CT Angiography of the Mesenteric Circulation

Multidetector computer tomography and magnetic resonance imaging of double superior mesenteric veins: A case report

BACKGROUND

This study aimed to describe the findings of double superior mesenteric veins (SMVs), a rare anatomical variation, on multidetector computer tomography (MDCT) and magnetic resonance imaging (MRI) images.

CASE SUMMARY

We describe the case of a 34-year-old male, who underwent both MDC and MRI examinations of the upper abdomen because of liver cirrhosis. MDCT and MRI angiography images of the upper abdomen revealed an anatomic variation of the superior mesenteric vein (SMV), the double SMVs.

CONCLUSION

The double SMVs are a congenital abnormality without potential clinical manifestation. Physicians need to be aware of this anatomical variation during abdominal surgery to avoid iatrogenic injury.

Deep learning algorithm applied to plain CT images to identify superior mesenteric artery abnormalities

OBJECTIVES

Atypical presentations, lack of biomarkers, and low sensitivity of plain CT can delay the diagnosis of superior mesenteric artery (SMA) abnormalities, resulting in poor clinical outcomes. Our study aims to develop a deep learning (DL) model for detecting SMA abnormalities in plain CT and evaluate its performance in comparison with a clinical model and radiologist assessment.

MATERIALS AND METHODS

A total of 1048 patients comprised the internal (474 patients with SMA abnormalities, 474 controls) and external testing (50 patients with SMA abnormalities, 50 controls) cohorts. The internal cohort was divided into the training cohort (n = 776), validation cohort (n = 86), and internal testing cohort (n = 86). A total of 5 You Only Look Once version 8 (YOLOv8)-based DL submodels were developed, and the performance of the optimal submodel was compared with that of a clinical model and of experienced radiologists.

RESULTS

Of the submodels, YOLOv8x had the best performance. The area under the curve (AUC) of the YOLOv8x submodel was higher than that of the clinical model (internal test set: 0.990 vs 0.878, P =.002; external test set: 0.967 vs 0.912, P =.140) and that of all radiologists (P <.001). The YOLOv8x submodel, when compared with radiologist assessment, demonstrated higher sensitivity (internal test set: 100.0 % vs 70.7 %, P =.002; external test set: 96.0 % vs 68.8 %, P <.001) and specificity (internal test set: 90.7 % vs 66.0 %, P =.025; external test set: = 88.0 % vs 66.0 %, P <.001).

CONCLUSION

Using plain CT images, YOLOv8x was able to efficiently identify cases of SMA abnormalities. This could potentially improve early diagnosis accuracy and thus improve clinical outcomes.

Surgical anatomy and clinical variation of the left colonic artery in laparoscopic anterior rectal resection

Objectives

This study aims to investigate the surgical anatomy and clinical variation of the left colonic artery (LCA) during laparoscopic anterior rectal resection.

Methods

We conducted a retrospective analysis of 87 patients diagnosed with colorectal cancer who underwent laparoscopic anterior rectal resection with preserved LCA at the Department of Gastroenterology, Sichuan Cancer Hospital, between March 2018 and April 2022, aiming to observe the emanation location, anatomical typing, and travel trajectory of the LCA, as well as its relationship with the inferior mesenteric vein (IMV).

Results

In all observed cases, we observed that the LCA emanated from the left side of the inferior mesenteric artery (IMA), and the average distance from the root of the IMA to the emanation of the LCA was approximately 3.5 ± 1.1 cm. Specifically, 35 of these cases had the LCA branching from the IMA alone (Type I, 40.2%),16 cases had the LCA cotruncating with the sigmoid artery (SA) (Type II, 18.4%), 30 cases had the LCA cotruncating with the superior rectal artery (SRA) and SA (Type III, 34.5%), and six cases had the LCA cotruncating with four or more branches of the SRA and SA (Type IV, 6.9%). No LCA agenesis cases were found in this group. In addition, we also observed the occurrence of LCA alignment. Specifically, there were 25 cases where the LCA crossed the IMV in a diagonal upward direction (Type A, 28.7%), 36 cases where the LCA crossed the IMV in an upward arched manner (Type B, 41.4%), 18 cases where the LCA crossed the IMV in a vertical outward direction (Type C, 20.7%), and eight cases where the LCA crossed the IMV in a diagonal downward manner (Type D, 9.2%). Among them, two cases developed anastomotic fistula, one case had chyle leakage 1 week after surgery, and four cases experienced urinary retention; all of the patients successfully recovered and were discharged after receiving conservative treatment.

Conclusion

The anatomy and variation of the LCA can be clearly and accurately observed during laparoscopic surgery. Understanding the type and variation of the LCA helps to dissect the vessels in the IMA region during surgery, particularly in cases when the LCA is preserved, and reduce the incidence of vascular injury and its complications.

Preoperative assessment of blood supply and its role in predicting anastomotic leak

BACKGROUND

Anastomosis leak is one of the significant postoperative complications after colorectal surgery. The aim of this systematic review was to synthesize the evidence relative to the preoperative assessment of the colon and rectum blood supply and to investigate its role in predicting anastomosis leak.

METHOD

This systematic review was conducted according to the recommendations of the Cochrane Handbook for Reviews of Interventions and reported according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses. PubMed, Embase, and the Cochrane Library were searched to identify eligible studies. The main outcome variable was the preoperative assessment of patterns of blood supply to the colon and the impact of these patterns on anastomosis leak. The quality of bias control in the studies was assessed using the Newcastle-Ottawa Scale. Due to the heterogeneous nature of the included studies, no meta-analysis was conducted.

RESULTS

Fourteen studies were included. The study covered a period from 1978 to 2021. A significant degree of variation in the arterial and/or venous supply of the colon and rectum might influence anastomosis leak rates. Calcification in great blood vessels can be assessed with a preoperative computed tomography scan, which may predict anastomosis leak rates. This is supported by many experimental studies that showed increased rates of anastomosis leak after preoperative ischemia, but the extent of this impact is not well established.

CONCLUSION

Preoperative assessment of blood supply to the colon and rectum might help in planning the surgical intervention to reduce anastomosis leak rates. Calcium scoring of major arteries might predict anastomosis leak and thus play a crucial role in intraoperative decision-making.

An Update on Acute Mesenteric Ischemia

Acute mesenteric ischemia (AMI) is an uncommon yet highly lethal cause of acute abdomen in the emergency setting. Computed tomography (CT) imaging, in particular a biphasic protocol consisting of angiographic and venous phase scans, is widely used to corroborate non-specific clinical findings when suspicions of AMI are high. Techniques such as low kilovoltage peak scanning, dual energy acquisition, or a combined arterial/enteric phase can improve iodine conspicuity and evaluation of bowel enhancement. Biphasic CT with CT angiography is mandatory to directly assess for the 3 primary etiologies of AMI-arterial, venous, and non-occlusive mesenteric ischemia (NOMI), and the CT angiographic findings may be the first visible in the disease. In addition, numerous non-vascular CT findings have also been reported. Bowel wall thickening, mesenteric stranding, and ascites are common but non-specific findings that correlate poorly with disease severity. Pneumatosis intestinalis and portomesenteric venous gas, while not pathognomonic for ischemia, are highly specific in cases of high clinical suspicion. Bowel wall hypoenhancement is an early and specific sign but requires a protocol optimizing iodine conspicuity to confidently identify. Finally, intraperitoneal free air and solid organ infarcts are also highly specific ancillary findings in AMI. AMI occurs as a complication in 10% of small bowel obstruction (SBO) patients, and understanding imaging findings of ischemia in the context of SBO is necessary to aid in treatment planning and reduce over- and under-diagnosis of strangulation. Familiarity with the imaging features of ischemia by radiologists is vital to establish an early diagnosis before irreversible necrosis occurs.

Mesenteric ischemia: a radiologic perspective

Mesenteric ischemia is a broad term encompassing several clinical conditions leading to impaired vascularity of bowel loops. Absence of specific clinical presentation and a definitive laboratory marker often lead to delayed diagnosis with high morbidity and mortality in the acute setting. Imaging plays a crucial role in the diagnosis and management. Multi-detector CT (MDCT) is the first line imaging modality for the evaluation of patients with suspected mesenteric ischemia and plays an important role for assessing its severity and complications. This review article highlights the causes, pathophysiology, imaging features and possible endovascular treatment options of mesenteric ischemia.

Comprehensive review of acute small bowel ischemia: CT imaging findings, pearls, and pitfalls

Acute small bowel ischemia is a life-threatening condition with a high mortality rate due to its lack of specific symptoms and laboratory profile, which render difficulty in establishing early diagnosis. The etiology of acute small bowel ischemia includes occlusive forms (arterial embolism, arterial thrombosis, and venous thrombosis) and nonocclusive mesenteric ischemia, of which arterial causes are far more common than venous causes. CT, the mainstay of accurate diagnoses, allows the identification of the features of vascular abnormalities and intestinal ischemic injuries, and helps clinicians to restore intestinal blood flow. Without treatment, the prognosis for acute small bowel ischemia is poor. A high index of suspicion and familiarity with the CT spectral findings of bowel ischemia are required to ensure rapid recognition of this condition.

Acute Mesenteric Infarction: The Chameleon of Acute Abdomen Evaluating the Quality of the Diagnostic Parameters in Acute Mesenteric Ischemia

INTRODUCTION/OBJECTIVE

Acute mesenteric ischemia (AMI) is difficult to diagnose. Since the established parameters have low sensitivity and specificity, the aim of this study is to analyze the diagnostic quality of the established parameters of AMI.

METHODS

All patients that underwent emergency surgery due to suspected diagnosis of mesenteric ischemia at the University Medical Center Hamburg-Eppendorf between 2008 and 2014 were evaluated. Overall, 275 patients were enrolled and pre-, intra- and postoperative data were evaluated.

RESULTS

In 200 patients, a mesenteric ischemia was confirmed intraoperatively, and 75 patients had no ischemia. Comparing these groups, the rate of patients with pH < 7.2 (25 vs. 12%; p = 0.021) and elevated mean CRP level (175 ± 117 mg/L vs. 139 ± 104 mg/L; p = 0.019) was significantly higher in ischemic patients. There was no significant difference in the level of preoperative lactate. Concerning abdominal CT scan, a sensitivity and specificity of 61 and 68%, respectively, was found.

CONCLUSION

New diagnostic parameters are needed. So far, explorative laparotomy is the only reliable diagnostic method to detect mesenteric infarction.

Precision image-guided colonic surgery: proof of concept for enhanced preoperative and intraoperative vascular imaging

BACKGROUND

Colorectal surgery has benefited from advances in precision medicine such as total mesorectal resection, and recently, mesocolon resection, fluorescent perfusion imaging, and fluorescent node mapping. However, these advances fail to address the variable quality of mesocolon dissection and the directed extent of vascular dissection (including high ligation) or pre-resection anastomotic perfusion mapping, thereby impacting anastomotic leaks. We propose a new paradigm of precision image-directed colorectal surgery involving 3D preoperative resection modeling and intraoperative fluoroscopic and fluorescence vascular imaging which better defines optimal dissection planes and vascular vs. anatomy-based resection lines according to our hypothesis.

METHODS

Six pigs had preoperative CT with vascular 3D reconstruction allowing for the preoperative planning of vascular-based dissection. Laparoscopic surgery was performed in a hybrid operating room (OR). Superselective arterial catheterization was performed in branches of the superior mesenteric artery (SMA) or the inferior mesenteric artery (IMA). Intraoperative boluses of 0.1 mg/kg or a continuous infusion of indocyanine green (ICG) (0.01 mg/mL) were administered to guide fluorescent-based sigmoid and ileocecal resections. Fluorescence was assessed using proprietary software at several regions of interest (ROI) in the right and left colon.

RESULTS

The approach was feasible and safe. Selective catheterization took an average of 43 min. Both bolus and continuous perfusion clearly marked pre-identified vessels (arteries/veins) and the target colon segment, facilitating precise resections based on the visible vascular anatomy. Quantitative software analysis indicated the optimal resection margin for each ROI.

CONCLUSION

Intra-arterial fluorescent mapping allows visualization of major vascular structures and segmental colonic perfusion. This may help to prevent any inadvertent injury to major vascular structures and to precisely determine perfusion-based resection planes and margins. This could enable tailoring of the amount of colon resected, ensure good anastomotic perfusion, and improve oncological outcomes.

High-Value Multidetector CT Angiography of the Superior Mesenteric Artery: What Emergency Medicine Physicians and Interventional Radiologists Need to Know

The superior mesenteric artery (SMA) provides vital blood supply to the midgut, and an acute abnormality can rapidly precipitate bowel ischemia and infarction and lead to morbidity and mortality. Vascular diseases that acutely compromise the SMA threaten its tributaries and include occlusion, dissection, aneurysm rupture, pseudoaneurysm, vasculitis, and SMA branch hemorrhage into the bowel. Emergency medicine physicians rely on the radiologist to identify SMA abnormalities, to characterize them, and to detail findings that guide the appropriate triage of these patients. As such, radiologists must be cognizant of the features that influence patient treatment to assist vascular surgeons and interventional radiologists in decision making. Some patients can be treated medically, while clinical and radiographic findings may suggest the need for interventional or surgical repair of the artery. In the latter case, multidetector CT findings aid in determining which of the various surgical and endovascular treatment options is optimal, and both vascular and gastrointestinal sequelae of acute SMA abnormalities contribute to these determinations. The authors review acute life-threatening conditions involving the SMA including acute occlusion, dissection, aneurysm, pseudoaneurysm, and hemorrhage and discuss the vascular and gastrointestinal multidetector CT findings in each of these conditions that help to guide surgical and interventional management. ^©RSNA, 2019.

Accurate diagnosis and treatment of isolated mesenteric artery dissections

Objectives

Diagnosis and treatment of isolated mesenteric artery dissections (IMAD) are overlooked. The purpose of this study was to assess the clinical feature, possible diagnostic errors and treatment methods.

Methods

From January 2010 to December 2017, 99 consecutive patients who were diagnosed with IMAD on computed tomography angiography were enrolled retrospectively. Thirty-nine misdiagnosed patients, false negative, and 60 accurate diagnosis patients with revealed IMAD were compared. In addition, therapeutic schemes were evaluated.

Results

Ninety-nine patients participated in this study; 39 patients (34 men, 5 women; median age, 51.41 years, range 38–64 years) were included in group A who were misdiagnosed initial visit; the remaining 60 patients (52 men, 8 women; median age, 52.07 years, range 38–68 years) with IMAD who were diagnosed accurately initial visit were included in group B. Significant differences were observed between the two groups with respect to dissection length (55.26 ± 3.88 mm vs. 43.37 ± 2.75 mm; p = 0.01), and branch involvement (14 and 9, respectively; p = 0.04). Ultimately, 33 patients (group A 14 patients and group B 19 patients) underwent invasive interventional therapy, and 66 patients with conservative treatment with antithrombotic agents (group A 25 patients and group B 41 patients). A total of 86 (86.87%) had follow-up computed tomography angiography with a median duration of 24.51 months (range 2–71 months). Three patients died during follow-up. The remaining patients recovered smoothly.

Conclusion

Physicians should raise the awareness of IMAD and use the optimal treatment time frame. Diagnosis of IMAD depends on imaging examinations, especially computed tomography angiography. Additionally, conservative management is the most common initial treatment. For patients in whom conservative treatment fails, endovascular and/or surgery may be necessary.

Diagnosing Internal Herniation After Roux-en-Y Gastric Bypass Surgery: Literature Overview, Cadaver Study and the Added Value of 3D CT Angiography

Purpose

The purposes of the study are to outline the complexity of diagnosing internal herniation after Roux-en-Y gastric bypass (RYGB) surgery and to investigate the added value of computed tomography angiography (CTA) for diagnosing internal herniation.

Materials and Methods

A cadaver study was performed to investigate the manifestations of internal hernias and mesenteric vascularization. Furthermore, a prospective, ethics approved study with retrospective interpretation was conducted. Ten patients, clinically suspected for internal herniation, were prospectively included. After informed consent was obtained, these subjects underwent abdominal CT examination, including additional arterial phase CTA. All subjects underwent diagnostic laparoscopy for suspected internal herniation. The CTA was used to create a 3D reconstruction of the mesenteric arteries and surgical staples (3D CTA). The 3D CTA was interpreted, taking into account the presence and type of internal hernia that was found upon laparoscopy.

Results

Cadaveric analysis demonstrated the complexity of internal herniation. It also confirmed the expected changes in vascular structure and surgical staple arrangement in the presence of internal herniation. 3D CTA studies of the subjects with active internal hernias demonstrated remarkable differences when compared to control 3D CTA studies. The blood supply of herniated intestinal limbs in particular showed abnormal trajectories. Additionally, enteroenterostomy staple lines had migrated or altered orientation.

Conclusion

3D CTA is a promising technique for diagnosing active internal hernias. Our findings suggest that for diagnosing internal hernias, focus should probably shift from routine abdominal CT examination towards the 3D assessment of the mesenteric vasculature and surgical staples.

Electronic supplementary material

The online version of this article (10.1007/s11695-018-3121-3) contains supplementary material, which is available to authorized users.

Mesenteric ischemia: what the radiologist needs to know

Acute mesenteric ischemia (AMI) is a life-threatening condition that often presents with abdominal pain. Early diagnosis with contrast-enhanced computed tomography and revascularization can reduce the overall mortality in AMI. This article reviews practical etiological classification, pathophysiology of imaging manifestations and common pitfalls in intestinal ischemia.

Thrombectomy Devices in the Treatment of Acute Mesenteric Ischemia: Initial Single-Center Experience

BACKGROUND

To report our preliminary experience with endovascular revascularization of patients with acute mesenteric ischemia (AMI), using thrombectomy devices.

METHODS

It is a retrospective analysis of patients admitted to our hospital due to AMI and who were subjected to concomitant or exclusive endovascular treatment, from January 2011 to January 2016. Patients were admitted at the emergency department, underwent imaging investigation, and were referred to the endovascular specialist. Endovascular treatment was performed through left brachial artery access and selective catheterization and thrombectomy with a 6F Rotarex Debulking Device (Straub Medical, Wangs, Switzerland). Laparotomy was performed based on clinical and radiologic sings and at the discretion of the surgeon. Demographic, clinical/periprocedural, postoperative, complication, and adjunct intervention data were reviewed. Technical success was defined as recanalization of the Riolan's arcade on angiographic control.

RESULTS

Twenty patients (mean age: 69.8 ± 11.3 years) underwent endovascular revascularization for AMI using thrombectomy devices, during the period of the study. Abdominal pain was the most common complain on admission (65%), with ileus (35%), sepsis (25%), and myocardial infarction as the main clinical referral presentation at admission. Fifteen patients (75%) had suggestive computer tomography (CT) signs of AMI on admission. Endovascular revascularization was successfully performed in all patients through the left brachial artery with a mean procedural time of 28 ± 17 min. Superior mesenteric artery (SMA) was the main vessel involved in 75% on a solely basis. The majority of the SMA occlusions were in the periosteal (30%) and proximal to middle colic artery offspring (35%). Primary use of thrombectomy devices was performed in all patients, associated with balloon angioplasty (7/20; 50%), stent deployment (5/20; 25%), intraoperative selective thrombolysis (4/20; 20%) and catheter-assisted aspiration in 10% (2/20) of patients. Average time between admission and computed tomography angiography was 1.5 ± 0.5 hr, between admission and angiographic procedure was 2.5 ± 1 hr, and between admission and surgery was 9 ± 5 hr. Following recanalization, 14 patients (70%) underwent open surgery. Laparotomy with intestinal resection (enterectomy, colectomy) and transit deviation was the most common procedure. Complications directly related to the endovascular procedure occurred in 2 patients, represented by self-limited small perforations. Overall 30-day mortality was 40% (n = 8). During the period of this study, no patient died as a result of complications related to the use of rotational thrombectomy.

CONCLUSIONS

Endovascular treatment of the AMI with the use of thrombectomy devices proved to be technically feasible and reasonably fast procedure. Early diagnosis and adequate treatment remains the cornerstone of the treatment. Early surgical evaluation and close integration between surgical and endovascular specialists are crucial to faster treatment and consequently lower extensive surgical resections and mortality. Further studies are necessary on this field to confirm these findings.

Aneurysm of the Anomalous Splenic Artery Arising from Superior Mesenteric Artery Treated by Coil Embolization: A Report of Two Cases and Literature Review

BACKGROUND

Aneurysm of splenic artery (SA) which arises from the superior mesenteric artery (SMA) is a very rare condition. The aim of this study was to present our experience with 2 such patients treated by coil embolization.

METHODS

A 33-year-old man and a 61-year-old woman were incidentally identified with aneurysms of the SA which arose from the SMA. Endovascular therapy of coil embolization was chosen to treat the aneurysm.

RESULTS

Follow-up computed tomography showed no change in the location of the coils and occlusion of majority of the aneurysm sac. The 2 patients have been doing well during a 26-month and 10-month follow-up period, respectively.

CONCLUSIONS

Combined with the experience of the previous literature, we think coil embolization can be cost-effective and minimally invasive in selected cases, depending on the morphology and site of the lesion.

Vascular imaging of the mesenteric vasculature

Imaging of the mesenteric vasculature is crucial in diagnosing vascular disease of the gastro-intestinal tract such as acute or chronic mesenteric ischemia caused by arterial stenosis, embolism or thrombosis, mesenteric vein thrombosis and mesenteric aneurysm or dissection. The reference standard for imaging of the mesenteric vasculature is digital subtraction angiography. However, modalities as duplex ultrasonography, computed tomography angiography and magnetic resonance angiography are developing rapidly and may provide accurate imaging non-invasively. This review provides an up-to-date overview of the anatomic resolution, clinical application, emerging techniques and future perspectives of these four radiological modalities for imaging of the mesenteric vasculature.

CT assessment of right colonic arterial anatomy pre and post cancer resection - a potential marker for quality and extent of surgery?

BACKGROUND

There is conflicting opinion as to the optimum extent of resection for right-sided colonic cancer, which is currently graded by pathological analysis of the resected specimen. It is not known if computed tomography (CT) analysis of residual post-resection arterial stump length could be used as an alternative in vivo marker for extent of mesenteric resection. Ileocolic artery stumps have been demonstrated previously on CT after right hemicolectomy, but only in the early postoperative period.

PURPOSE

To analyze preoperative right colonic arterial anatomy using portal venous colorectal cancer staging CT and subsequently determine if post-resection arterial stumps (a potential in vivo marker of surgical resection) could be consistently identified using routine follow-up CT scans many months after cancer resection.

MATERIAL AND METHODS

A retrospective analysis of routine staging and follow-up CT scans for 151 patients with right-sided colorectal cancer was performed. Preoperative right colonic arterial anatomy and postoperative arterial stumps were analyzed and measured.

RESULTS

Preoperative ileocolic (98.8%), middle (94.7%), and right colic artery (23.8%) identification was comparable to catheter angiogram studies. Postoperative ileocolic stumps were consistently demonstrated (88.3%) many months (average, 2 years and 42 days) after resection and were significantly longer than expected for a standard D2 resection (paired t-test, t(127) = -11.45, P ≤ 0.001).

CONCLUSION

This is the first study to successfully demonstrate ileocolic arterial stumps many months (and years) after cancer resection using routine portal venous CT. Further prospective research should assess whether arterial stumps can be used as an in vivo marker of surgical quality and extent.

Computed Tomography Angiography of the Hepatic, Pancreatic, and Splenic Circulation

Multidetector computed tomography angiography (MDCTA) has become a routine imaging tool to assess visceral vascular anatomy and abdominal parenchymal pathology. Enhanced temporal resolution and rapid acquisition allow for precise delineation of arterial and venous anatomy. The excellent spatial resolution permits assessment of small parenchyma lesions and vasculature. The ability of CT to rapidly acquire data and reconstruct with thinner slices allows robust 3D mapping using maximum intensity projection before definitive surgical or interventional therapy. Emerging novel techniques of image acquisition offer sensitive methods for detecting enhancement and allow for virtual imaging subtraction, all while limiting the total radiation burden.

Mesenteric inflammatory veno-occlusive disease: radiographic and histopathologic evaluation of 2 cases

Mesenteric inflammatory veno-occlusive disease (MIVOD) is a rare cause of inflammatory enterocolitis whose clinical and imaging presentation can be confused with mesenteric venous thrombosis and inflammatory bowel disease. We report two cases of histologically proven MIVOD in patients presenting with abdominal pain and describe potentially useful distinguishing features at contrast-enhanced CT, including prominent small pericolonic arteries and veins but a diminutive or absent inferior mesenteric vein. Alerting referring clinicians to the possibility of this diagnosis may help avoid unnecessary anticoagulation and reduce diagnostic delay. Treatment of MIVOD is surgical resection, which is typically curative.

Multidetector computed tomography of mesenteric ischaemia

Mesenteric ischaemia comprises a broad, heterogeneous group of diseases characterised by inadequate blood supply to the small or large bowel. Acute mesenteric ischaemia is a surgical emergency, with significant associated morbidity and mortality. Because the clinical presentation of mesenteric ischaemia is variable and often nonspecific, a high index of clinical and radiologic suspicion is required for early diagnosis. The severity of mesenteric ischaemia ranges from transient, localised ischaemia to frank necrosis of the bowel. The most common causes of acute mesenteric ischaemia are embolic and thrombotic occlusion of the superior mesenteric artery, whereas chronic mesenteric ischaemia is almost always associated with generalised atherosclerotic disease. Multidetector computed tomography (MDCT) angiography is the preferred imaging test for acute and chronic mesenteric ischaemia. MDCT is useful in making a prompt, more precise diagnosis of mesenteric ischaemia, as well as identifying the cause and potential complications, which are key to reducing patient morbidity and mortality. In this article, we review the clinical features and aetiologies of mesenteric ischaemia and illustrate the imaging manifestations on MDCT.

• Acute and chronic mesenteric ischaemia are morbid conditions challenging to diagnose.

• MDCT is the first-line imaging test for evaluating patients with suspected mesenteric ischaemia.

• Bowel findings include wall thickening, abnormal enhancement, pneumatosis and luminal dilation.

• Vascular occlusion, portomesenteric venous gas, mesenteric congestion and free air can be seen.

Acute Mesenteric Ischaemia

Acute mesenteric ischaemia (AMI) is a surgical emergency, and has a high mortality. The term AMI covers arterial embolism, arterial thrombosis, non-occlusive mesenteric ischaemia and venous thrombosis which all lead to ischaemia/reperfusion syndrome of the bowel. Multi-detector row helical CT (MDCT) technology has dramatically improved the performance of CT by allowing rapid volumetric data acquisition to provide increased resolution, leading to better identification of the site, level and cause of ischaemia. CT angiography for diagnosing mesenteric ischaemia is now highly sensitive and specific, and should be used as first line when AMI is suspected. The aim of management is to restore intestinal blood flow in a timely manner. Therapeutic decisions are based on the presence of peritonitis, the presence of irreversible ischaemia or infarcted segments of the bowel, the general condition of the patient and the pathophysiological process underlying the ischaemia. AMI remains a challenging condition with high mortality. There is a need for good general surgical cover on the intensive care unit, with continuing care and clinical review by experienced senior surgeons with an interest in this condition.

The revised Atlanta classification for acute pancreatitis: updates in imaging terminology and guidelines

Imaging of acute pancreatitis requires not only an understanding of the disease subtypes and the myriad of associated complications but also familiarity with the appropriate radiologic nomenclature as defined by the Atlanta symposium in 1992 and, more recently, by the Acute Pancreatitis Classification Working Group in 2008. The accurate description of the radiological findings plays a critical role in the evaluation and management of patients with acute pancreatitis, particularly those with severe disease. There have been increasing efforts to develop uniformity in the use of terminology used to define the radiologic findings in acute pancreatitis, in particular, the terminology for fluid collections, a common area of inconsistency and confusion. Terms such as "acute peripancreatic fluid collections," "acute post- necrotic fluid collections," "pseudocyst," and "walled-off pancreatic necrosis" are now recommended as they describe the evolution of fluid collections in patients with both interstitial and necrotizing pancreatitis and nonspecific terms such as "pancreatic abscess" and "phlegmon" are being abandoned. In this review we illustrate, with case examples, the standardized terminology used in the radiological and clinical description of acute pancreatitis, its severity, and complications with an emphasis on the role of ultrasound, computed tomography and magnetic resonance imaging. Different management options of the associated complications are also discussed. The use of standardized terminology will hopefully improve the communication between radiologists, gastroenterologists, and surgeons to facilitate treatment planning and will lead to enhanced outcomes for patients with acute pancreatitis as well as create uniformity for enrollment into research studies.

Comparison between survey radiography, B-mode ultrasonography, contrast-enhanced ultrasonography and contrast-enhanced multi-detector computed tomography findings in dogs with acute abdominal signs

Contrast-enhanced multi-detector computed tomography (CE-MDCT) is used routinely in evaluating human patients with acute abdominal symptoms. Contrast-enhanced ultrasound (CEUS) continues to be in its infancy as it relates to evaluation of the acute abdomen. The purpose of this study was to compare survey radiography, B-mode ultrasound, CEUS, and CE-MDCT findings in canine patients presenting with acute abdominal signs; with a focus on the ability to differentiate surgical from non-surgical conditions. Nineteen dogs were prospectively enrolled. Inclusion required a clinical diagnosis of acute abdominal signs and confirmed surgical or non-surgical causes for the clinical signs. Agreement for the majority of recorded imaging features was at least moderate. There was poor agreement in the identification of pneumoperitoneum and in the comparison of pancreatic lesion dimensions for B-mode vs. CEUS. The CT feature of fat stranding was detected in cases including, but not limited to, gastric neoplasia with perforation, pancreatitis, and small intestinal foreign body. Ultrasound underestimated the size and number of specific lesions when compared with CE-MDCT. Contrast-enhanced ultrasound was successful in detecting bowel and pancreatic perfusion deficits that CE-MDCT failed to identify. Accuracy for differentiation of surgical vs. non-surgical conditions was high for all modalities; 100%, 94%, and 94% for CE-MDCT, ultrasonography and survey radiography respectively. Findings indicated that CE-MDCT is an accurate screening test for differentiating surgical from non-surgical acute abdominal conditions in dogs. Focused CEUS following CE-MDCT or B-mode ultrasonography may be beneficial for identifying potentially significant hypoperfused lesions.

The impact of early diagnostic laparoscopy on the prognosis of patients with suspected acute mesenteric ischemia

PURPOSE

To assess the impact of early diagnostic laparoscopy in patients with suspected acute mesenteric ischemia in whom other diagnostic studies are inconclusive or unavailable.

METHODS

The medical records of patients who underwent diagnostic laparoscopy with a preoperative diagnosis of acute mesenteric ischemia between January 2008 and January 2012 were reviewed. The patients who had a preoperative diagnosis of acute mesenteric ischemia based on computed tomography or angiography were excluded. Outcome variables were the time between admission and diagnostic laparoscopy, overall revascularization rate, successful revascularization rate, and in-hospital mortality rate.

RESULTS

Fifty-three patients were included in the study. Twelve patients (22.6 %) had negative diagnostic laparoscopy. In 43 patients (77.4 %) who were found to have acute mesenteric ischemia at diagnostic laparoscopy, the mean time between admission and diagnostic laparoscopy, overall revascularization rate, successful revascularization rate, and in-hospital mortality rate were 10.2 h, 32.5 %, 13.9 %, and 74.4 %, respectively. The mean time between admission and diagnostic laparoscopy was significantly shorter in patients who underwent successful revascularization, and in those who survived with or without developing short bowel syndrome.

CONCLUSIONS

Diagnostic laparoscopy is a safe and reliable diagnostic tool that can have a positive impact on the prognosis of patients with suspected acute mesenteric ischemia if carried out in a timely manner when radiological diagnostic studies are inconclusive or unavailable.

Role of CT angiography with three-dimensional reconstruction of mesenteric vessels in laparoscopic colorectal resections: a randomized controlled trial

BACKGROUND

Laparoscopic surgery, despite its well-known advantages and continuous technological innovations, still has limitations such as the lack of tactile sensation and reduced view of the operative field. These limitations are particularly evident when performing laparoscopic colorectal resection due to the variability of the number and course of mesenteric vessels. Today, the patient's vascular anatomy can be mapped using computed tomography (CT) angiography and processing of the images with rendering software to reconstruct a three-dimensional model of the mesenteric vessels. To assess how prior knowledge of the patient's mesenteric vascular anatomy represents an advantage when performing laparoscopic colorectal resections, we conducted a randomized, parallel, single-blinded controlled trial.

METHODS

From January 2010 to January 2012, all patients with surgical indication to undergo standardized right or left hemicolectomy and anterior rectal resections were randomly assigned to two groups and subjected to CT angiography with three-dimensional reconstruction of mesenteric vessels. In the first group the surgeon was able to view the 3D reconstruction before and during surgery, while in the second group the surgeon was only able to view the 3D reconstruction after surgery.

RESULTS

Evaluation of data from 112 patients shows statistically significantly lower operative time, episodes of difficult identification of right anatomy, and incidence of intraoperative and postoperative complication related to difficult or erroneous identification of mesenteric vessels in the group in which the surgeon was able to view the 3D reconstruction before and during surgery compared with the control group.

CONCLUSION

This study shows that prior knowledge of the patient's mesenteric vascular anatomy represents an advantage when performing laparoscopic colorectal resection.

A study on 107 patients with acute mesenteric ischemia over 30 years

Acute mesenteric ischemia (AMI) is a life threatening cause of acute abdomen. The purpose of this study is to define risk factors that predict the adverse outcome of AMI and to present our experience in the last 30 years. Hospital records and clinical data of 107 patients undergoing surgical intervention for AMI during the last 30 year period were reviewed and clinical outcomes as well as factors influencing mortality were analyzed. Mesenteric arterial thrombosis, arterial embolism and nonocclusive mesenteric ischemia (NOMI) were the cause of AMI in 68 (63.6%), 28 (26%), and 11 patients (10.2%), respectively. Abdominal pain was the most common presenting symptom (90.6%). Peritonitis was observed in 96 patients (89.7%) and 24 patients (22.4%) were in shock. Abdominal ultrasonography was performed in 46 patients (42%), abdominal CT angiography in 36 patients (33%) and mesenteric angiography in 12 patients (10.5%). All patients were operated and 11 (10%) patients underwent a second-look operation. Bowel resection was necessary in 101 patients (93.4%) during the initial operation and in seven patients (6.5%) during the second-look operation. The hospital mortality was 55.1%. Mortality was mainly due to multiorgan failure (43%). Diabetes mellitus, use of digoxine and antiplatelet drugs, duration of the symptoms until before surgery, existence of shock, low levels of the pH and bicarbonate and re-laparotomy were found to be negative predictors of the perioperative mortality. The use of total parenteral nutrition and CT angiography was found to be a protective factor against mortality. A high index of suspicion with prompt diagnostic evaluation with CT angiography may reduce time prior to surgical intervention which may lead to improved patient survival.

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.