Impact of minimum contrast media volumes during percutaneous coronary intervention for chronic total occlusion lesion.

Contrast media exposure is associated with contrast-induced nephropathy (CIN) following percutaneous coronary intervention (PCI) of chronic total occlusion (CTO). Aim of this study is to assess the utility of minimum contrast media volume (CMV ≤ 50 mL) during CTO-PCI for CIN prevention in patients with chronic kidney disease (CKD). We extracted data from the Japanese CTO-PCI expert registry; 2863 patients with CKD who underwent CTO-PCI performed from 2014 to 2020 were divided into two groups: minimum CMV (n = 191) and non-minimum CMV groups (n = 2672). CIN was defined as an increased serum creatinine level of ≥ 25% and/or ≥ 0.5 mg/dL compared with baseline levels within 72 h of the procedure. In the minimum CMV group, the CIN incidence was lower than that in the non-minimum CMV group (1.0% vs. 4.1%; p = 0.03). Patient success rate was higher and complication rate was lower in the minimum CMV group than in the non-minimum CMV group (96.8% vs. 90.3%; p = 0.02 and 3.1% vs. 7.1%; p = 0.03). In the minimum CMV group, the primary retrograde approach was more frequent in the case of J-CTO = 1,2 and 3-5 groups compared to that in non-minimum CMV-PCI group (J-CTO = 0; 11% vs. 17.7%, p = 0.06; J-CTO = 1; 22% vs. 35.8%, p = 0.01; J-CTO = 2; 32.4% vs. 46.5%, p = 0.01; and J-CTO = 3-5; 44.7% vs. 80.0%, p = 0.02). Minimum CMV-PCI for CTO in CKD patients could reduce the incidence of CIN. The primary retrograde approach was observed to a greater extent in the minimum CMV group, especially in cases of difficult CTO.

[A Case of Pancreatic Cancer That Developed Peritoneal Recurrence after Radical Surgery following Neoadjuvant Chemoradiation Therapy(NACRT)with Pathological Complete Response(pCR)].

A 71-year-old woman was diagnosed with a tumor in the pancreatic head on CT imaging, which was performed as a close examination of an exacerbation of diabetes mellitus. The pancreatic tumor was diagnosed as resectable pancreatic cancer, and after preoperative adjuvant chemoradiotherapy, pancreatoduodenectomy was performed as a radical surgery. There were no residual tumor cells in the resected specimen histopathologically, and the patient was judged to have a pathological complete response(pCR). Six months of postoperative adjuvant chemotherapy was administered, but peritoneal recurrence was observed at 20 months postoperatively, and the patient is currently undergoing treatment for recurrence. There have been other reports of recurrence even after pCR was achieved with preoperative treatment, so it is important to follow up carefully, keeping in mind that pancreatic cancer is a latent systemic disease.

The safety and feasibility of retrograde balloon aortic valvuloplasty using the INOUE-BALLOON with severe aortic stenosis.

In the transcatheter aortic valve implantation (TAVI) era, the indications for balloon aortic valvuloplasty (BAV) are increasing. Previously, the INOUE-BALLOON® (IB) was used only for antegrade BAV, but recently, it has also been used for retrograde BAV. However, the safety and feasibility of retrograde BAV using an IB are not fully understood. In this study, we investigated the safety and feasibility of retrograde BAV using an IB in elderly Japanese patients with severe aortic stenosis (AS). We compared 39 cases of retrograde BAV using an IB performed from June 2018 to September 2020 and 34 cases of antegrade BAV using an IB performed from August 2013 to May 2018. The total number of complications was lower in retrograde BAV than in antegrade BAV (p = 0.020). The procedure time was significantly shorter in retrograde BAV than in antegrade BAV (p < 0.001), and the maximum balloon size and number of balloon inflations were smaller in retrograde BAV than in antegrade BAV (p = 0.002 and p < 0.001, respectively). There was no significant difference in the degree of improvement in the aortic valve area or ejection fraction between retrograde and antegrade BAV. In conclusion, the present study showed the safety and feasibility of retrograde BAV using an IB in elderly Japanese patients with severe AS compared with antegrade BAV using an IB.

Predictors of prolonged guidewire manipulation time for native coronary chronic total occlusion percutaneous coronary intervention via primary antegrade approach.

OBJECTIVES: This study aimed to identify the predictive factors for the guidewire manipulation time (GWMT) of ≥20 and 30 min for chronic total occlusion-percutaneous coronary intervention (CTO-PCI) via the primary antegrade approach (PAA). BACKGROUND: Selection of primary retrograde approach (PRA) and the optimal timing to switch from antegrade to retrograde approach for coronary CTO-PCI is still debatable. METHODS: Using the Japanese CTO-PCI expert registry data, we selected and analyzed 4461 patients who underwent CTO-PCI via PAA alone. The considerable lesion/anatomical factors for GWMT ≥20 and 30 min were analyzed. The risks of prolonged GWMT ≥20 and 30 min were stratified as easy, intermediate, difficult, and very difficult according to the multivariate analysis. RESULTS: Nine lesion/anatomical characteristics (blunt stump, side branch at proximal cap, bifurcation at the exit point, calcification, tortuosity, occlusion length ≥ 20 mm, reattempt, nonleft anterior descending artery (nonleft anterior descending artery [LAD]), and tandem CTO) were independent predictors of GWMT ≥20 min (all p < 0.05). Excluding the nonLAD and tandem CTO, the same factors of GWMT ≥20 min correlated with GWMT ≥30 min (all p < 0.05). The distributions were increased in easy, intermediate, difficult, and very difficult subsets of GWMT ≥20 min (58.3%, 77.2%, 89.1%, and 100%) and GWMT ≥30 min (47.5%, 69.2%, 83.9%, and 100%). CONCLUSIONS: These predictive factors of prolonged GWMT should be assessed before CTO-PCI via PAA and when considering an adequate timing to switch the retrograde or PRA if clinically available.

Assessment of reattempted percutaneous coronary intervention strategy for chronic total occlusion after prior failed procedures: Analysis of the Japanese CTO-PCI Expert Registry.

OBJECTIVES: We aimed to investigate strategies for reattempted percutaneous coronary interventions (PCIs) for chronic total occlusions (CTOs) by highly skilled operators after a failed attempt. BACKGROUND: Development of complex techniques and algorithms has been standardized for CTO-PCI. However, there is no appropriate strategy for CTO-PCI after a failed procedure. METHOD: From 2014 to 2016, the Japanese CTO-PCI Expert Registry included 4,053 consecutive CTO-PCIs (mean age: 66.8 ± 10.9 years; male: 85.6%; Japanese CTO [J-CTO] score: 1.92 ± 1.15). Initial outcomes and strategies for reattempted CTO-PCIs were evaluated and compared with first-attempt CTO-PCIs. RESULTS: Reattempt CTO-PCIs were performed in 820 (20.2%) lesions. The mean J-CTO score of reattempt CTO-PCIs was higher than that of first-attempt CTO-PCIs (2.86 ± 1.03 vs. 1.68 ± 1.05, p < .001). The technical success rate of reattempt CTO-PCIs was lower than that of first-attempt CTO-PCIs (86.7% vs. 90.8%, p < .001). Regarding successful CTO-PCIs, the strategies comprised antegrade alone (reattempt: 36.1%, first attempt: 63.8%), bidirectional approach (reattempt: 54.4%, first attempt: 30.3%), and antegrade approach following a failed bidirectional approach (reattempt: 9.4%, first attempt: 5.4%). Parallel wire technique, intravascular ultrasound guide crossing, and bidirectional approach technique were frequently performed in reattempt CTO-PCIs. Reattempt CTO-PCIs showed higher rates of myocardial infarction (2.1% vs. 0.9%, p < .001) and coronary perforation (6.9% vs. 4.2%, p = .002) than first-attempt CTO-PCIs. CONCLUSIONS: The technical success rate of reattempt CTO-PCIs is lower than that of first-attempt CTO-PCIs. However, using more complex strategies, the success rate of reattempt CTO-PCI can be improved by highly skilled operators.

[FOLFIRINOX for Locally Advanced and Recurrent Pancreatic Cancer with UGT1A1 *6 and or UGT1A1*28 Polymorphisms-A Report of Two Cases].

Treatment containing FOLFIRINOX was planned to be administered to a 51-year-old man with locally advanced pancreatic cancer as second-line chemotherapy and to a 66-year-old woman with recurrent pancreatic cancer as third-line chemotherapy in their treatments. Since both patients were revealed to harbor UGT1A1 polymorphisms, which were highly associated with irinotecan-induced toxicity(the former: UGT1A1 *6/*28, the latter: UGT1A1*6/*6), there was no alternative hopeful treatment other than FOLFIRINOX for them. Therefore, FOLFIRINOX was administered very carefully. Although both patients showed Grade 4 neutropenia during the initial course, it was controllable with G-CSF administration and following stepwise reduction of the irinotecan dose. Severe diarrhea and other adverse events were not observed in both cases. Since the determined regimen of FOLFIRINOX for patients with high-risk UGT1A1 polymorphisms has not been developed yet, it would be critical to accumulate and review an experience of FOLFIRINOX administration for these patients.

[A Case of Long-Term Survival of the Pancreatic Tail Cancer with the Concomitant Small Liver Metastasis].

We hereby report a case of long-term survival of the pancreatic tail cancer with a synchronous small liver metastasis. A 62- year-old male with pancreatic tail cancer was incidentally diagnosed with single tiny metastasis in the left medial section of the liver duringthe distal pancreatectomy. The lesion was also resected together with primary lesion. Since then, systemic chemotherapies such as gemcitabine(GEM)plus S-1 combination therapy, GEM alone therapy and S-1 alone therapy had been given to escape from recurrence. However, the recurrences were found in the liver at 21 months after surgery. Left hepatectomy was performed for metastatic lesions. Afterwards, proton radiation therapy was twice performed for the metastatic lesions in the liver which were unable to be removed by surgery alone. Partial resection of transverse colon was also needed to be performed for the bowel obstruction caused by recurrence on the surgical margin of the liver. Systemic chemotherapies includingS -1 therapy, FOLFIRINOX therapy and GEM plus nab-paclitaxel therapy have been continued throughout his entire treatment history after recurrence. He has been keepingin good physical condition with these multidisciplinary therapies, even though 51 months have passed since the first evidence of liver metastasis was diagnosed.

[A Case of Long-Term Survival of Metastatic and Recurrent Duodenal Gastrointestinal Stromal Tumor Treated with Multimodality Managements].

We hereby report a case of long-term survival of metastatic and recurrent duodenal gastrointestinal stromal tumor(GIST) treated with multimodality managements. A 59-year-old man was diagnosed with duodenal GIST and underwent surgical resection of a primary lesion of the duodenum. Since the pathological findings on mitotic rate indicated its high risk of recurrence, the systemic treatment by imatinib mesylate was given shortly after the surgery. Six months later, metastatic lesions being considered to be imatinib-resistant were observed in the remnant liver. Since there were no other drugs available for GISTs in clinic at that time, surgery of central bisegmentectomy with partial resection of the liver was performed to eliminate all metastatic lesions. However, recurrences had been repeatedly diagnosed afterward. In response to them, four more surgery for recurrent liver or peritoneal tumors, two transcatheter arterial chemoembolizations(TACE)and one radiofrequency ablation(RFA)were performed on the basis of its resectability. Sunitinib malate had been given since it was approved for imatinib-resistant GISTs in clinic. Eventually, as long as 99 months had passed since we observed the first evidence of the resistance to imatinib mesylate when he died from the GIST.

Independent predictors of retrograde failure in CTO-PCI after successful collateral channel crossing.

OBJECTIVES: To evaluate factors for predicting retrograde CTO-PCI failure after successful collateral channel crossing. BACKGROUND: Successful guidewire/catheter collateral channel crossing is important for the retrograde approach in percutaneous coronary intervention (PCI) for chronic total occlusion (CTO). METHODS: A total of 5984 CTO-PCI procedures performed in 45 centers in Japan from 2009 to 2012 were studied. The retrograde approach was used in 1656 CTO-PCIs (27.7%). We investigated these retrograde procedures to evaluate factors for predicting retrograde CTO-PCI failure even after successful collateral channel crossing. RESULTS: Successful guidewire/catheter collateral crossing was achieved in 77.1% (n = 1,276) of 1656 retrograde CTO-PCI procedures. Retrograde procedural success after successful collateral crossing was achieved in 89.4% (n = 1,141). Univariate analysis showed that the predictors for retrograde CTO-PCI failure were in-stent occlusion (OR = 1.9829, 95%CI = 1.1783 - 3.3370 P = 0.0088), calcified lesions (OR = 1.9233, 95%CI = 1.2463 - 2.9679, P = 0.0027), and lesion tortuosity (OR = 1.5244, 95%CI = 1.0618 - 2.1883, P = 0.0216). On multivariate analysis, lesion calcification was an independent predictor of retrograde CTO-PCI failure after successful collateral channel crossing (OR = 1.3472, 95%CI = 1.0614 - 1.7169, P = 0.0141). CONCLUSIONS: The success rate of retrograde CTO-PCI following successful guidewire/catheter collateral channel crossing was high in this registry. Lesion calcification was an independent predictor of retrograde CTO-PCI failure after successful collateral channel crossing. Devices and techniques to overcome complex CTO lesion morphology, such as lesion calcification, are required to further improve the retrograde CTO-PCI success rate. © 2016 Wiley Periodicals, Inc.

Short-term effects of arthrotomy with and without infrapatellar fat pad resection on the normal canine stifle.

OBJECTIVE: To investigate the short-term effects of infrapatellar fat pad (IFP) resection in normal dogs. STUDY DESIGN: Experimental in vivo study. ANIMALS: Five normal adult female beagle dogs. METHODS: The IFP was resected via arthrotomy in the left stifle joint (experimental side) while the right stifle underwent arthrotomy alone (sham side). An orthopedic examination was performed every week for 4 weeks and synovial fluid was analyzed before and 4 weeks after the procedure. The ratio of the length of the patellar ligament to the patellar length (L:P) was calculated on a lateral radiograph of the stifle before, 2 and 4 weeks after the procedure. Patellar depth (PD) and the contact area (CA) between the femur and patella were calculated from computed tomographic images taken at 3 different stifle angles (extended, flexed, hyperflexed) before, immediately after, and 4 weeks following the procedure. The dogs were euthanatized 4 weeks after the procedure for macroscopic and microscopic evaluation of the patellofemoral joint. RESULTS: No difference was found between treatment groups throughout the study. No evidence of postoperative osteoarthritis was detected in any of the dogs. Orthopedic examinations, radiographs, and synovial fluid analyses remained within normal limits. Most PD, but not CA measurements, increased with time in both joints and at all stifle angles. CONCLUSIONS: Excision of the IFP subsequent to medial arthrotomy did not result in any measurable changes in the canine patellofemoral joint when compared with medial arthrotomy alone after 4 weeks of follow-up.

Complications during retrograde approach for chronic coronary total occlusion: Sub-analysis of Japanese multicenter registry.

OBJECTIVES: This study was performed to determine the complications occurring during retrograde percutaneous coronary intervention (PCI) for chronic total occlusion (CTO) based on analysis of the multicenter, prospective, nonrandomized Retrograde Summit registry. BACKGROUND: Retrograde PCI for CTO has improved treatment success rates, but several complications related to the retrograde approach have been reported, including collateral channel injury and donor artery injury due to their use as retrograde roots. METHODS: This registry included data from 1,166 patients who underwent retrograde PCI for CTO in 28 Japanese centers between January 2009 and December 2011. RESULTS: Overall procedure success and retrograde procedure success were achieved in 985 (84.5%) and 838 (71.9%) of the 1,166 patients, respectively. In-hospital major adverse cardiac and cerebrovascular events (MACCE) occurred in 18 (1.5%) of the 1,166 patients. With regard to complications related to the retrograde approach, channel injury occurred in 111 (9.5%) of the 1,166 patients, but treatment was required in only 24 (2.1%) patients and subsequent cardiac tamponade occurred in only 4 (0.3%) patients. Donor artery problems occurred in only 10 (0.9%) of the 1,166 patients. In sub-analysis regarding the types of collateral channels, the septal channel was significantly safer than epicardial channel because of the lower frequency of non-Q-wave myocardial infarction (non-QMI) and channel injury requiring treatment. CONCLUSIONS: The MACCE rate during retrograde PCI for CTO determined from the Retrograde Summit registry was low and the frequency of complications related to the retrograde approach was acceptable. © 2015 Wiley Periodicals, Inc.

[A Case of Axillary Lymph Node Metastases from Distal Bile Duct Cancer].

A 67-year-old man suffered from obstructive jaundice due to distal bile duct cancer. He underwent surgery after percutaneous biliary drainage and did not received adjuvant chemotherapy afterwards. Two years after surgery, some subcutaneous nodules were detected in the left axilla and the lateral chest on enhanced CT imaging. The nodules were diagnosed as metachronous distant metastases from bile duct cancer based on pathological findings. He was treated postoperatively with S-1 and new lesions have not been detected during the 3 months after the surgery. Surgical intervention in combination with chemotherapy might be beneficial in selected patients with recurrent bile duct cancer.

[A Case of AFP and PIVKA- II Producing Gastric Cancer Presenting with Metachronous Multiple Liver Metastases].

A 55-year old man underwent distal gastrectomy with lymphadenectomy for gastric cancer(T1N0M0, Stage I A). Six months after the radical operation, he presented with multiple liver metastases. Based on immunohistochemical examination, he was diagnosed with AFP-producing gastric cancer and metachronous liver metastases. He underwent a surgery to remove the liver metastases. Two months after the surgery, recurrent tumors were found in the lung and remnant liver. He received chemotherapy(S-1/CDDP and CPT-11/CDDP)for the recurrent tumor and lived for 15 months after the surgical intervention.

Retrograde Coronary Chronic Total Occlusion Intervention (JR-CTO) Score: From the Japanese CTO-PCI Expert Registry.

BACKGROUND: Despite the effectiveness of the retrograde approach for chronic total occlusion (CTO) lesions, there are no standardized tools to predict the success of retrograde percutaneous coronary intervention (PCI). OBJECTIVES: The aim of this study was to develop a prediction tool to identify CTO lesions that will achieve successful retrograde PCI. METHODS: This study evaluated data from 2,374 patients who underwent primary retrograde CTO-PCI and were enrolled in the Japanese CTO-PCI Expert Registry between January 2016 and December 2022 (NCT01889459). All observations were randomly assigned to the derivation and validation cohorts at a 2:1 ratio. The prediction score for guidewire failure in retrograde CTO-PCI was determined by assigning 1 point for each factor and summing all accrued points. RESULTS: The JR-CTO score (moderate-severe calcification, tortuosity, Werner collateral connection grade ≤1, and nonseptal collateral channel) demonstrated a C-statistic for guidewire failure of 0.72 (95% CI: 0.67-0.76) and 0.71 (95% CI: 0.64-0.77) in the derivation and validation cohorts, respectively. Patients with lower scores had higher guidewire and technical success rates and decreased guidewire crossing time and procedural time (P < 0.01). CONCLUSIONS: The JR-CTO (Japanese Retrograde Chronic Total Occlusion) score, a simple 4-item score that predicts successful guidewire crossing in patients undergoing retrograde CTO-PCI, has the potential to support clinical decision-making for the retrograde approach.

Tissue-Engineered Hepatocyte Sheets Supplemented with Adipose-Derived Stem Cells.

The ability to engineer biologically viable hepatocytes and tissue matrices with long-term functional maintenance has attracted considerable interest in the fields of hepatocyte transplantation and liver tissue engineering. Here, newly developed hepatocyte sheets supplemented with adipose-derived stem cells (ADSCs) were evaluated to assess the effects of ADSCs on hepatocyte function and engraftment into the subcutaneous space. Eight-week-old male C57BL/6J mice were used as donors, and 6-week-old male C.B-17/Icr-scid/scid mice were used as recipients. Hepatocyte-ADSC composite sheets were developed using temperature-responsive culture dishes. Hepatocyte viability in the hepatocyte-ADSC composite sheets was evaluated in an in vitro assay, and the outcome of subcutaneous transplantation of the sheet was evaluated. Hepatocyte viability was sustained in the hepatocyte-ADSC composite sheets in vitro. Albumin secretion was significantly higher (p = 0.015) in the hepatocytes of the hepatocyte-ADSC composite sheets (70.5 µg/mL) than in hepatocyte-only sheets (24.0 µg/mL). Cytokine assays showed that hepatocyte growth factor and interleukin-6 were contributed by ADSCs and not hepatocytes, which were not capable of constitutively secreting them. Immunohistochemically, phosphorylated STAT3 and c-MET expression in hepatocytes in the hepatocyte-ADSC composite sheets was significantly higher than that in the hepatocyte-only sheets. Engraftment of the transplanted hepatocyte-ADSC composite sheets was significantly enhanced without pretreatment of the subcutaneous tissue to induce a vascular network. In the hepatocyte-ADSC composite sheets, the viability of the hepatocytes was significantly maintained as the co-cultured ADSCs provided cytokines, enhancing pivotal cell signaling necessary for hepatocyte activity. Impact statement Hepatocyte transplantation is a safe, less invasive bridge treatment for liver transplantation, but its effectiveness is low and transitory. Herein, we introduce newly developed hepatocyte-adipose-derived stem cell composite sheets with improved strength, easier transplantation, and increased hepatocyte viability in the subcutaneous transplantation compared with hepatocyte-only sheets.

Long-term survival of a cow with cervical ectopia cordis.

This study investigated the long-term survival of a calf with cervical ectopia cordis that grew normally, became pregnant, and calved normally. The cow showed normal cardiac function and absence of peripheral circulation abnormalities. This paper documents antemortem characteristics of the affected cow.

Intratumor Abscess in a Posttraumatic Hepatic Inflammatory Pseudotumor Spreading Out of the Liver.

A 45-year-old woman with abdominal pain after minor trauma was referred to our hospital. Computed tomography (CT) showed a hypovascular tumor in the left liver lobe. A tumor biopsy revealed granuloma, although no findings indicated malignancy or infection. A follow-up imaging study showed spread of the hepatic tumor. Her abdominal pain worsened after a second minor trauma. CT revealed an intratumor abscess, and pus overflowed from the patient's umbilicus. The abscess was improved by antibiotics and drainage therapy. In this case, unusual imaging findings and an atypical disease course of a hepatic inflammatory pseudotumor were observed.

A pilot cohort study assessing the feasibility of complete revascularization with balloon pulmonary angioplasty for chronic thromboembolic pulmonary hypertension.

Balloon pulmonary angioplasty improves prognosis by alleviating pulmonary hypertension in patients with chronic thromboembolic pulmonary hypertension, even with incomplete revascularization. However, hypoxia or the requirement for pulmonary vasodilators often remain even after pulmonary hypertension relief. With this cohort study, we aimed to examine whether complete revascularization by additional balloon pulmonary angioplasty on residual lesions, even after pulmonary hypertension relief, could resolve hypoxia or the requirement for pulmonary vasodilators. During complete revascularization with balloon pulmonary angioplasty in 42 patients with chronic thromboembolic pulmonary hypertension, we investigated therapeutic effects at baseline (T1), pulmonary hypertension relief phase (T2), and at 6 months post-final balloon pulmonary angioplasty (T3). The pulmonary hypertension relief phase was defined as the first time that a mean pulmonary artery pressure ≤ 25 mmHg or pulmonary vascular resistance ≤ 240 dyn-s/cm5 was reached in right heart catheterization before balloon pulmonary angioplasty. The partial pressure of oxygen increased progressively over T1, T2, and T3 (59.2±8.5, 69.0±9.7, and 80.0±9.5 mmHg, respectively; P<0.001 T2 vs. T3). Minimum oxygen saturation levels during the 6-minute walk distance test were 87% (81‒89%), 88% (84‒92%), and 91% (89‒93.3%), respectively (P<0.001 T2 vs. T3), with gradual increase in the 6-minute walk distance (346±125 m, 404±90 m, 454±101 m, respectively; P<0.001 T2 vs. T3). The percentages of patients using pulmonary vasodilators (54.8%, 45.2%, 4.8%, respectively; P<0.001 T2 vs. T3) and requiring oxygen therapy (26%, 26%, 7%, respectively; P = 0.008 T2 vs. T3) decreased significantly without hemodynamic exacerbation or major complications. Despite the discontinuation of pulmonary vasodilators, mean pulmonary artery pressure improved (36.0 [31.0‒41.3], 21.4±4.2, 18.5±3.6 mmHg, respectively; P<0.001 T2 vs. T3). Complete revascularization with balloon pulmonary angioplasty beyond pulmonary hypertension relief benefits patients with chronic thromboembolic pulmonary hypertension; it may improve oxygenation and exercise capacity, and reduce the need for pulmonary vasodilators and oxygen therapy.

Evaluation of the susceptibility artifacts and tissue injury caused by implanted microchips in dogs on 1.5 T magnetic resonance imaging.

Performing magnetic resonance imaging (MRI) in patients with a metallic implant raises concern over the potential complications, including susceptibility artifacts, implant migration, and heat injury. The purpose of this study was to investigate these complications in dogs with implanted microchips by evaluating MR images and the histopathological changes after 1.5 Tesla (T) MRI. Five dogs underwent microchip implantation in the cervicothoracic area. One month later, the area was imaged using 1.5T MRI in three dogs. The microchips were removed surgically together with the surrounding tissue in all dogs. There was significant signal loss and image distortion over a wide range around the area where the microchip was implanted. This change was consistent with susceptibility artifacts, which rendered the affected area including the spinal cord undiagnostic. The artifact was more extensive in T2*-weighted images (gradient-echo) and less extensive in proton density-weighted images (fast spin-echo with short echo time). Histopathologically, all microchips were well-encapsulated with granulation tissue, and there were no evidence of migration of microchips. Cell debris and a moderate number of degenerated cells with fibrin were seen in the inner layer of the granulation tissue in each dog that underwent MRI. These changes were very subtle and did not seem to be clinically significant. The results of this study suggest that, in 1.5T MRI, susceptibility artifacts produced by implanted microchips can be marked, although the dogs with implants appeared to be scanned safely.