Living donor kidney volume as a predictor of graft function: is there a role for proteinuria?

BACKGROUND: The proposed mechanism by which nephron underdosing contributes to graft failure is hyperfiltration damage leading to proteinuria and nephron loss. We evaluated whether proteinuria had an impact on the relationship between graft size and outcome in living donor kidney transplantation. METHODS: We analyzed 69 living donors and their recipients who underwent transplantation between 2003 and 2007. Transplanted kidney volumes were measured by 3-D helical computed tomography scanning. A transplant kidney volume-recipient body weight (Vol/Wt) ratio was calculated for each donor-recipient pair. The subjects were divided into tertiles according to Vol/Wt ratios: low (<2.0), medium (2.0-2.7) and high (>2.7). RESULTS: Recipient glomerular filtration rate (GFR) positively correlated with Vol/Wt ratio at 6, 12, and 24 months posttransplantation (r = .49, P < .001; r = .47, P < .001; r = .42, P < .001, respectively). Mean GFR increased significantly in graded fashion from low to high Vol/Wt ratio groups at 6, 12, and 24 months posttransplantation. Proteinuria did not differ between the three groups during 24 months after transplantation. Upon multivariate analysis, donor age, recipient age, and Vol/Wt ratio showed significant impacts on graft function. CONCLUSION: Vol/Wt ratio displayed a significant independent effect on graft function in living donor kidney transplantation. This close association did not appear to be related to the degree of proteinuria during 24 months.

Proton pump inhibitor omeprazole use is associated with low bone mineral density in maintenance haemodialysis patients.

OBJECTIVE: Limited studies have shown that proton pump inhibitor (PPI) therapy may decrease bone density or insoluble calcium reabsorption through induction of hypochlorhydria. However, PPI therapy may also reduce bone resorption via inhibition of osteoclastic vacuolar proton pumps. The aim of this study was to determine whether the opposing effects of PPI therapy may cause clinically important alterations in bone mineral densitometry (BMD) parameters in maintenance haemodialysis patients. METHODS: Sixty-eight maintenance haemodialysis patients were enrolled in this study. Patients were classified into two groups involving users of PPI therapy (omeprazole 20 mg/day, group 1, n = 36 patients) and non-users of acid suppression drugs (group 2, n = 32 patients). Patients had radius, hip and spine BMD assessed by dual-energy X-ray absorptiometry. RESULTS: The mean duration of PPI therapy with omeprazole was 27 +/- 5 months. The users of PPI therapy had lower values of bone mineral density and T-scores at the anatomical regions than non-users of acid suppression drugs. Serum calcium and phosphate levels, calcium-phosphate product and serum intact parathormone levels and the ratio of users of vitamin D therapy were similar among groups. A mutivariable adjusted odds ratio for lower bone density associated with more than 18 months of omeprazole, when all the potential confounders were considered, was 1.31 in the proximal radius, 0.982 in the femur neck, 0.939 in the trochanter and 1.192 in the lumbal spine. CONCLUSION: The present data suggest that PPI therapy should be cautiously prescribed in maintenance haemodialysis patients, especially with lower BMD values.

Coronary artery calcifications in hemodialysis patients and their correlation with the prevalence of erectile dysfunction.

INTRODUCTION: Our aim in this study was to investigate the prevalence and correlation with coronary artery calcium scores (CACS) and erectile dysfunction (ED) among hemodialysis patients. PATIENTS AND METHODS: Thirty-five male patients with chronic renal failure were selected to participate in this study. All patients underwent examinations for CACS using 16-channel multidetector computed tomography. The presence and severity of ED were determined by calculating the erectile function domain of the self-administered International Index of Erectile Function (IIEF). RESULTS: The patients' ages ranged from 22 to 78 with a mean of 51.6 years. The mean duration of hemodialysis was 75.7 months (range = 12 to 232). Twenty-six patients had a history of one or more systemic diseases. The prevalence of any level of ED was 82.9% for all hemodialysis patients, and severe ED, 40%. The CACS was significantly higher among patients with severe ED (P = .032). The IIEF-5 score was also shown to have a moderate negative correlation with the CACS (r = -.420, P = .012). Age, duration of hemodialysis, body mass index, diabetes mellitus, hypertension, coronary heart diseases, hyperlipidemia, thyroid disease, depression, tobacco consumption, and medication were not associated with the presence of ED (P > .05). CONCLUSION: ED is prevalent in hemodialysis patients. Although many possible factors contribute to ED, the severity of ED increases with greater CACS.

Utility of the Doppler ultrasound parameter, resistive index, in renal transplant histopathology.

BACKGROUND: Doppler ultrasonography is routinely used by many clinicians during long-term follow-up to identify high-risk patients without diagnosing the exact cause of graft dysfunction. Despite a number of studies showing a correlation between intrarenal resistive index (RI) and renal function in patients with kidney diseases, correlations between RI and renal histopathologic characteristics have not been sufficiently evaluated in renal transplant recipients. The aim of this study was to examine this relationship in grafted kidneys. PATIENTS AND METHODS: The intrarenal RI was retrospectively compared with biopsy findings in 28 kidney recipients. All renal biopsy specimens were reviewed by light microscopy and immunofluorescence staining. For glomerulosclerosis, we considered the percentage of glomeruli showing this change; for interstitial fibrosis/tubular atrophy and interstitial infiltration, we graded abnormalities according to the methods of Kliem et al (Kidney Int 49:666, 1996). RESULTS: The percentage of globally sclerosed glomeruli was significantly greater among patients with RI values higher than 0.75 than below this level (23% vs 47%; P = .022). Patients with grade 1 interstitial fibrosis and tubular atrophy (n = 14) showed lower RI values (0.68 +/- 0.03 vs 0.74 +/- 0.06; P = .047) than those with grade 3 fibrosis (n = 12). Similarly, lower RI values (0.66 +/- 0.02 vs 0.73 +/- 0.05; P = .014) were observed among patients with grade 1 (n = 13) compared with grade 3 interstitial infiltration (n = 13). CONCLUSION: RI seemed to provide a prognostic marker for the graft rather than yielding an exact diagnosis of renal graft dysfunction.

Utility of c2 monitoring in prediction of diastolic dysfunction in renal transplant recipients.

BACKGROUND: A number of experimental studies have suggested that cyclosporine (CsA) toxicity induces cardiac modifications which may cause diastolic dysfunction over the course of time. Doppler echocardiography with tissue Doppler imaging (TDI) could consistently detect diastolic dysfunction. The purpose of this study was to assess diastolic dysfunction using C2 monitoring of CsA exposure in stable renal transplant patients. PATIENTS AND METHODS: Seventy-eight kidney recipients including 42 men and 36 women of overall mean age of 52 +/- 9 years were obtained in 47 living and in 31 cases from cadaveric donations over 12 or more months after transplantation using cases from CsA, mycophenolate mofetil, and steroid. C2 levels were measured by an enzyme multi-immune assay technique. The patients underwent conventional and Doppler echocardiography with TDI. RESULTS: The patients were divided into 2 groups according to C2 levels less than 500 mug/L (group 1, n = 40) versus greater than 500 mug/L (group 2, n = 38). The demographic parameters, serum creatinine and lipid levels, systolic and diastolic blood pressures, number and type of antihypertensive medications, and conventional echocardiographic parameters did not differ significantly between the groups. However, group 1 patients showed significantly higher isovolumic relaxation time (109 +/- 27 vs 86 +/- 14 ms), early diastolic deceleration time (189 +/- 52 vs 137 +/- 59 ms), and lower values of E velocity (56 +/- 32 vs 92 +/- 27 cm/s) and E/A ratios (0.81 +/- 0.23 vs 1.15 +/- 0.46) than group 2. TDI studies revealed significantly lower E'/A' (0.76 +/- 0.25 vs 1.09 +/- 0.32, P < .05) in group 1 versus group 2. CONCLUSION: The data suggested that the higher C2 levels may induce diastolic dysfunction in the hearts of kidney recipients without impairment of contractile performance.

Gingival health status in renal transplant recipients: relationship between systemic inflammation and atherosclerosis.

Cardiovascular disease (CVD) is the leading cause of mortality in renal transplant recipients (RTR). Systemic and periodontal inflammation has been suggested to have a possible role in the development of atherosclerosis. In the present study, we aimed to investigate the relationship between gingival health status, inflammation and atherosclerosis in RTRs. Eighty-three RTR (50 male, 33 female) were enrolled in the study. Routine biochemical analyses, serum lipoproteins, C-reactive protein, fibrinogen, homocystein, parathyroid hormone (PTH) and cyclosporin A (CsA) trough levels were studied. All patients had 24-h ambulatory blood pressure monitoring and B-mode ultrasound of the common carotid arteries. Gingival status was evaluated by the Löe and Silness gingival index (GI). Mean GI value was 2.3 +/- 0.5. Fifty patients (60.3%) had GI value >or= 2.1 (severe gingivitis; group A). Thirty-three patients (39.7%) had GI value < 2.1 (no or moderate gingivitis; group B). Age, carotid intima-media thickness (CIMT) and mean time on dialysis before transplantation were significantly higher in group A than in B. Systemic inflammation markers were not different between group A and group B. Mean CIMT was positively correlated with GI (r = 0.425; p = 0.001) and negatively correlated with high-density lipoprotein cholesterol (r = -0.256; p = 0.023). After the correction for confounding variables, mean CIMT was still significantly correlated with GI (r = 0.376, p = 0.02). In RTR, gingival inflammation seems to be associated with CIMT in the absence of systemic inflammation. Thus, gingivitis may, in part, play a role in the development of systemic atherosclerosis without causing any aggravation in systemic inflammatory response.

The role of proinflammatory cytokine gene polymorphisms for development of insulin resistance after renal transplantation.

BACKGROUND: Insulin resistance, a frequent prediabetic metabolic complication after renal transplantation, is generally linked to immunosuppressive drugs including corticosteroids, cyclosporine (CsA) or tacrolimus, as well as to age, cadaveric donors and ethnic factors. Cytokines are known to be inflammation modulatory substances that contribute to metabolic derangements after transplantation. The present study investigated the effects of cytokine gene polymorphisms on insulin resistance in renal transplant recipients. PATIENTS AND METHODS: Sixty-one renal transplant recipients (37 men, 24 women; mean age: 39.3 +/- 10.8 years) who attended regular clinical visits without a known history of diabetes were enrolled in the study. All patients were on a regimen of steroid, CsA, and mycophenolate mofetil. Venous blood samples were collected for biochemical analyses after an overnight fast at 08:00 pm. CsA trough levels, C-reactive protein, and fibrinogen were also estimated. Additional 10 mL of blood was withdrawn into an ethylenediamine tetraacetic acid-containing tube to determine cytokine genotypes (tumor necrosis factor-alpha [TNF-alpha] -238 G/A, transforming growth factor-beta [TGF-beta] codon 10 -869 T/C). Insulin resistance was calculated by the homeostasis model assessment (HOMA) method using the values of fasting blood glucose (FBG) and insulin levels. Anthropometric indices as well as body height, weight, waist and hip circumferences were measured simultaneously to calculate body mass index (kg/m2) and waist-to-hip ratio. Impaired fasting glucose (IFG) was described as an FBG > or = 110 but < 126 mg/dL. RESULTS: IFG was detected in 27.9% of this study group. The HOMA index was significantly higher among patients with IFG compared with normal FBG (NoGT) (6.3 +/- 4.5 vs 3.7 +/- 1.5; P = .01). Neither FBG and insulin nor HOMA values correlated with antrophometric, metabolic, or inflammatory parameters. Cytokine genotype allele frequencies, age, sex, immunosuppressive and antihypertensive drug type and doses, CsA trough levels, and donor source (cadaveric/living) were similar for patients with IFG and NoGT. Mutant allele carrier genotypes (AA + GA) for TNF-alpha -238 G/A showed higher fasting insulin (14.0 +/- 7.9 vs 34.1 +/- 17.7 microIU/mL; P = .04) and HOMA (4.01 +/- 2.01 vs 7.95 +/- 5.44; P = .002) levels than GG homozygote subjects. FBG, HOMA, and other metabolic and anthropometric indices were similar between TGF-beta codon 10 -869 T/C genotypes. The daily dose of steroid (mg/d) and A allele frequency for TNF-alpha -238 G/A genotype were significant predictors of HOMA index in linear regression analysis. CONCLUSION: The present study revealed that beside the daily dose of steroids, TNF-alpha -238 G/A genotype may contribute to insulin resistance in renal transplant recipients. Further investigations may highlight the effects of cytokine gene heterogenity on insulin resistance in those patients.

The prevalence of carotid artery calcification on the panoramic radiographs of patients with renal disease.

OBJECTIVES: To determine the prevalence of carotid calcification on dental panoramic radiographs in end-stage renal disease (ESRD) patients on haemodialysis and renal transplant recipients. METHODS: Panoramic radiographs of 69 adult patients with renal disease (34 with haemodialysis and 35 with renal transplantations) (age range 17-74 years; mean age 39.45 years) and 50 controls (age-match, free of systemic disease) were examined on panoramic radiographs for any unusual radiopacity adjacent to or just below the intervertebral space between C3 and C4. Patients with such calcifications were referred to ultrasound examination. Using Chi-squared tests, calcification prevalence rates were statistically compared. RESULTS: The statistical difference between renal disease patients and control group was significant (chi2 = 17.91, P < 0.001). On comparison of haemodialysis patients and renal transplant recipients with controls, statistical difference (P=0.007) was found to be significant. CONCLUSION: Carotid artery calcification was higher in haemodialysis patients and renal transplant recipients. These patients with such calcifications should be referred for further evaluation and treatment of carotid arteries, coronary arteries and vascular risk factors.

Prediction of renal allograft function with early Doppler ultrasonography.

INTRODUCTION: Doppler ultrasonography (USG) is an useful, noninvasive diagnostic tool for the management and follow-up of the transplanted kidney. However, it is believed that the value of Doppler USG is limited to discrimination of acute rejection episodes. We tested whether early Doppler USG findings were predictive of 1-month and 1-year allograft functions in noncomplicated renal transplant recipients (RTRs). PATIENTS AND METHODS: Resistive index (RI) and pulsatile index (PI) values obtained by doppler USG within the first week of transplantation were correlated with allograft function at 1 month and 1 year in 45 (10 women, 35 men, mean age: 27 years) noncomplicated cases. Patients with complications during the first posttransplant year were not included. RESULTS: There was a negative correlation between both RI and PI with creatinine clearance values at 1 month and at 1 year posttransplant. There was a significant decline in allograft function among cases with either RI > or = 0.7 or PI > or = 1.1. Patients with impaired allograft function have higher RI and PI values. CONCLUSION: Renal allograft survival is influenced by many factors. However, no reliable simple parameter has been identified to predict long-term outcome. Doppler USG performed during the early transplantation period with calculation of RI and PI may have a predictive value to forecast early and long-term outcomes of noncomplicated kidney transplants.

Pure red cell aplasia preceding malignant lymphoma in a renal transplant patient.

Malignant disorders are one of the major causes of morbidity and mortality in transplant patients. We present herein a renal transplant recipient with malignant lymphoma which preceded by pure red cell aplasia (PRCA). Acquired PRCA is a rare hematologic disorder in renal transplant recipients. It has been associated with a variety of disorders of immunologic dysfunction and neoplasms, exposure to drugs and toxins, infectious diseases, pregnancy and severe nutritional deficiency. This is the first case with PRCA preceding the malign lymphoma in a renal transplant patient. Treatment of lymphoma and lymphoma-related humoral and cellular changes or other undefined effects that may be related to therapy may be responsible of the resolving of PRCA in this patient. In this regard, renal transplant patients with acquired PRCA, must be closely followed for an underlying neoplastic disorder.

Polyarteritis nodosa in patients with Familial Mediterranean Fever (FMF): a concomitant disease or a feature of FMF?

BACKGROUND: Familial Mediterranean Fever (FMF) is caused by mutations in the gene encoding pyrin and is characterized by self-limited, recurrent attacks of fever and serositis. Vasculitis has been increasingly reported in FMF. A study evaluating the prognosis in FMF and polyarteritis nodosa (PAN) patients has not been reported previously. OBJECTIVES: To determine the special characteristics and the prognosis of PAN in FMF patients. METHODS: A questionnaire was used for the present survey. The setting was 7 referral centers from Turkey and Israel. Seventeen patients who were diagnosed with FMF and who developed PAN were included. PAN was diagnosed in those who met the Chapel Hill consensus criteria for microscopic polyarteritis or classic PAN. The clinical features of these 17 patients and the outcomes of their vasculitis were analyzed. RESULTS: The age at diagnosis of PAN in these FMF patients ranged from 3.5 to 37 years. All patients had constitutional symptoms, elevated acute phase reactants, and myalgia at the time PAN was diagnosed. The diagnosis of PAN was confirmed by renal angiography in 8 patients, by renal biopsy in 6 patients, and by muscle and/or nodule biopsies in 6 patients. A number of patients had definite features of both classic PAN and microscopic polyarteritis. CONCLUSIONS: When compared with other PAN patients, those with FMF tended to have a younger age at PAN onset, more frequent perirenal hematomas, and an overall better prognosis. The cases with overlapping features of microscopic and classic PAN pose a problem for the current classification of vasculitis. We suggest that the clinical representation of PAN in FMF patients has certain characteristics and may be a feature of FMF per se.

Bone mineral density in haemodialysis patients: A comparative study of dual-energy X-ray absorptiometry and quantitative ultrasound.

BACKGROUND: Quantitative ultrasound (QUS) of bone is a relatively new technique that appears to assess 'bone quality' in addition to bone mineral density. The purpose of this study was to evaluate the diagnostic potential of QUS of calcaneum and to correlate it with dual energy X-ray absorptiometry (DEXA) in chronic haemodialysis patients. METHODS: Broad-band ultrasound attenuation (BUA; dB/MHz) and speed of sound (SOS; m/s) of calcaneum and DEXA (g/cm(2)) measurements of the lumbar spine and hip were made in 39 patients. The indices obtained by either method were compared with age-and sex-matched controls. Calcaneal measurements were correlated to DEXA and relevant clinical and biochemical data of patients. RESULTS: BUA and SOS values were markedly reduced in dialysis patients compared to controls (59.1+/-13.8 vs 73.0+/-16.2 dB/MHz, P:<0.001 and 1533+/-28 vs 1560+/-29 m/s, P:=0.014 respectively). There was a moderate, but significant association between calcaneal parameters and DEXA (r=0.32-0.53, P:<0.05). Both BUA and SOS scores were inversely correlated with age (r=-0.69, P:<0.001) and duration of menopause (r=-0.74, P:<0.01). Additionally, BUA values showed a moderate negative association with serum intact parathyroid values (r=-0.38, P:=0.018). CONCLUSION: Chronic haemodialysis patients have reduced calcaneal BUA and SOS scores. QUS of the calcaneum is an easy-to-apply and radiation-free technique. It could be a useful substitute for assessment of bone density in such patients. However, further studies in large patient groups and comparisons with plasma markers of bone turnover and bone biopsy findings are needed to assess its potential place in the management of renal osteodystrophy.

Effects of angiotensin converting enzyme and angiotensin II receptor inhibition on impaired fibrinolysis in systemic hypertension.

Abnormalities in fibrinolysis have been reported in hypertension. Angiotensin converting enzyme (ACE) inhibitors have been shown to improve altered fibrinolytic balance in hypertensive patients. It has not been documented, however, whether this is due to a decrease in angiotensin II (Ang-II) generation or is a consequence of elevated local levels of bradykinin. Accordingly, the aim of this study was to determine the effects of an ACE inhibitor (perindopril) and an Ang-II receptor antagonist (losartan) on fibrinolytic kinetics. We have examined the serum levels of the plasminogen activator inhibitor type-1 (PAI-1) antigen and activity, tissue plasminogen activator (t-PA) antigen and activity, soluble thrombomodulin (sTM), and tissue factor pathway inhibitor (TFPI) before and after reaching the target blood pressure (<140/90 mm Hg) in 13 hypertensive patients receiving perindopril (mean age 40+/-11 years, 6 women, 7 men) and in 12 patients receiving losartan (mean age 38+/-9 years, 6 women, 6 men). We also compared the baseline fibrinolytic activity of hypertensive patients with that of 12 normotensive control persons (mean age 40+/-9 years, 6 women, 6 men). The mean basal plasma levels of PAI-1 antigen, PAI-1 activity, and sTM were significantly higher in the hypertensive patients than in normal controls (P<.005). The values of other analytes were similar in both groups. Increased plasma levels of PAI-1 antigen, PAI-1 activity, and sTM were reduced in patients after they were given perindopril and losartan (P<.005); the reductions in losartan-receiving group were more pronounced (P<.05). There were no significant effects on the plasma levels of t-PA antigen, t-PA activity, and TFPI in patients receiving the two therapeutic regimens (P>.05). In conclusion, chronic hypertension is associated with hypofibrinolysis. The beneficial effect of ACE inhibitors on fibrinolysis seems to be related to the blockade of Ang-II, and increased kinin activity does not appear to play a major role.

Determinants of soluble CD23 antigen levels in hemodialysis patients: effect of 1.25 dihydroxyvitamin D3 and recombinant human erythropoietin treatment.

BACKGROUND: The immunodeficiency of end-stage renal disease (ESRD) paradoxically coexists with T cell and monocyte activation. In spite of well known defective antibody responses in ESRD, the functional status of B cells in the immune system dysregulation of uremia is still controversial. Soluble CD23 (sCD23) antigen is a recently identified B cell activation marker and is also involved in T cell activation process. Effects of parathyroid hormone (PTH), red blood cells and ferritin on T and B cell functions have been shown both in vivo and in vitro. PATIENTS AND METHODS: In this study, serum levels of sCD23 in hemodialysis patients were determined to evaluate the functional status of B cells and possible linkages between this cytokine and PTH levels, ferritin levels, red blood cell counts were investigated. RESULTS: Serum sCD23 levels were significantly elevated in hemodialysis patients relative to healthy controls (12.5+/-8.4 micro/l vs. 2.4+/-1.1 micro/l, p<0.001). Serum sCD23 levels were negatively correlated with red blood cell count (r = -0.61, p = 0.009) and serum PTH levels (r = -0.62, p = 0.008), while positively correlated with serum ferritin levels (r = 0.63, p = 0.007) in hemodialysis patients. We also investigated the immunumodulator effects of 1.25 dihydroxyvitamin D3 (1.25OHD3) and recombinant human erythropoietin (rHu-Epo) treatment in hemodialysis patients. 1.25OHD3 treatment for eight weeks did not change serum sCD23 levels in hemodialysis patients (n = 8). On the other side, rHu-Epo administration for 16 weeks led to a decrease in serum sCD23 levels (17.7+/-8.6 microg/l vs. 9.8+/-3.5 microg/l, p = 0.007) in these patients (n = 9). CONCLUSION: These results suggests that similar to T cells, B cells are activated in uremia and the degree of this activation is correlated with red blood cell count, serum parathyroid hormone levels and iron status of the hemodialysis patients. Moreover, B cell activation could be altered by recombinant human erythropoietin therapy in hemodialysis patients.

Cyclical acute renal failure due to bilateral ureteral endometriosis.

Endometriosis is a common disease but ureteral involvement is relatively rare. Ureteric endometriosis is mostly unilateral. Endometriotic ureteral obstruction is a serious event commonly diagnosed late and therefore associated with a major risk of hydronephrotic renal atrophy. We present the cyclical acute renal failure associated with menstruation in a patient who developed severe bilateral ureteral obstruction due to endometriosis. Physicians should be aware of this uncommon but serious manifestation of endometriosis, especially if the clinical presentation is cyclical acute renal dysfunction in a premenopausal woman.

Serum thrombopoietin levels in haemodialysis patients: involvement of arteriovenous fistula.

BACKGROUND: Thrombopoietin (Tpo) is a recently cloned growth factor which plays a critical role in the regulation of thrombopoiesis. Tpo has also been shown to stimulate in vitro and in vivo erythroid cell growth. Although Tpo transcripts were detected in hepatocytes, proximal tubules and endothelium, mechanisms regulating the level of circulating Tpo have not been fully delineated. Changes in the vessel wall and blood flow in arteriovenous fistula (AVF) might alter Tpo activity. METHODS: Serum thrombopoietin levels and serum erythropoietin levels in samples concurrently obtained from venous returns of AVF and contralateral peripheral veins in 31 haemodialysis patients were determined and compared with 12 healthy controls. Levels were also compared between 14 haemodialysis patients (group I) treated with recombinant human erythropoietin (rHu-Epo) and 17 haemodialysis patients (group II) not requiring rHu-Epo. RESULTS: Serum Tpo levels (44.8 +/- 23.9 pg/ml, vs 129.9 +/- 113.6 pg/ml, P<0.05) and platelet counts (194 +/- 55, 10(6)/ml vs 273 +/- 94. 10(6)/ml, P<0.05) of haemodialysis patients were lower than healthy controls. Serum Tpo levels were inversely correlated with platelet counts in the control group (R=-0.61, P<0.05), but not in haemodialysis patients. Tpo concentrations of AVF samples were lower than peripheral venous samples (31.6 +/- 17.7 pg/ml vs 44.8 +/- 23.9 pg/ml, P=0.001). No significant difference was present between the serum Tpo concentrations of haemodialysis patients in group I and group II. Serum Tpo levels were not correlated with haemoglobin levels or serum erythropoietin levels in haemodialysis patients. CONCLUSION: Decreased serum Tpo levels despite low platelet counts in haemodialysis patients suggest that the proposed feedback mechanism of platelet uptake of Tpo is not fully operative in these patients. Moreover, AVF might affect the local production and/or catabolism of this growth factor.

Thrombopoietin and thrombospondin in renal allograft recipients.

Recipients of renal transplants appear to be at increased risk of thromboembolic events. Despite accumulating evidence for the hyperreactivity of platelets, the primary regulator of thrombopoiesis, thrombopoietin (TPO), has not yet been studied in renal transplant recipients. Thus, the aim of the present study was to quantify the levels of TPO and to assess its contribution to increased platelet reactivity in recipients of renal allografts. Serum concentrations of thrombospondin (TSP) were also determined in patients undergoing renal transplants in order to evaluate the role of this multifunctional protein in platelet hyperaggregability. Serum levels of TPO were significantly lower in renal transplant recipients (n = 27) than in healthy controls (30.8+/-20.6 pg/ml versus 129.9+/-113.6 pg/ml, P = 0.001). Serum concentrations of TPO were correlated neither with serum levels of creatinine nor duration of transplantation. However, levels of TPO were negatively correlated with platelet counts (r = -0.50, P = 0.007) in recipients of renal transplants. Plasma levels of TSP were higher in renal transplant patients than in the control group (104.5+/-54.7 ng/ml versus 63.4+/-41.5 ng/ml, P = 0.003). No significant correlation was found between levels of TPO and TSP. We conclude that, rather than the allograft function, the platelet mass determines the levels of TPO in recipients of renal transplants. Despite the low serum levels of TPO, and increased concentrations of TSP, TPO might still play a role in the hyperaggregability of platelets in patients undergoing renal transplants.