What is Pyelonephritis?

Pyelonephritis is understood as an inflammatory process in which not only the renal pelvis and calyx are involved, but also the renal parenchyma with a predominant lesion of interstitial tissue. In most cases, the disease occurs in women under 40 years old, in some of them during pregnancy. In old age, men get sick more often than women. This is due to urinary stasis due to the development of prostate adenoma. Often pyelonephritis complicates the course of diabetes.
There are primary, or uncomplicated, pyelonephritis and secondary – complicated. Primary pyelonephritis is not preceded by any disturbances on the part of the kidneys and urinary tract; secondary pyelonephritis is based on organic or functional processes in the urinary tract that disrupt the dynamics of urine. Primary pyelonephritis is much less common than secondary.
The causative agents of pyelonephritis are most often Escherichia coli, enterococcus, Proteus, staphylococcus. In most cases, the urine flora is mixed, and in chronic pyelonephritis, mixed flora is much more common than in acute.
During treatment, the urine flora and its sensitivity to antibiotics change. Pyelonephritis is usually preceded and accompanied by bacteriuria. Bacteriuria is absent only with obstruction of the corresponding ureter or the formation of a turned-down abscess in the renal parenchyma.

Pathogenesis during Pyelonephritis

Essential in the occurrence and development of pyelonephritis is a violation of the state of the macroorganism, the weakening of its immunobiological reactivity. A decrease in the body’s resistance to infection as a result of overwork, previous diseases, hypovitaminosis, excessive cooling, circulatory disorders, chronic diseases, etc., as well as massive infection of the body, are very predisposing to pyelonephritis.
Disorders in the outflow of urine followed by urostasis (narrowing and kinks of the ureter, nephrotosis, anomalies of the urinary tract, pressure on the urinary tract from the outside) is one of the main factors predisposing to pyelonephritis.
Pyelonephritis is favored by diabetes mellitus, gout, nephrocalcinosis, potassium deficiency, analgesic abuse, extrarenal foci of inflammation (enteritis, frequent tonsillitis, pneumonia, suppuration), as well as inflammatory processes of the urogenital sphere (prostatitis, cystitis, adnexitis, and adnexitis). .
In the development of pyelonephritis, a major role is played by a violation of the venous and lymphatic outflows from the kidney, which contribute to the fixation of the infection in the latter.
Urokinematography managed to establish significant changes in the ureter urodynamics in the initial stages of pyelonephritis, when there are still no organic changes in the pyelocaliceal system. There are four ways of infection penetrating the kidney, pelvis and its calyxes: a) hematogenous, b) lymphogenous, c) along the ureter wall and d) along its lumen in the presence of vesicoureteral reflux.
Hematogenous pyelonephritis is a secondary focus of infection that has penetrated the kidney from a primary focus, often located in the urinary tract or organs of the reproductive system. If the infection is introduced into the kidney from a focus located away from the kidney and urinary tract, its causative agents are usually gram-positive cocci (in 90% of cases of staphylococcus).
With localization of the infection in the lower urinary tract, microorganisms can penetrate the kidney through the urinary tract. Of particular importance for the spread of infection are the pelvis-renal refluxes. With them, as a result of increased intrapulmonary pressure, microbes enter the venous or lymphatic vessels of the kidneys into the general bloodstream, and then return to the kidneys with a blood stream.
The appearance of acute pyelonephritis in pregnant women is facilitated by the expansion of the upper urinary tract, which occurs due to hormonal changes and compression of the ureters by the pregnant uterus.

Pathological anatomy of pyelonephritis

The initial stage of acute pyelonephritis is characterized by the presence of large edema of paranephral tissue. At this stage, apostematic nephritis or kidney carbuncle may occur. The inflammatory process in the perinephric tissue can be limited to leukocyte infiltration, but can progress and lead to its purulent fusion.
Even with prolonged pyelonephritis in the kidney, areas of purulent inflammation alternate with areas of sclerosis, and between them there may be islands of completely unchanged parenchyma.
Morphologically distinguish four stages of chronic pyelonephritis. In the first stage, the glomeruli are preserved, uniform atrophy of the collecting tubules and lymphocytic infiltration of the interstitial tissue are noted. In the second stage, some glomeruli are hyalinized, there is a pronounced atrophy of the tubules, a decrease in inflammatory infiltration and proliferation of connective tissue. In the third stage, death and hyalinization of many glomeruli are observed, the urinary tubules are lined with a low undifferentiated epithelium and filled with a colloidal mass. In the fourth stage, the cortical substance of the kidney sharply decreases, consisting in such patients mainly of poor connective tissue with nuclei with abundant lymphocytic infiltration.