RTRyohei Takei

Ryohei Takei

*This is an algorithmically generated author record based on publicly available information.

Current Organizations / Institutes

The organizations/institutes from the scholar's latest article

Previous Organizations / Institutes

The organizations / institutes from the scholar's other articles in the past ten years


Ryohei Takei has a total of 57 co-authors. Here are the top co-authors by number of shared publications:


Latest Publications

  • Open Access

    Laparoscopic versus open partial hepatectomy for hepatocellular carcinoma in F4 cirrhosis: A propensity score-matched study of perioperative safety

    by Hiroaki Sugita, Shinichi Nakanuma, Tomokazu Tokoro, Ryohei Takei, Mitsuyoshi Okazaki, Kaichiro Kato, Satoshi Takada, Isamu Makino, Shintaro Yagi

    Hiroaki Sugita, Shinichi Nakanuma, Tomokazu Tokoro, Ryohei Takei, Mitsuyoshi Okazaki, Kaichiro Kato, Satoshi Takada, Isamu Makino, Shintaro Yagi. Ann Hepatobiliary Pancreat Surg -0001;0:. https://doi.org/10.14701/ahbps.26-046

  • Open Access

    Impact of aging on hepatic reserve after preoperative portal vein embolization in hepatectomy for perihilar cholangiocarcinoma

    by Shinichi Nakanuma, Takahiro Ogi, Hiroaki Sugita, Ryosuke Gabata, Tomokazu Tokoro, Ryohei Takei, Kaichiro Kato, Satoshi Takada, Mitsuyoshi Okazaki, Isamu Makino, et al.


  • Open Access

    Assaying ADAMTS13 Activity as a Potential Prognostic Biomarker for Sinusoidal Obstruction Syndrome in Mice

    by Masakazu Saeki, Seiichi Munesue, Yuri Higashi, Ai Harashima, Ryohei Takei, Satoshi Takada, Shinichi Nakanuma, Tetsuo Ohta, Shintaro Yagi, Hidehiro Tajima, et al.

    Sinusoidal obstruction syndrome (SOS) is a serious liver disorder that occurs after liver transplantation, hematopoietic stem cell transplantation, and the administration of anticancer drugs. Since SOS is a life-threatening condition that can progress to liver failure, early detection and prompt treatment are required for the survival of patients with this condition. In this study, female CD1 mice were divided into treatment and control groups after the induction of an SOS model using monocrotaline (MCT, 270 mg/kg body weight intraperitoneally). The mice were analyzed at 0, 12, 24, and 48 h after MCT administration, and blood and liver samples were collected for assays and histopathology tests. SOS was observed in the livers 12 h after MCT injection. In addition, immunohistochemical findings demonstrated CD42b-positive platelet aggregations, positive signals for von Willebrand factor (VWF), and a disintegrin-like metalloproteinase with thrombospondin type 1 motifs 13 (ADAMTS13) in the MCT-exposed liver sinusoid. Although ADAMTS13’s plasma concentrations peaked at 12 h, its enzyme activity continuously decreased by 75% at 48 h and, inversely and proportionally, concentrations in the VWF-A2 domain, in which the cleavage site of ADAMTS13 is located, increased after MCT injection. These findings suggest that the plasma concentration and activity of ADAMTS13 could be useful biomarkers for early detection and therapeutic intervention in patients with SOS.


  • Open Access

    Correction to: Dynamic switch of immunity and antitumor effects of metformin in rat spontaneous esophageal carcinogenesis

    by Ryohei Takei, Tomoharu Miyashita, Satoshi Takada, Hidehiro Tajima, Itasu Ninomiya, Hiroyuki Takamura, Sachio Fushida, Ai Harashima, Seiichi Munesue, Shintaro Yagi, et al.

  • Open Access

    Dynamic switch of immunity and antitumor effects of metformin in rat spontaneous esophageal carcinogenesis

    by Ryohei Takei, Tomoharu Miyashita, Satoshi Takada, Hidehiro Tajima, Itasu Ninomiya, Hiroyuki Takamura, Sachio Fushida, Ai Harashima, Seiichi Munesue, Shintaro Yagi, et al.

    Chronic inflammation contributes to tumor development by creating a local microenvironment that facilitates neoplastic transformation and potentiates the progression of cancer. Esophageal cancer (EC) is an inflammation-associated malignancy with a poor prognosis. The nature of the switch between chronic inflammation of the esophagus and EC-related immunological changes remains unclear. Here, we examined the dynamic alterations of immune cells at different stages of chronic esophagitis, Barrett’s esophagus (BE) and EC using an esophageal spontaneous carcinogenesis rat model. We also investigated the anticancer effects of metformin. To stimulate EC carcinogenesis, chronic gastroduodenal reflux esophagitis via esophagojejunostomy was induced in 120 rats in metformin-treated and non-treated (control) groups. After 40 weeks, BE and EC developed in 96.7% and 63.3% of the control group, and in 66.7% and 23.3% of the metformin-treated group, respectively. Flow cytometric analysis demonstrated that the balance of M1/M2-polarized or phospho-Stat3-positive macrophages, regulatory T, cytotoxic T, natural killer (NK), NK T cells, and Th17 T cells was dynamically changed at each stage of the disease and were resolved by metformin treatment. These findings clarify the immunity in esophageal carcinogenesis and suggest that metformin could suppress this disease by improving the immunosuppressive tumor microenvironment and immune evasion.


  • Open Access

    Pedicled jejunal flap reconstruction for partial duodenectomy: a report of two cases

    by Ryohei Takei, Masashi Hashimoto, Ryosuke Zaimoku, Hirohumi Terakawa, Itsuro Terada, Yuji Tsukioka, Masato Kiriyama

    Conventional jejunal reconstruction procedures for large duodenal defects include jejunal serosal patch repair and duodenojejunostomy and have some risks of postoperative complications. The pedicled jejunal flap is used for reconstruction following laryngopharyngectomy, esophagectomy and other gastrointestinal surgeries. We report two cases of successful closure of duodenal defects after partial duodenectomies by pedicled jejunal flap reconstruction. Case 1: A 72-year-old man was diagnosed with gastrointestinal stromal tumor by esophagogastroduodenoscopy (EGD), endoscopic ultrasound-guided fine needle aspiration biopsy and computed tomography (CT). Case 2: A 63-year-old woman was diagnosed with early duodenal cancer using EGD and CT. Partial duodenectomy and pedicled jejunal flap reconstruction were performed in both patients. A part of the jejunum was formed into a pedicled flap to fit the duodenal defect and duodenojejunal anastomosis was performed. The patients did not report any postoperative gastrointestinal symptoms or abnormal findings during follow-up EGD or upper gastrointestinal radiography.

  • A Case of Strangulation Ileus Due to a Low-Grade Appendiceal Mucinous Neoplasm

    by Ryohei Takei, Keiichiro Kanamoto, Yuta Tamaru, Koki Nojima, Kazuyoshi Mitta, Ryosuke Zaimoku, Ayako Kanamoto, Hirohumi Terakawa, Yuki Higashi, Yuji Tsukioka, et al.

    BACKGROUND Strangulation ileus is caused by external obstruction to the small bowel, which results in ischemia and loss of bowel peristalsis. Low-grade appendiceal mucinous neoplasm (LAMN) is a low-grade adenocarcinoma that arises in the appendix. LAMN is usually asymptomatic but can present with appendiceal rupture and pseudomyxoma peritonei (PMP). This report is of a rare presentation of LAMN with strangulation ileus in a 92-year-old man. CASE REPORT A 92-year-old man was admitted to the emergency room with sudden onset of lower abdominal pain and abdominal distension. Laboratory investigations showed a leukocytosis with a white blood cell (WBC) count of 14.6×10³/μL with 85.5% neutrophils, blood urea nitrogen (BUN) of 26.6 mg/dL, and serum creatinine of 2.6 mg/dL, consistent with acute renal failure. Arterial blood gas analysis showed lactic acidosis (pH of 7.11) with a base excess of -20.8 mmol/L and lactate of 13.7 mmol/L. Abdominal computed tomography (CT) showed ascites and a dilated obstructed closed loop of the distal ileum associated with an external mass (3.9×2.8 cm). An initial diagnosis was of strangulation ileus due to Meckel's diverticulum. Emergency ileocecal resection was performed. Histopathology showed a low-grade mucinous tumor arising from the mucosa of the appendix, consistent with LAMN. At a 13-month follow-up, the patient was well with no tumor recurrence. CONCLUSIONS This report is of a rare case of LAMN that presented as a surgical emergency with strangulation ileus.


  • Open Access

    Recurrent biliary dissemination of colon cancer liver metastasis: a case report

    by Ichiro Onishi, Masato Kayahara, Ryohei Takei, Naoki Makita, Masayoshi Munemoto, Yasumichi Yagi, Atsuhiro Kawashima

    Most colorectal cancer liver metastases form nodules within the hepatic parenchyma, and hepatectomy is the only radical treatment for synchronous metastases. There is concern about intrabiliary tumor growth which may affect the surgical margin, resulting in local recurrence after hepatectomy for colorectal cancer liver metastasis; however, there has been no report of the dissemination in the bile duct after hepatectomy. Here, we report an unusual case of biliary dissemination of colorectal cancer that caused recurrent intrabiliary growth after hepatectomy, and discuss the management of intrabiliary metastasis of colorectal cancer. A 69-year-old Japanese man underwent treatment for liver dysfunctions 3 years after aortic valve replacement. Computed tomography revealed an enhanced tumor within the hilar bile duct and dilatation of the left hepatic duct, typical of hilar cholangiocarcinoma. Endoscopic retrograde cholangiopancreatography revealed tumor shadow in his bile duct, and the cytology confirmed malignant cells in the bile. We performed extended left hepatectomy with bile duct resection; his postoperative course remained good without acute complications. After 3 months postoperatively, he was readmitted for subacute cholangitis and obstructive jaundice. Immediately, percutaneous transhepatic cholangiography drainage was performed, followed by cholangiography that exhibited intrabiliary tumor growth in the remnant liver. On immunohistochemical examination, tumor cells were positive for cytokeratin 20 and CDX2 but negative for cytokeratin 7. Then, computed tomography revealed an enhanced tumor-like lesion at the descending colon. After 3 months, left hemicolectomy was performed. Meanwhile, the percutaneous transhepatic cholangiography drainage fluid turned bloody, which was considered to be bleeding from a residual bile duct tumor. Accordingly, radiotherapy was initiated to prevent tumor bleeding around the hilar bile duct, but, unfortunately, the effects were short-lived, and cholangitis rebooted after 1 month leading to our patient’s death due to septic liver failure. Autopsy revealed a remnant tumor in the bile duct, but no noticeable nodular metastasis was observed, except for a single small metastasis in the lower lobe of the left lung. The intrabiliary growth of metastatic colorectal cancer mimics cholangiocarcinoma occasionally. To date, as the effect of chemotherapy or radiotherapy remains uncertain, the complete resection of a bile duct tumor is the only method which could result in a better prognosis.


  • Open Access

    Adenocarcinoma in a Blind Loop of the Ileum 53 Years After an Ileotransversostomy Procedure

    by Ryohei Takei, Ichiro Onishi, Ryosuke Zaimoku, Naoki Makita, Yasumichi Yagi, Masato Kayahara

    BACKGROUND:Primary small bowel cancer is a rare malignancy; the common histopathological types are carcinoid and adenocarcinoma. Inflammatory bowel diseases and familial adenomatous polyposis are known risk factors for small bowel cancer. Additionall...