Pyelonephritis: an overview of information

Pyelonephritis is a nonspecific infectious-inflammatory disease of the kidney.

The term is commonly used to describe an infectious process in which kidneys and related structures are involved. Infection can be ascending and involve both the renal pelvis, and the kidney or metastatic and confine itself to the renal parenchyma. When the infection spreads into the underlying tissues, a perinephalic abscess or paranus is formed.

ICD-10 codes

• N10. Acute tubulointerstitial nephritis.
• N11. Chronic tubulointerstitial nephritis.
• N13.6. Pionerophosis.
• N15.1. Abscess of the kidney and pericardial tissue.

The following are the nosological forms for ICD-10 that are not associated with infection:

• N11.0. Non-structured chronic pyelonephritis associated with reflux.
• N11.1. Chronic obstructive pyelonephritis.

Pyelonephritis includes one or more of the following conditions:

• acute or chronically active infection;
• residual lesions and scars of past infection;
• local immune inflammatory response to infection;
• a combination of all these processes.

Epidemiology of pyelonephritis

  Pyelonephritis is a common disease. However, there are no reliable population epidemiological studies describing the frequency of pyelonephritis. Even for groups such as those with diabetes mellitus, who have a high risk of developing the disease with the most severe course, there is no statistically reliable data.

In children, pyelonephritis ranks second after respiratory diseases. In women of young, middle age and girls, acute uncomplicated pyelonephritis occurs 5 times more often than in men and boys.  

Despite the high incidence of the disease in women, the course of uncomplicated non-obstructive pyelonephritis is favorable. Pyelonephritis is detected in 8-20% of autopsies, and equally in men and women. However, there is no evidence that he had an infectious disease.

The higher incidence of ascending urinary tract infections and pyelonephritis in girls and women is due to anatomical and physiological characteristics:

• short and wide urethra;
• the proximity of natural reservoirs of infection (vestibule vestibule, rectum);
• frequent accompanying inflammatory gynecological diseases;
• often occurring right-sided nephroptosis, with violation of urodynamics of the upper urinary tract and blood supply to the kidney;
• violation of urodynamics of the upper urinary tract, compression of the lower third of the ureters by an enlarged uterus during pregnancy;
• atrophy of the urinary tract mucosa in postmenopause.

During pregnancy, acute pyelonephritis is observed in 3-11% of women.

[1], [2], [3], [4], [5], [6], [7], [8]

What causes pyelonephritis?

Infectious pyelonephritis is primarily caused by gram-negative or gram-positive bacteria, usually causing a urinary tract infection (bacterial pyelonephritis). Other possible pathogens of pyelonephritis can be Mycobacterium tuberculosis (kidney tuberculosis), yeast fungi (candidiasis pyelonephritis), other fungi and viruses. Patients with acute uncomplicated pyelonephritis rarely have arterial hypertension or recurrent renal damage. Patients with a complicated infection are more likely to develop sepsis and severe kidney damage. A high risk of severe kidney infection also exists in patients with obstruction and neurogenic abnormalities of the urinary tract, diabetes mellitus, polycystic kidney disease, stones and urinary catheters. Infection caused by urease-producing microorganisms leads to the formation of infectious (struvite) stones.

In patients with diabetes, the risk of developing destructive (purulent) forms of the disease: apostematous and emphysematous pyelonephritis, carbuncle and kidney abscess, papillary necrosis. In patients with a long-persistent, complicated infection, a rare condition, known as xanthogranulomatous pyelonephritis, may occur. In the past, pyelonephritis was considered one of the frequent causes of hypertension and severe kidney disease. At present, it is known that with reflux-nephropathy, there is much more damage to the kidneys, which was previously attributed to chronic pyelonephritis. Many diseases can mimic bacterial pyelonephritis, for example analgesic nephropathy, interstitial nephritis, vascular kidney disease.

What causes pyelonephritis?

Classification of pyelonephritis

There are many classifications of infections of the urinary tract and urogenital organs. At the same time, the classification of acute pyelonephritis, adopted in Russia, distinguishes only the stages of acute infectious inflammatory process in the interstitium and in the parenchyma of the kidney (serous, purulent), but not the topical forms of damage to the kidney or renal pelvis itself, and the lesion of the pelvis is not reflected in these classifications, which contradicts the very notion of "pyelonephritis".

Classification of pyelonephritis according to S. Kunin (1997):

• acute complicated bacterial pyelonephritis (focal or diffuse);
• lobar nephronia;
• chronic complicated bacterial pyelonephritis;
• pioneophosis;
• emphysematous pyelonephritis:
• papillary necrosis of the kidneys;
• xanthogranulomatous pyelonephritis;
• malacoplakia;
• pyelonephritis Tape (infection, localized in the upper urinary tract);
• kidney abscess and perinephric abscess;
• an infection superimposed on polycystic kidney disease;
• kidney infection caused by less common microorganisms;
• kidney tuberculosis and other mycobacterial infections;
• fungal infections;
• viral infections.

Classification of infections of the urinary tract and urogenital organs according to the Guidelines of the European Urological Association (2006):

• uncomplicated lower urinary tract infections (cystitis);
• uncomplicated pyelonephritis;
• complicated urinary tract infection with and without pyelonephritis;
• urosepsis;
• urethritis;
• Special forms: prostatitis, epididymitis and orchitis.

With the flow, uncomplicated (primary) and complicated (secondary, recurrent) urinary tract infections are distinguished. The term "chronic" for urinary tract infections, as a rule, does not apply, as in most cases it incorrectly reflects the course of the disease. As a rule, chronic pyelonephritis develops after a bacterial infection that appeared against the background of anatomical abnormalities of the urinary tract (obstruction, vesicoureteral reflux), infected stones. It is believed that up to 60% of human infections are associated with a biofilm-infection. By biofilm infection refers to the adhesion of microorganisms to the surface of mucous membranes, stones or biomaterials (catheters, drains, artificial prostheses, sphincters, nets, etc.). Microorganisms at the same time begin to live and multiply on them, periodically developing aggression against the host - the macroorganism.

Uncomplicated infections are more common for young women, for complicated (secondary) infections there is no such difference. Complications of infections occur against the background of functional disorders or anatomical abnormalities of the urinary tract, after catheterization of the bladder or kidney of the kidney and interventions on the urinary tract, against a background of severe co-morbidities: diabetes, urolithiasis, chronic renal failure, etc. In 30% of cases, secondary or complicated infections have nosocomial (hospital, nosocomial) origin. Finally, secondary infections are less treatable, often recur, involve a higher risk of renal parenchyma, the emergence of kidney abscess and urosepsis, and among the pathogens are found resistant to antibacterial drugs strains of microorganisms.

Among recurrent urinary tract infections, recurrent (true relapses), recurrent (reinfection), and resistant or asymptomatic bacteriuria are isolated.

[9], [10], [11], [12], [13], [14]