Renal arteriolar hyalinosis, not intimal thickening in large arteries, is associated with cardiovascular events in people with biopsy-proven diabetic nephropathy

AIMS

Diabetic nephropathy, a pathologically diagnosed microvascular complication of diabetes, is a strong risk factor for cardiovascular events, which mainly involve arteries larger than those affected in diabetic nephropathy. However, the association between diabetic nephropathy pathological findings and cardiovascular events has not been well studied. We aimed to investigate whether the pathological findings in diabetic nephropathy are closely associated with cardiovascular event development.

METHODS

This retrospective cohort study analysed 377 people with type 2 diabetes and biopsy-proven diabetic nephropathy, with a median follow-up of 5.9 years (interquartile range 2.0 to 13.5). We investigated how cardiovascular events were impacted by two vascular diabetic nephropathy lesions, namely arteriolar hyalinosis and arterial intimal thickening, and by glomerular and interstitial lesions.

RESULTS

Of the 377 people with diabetic nephropathy, 331 (88%) and 295 (78%) had arteriolar hyalinosis and arterial intimal thickening, respectively. During the entire follow-up period, those with arteriolar hyalinosis had higher cardiovascular event rates in the crude Kaplan-Meier analysis than those without these lesions (P = 0.005, log-rank test). When fully adjusted for clinically relevant confounders, arteriolar hyalinosis independently predicted cardiovascular events [hazard ratio (HR) 1.99; 95% confidence interval (CI) 1.12, 3.86], but we did not find any relationship between arterial intimal thickening and cardiovascular events (HR 0.89; 95% CI 0.60, 1.37). Additionally, neither glomerular nor interstitial lesions were independently associated with cardiovascular events in the fully adjusted model.

CONCLUSIONS

Arteriolar hyalinosis, but not intimal thickening of large arteries, was strongly associated with cardiovascular events in people with diabetic nephropathy.

Phosphate binders prevent phosphate-induced cellular senescence of vascular smooth muscle cells and vascular calcification in a modified, adenine-based uremic rat model

Clinical and experimental studies have reported that phosphate overload plays a central role in the pathogenesis of vascular calcification in chronic kidney disease. However, it remains undetermined whether phosphate induces cellular senescence during vascular calcification. We established a modified uremic rat model induced by a diet containing 0.3% adenine that showed more slowly progressive kidney failure, more robust vascular calcification, and longer survival than the conventional model (0.75% adenine). To determine the effect of phosphate on senescence of vascular smooth muscle cells (VSMCs) and the protective effect of phosphate binders, rats were divided into four groups: (1) normal control rats; (2) rats fed with the modified adenine-based diet (CKD); (3) CKD rats treated with 6% lanthanum carbonate (CKD-LaC); and (4) CKD rats treated with 6% calcium carbonate (CKD-CaC). After 8 weeks, CKD rats showed circumferential arterial medial calcification, which was inhibited in CKD-LaC and CKD-CaC rats. CKD rats showed increased protein expression of senescence-associated β-galactosidase, bone-related proteins, p16 and p21, and increased oxidative stress levels in the calcified area, which were inhibited by both phosphate binders. However, serum levels of oxidative stress and inflammatory markers, serum fibroblast growth factor 23, and aortic calcium content in CKD-CaC rats were higher than those in CKD-LaC rats. In conclusion, phosphate induces cellular senescence of VSMCs in the modified uremic rat model, and phosphate binders can prevent both cellular senescence and calcification of VSMCs via phosphate unloading. Our modified adenine-based uremic rat model is useful for evaluating uremia-related complications, including vascular calcification.

Blood pressure control in a Japanese population with chronic kidney disease: a baseline survey of a nationwide cohort

BACKGROUND

Hypertension is a key risk factor for adverse renal outcomes in chronic kidney disease (CKD), and strict blood pressure control is recommended to halt its progression. This study assessed blood pressure control in the Japanese CKD population.

METHODS

We used a nationwide database of 250,130 subjects (aged 20-88), including 45,845 CKD subjects (18.3%), participated in an annual health check, "The Specific Health Check and Guidance in Japan," and examined the relationship between CKD status and blood pressure. Blood pressures were measured in sitting position by trained staff, and target blood pressure for CKD subjects was defined as systolic (SBP)/diastolic blood pressure (DBP) <130/80 mm Hg.

RESULTS

In total population, CKD subjects had a higher prevalence of hypertension (58.0% vs. 41.8%, P < 0.001) and a higher proportion with antihypertensive medication (42.4% vs. 26.7%, P < 0.001), compared with non-CKD subjects. The proportion of subjects achieving target blood pressure was significantly lower among total CKD subjects than among total non-CKD subjects (34.6% vs. 43.8%, P ≤ 0.001). Among CKD subjects, these proportions were especially low in those with stage 4-5 (24.3-27.5%), those on antihypertensive medication (21.6%) and those with proteinuria ≥2± (21.3%). Logistic regression analysis showed that independent factors for high-blood pressure in CKD subjects were age, male gender, alcohol consumption, nonsmoking, diabetes, dyslipidemia, obesity, proteinuria, and antihypertensive medication.

CONCLUSIONS

Blood pressure control was inadequate in the majority of Japanese CKD subjects, despite antihypertensive treatment. More aggressive efforts to achieve target blood pressures among CKD subjects are recommended.

Two cases of calciphylaxis treated by parathyroidectomy: importance of increased bone formation

Calciphylaxis (calcific uremic arteriolopathy) is a poorly understood and highly morbid syndrome of both vascular calcification and skin necrosis. The main histopathological finding is calcium deposits within arteriolar and small vessel walls, showing endovascular fibrosis associated with fat necrosis. The therapeutic strategy is to normalize the high calcium-phosphate products (Ca x P). When calciphylaxis is complicated with advanced renal hyperparathyroidism (HPT), parathyroidectomy (PTX) should be performed promptly. However, for patients with low PTH level, calciphylaxis is unresponsive to PTX, and such an approach may worsen hyperphosphatemia and hypercalcemia. We report two patients with calciphylaxis confirmed by skin biopsy. PTX was performed in both patients based on high PTH levels. PTH and Ca x P level decreased in both patients post PTX. In Case 1, the skin ulcers gradually improved and almost disappeared after PTX. However, in Case 2, new ulcers appeared after PTX. In Case 1, alkaline phosphatase (ALP) after PTX was approximately twice its level before surgery and PTX resulted in normalization of uptake on bone scintigraphy. However, no rise in ALP was noted in Case 2, probably due to long-term use of aluminum, which prevented bone formation. These findings suggest that differences in the extent of bone formation explain the different response in post-PTX ulcer healing.

Candida glabrata fungemia in a diabetic patient with neurogenic bladder: successful treatment with micafungin

A 69-year-old man was transferred to our hospital because of fever and acute renal failure. 5 weeks prior to admission, he was admitted to another hospital and treated with several antibiotics including vancomycin, but fever did not subside and renal dysfunction showed rapid progression. On admission, laboratory findings revealed pyuria, inflammatory changes, acute renal failure, and disseminated intravascular coagulation (DIC). Computed tomography showed left ureteral stone and hydronephrosis. Gallium scintigraphy showed avid uptake in the left kidney. Serum concentration of vancomycin was 57.4 micro/ml. Candida glabrata was isolated from blood, sputum and urine. Under the diagnosis of fungemia and left pyelonephritis, he was treated with micafungin (150 mg/day), gabexate mesilate and insertion of a double-ended pigtail catheter. The above treatment produced regression of systemic inflammation, DIC and acute renal failure. At the last follow-up 3 weeks after discharge, ureteroscopy showed that the ureter stone had already passed but a soft white-yellowish bezoar was detected in the ureter. In this case, neurogenic bladder, poorly controlled diabetes, and long-term antibiotic treatment probably enhanced the development of C. glabrata infection. Antifungal treatment with micafungin is useful in patients with non-albicans Candida infection.

Persistent hyperparathyroidism in renal allograft recipients: vitamin D receptor, calcium-sensing receptor, and apoptosis

The phenotypic changes in parathyroid cells after successful renal transplantation remain to be elucidated. We compared 10 diffuse and 11 nodular hyperplastic parathyroid glands from five renal allograft recipients with persistent hyperparathyroidism, with five diffuse and 13 nodular hyperplasia from seven uremic patients on hemodialysis, and 13 normal glands. Comparisons included expressions of both vitamin D receptor (VDR) and calcium-sensing receptor (CaSR), proliferative activity (Ki67), and apoptosis (TUNEL). Immunoreactivity was assessed semiquantitatively and expressed as labeling index. The area/cell was also measured to assess cellular hypertrophy. The labeling indexes of VDR (587+/-71; mean+/-s.e.m.) and CaSR (45.0+/-2.8) in recipients' diffuse hyperplasia were significantly higher than those in uremic diffuse hyperplasia (224+/-44, 29.3+/-2.3, respectively) (P<0.01, each). However, these expressions remained low in recipients' nodular hyperplasia (42+/-8, 11.8+/-1.4, respectively). Ki67 labeling index in recipients' nodular hyperplasia (7+/-1) was significantly smaller than in uremic patients (24+/-6, P<0.01). TUNEL labeling index in recipients' diffuse hyperplasia (30+/-5) was the highest among the groups. The cell volume tended to be smaller in both patterns of hyperplasia in allograft recipients compared with uremic patients. Our results suggest that the phenotypic change in parathyroid cells after renal transplantation depends on the pattern of hyperplasia, where it is normalized only in diffuse hyperplastic glands in which the number of cells also regresses with significant induction of apoptosis.

Parathyroid growth and regression in experimental uremia

Early 1,25-dihydroxyvitamin D(3) (VD(3)) therapy during the course of renal failure prevents the downregulation of VD(3) receptor (VDR), calcium-sensing receptor (CaSR) or p21, and the parathyroid (PT) growth. We hypothesized that VD(3) could restore the decreased expressions of VDR and CaSR, and cause regression in enlarged PT glands. 5/6 nephrectomized rats fed high-phosphorus diet were killed at 1, 3, 5, or 7 days and at 2, 3, 4, 8, or 12 weeks. VD(3)-treated rats were given VD(3) intraperitoneally for 1, 2, 3, or 4 weeks, starting 8 weeks after 5/6 nephrectomy. PT glands were weighed and subjected to immunohistochemical analyses for VDR, CaSR, p21, Ki67, and Tdt-mediated dUTP nick end-labeling (TUNEL) assay. The area per cell was measured as the parameter of cell size. The expression of VDR and p21 began to decrease at day 1, and Ki67 increased at day 3, but decreased thereafter. There was a significant increase in PT gland weight to week 12 with the increase of cell size. VD(3) treatment significantly increased both VDR and CaSR expressions 2 weeks after the start of injection, and reduced the PT gland weight at week 3 with significant increase of TUNEL-positive cells and decrease of cell size. Our results suggest that PT growth in uremic rats involves both PT cell proliferation and hypertrophy, in association with the reduction of VDR, CaSR, and p21 expressions. In addition, VD(3) treatment could reverse PT hyperplasia and hypertrophy via restoration of these proteins.

Strong polarization toward Th1 immune response in ANCA-associated glomerulonephritis

AIM

Human immune response can be classified into 2 different subsets of T helper cells (Th1 and Th2) based on the pattern of cytokine production. In modern immunology, Th1/Th2 paradigm helps to explain the different inflammatory effector pathways and outcomes in human diseases. The present study was designed to determine the type of immunological response that influences anti-neutrophil cytoplasmic antibody-(ANCA) associated glomerulonephritis (GN) using cytokine analysis of peripheral T cells and diseased kidney tissues.

PATIENTS AND METHODS

We analyzed peripheral blood Th1/Th2 ratio in 91 patients with primary GN, including 10 cases of ANCA-associated GN. Tissues were immunostained with markers of T cells and macrophages and osteopontin (OPN). Intrarenal expression of IFN-gamma and IL-4 mRNAs was evaluated by reverse transcriptase (RT)-PCR.

RESULTS

Peripheral Th1/Th2 ratio was significantly higher in ANCA-associated GN (19.4 +/- 9.4, mean +/- SD, n = 10), than those in healthy controls (7.6 +/- 4.1, n = 27), IgA nephropathy (9.6 +/- 5.6, n = 45), membranous nephropathy (7.1 +/- 4.4, n = 13), minimal-change nephrotic syndrome (8.2 +/- 4.5, n = 13) and focal segmental glomerulosclerosis (8.3 +/- 3.9, n = 10) (p < 0.01, each). In 7 of 10 cases of ANCA-associated GN, Th1/Th2 ratio decreased significantly after treatment with corticosteroid from 21.0 +/- 12.0 to 9.0 +/- 6.6 (p < 0.05). Immunohistochemical staining showed numerous infiltrating T cells, macrophages and OPN-positive cells in both glomerular tuft and cellular crescent; OPN-positive cell distribution was similar to that of macrophages. Intrarenal expression of IFN-gamma mRNA was strongly enhanced whereas a weak expression of IL-4 mRNA was observed especially in advanced cases showing tubulointerstitial injury.

CONCLUSION

Both peripheral and renal immune responses are strongly polarized toward Th1 type immune response in ANCA-associated GN. Peripheral Th1/Th2 ratio may reflect the immune responses in renal injury of ANCA-associated GN.

Diffuse proliferative glomerulonephritis after bone marrow transplantation

A 15-year-old boy developed nephrotic syndrome and acute renal failure 4 years after allogenic bone marrow transplantation (BMT) for lymphoid crisis of chronic myelocytic leukemia. On admission, he presented with clinical features of chronic GVHD including transient exacerbation of cholestatic liver injury. Renal biopsy showed diffuse proliferative glomerulonephritis with cellular crescents. The patient was treated with methylprednisolone pulse therapy (1 g/day, for 3 days) followed by oral prednisolone. Renal function gradually improved but nephrotic state was persistent. A second renal biopsy showed improvement of acute tubular necrosis and endocapillary proliferation and transformation of crescents into a fibrous form. After tapering of oral prednisolone, cyclophosphamide was started, which resulted in a gradual improvement of proteinuria. Several cases of nephrotic syndrome occurring after BMT have already been reported, but most cases had membranous nephropathy. In our case, renal biopsy revealed diffuse proliferative glomerulonephritis with findings of active cellular immunity, and aggressive treatment resulted in attenuation of these findings. Moreover, chronic GVHD-related liver injury was noted at the time of this episode. Our findings suggest that chronic GVHD may be complicated with diffuse proliferative glomerulonephritis through unknown cellular immune mechanism.

Intracellular distribution of the antimutagenic enzyme MTH1 in the liver, kidney and testis of F344 rats and its modulation by cadmium

Cellular distribution of the antimutagenic MTH1protein in the liver, kidney, and testis of Fischer rat was evaluated using the immunohistochemical staining with anti-MTH1 polyclonal antibody. The present investigation revealed a non-uniform distribution of MTH1 among cells and among the cytoplasmic, nuclear, and membranal structures of cells within a given tissue. A particularly strong expression of MTH1 was observed for the first time in the perinuclear acrosomic bodies of spermatocytes and in the acrosomic vesicles of sperm heads. Treatment of rats with a single sc dose of 20 micromol Cd(II)/kg body wt. produced histopathologic changes in these organs accompanied by redistribution of the cellular MTH1 protein between the cytoplasm and nuclei. The acute phase of Cd(II) toxicity, that in the liver and especially in the testes (but not in kidneys) led to cell necrosis, was accompanied by a characteristic decrease in the abundance of MTH1-expressing nuclei. Chronic toxicity without necrosis, persisting in the kidney over the entire 14-day study, as well as the survival and proliferation of cells, observed in the liver and testis after the necrotizing phase, were signified by increased number of nuclei expressing MTH1. Thus, unlike previous biochemical studies, immunohistochemistry managed to reveal alterations in the patterns of inter- and intracellular distribution of MTH1, associated apparently with the conditional changes in the dynamics of synthesis of nucleic acids, assisted by this protein.

Predominance of Th1 immune response in diffuse proliferative lupus nephritis

OBJECTIVE

Lupus nephritis, which shows various histologic patterns, is a serious complication of systemic lupus erythematosus (SLE). We previously demonstrated the importance of Thl cell-mediated immune response in patients with diffuse proliferative lupus nephritis (DPLN). The aim of this study was to examine the relationship between the peripheral blood Th1/Th2 balance and the intrarenal immune response.

METHODS

The Th1:Th2 ratio in peripheral blood was measured by intracellular staining for cytokines with flow cytometry. Immunohistochemical analysis of renal biopsy specimens was performed to clarify the characterization of local infiltrating cells in 3 groups of subjects: SLE patients with World Health Organization (WHO) class IV nephritis (DPLN) (group I; n = 13), SLE patients with WHO class V nephritis (group II; n = 9), and patients with minor glomerular lesions (group III; n = 7). In addition, the histologic activity index and chronicity index were evaluated and correlated with the Th1:Th2 ratio.

RESULTS

Immunohistochemical studies showed higher numbers of CD68+ macrophages, CD3 + T cells, and interferon-gamma-positive cells in group I than in groups II or III. Renal tissues from patients in group I also showed up-regulation of expression of osteopontin and CD40, with a small number of infiltrating T cells expressing interleukin-4. Overall, the Thl:Th2 ratio in group I patients (SLE with DPLN) was high and correlated significantly with the histologic activity index, but not with the chronicity index.

CONCLUSION

We have identified a predominance of Thl-type response in both peripheral and renal tissues of patients with DPLN, suggesting that the peripheral blood Thl:Th2 ratio directly reflects the local histopathologic findings. In patients with lupus nephritis, the peripheral blood Th1:Th2 ratio could be useful as a parameter that reflects the renal histologic activity or the strength of the local Thl response.

A novel superoxide-producing NAD(P)H oxidase in kidney

During phagocytosis, gp91(phox), the catalytic subunit of the phagocyte NADPH oxidase, becomes activated to produce superoxide, a precursor of microbicidal oxidants. Currently increasing evidence suggests that nonphagocytic cells contain similar superoxide-producing oxidases, which are proposed to play crucial roles in various events such as cell proliferation and oxygen sensing for erythropoiesis. Here we describe the cloning of human cDNA that encodes a novel NAD(P)H oxidase, designated NOX4. The NOX4 protein of 578 amino acids exhibits 39% identity to gp91(phox) with special conservation in membrane-spanning regions and binding sites for heme, FAD, and NAD(P)H, indicative of its function as a superoxide-producing NAD(P)H oxidase. The membrane fraction of kidney-derived human embryonic kidney (HEK) 293 cells, expressing NOX4, exhibits NADH- and NADPH-dependent superoxide-producing activities, both of which are inhibited by diphenylene iodonium, an agent known to block oxygen sensing, and decreased in cells expressing antisense NOX4 mRNA. The human NOX4 gene, comprising 18 exons, is located on chromosome 11q14.2-q21, and its expression is almost exclusively restricted to adult and fetal kidneys. In human renal cortex, high amounts of the NOX4 protein are present in distal tubular cells, which reside near erythropoietin-producing cells. In addition, overexpression of NOX4 in cultured cells leads to increased superoxide production and decreased rate of growth. The present findings thus suggest that the novel NAD(P)H oxidase NOX4 may serve as an oxygen sensor and/or a regulator of cell growth in kidney.

Optimal hematocrit for the maximum oxygen delivery to the brain with recombinant human erythropoietin in hemodialysis patients

AIM

Although hematocrit (Ht) around 33 to 36% has been recommended, Ht of 30% is usually achieved as a target level during recombinant human erythropoietin (rHuEPO) therapy in the majority of hemodialysis (HD) patients. The present study aimed at estimating an optimal hematocrit (Ht) for the maximum oxygen delivery to the brain with rHuEPO.

PATIENTS AND METHODS

Oxygen delivery was defined as a product of cerebral blood flow and arterial oxygen content (CaO2). The regional cerebral blood flow (rCBF) in each region of interest was measured by positron emission tomography and CaO2 was calculated from hemoglobin concentration, arterial oxygen saturation, and arterial oxygen tension before and after rHuEPO therapy (1,500 units, 3 times a week) in 5 HD patients (the mean age of 52 +/- 2 (SEM) years old and the mean HD duration of 98 +/- 21 months).

RESULTS

Ht rose significantly from 21 +/- 1 to 31 +/- 1% (p < 0.001) after the 3-month rHuEPO treatment in association with a significant increase in CaO2 from 7.7 +/- 0.4 to 11.6 +/- 0.3 ml O2/100 ml (p < 0.01). Hemispheric rCBF decreased significantly from 40 +/- 3 to 32 +/- 1 ml/100 g/min (p < 0.02). In all data both before and after rHuEPO treatment, Ht inversely correlated with the hemispheric rCBF (y = 55.7 - 0.76x, where y is rCBF and x is Ht, r = 0.80, p < 0.01), and positively with CaO2 (y = 0.85 + 0.34x, where y is CaO2 and x is Ht, r = 0.95, p < 0.01). By using these correlations, the hemispheric oxygen delivery was expressed as a function of Ht, being y = 47.3 + 18.3x - 0.3 x2, where y is cerebral oxygen delivery and x is Ht. From this curve, Ht at the highest cerebral oxygen delivery in the hemisphere, i.e. an optimal Ht was found to be 35.2%. Above this level of Ht, the hemispheric cerebral oxygen delivery would rather decline.

CONCLUSION

The present study indicated that Ht of about 35% is required for a better oxygen delivery to the brain metabolism during anemia correction with rHuEPO.

Combination therapy using prednisolone and cyclophosphamide slows the progression of moderately advanced IgA nephropathy

AIM

We retrospectively examined the effect of combination therapy using prednisolone (PSL) and cyclophosphamide (CPA) on the progression of IgA nephropathy (IgAN) in 45 patients with moderate to severe histological changes.

PATIENTS AND METHODS

Patients were recruited from 129 consecutive patients with IgAN seen over 10 years based on semiquantitative histological grading. They were divided into two groups: PSL+CPA group (n = 26, male/female = 11/15, age 40+/-3 years (SEM)) or control group undergone conventional therapy with or without antiplatelet agents (n = 19, male/female = 10/9, age 41+/-3). In PSL+CPA group, PSL and CPA treatment commenced using a dose of 30 and 50 mg/day, respectively. PSL was reduced by 5 mg every month.

RESULTS

The clinical parameters at the start of treatment such as age, gender, histological score, blood pressure, urinary protein excretion and serum creatinine concentration (SCr) were not different between the groups. The mean observation period in PSL+CPA group (3.3+/-0.3 years) was not different from the control group (4.0+/-0.7 years). In PSL+CPA group, urinary protein excretion, defined as the ratio of urinary protein to creatinine concentration (UP/UCr), significantly decreased from 3.9+/-0.4 to 1.3 +/-0.2 (p<0.01), whereas it remained high in the control group (3.8+/-0.7 to 2.7+/-0.8). The progression rate (PR), which was determined by the slope of the correlation between time after renal biopsy and reciprocal SCr, was significantly lower in PSL+CPA (0.054+/-0.014) than in the control group (0.172+/-0.032 dl/mg/year, p<0.001). Our results indicated that PSL+CPA combination therapy was effective in slowing the progression of moderately advanced IgAN.

CONCLUSION

We suggest that the immunosuppressive treatment with CPA is sometimes necessary to preserve renal function in patients with histologically advanced IgAN.

Successful use of single-lumen, urokinase immobilized femoral catheters as a temporary access for haemodialysis

METHODS

Placement of a femoral vein catheter as a temporary vascular access for haemodialysis was conducted and the indications, catheter patency rate, and incidence of catheter-related infections were examined. An urokinase immobilized femoral vein catheter (UIFC) is a soft polyurethane single-lumen catheter 2.7 mm in diameter and 22 cm in length which needs no heparin infusion (Japan Shawood Co., Ltd., Tokyo; Unitica Co., Ltd., Hyogo, Japan). A soft silicon rubber was attached to the tip of the catheter in order to avoid excessive bleeding during insertion. Aseptic adhesive wound dressing was employed at the exit-site which was cleansed with popidone-iodine and renewed at each dialysis session.

RESULTS

Eighty-one UIFCs were used for haemodialysis in 64 patients (acute renal failure: 11; vascular access trouble: 53; initiation of chronic dialysis: 17). The average age of the patients was 58 +/- 13 years, ranging from 26 to 80 years. The mean duration of catheter indwelling was 22.4 +/- 13.1 days. An adequate blood flow of 180-200 ml/min was obtained through UIFC and returned to another peripheral vein punctured at each dialysis session. Unexplained fever occurred in four cases while the UIFC was in place (4.9%) but culture of either blood or the catheter tip was negative for bacteria. The catheter was removed immediately and fever subsided in all cases. The overall catheter survival rate was 84% at 34 days calculated using the Kaplan-Meier method. Catheter insertion was easy to perform and no serious complications such as pulmonary embolism or septicaemia occurred.

CONCLUSION

Our modified type of UIFC is very useful as a temporary access for haemodialysis with a very low incidence of catheter-related infections and no need for heparinization. Excellent catheter patency was maintained with the plug system and careful dressing techniques without unnecessary bleeding during catheter care.