Two case reports of two interventional radiology techniques for the treatment of stage II empyema: Hydrodissection and guidewire-dissection.

Empyema is an infection of the pleural space that is classified into 3 stages. Video-assisted thoracoscopic surgery is recommended as the first-line approach for stage II acute empyema. The purpose of video-assisted thoracoscopic surgery is also achieved with hydrodissection and guidewire-dissection by breaking the septa mechanically in the pleural cavity. Hydrodissection and guidewire-dissection are techniques in which a contrast medium is administered at high pressure and a guidewire is inserted into the pleural cavity to break the septa, respectively. Hydrodissection and guidewire-dissection might be minimally invasive alternatives for the treatment of septated empyema.

[Successful Treatment with TACE and RFA for a Hepatocellular Carcinoma Case with Lung Metastasis].

We report a hepatocellular carcinoma(HCC)case with lung metastasis that was successfully treated with transarterial chemoembolization(TACE)and percutaneous radiofrequency ablation(RFA). A man in his 60s took right robe liver resection for HCC after TACE for its rupture. Lung metastasis occurred at S1+2 and S6 in the left lung, and an adverse event interrupted standard molecular target therapies. Because extrahepatic metastasis had been seen only in these two locations for a long time, TACE was performed for both metastases. The feeders for both lesions were each intercostal artery, and controlling the drug inflow was necessary to avoid drug influx into the spinal cord branches when S6 metastasis was treated. The viable lesion remained in the S6 lesion, so RFA was added for both lung metastases. 100% tumor necrosis has been observed since the RFA.

Taxonomic identity of four groups of Glandirana rugosa (Anura, Ranidae) in Japan revealed by the complete mitochondrial genome sequence analysis.

The Japanese Glandirana rugosa phylogenetically consists of four groups. However, the taxonomic identity of these groups still remains unclear. We determined the complete mitogenome sequences of the four groups of G. rugosa. The mitogenomes were 17,394-17,781 bp in length. The phylogenetic analysis clearly showed that the genus Glandirana is monophyletic and that the four groups of G. rugosa are separated into two clusters: one cluster represents G. rugosa, the other cluster may represent a different species.

Pleuroparenchymal fibroelastosis-like lesions in patients with interstitial pneumonia diagnosed by multidisciplinary discussion with surgical lung biopsy.

PURPOSE: The present study aimed to evaluate the significance of Pleuroparenchymal fibroelastosis (PPFE)-like lesions in predicting prognosis in patients with chronic interstitial pneumonia (IP). METHOD: The present study enrolled 207 patients with IP in whom surgical lung biopsy was performed. Among the patients enrolled in the present study, 77 had idiopathic pulmonary fibrosis (IPF), 15 had nonspecific interstitial pneumonia (NSIP), 13 had chronic hypersensitivity pneumonitis (CHP), 41 had connective tissue disease (CTD), three had PPFE, and 58 had unclassifiable diagnosis. The incidence, characteristics, and thickness of PPFE-like lesions were evaluated in each patient with IP. Additionally, the influence of PPFE-like lesions on the prognosis was also determined. RESULTS: Of 207 patients, 160 (77.3 %) showed PPFE-like lesions. The frequency of PPFE-like lesions was similar in patients with IPF, NSIP, CHP, CTD, and unclassifiable diagnosis (79.5 %, 79.5 %, 73.2 %, 65.9 %, and 81 %, respectively); however, PPFE-like lesions were present in all patients with PPFE (p = 0.42). Consequently, there was no significant difference in the characteristics of PPFE-like lesions among patients with all forms of IP, except PPFE. PPFE-like lesions were not a significant predictor of prognosis (hazard ratio [HR], 1.16; 95 % confidence interval [CI], 0.64-2.10, p = 0.62); however, patients with PPFE-like lesions under the aortic arch had significantly poorer prognoses (HR, 2.70; 95 % CI, 1.66-4.39, p < 0.001). For craniocaudal extent comparison, patients with IPF with PPFE-like lesions below the level of the carina had significantly poorer prognoses than those without PPFE-like lesions (p = 0.001, overall survival 53.1 and 80.6, respectively). CONCLUSION: PPFE-like lesions are common in patients with IP, and their characteristics were not significantly different among all forms of IP, except idiopathic PPFE. The broad extent of PPFE-like lesions is an important predictor of prognosis in patients with IPF.

A threshold dosage of estrogen for male-to-female sex reversal in the Glandirana rugosa frog.

Steroid hormones play very important roles in gonadal differentiation in many vertebrate species. Previously, we have determined a threshold dosage of testosterone (T) to induce female-to-male sex reversal in Glandirana rugosa frogs. Genetic females formed a mixture of testis and ovary, the so-called ovotestis, when tadpoles of G. rugosa were reared in water containing the dosage of T, which enabled us to detect primary changes in the histology of the masculinizing gonads. In this study, we determined a threshold dosage of estradiol-17ß (E2) to cause male-to-female sex reversal in this frog. We observed first signs of histological changes in the ovotestes, when tadpoles were reared in water containing the dosage of E2. Ovotestes were significantly larger than wild-type testes in size. By E2 treatment, male germ cells degenerated in the feminizing testis leading to their final disappearance. In parallel, oocytes appeared in the medulla of the ovotestis and later in the cortex as well. Quantitative polymerase chain reaction analysis revealed that the expression of sex-related genes involved in testis formation was significantly decreased in the ovotestis. In addition, immuno-positive signals of CYP17 that is involved in testis differentiation in this frog disappeared in the medulla first and then in the cortex. These results suggested that oocytes expanded in the feminizing gonad (ovary) contemporaneously with male germ cell disappearance. Primary changes in the histology of the gonads during male-to-female sex reversal occurred in the medulla and later in the cortex. This direction was opposite to that observed during female-to-male sex reversal in the G. rugosa frog.

A Phylogenetically Distinct Group of Glandirana rugosa Found in Kyushu, Japan.

The Japanese wrinkled frog Glandirana rugosa is separated into five genetically different groups. One group in western Japan is further divided into three subgroups, found in Kyushu, Shikoku, and western Honshu. We collected G. rugosa frogs at 39 sites in Kyushu and determined nucleotide sequences of the mitochondrial 12S and 16S rRNA genes for phylogenetic analysis. Unexpectedly, we found a group of frogs in southeastern Kyushu that did not cluster with any of the pre-existing five groups of G. rugosa on the phylogenetic trees. The frogs in the new group and G. rugosa in Kyushu were externally similar, but there were a few significant differences in morphological features between the two populations. In addition, we observed significant differences in the frogs' calls . Thus, the group of the frogs in southeastern Kyushu may represent a new candidate species in the genus Glandirana. We discuss the possibility of a new species.

Blood flow modification might prevent secondary rupture of multiple pancreaticoduodenal artery arcade aneurysms associated with celiac axis stenosis.

A pancreaticoduodenal artery arcade aneurysm (PDAA) is rare and often associated with celiac axis stenosis by the median arcuate ligament. Although rupture risk of the PDAA is not related to its size, treatment guidelines are absent. Here we describe a 59-year-old woman with multiple ruptured PDAAs associated with celiac axis stenosis who was successfully treated with coil embolization. As follow-up computed tomography revealed rapid expansion of residual PDAAs and new gastric artery dissection, median arcuate ligament resection was followed by aorta-common hepatic artery bypass, which resulted in aneurysmal regression. Blood flow modification might prevent secondary rupture of PDAA associated with celiac axis stenosis.

Melatonin is a potential drug for the prevention of bone loss during space flight.

Astronauts experience osteoporosis-like loss of bone mass because of microgravity conditions during space flight. To prevent bone loss, they need a riskless and antiresorptive drug. Melatonin is reported to suppress osteoclast function. However, no studies have examined the effects of melatonin on bone metabolism under microgravity conditions. We used goldfish scales as a bone model of coexisting osteoclasts and osteoblasts and demonstrated that mRNA expression level of acetylserotonin O-methyltransferase, an enzyme essential for melatonin synthesis, decreased significantly under microgravity. During space flight, microgravity stimulated osteoclastic activity and significantly increased gene expression for osteoclast differentiation and activation. Melatonin treatment significantly stimulated Calcitonin (an osteoclast-inhibiting hormone) mRNA expression and decreased the mRNA expression of receptor activator of nuclear factor κB ligand (a promoter of osteoclastogenesis), which coincided with suppressed gene expression levels for osteoclast functions. This is the first study to report the inhibitory effect of melatonin on osteoclastic activation by microgravity. We also observed a novel action pathway of melatonin on osteoclasts via an increase in CALCITONIN secretion. Melatonin could be the source of a potential novel drug to prevent bone loss during space flight.

Magnetic compression anastomosis for the complete dehiscence of hepaticojejunostomy in a patient after living-donor liver transplantation.

BACKGROUND: Magnetic compression anastomosis (MCA) is a minimally invasive method of anastomosis that does not involve a surgical procedure in patients with stricture, obstruction, or dehiscence of anastomosis after surgery. We experienced a case of complete dehiscence of bilioenteric anastomosis that was successfully treated by MCA. CASE PRESENTATION: A 55-year-old woman received ABO-incompatible right-lobe living-donor liver transplantation with hepaticojejunostomy for the right anterior duct (RAD) and right posterior duct (RPD). Nineteen days after the operation, bilious and bloody discharge was detected from the abdominal drain. We performed an emergency operation and found that the anastomosis was completely dehiscent. We placed bile drainage catheters into the stumps of the RAD and RPD. She repeatedly experienced cholangitis after the surgery, so we added percutaneous transhepatic cholangial drainage (PTCD) tubes. We decided to treat the complete dehiscence of anastomosis by MCA. One year after the liver transplantation, we performed MCA for the RAD. The bilioenteric fistula was completed 21 days after MCA, and the magnets were retrieved by double-balloon endoscopy. Two months later, MCA for the RPD was also performed by the same procedure. The bilioenteric fistula was not completely established, so we performed double-balloon endoscopy and pulled the magnets down 47 days after MCA for the RAD. The internal/external bile drainage tubes were then left in place to maintain the bilioenteric fistula. Twelve months after MCA for the RAD and 19 months after MCA for the RPD, we removed the tubes without any complications. CONCLUSION: Magnetic compression anastomosis for stricture, obstruction, or dehiscence of the anastomosis after living-donor liver transplantation was an effective and safe procedure.

Nanos3 of the frog Rana rugosa: Molecular cloning and characterization.

Nanos is expressed in the primordial germ cells (PGCs) and also the germ cells of a variety of organisms as diverse as Drosophila, medaka fish, Xenopus and mouse. In Nanos3-deficient mice, PGCs fail to incorporate into the gonad and the size of the testis and ovary is thereby dramatically reduced. To elucidate the role of Nanos in an amphibian species, we cloned Nanos3 cDNA from the testis of the R. rugosa frog. RT-PCR analysis showed strong expression of Nanos3 mRNA in the testis of adult R. rugosa frogs, but expression was not sexually dimorphic during gonadal differentiation. In Nanos3-knockdown tadpoles produced by the CRISPR/Cas9 system, the number of germ cells decreased dramatically in the gonads of both male and female tadpoles before sex determination and thereafter. This was confirmed by three dimensional imaging of wild-type and Nanos3 knockdown gonads using serial sections immunostained for Vasa, a marker specific to germ cells. Taken together, these results suggest that Nanos3 protein function is conserved between R. rugosa and mouse.

Participation of androgen and its receptor in sex determination of an amphibian species.

INTRODUCTION: In the Japanese frog Rana (R.) rugosa the androgen receptor (AR) gene on the W chromosome (W-AR) is barely expressed. Previously we showed that incomplete female-to-male sex-reversal occurred in Z-AR transgenic female frogs. To date, however, there is no report showing that AR with androgens can determine genetically programed male sex fate in any vertebrate species. Here, we examined whether AR together with androgens functions as a sex determinant in an amphibian species. METHODS: To examine whether complete female-to-male sex-reversal occurs in R. rugosa frogs, we produced AR-transgenic (Tg) and -knockdown (KD) female R. rugosa frogs by the I-SceI meganuclease-mediated gene trap and CRISPR/Cas9 system, respectively. AR-Tg and -KD tadpoles were reared in water containing testosterone (T) at 0 to 7.1 ng/ml. Frozen sections were prepared from the gonads of metamorphosed frogs and immunostained for laminin, Vasa, Pat1a, CYP17 and AR. We also employed PCR analysis to examine Dmrt1, Pat1a and CYP17 expression in the gonads of KD and placebo-KD female frogs. RESULTS: Complete female-to-male sex-reversal occurred in the AR-Tg ZW female frogs when a low dosage of T was supplied in the rearing water of tadpoles. However, no sex-reversal was observed in AR-KD ZW female frogs when the gonads were treated with dosages of T high enough to induce complete female-to-male sex-reversal even in wild type frogs. DISCUSSION: These results suggest that AR with its androgen ligand functions as a male sex-determinant in the ZW type R. rugosa frogs.

Origin of sex chromosomes in six groups of Rana rugosa frogs inferred from a sex-linked DNA marker.

Each vertebrate species, as a general rule, has either the XX/XY or ZZ/ZW chromosomes by which sex is determined. However, the Japanese Rana (R.) rugosa frog is an exception, possessing both sex-determining combinations within one species, varying with region of origin. We collected R. rugosa frogs from 104 sites around Japan and South Korea and determined the nucleotide sequences of the mitochondrial 12S ribosomal RNA gene. Based on the sequences, R. rugosa frogs were divided into four groups from Japan and one from South Korea. The ZZ/ZW type is reportedly derived from the XX/XY type, although recently a new ZZ/ZW type of R. rugosa was reported. However, it still remains unclear from where the sex chromosomes in the five groups of this species were derived. In this study, we successfully isolated a sex-linked DNA maker and used it to classify R. rugosa frogs into several groupings. From the DNA marker as well as from nucleotide analysis of the promoter region of the androgen receptor (AR) gene, we identified another female heterogametic group, designated, West-Central. The sex chromosomes in the West-Central originated from the West and Central groups. The results indicate that a sex-linked DNA marker is a verifiable tool to determine the origin of the sex chromosomes in R. rugosa frogs in which the sex-determining system has changed, during two independent events, from the male to female heterogamety.

A Threshold Dosage of Testosterone for Female-to-Male Sex Reversal in Rana rugosa Frogs.

Androgens play a critical role in testicular differentiation in many species of vertebrates. While female-to-male sex reversal can be induced by testosterone (T) in some species of amphibians, the mechanism still remains largely unknown even at the histological level. In this study, we determined a threshold dosage of T to induce female-to-male sex reversal in the Japanese frog Rana (R.) rugosa. Tadpoles were allowed to metamorphose into frogs with T present in the rearing water. At 0.2 ng/mL T, female frogs formed tissue comprising a mixture of ovary and testis, the so-called ovotestis, the size of which was significantly smaller than the wild-type ovary. Histological changes occurring in the oocytes of T-treated ovaries induced oocyte degeneration in the masculinizing ovaries leading to their final disappearance. In parallel, many germ cells emerged in the cortex of the ovotestis and, later, in the medulla as well. RT-PCR analysis revealed upregulated expression of CYP17 and Dmrt1 but not 17ßHSD in the ovotestis, and downregulation of Pat1a expression. Furthermore, immunohistology revealed CYP17-positive signals in the cortex of the masculinizing ovary, spreading throughout the whole area as the testis developed. These results indicate that oocytes are sensitive to T in the ovary of R. rugosa and that male-type germ cells expand in the masculinizing gonad (testis) contemporaneous with oocyte disappearance.

Structural changes in female-to-male sex-reversing gonads of Rana RUGOSA.

The phenotypic sex of many species of amphibians is subject to reversal by steroid hormones. The mechanism of this process, however, still remains largely unknown. As a step toward understanding the histological changes during sex reversal in amphibians, we analyzed two- and three-dimensional (2D and 3D) structures of sex-reversing gonads in Rana rugosa frogs. 2D views revealed that many oocytes in the wild-type ovary disappeared during female-to-male sex-reversal concomitant with the emergence of Vasa-positive small germ cells. Some of the germ cells were labeled with BrdU. BrdU-positive germ cells were few in the testosterone (T) treated ovaries at days 8 and 16, which resembled wild-type ovaries. Basement membranes became disrupted by day 24 in T-treated ovaries. However, the membranes were later reconfigured into testis-like gonadal structures 40 days after T treatment. 3D imaging of the sex-reversing gonad using serial immunostained sections showed that germ cells were organized in linear fashion extending out from where the sex-reversing gonad attached to the mesorchium 24 days after T treatment. Germ cells were increased in number by 40 days and were localized to the cortex of the gonads. In a T-untreated testis at day 24, many germ cells were distributed throughout the cortex except in the central space, while the efferent duct ran between two sheets of the mesorchium. These results, taken together, suggest that the mesorchium plays an important role in the organization of testicular structure. This is the first report showing germ cell ontogeny and organization in the female-to-male sex-reversing gonad in a vertebrate species.

Cost-Effectiveness Analysis of Percutaneous Sclerotherapy for Venous Malformations.

PURPOSE: To assess cost-effectiveness of sclerotherapy for venous malformations (VMs) to improve patient quality of life (QOL). MATERIALS AND METHODS: This prospective study enrolled 28 patients with symptomatic VMs who underwent sclerotherapy. EuroQol-5 Dimension (EQ-5D) and Short-Form 36 (SF-36) Health Survey were used to measure health-related QOL. Questionnaires were collected before and 1, 3, 6, and 12 months after sclerotherapy. Quality-adjusted life years (QALYs) were calculated using EQ-5D score as a measure of health utility. Medical costs obtained from the hospital accounting system and other costs of staff, drugs, materials, and angiographic equipment were calculated for each procedure. Cost-effectiveness was analyzed using incremental cost-effectiveness ratio (ICER) as the medical cost/gain of QALYs. RESULTS: Median EQ-5D scores improved from 0.768 (range, 0.705-1) to 1 (range, 0.768-1) after 6 months (P = .023) and 1 (range, 0.768-1) after 12 months (P = .063). The gain of QALYs at 12 months was 0.043. The mean medical cost was ¥281,228 ($2,337). The pain group (baseline bodily pain scale of SF-36 score < 70) showed greater improvement in median EQ-5D score, from 0.705 (range, 0.661-0.768) to 0.768 (range, 0.705-1) after 6 months (P = .041) and 0.768 (range, 0.768-1) after 12 months (P = .049). ICER at 12 months was ¥6,600,483 ($54,840) in the overall group and decreased to ¥3,998,113 ($33,218) in the pain group, < ¥6,000,000 ($49,850), threshold for acceptance of a public health benefit in Japan, even accounting for 50% increase in costs. CONCLUSIONS: Sclerotherapy was cost-effective for improving QOL for symptomatic VMs, especially for patients with moderate to severe pain.

Patient satisfaction after sclerotherapy of venous malformations in children.

BACKGROUND: We have introduced and performed percutaneous sclerotherapy on pediatric patients, and information regarding the mid- and long-term results after percutaneous treatment of peripheral venous malformations is necessary to counsel patients and their parents about the outcome of the therapy. This study was designed to retrospectively evaluate the long-term satisfaction of pediatric patients following percutaneous sclerotherapy for venous malformations (VMs). METHODS: A total of 53 children younger than 16 years of age with VMs who underwent sclerotherapy were included in this study. Self-assessment questionnaires regarding the treatment effectiveness and patients' satisfaction were sent to 50 of 53 patients. Sclerotherapy was performed using 3% polidocanol, absolute ethanol, or 5% ethanolamine oleate (EO). RESULTS: The median numbers of sessions per patient was 2.0 (range, 1-12), and the median follow-up time was 1.8 years (range, 6months-8.3years). Forty-two patients (84%) returned the questionnaire. The most frequent symptom was swelling (95%, 40/42) before sclerotherapy. After treatment, patients felt less pain (82%, 23/28), functional limitation (78%, 14/18), swelling (70%, 28/40), and cosmetic disfigurement (59%, 13/22). None of the patients responded "worse" for any symptoms, and 30 patients (71%) reported being "very satisfied" or "satisfied" with the treatment. CONCLUSION: Percutaneous sclerotherapy of VMs was safe and effective for relieving symptoms in our pediatric patients, and many of them were satisfied with the outcomes.

Molecular cloning and characterization of oocyte-specific Pat1a in Rana rugosa frogs.

The Pat1 gene is expressed in the immature oocytes of Xenopus, and is reportedly involved in regulating the translation of maternal mRNAs required for oocyte-maturation. However, it is still unknown when Pat1a first appears in the differentiating ovary of amphibians. To address this issue, we isolated the full-length Pat1a cDNA from the frog Rana rugosa and examined its expression in the differentiating ovary of this frog. Among eight different tissues examined, the Pat1a mRNA was detectable in only the ovary. When frozen sections from the ovaries of tadpoles at various stages of development were immunostained for Vasa-a germ cell-specific protein-and Pat1a, Vasa-immunopositive signals were observed in all of the germ cells, whereas Pat1a signals were confined to the growing oocytes (50-200 µm in diameter), and absent from small germ cells (<50 µm in diameter). Forty days after testosterone injection into tadpoles to induce female-to-male sex-reversal, Pat1a-immunoreactive oocytes had disappeared completely from the sex-reversed gonad, but Vasa-positive small germ cells persisted. Thus, Pat1a would be a good marker for identifying the sexual status of the sex-reversing gonad in amphibians. In addition, fluorescence in situ hybridization analysis showed Pat1a to have an autosomal locus, suggesting that Pat1a transcription is probably regulated by a tissue-specific transcription factor in R. rugosa.

Molecular cloning and characterization of anti-Müllerian hormone (AMH) from the Japanese wrinkled frog, Rana rugosa.

The role of anti-Müllerian hormone (AMH) during gonad development has been studied extensively in many species of mammal, bird, reptile, and fish but remains unresolved in amphibians. In male mammalian embryos, Sox9 activates AMH expression, which initiates regression of the Müllerian ducts. However, Sox9 (Sry-related HMG box 9) is unlikely to initiate AMH in chicken, because AMH precedes Sox9 expression in this species. To clarify whether AMH is involved in testicular differentiation in amphibians, we cloned the full-length AMH cDNA from the Japanese wrinkled frog, Rana rugosa. The AMH gene, which appears to be autosomal, is exclusively expressed in the testis of adult frog among 8 different tissues examined; Sertoli cells are probably responsible for its expression. AMH expression was found in the undifferentiated gonad of both male and female tadpoles, increasing in the differentiating testis. Moreover, we observed consensus binding sites for Sox9 in the 5'-flanking region of the AMH gene. Sox9 stimulated statistically significant AMH expression in luciferase reporter assays when coexpressed in Xenopus kidney-derived A6 cells. However, Sox9 expression showed no sexual dimorphism when AMH expression was up-regulated in the developing testis. These results, taken together, suggest that AMH is probably involved in testicular differentiation in R. rugosa, although an additional, perhaps tissue-specific, transcription factor may be required for the regulation of AMH transcription.

Percutaneous sclerotherapy for venous malformations in the extremities: clinical outcomes and predictors of patient satisfaction.

The purpose of this study is to retrospectively evaluate the clinical outcomes and to identify the predictors ofpatient satisfaction after percutaneous sclerotherapy for venous malformations (VMs) in the extremities. A totalof 48 patients with VMs in the extremities over 10 years of age underwent sclerotherapy to relieve symptoms, such as pain, swelling, functional limitations, and cosmetic problems. Self-assessment questionnaires were sentto rate the degree of symptom improvement and level of satisfaction. Clinical and imaging data from medicalrecords were analyzed to obtain information about VMs and sclerotherapy. The predictors for patientsatisfaction were determined by univariate and multivariate analysis of clinical variables. Forty patients (meanage, 28.2 years; range, 11-69 years) responded to the survey. Sixteen patients had VMs in the upper extremities, and 24 patients had VMs in the lower extremities. In 12 patients (30%), adjacent bone change was seen. After amean of 2.6 (range 1-10) sclerotherapy sessions, good response to pain, swelling, dysfunction, and cosmeticproblems was obtained in 83%, 74%, 79%, and 50% of patients, respectively. Thirty-two patients (80%) weresatisfied with their outcomes. On univariate analysis, absence of adjacent bone change, maximum diameter (<6.7 cm), and number of sclerotherapy sessions (<3) were significantly associated with patient satisfaction.Multivariate analysis revealed absence of adjacent bone change (odds ratio, 7.56; 95% confidence interval, 1.02-55.8) as an independent predictor for satisfaction. Thus, adjacent bone change significantly portended adissatisfied patient. In conclusion, percutaneous sclerotherapy was effective to relieve symptoms of VMs in theextremities, and most patients were satisfied with the outcomes. However, adjacent bone change was asignificant predictor of patient dissatisfaction.

Embolic effects of transcatheter mesenteric arterial embolization with microspheres on the small bowel in a dog model.

PURPOSE: To determine the arterial distribution and ischemic effects of various particle sizes after transcatheter embolization of the small bowel in a dog model. MATERIALS AND METHODS: In 10 dogs, selective microsphere embolization was performed in six branches of the superior mesenteric artery. Microspheres were allocated into three size ranges (100-300 µm, 300-500 µm, and 500-700 µm) and four volume concentrations (0.625%, 1.25%, 2.5%, and 5%). For each size and volume concentration, embolization was performed of five branches at the origin of the last arcade. The distribution of microspheres and the range of ischemic changes of mucosa were evaluated histologically. Angiograms were categorized into two groups: group A, only the vasa recta nonopacified; group B, the last arcade or more proximal branches nonopacified. RESULTS: Microspheres sized 100-300 µm penetrated into intramural arteries and 500-700 µm microspheres mainly blocked arteries in the mesentery. There was a significant difference among three sizes in terms of the locations within the vasculature (P < .0001). The larger volume and the smaller size resulted in more ischemia. The range of ischemic changes among three sizes and among four volume concentrations was significantly different (P = .004 and P < .0001, respectively). The range of ischemic changes with 500-700 µm microspheres in group B was significantly greater than in group A (0% in group A vs 83% in group B, P = .001). CONCLUSIONS: In a dog model, embolization of the small bowel limited to the vasa recta with the use if 500-700 µm microspheres reduced the range of ischemic changes.