T. Çolak - Academia.edu (original) (raw)

Papers by T. Çolak

Transplantation Proceedings, 2011

Insulin resistance (IR) is an early and very strong predictor of posttransplantation diabetes mel... more Insulin resistance (IR) is an early and very strong predictor of posttransplantation diabetes mellitus as well as an important cardiovascular risk factor even in the absence of hyperglycemia. Patients after renal transplantation are insulin resistant compared with a control group with similar demographic characteristics. The aim of this study was to determine the frequency of IR in renal allograft patients without glucose disorders, to correlate IR indexes with the doses of immunosuppressive medications, and to examine other risk factors, such as age, obesity, and antihypertensive therapy used. One hundred six patients who received a kidney transplant at Baskent University Hospital between 1992 and 2006 were enrolled the study. IR was diagnosed by using homeostasis model assessment (HOMA); 53.8% of the patients (n ϭ 57) had IR. HOMA-IR was correlated with age, body mass index, and waist-hip ratio (P values .004, .001, and .000, respectively). In regression analysis, only waist-hip ratio was significantly associated with HOMA-IR.

Transplantation Proceedings, 2011

Background. There are limited data about ambulatory blood pressure monitoring (ABPM) in renal tra... more Background. There are limited data about ambulatory blood pressure monitoring (ABPM) in renal transplantation patients. We sought to evaluate the clinical outcomes, and success of antihypertensive therapy based upon ABPM data. Methods. We performed ABPM on 82 recipients between 2000 and 2006 including 27 females of overall age of 37.3 Ϯ 10.8 years who displayed mild to moderate hypertension (HT). We evaluated demographic blood pressure, proteinuria, and laboratory values, as well as renal resistive index (RRI) estimated by Doppler ultrasonography.

Transplantation Proceedings, 2005

Amyloidosis is characterized by the accumulation of an amorphous material in various organs and t... more Amyloidosis is characterized by the accumulation of an amorphous material in various organs and tissues secondary to a variety of inflammatory, immune, infectious, and hereditary diseases. Since 1975, our transplantation team has performed 1470 renal transplantations. Between 1985 and July 2004, among 1159 kidney transplantations, 953 (82.3%) were from living donors and 206 (17.7%) from cadaveric donors. There were 32 recipients (28 men, 4 women; mean age, 31.4 Ϯ 1.7 years; range, 21 to 48 years) with amyloidosis, including, 28 (87.5%) who received grafts from living donors and 4 (12.5%) from cadaveric donors. Amyloidosis was secondary to familial Mediterranean fever in 22 (68.7%) patients and rheumatoid arthritis in 1 (3.1%). The remaining 9 (28.1%) patients had primary amyloidosis. The mean follow-up time was 51.2 Ϯ 5.7 months (range, 2-124 months). Mean HLA mismatch rate was 2.2 Ϯ 1. Twenty-six (81.2%) patients are alive at this time with functioning grafts, and a mean serum creatinine value of 2.1 Ϯ 1.5 ng/dL. The 1-and 5-year patient and graft survival rates were 90.6% and 84.3%, and 81.2% and 68.7%, respectively. We conclude that patients with amyloidosis may undergo kidney transplantation safely expecting outcomes similar to those patients who receive transplantations for other reasons.

Transplantation Proceedings, 2006

Background. There are numerous recent reports on the use of lamivudine for hepatitis B virus (HBV... more Background. There are numerous recent reports on the use of lamivudine for hepatitis B virus (HBV) infection after renal transplantation. However, the optimal strategy (prophylactic, preemptive, or salvage approach) for starting lamivudine treatment in this patient group has not been determined. The aim of this study was to assess how the timing of lamivudine therapy affected the HBV serological status and the transaminase levels in renal allograft recipients with chronic HBV infection. Methods. We investigated outcomes for patients who were seropositive for hepatitis B surface antigen (HBsAg) and underwent transplantation before or after October 2004 (the date our institution implemented a prophylactic lamivudine treatment strategy against HBV). The data included serum liver enzyme levels and polymerase chain reaction (PCR) screening results for HBV-DNA in serum. Results. Fifteen patients (11 before October 2004, four after October 2004) were included in the study. Preoperatively all patients had normal transaminases levels and 2 of 15 patients had detectable HBV-DNA on PCR. Eight of the 15 total HBsAg-positive patients in our series were not placed on lamivudine at the time of renal transplantation. Half of those who were not treated initially showed transaminase elevations in the first year of follow-up requiring lamivudine therapy at that time. In contrast, all seven individuals who received lamivudine at the time of transplantation were negative for HBV-DNA throughout the follow-up. Conclusion. To prevent viral replication in HBsAg-positive patients who are scheduled for renal transplantation, it is best to initiate lamivudine therapy before or immediately after transplantation. Address reprint requests to

Transplantation Proceedings, 2008

Antithymocyte globulin (ATG) is a polyclonal antibody used in renal transplantation for preventio... more Antithymocyte globulin (ATG) is a polyclonal antibody used in renal transplantation for prevention and treatment of acute rejection. In this study we have presented the outcomes of 23 cases treated with ATG due to steroid-resistant acute rejection episodes in 17 male and 6 female recipients. Sixteen transplantations were performed from cadaver donors and the other 7 from living-related donors. The mean recipient age was 31.9 Ϯ 9 years and the mean donor age was 56.3 Ϯ 10.8 years. ATG treatment was administered in doses of 3-5 mg/kg/d for 10 or 14 days. All patients received the same premedication before the ATG treatment; we did not encounter any ATG-related side effects. ATG doses were adjusted according to the T-lymphocyte levels. All recipients were followed up for infectious complications, for graft function, and for immunologic parameters of CD3 levels, CD4 levels, CD3/CD4 ratios, lymphocyte, and polymorphonuclear leukocyte numbers. According to the Banff criteria introduced in 1997, 4 patients displayed humoral rejection: 3 had type 3; 5 had type 2; and 11 had type 1 acute rejection episodes. Nine patients developed infectious complication during the follow-up. Three had pulmonary aspergillosis; 2 had cytomegalovirus infection; and 4 had bacterial infections. One patient who experienced aspergillosis died with a functioning graft, and the remaining 8 patients were treated successfully. Graft function improved in 19 (83%) cases. The other 4 patients returned to hemodialysis. Mean creatinine levels decreased from 4 Ϯ 1.7 to 2.1 Ϯ 0.2 mg/dL. We did not observe any relationship between the immunologic parameters and infectious complications. In conclusion, although ATG is a powerful drug to treat steroid-resistant acute rejection episodes, there was no precise way to monitor the intensity of immunosuppression to prevent infectious complications.

Tissue Antigens, 2002

The role of HLA-antigens in susceptibility to hepatitis C virus (HCV) infection is still being de... more The role of HLA-antigens in susceptibility to hepatitis C virus (HCV) infection is still being debated. We analyzed HLA phenotype frequencies in two major ethnic groups, namely Egyptian and Saudi nationals. The Egyptian group included 110 patients of whom 55 were HCV positive and the other 55 were HCV negative (control group). The Saudi group included 146 HCV-positive patients and 122 HCV-negative individuals (control group). The results for the Egyptian population revealed increased frequencies of some HLA phenotypes and decreased frequencies of others but without any statistically significant difference. In contrast, in the Saudi population, the HLA-A19 phenotype was significantly increased in the HCVpositive patients when compared with the control group, while significantly decreased frequencies were found for HLA-B8, HLA-DRI and HLA-DR3. Our data suggest that there was no significant association between the HLA phenotypes and the susceptibility to HCV infection among the Egyptian population, while the overall data of the Saudi population seem to indicate that the expression of particular HLA-alleles could be associated with the susceptibility or resistance to the HCV infection. Further studies on larger numbers of patients are needed to support the role of the HLA system in HCV infection. A total of 108 HCV-positive patients underwent renal transplantation at the Jeddah Kidney Center, and the results were compared with 100 age-and sex-matched controls. Graft survival at 36 months was 82% and 86% for the HCV positive and control subjects, respectively, while the patient survival rate was, respectively, 90% and 91%. Our data suggest that the outcome, at least in the short-term, of renal transplantation in HCV-positive patients is very good.

Transplantation Proceedings, 2011

Background. Chronic kidney disease (CKD) is a common problem in long-term survivors after liver t... more Background. Chronic kidney disease (CKD) is a common problem in long-term survivors after liver transplantation (LT). It is important to identify and correct risk factors that negatively affect kidney function. The purpose of this study was to delineate the risk factors associated with progressive kidney dysfunction after OLT. Methods. We analyzed 50 recipients (10 female, 40 male) of overall age of 44 Ϯ 13 year who were all Ն18 years old and underwent first LT between 1999 and 2005. Patient-related risk factors were evaluated for renal failure at 3 and 5 years after transplantation. We evaluated parameters of demographic data, laboratory values, daily proteinuria, and renal resistive index (RRI) by Doppler ultrasonography. CKD was defined as a sustained decrease in estimated glomerular filtration rate (eGFR). Patients were divided into 3 groups according to the change in eGFR from the baseline value: group 1, stable eGFR (no change from baseline); group 2, Ͻ50% decreased eGFR; and group 3, Ն50% decrease from baseline. eGFR was calculated by using Modification of Diet in Renal Disease (MDRD) formula. Results. At 3 years after LT, GFR negatively correlated with initial Child-Pugh score (r ϭ Ϫ0.42; P Ͻ .01); microalbuminuria (r ϭ Ϫ0.28; P Ͻ .01), and RRI (r ϭ Ϫ0.36; P Ͻ .01). After 5 years, GFR negatively correlated with initial gamma glutamyl transferase (r ϭ Ϫ0.21; P Ͻ .05), PT (r ϭ Ϫ0.29; P Ͻ .05), and RRI (r ϭ Ϫ0.32; P Ͻ .01). Pretransplantation direct bilirubin levels were significantly correlated with GFR decrease at 3 years (P ϭ .05). At 5 years of follow-up, smoking (P Ͻ .05), baseline alanine aminotransferase (P ϭ .03) and serum triglyceride (P Ͻ .01) levels significantly correlated with eGFR decrease. Pretransplantation serum creatinine levels were stratified into normal versus high groups. Patients with increased basal serum creatinine levels displayed shorter survivals than those with normal creatinine levels, namely, median values of 21 Ϯ 3.9 months versus 14 Ϯ 2.4 months, log rank test: P Ͻ .05). Conclusion. Renal function after liver transplantation show sustained impairment in certain patients. In the short term the main risk factors for renal detoriation were severity of liver disease before LT, microalbuminuria, and renal perfusion. In the long term, smoking and dyslipidemia were the main predictors of CKD. Patients with high basal serum creatinine values were at increased risk of mortality.

Transplantation Proceedings, 2011

Insulin resistance (IR) is an early and very strong predictor of posttransplantation diabetes mel... more Insulin resistance (IR) is an early and very strong predictor of posttransplantation diabetes mellitus as well as an important cardiovascular risk factor even in the absence of hyperglycemia. Patients after renal transplantation are insulin resistant compared with a control group with similar demographic characteristics. The aim of this study was to determine the frequency of IR in renal allograft patients without glucose disorders, to correlate IR indexes with the doses of immunosuppressive medications, and to examine other risk factors, such as age, obesity, and antihypertensive therapy used. One hundred six patients who received a kidney transplant at Baskent University Hospital between 1992 and 2006 were enrolled the study. IR was diagnosed by using homeostasis model assessment (HOMA); 53.8% of the patients (n ϭ 57) had IR. HOMA-IR was correlated with age, body mass index, and waist-hip ratio (P values .004, .001, and .000, respectively). In regression analysis, only waist-hip ratio was significantly associated with HOMA-IR.

Transplantation Proceedings, 2011

Background. There are limited data about ambulatory blood pressure monitoring (ABPM) in renal tra... more Background. There are limited data about ambulatory blood pressure monitoring (ABPM) in renal transplantation patients. We sought to evaluate the clinical outcomes, and success of antihypertensive therapy based upon ABPM data. Methods. We performed ABPM on 82 recipients between 2000 and 2006 including 27 females of overall age of 37.3 Ϯ 10.8 years who displayed mild to moderate hypertension (HT). We evaluated demographic blood pressure, proteinuria, and laboratory values, as well as renal resistive index (RRI) estimated by Doppler ultrasonography.

Transplantation Proceedings, 2005

Amyloidosis is characterized by the accumulation of an amorphous material in various organs and t... more Amyloidosis is characterized by the accumulation of an amorphous material in various organs and tissues secondary to a variety of inflammatory, immune, infectious, and hereditary diseases. Since 1975, our transplantation team has performed 1470 renal transplantations. Between 1985 and July 2004, among 1159 kidney transplantations, 953 (82.3%) were from living donors and 206 (17.7%) from cadaveric donors. There were 32 recipients (28 men, 4 women; mean age, 31.4 Ϯ 1.7 years; range, 21 to 48 years) with amyloidosis, including, 28 (87.5%) who received grafts from living donors and 4 (12.5%) from cadaveric donors. Amyloidosis was secondary to familial Mediterranean fever in 22 (68.7%) patients and rheumatoid arthritis in 1 (3.1%). The remaining 9 (28.1%) patients had primary amyloidosis. The mean follow-up time was 51.2 Ϯ 5.7 months (range, 2-124 months). Mean HLA mismatch rate was 2.2 Ϯ 1. Twenty-six (81.2%) patients are alive at this time with functioning grafts, and a mean serum creatinine value of 2.1 Ϯ 1.5 ng/dL. The 1-and 5-year patient and graft survival rates were 90.6% and 84.3%, and 81.2% and 68.7%, respectively. We conclude that patients with amyloidosis may undergo kidney transplantation safely expecting outcomes similar to those patients who receive transplantations for other reasons.

Transplantation Proceedings, 2006

Background. There are numerous recent reports on the use of lamivudine for hepatitis B virus (HBV... more Background. There are numerous recent reports on the use of lamivudine for hepatitis B virus (HBV) infection after renal transplantation. However, the optimal strategy (prophylactic, preemptive, or salvage approach) for starting lamivudine treatment in this patient group has not been determined. The aim of this study was to assess how the timing of lamivudine therapy affected the HBV serological status and the transaminase levels in renal allograft recipients with chronic HBV infection. Methods. We investigated outcomes for patients who were seropositive for hepatitis B surface antigen (HBsAg) and underwent transplantation before or after October 2004 (the date our institution implemented a prophylactic lamivudine treatment strategy against HBV). The data included serum liver enzyme levels and polymerase chain reaction (PCR) screening results for HBV-DNA in serum. Results. Fifteen patients (11 before October 2004, four after October 2004) were included in the study. Preoperatively all patients had normal transaminases levels and 2 of 15 patients had detectable HBV-DNA on PCR. Eight of the 15 total HBsAg-positive patients in our series were not placed on lamivudine at the time of renal transplantation. Half of those who were not treated initially showed transaminase elevations in the first year of follow-up requiring lamivudine therapy at that time. In contrast, all seven individuals who received lamivudine at the time of transplantation were negative for HBV-DNA throughout the follow-up. Conclusion. To prevent viral replication in HBsAg-positive patients who are scheduled for renal transplantation, it is best to initiate lamivudine therapy before or immediately after transplantation. Address reprint requests to

Transplantation Proceedings, 2008

Antithymocyte globulin (ATG) is a polyclonal antibody used in renal transplantation for preventio... more Antithymocyte globulin (ATG) is a polyclonal antibody used in renal transplantation for prevention and treatment of acute rejection. In this study we have presented the outcomes of 23 cases treated with ATG due to steroid-resistant acute rejection episodes in 17 male and 6 female recipients. Sixteen transplantations were performed from cadaver donors and the other 7 from living-related donors. The mean recipient age was 31.9 Ϯ 9 years and the mean donor age was 56.3 Ϯ 10.8 years. ATG treatment was administered in doses of 3-5 mg/kg/d for 10 or 14 days. All patients received the same premedication before the ATG treatment; we did not encounter any ATG-related side effects. ATG doses were adjusted according to the T-lymphocyte levels. All recipients were followed up for infectious complications, for graft function, and for immunologic parameters of CD3 levels, CD4 levels, CD3/CD4 ratios, lymphocyte, and polymorphonuclear leukocyte numbers. According to the Banff criteria introduced in 1997, 4 patients displayed humoral rejection: 3 had type 3; 5 had type 2; and 11 had type 1 acute rejection episodes. Nine patients developed infectious complication during the follow-up. Three had pulmonary aspergillosis; 2 had cytomegalovirus infection; and 4 had bacterial infections. One patient who experienced aspergillosis died with a functioning graft, and the remaining 8 patients were treated successfully. Graft function improved in 19 (83%) cases. The other 4 patients returned to hemodialysis. Mean creatinine levels decreased from 4 Ϯ 1.7 to 2.1 Ϯ 0.2 mg/dL. We did not observe any relationship between the immunologic parameters and infectious complications. In conclusion, although ATG is a powerful drug to treat steroid-resistant acute rejection episodes, there was no precise way to monitor the intensity of immunosuppression to prevent infectious complications.

Tissue Antigens, 2002

The role of HLA-antigens in susceptibility to hepatitis C virus (HCV) infection is still being de... more The role of HLA-antigens in susceptibility to hepatitis C virus (HCV) infection is still being debated. We analyzed HLA phenotype frequencies in two major ethnic groups, namely Egyptian and Saudi nationals. The Egyptian group included 110 patients of whom 55 were HCV positive and the other 55 were HCV negative (control group). The Saudi group included 146 HCV-positive patients and 122 HCV-negative individuals (control group). The results for the Egyptian population revealed increased frequencies of some HLA phenotypes and decreased frequencies of others but without any statistically significant difference. In contrast, in the Saudi population, the HLA-A19 phenotype was significantly increased in the HCVpositive patients when compared with the control group, while significantly decreased frequencies were found for HLA-B8, HLA-DRI and HLA-DR3. Our data suggest that there was no significant association between the HLA phenotypes and the susceptibility to HCV infection among the Egyptian population, while the overall data of the Saudi population seem to indicate that the expression of particular HLA-alleles could be associated with the susceptibility or resistance to the HCV infection. Further studies on larger numbers of patients are needed to support the role of the HLA system in HCV infection. A total of 108 HCV-positive patients underwent renal transplantation at the Jeddah Kidney Center, and the results were compared with 100 age-and sex-matched controls. Graft survival at 36 months was 82% and 86% for the HCV positive and control subjects, respectively, while the patient survival rate was, respectively, 90% and 91%. Our data suggest that the outcome, at least in the short-term, of renal transplantation in HCV-positive patients is very good.

Transplantation Proceedings, 2011

Background. Chronic kidney disease (CKD) is a common problem in long-term survivors after liver t... more Background. Chronic kidney disease (CKD) is a common problem in long-term survivors after liver transplantation (LT). It is important to identify and correct risk factors that negatively affect kidney function. The purpose of this study was to delineate the risk factors associated with progressive kidney dysfunction after OLT. Methods. We analyzed 50 recipients (10 female, 40 male) of overall age of 44 Ϯ 13 year who were all Ն18 years old and underwent first LT between 1999 and 2005. Patient-related risk factors were evaluated for renal failure at 3 and 5 years after transplantation. We evaluated parameters of demographic data, laboratory values, daily proteinuria, and renal resistive index (RRI) by Doppler ultrasonography. CKD was defined as a sustained decrease in estimated glomerular filtration rate (eGFR). Patients were divided into 3 groups according to the change in eGFR from the baseline value: group 1, stable eGFR (no change from baseline); group 2, Ͻ50% decreased eGFR; and group 3, Ն50% decrease from baseline. eGFR was calculated by using Modification of Diet in Renal Disease (MDRD) formula. Results. At 3 years after LT, GFR negatively correlated with initial Child-Pugh score (r ϭ Ϫ0.42; P Ͻ .01); microalbuminuria (r ϭ Ϫ0.28; P Ͻ .01), and RRI (r ϭ Ϫ0.36; P Ͻ .01). After 5 years, GFR negatively correlated with initial gamma glutamyl transferase (r ϭ Ϫ0.21; P Ͻ .05), PT (r ϭ Ϫ0.29; P Ͻ .05), and RRI (r ϭ Ϫ0.32; P Ͻ .01). Pretransplantation direct bilirubin levels were significantly correlated with GFR decrease at 3 years (P ϭ .05). At 5 years of follow-up, smoking (P Ͻ .05), baseline alanine aminotransferase (P ϭ .03) and serum triglyceride (P Ͻ .01) levels significantly correlated with eGFR decrease. Pretransplantation serum creatinine levels were stratified into normal versus high groups. Patients with increased basal serum creatinine levels displayed shorter survivals than those with normal creatinine levels, namely, median values of 21 Ϯ 3.9 months versus 14 Ϯ 2.4 months, log rank test: P Ͻ .05). Conclusion. Renal function after liver transplantation show sustained impairment in certain patients. In the short term the main risk factors for renal detoriation were severity of liver disease before LT, microalbuminuria, and renal perfusion. In the long term, smoking and dyslipidemia were the main predictors of CKD. Patients with high basal serum creatinine values were at increased risk of mortality.