Imaging medullary cystic kidney disease with magnetic resonance

Medullary cystic kidney disease is characterized by multiple renal cysts at the corticomedullary boundary area, by autosomal dominant inheritance, and by onset of chronic renal failure in the third decade of life. Its clinical manifestations are often insignificant and nonspecific. Furthermore, its diagnosis may be difficult in sporadic forms where genetic linkage analysis cannot be performed. The authors report the case of a patient presenting with a sporadic form of medullary cystic kidney disease whose diagnosis was confirmed using computerized tomography with 3-dimensional reconstruction at the nephrography-excretion time and magnetic resonance imaging (MRI) with magnetic resonance angiography and urography after the injection of gadolinium, a nonnephrotoxic compound. Both imaging techniques showed normal-sized, normal-shaped kidneys containing multiple cysts from 1 to 30 mm in diameter in the medulla and at the corticomedullary junction. A characteristic medullary nephrogram appeared after injection of iodinated contrast medium or gadolinium corresponding to contrast-filled dilated collecting ducts. This report shows that MRI with gadolinium injection can substitute for computerized tomography in azotemic patients. MRI seems particularly promising for the diagnosis of cystic diseases of the kidney and must also be considered when investigating a patient with chronic renal failure of unknown origin.

Nephrocalcinosis and medullary cysts in 3-methylglutaconic aciduria

3-methylglutaconic aciduria is frequently found during urine organic acid analysis and is widely regarded as a marker of a mitochondrial disorder, the clinical features of which are very heterogeneous. We describe two siblings with 3-methylglutaconic aciduria in whom renal ultrasonography showed echogenic medullae consistent with nephrocalcinosis. One patient also developed medullary cysts. In both children renal function was normal and neither had any plasma or urinary evidence of tubulopathy. The presence of nephrocalcinosis and medullary cysts in patients with 3-methylglutaconic aciduria adds to the heterogeneous clinical presentation of this group of disorders.

Mechanisms of down-regulation of the renal parathyroid hormone receptor in rats with chronic renal failure

Hypocalcemia, hyperphosphatemia and resistance to the action of parathyroid hormone (PTH) are well-characterized features in advanced chronic renal failure (CRF). Their pathogenesis has been attributed to both PTH receptor (PTH-R) down-regulation and postreceptor abnormalities. In this study, we examined the renal expression of the PTH-R mRNA in CRF (5/6 nephrectomy) rats. Experiments were also performed to determine whether an acidic condition and PTH itself influence PTH-R mRNA expression. RT-competitive PCR was used to examine mRNA expression, and polyclonal antibody against PTH-R was used for Western blot. PTH-R mRNA expression was abundant in glomeruli, proximal convoluted and straight tubules (PCT, PST), small in medullary and cortical thick ascending limbs, and cortical collecting ducts and not detectable in outer and inner medullary collecting ducts. The expression was significantly decreased in PCT and PST in CRF rats. Decrease in PTH-R mRNA expression was observed 1 week after the induction of CRF. PTH-R protein was decreased at 2 (-23%) and 4 (-45%) weeks in renal cortex, but not in medulla in CRF rats. PTH-R mRNA expression in PST was decreased by low pH (7.1 or 6.7) incubation compared with that at pH 7.4. PTH(1-34) (10(-9) M) increased PTH-R mRNA expression in PST from control rats by 250%. The stimulatory effect of PTH on PTH-R mRNA expression was decreased by the incubation at low pH medium. In summary, renal PTH-R is down-regulated in CRF rats. The decrease in mRNA expression in PCT and PST causes the decrease in PTH-R protein. Metabolic acidosis may participate in the down-regulation of PTH-R in early stage of CRF. This abnormality could be important in the pathogenesis of secondary hyperparathyroidism of CRF.

Elevated SMAD1/beta-catenin molecular complexes and renal medullary cystic dysplasia in ALK3 transgenic mice

Renal dysplasia, the most frequent cause of childhood renal failure in humans, arises from perturbations in a complex series of morphogenetic events during embryonic renal development. The molecular pathogenesis of renal dysplasia is largely undefined. While investigating the role of a BMP-dependent pathway that inhibits branching morphogenesis in vitro, we generated a novel model of renal dysplasia in a transgenic (Tg) model of ALK3 receptor signaling. We report the renal phenotype, and our discovery of molecular interactions between effectors in the BMP and WNT signaling pathways in dysplastic kidney tissue. Expression of the constitutively active ALK3 receptor ALK3(QD), in two independent transgenic lines caused renal aplasia/severe dysgenesis in 1.5% and 8.4% of hemizygous and homozygous Tg mice, respectively, and renal medullary cystic dysplasia in 49% and 74% of hemizygous and homozygous Tg mice, respectively. The dysplastic phenotype, which included a decreased number of medullary collecting ducts, increased medullary mesenchyme, collecting duct cysts and decreased cortical thickness, was apparent by E18.5. We investigated the pathogenesis of dysplasia in these mice, and demonstrated a 30% decrease in branching morphogenesis at E13.5 before the appearance of histopathogical features of dysplasia, and the formation of beta-catenin/SMAD1/SMAD4 molecular complexes in dysplastic renal tissue. Increased transcriptional activity of a beta-catenin reporter gene in ALK3(QD);Tcf-gal mice demonstrated functional cooperativity between the ALK3 and beta-catenin-dependent signaling pathways in kidney tissue. Together with our results in the dysplastic mouse kidney, our findings that phospho-SMAD1 and beta-catenin are overexpressed in human fetal dysplastic renal tissue suggest that dysregulation of these signaling effectors is pathogenic in human renal dysplasia. Our work provides novel insights into the role that crucial developmental signaling pathways may play during the genesis of malformed renal tissue elements.

ICAM-1 expression and leukocyte accumulation in inner stripe of outer medulla in early phase of ischemic compared to HgCl2-induced ARF

BACKGROUND

After ischemia/reperfusion (I/R), as well as after toxic insults, there is significant infiltration of leukocytes in the kidney. It is well known that antibodies against adhesion molecules [e.g., intercellular adhesion molecule-1 (ICAM-1)] protect the kidney against acute ischemic injury. In contrast, same antibody treatment did not protect the rat kidney against toxic acute renal failure (ARF) induced by HgCl2. Protection obtained by anti-adhesion treatment in I/R injury is an early phenomenon, since delaying the administration of anti-ICAM-1 for 8 hours did not protect the kidney anymore. The aim of this study was to compare the early ICAM-1 expression and leukocyte accumulation in different zones of ischemic and toxic injury.

METHODS

Male Lewis rats were injected with HgCl2 (2 mg/kg, subcutaneously) or uninephrectomized Lewis rats were submitted to 30 degrees C warm ischemia (I/R injury). Rats were sacrificed at 2, 6, 12 and 24 hours. ICAM-1 (1A29) expression in kidney was evaluated morphometrically. Different subsets of leukocytes were stained by immunohistochemistry and counted in cortex, the outer stripe of the outer medulla (OSOM) and the level of the inner stripe of the outer medulla (ISOM).

RESULTS

Although the functional and morphologic damage was comparable between the I/R and toxic ARF group, different ICAM-1 expression could be observed early after injury. ICAM-1 expression in the ISOM started already 2 hours after the onset of I/R injury, and was increased after 12 hours in the cortex and after 24 hours in the OSOM. In contrast, during the first 24 hours after injury, ICAM-1 expression in HgCl2-injured kidneys was not different from noninjured kidneys in the ISOM and the cortex, whereas in the OSOM, ICAM-1 expression increased. The number of polymononuclear cells (PMNs) was low in noninjured kidneys and did not increase in time after both I/R injury and after HgCl2-induced ARF. In the ISOM, significant monocyte and T-cell accumulation was observed early after I/R but not after HgCl2. There was no significant T-cell accumulation in the cortex or in the OSOM.

CONCLUSION

After HgCl2, almost no leukocyte accumulation and up-regulation of ICAM-1 was observed the first 12 hours after injury. In contrast, very early after I/R injury, increased expression of ICAM-1 goes along with monocyte and T-cell accumulation in the ISOM, endorsing this particular zone as critical in renal I/R injury. These observations contribute to the understanding why anti-ICAM-1 treatment in acute I/R injury is successful, but fails in acute toxic injury induced by HgCl2.

Subchronic and developmental toxicity studies in rats with Ac-Di-Sol croscarmellose sodium

Studies were conducted to evaluate the subchronic and developmental toxicity of Ac-Di-Sol (croscarmellose sodium). In the subchronic study, groups of Sprague-Dawley rats (20/sex/group) received 0 (control), 10000, or 50000 ppm Ac-Di-Sol in the diet for 90 consecutive days (equivalent to 757 and 893 mg/kg/day for males and females fed 10000 ppm, respectively, and to 3922 and 4721 mg/kg/day for males and females fed 50000 ppm, respectively). No mortality, clinical signs of toxicity, or adverse toxicological effects on hematology or serum chemistry parameters, feed consumption, or ophthalmologic examinations were noted in any treatment group. Body weight gain was depressed in high-dose males during the final 3 weeks. The only treatment-related histological lesion noted was moderate renal mineralization at the corticomedullary junction in one high-dose female. This lesion was not considered a specific effect of Ac-Di-Sol, but rather a secondary effect resulting from a potential increase in urinary pH and renal excretion of sodium due to the high intake of sodium associated with Ac-Di-Sol. In the developmental toxicity study, groups of pregnant Sprague-Dawley rats (25/group) received 0 (control), 10000, or 50000 ppm Ac-Di-Sol in the diet on gestational days 6 to 15. No evidence of maternal, fetal, or embryo toxicity was noted. The no-observed-adverse-effect level (NOAEL) for Ac-Di-Sol in both studies exceeds 50000 ppm in the diet, which represents doses of 3922 and 4712 mg/kg/day, for males and females, respectively. The results of these studies demonstrate the low subchronic oral toxicity and developmental toxicity of Ac-Di-Sol, and support the safe use of Ac-Di-Sol in oral applications such as pharmaceuticals, dietary supplements, and sweetener tablets.

Accumulation of 8-oxoguanine in the cellular DNA and the alteration of the OGG1 expression during ischemia-reperfusion injury in the rat kidney

During ischemia-reperfusion (I/R) injury in the rat kidney, apoptosis was observed in the distal tubules of the cortico-medullary region and outer medulla (OM) while severe necrosis was seen in the proximal straight tubules of the OM. The majority of these changes disappeared within 2 weeks. We examined the contents of 8-oxo-2'-deoxyguanosine (8-oxo-dG), which is a major type of oxidative damage in DNA, in the rat kidney during I/R injury, and also investigated the expression level of the OGG1 gene encoding the 8-oxoguanine DNA glycosylase. High-performance liquid chromatography with an MS/MS analysis of the nuclear DNA revealed an immediate accumulation of 8-oxo-dG in the nuclear DNA prepared from the cortex and OM of the kidney 1h after I/R, and an immunohistochemical analysis demonstrated the immediate accumulation of 8-oxo-dG in the nuclei of renal tubular cells both in the cortex and OM. A delayed increase of cytoplasmic staining with anti-8-oxo-dG was observed only in the cortico-medulla and OM, where the cytoplasmic staining in the proximal tubular cells is higher than in the distal tubular cells. The level of cytoplasmic staining representing 8-oxo-dG in mitochondrial DNA, peaked at 6h after I/R and preceded the necrosis of proximal tubular cells in the OM. An RNase protection assay showed a high level of OGG1 mRNA in the normal kidney, and the level decreased within 3h only in the OM, and increased thereafter 1-7 days of I/R both in the cortex and OM. In situ hybridization showed higher levels of OGG1 mRNA expression in the renal tubules in the OM than in the cortex of the normal kidney, which decreased rapidly within 3h of I/R. Thus, the accumulation of 8-oxo-dG in the mitochondrial DNA rather than in nuclear DNA is likely to be involved in the pathogenic responses such as necrosis of renal tubular cells during I/R injury of the kidney, together with an altered level of OGG1 expression.

N-acetylcysteine ameliorates renal microcirculation: studies in rats

BACKGROUND

N-acetylcysteine (NAC) administration has been shown to ameliorate experimental acute renal failure induced by ischemia-reflow, and was found to prevent radiocontrast nephropathy in high-risk patients. While the protective effect of NAC has been primarily attributed to scavenging oxygen free radicals, improving renal microcirculation also may play a role in the prevention of acute renal failure.

METHODS

This study was designed to explore the effect of NAC on renal microcirculation. Blood pressure, total renal blood flow and selective regional cortical and outer medullary blood flow were continuously monitored in anesthetized Sprague Dawley rats with ultrasonic and laser-Doppler probes during the infusion of NAC (60 mg/kg).

RESULTS

In control intact rats blood pressure and renal microcirculation were unaffected by NAC. By contrast, following renal vasoconstriction induced by the radiocontrast agent iothalamate meglumine, NAC decreased total, cortical and medullary vascular resistance by 7 to 10% (P < 0.05). NAC also reduced renal vascular resistance by 16% when given during angiotensin II infusion (P < 0.05). Altered renal microcirculation, induced by the cyclooxygenase inhibitor indomethacin, by the nitric oxide synthase-inhibitor, Nomeganitro-l-arginine (L-NAME), or with their combination was partially restored by NAC. Nevertheless, NAC administration failed to attenuate renal function and morphology in a rat model of acute renal failure with selective outer medullary hypoxic injury, induced by indomethacin, L-NAME and iothalamate.

CONCLUSIONS

NAC ameliorates renal vasoconstriction, an effect that seems to be mediated by mechanisms other than prostaglandins and nitric oxide. The potential renoprotective outcome of NAC and the role of its vasodilating effect on the pre-constricted renal vasculature should be evaluated further.

Differences in ethoxyquin nephrotoxicity between male and female F344 rats

Dose-response studies have shown a sharp threshold for the renal papillary toxic effect in male rats between 0.25% and 0.5% ethoxyquin (Eto) in the diet over 6 months. Although similar elevated urinary protein (albumin) levels resulted from dietary Eto (0.5%) in both males and females, papillary necrosis was male specific. Following [14C]Eto administration, radiolabel was associated with urinary albumin but not alpha 2 globulin (alpha(2mu)-g). Autoradiographic studies indicated that the sex differences in nephrotoxicity do not involve differences in distribution or retention of Eto. Faecal and urinary metabolic profiles were also similar in the two sexes. The sharp threshold of toxicity in the male rat could indicate a fine balance between toxifying/detoxifying metabolism of Eto.

Proximal tubular injury attenuates outer medullary hypoxic damage: studies in perfused rat kidneys

The straight segment (S3) of the proximal tubule is predominantly damaged during renal ischemia-reflow, whereas medullary thick ascending limbs (mTALs) are principally affected in other models of hypoxic acute tubular necrosis (ATN). Since the latter injury pattern largely depends on the extent of reabsorptive activity during hypoxic stress, we hypothesized that proximal tubular damage might attenuate downstream mTAL injury by means of diminished distal solute delivery for reabsorption. In isolated rat kidneys perfused for 90 min with oxygenated Krebs-Henseleit solution, mTAL necrosis developed in 75 +/- 3% of tubules in the mid-inner stripe of the outer medulla. By contrast, S3 segments in the outer stripe were minimally affected, with tubular fragmentation involving some 5 +/- 2% of tubules. In kidneys subjected in vivo to proximal tubular injury and subsequently used for isolated perfusion studies, the injury pattern was inverted: following 20 and 30 min ischemia and reflow for 24 h, S3 fragmentation rose to 18 +/- 16% and 72 +/- 13%, while mTAL damage was reduced to 33 +/- 10 and 24 +/- 8%, respectively. In kidneys subjected in vivo to D-serine S3 necrosis rose to 100%, while mTAL damage fell to 1 +/- 1% (p < 0.001). Substantial S3 tubular collapse (involving approximately 30% of tubules) and inner stripe interstitial hemorrhage were also noted, exclusively in kidneys subjected to ischemia-reflow. Proximal tubular necrosis alone or in combination with collapse inversely correlated with mTAL necrosis (R = -0.51 and -0.72, respectively, p < 0.003). This cogent inverse association might imply that disruption of the proximal nephron attenuates downstream mTAL necrosis by a reduction of distal tubular reabsorptive workload.

Effect of Poly(ADP-Ribose) Polymerase Inhibition on Outer Medullary Hypoxic Damage

Poly(ADP-ribose) polymerase (PARP) activation after free-radical-induced DNA damage depletes cellular energy stores and participates in ischemia-reflow injury. We studied the potential protective effect of the water-soluble PARP inhibitor 3-aminobenzamide (3-AB) in a rat model of acute renal failure (ARF) from combined administration of radiocontrast, indomethacin and N(omega)-nitro-L-arginine methyl ester. Kidney function at 24 h was better preserved in rats treated with 3-AB as compared to control animals. However, the extent of tubular hypoxic damage was not significantly mitigated. It is concluded that PARP inhibition may attenuate renal dysfunction in this model of ARF with medullary hypoxic tubular injury even while the extent of tubular necrosis is not significantly altered. Further studies of this dyssynchrony of structure and function may provide important insights into the sequence of events that promotes renal failure after medullary injury.

[Intramedullary spinal cord metastasis: is there a place for surgery? Case report and review of literature]

BACKGROUND AND PURPOSE

The usual onset of intramedullary spinal cord metastases at an advanced stage of cancer disease explains that surgical removal of such lesions is rarely performed. We tried to define the place for surgery in the management of such lesions.

METHODS

We report the observation of a 52-year-old male patient presenting with a metastasis of the conus medullaris revealing a lung cancer. Surgical excision of the lesion led to pain relief and improvement of bladder dysfunction. We present a review of pertinent literature.

RESULTS

Surgery allows histological diagnosis in case of isolated, revealing tumor. In other selected cases, radical removal of intramedullary metastases could improve the quality and comfort of life although it does not seem to affect the duration of survival.

Expression of the progesterone receptor and progesterone- metabolising enzymes in the female and male human kidney

Due to high binding affinity of progesterone to the human mineralocorticoid receptor (hMR), progesterone competes with the natural ligand aldosterone. In order to analyse how homeostasis can be maintained by mineralocorticoid function of aldosterone at the MR, especially in the presence of elevated progesterone concentrations during the luteal phase and pregnancy, we investigated protective mechanisms such as the decrease of free progesterone by additional binding sites and progesterone metabolism in renal cells. As a prerequisite for sequestration of progesterone by binding to the human progesterone receptor (hPR) we demonstrated the existence of hPR expression in female and male kidney cortex and medulla at the level of transcription and translation. We identified hPR RNA by sequencing the RT-PCR product and characterised the receptor by ligand binding and scatchard plot analysis. The localisation of renal hPR was shown predominantly in individual epithelial cells of distal tubules by immunohistology, and the isoform hPR-B was detected by Western blot analysis. As a precondition for renal progesterone metabolism, we investigated the expression of steroid-metabolising enzymes for conversion of progesterone to metabolites with lower affinity to the hMR. We identified the enzyme 17alpha-hydroxylase for renal 17alpha-hydroxylation of progesterone. For 20alpha-reduction, different hydroxysteroid dehydrogenases (HSDs) such as 20alpha-HSD, 17beta-HSD type 5 (3alpha-HSD type 2) and 3alpha-HSD type 3 were found. Further, we detected the expression of 3beta-HSD type 2 for 3beta-reduction, 5alpha-reductase (Red) type 1 for 5alpha-reduction, and 5beta-Red for 5beta-reduction of progesterone in the human kidney. Therefore metabolism of progesterone and/or binding to hPR could reduce competition with aldosterone at the MR and enable the mineralocorticoid function.

Rupture of a saccular renal artery aneurysm: report of a case

This paper reports a patient who was successfully treated for a ruptured renal artery aneurysm. A 64-year-old man presented with sudden onset of strong abdominal and lumbar pain, and a 2-week history of abdominal discomfort. Abdominal computed tomography and visceral arteriography revealed a retroperitoneal hematoma and a 7.5-cm saccular renal aneurysm with active bleeding. A laparotomy was indicated, and a nephrectomy was performed due to the persistent bleeding and refractory hypotension presented during surgery. The postoperative course was uneventful, and the patient was discharged with a normal renal function on the tenth day. This paper presents the successful management of a ruptured renal aneurysm with a review of the literature, and the management possibilities of such patients is also discussed.

Effect of short-term vs. long-term elevation of dietary protein intake on responsiveness of rat thick ascending limbs to peptide hormones

We compared the renal responses of rats on three diet regimens. Rats received either 8% protein food (low-protein, LP) for 10 weeks following weaning, 8% protein for 9 weeks followed by 1 week on 30% protein (short-term high-protein, SHP), or 30% protein for 10 weeks (high-protein, HP). Kidneys from HP rats were enlarged by approximately 50%, or 20% when corrected for body mass. Most of this hypertrophy resulted from enlargement of the inner stripe of the outer medulla, site of the thick ascending limbs (TAL), and TAL from HP rats were larger in diameter. SHP rats had TAL diameters similar to HP rats, but changes in renal mass or height of renal zones did not reach statistical significance. The activity of adenylyl cyclase (AC) in TAL, measured from the accumulation of cAMP in isolated tubules, increased with dose of both arginine vasopressin (AVP) and glucagon in all rats. However, HP rats had significantly higher hormone-induced AC activity than LP or SHP rats, which were not different from each other. Our results suggest that tubule hypertrophy may precede up-regulation of hormone-sensitive AC activity during the progression of renal response to elevated dietary protein.

Polyethylene glycol reduces early and long-term cold ischemia-reperfusion and renal medulla injury

Ischemia-reperfusion injury (IRI) after transplantation is a major cause of delayed graft function, which has a negative impact on early and late graft function and improve acute rejection. We have previously shown that polyethylene glycol (PEG) and particularly PEG 20M has a protective effect against cold ischemia and reperfusion injury in an isolated perfused pig and rat kidney model. We extended those observations to investigate the role of PEG using different doses (30g or 50g/l) added (ICPEG30 or ICPEG50) or not (IC) to a simplified preservation solution to reduce IRI after prolonged cold storage (48-h) of pig kidneys when compared with Euro-Collins and University of Wisconsin solutions. The study of renal function and medulla injury was performed with biochemical methods and proton NMR spectroscopy. Histological and inflammatory cell studies were performed after reperfusion (30-40 min) and on days 7 and 14 and weeks 4, 8, and 12. Peripheral-type benzodiazepine receptor (PBR), a mitochondrial protein involved in cholesterol homeostasis, was also studied. The results demonstrated that ICPEG30 improved renal function and reduced medulla injury. ICPEG30 also improved tubular function and strongly protect mitochondrial integrity. Post-IRI inflammation was strongly reduced in this group, particularly lymphocytes TCD4(+), PBR expression was influenced by IRI in the early period and during the development of chronic dysfunction. This study clearly shows that PEG has a beneficial effect in renal preservation and suggests a role of PBR as a marker IRI and repair processes.

Participation of alpha-smooth muscle actin-positive cells in renomedullary interstitial cell tumors

Renomedullary interstitial cell tumors are benign lesions which are generally discovered in specimens nephrectomized for other malignant tumors or by autopsy. We examined the histologic features of eight tumors from four patients and investigated the appearance of alpha-smooth muscle actin (ASMA)-positive cells in these tumors using immunohistochemistry. We considered that five tumors are cellular type and the remaining three as fibrous. Characteristic hyalinization was observed in two of the three fibrous tumors. All the tumors except for one fibrous type contained entrapped tubular cells. CD35-positive cells (dendritic cells) and ASMA-positive cells were observed in all the tumors, with a more frequent occurrence in the cellular type than the fibrous type. CD35-negative spindle cells were considered as fibroblasts or activated fibroblasts (myofibroblasts). The number of CD35-positive cells was higher than that of ASMA-positive cells. Additionally, the entrapped tubular cells showed the transition to spindle cells and some of them expressed for ASMA. With double immunohistochemical staining, there were some cells showing positive reactions for both CD35 and ASMA. Furthermore, an ultrastructural examination confirmed the presence of ASMA-positive filaments in the dendritic cells and myofibroblasts. The expression of TGF-beta 1 was observed not only in the tumor cells and the collecting ducts surrounding the tumor but also in the entrapped tubular cells. In addition, the intensity of TGF-beta 1 was stronger in/around the tumor than in the areas distant from the tumor. The positive cells were more numerous in the cellular type than in the fibrous type. In conclusion, ASMA-positive cells appear in renomedullary interstitial cell tumors and some of the cells may originate in dendritic interstitial cells, fibroblasts including myofibroblasts, and entrapped tubular cells. Furthermore, TGF-beta 1 may contribute to the formation of fibrosis in the tumors.

Gadolinium-enhanced T1-weighted renal and abdominal MR imaging: quantitative discrepancy between clinical and in vitro findings

RATIONALE AND OBJECTIVES

This study was conducted to compare the magnetic resonance (MR) contrast medium enhancement of abdominal organs in vivo with the signal intensity (SI) values of known in vitro gadolinium solutions.

MATERIALS AND METHODS

A phantom was imaged with the MR contrast medium gadodiamide (Omniscan; Nycomed, Princeton, NJ) of solutions at full-strength (0.5 mmol/mL), one-third, 1/10, and 1/100 concentrations. A fat-suppressed fast spoiled gradient-echo pulse sequence with flip angles ranging from 10 degrees to 170 degrees (at 20 degrees increments) was performed with a 1.5-T magnet. In 12 subjects, the SIs of abdominal organs were determined with identical imaging parameters, before and after administration of gadodiamide injection at 0.1 mmol/kg.

RESULTS

As anticipated, the plot of SI in relation to gadodiamide concentration is nonlinear, with a decrease in SI due to T2 effects at concentrations above 0.05 mmol/mL. The kidney showed the highest SI after gadodiamide enhancement (125.2 +/- 11.6 [standard error] at 2.5 minutes), followed by the liver (76.5 +/- 11.5 at 1 minute) and spleen (57.26 +/- 9.35 at 30 seconds). The SI of the renal medulla (114.2 +/- 9.8 at 4.5 minutes) was approximately one-third that in phantom observations.

CONCLUSION

The authors observed a marked discrepancy between empirical contrast medium performance in abdominal organs and SI values for comparable gadodiamide concentrations in vitro. One possible reason is the intracellular compartmentalization of water molecules in vivo. These results suggest a need for a better understanding of MR contrast medium performance in vivo.

Evaluation of superficial papillary ablation by endoscopic lasers in an ex vivo kidney model

BACKGROUND AND PURPOSE

Endoscopic examinations of stone-forming kidneys show a coincidence of plaques and microliths on the surface of and within papillary epithelial tissue. These calcifications are thought to be precursors of calcium oxalate urolithiasis. We hypothesized that minimally invasive endoscopic laser ablation of microliths and necrotic cell layers enables epithelial regeneration and prevents recurrent urolithiasis. The aim of this study was to determine the most suitable laser type and dose intensity for selective superficial cell ablation.

MATERIALS AND METHODS

Conventional Nd:YAG (1-40 W) or Ho:YAG (0.5-3 J/single impulse) lasers were used endoscopically on an ex vivo blood-perfused porcine kidney model. Defined doses were applied to the papillary surface in the contact and noncontact modes for 10 to 30 seconds. Papillae were excised after treatment and histopathologically analyzed in continuous sections. Lesions were microscopically assessed with the aid of a Leica Quantimed computer program.

RESULTS

Depending on the time and dose, vaporization by the Nd:YAG laser caused large tissue defects and coagulation necrosis at energy levels over 5 W (contact and noncontact mode). Lower energy levels with tissue contact produced only superficial cell defects (<20 cell layers) but more extensive coagulation necrosis, whereas no histologic effects were observed at the same energy level without contact. In contrast, independent of delivered energy but dependent on time, Ho:YAG laser application caused pure tissue loss without relevant coagulation necrosis. The generation of small lesions (6-10 cell layers) without tissue contact was possible at energy levels under 2 J.

CONCLUSIONS

Selective superficial papillary cell ablation is possible. Low-energy Nd:YAG treatment in the contact mode and Ho:YAG treatment in the noncontact mode led to superficial vaporization with no (Ho:YAG) or minimum (Nd:YAG) coagulation defects.

[Severe sickle cell anemia revealed in an adult by medullary necrosis]

INTRODUCTION

Drepanocytosis, even severe, may only be discovered in adults further to severe complications.

OBSERVATION

A 44 year-old woman was hospitalised for a severe vaso-occlusive crisis, revealing a drepanocyte syndrome with heterozygote S-beta zero thalassemia. Evolution was marked by severe anaemia, the aregenerative nature of which, uncommon during vaso-occlusive crises and the absence of Parvovirus B19 infection, led to the diagnosis of medullar necrosis. Evolution was rapidly improved after transfusion of erythrocyte concentrations and symptomatic treatment of the pain.

COMMENTS

Medullar necrosis is a rare entity with multiple causes. In severe drepanocyte syndromes it is concomitant to a severe vaso-occlusive syndrome, resulting from medullar ischemia due to specific microvascular damage.

Protective effect of glycine on renal injury induced by ischemia-reperfusion in vivo

Although glycine prevents renal tubular cell injury in vitro, its effect in vivo is not clear. The purpose of this study was to investigate whether a bolus injection of glycine given before reperfusion plus continuous dietary supplementation afterward would reduce renal injury caused by ischemia-reperfusion. Female Sprague-Dawley rats received a semisynthetic powdered diet containing 5% glycine and 15% casein (glycine group) or 20% casein (control group). Two days later, renal ischemia was produced by cross-clamping the left renal vessels for 15 min, followed by reperfusion. The right kidney was removed before reperfusion. The postischemic glomerular filtration rate (GFR) showed that renal function was less impaired and recovered more quickly in rats receiving glycine. For example, at day 7, GFR in controls (0.31 +/- 0.03 ml x min(-1) x 100 g(-1)) was about one-half that of glycine-treated rats (0.61 +/- 0.06 ml x min(-1) x 100 g(-1), P < 0.05). Furthermore, tubular injury and cast formation observed in controls was minimized by glycine (pathology score, 3.2 +/- 0.4 vs. 1.0 +/- 0.4, P < 0.05). Urinary lactate dehydrogenase (LDH) concentration was elevated by ischemia-reperfusion in the control group (260 +/- 22 U/l), but values were significantly lower by about fourfold (60 +/- 30 U/l) in glycine-fed rats. Similarly, free radical production in urine was significantly lower in glycine-treated animals. Importantly, on postischemic day 1, binding of pimonidazole, an in vivo hypoxia marker, was increased in the outer medulla in controls; however, this phenomenon was prevented by glycine. Two weeks later, mild leukocyte infiltration and interstitial fibrosis were still observed in controls, but not in kidneys from glycine-treated rats. In conclusion, these results indicate that administration of glycine indeed reduces mild ischemia-reperfusion injury in the kidney in vivo, in part by decreasing initial damage and preventing chronic hypoxia.

Effects of reduction of renal mass on renal oxygen tension and erythropoietin production in the rat

BACKGROUND

It is well known that the anemia of chronic renal failure is associated with a blunted erythropoietin response. However, it is not clear why this response is blunted. Oxygen tension is an important regulator of erythropoietin production and release, but the effect of reduced renal mass on renal tissue oxygen tensions is currently unknown.

METHODS

A computer-based simulation was used to determine how alterations in filtration fraction might impact on renal tissue oxygen tensions. In addition, direct measurements of oxygen tension with needle electrodes were employed, as well as conventional physiological measurements and ELISA measurements of plasma and tissue erythropoietin concentrations in rats subjected to 5/6th nephrectomy.

RESULTS

Remnant kidney rats had 39% and 52% decreases in tissue and plasma erythropoietin concentrations, respectively, that correlated with 73% increased oxygen tensions in both cortex and outer medulla in the remnant kidney (all P < 0.01). Estimations of filtration fraction were decreased by approximately 36% in the rats bearing remnant kidneys.

CONCLUSIONS

Higher oxygen tensions were observed in the remnant kidneys. We suggest that higher oxygen tensions are caused by a decrease in filtration fraction, and that these higher tissue oxygen tensions result in decreased renal erythropoietin production and anemia.

Measurement of renal volumes with contrast-enhanced MRI

PURPOSE

To determine the accuracy of in vivo magnetic resonance imaging (MRI) measurement of total renal parenchymal volume and medullary fraction.

MATERIALS AND METHODS

Sixteen kidneys in eight pigs were imaged with a multiphasic contrast-enhanced fast three-dimensional sequence on a 1.5-T imager. Kidney segmentation, followed by a process of signal intensity thresholding for cortical and nephrographic phase datasets, allowed for MRI measurements of parenchymal volume and medullary fraction. Autopsy provided reference standards of renal volume, weight, and medullary fraction.

RESULTS

An excellent correlation was found between MRI measurement of total renal parenchymal volume and autopsy volume (R2 = 0.86) and weight (R2 = 0.90). Medullary fraction (mean +/- SD) measured with MRI was 0.120 +/- 0.067, and with autopsy was 0.116 +/- 0.025 (t-test P = 0.84, F-test P = 0.001).

CONCLUSION

MRI measurements of total renal volume are accurate. MRI measurements of medullary fraction show promise, but precision is limited when using a simple signal intensity thresholding algorithm.