GIT (Glucose Infusion Test): Polycentric Evaluation of a New Test for Vascular Access Recirculation

Introduction

Vascular access recirculation (AR), which is often unacknowledged, remains an important cause of inadequate dialytic dose. The glucose infusion test (GIT) is a new method for detecting and quantifying AR. This paper reports on a polycentric evaluation of the new test and a comparison with the classical Urea-test (UT).

Methods

GIT protocol comprises withdrawal from the arterial port (sample A), injection into the venous drip chamber of 1 g glucose in 4 seconds, withdrawal from the arterial port (sample B) continuously from 13 to 17 seconds. Glucose is determined on A and B by a reflectance photometer. If B = A then there is no recirculation. If B exceeds A by at least 20 mg/dl there is recirculation. AR quantification: AR% = (B-A) / 20. GIT was performed on 623 patients from eleven dialysis centers to screen the patients for AR. Subsequently, GIT and Urea-test (UT) were compared in 189 paired tests. The reproducibility of GIT and UT was studied in 28 paired tests performed in sequence.

Results

The screening test by GIT was positive in 68 cases (11 %). The majority of positivities was found in central venous catheters (CVC, 27/50 cases, 54 %), whereas only 7 % of artero-venous fistulas (AVF) were positive. In the CVC group, Tesio catheters were more frequently positive compared to Dual Lumen Catheters (64 % vs. 29 %). The comparison GIT – UT showed that results matched in 162 tests (79 negative and 83 positive both by GIT and UT), showing that on the grounds of UT, GIT has high sensitivity and specificity. In 27 tests GIT was positive, but UT negative. This disagreement is due to the different minimal limit of detection, 1 % for GIT and 5% for UT. The reproducibility was greater with GIT than with UT with a lower D % (respectively −0.6 ± 2.5 and −0.4 ± 6.1 %, p<0.001) and a lower coefficient of variation (17 vs 33 %).

Conclusions

The screening of 623 patients by GIT confirmed that AR in AVF is normally absent, whereas an unexpectedly high frequency of moderate AR in CVC was found. The GIT-UT comparison showed that the new test is simple and immediate, and gives results with higher accuracy, sensitivity and reproducibility than UT.

Renal involvement in systemic amyloidosis--an Italian retrospective study on epidemiological and clinical data at diagnosis

BACKGROUND

Few data are available on epidemiology and clinical picture of renal involvement in different forms of systemic amyloidosis.

METHODS

Patients with biopsy-proven systemic amyloidosis diagnosed in Italy between January 1995 and December 2000 were selected from 49 Nephrology and Internal Medicine Units provided they showed signs characteristic of renal involvement. Clinical and laboratory information were collected by using a specific data form for diagnosis integrated by a questionnaire on diagnostic tools. Collected data were matched both with the Italian Registry of Renal Biopsies (IRRB) and the Registry of the Italian Society of Amyloidosis (SIA) in order to approximate the incidence of the disease.

RESULTS

Of all patients, 373 were finally selected throughout Italy with an estimated mean incidence of renal amyloidosis of 2.1 per million population (p.m.p.) per year. Of those, 237 were affected from AL (primary) amyloidosis, 104 from AA (secondary) amyloidosis and 6 from AF (heredofamilial) forms. In 26 cases the type of amyloidosis remained undetermined. Among patients with AL, 36 presented an associated multiple myeloma (MM). Rheumatoid arthritis (RA) was the commonest underlying disease in AA. Median age ranged between 63 and 65 years in all groups. Males were prevalent in AL and females in AA. The main clinical features of renal involvement were represented by nephrotic syndrome and renal failure observed in 59 and 54% of cases, respectively. The presence of a lambda light chain, either in serum or urine was significantly associated to a more elevated urinary protein loss and to a reduced renal function. Patients with AA showed a worse renal function at presentation than patients with AL, possibly due to a late diagnosis and/or referral to nephrology units. Diagnosis was obtained by renal biopsy in 315 cases, by abdominal fat tissue (AFT) aspiration/biopsy in 156 patients and by other organ biopsies in 47 patients. Characterization of deposits was extremely variable among referring centres.

CONCLUSIONS

Our results point to an increased incidence of renal amyloidosis observed in Italy over the period 1996-2000 with AL as the prevalent type. Characterization of amyloid deposits still remains the major diagnostic challenge of the disease. The institution of networks dedicated to rare diseases is strongly recommended in order to effectively afford this challenge.

Lp(a) levels: effects of progressive chronic renal failure and dietary manipulation

Patients with chronic renal failure (CRF) have an increased risk of cardiovascular disease (CVD). Elevated lipoprotein(a) (LP(a)) levels have been shown to be an important risk factor for CVD. This study examined Lp(a) changes during the progression of renal disease in patients following different dietary regimens. Fifty-seven patients with CRF of different etiology and degree (mean age 58 +/- 10 yrs) were divided into four groups according to their serum creatinine (sCr) levels. The first group had sCr 1.5-3; the second 3-6; the third > 6, all on a conventional low-protein diet (CLPD), and the fourth had sCr > 6 on a supplemented vegetarian diet (SVD). Lp(a), apoproteins AI, B, E, CII, CIII, CII/CIII, Apo A/Apo B ratios and the lipid pattern (total cholesterol (TC) and its fractions LDL, HDL, HDL3 and triglycerides) were investigated. Patients with diabetes, proteinuria > 1.5 g/24 h, hepatic disease or taking contraceptives or lipid lowering drugs were excluded. Results were compared with a reference group (N = 12) with sCcr < 1. Lp(a) concentrations increased with the progression of renal failure, and a significant correlation was observed with sCr. Despite the elevated sCr levels, patients on the SVD had an almost normal Lp(a) concentration. Only 15% of the reference group had Lp(a) levels > 30 mg/dl, compared to 33%, 50% and 78% of the 1st, 2nd and 3rd groups and 38% of the 4th group. No relationship was found between Lp(a), lipids or apoproteins. Our results indicate that renal function influences Lp(a) levels and suggest a SVD helps to lower them. This might be ascribed to some antioxidant factors in the SVD.

[Percutaneous nephrolithotomy of renal staghorn calculi. Experience with monotherapy treatment]

Seventy patients with renal staghorn calculi were treated with percutaneous nephrolithotripsy monotherapy. Nine patients (13%) required more than one nephrostomy to remove the stone: an overall success rate was obtained in 67% of the cases, with 27% of residual asymptomatic fragments. Open surgery was necessary in 4 patients for complications. No nephrectomies were carried out. Comparing complete and partial, better results as expected, were obtained in partial staghorn calculi. Evaluating results stratified per number of treatments, we obtained a stone-free rate of 35% with only one treatment, and 61% with two percutaneous sessions, at the discharge from the hospital. To date, initial percutaneous debulking of the stone followed by ESWL treatment on residual stones, seems to be the most suitable approach to branched calculi. However, in selected cases, PCNL treatment alone, can obtain removal of the stone in a significant percentage of cases, with minimal morbility, and, what's more, at the discharge from the hospital, without any ancillary procedure or rehospitalization.

Chronic total renal artery occlusion: a diagnostic challenge

Chronic renal artery occlusion must be suspected whenever a moderate hypertensive patient over 50 years of age presents increase of blood pressure refractory to treatment, sometimes causing heart failure or stroke. This suspicion is reinforced by the presence of renal insufficiency and of anatomical and/or functional lateralization of renal damage at intravenous pyelography.