Pyelonephritic Lesions Research Articles

Diffusion tensor imaging based multiparametric characterization of renal lesions in infants with urinary tract infections: an explorative study

BackgroundConventional diffusion weighted imaging (DWI) is a promising non-invasive tool in the evaluation of infants with symptomatic urinary tract infections (UTI). The use of multiparametric diffusion tensor imaging (DTI) provides further information on renal pathology by reflecting renal microstructure. However, its potential to characterize and distinguish between renal lesions, such as acute pyelonephritic lesions, permanent renal damages or dysplastic changes has not been shown. This study aimed to evaluate the potential of multiparametric DTI for characterization of renal lesions with purpose to distinguish acute pyelonephritis from other renal lesions in young infants with their first UTI.MethodsNine kidneys in seven infants, age 1.0–5.6 months, with renal lesions i.e. uptake reductions, on acute scintigraphy performed after their first UTI, were included. The DTI examinations were performed during free breathing without sedation. The signal in the lesions and in normal renal tissue was measured in the following images: b0, b700, apparent diffusion coefficient (ADC), and fractional anisotropy (FA). In addition, DTI tractographies were produced for visibility.ResultsThere was a difference between lesions and normal tissue in b700 signal (197 ± 52 and 164 ± 53, p = 0.011), ADC (1.22 ± 0.11 and 1.45 ± 0.15 mm2/s, p = 0.008), and FA (0.18 ± 0.03 and 0.30 ± 0.10, p = 0.008) for all nine kidneys. Six kidneys had focal lesions with increased b700 signal, decreased ADC and FA indicating acute inflammation. In three patients, the multiparametric characteristics of the lesions were diverging.ConclusionMultiparametric DTI has the potential to further characterize and distinguish acute pyelonephritis from other renal lesions in infants with symptomatic UTI.

Microvascular Doppler ultrasound in children with acute pyelonephritis

To compare the diagnostic performance of microvascular Doppler ultrasonography (MVUS) to B-mode and con-ventional colour Doppler US (CDUS) for detecting acute pyelonephritis (APN) lesions in children. An IRB-approved retrospective study was performed. From July 2018 to January 2019, 41 APN lesions in 28 children (15 boys, 13 girls; age range, 1-196 months; mean age, 53 months) who underwent 99mTc‒dimercaptosuccinic acid renal scintig-raphy (DMSA) or contrast-enhanced computed tomography (CECT) and US including B-mode, CDUS, and MVUS were enrolled in this study. Three paediatric radiologists independently reviewed the B-mode, CDUS and MVUS images for the DMSA or CECT-proven APN lesions and evaluated the lesion visibility, lesion distinguishability and diagnostic confidence between the MVUS and CDUS images. A total 41 of APN lesions were verified by DMSA (41 lesions) or CECT (3 lesions) during the same hospitalization period with renal US. Among 41 APN lesions, 52.8% was visible on B-mode, 85.4% on CDUS, and 94.3% on MVUS (p<0.001). Comparing the extent and margins of the lesions, MVUS had better results than CDUS in 41.5% of the lesions, CDUS had better results in 6.5% and they were equal in 52% (p<0.001). The diagnostic con-fidence of the APN lesions was higher for MVUS than CDUS in 36.6%, higher for CDUS than MVUS in 4.9%, and equal in the remaining 58.5% (p<0.05). The interobserver agreement was fair to moderate. MVUS showed improved detectability of hypoperfused areas in paediatric APN and provided higher diagnostic confidence.

Diffusion weighted imaging is a promising method to detect acute pyelonephritis in non-sedated free breathing infants

Urinary tract infection (UTI) is a common disease in infants. The initial evaluation includes imaging to identify risk factors for permanent renal damage, such as malformation and renal parenchymal involvement of the infection i.e. pyelonephritis. 99mTc-Dimercaptosuccinic acid (DMSA) scintigraphy is a well-established method for detection of pyelonephritis and renal damage, but has limitations in availability, spatial resolution, and detection of congenital malformations. Diffusion weighted magnetic resonance imaging (DWI) has been shown to have a high sensitivity for detection of pyelonephritis in children without the use of invasive procedures, contrast agents or ionizing radiation. How this method performs in young infants during non-sedated free breathing remains, however, to be investigated. To prospectively assess the feasibility and performance of DWI for detection of pyelonephritis in non-sedated free breathing infants. 32 children <6 months of age with first-time symptomatic UTI were examined with DWI and DMSA scintigraphy. The DWI examination was performed using a free breathing protocol without the use of sedation. Pyelonephritic lesions were registered for both methods by independent observers. Agreement between DWI and DMSA was evaluated. Consensus diagnosis was determined and compared to the DWI findings. The MRI and DMSA examinations were completed in 25 infants, with a median age of 1.7 (0.7-5.5) months. Focal uptake reductions were detected on the DMSA images in 12 (24%) of the 50 kidneys. The DWI method demonstrated a fair to good agreement with DMSA, k=0.50 (p<0.0001). The consensus diagnosis was pyelonephritis in eight (16%) of the 50 kidneys. DWI detected seven of the eight kidneys with pyelonephritis. No false positive findings were detected with DWI compared to consensus diagnosis. This study has shown an agreement between DWI and DMSA scintigraphy in the detection of pyelonephritis. Further validation of the performance of DWI, using a consensus diagnosis as a reference, confirmed the potential of the method. This feasibility study included a limited number of patients and the results need to be confirmed in a prospective study of a larger cohort. Free breathing DWI is a promising method for detection of pyelonephritic lesions in non-sedated infants.

Pyelonephritis: A Historical Reappraisal.

There is no human knowledge which cannot lose its scientific character when we forget the conditions under which it originated, the questions it answered and the function it was created to serve.[1][1] As with most diseases of the kidney, pyelonephritis is an old ailment, which as a diagnosis, is a

Cystographie isotopique indirecte couplée à la scintigraphie rénale corticale et détection des reflux vésicorénaux chez les nourrissons et les enfants atteints de pyélonéphrite

Vesico-uretero-renal reflux (VRR) and urinary tract infection are closely linked. Without any treatment, reflux nephropathy, hypertension and renal dysfunction are very often encountered. That is why a precocious and reliable diagnosis of RVR should be made. Our retrospective study included 33 infants and children suffering from acute pyelonephritis (APN). They were explored by both 99mTc-MAG3 indirect isotopic cystography (IIC), 99mTc-DMSA cortical renal scintigraphy performed on the same day, and radiological retrograde cystography (RRC). A VRR was expected on the same side than the pyelonephritic kidney. Results from IIC versus RRC and versus renal cortical acute pyelonephritis lesions, which were proved by the “gold standard” DMSA scan, were obtained. IIC detected a same-sided VRR in 52% and CRR in 33% of our patients. Some of them had bilateral lesions. IIC detected an homolateral VRR in 59% instead of 38% with RRC (P<0.05). IIC is a physiological noninvasive examination with a convenient sensitivity and dosimetry to search a VRR. Moreover, it gives in the same time interesting functional information on the kidneys and the urinary tract. Each of these characteristics can be favorably compared with RRC.

Host Response to Porcine Strains of Escherichia coli in a Novel Pyelonephritis Model

The initial pathology and pathogenesis of pyelonephritis and the influence of different strains of Escherichia coli were investigated in a novel porcine model. Nine female pigs were divided into three groups (A, B and C) and inoculated repeatedly into one renal pelvis with porcine pyelonephritis E. coli strain LK67 (P fimbriae PapG(I)), LK76 (type 1 fimbriae) or LK82 (type 1 fimbriae and P fimbriae PapG(II/III)), respectively. The contralateral kidneys were inoculated with saline and served as controls. Pigs were killed 6h post-inoculation (hpi). Differential leucocyte counts, serum biochemical analyses and measurement of serum concentrations of proinflammatory cytokines and acute phase proteins were carried out at 0, 3 and 6 hpi. Bacteriological evaluation of urine, kidneys, spleen, liver, abdominal swabs and blood samples and gross and histopathological evaluation of kidneys, renal lymph nodes, liver and spleen were performed by quantitative, semiquantitative and/or descriptive methods. Immunohistochemistry was used to identify cells expressing L1 antigen, CD3ɛ, CD4, CD8, CD79αcy and lysozyme, and to identify E. coli and Tamm-Horsfall protein (THP). E. coli was re-isolated from all inoculated kidneys. Gross and microscopical lesions of acute pyelonephritis were demonstrated in all but one kidney inoculated with E. coli, but in none of the control kidneys. Renal parenchymal infiltration with both neutrophils and mononuclear cells, primarily CD3+ T lymphocytes, was observed at 6 hpi. Most T lymphocytes were CD8+. Pigs in group C had the highest mean pathology scores. Neutrophils were the dominant renal leucocyte in this group, while the number of mononuclear cells was at least equal to the number of neutrophils in the lesions of pigs from groups A and B. Kidneys with a high number of E. coli had severe lesions. Systemic spread of E. coli was observed in five pigs. THP was observed interstitially in 89% of the E. coli-inoculated kidneys. In all groups, increased numbers of neutrophils and decreased numbers of lymphocytes and monocytes were shown by differential leucocyte count at 6 hpi, and from 3 to 6 hpi there was a significant increase in C-reactive protein concentration.

Comparison of MRI and renal cortical scintigraphy findings in childhood acute pyelonephritis: preliminary experience

Objective: The diagnosis of acute pyelonephritis in children remains a clinical challenge. It may cause permanent renal scar formation and results in the chronic renal failure if prompt diagnosis and treatment are delayed. The purpose of this study is to compare magnetic resonance imaging (MRI) and renal cortical scintigraphy (RCS) findings in childhood acute pyelonephritis and to determine pyelonephritic foci in the acute phase. Materials and method: Twenty children (15 females and five males) with symptoms dysuria, enuresis, costovertebral pain, fever of 37.5 °C or more and/or positive urine culture were imaged by unenhanced turbo spin echo T2, spin echo T1-weighted, pre- and post-gadolinium inversion recovery MRI and RCS. Both imaging techniques were read independently by two radiologists and nuclear medicine specialists. Sensitivity and specificity of MRI in detecting acute pyelonephritic foci and scar lesions were calculated. Furthermore, in order to calculate the reliability of MRI over RCS in differentiating scar tissue and acute pyelonephritic foci, follow-up MRI studies were done in six patients after treatment of acute pyelonephritis. Results: Sensitivity and specificity of MRI in the detection of pyelonephritic lesions were found to be 90.9 and 88.8%, respectively. There is no statistically significant difference in lesion detection between the two diagnostic modalities ( P>0.05). Conclusion: Post-gadolinium MR images show significant correlation with RCS in the determination of renal pathology. Moreover, the ability of discriminating acute pyelonephritic foci and renal scar in early stages of disease is the superiority of MRI.

ADJUNCTIVE ORAL CORTICOSTEROIDS REDUCE RENAL SCARRING: THE PIGLET MODEL OF REFLUX AND ACUTE EXPERIMENTAL PYELONEPHRITIS

Purpose We investigate the efficacy of antibiotics combined with corticosteroid in diminishing post-pyelonephritic renal scarring compared to standard antibiotic therapy. Materials and Methods Bilateral vesicoureteral reflux was surgically created in 36 piglets (72 kidneys). A week later each bladder was inoculated by percutaneous injection with a standardized broth culture of Escherichia coli and molten paraffin. 99m Technetium dimercapto-succinic acid (DMSA) scintigraphy was performed 3 days after introduction of urinary infection to detect the presence of acute pyelonephritis. Acute pyelonephritic lesions seen on DMSA scans were graded according to the percentage of renal zone involvement as grade 1-less than 33%, grade 2-33 to 66% and grade 3-greater than 66% involved. When pyelonephritis was present, piglets were randomized to receive either standard antibiotics or antibiotics and 2 mg./kg. prednisolone daily. 99m Technetium-DMSA scintigraphy was repeated 2 months after completion of therapy, and the kidneys were harvested for gross and histopathological examination. Each kidney was divided into upper, middle and lower zones for correlation of pathological and imaging findings. Severity of renal scarring was then assessed using histopathological confirmation of gross anatomical findings as grade 1-less than 1, grade 2-1 to 2 and grade 3-greater than 2 cm. Results Acute pyelonephritis was induced in 136 of 216 renal zones. The sites of renal scarring corresponded anatomically to sites of acute pyelonephritis in all but 5 cases. Overall, the prevalence of post-pyelonephritic scarring was 56.6% (77 of 136) of renal zones. The severity of scarring in both groups correlated with the severity of the initial pyelonephritic lesion. Of the 31 zones that formed grade 3 renal scars the distribution of grades 1, 2 and 3 acute pyelonephritis on the initial DMSA scan was 3, 26 and 71%, respectively. Grade 3 acute pyelonephritis was more likely to result in severe (grade 3) renal scars in the control compared to the steroid treated group (59 versus 31%). Overall, acute pyelonephritis completely resolved in 40% of controls and 51% of steroid treated animals. However, only 9% of control animals with grade 3 acute pyelonephritis demonstrated complete resolution, as opposed to 28% of those receiving steroids. Conclusions The risk of renal scarring is greatest after severe acute pyelonephritis involving greater than 66% of a renal zone. Adjunctive oral prednisolone appears to be effective in diminishing renal scarring in severely affected kidneys. In kidneys with mild and moderate acute pyelonephritis antibiotics alone appear to be equally effective in preventing scarring.

EXPRESSION OF INTERCELLULAR ADHESION MOLECULE-1 IN MICE WITH PSEUDOMONAS-INDUCED PYELONEPHRITIS

Purpose To investigate the role of intercellular adhesion molecule-1 (ICAM-1) in the renal inflammatory process, we studied the time-course fluctuation of ICAM-1 expression on inflammatory lesions in mice with experimentally induced bacterial pyelonephritis and the effect of in vivo administration of an anti-ICAM-1 monoclonal antibody (mAb) on leukocytic migration. Materials and Methods Ascending pyelonephritis was induced by transurethral instillation of Pseudomonas aeruginosa, and the expression of ICAM-1 in the pyelonephritic lesions was studied by immunohistochemical methods. Results The expression of ICAM-1 on the pyelonephritic lesions closely paralleled the degree of infiltration of neutrophils and macrophages until 3 days after infection. At 7 days after infection, though the degree of infiltration of these cells was quite high, expression of ICAM-1 was reduced. Treatment with the anti-ICAM-1 mAb in mice with bacterial pyelonephritis resulted in suppression of influx of neutrophils and macrophages in the infected sites until 3 days after infection. However, at 7 days after infection inhibition of the influx of these cells was not seen. Conclusions These results suggest that ICAM-1 expression is transient and plays a key role in the influx of neutrophils and macrophages associated with the early-phase response, and that in the late phase ICAM-1 independent adhesion molecules may be more predominant.

Tc-99m Dimercaptosuccinic AcidDMSA Renal Scintigraphy in Patients with Acute Pyelonephritis

ObjectivesRecently, several authors reported that Tc-99m DMSA renal scan frequently showed cortical defects of the involved kidneys even in the patients with acute pyelonephritis who did not show abnormal findings in the ultrasonography and intravenous pyelography IVP).MethodsIn order to evaluate the utilities of Tc-99m DMSA renal scan and the clinical meanig of cortical defects in the Tc-99m DMSA renal scan of the patients with acute pyelonephritis, ninety two patients with acute pyelonephritis, from March 1991 to February 1994 in Chungnam National University Hospital(CNUH), were included in this study. Patients were subdivided as Group A:Patients showing normal Tc-99m DMSA renal scan(n=42) and Group B:Patients with definit cortical defects on the Tc-99m DMSA renal scan(n=50). We compared clinical characteristics such as age and sex, recurrency, duration of fever, bacterial culture study, incidence of renal insufficiency and the results of renal ultrasonography and intravenous pyelography between the two groups.ResultsFifty four percents of 92 patients with acute pyelonephritis showed a significantly longer febrile period after admission, higher positive rates on the urine and blood culture studies and higher incidence of renal insufficiency than those of the Group A patients. Sixty nine percents of Group B patients showed normal results in ultrasonography or IVP study.ConclusionsTc-99m DMSA renal scan was a more sensitive imaging test than ultrasonography in kidneys and IVP to detect pyelonephritis lesions and may be useful to predict the patient group with a severe disease course. These patients may need more careful management and further studies to evaluate the possibility of complications.

Renal Pathology and the 99mTc-DMSA Image During the Evolution of the Early Pyelonephritic Scar: An Experimental Study

This study describes the pathologic changes underlying the appearances of the 99mTc-DMSA renal image during acute pyelonephritis induced in piglets by a combination of vesicoureteral reflux (VUR) and urinary infection.In a total of 42 animals examined, pathologic lesions were identified in 36 of the 46 kidneys subjected to VUR and urinary infection, but no lesions developed in the remaining 10 refluxing kidneys. While scintigraphic defects were invariably associated with pyelonephritic lesions (specificity 100%), some small lesions were not identified (sensitivity 80%).There was a significant association (p = <0.001) between the degree of photon deficiency seen scintigraphically and the histologic changes (early and late lesions). However, the scintigraphic appearance of individual lesions was also influenced by factors such as their extent and density, so that consideration of the macroscopic characteristics was also important for precise correlation.

Renal imaging with 99Tcm-labelled DMSA in the detection of acute pyelonephritis

Serial renal 99Tcm-labelled dimercaptosuccinic acid (DMSA) scintigrams were acquired 2-58 days after the introduction of urinary tract infection in 33 pigs with experimentally induced vesicoureteric reflux (VUR). In 29 animals VUR was unilateral and in four bilateral, a total of 37 refluxing systems. Animals were killed either at varying intervals after a scintigraphic defect was noted (24 refluxing kidneys) or after a period when sequential scintigrams were normal (13 refluxing kidneys). The appearance of the scintigram acquired on the day prior to death was compared with the renal pathology, each kidney and renal image being divided into three zones (upper, middle, lower) for separate consideration. Of the 37 refluxing systems pyelonephritic lesions were seen in 27, in a total of 61 zones. In the remaining ten kidneys no scintigraphic defect was detected and no pathological lesions were identified either macroscopically or microscopically. Where an abnormality was detected on the scintigram a lesion was always identified in the kidney (sensitivity 100%). Small pyelonephritic lesions in a total of 12 zones in six kidneys were not detected on the scintigram (specificity 82%). Of the lesions undetected by scintigraphy only one occurred in the upper pole.

Escherichia coli-specific T lymphocytes in experimental pyelonephritis.

We have assessed the phenotype and specificity of infiltrating mononuclear cells in a model of unilateral ascending acute pyelonephritis induced in rats with nephritogenic Escherichia coli or Pseudomonas aeruginosa. Histologic examination showed a predominance of mononuclear cells in the interstitium at all periods examined (4, 8, 15, 21, and 25 days), although at 4 and 8 days neutrophils were also abundant. Most of the mononuclear cells had the morphologic appearance of large lymphocytes. Immunoperoxidase studies with mAb showed that most of the mononuclear cells were W3/25+; many were W3/13+ and a small proportion were OX8+. Many of the mononuclear cells were Ia+. T cells were propagated in IL-2-containing media from small fragments of renal tissue with pyelonephritic lesions. Most of the propagated cells were W3/25+; fewer than (10%) were OX8+ or Ia+. T cells propagated from kidneys infected with E. coli responded, in proliferation assays, to the infecting strain or other E. coli strains, but not to P. aeruginosa or enterococci. The response to non-p-pilus-bearing E. coli was as great or greater than to E. coli with adhesins. T cells derived from lesions induced by P. aeruginosa responded to the infecting organisms, but not to E. coli. The response to the infecting organism (E. coli or P. aeruginosa) was MHC restricted, as indicated by the requirement for syngeneic APC. The results show that large numbers of T lymphocytes, especially with the "helper/inducer" phenotype, accumulate in the lesions of acute pyelonephritis in rats. Among the infiltrating T lymphocytes are activated cells and cells with specific reactivity to the infecting bacteria (or related strains). The findings indicate that T lymphocytes play a role within the kidney in response to the invading bacteria.

Evaluation of 99Mtechnetium-Dimercapto-Succinic Acid Renal Scans in Experimental Acute Pyelonephritis in Piglets

We evaluated the sensitivity and specificity of 99mtechnetium-dimercapto-succinic acid renal scans in the detection and localization of experimental acute pyelonephritis in piglets. To create pyelonephritis vesicoureteral reflux of infected urine was surgically induced in 22 piglets. Nine animals were evaluated with a dimercapto-succinic acid renal scan at 1 week and 13 at 2 weeks. Autopsy and histopathological examination of the kidneys were performed subsequently.The location and extent of the inflammatory response found on histopathological examination were compared to dimercapto - succinic acid renal scan findings in a blinded fashion. Of the 22 kidneys subjected to vesicoureteral reflux 15 had positive histopathological findings of acute pyelonephritis, including 13 detected by the dimercapto - succinic acid renal scan findings. The 2 kidneys in which inflammation was not detected had only minimal grade I lesions and were grossly normal. There were no false positive scans in any of these kidneys. The sensitivity of the scan for detection of acute pyelonephritis in the kidneys subjected to reflux was 87 per cent and the specificity was 100 per cent. Furthermore, in these same kidneys the dimercapto-succinic acid renal scan findings correctly predicted the presence or absence of individual pyelonephritic lesions in 62 of 66 poles for an over-all agreement rate of 94 per cent. Thus, dimercapto - succinic acid renal cortical imaging is a highly sensitive and reliable imaging modality to detect and localize experimental acute pyelonephritis in piglets. (J. Urol, part 2, 140:1169-1174, 1988)

Inhibition of neutrophil myeloperoxidase activity by selected tissues

Myeloperoxidase, a polymorphonuclear leukocyte-specific enzyme, has been used previously to quantify the number of polymorphonuclear leukocytes in tissue. When this method was employed in an attempt to measure polymorphonuclear leukocyte numbers in infected kidneys, it was found that myeloperoxidase could not be demonstrated, although significant numbers of neutrophils were present in the pyelonephritic lesions. Further studies were carried out to determine the effect of other tissues on free and cell-bound exogenous myeloperoxidase. We have shown that while skin had little effect on enzyme levels, liver and spleen totally destroyed myeloperoxidase activity within 30 sec. Cardiac and striated muscle had an intermediate effect. When intact neutrophils were added to fresh cardiac tissue 72.5% myeloperoxidase activity was destroyed during the enzyme solubilization procedure. These findings indicate that the technique can only be used for the quantification of polymorphonuclear leukocytes in selected tissues and that appropriate controls are essential. Previous studies in which myeloperoxidase levels have been used to estimate polymorphonuclear leukocyte numbers in cardiac tissue will need reevaluation.

Local cellular immune response in ascending urinary tract infection: occurrence of T-cells, immunoglobulin-producing cells, and Ia-expressing cells in rat urinary tract tissue.

The local immune response was studied in rats with ascending urinary tract infection that was induced by Escherichia coli 06K13H1 . The occurrence in urinary tract tissue of cells reacting with monoclonal antibodies to T-cell markers and Ia antigen and with antibodies to immunoglobulin G (IgG), IgM, and IgA was studied by immunohistochemical methods. Serum antibody response and antibody coating of bacteria in the urine were also followed. Infection increased the number of irregular Ia-expressing cells in both bladder submucosa and the intertubular space in the kidney. The epithelial cells of some tubules were induced to express Ia antigens. A slight increase of what were most probably T-"helper" cells in the bladder was noted during the initial phase of infection. These cells soon disappeared, and there was instead an increase in irregular W3/25-reactive cells that may be identical to the observed Ia-positive cells. In the pyelonephritic lesions there were large amounts of T-cells, mainly T-helper cells, Ia-expressing cells, both rounded and irregular, and also IgG-and IgM-producing cells. IgA-producing cells were demonstrated in the infected bladders. The results indicate that distinct differences exist between the immune reactions in bladder and kidney tissue which may be important for the development of infections in these organs.

Experimental renal infection: Acute and chronic studies of histology and function

Experimental renal infections have resulted in histologic lesions of acute and chronic pyelonephritis, but in most studies the urinary tract has been "traumatized" to induce persistent infection. Sequential functional alterations have been measured infrequently. The present studies were designed to separate the functional and histological changes caused by high pressure sterile reflux from reflux with pathogenic organisms. Reproducible disruption of the pelvic epithelium with extravasation of solution into the parenchyma and vasculature occurred with reflux of 2.0 ml of solution but not with 1.0 ml. Reflux with 2.0 ml of sterile broth failed to cause permanent histologic changes, but reflux with broth containing organisms resulted in minor inflammatory changes. There was no decrease in renal function in either group. In long-term studies, no histologic changes in the cortex or medulla were noted 21 weeks after reflux of 1.0 ml of broth containing organisms; however, there was failure of functional maturation in the infected animals commensurate with their growth, as compared to the shams and controls (P = 0.03). Sterile reflux did not cause cortical scars or changes in renal function, but persistent parenchymal infection was associated with arrest of functional growth.

Experimental Rat model for Corynebacterium renale-induced pyelonephritis.

The laboratory rat was able to serve as a model for ascending pyelonephritis after implantation of a zinc disk coated with Corynebacterium renale into the urinary bladder because it satisfied three different criteria for infection. The production of an alkaline urine and the presence of significant numbers of C. renale in the kidneys, as well as distinct pyelonephritic lesions as revealed by histological examination, were observed in all rats infected with C. renale. Control rats that harbored sterile disks in their urinary bladders exhibited none of the above effects.

Influence of acetohydroxamic acid on experimental Corynebacterium renale pyelonephritis.

The role of Corynebacterium renale urease in the establishment of pyelonephritis was studied by the oral administration of acetohydroxamic acid (AHA), a urease inhibitor, to experimentally infected rats. The bacteria were introduced by surgical insertion of a zinc disc containing 1 X 10(6) colony-forming units of C-renale into the urinary bladder whereas sterile discs were implanted in the bladders of the control animals. Daily administration of AHA via the drinking water did not halt the development of pyelonephritis. Larger doses, given by gavage, did accomplish this goal; that is, the pH of the urine was lowered, the number of colony-forming units of C. renale in the kidney was reduced drastically, and pyelonephritic lesions were observed in the kidney by light-microscopic examination. All experimental rats developed cystitis in varying degrees of severity. About 70% of the intact AHA given by gavage was excreted in the urine 24 h after administration of this compound. Rats implanted with a urease-negative mutant of C. renale displayed no signs of pyelonephritis but did develop cystitis.

Pyelonephritis in the dog

A survey of 178 dogs in Britain with nephritis revealed an incidence of 8 per cent. of pyelonephritis. Four out of 14 (28·6 per cent.) of these were associated with partial or complete obstruction of the urinary tract. Histopathological studies suggest a haematogenous mode of spread of the infection. Escherichia coli appears to play an important part in the pathogenesis of the lesions while obstruction or stasis predisposes the kidney to infection. The lesions of pyelonephritis in the dog are similar to those in man.