Acute mesenteric ischemia is the pathology with the highest mortality rate among cases of acute abdomen. An early and accurate diagnosis is necessary for saving the patient’s life, and computed tomography (CT) is the mainstay of diagnostic imaging.
The major causes of acute mesenteric ischemia include mesenteric arterial occlusion, nonocclusive mesenteric ischemia (NOMI), and mesenteric venous thrombosis. Furthermore, mesenteric arterial occlusion is caused by embolism, thrombosis, and dissection. In diagnostic CT, it is necessary not only to identify the causes but also to evaluate the severity of ischemic injury of the bowel, which affects the decision regarding treatment strategies. Here, we explain the differentiation factors for each disease causing bowel ischemia as well as imaging findings corresponding to the severity of ischemic injury of the bowel.

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Acute mesenteric arterial occlusion (AMAO) is caused by a disturbance of blood flow in the superior mesenteric artery (SMA). AMAO is classified into two main categories based on the mechanism of occlusion: SMA embolism and SMA thrombosis. Both conditions present with rapid intestinal ischemia and have a high mortality rate of more than 30% within 30 days of onset. In AMAO, (1) revascularization and (2) evaluation of the ischemic intestinal tract (± resection of the necrotic intestinal tract) are the two mainstays of the acute treatment strategy. In revascularization for AMAO, recent meta-analyses have indicated that endovascular treatment tends to have a lower bowel resection and mortality rates than open revascularization. Endovascular treatment for AMAO as minimally invasive therapy is expected to increase in the super-aging society. It is crucial that IVR physicians, who can contribute to the diagnostic imaging and endovascular treatment, are familiar with this disease and play a central role in the team.

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While spontaneous isolated superior mesenteric artery dissection (SISMAD) is rare, endovascular recanalization to avoid life-threatening mesenteric ischemia is occasionally mandatory. The treatment strategy for acute complicated aortic dissection involving bowel ischemia has been improved in the last decade, and the endovascular repair for these conditions has also been established.

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Non-occlusive mesenteric ischemia (NOMI) is described as discontinuous or segmental intestinal ischemia and/or necrosis even with patent mesenteric vessels. NOMI has no specific symptoms during the early onset stage, so making an accurate diagnosis is very difficult. Hence, patients with NOMI have a high mortality rate. Therefore, early diagnosis and treatment are very important. The usefulness of intra-arterial vasodilator infusion therapy as an endovascular treatment has already been reported, but its future role is currently unclear. Herein, we introduce the current state of NOMI management and the practice of endovascular therapy.

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Acute gastrointestinal bleeding is a cause of death, with mortality rates as high as 8-14%. Thus, it is very important to identify the cause of gastrointestinal bleeding earlier and to stop bleeding more quickly. With lower gastrointestinal bleeding (LGIB), it is often more difficult to detect the bleeding point and stop the bleeding by endoscopy than with upper gastrointestinal bleeding. However, the bleeding point identification rate by contrast-enhanced computed tomography (CT) is extremely high, with a sensitivity of 85.2% and specificity of 92.1%, and the subsequent hemostasis rate is almost 90% for both endoscopy and interventional radiolody. However, the strategy for diagnosis and treatment of LGIB differs by hospital, and the differences depend on hospital function.
We will explain the strategy for the diagnosis and treatment of LGIB, especially diverticular bleeding, with case presentations.

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There is no established interventional radiology treatment for superior mesenteric venous thrombosis (SMVT) or portal vein thrombosis (PVT). Recently, concentrated antithrombin III preparations have been approved by insurance for PVT treatment and randomized controlled trials of several direct oral anticoagulants (DOAC) for PVT to replace warfarin were conducted. The outcomes have been generally favorable although they are yet to be covered by Japanese health insurance. The cornerstone of SMVT/PVT treatment without associated bowel ischemia is immediate systemic anticoagulation with heparin, bowel rest, and fluid and electrolyte correction. The initial treatment of acute SMVT gradually shifted from surgical management to nonoperative management and now includes endovascular techniques, although this remains highly controversial. Transcatheter thrombolysis as the only revascularization method, or in combination with mechanical thrombectomy or other endovascular manipulations as a hybrid procedure, has been reported in many cases. However, definitive recommendations are difficult because of the lack of high-quality data. Treatment should be considered on a case-by-case basis.

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In treating multilocular emphysematous pyelonephritis with percutaneous drainage, the presence of septa often limits the effect of drainage. A case of multilocular emphysematous pyelonephritis successfully treated by multiple percutaneous drainage and septal destruction is reported.
A woman in her 70s was admitted for severe emphysematous pyelonephritis. Contrast-enhanced CT showed extensive multilocular lesions filled with gas in the right kidney. Conservative treatment including intravenous antibiotics was not sufficient, and percutaneous drainage was performed under fluoroscopic guidance. Due to the multilocularity, a single drainage catheter was inefficient, and three drainage catheters were placed. In addition, percutaneous septal destruction was performed with a hand-curved metal stylet that was inserted through a 6-Fr. sheath into the abscess and rotated to break the septa.
All drainage catheters were removed by 47 days, and emphysematous pyelonephritis was completely cured without surgery.

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Adrenal venous sampling (AVS) is essential for determining the optimal treatment strategy for patients with primary aldosteronism (PA) who desire surgery. There have been only a few reports of AVS in patients with a left inferior vena cava (IVC) because it is a rare anomaly. The case of a female patient with PA in her 30s with a left IVC who underwent AVS is reported. There was difficulty cannulating the right adrenal vein using a three-dimensional, double-angled catheter designed for the right adrenal vein (Adselect type I®; Hanaco Medical, Japan) because the right IVC was absent. To overcome this difficulty, the first and second angles of the Adselect type I® catheter were reshaped into a bow-like structure, and it crossed the abdominal aorta. The right adrenal vein was successfully cannulated, and the patient was diagnosed with bilateral adrenal hyperplasia based on the results of AVS. In conclusion, the right adrenal vein in a PA patient with a left IVC is difficult to cannulate because of its anatomical features. However, a reshaped catheter can be used to successfully cannulate it.

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