Search

The use of renal resistive indices (RRIs) for the study of renal microcirculation has in the past been proposed for the identification of renal organ damage or even to specifically identify injury to some areas of the renal parenchyma. Nevertheless, according to the most recent evidences from literature this organ-based conception of RRIs has been proven to be partial and unable to explain the RRIs variations in clinical settings of sepsis or combined organ failure of primitively extrarenal origin or, more generally, the deep connection between RRIs and hemodynamic factors such as compliance and pulsatility of the large vessels. The aim of this review is to explain the physiopathological basis of RRIs determination and the most common interpretative errors in their analysis. Moreover, through a comprehensive vision of these Doppler indices, the traditional and emerging clinical application fields for RRIs are discussed.

In recent years, novel anticoagulant drugs have been introduced in the clinical armamentarium and have progressively gained momentum. Although their use is increasing among CKD patients, some skepticism about their risk–benefit ratio still persists. We sought to investigate the safety and effectiveness of rivaroxaban in a cohort of moderate-to-advanced CKD patients. This observational, retrospective, longitudinal study involved 347 consecutive CKD stage 3b–4 (according to NKF–KDOQI guidelines) patients enrolled from 8 cardiac outpatient clinics between March 2015 and October 2017. All patients received anticoagulation (100 warfarin vs. 247 rivaroxaban) as part of their non-valvular atrial fibrillation management at the attending physician’s discretion. Clinical effectiveness (defined as the occurrence of ischemic stroke, venous thromboembolism, or transient ischemic attack) and safety (intracranial hemorrhage, gastrointestinal or other bleeding) were assessed separately. Over a mean follow-up period of 16 ± 0.3 months, 25 stroke episodes (15 hemorrhagic, and 10 ischemic) occurred in 24 warfarin treated patients vs. none in the rivaroxaban arm. There were 5 vs. 0 episodes of deep venous thrombosis and 8 vs. 2 major episodes of bleeding in the warfarin and rivaroxaban groups, respectively. In contrast, the proportion of minor episodes of bleeding was similar between groups. Rivaroxaban seems a safe and effective therapeutic option in CKD stage 3b–4 patients. However, future randomized controlled trials are needed to definitively establish the role of rivaroxaban in CKD patients.

Patients undergoing abdominal aortic aneurysm (AAA) surgery with suprarenal clamping are at high risk for acute kidney injury (AKI) and major cardiac and cerebrovascular events (MACCE). We aimed to assess whether the stroke volume variation (SVV), a measure of hemodynamic instability, is associated with AKI in hypertensive patients undergoing elective AAA surgery with suprarenal clamping. In a cohort of 51 hypertensive patients, we performed serial measurements of SVV (n = 459) and serum creatinine (sCr) (n = 255). AKI was defined according to the KDIGO clinical practice guidelines. Data were analyzed by repeated-measures ANOVA and regression analysis of time-integrated changes of both SVV and sCr. AKI developed in 45% of patients (stage 1: 31%; stage 2: 10%; stage 3: 2%). The diuresis during surgery (beta − 0.29 Z-score 95% [CI − 0.54, − 0.05]; p = 0.02), clamp time (beta 0.29 Z-score [0.05–0.52]; p = 0.02), and time-integrated changes in SVV from baseline to 12 h after surgery (beta 0.31 Z-score [0.03–0.60]; p = 0.03) were independent predictors of the time-integrated changes in sCr from baseline to 48 h after the end of surgery. In a model adjusted for age and sex, patients with AKI had an increased risk for MACCE during a mean follow-up of 3.5 ± 1.1 years (HR 5.53 [1.52–20.06]; p = 0.004). SVV increases progressively during and after AAA surgery in subjects who will develop AKI. The increase of SVV precedes and predicts the rise in sCr and is a good discriminator of the development of AKI. AKI is associated with an increased long-term risk for MACCE.

Hypomagnesemia is a common but often overlooked problem in hospitalized patients. Unrecognized hypomagnesemia can cause serious complications. The association of hypokalemia and hypocalcemia is strongly evocative of a magnesium deficiency. Research into the causes of hypomagnesemia is imperative, as it will definitely change the approach, treatment and prognosis. We report the case of a 65-year-old man with chronic hypocalcemia and hypokalemia associated with cerebellar syndrome, a solitary seizure and cerebellar hyperintensities on magnetic resonance imaging. After the detection and treatment of hypomagnesemia with oral supplements of magnesium and the replacement of pantoprazole with ranitidine, we observed immediate relief of the symptoms. In conclusion, in clinical practice, magnesium depletion should be investigated in elderly patients with hypocalcemia treated with proton pump inhibitors for many years, in particular in the presence of neurological disorders.

In Part II of our work we approach the problem discussed in Part I from the new viewpoint of canonical factorizations of a certain nth order differential operator L. The main results include: (i) characterizations of the set of relations $$ f^{(k)} (x) = P^{(k)} (x) + o^{(k)} (x^{\alpha _n - k} ),x \to + \infty ,0 \leqslant k \leqslant n - 1, $$ where $$ P(x) = a_1 x^{\alpha _1 } + \cdots + a_n x^{\alpha _n } and \alpha _1 > \alpha _2 > \cdots > \alpha _n , $$ by means of suitable integral conditions (ii) formal differentiation of a real-power asymptotic expansion under a Tauberian condition involving the order of growth of L (iii) remarkable properties of asymptotic expansions of generalized convex functions.

In two papers, the problem of formal differentiation of an asymptotic expansion in the real domain of type $$ f(x) - a_1 x^{\alpha _1 } + \cdots + a_n x^{\alpha _n } + o(x^{\alpha _n } ),x \to + \infty , $$ is amply studied. In Part I, we show that the classical viewpoints and techniques concerning formal differentiation of an asymptotic relation $$ f(x) - ax^\alpha + o(x^\alpha ),x \to + \infty , $$ give either unsatisfactory or partial results when applied to an asymptotic expansion with at least two meaningful terms. Simple examples show that some of these results are the best possible in the classical context. Hence a change of viewpoint is necessary to arrive at useful results.

The problem of the existence of an asymptotic expansion of type $$ f(x) = a_n x^n + a_{n - 1} x^{n - 1} + \cdots + a_i x^i + o(x^i ), x \to + \infty , $$ is thoroughly studied, comparing and completing the known results obtained through the three different approaches mentioned in the title. A unifying thread is provided by the canonical factorizations of the differential operator D n. Particularly meaningful are several characterizations of the polynomial asymptotic expansions of an nth order convex function.

To the Editor Renal parapelvic calcifications are frequent ultrasonographic findings but are not always solely an expression of lithiasis; they may also occur in the setting of arterial aneurysms. Renal artery aneurysms account for 22 % of all visceral aneurysms, with a reported incidence of 0.7–1.0 % in large-scale screening studies [1–3]. Ultrasound plays a major role in the diagnosis of renal artery aneurysms, primarily because it is comparatively inexpensive, widely available and risk-free. However, this diagnostic approach has certain risks, as exemplified by the case we describe below. A 66-year-old Caucasian female with a history of hypertension and dyslipidemia was referred to our department for a colour Doppler examination. The aim of the examination was to exclude the presence of renal artery stenosis. Serum creatinine, blood urea and urinalysis were within normal limits. Abdominal ultrasonography (Sequoia Acuson 512 system, 4.0 MHz electronic probe, Siemens), revealed a roughly hyperechoic parapelvic mass in the right kidney, with a wide posterior shadow cone which made it impossible to study the entire structure of the lesion adequately, either with colouror power-flow. The mass had been previously described as lithiasis, but a hypoechoic space was noted below the hyperechoic stria (Fig. 1a). To better ascertain the nature of the lesion, contrast-enhanced ultrasonography was performed which revealed contrast medium flow below the hyperechoic structure, as through a vessel. This suggested a calcified renal artery aneurysm (Fig. 1b). Confirmatory contrast-enhanced computed tomography (CT) was then performed which revealed a 27 9 25-mm saccular aneurysm of the right renal artery middle branch (Fig. 1c). This case highlights the need to carefully examine renal vessels when performing renal ultrasonography, particularly when parapelvic calcifications are noted. Aneurysms may be identified along the entire course of the main renal artery as an outpouching tract, containing colour flow. Slow velocities and whirling flow patterns can usually be observed on Doppler studies. However, a calcified renal artery aneurysm may be difficult to distinguish from lithiasis or complicated cyst based only on power, colour or pulsed Doppler, due to the frequent presence of a posterior shadow cone. In this instance, contrast-enhanced ultrasonography might help clinicians in the diagnosis, thanks to low mechanical index and the use of contrast medium. A. Granata A. Clementi Department of Nephrology and Dialysis, ‘‘San Giovanni di Dio’’ Hospital, ASP, Agrigento, Italy

Behcet’s disease (BD) is characterised by oral aphthosis, uveitis, genital ulcers and skin lesions such as folliculitis and erythema nodosum [1, 2]. Glomerulonephritis is not a recognised feature of BD [3]. Only few cases of nonnephrotic focal segmental glomerulosclerosis (FSGS) associated with BD were reported [3, 4]. We report the Wrst case of nephrotic FSGS, associated with BD, successfully treated with cyclosporin (CsA). A 19-year-old man, admitted in our Department for nephrotic syndrome, showed oral ulcers, periodically recurring from at least 3 years, monocular right-sided uveitis, arthritis, leg thrombophlebitis and cutaneous vasculitis. There was no history of genital ulcers or erythema nodosum. HLA typing showed positive HLA B51, and the diagnosis of BD was made. He reported a history of mild hypertension from 2 years, well controlled through low-sodium diet and ramipril 5 mg/ day. Blood urea was 104 mg/dl and creatinine 1.9 mg/dl. Total serum proteins were 5.5 g/dl and serum albumin 2.9 g/dl. Twenty-four-hour urinary protein excretion was 4.2 g/day. Serum immunoglobulins were within normal levels. Serological tests for rheumatoid factor, antinuclear, anti-DNA and antineutrophil cytoplasmic antibody and cryoglobulins were negative. Urinalysis showed 4–6 leucocytes and 10–15 red blood cells/hpf. There was no evidence of complement factor C3 and C4 consumption. Chest X-ray, renal ultrasonography and ECG were normal. A percutaneous eco-guided renal biopsy was then performed. At light microscopy, 19 glomeruli were disclosed. Three glomeruli showed segmental sclerosis and collapse of the glomerular tuft with podocyte hyperplasia, suggesting the diagnosis of collapsing FSGS. There was no mesangial proliferation. Both IgM (1+) and C3 (1+) in mesangial area and IgG (1+) in glomerular basement membranes were detected by immunoXuorescence. Oral prednisone (1 mg/kg/day, alternate day), CsA 200 mg/day, ramipril 10 mg/day, furosemide 100 mg/day and atorvastatin 40 mg/day were started. At 1 month, his 24-h proteinuria was 425 mg and his serum creatinine was 1.3 mg/dl. At 6 months, his 24-h proteinuria was 489 mg and his serum creatinine was 1.3 mg/dl. Oral steroids were withdrawn from therapy at 6 months. This total remission remained stable at 4 years from the biopsy, with a 24-h proteinuria of 356 mg and a serum creatinine of 1.2 mg/dl. Daily treatment with CsA 100 mg, ramipril 10 mg and atorvastatin 40 mg was maintained. This is the only case reported with FSGS at nephrotic presentation in BD in our knowledge. He responded with total remission to a treatment with CsA, steroids, ACE inhibitors and statins. Dermatologists, rheumatologists and ophthalmologists taking care of BD patients should be aware about potential renal involvement and therefore periodic urine examination and serum creatinine monitoring should be part of the management protocol. A. Granata (&) Department of Nephrology and Dialysis, AOU “Policlinico Vittorio Emanuele”, Catania, Italy e-mail: antonio.granata4@tin.it