Pyelonephritis: Causes

Pathogenesis (development of disease)

The most common cause of acute pyelonephritis is ascending (ascending) infection; in addition, vesicouretral reflux (nonphysiologic reflux of urine from the bladder via the ureters into the renal pelvis) is a common cause of pyelonephritis. Hematogenous-descending (ascending via the bloodstream) development is also possible.Common causative agents are E. coli, P. mirabilis, or Klebsiellen.It is a granulocytic inflammation (purulent inflammation) with tissue necrosis (death of tissue). The tubules (renal tubules) are mainly affected. Chronic pyelonephritis results in inflammatory changes (scarring, deformity) of the kidney that promote the development of renal insufficiency (kidney weakness).Other – but less common – routes of infection include:

• Hematogenous – for example, in sepsis (blood poisoning).
• Lymphogenic

Possible causative agents of pyelonephritis are:

• Uropathogenic Escherichia coli (UPEC) (E. coli) – in 75-80% of cases (community-acquired urinary tract infection (UTI)).
• Staphylococcus (Staphylococcus saprophyticus).
• Klebsiella (Klebsiella pneumoniae)
• Proteus mirabilis
• Enterococci (most common in mixed infection).
• Enterobacter
• Pseudomonas
• Salmonella (0.5% of all UTIs) – patient usually has had a previous intestinal infection in such cases
• Other atypical pathogens, e.g. ureaplasma, mycoplasma.

Etiology (causes)

Biographical causes

• Genetic burden
  • Genetic diseases
    • Sickle cell anemia (med: drepanocytosis; also sickle cell anemia, English : sickle cell anemia) – genetic disorder with autosomal recessive inheritance affecting erythrocytes (red blood cells); it belongs to the group of hemoglobinopathies (disorders of hemoglobin; formation of an irregular hemoglobin called sickle cell hemoglobin, HbS).
• Anatomical features – for example, horseshoe kidney, double ureteral system, cystic kidneys.
• Adolescent age at the first urinary tract infection.
• Hormonal factors – gravidity (pregnancy).

Behavioral causes

• Nutrition
  • Micronutrient deficiency (vital substances) – see Prevention with micronutrients.
• Use of vaginal diaphragms and spermicides – this alters the normal bacterial vaginal flora (microbiota), so there may be an increase in the bacterium E. coli – Escherichia coli – in the vagina (vagina), which is associated with an increased risk of cystitis* (bladder infection)
• Sexual activity – coitus can cause bacteria to enter the bladder and cause cystitis* (= timely sexual intercourse). A micturition post-coital (urinating after sexual intercourse) can reduce the risk, as this flushes out any bacteria that may be present. Furthermore, the male partner should ensure adequate hygiene.

* Each cystitis (cystitis) increased risk of pyelonephritis.

Disease-related causes

• Inflammatory bowel disease (IBD) such as ulcerative colitis or Crohn’s disease – can lead to pyelonephritis via the bloodstream (hematogenous).
• Diabetes mellitus
• Urinary flow disorders* , e.g.:
  • Obstruction (obstruction) or anatomical abnormality of the urinary tract.
  • Benign prostatic hyperplasia (BPH) – benign enlargement of the prostate gland.
  • Urethral stricture (narrowing of the urethra) – for example, due to venereal diseases (sexually transmitted diseases) such as syphilis (lues) or gonorrhea (gonorrhea) – or congenital (congenital).
  • Nephrolithiasis (kidney stones), urolithiasis (urinary stones).
  • Neurogenic bladder emptying disorders – e.g. in diabetes mellitus, multiple sclerosis (MS), tabes dorsalis.
  • Vesicoureteral reflux (VUR; unphysiologic reflux of urine from the bladder via the ureters (ureters) into the renal pelvis) (urinary tract infections (UTIs) in childhood).
  • Pregnancy
• Gout
• HIV disease
• Immunodeficiency with accompanying immune deficiency* .
• Plasmocytoma (multiple myeloma) – malignant tumor disease from the group of non-Hodgkin’s lymphomas.Its origin is in the lymphoid tissue, as in all lymphomas; many (multiple) tumors originating in the bone marrow (myelomas).
• Tumor diseases of the genitourinary system
• Urolithiasis* (urinary stones)
• Cystitis (inflammation of the urinary bladder)

Medication

• Analgesics (painkillers), which are nephrotoxic with continuous therapy, such as phenacetin.
• Corticosteroids – lead to suppression of the immune system with prolonged use.
• Immunosuppressants* (drugs that reduce the functions of the immune system).
• Painkillers, which can damage the kidneys, such as phenacetin.
• Cytostatics (substances that inhibit cell growth or cell division).

Operations

• Surgery in the urinary tract (especially after transurethral resection of the prostate/urological surgical technique in which pathologically altered prostate tissue can be removed without an external incision through the urethra (urethra)).
• Instrumental urological procedures (e.g. cystoscopy / cystoscopy), which may be associated with germ transmission.
• Kidney transplantation* (NTx, NTPL).

Radiotherapy

• Radiatio (radiation therapy) in the urinary tract or pelvis* → weakening of the immune system.

Other causes

• Use of diaphragm and spermicides.
• Mechanical stimuli – foreign body in the urinary tract* (indwelling bladder catheter, suprapubic catheter/bladder catheter inserted above the pubic bone through the abdominal wall into the urinary bladder, ureteral stent, nephrostomy/application of a renal fistula to drain urine to the outside)
• Stress and constant tension – tense bladder walls increase risk due to decreased mucus production
• Gravidity (pregnancy)

* Risk factors for the development of complicated urinary tract infection.