Current Organizations / Institutes

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Previous Organizations / Institutes

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


Byung Kyu Ahn has a total of 52 co-authors. Here are the top co-authors by number of shared publications:


Latest Publications

  • Extraintestinal manifestations in Korean patients with inflammatory bowel disease: A nationwide population-based study from 2005 to 2017

    by Sung Sil Park, Yun Jin Kim, Byung Kyu Ahn

    Background: Extraintestinal manifestations (EIMs) significantly contribute to morbidity in individuals with inflammatory bowel disease (IBD); however, population-based East Asian data remain limited. We evaluated EIM burden in a nationwide Korean IBD cohort. Methods: This nationwide retrospective cohort study was conducted using data from the Korean National Health Insurance Service between 2005 and 2017. Individuals with ulcerative colitis (UC) or Crohn’s disease (CD) were identified using the International Classification of Diseases–10th Edition and rare intractable disease codes. EIM incidence, associated risk factors, interval from IBD diagnosis to EIM onset, and trends by sex and age were examined. Results: Among 69 414 individuals with IBD (48 689 UC, 20 725 CD), 42.23% developed at least 1 EIM. Dermatologic manifestations were the most common (17.02%), followed by musculoskeletal (16.36%), hepatopancreaticobiliary (15.48%), and ophthalmologic (7.83%) manifestations. Low socioeconomic status, smoking history, female sex, and higher Charlson Comorbidity Index scores independently correlated with EIM development in UC (hazard ratios of 2.14, 1.18, 1.15, and 1.08, respectively) and CD (hazard ratios of 1.98, 1.20, 1.18, and 1.09, respectively). Most EIMs developed within 4 to 6 years postdiagnosis, with musculoskeletal EIMs occurring earliest (median 42.9 months [interquartile range: 10.3-89.5 months]). Annual EIM incidence increased steadily over time across all age groups. Conclusions: EIMs affected 42.23% of Korean individuals with IBD, most frequently appearing 4 to 6 years postdiagnosis. Low socioeconomic status, smoking history, female sex, and higher Charlson Comorbidity Index scores consistently correlated with EIM occurrence, and incidence increased steadily over time, highlighting the need for sustained, personalized monitoring and timely intervention.

  • Open Access

    Absence of AMPK expression is an independent risk factor for stage II/III colorectal cancer recurrence

    by Hyun Seok Goh, Sung Sil Park, Hyun Sung Kim, Byung Kyu Ahn

  • Open Access

    Low MTUS1 Protein Expression Is Associated with Poor Survival in Patients with Colorectal Adenocarcinoma

    by Hosub Park, Seungyun Jee, Hwangkyu Son, Hyebin Cha, Seongsik Bang, Byung Kyu Ahn, Jaekyung Myung, Seungsam Paik, Hyunsung Kim

    Introduction: Microtubule-associated tumor suppressor 1 (MTUS1) is a novel tumor suppressor protein involved in cell proliferation, migration, and tumor growth. MTUS1 is thought to be downregulated in various human cancers and associated with poor prognosis. We evaluated the clinicopathologic significance and prognostic value of MTUS1 in colorectal adenocarcinoma. Methods: Immunohistochemical staining for MTUS1 was performed on tissue microarrays of 393 colorectal adenocarcinoma cases, and MTUS1 staining was classified into high- and low-expression groups. Then, we investigated the correlations between MTUS1 protein expression and various clinicopathological parameters and patient survival. Results: MTUS1 protein was expressed at various grade levels in the cytoplasm of tumor cells, which showed loss or decreased expression of MTUS1. A total of 253 cases (64.4%) were classified into the low MTUS1 protein expression group and 140 cases (35.6%) into the high MTUS1 expression group. A low level of MTUS1 protein significantly correlated with tumor size (p = 0.047), histological grade (p < 0.001), lymphovascular invasion (p < 0.001), perineural invasion (p = 0.047), and lymph node metastasis (p < 0.001). Survival analyses showed that patients with low MTUS1 protein expression had worse overall survival (p = 0.007, log-rank test) and worse recurrence-free survival (p = 0.019, log-rank test) than those with high MTUS1 expression. Conclusions: Low MTUS1 protein expression is associated with adverse clinicopathological characteristics and poor survival outcomes in patients with colorectal adenocarcinoma. These results suggest that MTUS1 functions as a tumor suppressor in colorectal adenocarcinoma and could be a potential prognostic biomarker.


  • The usefulness of the status of extranodal tumor extension as a factor that can predict the recurrence of stage III colorectal cancer

    by Sang Hoon Lee, Hyunsung Kim, Seung Sam Paik, Won Moo Lee, Kang Hong Lee, Byung Kyu Ahn

    Background: Extranodal tumor extension (ENTE) is considered a poor prognostic factor in colorectal cancer (CRC). This study aimed to investigate the risk factors for recurrence according to ENTE status in stage III CRC. Methods: We retrospectively evaluated 169 consecutive stage III CRC patients. All patients underwent a curative resection between 2005 and 2010. The presence or absence of ENTE was assessed in the resected lymph nodes. Results: ENTE was observed in 65 (38.5%). Recurrence occurred in 38 patients (22.5%) and was more frequent (p = .041) in the ENTE (+) group. Disease-free survival (p = .016) was significantly shorter in the ENTE (+) group than in the ENTE (−) group. In a univariable analysis, recurrence was associated with vascular invasion (p = .006), perforation (p = .024) in the ENTE (−) group and perforation (p = .048) in the ENTE (+) group. In a Cox’s regression test, vascular invasion (p = .014) and the higher ratio of metastatic lymph nodes/total removed lymph nodes (MLN/TLN) (0.009) in the ENTE (−) group and perforation (p = .025) in the ENTE (+) group were independent risk factors of recurrence. Conclusions: Vascular invasion and the higher ratio of MLN/TLN in ENTE (−) patients and perforation in ENTE (+) patients were independent risk factors of recurrence.


  • Higher visceral fat area/subcutaneous fat area ratio measured by computed tomography is associated with recurrence and poor survival in patients with mid and low rectal cancers

    by Kang Hong Lee, Bo-Kyeong Kang, Byung Kyu Ahn

    Obesity is thought to influence postoperative complications and recurrence of mid and low rectal cancer (MLRC) because of intraoperative technical difficulties. However, few reports have described the relationship between obesity indices and the clinical outcomes of MLRC. This study aimed to investigate the association between visceral obesity on computed tomography (CT) and oncolofical outcomes after surgery for MLRC and identify the obesity index that most accurately reflects clinical outcomes.


  • Loss of APAF-1 expression is associated with early recurrence in stage I, II, and III colorectal cancer

    by Byung Kyu Ahn, Sung Hoo Kim, Seung Sam Paik, Kang Hong Lee

    Purpose Apoptotic protease activating factor-1 (APAF-1) is a key regulator in the mitochondrial apoptotic pathway and an important diagnostic and therapeutic biomarker. Loss of APAF-1 expression has been observed in various tumors including colorectal cancer. The aim of our study was to evaluate the relationship between loss of APAF-1 expression and early recurrence of stage I–III colorectal cancer. Methods We investigated 165 out of 492 patients who had undergone curative resection for colorectal cancer between 1991 and 2001. Sixty-one patients (37.0 %) had early recurrence within 1 year after surgery. Tissue microarrays were used for immunohistochemical detection of APAF-1. Results The mean age of patients with recurrence was 58 years (range, 24–85); 88 (53.3 %, 88/165) were male. APAF-1 was expressed in 32 (19.4 %, 32/165) cases and was not expressed in 133 (80.6 %, 133/165). In univariate analysis, early recurrence significantly correlated with loss of APAF-1 expression (p = 0.017), tumor stage (p = 0.005), N category (p = 0.001), and lymphatic invasion (p = 0.008). In a logistic regression model, loss of APAF-1 expression (p = 0.015, 95 % CI = 1.280–10.063) and N category (p = 0.001, 95 % CI = 0.004–0.739) proved to be independent risk factors associated with early recurrence. In patients with lymph node metastasis, early recurrence was more frequent in the APAF-1-negative group than in the APAF-1-positive group (46.2 % (54/117) vs. 22.2 % (6/27), p = 0.023). Conclusions Loss of APAF-1 expression is associated with early recurrence in stage I–III colorectal cancer, suggesting that APAF-1 may have clinical value as a predictive marker of early recurrence.


  • Open Access

    Chronic inflammatory demyelinating polyneuropathy-like neuropathy as an initial presentation of Crohn’s disease

    by Suji Kim, Seok-Jae Kang, Ki-Wook Oh, Byung Kyu Ahn, Hang Lak Lee, Dong Soo Han, Kiseok Jang, Young Seo Kim

    Chronic inflammatory demyelinating polyneuropathy (CIDP) is a rare complication of Crohn's disease (CD), and it is uncertain whether it is associated with CD itself or with its treatment. We describe a case of CIDP-like neuropathy as an initial symptom of CD. The neurologic symptoms of the patient which responded partially to intravenous immunoglobulin (IVIG) recovered after resection of the appendiceal CD. A 17-year-old male had experienced three separate attacks of motor weakness and paresthesia of all four extremities over a period of 7 months. The electrophysiologic findings revealed a demyelinating sensory-motor polyneuropathy which was compatible with CIDP. However, repeated intravenous IVIG (2 g/kg) treatment gave only a partial response. Four days after the last discharge, he was diagnosed as appendiceal CD after surgical resection of a periappendiceal abscess. His neurologic symptoms and electrophysiologic findings recovered without any maintenance therapy. CIDP-like neuropathy can be an initial presentation of CD, and recovery of the CIDP symptoms may result from resection of the CD. Clinicians should be aware of the possibility of CD in patients with intractable CIDP symptoms.


  • What is the optimal time for laparoscopic cholecystectomy in gallbladder empyema?

    by Yong Jin Kwon, Byung Kyu Ahn, Hwon Kyum Park, Kwang Soo Lee, Kyeong Geun Lee

    With the accumulating experience in laparoscopic surgery, early laparoscopic cholecystectomy (LC) is increasingly offered for acute cholecystitis. However, early LC without percutaneous transhepatic gallbladder drainage (PTGBD) for gallbladder empyema is still believed to be unsafe. The purpose of this study was to determine the optimal time for LC in gallbladder empyema. A retrospective analysis was carried out of patients who underwent LC without PTGBD for gallbladder empyema between August 2007 and December 2010. All cases were confirmed by biopsy. The patients were divided into two groups on the basis of a cutoff of 72 h. LC for gallbladder empyema was performed without PTGBD in 61 patients during the study period. The overall conversion rate was 6.6 %. Based on the 72 h cutoff, there were 33 patients in the early group and 28 in the delayed group. There were no significant differences between early and late patients with respect to operation duration (75.5 vs. 71.4 min, p = 0.537), postoperative hospital stay (4.2 vs. 3.3 days, p = 0.109), conversion rate (12.1 vs. 0 %, p = 0.118), and complication rate (12.1 vs. 3.6 %, p = 0.363). However, the early group had a significantly shorter total hospital stay (5.3 vs. 8.7 days, p = 0.001). Early LC without PTGBD is safe and feasible for gallbladder empyema and is associated with a low conversion rate. Delayed LC for gallbladder empyema has no advantages and results in longer total hospital stays. LC should be performed as soon as possible within 72 h after admission to decrease length of hospital stay.