four patients (47%) underwent surgery for AMI or for other causes of acute abdominal pain. One hundred-six patients (53%) were followed conservatively according to clinical, radiologic and laboratory findings. Of the 94 patients who underwent surgery, 49 (25%) were found to have AMI. All of these 49 patients with a proven AMI diagnosis were diagnosed with CT. In the other 45 patients who underwent surgery, CT findings were negative for AMI. None of the patients, who were followed conservatively, were eventually diagnosed as having AMI except 1 patient. This patient was unfit for surgery although his clinical and radiologic findings were consistent with AMI and died in 3 days. The sensitivity and specificity values of CT for the detection of AMI were calculated to be 100% for each.

CONCLUSIONS

Multislice CT is an effective imaging technique for the diagnosis of AMI with excellent sensitivity and specificity values.

Hepatic portal venous gas: a case report and review of literature

Hepatic portal venous gas (HPVG) results from mesenteric ischemia and a wide variety of other causes. The primary factors that favour the development of this pathologic entity are intestinal wall alterations, bowel distension, and sepsis. Findings of HPVG during an ultrasound or computed tomography (CT) scan should be carefully evaluated in the context of the clinical picture. In the absence of features of bowel ischemia, the prognosis of patients with HPVG is usually good.

Diagnostic performance of CT in the detection of intestinal ischemia associated with small-bowel obstruction using maximal attenuation of region of interest

OBJECTIVE

The purpose of this study was to assess the diagnostic performance of CT in the detection of intestinal ischemia associated with small-bowel obstruction using the maximal attenuation of a region of interest (ROI).

MATERIALS AND METHODS

Abdominal CT scans of 60 patients with small-bowel obstruction were retrospectively reviewed. The reference standard of the clinicopathologic groups was classified into four categories: no bowel necrosis, mucosal-submucosal necrosis, superficial muscle necrosis, and transmural necrosis. The viability of the small bowel on CT was evaluated by visual assessment using five categories (i.e., definitely intestinal ischemia, probably intestinal ischemia, possibly intestinal ischemia, equivocal CT results, and no intestinal ischemia) and by measurement of the maximal attenuation of an ROI at selected obstructed small-bowel loops on contrast-enhanced and unenhanced CT scans. Diagnostic performances were evaluated by one-way analysis of variance and receiver operating characteristic (ROC) curve analysis.

RESULTS

The sensitivity, specificity, positive and negative predictive values, and accuracy of visual assessment for intestinal ischemia were 91.7% (33/36), 66.7% (16/24), 80.5% (33/41), 84.2% (16/19), and 81.7% (49/60), respectively. The maximal attenuation of the ROIs on contrast-enhanced CT and the subtraction value between the maximal attenuation on contrast-enhanced CT and that on unenhanced CT scans at selected bowel were significantly different according to clinicopathologic group (p < 0.001). The area under the ROC curve of the maximal attenuation subtraction values between contrast-enhanced and unenhanced CT scans (0.995) was higher than that of visual assessment (0.908) for the detection of intestinal ischemia.

CONCLUSION

The quantification of bowel wall enhancement using the maximal attenuation of an ROI was a reliable and useful method for the diagnosis of intestinal ischemia and showed good correlation with pathology results.

[Diagnostics of vascular diseases as a cause for acute abdomen]

Vascular pathologies are rare causes of an acute abdomen. If the cause is a vascular disease a rapid diagnosis is desired as vascular pathologies are associated with high mortality. A differentiation must be made between arterial and venous diseases. An occlusion of the superior mesenteric artery is the most common reason for acute mesenteric ischemia but intra-abdominal arterial bleeding is also of great importance. Venous pathologies include thrombotic occlusion of the portal vein, the mesenteric vein and the vena cava.Multi-detector computed tomography (MDCT) is predestined for the diagnostics of vascular diseases of the abdomen. Using multiphasic contrast protocols enables reliable imaging of the arterial and venous vessel tree and detection of disorders with high sensitivity and specificity. Although conventional angiography has been almost completely replaced by MDCT as a diagnostic tool, it is still of high importance for minimally invasive interventions, for example in the management of gastrointestinal bleeding.

Spectrum of CT findings in patients with atrial fibrillation and nontraumatic acute abdomen

OBJECTIVE

The purpose of our study was to review the wide spectrum of pertinent CT findings in patients with acute nontraumatic abdominal pain in the setting of atrial fibrillation.

CONCLUSION

Underlying embolic or hemorrhagic complications are common in patients with acute nontraumatic abdominal pain in the setting of atrial fibrillation and can be accurately seen on CT.

Hepatic portal venous gas: Physiopathology, etiology, prognosis and treatment

Hepatic portal venous gas (HPVG), an ominous radiologic sign, is associated in some cases with a severe underlying abdominal disease requiring urgent operative intervention. HPVG has been reported with increasing frequency in medical literature and usually accompanies severe or lethal conditions. The diagnosis of HPVG is usually made by plain abdominal radiography, sonography, color Doppler flow imaging or computed tomography (CT) scan. Currently, the increased use of CT scan and ultrasound in the inpatient setting allows early and highly sensitive detection of such severe illnesses and also the recognition of an increasing number of benign and non-life threatening causes of HPVG. HPVG is not by itself a surgical indication and the treatment depends mainly on the underlying disease. The prognosis is related to the pathology itself and is not influenced by the presence of HPVG. Based on a review of the literature, we discuss in this paper the pathophysiology, risk factors, radiographic findings, management, and prognosis of pathologies associated with HPVG.

Prognostic value of multidetector computed tomography in bowel infarction

PURPOSE

This study aimed to correlate computed tomography (CT) findings and outcomes in patients affected by bowel infarction.

MATERIALS AND METHODS

Twenty-seven patients with bowel infarction due to vascular obstruction were evaluated with multidetector CT (MDCT) to establish the prognostic value of CT findings and their correlation with the origin of the ischaemia. The chi-square test was used to analyse the results (p</=0.05).

RESULTS

MDCT images allowed recognition of the nature of ischaemia in all cases. In particular, arterial occlusion was found in 67% of patients and venous obstruction in 33%. The overall mortality rate was 63%. Outcome closely correlated with the kind of vascular obstruction, with a mortality rate of 89% in arterial forms and 11% in venous forms. Bowel-wall hyperdensity (2/9 venous occlusions), loss of wall enhancement (1/9 venous occlusions, 2/18 arterial occlusions) and wall thickening (8/9 venous obstructions, 2/18 arterial occlusions) were predictive of good outcome. Bowel-loop dilatation (4/9 venous occlusions, 13/18 arterial occlusions), intramural pneumatosis (1/9 venous occlusions, 17/18 arterial occlusions), mesenteric venous gas (2/9 venous occlusions, 11/18 arterial occlusions), portal venous gas (1/9 venous occlusions, 4/18 arterial occlusions), pneumoperitoneum (8/18 arterial occlusions) and pneumoretroperitoneum (1/18 arterial occlusions) were predictive of poor outcome. Ascites (6/9 venous occlusions, 12/18 arterial occlusions) did not add any prognostic information.

CONCLUSIONS

MDCT is able to detect the nature of bowel ischaemia and provide important prognostic information.

Small bowel obstruction: what to look for

Small bowel obstruction (SBO) is a common clinical syndrome for which effective treatment depends on a rapid and accurate diagnosis. Despite advances in imaging and a better understanding of small bowel pathophysiology, SBO is often diagnosed late or misdiagnosed, resulting in significant morbidity and mortality. A comprehensive approach that includes clinical findings, patient history, and triage examinations such as plain abdominal radiography will help the clinician develop an individualized treatment plan. When an SBO is accompanied by signs of strangulation, emergent surgical treatment is advised. If surgery cannot be performed immediately or if a partial obstruction is suspected, then a more detailed radiologic work-up is needed. The imaging techniques used subsequently vary according to the initial findings. If a low-grade partial obstruction is suspected, volume-challenge enteral examinations such as enteroclysis and computed tomographic (CT) enteroclysis are preferred. If a complete or high-grade obstruction is suspected, cross-sectional studies such as ultrasonography or multidetector CT are used to exclude strangulation. An algorithmic approach to imaging is proposed for the management of SBO to achieve accurate diagnosis of the obstruction; determine its severity, site, and cause; and assess the presence of strangulation. Radiologists have a pivotal role in clinical decision making in cases of SBO by providing answers to specific questions that significantly affect management.

Mesenteric ischemia: still a deadly puzzle for the medical community

The main goal of this article is to update etiology, epidemiology, diagnosis, treatment and outcome of the various causes of mesenteric ischemia in order to elucidate its labyrinthine clinical riddle, by reviewing the current English medical literature. Mesenteric ischemia is a quite uncommon disorder, observed in the emergency department. It is a life-threatening vascular emergency that requires early diagnosis and intervention to restore mesenteric blood flow and to prevent bowel necrosis and patient death. Consequently, it is a vital diagnosis to make because of its high mortality rate and its thorny complications. The underlying causes vary, and the prognosis depends on the specific findings during clinical examination. Vague and nonspecific clinical findings and limitations of diagnostic studies make the diagnosis a significant challenge. The prognosis of acute mesenteric ischemia of any type is grave. The complications following this medical jigsaw puzzle are also severe. Patients in whom the diagnosis is missed until infarction occurs have a mortality rate of 90%. Even with good treatment, up to 50-80% of patients die. Survivors of extensive bowel resection face lifelong disability. Despite the progress in understanding the pathogenesis of mesenteric ischemia and the development of treatment modalities, the entity remains a diagnostic challenge for clinicians. Delay in diagnosis contributes to a high mortality rate. Early diagnosis and adequate treatment can improve the clinical outcome. Even if diagnostic modalities have improved since the first successful attempts to confront effectively this clinical entity, mesenteric ischemia still remains a lethal diagnostic enigma for the medical community.

CT diagnosis of acute mesenteric ischemia from various causes

OBJECTIVE

Acute mesenteric ischemia can be caused by various conditions such as arterial occlusion, venous occlusion, strangulating obstruction, and hypoperfusion associated with nonocclusive vascular disease, and the CT findings vary widely depending on the cause and underlying pathophysiology. The aim of this article is to review the CT appearances of acute mesenteric ischemia in various conditions.

CONCLUSION

Recognition of characteristic CT appearances and the variations associated with each cause may help in the accurate interpretation of CT in the diagnosis of mesenteric ischemia.

Imaging in intestinal ischemic disorders

Intestinal ischemia and infarction are a heterogeneous group of diseases that have as their unifying theme hypoxia of the small bowel or colon. The incidence of bowel ischemia and infarction is on the rise for several reasons: the aging of the population, the ability of intensive care units to salvage critically ill patients, and heightened clinical awareness of these disorders. Improvements in diagnostic imaging techniques have greatly contributed to the earlier diagnosis of intestinal ischemia, which can have a positive influence on patient outcomes. In this article, role of radiology in the detection, differential diagnosis, and management of patients who have intestinal ischemia and infarction is discussed.

Assessment of dynamic contrast enhancement of the small bowel in active Crohn's disease using 3D MR enterography

PURPOSE

To retrospectively compare the dynamic contrast enhancement of the small bowel segments with and without active Crohn's disease at 3D MR enterography (MRE).

MATERIALS AND METHODS

Thirteen patients (five men, eight women; mean age 41.2 years; range 29-56) were imaged on a 1.5-T MR scanner (Sonata, Siemens Medical) with standard MR sequences after having ingested 1000 ml of a 3% mannitol solution. Subsequently, high resolution 3D gradient-echo (volumetric interpolated breath-hold examination=VIBE) data sets were obtained pre-contrast and 20-40s, 60-80s, and 120-140 s after i.v. Gd-DOTA administration (0.2 mmol/kg). Signal enhancement was measured on single slices both in normal and histologically confirmed (12/13) inflamed small bowel wall segments as well as in the aorta, the psoas muscle, and the background to calculate signal-to-noise (SNR) and contrast-to-noise ratios (CNR).

RESULTS

Small bowel wall enhancement was significantly higher (p<0.05) in inflamed compared to normal segments at 20-40s (SNR inflamed: 58.7+/-33.8 vs normal: 36.0+/-19.8; p=0.048; CNR inflamed: 34.8+/-23.4 vs normal: 16.3+/-11.2; p=0.017) and at 60-80s (SNR: 60.3+/-25.1 vs 41.9+/-20.0; p=0.049; CNR: 34.9+/-15.1 vs 19.3+/-13.2; p=0.01) after i.v. contrast administration, respectively. Even at 120-140 s CNR was still increased in inflamed segments (33.7+/-16.0 vs 18.1+/-13.2; p=0.04), while differences in SNR did not attain statistical significance (63.0+/-26.2 vs 45.3+/-23.3; p=0.15).

CONCLUSION

In active Crohn's disease, histologically confirmed inflamed small bowel wall segments demonstrate a significantly increased early uptake of gadolinium on 3D VIBE sequences compared to normal small bowel segments.

Predicting strangulated small bowel obstruction: an old problem revisited

BACKGROUND

Diagnosing intestinal strangulation complicating a small bowel obstruction (SBO) remains a considerable challenge. Despite decades of experience and numerous studies, no clinical indicators have been identified that reliably predict this life-threatening condition. Our goal was to determine which clinical indicators in patients with SBO can be used to independently predict the presence of strangulated intestine.

METHODS

Medical records were reviewed for 192 adult patients operated on for acute SBO over an 11-year period (1996-2006). Seventy-two preoperative clinical, laboratory, and radiologic findings at admission were examined. Data from patients with strangulated intestine were compared to data from patients without bowel compromise. Likelihood ratios were generated for each significant parameter in a multivariate logistic regression analysis.

RESULTS

Forty-four patients had bowel strangulation requiring bowel resection, and 148 had no strangulation. The most significant independent predictor of bowel strangulation was the computed tomography (CT) finding of reduced wall enhancement, with a sensitivity and specificity of 56% and 94% [likelihood ratio (LR) 9.3]. Elevated white blood cell (WBC) count and guarding were moderately predictive (LR 1.7 and 2.8).

CONCLUSION

Regression analysis of multiple preoperative criteria demonstrates that reduced wall enhancement on CT, peritoneal signs, and elevated WBC are the only variables independently predictive of bowel strangulation in patients with SBO.