Modelling of icodextrin hydrolysis and kinetics during peritoneal dialysis.

In peritoneal dialysis, ultrafiltration is achieved by adding an osmotic agent into the dialysis fluid. During an exchange with icodextrin-based solution, polysaccharide chains are degraded by α-amylase activity in dialysate, influencing its osmotic properties. We modelled water and solute removal taking into account degradation by α-amylase and absorption of icodextrin from the peritoneal cavity. Data from 16 h dwells with icodextrin-based solution in 11 patients (3 icodextrin-exposed, 8 icodextrin-naïve at the start of the study) on dialysate volume, dialysate concentrations of glucose, urea, creatinine and α-amylase, and dialysate and blood concentrations of seven molecular weight fractions of icodextrin were analysed. The three-pore model was extended to describe hydrolysis of icodextrin by α-amylase. The extended model accurately predicted kinetics of ultrafiltration, small solutes and icodextrin fractions in dialysate, indicating differences in degradation kinetics between icodextrin-naïve and icodextrin-exposed patients. In addition, the model provided information on the patterns of icodextrin degradation caused by α-amylase. Modelling of icodextrin kinetics using an extended three-pore model that takes into account absorption of icodextrin and changes in α-amylase activity in the dialysate provided accurate description of peritoneal transport and information on patterns of icodextrin hydrolysis during long icodextrin dwells.

Comparison of Second- and Third-Generation Parathyroid Hormone Test Results in Patients with Chronic Kidney Disease.

BACKGROUND In patients with chronic kidney disease (CKD), secondary hyperparathyroidism is assessed by measuring serum parathyroid hormone (PTH) levels. Well-established, recommended, second-generation intact parathyroid hormone (iPTH) tests are typical; rarely are more recent third-generation PTH 1-84 assays used. The agreement between results of the 2 tests in patients with CKD has not been sufficiently defined. MATERIAL AND METHODS This study aimed to compare Roche second- and third-generation PTH assays by establishing a quantitative relationship between the results of assays in patients with CKD and assessing degree of their correlation with kidney function and calcium-phosphate and bone metabolism parameters. In 205 patients with stages 3 to 5D CKD and 30 healthy controls, we measured levels of iPTH and PTH (1-84), creatinine, urea, cystatin C, calcium, inorganic phosphate, magnesium, alkaline phosphatase, bone alkaline phosphatase, osteocalcin, and ß-CrossLaps. RESULTS The third-generation PTH assay results were more than 40% lower than those obtained with the second-generation test in patients undergoing dialysis and approximately 30% lower in patients in the pre-dialysis period. PTH concentrations determined with both assays were almost to the same extent correlated with calcium-phosphate and bone metabolism parameters, and renal function indices. Formulas have been developed enabling 2-way conversion of PTH results determined with both the second- and third-generation PTH assays: For dialyzed patients, PTH (1-84)=0.5181iPTH+18.0595. Serum osteocalcin, ß-CrossLaps, and total calcium were independent predictors of PTH levels. CONCLUSIONS Correcting for the established quantitative differences, the second-and third-generation PTH tests can be used interchangeably, given the almost identical pathophysiological correlations of their results with calcium-phosphate and bone metabolism parameters.

Long Peritoneal Dialysis Dwells With Icodextrin: Kinetics of Transperitoneal Fluid and Polyglucose Transport.

Background and objective: During peritoneal dialysis (PD), the period of effective net peritoneal ultrafiltration during long dwells can be extended by using the colloidal osmotic agent icodextrin but there are few detailed studies on ultrafiltration with icodextrin solution exceeding 12 h. We analyzed kinetics of peritoneal ultrafiltration in relation to icodextrin and its metabolites for 16-h dwells with icodextrin. Design, setting, participants, and measurements: In 20 clinically stable patients (mean age 54 years; 8 women; mean preceding time on PD 26 months), intraperitoneal dialysate volume (VD) was estimated from dilution of 125I-human serum albumin during 16-h dwell studies with icodextrin 7.5% solution. Sodium was measured in dialysate and plasma. In 11 patients, fractional absorption of icodextrin from dialysate, dialysate, and plasma amylase and high and low (Mw <2 kDa) Mw icodextrin fractions were analyzed. Results: Average VD increased linearly with no difference between transport types. At 16 h, the cumulative net ultrafiltration was 729 ± 337 ml (range -18 to 1,360 ml) and negative in only one patient. Average transcapillary ultrafiltration rate was 1.40 ± 0.36 ml/min, and peritoneal fluid absorption rate was 0.68 ± 0.38 ml/min. During 16 h, 41% of the initial mass of icodextrin was absorbed. Plasma sodium decreased from 138.7 ± 2.4 to 136.5 ± 3.0 mmol/L (p < 0.05). Dialysate glucose G2-G7 oligomers increased due to increase of G2-G4 metabolites while G6-G7 metabolites and higher Mw icodextrin fractions decreased. In plasma maltose and maltotriose (G2-G3 metabolites) increased while higher Mw icodextrin oligomers were almost undetectable. Dialysate amylase increased while plasma amylase decreased. Conclusions: Icodextrin resulted in linear increase of VD with sustained net UF lasting 16 h and with no significant difference between peritoneal transport types. In plasma, sodium and amylase declined, G2-G3 increased whereas larger icodextrin fractions were not detectable. In dialysate, icodextrin mass declined due to decrease of high Mw icodextrin fractions while low Mw metabolites, especially G2-G3, increased. The ability of icodextrin to provide sustained UF during very long dwells - which is usually not possible with glucose-based solutions - is especially important in anuric patients and in patients with fast peritoneal transport.

Role of Nitric Oxide Pathway in Development and Progression of Chronic Kidney Disease in Rats Sensitive and Resistant to its Occurrence in an Experimental Model of 5/6 Nephrectomy.

BACKGROUND Understanding the mechanisms conditioning development of chronic kidney disease (CKD) is still a challenge. The aim of this study was to evaluate the activity of the intrarenal nitric oxide (NO) pathway in the context of sensitivity or resistance of different animal strains to the development and degree of renal failure. MATERIAL AND METHODS Two rat strains were used: Wistar (WR) and Sprague-Dawley rats (SDR) in a model of CKD - 5/6 nephrectomy. We assessed parameters of renal failure and expression of nitric oxide synthase (NOS) isoforms in renal cortex and medulla. RESULTS We did not observe renal failure in WR, and CKD developed in SDR with increase of creatinine and urea concentration as well as decrease of diuresis and glomerular filtration. In the renal cortex, baseline expression of NOS2 was higher in WR than in SDR. 5/6 nephrectomy resulted in reduction of NOS2 in both strains and NOS3 in WR. In the renal medulla, baseline NOS2 expression was higher in SDR, and nephrectomy resulted in its decrease only in SDR. Although baseline NOS3 expression was higher in SDR, the NOS3 expression after nephrectomy was higher in WR rats. CONCLUSIONS In model of CKD - 5/6 nephrectomy, SDR proved to be sensitive and WR resistant to development of CKD. The intrarenal activity of the nitric oxide pathway was the factor that differentiated both strains. This mechanism may be responsible for insensitivity of WR to development of renal failure in this model of CKD.

Changes of peritoneal transport parameters with time on dialysis: assessment with sequential peritoneal equilibration test.

BACKGROUND: Sequential peritoneal equilibration test (sPET) is based on the consecutive performance of the peritoneal equilibration test (PET, 4-hour, glucose 2.27%) and the mini-PET (1-hour, glucose 3.86%), and the estimation of peritoneal transport parameters with the 2-pore model. It enables the assessment of the functional transport barrier for fluid and small solutes. The objective of this study was to check whether the estimated model parameters can serve as better and earlier indicators of the changes in the peritoneal transport characteristics than directly measured transport indices that depend on several transport processes. METHODS: 17 patients were examined using sPET twice with the interval of about 8 months (230 ± 60 days). RESULTS: There was no difference between the observational parameters measured in the 2 examinations. The indices for solute transport, but not net UF, were well correlated between the examinations. Among the estimated parameters, a significant decrease between the 2 examinations was found only for hydraulic permeability LpS, and osmotic conductance for glucose, whereas the other parameters remained unchanged. These fluid transport parameters did not correlate with D/P for creatinine, although the decrease in LpS values between the examinations was observed mostly for patients with low D/P for creatinine. CONCLUSIONS: We conclude that changes in fluid transport parameters, hydraulic permeability and osmotic conductance for glucose, as assessed by the pore model, may precede the changes in small solute transport. The systematic assessment of fluid transport status needs specific clinical and mathematical tools beside the standard PET tests.

New Options of Apheresis in Renal Diseases: How and When?

The 100-year anniversary of the first experimental apheresis performed by John Abel on uremic dogs in 1914 provides the opportunity for discussion on the current state of classic apheresis as well as technological progress and clinical experiences with its new options presented in the world literature in the last 15 years, such as the following: double filtration, plasma adsorption and immunoadsorption, leuko- and cytapheresis and low-density lipoprotein apheresis. In our review, we highlight the potential limitations for further development of those highly promising techniques, such as the following: the lack of multicenter, controlled clinical studies; insufficient knowledge of the mechanisms of those techniques and last but not least, the restricted access to apheresis, caused both by high expenditure and organizational negligence, even in highly developed countries. Special attention was paid to the most recent recommendations by the American Society of Apheresis in primary and secondary renal diseases, which are the subject of our professional interest.

Peritoneal Fluid Transport rather than Peritoneal Solute Transport Associates with Dialysis Vintage and Age of Peritoneal Dialysis Patients.

During peritoneal dialysis (PD), the peritoneal membrane undergoes ageing processes that affect its function. Here we analyzed associations of patient age and dialysis vintage with parameters of peritoneal transport of fluid and solutes, directly measured and estimated based on the pore model, for individual patients. Thirty-three patients (15 females; age 60 (21-87) years; median time on PD 19 (3-100) months) underwent sequential peritoneal equilibration test. Dialysis vintage and patient age did not correlate. Estimation of parameters of the two-pore model of peritoneal transport was performed. The estimated fluid transport parameters, including hydraulic permeability (LpS), fraction of ultrasmall pores (α u), osmotic conductance for glucose (OCG), and peritoneal absorption, were generally independent of solute transport parameters (diffusive mass transport parameters). Fluid transport parameters correlated whereas transport parameters for small solutes and proteins did not correlate with dialysis vintage and patient age. Although LpS and OCG were lower for older patients and those with long dialysis vintage, αu was higher. Thus, fluid transport parameters--rather than solute transport parameters--are linked to dialysis vintage and patient age and should therefore be included when monitoring processes linked to ageing of the peritoneal membrane.

Can Echocardiography, Especially Tricuspid Annular Plane Systolic Excursion Measurement, Predict Pulmonary Hypertension and Improve Prognosis in Patients on Long-Term Dialysis?

In recent years, increasing attention has been paid to pulmonary hypertension (PH) as a strong and independent risk factor for adverse outcome in the population of patients on long-term dialysis. Published results of observational studies indicate that the problem of PH refers mostly to patients on long-term hemodialysis and is less common in peritoneal dialysis patients. The main cause of this complication is proximal location of the arteriovenous fistula, causing chronically increased cardiac output. This paper presents the usefulness of transthoracic echocardiography (TTE) for measurement of the Tricuspid Annular Plane Systolic Excursion (TAPSE) in the early diagnosis of PH in dialysis patients. Echocardiographic diagnosis of pulmonary hypertension with TTE, especially in the case of HD patients, ensures the selection of the proper location for the first arteriovenous fistula and facilitates the decision to switch to peritoneal dialysis or to accelerate the process of qualification for kidney transplantation.

Denial Defense Mechanism in Dialyzed Patients.

BACKGROUND: It is a struggle to identify the most adaptive coping strategies with disease-mediated stress. Here, we hypothesize that intensity of coping strategies, including denial, in patients with end-stage renal disease (ESRD), varies with type of renal replacement therapy (RRT). MATERIAL AND METHODS: We enrolled 60 in-center hemodialyzed patients (HD) and 55 patients treated with continuous ambulatory peritoneal dialysis (CAPD). We administered the Coping Inventory with Stressful Situation, Profile of Mood States, and Stroop Anxiety Inventory to measure patient coping strategies in the context of their ESRD. Denial defense mechanism was measured via the IBS-R/ED. The Nottingham Health Profile was used to evaluate self-perceived quality of life. Serum potassium, urea, creatinine, phosphorus, calcium, albumin, and hematocrit were utilized as the measurements of adequacy of dialysis. RESULTS: HD patients had higher self-reported intensity of denial mechanism and avoidance-oriented strategies versus CAPD patients. Because a single strategy is almost never employed, we conducted cluster analysis. We identify 3 patterns of coping strategies using cluster analysis. "Repressors" employed denial and avoidance strategies and were predominant in HD. The second cluster consists of subjects employing predominantly task-oriented strategies with equal distribution among dialyzed patients. The third cluster encompassed a small group of patients who shared higher intensity of both denial and task-oriented strategies. Health-related outcome, anxiety, and mood profile were similar across all patients. CONCLUSIONS: HD patients predominantly used "repressive" strategies. Patients on RRT utilized denial and avoidance-based strategies to achieve satisfactory outcome in terms of perceived quality of life. We conclude that these coping mechanisms that were previously thought to be inferior are beneficial to patient compliance with RRT.

D-Galactosamine Intoxication in Experimental Animals: Is it Only an Experimental Model of Acute Liver Failure?

BACKGROUND: Short-term administration of Galactosamine to experimental animals causes liver damage and acute liver failure (ALF), as well as acute renal failure in some cases. The aim of our study was to describe kidney disorders that developed in the course of galactosamine-induced liver failure. MATERIAL AND METHODS: Sprague-Dawley rats were randomly divided into 2 groups: a study group administered galactosamine intraperitoneally and a control group administered saline. RESULTS: All the animals in the study group developed liver damage and failure within 48 h, with significant increase of alanine (p<0.001), aspartate aminotransferases (p<0.0001), bilirubin (p<0.004), and ammonia (p<0.005) and decrease of albumin (p<0.001) concentrations. Acute renal failure was observed in all test animals, with a significant increase in creatinine (p<0.001) and urea (p<0.001) concentrations and a decrease in creatinine clearance (p<0.0012). Moreover, osmotic clearance (p<0.001), daily natriuresis (p<0.003), and fractional sodium excretion (p<0.016) decreased significantly in this group of animals. The ratio of urine osmolality to serum osmolality did not change. Histopathology of the liver revealed massive necrosis of hepatocytes, whereas renal histopathology showed no changes. CONCLUSIONS: Acute renal failure that developed in the course of galactosamine-induced ALF was of a functional nature, with the kidneys retaining the ability to concentrate urine and retain sodium, and there were no renal changes in the histopathological examination. It seems that the experimental model of ALF induced by galactosamine can be viewed as a model of hepatorenal syndrome that occurs in the course of acute damage and liver failure.

Hepatoprotective effect of nitric oxide in experimental model of acute hepatic failure.

AIM: To evaluate the effect of nitric oxide (NO) on the development and degree of liver failure in an animal model of acute hepatic failure (AHF). METHODS: An experimental rat model of galactosamine-induced AHF was used. An inhibitor of NO synthase, nitroarginine methyl ester, or an NO donor, arginine, were administered at various doses prior to or after the induction of AHF. RESULTS: All tested groups developed AHF. Following inhibition of the endogenous NO pathway, most liver parameters improved, regardless of the inhibitor dose before the induction of liver damage, and depending on the inhibitor dose after liver damage. Prophylactic administration of the inhibitor was more effective in improving liver function parameters than administration of the inhibitor after liver damage. An attempt to activate the endogenous NO pathway prior to the induction of liver damage did not change the observed liver function parameters. Stimulation of the endogenous NO pathway after liver damage, regardless of the NO donor dose used, improved most liver function parameters. CONCLUSION: The endogenous NO pathway plays an important role in the development of experimental galactosamine-induced AHF.

Long-term cholecalciferol administration in hemodialysis patients: a single-center randomized pilot study.

BACKGROUND: Data on the potent pleiotropic extraskeletal effects of vitamin D have renewed interest in its use in selected populations, including patients with chronic kidney disease, but the available data are still insufficient to make recommendations. This study assessed the long-term effect of small cholecalciferol doses on serum vitamin D, parathormone (PTH), and bone mineral density (BMD) in hemodialysis patients. MATERIAL/METHODS: Nineteen patients with serum 25(OH)D <20 ng/mL were randomized into cholecalciferol (2000 IU 3×/week) and no-treatment groups, then observed for 1 year. Patients with hypercalcemia, hyperphosphatemia, and receiving vitamin D/calcimimetics were excluded. Serum 25(OH)D, 1,25(OH)2D, PTH, and alkaline phosphatase activity were examined every 2 months and BMD was measured before and after the study. RESULTS: We observed normalization of serum 25(OH)D with an increase in medians from 11.3 to 44.9 ng/mL (P=0.02) in the cholecalciferol group and no change in the controls (P<0.001). Simultaneously, median serum 1,25(OH)2D increased from 18.2 to 43.1 pmol/L (P=0.02) in the cholecalciferol group and from 10.6 to 21.2 pmol/L (P=0.02) in controls (P=0.013). The treatment was associated with a small increase in serum calcium, but serum phosphate, PTH, alkaline phosphatase, and BMD remained unchanged in both groups. CONCLUSIONS: Oral cholecalciferol at a dose of 2000 IU/3×/week is an effective and safe way to treat vitamin D deficiency in hemodialysis patients, leading to a significant increase in serum 1,25(OH)2D. However, it was insufficient to suppress the activity of parathyroid glands or to significantly change BMD.

Effect of nitric oxide pathway regulation on water/sodium balance and renal function in a rodent model of acute liver and renal failure.

BACKGROUND: The pathomechanism of acute hepatorenal syndrome (HRS), a particular form of acute renal failure that occurs in the course of acute liver injury, is still poorly understood. The aim of our study was to estimate the influence of the activation and inhibition of the nitric oxide pathway on the water/sodium balance and development of acute renal failure in the course of HRS. MATERIAL AND METHODS: We used male Sprague-Dawley rats in the acute galactosamine (Ga1N) model of HRS. The nitric oxide synthase (NOS) inhibitors L-NAME and L-arginine were administered intraperitoneally before and after liver damage. RESULTS: HRS developed in all tested groups. L-NAME increased osmotic clearance and urine volume more effectively before liver injury. Furthermore, administration of L-NAME increased creatinine clearance both before and after Ga1N injection. A double dose of L-NAME did not yield further improvement before Ga1N injection, but improved creatinine clearance after Ga1N intoxication. Injection of L-arginine increased sodium excretion and urine volume, but only after liver injury. Moreover, L-arginine injected after Ga1N caused significant improvement of the creatinine clearance in a dose-dependent manner. CONCLUSIONS: Our study shows that inhibition of the nitric oxide pathway improves parameters of water and sodium balance and prevents development of acute renal failure in the course of acute liver injury and liver failure. Activation of the nitric oxide system also has a favorable influence on water/sodium balance and renal failure, but only after liver injury.

Percutaneous translumbar catheterization of the inferior vena cava as an emergency access for hemodialysis - 5 years of experience.

PATIENTS AND METHODS: In this study, 13 patients (11 men and 2 women) undergoing hemodialysis (HD) with the use of a catheter placed into the inferior vena cava with percutaneous translumbar access were retrospectively evaluated. In the studied group, 16 procedures of percutaneous translumbar catheterization were performed. Complications connected with the presence of catheter, such as hematoma, thrombosis, infection, catheter movement or unsuccessful catheterization, were analyzed. Moreover, another aspect of our report was to evaluate the adequacy of HD treatment performed by lumbar catheter. RESULTS: The total time of translumbar catheter observation was 4,169 days. Average time of their functioning was 261 days. The most frequent reason for termination of the use of translumbar HD catheters was spontaneous/idiopathic removal - 2 cases. Episodes of infection and thrombosis per 1,000 days of catheter observation were 2.2 and 1.2, respectively. CONCLUSIONS: Based on our study, we can conclude that correctly performed percutaneous translumbar catheterization of the inferior vena cava, in order to produce a long-term vascular access for HD, is a valuable and safe method in patients after depletion of standard vascular accesses.

The role of technological progress vs. accidental discoveries and clinical experience.

The 50th anniversary of dialysotherapy celebrated by nephrologists around the world in 2012 provided an opportunity for discussion on the role of clinical experience in relation to technological progress in the evolution of dialysis, especially of recently observed inadequate decrease in mortality/morbidity rates of patients on chronic dialysis. My report, based on almost 50 years of career in nephrology, refers the evolution of dialysis, from catharsis to modern dialysotherapy with special attention devoted to nowadays gravely underestimated role of clinical experience and personalized professional care for patients.

Methods of central vascular access for haemodialysis.

The basic form of renal replacement therapy is haemodialysis. The duration and efficacy of this treatment depends on well-functioning vascular access. Short-term or long-term catheters are used if the arterial-venous fistula placement is not possible or not indicated. According to the recommendations of the NKF DOQI (National Kidney Foundation Disease Outcomes Quality Initiative), the first choice of access is the right internal jugular vein, and the next are the left internal jugular, femoral and subclavian vein. In this article, we present approaches to the abovementioned veins for haemodialysis cathether insertion as well as catheter tip positioning in the venous system to prevent serious complications.

Echocardiographic markers of left ventricular dysfunction among men with uncontrolled hypertension and stage 3 chronic kidney disease.

BACKGROUND: Current guidelines for the management of arterial hypertension (AH) emphasize the importance of diagnosing subclinical organ damage, which determines cardiovascular prognosis. The aim of our study was to evaluate the prevalence of left ventricular hypertrophy (LVH), LV geometry patterns, and LV systolic/diastolic dysfunction among men with uncontrolled AH and chronic kidney disease (CKD) stages 3A and 3B. MATERIAL/METHODS: The study group included 256 men with essential AH. Glomerular filtration rate (eGFR) was calculated by the simplified MDRD equation. Left ventricular structure and function were assessed using echocardiography. RESULTS: Target blood pressure values were observed in 44 (17.2%) patients. In the studied group, eGFR <60 ml/min/1.73 m2 was found in 67 (26.2%) subjects. Forty-nine (19.14%) patients were in stage 3A and 18 patients (7.03%) in stage 3B of CKD. We demonstrated that LVEDD, LA, RWT, and LVMI ECHO parameters were distinctly higher (p<0.05) in poorly controlled hypertensive patients in CKD stage 3B when compared with patients in CKD stage 3A. A significantly higher prevalence of LVH, including LV eccentric hypertrophy, was observed in stage 3B when compared to stage 3A of CKD (p<0.05). LVEF and E/A ratio decreased along with the decline of renal function (p<0.05). CONCLUSIONS: Relationships between eGFR values and echocardiographic abnormalities of LV structure and function observed by us support the division of CKD stage 3 into 2 substages, 3A and 3B, as proposed by recently published guidelines. Intensification of therapeutic regimen in the CKD 3B substage is therefore crucial from both cardiological and nephrological perspectives.

Diuretic-resistant congestive heart failure treated successfully with peritoneal ultrafiltration.

We present a case of successful peritoneal ultrafiltration (pUF) treatment in a 60 year-old patient diagnosed with diuretic-resistant congestive heart failure fulfilling the criteria for type 2 cardio-renal syndrome. Six months of pUF treatment with one daily dialysis exchange with icodextrin as an osmotic agent resulted in better functional status (from IV to II/III NYHA class), quality of life and improvement of haemodynamic parameters measured by impedance cardiography. During the follow-up (six months), pUF was well tolerated by the patient and he did not require hospitalisation for decompensated heart failure.

Sequential peritoneal equilibration test: a new method for assessment and modelling of peritoneal transport.

BACKGROUND: In spite of many peritoneal tests proposed, there is still a need for a simple and reliable new approach for deriving detailed information about peritoneal membrane characteristics, especially those related to fluid transport. METHODS: The sequential peritoneal equilibration test (sPET) that includes PET (glucose 2.27%, 4 h) followed by miniPET (glucose 3.86%, 1 h) was performed in 27 stable continuous ambulatory peritoneal dialysis patients. Ultrafiltration volumes, glucose absorption, ratio of concentration in dialysis fluid to concentration in plasma (D/P), sodium dip (Dip D/P Sodium), free water fraction (FWF60) and the ultrafiltration passing through small pores at 60 min (UFSP60), were calculated using clinical data. Peritoneal transport parameters were estimated using the three-pore model (3p model) and clinical data. Osmotic conductance for glucose was calculated from the parameters of the model. RESULTS: D/P creatinine correlated with diffusive mass transport parameters for all considered solutes, but not with fluid transport characteristics. Hydraulic permeability (L(p)S) correlated with net ultrafiltration from miniPET, UFSP60, FWF60 and sodium dip. The fraction of ultrasmall pores correlated with FWF60 and sodium dip. CONCLUSIONS: The sequential PET described and interpreted mechanisms of ultrafiltration and solute transport. Fluid transport parameters from the 3p model were independent of the PET D/P creatinine, but correlated with fluid transport characteristics from PET and miniPET.