Chronic pyelonephritis. A morphologic and bacteriologic study

Long-term urethral catheterization increases risk of chronic pyelonephritis and renal inflammation

OBJECTIVE

To determine the prevalences of chronic pyelonephritis and chronic renal inflammation in elderly nursing home patients at the time of death and to assess correlation with urethral catheterization and other putative risk factors.

DESIGN

Prospective assessment of risk factors with the prevalences of chronic pyelonephritis and renal inflammation at autopsy.

SETTING

A 240-bed long-term care facility.

PARTICIPANTS

All residents > or = 65 years old who died and were autopsied during a 2-year period.

MEASUREMENTS

Antemortem assessment of risk factors for renal inflammation, including a search for any urethral catheterization in the person's life. Prospective assessment of urethral catheterization, catheter obstruction, and use of anti-inflammatory medications and urine cultures. Urinary tract pathology was assessed for gross and microscopic evidence of inflammation and urinary tract stones.

RESULTS

The duration of catheterization was significantly associated with increasing prevalence of bacteriuria, polymicrobial bacteriuria, chronic pyelonephritis, and chronic renal inflammation. The prevalence of chronic pyelonephritis at death was 10 percent (5/52) for patients catheterized > 90 days during their last year of life and zero (0/65) when catheterized < or = 90 days (P < 0.02; Fisher's exact test). Chronic pyelonephritis was significantly associated with renal stones and hydronephrosis. The prevalence of chronic renal inflammation without chronic pyelonephritis was significantly greater than that of chronic pyelonephritis: the prevalence was 43 percent (20/47) when catheterized > 90 days and 18 percent (12/65) when < or = 90 days (P < 0.05). Chronic renal inflammation was associated with hydronephrosis, ureteral dilatation, acute pyelonephritis and diastolic hypertension.

CONCLUSION

Chronic pyelonephritis and chronic renal inflammation are associated with long-term catheterization.

Natural history of "lower" urinary tract infections

Our current knowledge of the long-term outcome of uncomplicated urinary tract infections in women is based on a re-evaluation of the criteria for defining pyelonephritis at autopsy, careful description of the causes of renal disease among patients entering dialysis and transplant programs, long term observation of patients, and epidemiologic studies which have attempted to determine the association of bacteriuria with mortality. The weight of the evidence favors the conclusion that although urinary tract infections can produce severe impairment of renal function, this is rare in the absence of a major predisposing factor such as obstruction, calculus, reflux, abnormalities of the voiding mechanism or diabetes. The predisposing lesions, however, may go undetected until heralded by episodes of acute pyelonephritis or by renal failure. Unfortunately, urinary tract infections are so common that it is difficult to distinguish the population at greatest risk. The possible role of renal damage produced by autoimmune mechanisms following infection needs continued study.

The role of urinary tract infection in chronic renal failure

The importance of bacterial infection as a major cause of progressive renal failure has become less prominent as long-term studies have failed to show progressive renal disease in bacteriuric humans. Functional or anatomic abnormalities of the urinary tract are necessary to perpetuate infection and cause renal scars and renal failure. In children, the most common abnormality is reflux. Sterile reflux that extends into the renal collecting ducts may cause scars previously called atrophic pyelonephritis. This entity is now referred to as reflux nephropathy. Other predisposing factors may lead to end-stage disease in a small proportion of bacteriuric patients. The most common are obstructive uropathy and calculus disease. Bacteriuria is difficult to eradicate in maintenance hemodialysis patients and may require bilateral nephrectomy. In transplant recipients, bacteriuria is common and has been associated with rejection and loss of allograft.

Bacteria and bacterial antigen in the kidney in human chronic renal disease. Bacteriological and immunofluorescence Studies

Kidneys obtained by nephrectomy from 85 patients with chronic nephropathy were examined by bacterial culture and by immunofluorescence for a content of E. coli antigen. A panel of 10 E. coli 0-antisera, representing the strains most commonly causing urinary tract infection, and antiserum against common enterobacterial antigen (CA), were used. Bacteria could be cultured from the nephrectomy specimens in 24 cases, mainly in cases of obstructive chronic pyelonephritis, analgesic nephropathy and congenital renal disease. By immunofluorescence, type-specific 0-antigen was found in whole bacteria and amorphously in macrophages, CA only in whole bacteria. Whole bacteria could be visualized in 12 cases, macrophages only in two cases. Amorphous bacterial antigen was no observed outside phagocytizing cells. On the basis of these results, it seems unlikely that progression of the renal lesions in chronic renal disease is due to persistant bacterial antigen in the absence of viable bacteria. Chronic pyelonephritis, defined as an interstitial nephritis due to the effects of bacterial infection in the renal parenchyma and pelvic mucosa, appears always to be a secondary manifestation following obstruction or primary renal disease, such as analgesic nephropathy or congenital renal disease.

Reflux as a cause of end stage kidney disease: report of 32 cases

Of 32 patients with end stage renal failure secondary to bilateral, primary, low pressure reflux 10 had sterile reflux and 22 had reflux associated with recurrent urinary tract infection. These cases clearly document a potential terminal phase in the natural history of reflux. In addition, the study indicates the absolute necessity of early diagnosis and surgical correction of severe reflux, regardless of whether the reflux is sterile or associated with infection, and before chemical evidence of renal functional impairment.

Acquiescent renal infection

The relationship between bacterial infection of the renal parenchyma with Escherichia coli and the establishment of pathologic lesions has been investigate experimentally. Infection was established in one kidney and the bacteriologic, pathologic and immunologic features of infection were compared in the pyelonephritic and contralateral unmanipulated kidney. Whereas active bacterial infection was associated with pathologic changes in the pyelonephritic kidney, a poor correlation was found between bacterial growth and the gross pathology and histopathologic changes in the contralateral kidney. The conclusion from these studies is that infection of the kidney is not always associated with pathologic changes. The term "acquiescent infection" has been used to describe this host-parasite relationship in which active, persistent, bacterial infection is not associated with pathologic lesions. Evidence is presented that bacteria in the contralateral unmanipulated kidney are present in the renal parenchyma and that bacterial proliferation can be induced following renal trauma. Activation of infection and bacterial proliferation did not always result in histopathologic damage to the kidney and was not associated with an increase in serum antibody.