Treatment of experimental pyelonephritis in the monkey

The effect of vitamin A on renal damage following acute pyelonephritis in children

Animal studies suggest that administration of vitamin A to rats with experimental urinary tract infection decreases the frequency of renal scars (Kavukçu et al., BJU Int 83(9):1055-1059, 1999). The aim of this study was to determine the effect of vitamin A on the rate of permanent renal damage in children with acute pyelonephritis. Fifty children, median age of 24 months (range 2-144), with first-time pyelonephritis verified by an uptake defect on acute dimercaptosuccinic acid (DMSA) scan were included in the study and randomly allocated to the case or control groups. All were given intravenous ceftriaxone for 10 days followed by oral cephalexin for 3 months. Cases in addition were given a single intramuscular dose of vitamin A, 25,000 U for infants below 1 year of age and 50,000 U for older children. At the repeat DMSA scan after 3 months, five of 25 cases (20%) and 17 of 25 controls (68%) had abnormal findings (p = 0.001). In conclusion, administration of vitamin A was associated with a significantly lower rate of permanent renal damage.

Vitamin E administration at the onset of fever prevents renal scarring in acute pyelonephritis

We evaluated the protective effects of antioxidant at the onset of fever on renal damage in a rat model of acute pyelonephritis. Twenty rats were allocated to four groups. In groups 1 to 3, the animals were given direct inoculation of Escherichia coli into the right kidney, and group four served as control. All rats in groups 1 to 3 were given once-daily intraperitoneal injections of ceftriaxon for five consecutive days, beginning on the third day after inoculation. The animals' body temperatures were monitored; as soon as body temperature reaches 38 degrees C, the rats in group 2 were given allopurinol co-treatment, whereas, in group 3, vitamin E co-treatment was started at fever onset. Both kidneys were excised 6 weeks later, for the evaluation of histopathologic changes, apoptotic damage, and concentrations of transforming growth factor-beta (TGF-beta). Only minimal changes were found in control samples. Pathologic scores of inflammation and fibrosis in group 1 were higher than in the vitamin E and allopurinol groups (P < 0.05). Apoptosis index was also decreased in groups 2 and 3, compared to group 1 (P < 0.05). There was no significant difference in average TGF-beta levels between study groups. These findings suggest that administration of vitamin E or allopurinol following the onset of fever can reduce renal damage in pyelonephritis.

The presence of urinary nitrites is a significant predictor of pediatric urinary tract infection susceptibility to first- and third-generation cephalosporins

BACKGROUND

Previous studies in adults have refuted the use of nitrites as a predictor of bacterial resistance to both trimethoprim-sulfamethoxazole and cephalosporins. Some centers now consider first-line outpatient therapy with an oral third-generation cephalosporin appropriate for young children.

OBJECTIVE

The objective of this study was to determine if nitrite-negative pediatric urinary tract infections (UTIs) were more likely than nitrite-positive UTIs to be resistant to cephalosporins. This may enable physicians to adjust antimicrobial therapy before patients leave the Emergency Department (ED) to avoid the complications of ineffectively treated pediatric UTIs.

METHODS

A retrospective chart review examined, over a 9-month period, 173 pediatric patients who were diagnosed with a clinical UTI in the ED and who also had a positive urine culture and a recorded dipstick at the time of visit. The chi-squared test and Fisher's exact test were used to compare nitrite-negative vs. nitrite-positive UTIs for resistance to third-generation cephalosporins and other empiric antimicrobials.

RESULTS

For third-generation cephalosporins, 1.4% of nitrite-positive UTIs were resistant, whereas 14.4% of nitrite-negative UTIs were resistant (95% confidence interval [CI] -0.22 to -0.05). For first-generation cephalosporins, 8.4% were resistant in the nitrite-positive group, compared to 22.2% in the nitrite-negative group (95% CI -0.24 to -0.03).

CONCLUSION

The absence of urinary nitrites is a significant indicator for potential resistance to cephalosporins in pediatric UTIs. Due to low levels of pediatric UTI resistance, cephalosporins continue to represent useful empiric therapy in the general pediatric population. However, in high-risk patients, physicians may opt to alter their empiric choice of antibiotic based on the presence of urinary nitrites.

Caffeic acid phenethyl ester suppresses oxidative stress in Escherichia coli-induced pyelonephritis in rats

Although oxidative damage is known to be involved in inflammatory-mediated tissue destruction, modulation of oxygen free radical production represents a new approach to the treatment of inflammatory diseases. Caffeic acid phenethyl ester (CAPE), an active component of propolis from honeybee hives, has antioxidant, anti-inflammatory and antibacterial properties. For that reason, we aimed to investigate the efficiency of CAPE administration in preventing oxidative damage in pyelonephritis (PYN) caused by Escherichia coli. In this study, 35 Wistar rats were grouped as follows: control, PYN 24 h, PYN 48 h, PYN 72 h, CAPE 24 h, CAPE 48 h and CAPE 72 h. E. coli (1 x 10(9) c.f.u.) were inoculated into the rats in both PYN and CAPE groups via urethral catheterization. Ten microM/kg-body weight CAPE was injected to the rats in all CAPE groups 24 h before E. coli infection, and injections were repeated at 24-h intervals. Rats were sacrificed 24 h, 48 h and 72 h after infection in both PYN and CAPE groups. Malondialdehyde (MDA) and nitric oxide (NO) levels were significantly increased in kidneys of PYN groups. The activities of the antioxidant enzymes, catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and xanthine oxidase (XO) were also elevated by E. coli. However, CAPE administration reduced MDA and NO levels, as well as XO activity, although it increased SOD and GSH-Px activities. Histopathological examination showed that CAPE reduced the inflammation grade induced by E. coli. In conclusion, CAPE administrations decrease the oxidative damage occurring in PYN and therefore could be used for medical management of bacterial nephropathy.

Effect of a selective cyclooxygenase-2 inhibitor on renal scarring

BACKGROUND

Scarring is one of the steps of excessive wound healing, causing dysfunction of the involved tissues and clinically poor cosmetics. The aim of this study was to examine the effect of a highly selective cyclooxygenase-2 (COX-2) inhibitor on renal scar formation in experimental pyelonephritis.

MATERIALS AND METHODS

Four groups of 10 Balb/C mice were formed. In groups I and II following the inoculation of lipopolysaccharide (LPS) into both kidneys, 0.18 and 0.36 mg/day of rofecoxib was given respectively via intraperitoneal route for 5 days. No medication was applied following physiological saline solution injection to both kidneys of the mice in group III (negative control group). After group IV's LPS inoculation on the first day, saline solution (1 ml/day) was given intraperitoneally for 5 days (positive control group). Following the exposure of both kidneys, LPS of Escherichia coli (5 mg/kg) was injected into the kidneys of groups I, II, and IV. In group III, saline solution (0.1 ml) was used instead of LPS. Three days after the inoculation of LPS, solutions containing 0.18 and 0.36 mg of COX-2 inhibitor were given intraperitoneally for 5 days in groups I and II. No medication was used for the mice in group III. Six weeks after the inoculation of LPS and saline solution, all mice were humanely euthanized. Bilateral nephrectomies were done on each group of mice, and histopathological examination was performed.

RESULTS

Inoculation of LPS into the renal parenchyma caused pyelonephritis and scar formation in all groups. The degree of pyelonephritis and scar formation was lesser in groups in which COX-2 inhibitors were used. The degree of scar formation was lesser in group II, in which 0.36 mg more of COX-2 inhibitor was used than in group I (0.18 mg of COX-2 inhibitor).

CONCLUSION

In our study model, direct inoculation of LPS to kidneys caused experimentally induced pyelonephritis. Renal scar formation was effectively prevented through the utilization of rofecoxib at 0.36-mg doses.

Association between ICAM-1 Gly-Arg polymorphism and renal parenchymal scarring following childhood urinary tract infection

Renal parenchymal scarring (RPS) following urinary tract infection (UTI) is an important cause of renal morbidity in children. Studies have shown that the intensity of the inflammatory response following infection is related to the risk of RPS. However, genetic variability in this response has not been studied. Adhesion molecules play a crucial role in leucocyte recruitment following infection, and polymorphisms have been reported in the genes for key cell adhesion molecules. We have investigated the possibility that children who develop RPS following UTI may exhibit altered genotype or allele frequencies for polymorphisms of the intercellular adhesion molecule-1 (ICAM-1) (exons 4 and 6), E-selectin (exons 2 and 4), platelet endothelial cell adhesion molecule-1 (PECAM-1) (exon 3) and CD11b (3'UTR) genes, which may predict outcome of UTI. DNA was isolated from 99 children shown to have developed RPS, 43 children with no evidence of scarring (NS) following UTI and 170 healthy controls. Genotyping was performed by restriction fragment length polymorphism (RFLP) analysis. When the RPS group was compared with the NS group, there was a significant reduction in the frequency of the ICAM-1 exon 4 A allele (10.6 vs. 21.3%, respectively, chi2 = 6.01, P = 0.014). There was no significant difference in either allele or genotype frequency for any of the other polymorphisms studied. These data suggest that the A allele of the ICAM-1 exon 4 polymorphism may protect against the risk of RPS following UTI and may participate in the regulation of the inflammatory response following UTI.

Therapeutic effects of xanthine oxidase inhibitors: renaissance half a century after the discovery of allopurinol

The prototypical xanthine oxidase (XO) inhibitor allopurinol, has been the cornerstone of the clinical management of gout and conditions associated with hyperuricemia for several decades. More recent data indicate that XO also plays an important role in various forms of ischemic and other types of tissue and vascular injuries, inflammatory diseases, and chronic heart failure. Allopurinol and its active metabolite oxypurinol showed considerable promise in the treatment of these conditions both in experimental animals and in small-scale human clinical trials. Although some of the beneficial effects of these compounds may be unrelated to the inhibition of the XO, the encouraging findings rekindled significant interest in the development of additional, novel series of XO inhibitors for various therapeutic indications. Here we present a critical overview of the effects of XO inhibitors in various pathophysiological conditions and also review the various emerging therapeutic strategies offered by this approach.

Antibody responses and protection from pyelonephritis following vaccination with purified Escherichia coli PapDG protein

PURPOSE

A critical early step in the establishment of Escherichia coli pyelonephritis is bacterial attachment via the tip protein of P fimbriae. This adhesin, PapG, binds to glycolipid receptors present on vaginal and kidney epithelial surfaces. In this study we investigated the efficacy of vaccination with purified PapDG protein complex in preventing pyelonephritis caused by E. coli.

MATERIALS AND METHODS

Mature cynomolgus monkeys were intraperitoneally vaccinated with 100 microg purified PapDG protein. Following 3 identical boosters serum antibody titers to PapDG were measured by enzyme-linked immunosorbent assay. Vaccinated and unvaccinated animals were urethrally inoculated with 1 x 10 cfu of E. coli strain DS17, which was isolated from a child with acute pyelonephritis. The infection course was monitored by catheterized urine cultures, and by histological examination of the kidneys, bladder and kidney tissue culture 28 days after infection.

RESULTS

Intraperitoneal administration of purified PapDG vaccine resulted in the development of specific antibody responses in cynomolgus monkeys. In contrast to control monkeys, vaccinated monkeys did not show histological evidence of pyelonephritis after subsequent urethral challenge with pyelonephritogenic E. coli expressing P fimbriae.

CONCLUSIONS

Purified PapDG is a tractable vaccine candidate that in our small study demonstrated the ability to elicit adequate serum antibody levels to prevent E. coli mediated pyelonephritis.

Plasma and urinary soluble adhesion molecule expression is increased during first documented acute pyelonephritis

BACKGROUND

The degree of inflammatory reaction and leucocyte trafficking during acute pyelonephritis has been related to the risk of developing renal parenchymal scarring. Adhesion molecules play a central role in leucocyte recruitment during inflammation.

AIMS

(1) To determine whether circulating and urinary concentrations of E-selectin and intercellular adhesion molecule 1 (ICAM-1) were abnormal during first documented acute pyelonephritis; (2) to investigate whether circulating or urinary concentrations were predictive for the development of abnormalities on DMSA imaging.

METHODS

Plasma and urine samples were collected from 40 children with a first episode of acute pyelonephritis within one week of infection (acute sample) and at six weeks (late sample). Control samples were collected from 21 healthy age matched controls and 18 age matched controls with febrile illness not secondary to urinary tract infection.

RESULTS

Plasma and urinary sE-selectin were higher in acute samples (median 176.3 ng/ml and 0.12 ng/mmol respectively) compared with late (97.8 ng/ml and 0.029 ng/mmol) and both control (65.6 ng/ml and 0 ng/mmol) and febrile control (urine 0 ng/mmol) samples. Plasma sICAM-1 was higher in acute samples (428 ng/ml) than controls (365.2 ng/ml), and acute sICAM-1 urine concentrations were higher than febrile control concentrations (3.2 v 0.7 ng/mmol). No correlations were detected between sE-selectin or sICAM-1 and acute or late DMSA scan changes.

CONCLUSION

Plasma and urinary sE-selectin and sICAM-1 are significantly increased during acute pyelonephritis, though no correlation exists between the presence of high plasma or urine concentrations and DMSA scan changes, both during acute infection and six weeks post-infection.

Pathogenicity of Escherichia coli from dogs with UTI in relation to urovirulence factors

Six strains of Escherichia coli, isolated from urine of dogs with urinary tract infection (UTI), were examined to assess of urovirulence factors (UVFs) in the pathogenesis of UTI in an experimental pyelonephritis mouse model. From the results of ID50 and LD50, isolates having different UVFs in the same O serotypes varied in pathogenicity, and isolates having the same UVFs in different O serotypes had nearly the same pathogenicity. Histopathogenic examination revealed that the presence of pap, hly and cnfl contributed greatly to the development of upper UTI. It has also been suggested that hly and cnfl significantly related to the LD50 of the strain in the mouse model, confirming that UVFs are closely related to the pathogenicity of canine UTI.

UTI: diagnosis and evaluation in symptomatic pediatric patients

We retrospectively reviewed data on 260 hospitalized pediatric patients with symptomatic urinary tract infection (UTI). To ascertain the colony-forming units (CFU)/mL compatible with the diagnosis of UTI, a culture from a catheterized urine specimen containing >1,000 CFU/mL was considered diagnostic of UTI and resulted in imaging by renal ultrasound, voiding cystourethrography, and renal nuclear scan with Tc99m dimercaptosuccinic acid (DMSA). A positive DMSA renal scan is indicative of pyelonephritis. We used logistic regression analysis to determine which patient characteristics were predictive of pyelonephritis. We determined that, in hospitalized pediatric patients, the colony count of the positive urine culture, the type of organism grown in culture, and the voiding cystourethrography (VCUG) result (positive or negative for vesicoureteral reflux) did not predict which patients had pyelonephritis. In females, advancing age of the patient and positive renal ultrasound results were predictive of which patients had pyelonephritis when we controlled for other factors. We feel this emphasizes the importance of a thorough evaluation of hospitalized symptomatic patients, including patients with colony counts of 1,000 to 50,000 CFU/mL, to locate the level of infection and plan appropriate therapy.

Bacterial attachment to uro-epithelial cells: mechanisms and consequences

Microbial attachment to mucosal surfaces is a first step in mucosal infection. Specific interactions between microbial surface ligands and host receptors influence the distribution of microbes in their sites of infection. Adhesion has often been regarded as a sufficient end point, explaining tissue tropism and bacterial persistence at mucosal sites. Adherence, however, is also a virulence factor through which microbes gain access to host tissues, upset the integrity of the mucosal barrier, and cause disease. The induction of mucosal inflammation is one aspect of this process. Bacterial attachment to mucosal surfaces activates the production of pro-inflammatory cytokines that cause both local and systemic inflammation. Epithelial cells are one source of these cytokines. The binding of fimbrial lectins to epithelial cell receptors triggers transmembrane signaling events that upregulate cytokine-specific mRNA and increase cytokine secretion. P fimbriae that bind the globoseries of glycolipids cause the release of ceramides and activation of the ceramide signaling pathway which contributes to the IL-6 response. Spread of cytokines and other pro-inflammatory mediators from the local site contributes to the symptoms and signs of infection.

The possible role of granulocyte elastase in renal damage from acute pyelonephritis

During acute inflammatory processes, extracellular release of granulocyte elastase can contribute to subsequent tissue damage. To test our hypothesis that extracellular elastase release during acute pyelonephritis may contribute to subsequent renal parenchymal damage, we compared the intracellular and extracellular activities of the lysozyme elastase of human polymorphonuclear cells (PMN) when incubated in vitro with bacterial strains causing renal infection that led to either renal damage or no damage. Urine bacterial cultures were obtained from patients with acute pyelonephritis (flank pain, costovertebral angle tenderness, fever > 38 degrees C, bacteriuria, pyuria, and leukocytosis). Renal damage was demonstrated by cortical scarring on followup intravenous pyelography and/or diminished function on 131iodine hippuran renal scan. Mean extracellular elastase activity (mu units/PMN) was 0.15 for unstimulated PMN, 0.07 for PMN stimulated by bacteria not associated with renal damage, and 1.20 for the PMN stimulated by strains associated with renal damage. Mean intracellular elastase activity (mu units/PMN) was 3.73 for unstimulated PMN, 3.48 for PMN stimulated by bacteria not associated with renal damage, and 3.31 for the PMN stimulated by strains associated with renal damage. Extracellular granulocyte elastase activity was thus significantly higher (P = 0.0001) in PMN stimulated by bacterial strains associated with renal damage. Extracellular release of elastase may contribute to the pathogenesis of renal damage in pyelonephritis.

Cytokine and lymphocyte activation during experimental acute pyelonephritis

We studied the cellular and humoral events which follow experimental acute pyelonephritis from P-fimbriated Escherichia coli to gain insight into the relationships among cells and specifically cytokines to determine how early events in untreated infection lead to renal damage. Cynomolgus (Macaca fascicularis) monkeys were studied after they were subjected to unilateral ureteral bacterial inoculation. We evaluated the blood for leukocytosis and studied lymphocyte subsets using flow cytometry and monoclonal antibodies to the subsets and serum, complement, cytokines and antibody titers. Interleukin-1, 2 and 6 and tumor necrosis factor (TNF) were assayed by enzyme-linked immunoadsorbent assay (ELISA), using monoclonal and polyclonal antibodies. Leukocytosis was marked and there were significant elevations in serum cytokines, interleukin-1 alpha, 2 and 6 with only small changes in the level of TNF. Interleukin-2 levels were sustained and may have upregulated the homing receptor for virgin lymphocytes. The studies illustrated the unique relationship between cytokines and lymphocytes and the response to bacterial infection, showing that the inflammatory response is regulated not only by cytokine activity but also by lymphocyte activation.

Effect of prednisolone on ascending renal infection due to biofilm disease and lower urinary tract obstruction in rats

A model of renal infection due to lower urinary tract obstruction and biofilm disease was constructed for the study of renal scarring by inserting glass beads coated with bacterial biofilm into the bladder of rats and then clamping the urethra. We previously reported the effect of antimicrobial therapy used in combination with the anti-inflammatory agent prednisolone to prevent renal scarring. In this study we investigated the effect of prednisolone on renal scar formation using our new model. Renal scarring could not be prevented in the group in which prednisolone was administered in the period during which the urethra was regularly being clamped. In contrast, scarring was prevented in the group that began to receive prednisolone after the period of clamping had ended. Therefore, in cases of lower urinary tract obstruction prednisolone should only be administered for the prevention of renal scarring after the obstruction has been resolved.

The Gal(alpha 1-4)Gal-specific tip adhesin of Escherichia coli P-fimbriae is needed for pyelonephritis to occur in the normal urinary tract

Nonobstructive acute pyelonephritis in humans is most often caused by P-fimbriated Escherichia coli. P-fimbriae are heteropolymeric fibers carrying a Gal(alpha 1-4)Gal-specific PapG adhesin at its distal end. The pyelonephritic strain DS17 expresses P-fimbriae from a single gene cluster. A mutant strain, DS17-8, which expresses P-fimbriae tacking the PapG adhesin, was constructed by allelic replacement introducing a 1-bp deletion early in the papG gene. In cynomolgus monkeys, DS17 and DS17-8 were equally able to cause bladder infection, whereas only the wild-type strain DS17 could cause pyelonephritis as monitored by bacteriological, functional, and histopathological criteria. Since DS17, but not DS17-8, adheres to renal tissue, these data underscore the critical role of microbial adherence to host tissues in infectious disease and strongly suggest that the PapG tip adhesin of P-fimbriae is essential in the pathogenesis of human kidney infection.

Suppression of renal scarring by prednisolone combined with ciprofloxacin in ascending pyelonephritis in rats

To prevent renal scarring, which occurs at the end stage of chronic pyelonephritis due to vesicoureteral reflux of infected urine, immediate antimicrobial treatment is reported to be essential. When treatment is delayed, the antimicrobial agent is believed to be effective only in eliminating bacteria, not in preventing scar formation. Using the ascending pyelonephritis model in rats, we investigated the effect of immediate or delayed treatment with ciprofloxacin and that of delayed treatment with a combination of ciprofloxacin and prednisolone in preventing renal scarring following infection. An inoculum of 1 x 10(9) colony forming units (cfu)/0.1 ml. of the HM32 strain of Escherichia coli, which was isolated from a patient with a urinary tract infection, was injected directly into the rat bladder, and the urethra was clamped for 4 hours in each rat. Treatment by ciprofloxacin (15 mg./kg., twice a day for 5 days) alone or in combination with prednisolone (2 mg./kg., once a day for 4 days) was initiated 6 or 72 hours after bacterial inoculation. The kidneys of each rat were examined 6 weeks later. Immediate treatment by ciprofloxacin significantly inhibited renal scarring (no scarring was seen in any of the 8 rats), but delayed treatment had no effect on scarring (4 of 8 rats showed scarring) when compared with the untreated controls (7 of 8 rats showed scarring). However, the addition of prednisolone to the delayed treatment with ciprofloxacin significantly inhibited renal scarring (only 1 of 10 rats showed scarring) when compared with the untreated controls (7 of 8 rats showed scarring). These data suggest that prednisolone is effective in preventing renal scarring which occurs due to vesicoureteral reflux when the initiation of antimicrobial treatment is delayed.

Events leading to septic death from experimental acute pyelonephritis in the monkey

Experimental acute pyelonephritis in monkeys led to death in some of the animals following renal E. coli inoculation. It was found that both the inflammatory response and cytokine activation were much more severe in these monkeys as compared with others that survived. IL-1 was decreased just before death, and there were early increases in IL-2 and IL-6 serum concentrations, but no significant increase in TNF values. The data suggest that death in sepsis is due in part to excessive cytokine release because of a decrease in the protective activity of IL-1.

Protective anti-idiotype antibodies in the primate model of pyelonephritis

The adherence of P-fimbriated Escherichia coli to a receptor containing alpha-D-Gal-(1-4)-beta-D-Gal (Gal-Gal) on urothelial cells is an important pathogenic mechanism in the development of pyelonephritis. Antibodies (Ab1) that had been produced by immunization with Gal-Gal conjugated with bovine serum albumin were specifically purified and used to stimulate the production of anti-idiotypic antibodies (Ab2) in cynomolgus monkeys (Macaca fascicularis). While sera from all of the Ab2-producing monkeys contained antibodies reactive with Ab1 and P-fimbriae, not all of the sera inhibited P-fimbrial binding to the Gal-Gal receptor. On the basis of the inhibition of binding, Ab2-producing monkeys were divided into two groups, termed reactive and nonreactive. The reactive and nonreactive Ab2-producing monkeys, together with a group of control monkeys, were challenged with a renal inoculation with P-fimbriated Escherichia coli. Hematologic, immunologic, microbiologic, and pathologic data were compared among the three groups. The reactive monkeys, whose Ab2 in serum inhibited binding between P-fimbriae and the Gal-Gal receptor, were protected against renal damage compared with the control group. The nonreactive group shared some parameters with the reactive group but overall developed renal damage comparable to that of the controls.

Vesicoureteral reflux and pyelonephritis in the monkey: a review

P-fimbriated Escherichia coli, which cause nonobstructive pyelonephritis, adhere to a specific urothelial glycolipid receptor. In either the presence or absence of reflux (in the area of turbulent urine flow) these bacteria ascend the ureter and cause a decrease in ureteral motility. Endotoxin causes peristalsis to cease, leading to ureteral dilatation and change in papillary shape, thus allowing intrarenal reflux and adherence of the bacteria to renal tubules. Bacterial infection of a refluxing ureter may cause reflux to persist. Once the bacteria reach the kidney rapid effects occur at the cellular level with activation of complement followed by granulocytic aggregation and capillary obstruction, causing renal ischemia and damage during reperfusion. In addition, during phagocytosis the respiratory burst occurs, releasing toxic oxygen molecules, which leads to renal tubular death, invasion of the interstitium, microabscess and renal scar formation, that is chronic pyelonephritis, which equates with reflux nephropathy.

Renal scarring following reflux and nonreflux pyelonephritis in children: evaluation with 99mtechnetium-dimercaptosuccinic acid scintigraphy

99mTechnetium dimercaptosuccinic acid (DMSA) scintigraphy is the imaging modality of choice for the detection of acute pyelonephritis and chronic renal scarring in children. Using the DMSA scan we prospectively evaluated renal scarring after reflux and nonreflux pyelonephritis in children. The study population consisted of 33 patients with acute pyelonephritis documented by a DMSA renal scan at infection. The children were evaluated for renal scarring with a followup DMSA scan 4 to 42 months (mean 10.7 months) after the acute infection. All new scarring on followup DMSA scans occurred at sites corresponding exactly to areas of acute inflammation on the initial DMSA scan. Therefore, only those kidneys with acute changes on the initial scan were subsequently analyzed. Of 38 kidneys new or progressive scarring developed in 16 (42%), including 6 of 15 (40%) with associated vesicoureteral reflux and 10 of 23 (43%) without demonstrable reflux. New renal scarring developed in 6 of the 7 kidneys (86%) associated with a neuropathic bladder or posterior urethral valves. In contrast, new scarring developed in only 10 of 31 kidneys (32%) associated with a normal bladder (p = 0.028). Excluding the kidneys associated with a neuropathic bladder or posterior urethral valves, new renal scarring developed in 3 of 12 (25%) with primary reflux, compared with 7 of 19 (37%) without vesicoureteral reflux. Except for the white blood count and the species of infecting bacteria, no other statistically significant differences could be found between those cases in which scars did or did not develop. We conclude that acquired renal scarring only occurs at sites corresponding to previous areas of acute pyelonephritis, the acute parenchymal inflammatory changes of acute pyelonephritis are reversible and do not lead to new renal scarring in the majority of cases, and once acute pyelonephritis has occurred ultimate renal scarring is independent of the presence or absence of vesicoureteral reflux.

Etiology and pathophysiology of pyelonephritis

Escherichia coli is the most frequent cause of pyelonephritis. Its possible virulence factors include the ability to adhere and colonize the urinary tract, an important initiating factor in all urinary tract infections (UTIs). The importance of P fimbriae in this adhesion is stressed and the evidence for its importance in pyelonephritis is presented in epidemiologic studies of patients, as well as in animal studies. It appears that both host receptor density and the nonsecretor state is responsible for susceptibility to urinary tract infection. Vesicoureteral reflux can be responsible for ascending upper tract infection, but infection with P-fimbriated E coli may lead to ascending pyelonephritis without reflux because of the paralytic effect of lipid A on ureteral peristaltic activity. Renal ischemia leads to renal damage following infection by reperfusion damage due to the release of superoxide. Experimentally, this ischemic damage can be prevented by allopurinol, a xanthine oxidase inhibitor. The acute inflammatory response can produce renal damage because of the respiratory burst of phagocytosis, which while killing phagocytosed bacteria also damages renal tubules. An amelioration of the inflammatory response by treatment with superoxide dismutase or corticosteroids has been shown to modulate renal damage. Vaccination with P fimbriae has been shown experimentally to prevent the initiation of the disease. However, since vaccines are not clinically available, the clinical and animal studies on therapy of acute disease are stressed. Acute pyelonephritis during the first 3 years of life more often produced the renal damage that could lead to end-stage renal disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Norwich-Eaton lectureship. Pathogenesis of nonobstructive urinary tract infections in children

Most urinary tract infections occur without either obstruction or vesicoureteral reflux. Children become colonized by their mother's bacterial flora, that within the nursery or by siblings. Bacterial adherence may lead to colonization of the perineum in girls and of the prepuce in boys (if uncircumcised). Nephropathogenic bacteria ascend the urinary tract because of the P-fimbriae of Escherichia coli which adhere to a specific urothelial cell glycolipid. The endotoxin effect on ureteral peristalsis leads to intrarenal reflux, adherence in the kidney and acute pyelonephritis. Complement activation then causes granulocytic aggregation in capillaries with renal ischemia and activates granulocytes to produce the respiratory burst of phagocytosis, which releases superoxide into both phagosomes and the tubular lumen. Bacteria are thus killed as are renal tubules, leading to nephron loss. Untreated, the ischemia and respiratory burst lead to a loss of renal function and scar formation ending as chronic pyelonephritis (or reflux nephropathy).