Chronic pyelonephritis

Chronic pyelonephritis is that variety of chronic interstitial nephritis resulting from bacterial infection of the kidney. But unlike urinary tract infections, for which simple diagnostic criteria are available, the diagno­sis of chronic pyelonephritis is reached only after careful consideration of various nonpathognomonic clinical and pathologic findings data, are dif­ficult to obtain and are too often available for only a fraction of the patients illness. As a consequence there are no reliable data concerning the prevalence of chronic nonobstructive pyelonephiritis.

Urinary obstruction is a common accompaniment of chronic pyelo­nephritis but in a large proportion of cases obstruction cannot be demon­strated anatomically. Most patients with renal lesions which fulfill crite­ria for chronic pyelonephritis at autopsy have sterile kidney cultures and were not known to have had clinical episodes of bacterial urinary infec­tion. These observations have stimulated investigations into factors other than obstruction which make the kidney susceptible to infection and into other injuries which may result in morphologic changes in the kidney resembling those produced by bacterial infection.

Many patients with chronic pyelonephritis develop hypertension at some time in the course of their illness. It has been suggested that this is related to the contraction of scar tissue and to endarteritis obliterans with focal renal ischemia, rather than to diffuse renal damage. Occa­sionally, the blood pressure may become elevated long before there is mea­surable impairment of renal function, and only a persistently positive urine culture or characteristic changes in the intravenous pyelogram may distinguish the clinical picture from that of "essential" or "malignant" hypertension.

In general, glomerular filtration and renal blood flow decline togeth­er and proportionally as the disease progresses. As might be expected, there is usually more disparity between the function of the right and left kidneys than is generally the case in diffuse diseases of the" kidney such as glomerulonephritis or nephrosclerosis. Maximum concentraing ability tends to become impaired earlier in the course of the disease than in pa­tients with chronic glomerulonephritis. Occasional patients with advanced azotemia may excrete a urine hypotonic to plasma, even when they are dehydrated. Many patients are unable to conserve sodium on a lowsalt diet, even when only mild azotemia is present. Polyuria and nocturia are prominent in such cases. Hyperchloremic acidosis as a result of impaired renal excretion of acid and reabsorption of bicarbonate is more often a feature of chronic pyelonephritis than of glomerulonephritis. Proteinuria is usually less than 2 g (rarely as much as 4 to 6 g) daily, except when congestive heart failure supervenes.

When pyelonephritis is not accompanied by hypertension, the course may be prolonged and compatible with comfortable and useful life even after considerable encroachment upon renal function in perhaps no other disease of the kidneys can fluctuations in renal function be so marked or so frequent. During acute infections or episodes of dehydration, renal decompensation may progress to the stage of advanced uremia; yet the patient may be able to recover and carry on with adequate though impaired renal function for years. Nonspecific complaints of fatigue, anorexia, and weakness often remit remarkably when the urine is steril­ized by an appropriate course of antibiotics and when acidosis, dehydra­tion, and salt depletion are adequately treated.

The problem of recurrent infections, sometimes with resistant bacte­ria, is important and unsolved. An effort should be made to treat urinary tract obstruction and to improve bladder emptying, when residual urine is present. Reducing the bacterial population of bladder urine by the pro­longed administration of urinary antiseptics may offer some hope for halting the indolent progression of the disease.

Even when one kidney appears small and the other normal in size, pyelonephritis is in most instances bilateral. Nephrectomy which is under­taken in the hope of eradicating infection is generally doomed to failure. This general view of the frequency of asymptomatic destruction of the kidney in pyelonephritis may be incorrect, since some of the patients may have had some other form of chronic interstitial nephritis; rather than pyelonephritis. Proper understanding of the problem requires continued careful study with clear recognition of the possible error of traditional concepts.

Дата добавления: 2015-11-14