What is Acute Pyelonephritis
Acute pyelonephritis is a localized inflammation that affects the mucosa of the renal pelvis (or renal pelvis) and the kidney; it is often caused by the spread of an infection sustained by pathogens belonging to the intestinal bacterial flora, which can reach the kidney through three ways: ascending from the bladder (the most common), blood from the blood and lymphatic from the lymph.
Symptoms indicative of acute inflammation are high fever, chills, lumbar pain, dysuria and renal involvement on physical examination.
The infection causes an inflammatory process in the kidney, of a suppurative nature, with the formation of small abscesses distributed in the affected organ.
Pyelonephritis has a benign evolution: if proper treatment is used, symptoms tend to regress in about two weeks. In the case of concomitant urinary anomalies, the infection may prove to be particularly resistant to treatment and, sometimes, there may be an evolution in the chronic form of the disease.
Incidence
Pyelonephritis can affect subjects of any sex and age, but there is a greater incidence in women and children, for the following reasons:
- Women: they have a shorter urethra than men and, during pregnancy, the uterus can compress the urinary tracts even more. Other factors that make the female sex more exposed can be hormonal changes and urethral traumas during sexual intercourse.
- Children: they present with a greater frequency than the vesico-ureteral reflux phenomenon.
Causes and risk factors
The cause of acute pyelonephritis is often to be found in a urinary tract infection, which can be ascertained and diagnosed by urine culture.
The presence of bacteria in the urine (they are sterile, in general, in the healthy subject) in a significantly high number, makes clear the presence of an infection, which can materialize precisely in the onset of pyelonephritis. Most cases of pyelonephritis are due to intestinal microorganisms entering the urinary tract, such as Escherichia coli (in 70-80% of cases) and Enterococcus faecalis . Nosocomial infections (contracted in the hospital) can be due to coliform bacteria and enterococci, as well as to other less common organisms (eg Pseudomonas aeruginosa and various species of Klebsiella ). Most cases of pyelonephritis begin as lower urinary tract infections, especially cystitis and prostatitis. Escherichia coli can invade the "umbrella" cells of the bladder (thus defined as each of them covers more cells than the intermediate layer) to form intracellular bacterial communities, which can mature in biofilm (complex aggregation of microorganisms characterized by the secretion of an anchor matrix); the latter are resistant to antibiotic therapy and immune system responses, so much so as to represent a possible explanation for recurrent urinary tract infections, including pyelonephritis.
Several factors predispose to pyelonephritis:
- Anatomical-functional alterations, which can cause obstruction of urinary flow or facilitate pathogenic entry into the bladder:
- structural defects of the urinary tract, such as some congenital malformations;
- shorter urethra in women: it favors the colonization of the urinary tract by microorganisms of intestinal origin, due to their access to the vaginal vestibule. Similarly, sexual intercourse facilitates the entry into the urethra of pathogens;
- tumors, stenosis, kidney stones, prostatic hypertrophy;
- neurological damage to the bladder and sphincters (spina bifida, multiple sclerosis).
- Incomplete bladder emptying.
- Catheterization.
- Predisposing diseases of various kinds: metabolic diseases (Diabetes Mellitus, hyperuricemia), immunodepression, neurological pathologies etc.
- Pregnancy is a condition that makes people susceptible to acute pyelonephritis due to increased production of estrogen (dilation of ureters, pelvis and bladder) and enlargement of the uterus (compression on ureters and bladder with urine stagnation).
Vesicoureteral reflux (reflux of urine from the bladder to the ureter and sometimes towards the renal parenchyma) and incomplete emptying of the bladder favor an ascending infection that reaches the kidney.
During insertion of a catheter, bacteria can be transported into the bladder intraluminally or through contact with the external surface. Ureteral stents (small tube inserted into the ureter to prevent or resolve obstruction of urine flow from the kidney) or drainage procedures (for example: nephrostomy) can also increase the risk of developing pyelonephritis.
Symptoms
The onset of the disease is usually rapid, with symptoms that develop rapidly over a few hours or a day. Pyelonephritis can cause discomfort, nausea, vomiting, painful urination and abdominal pain, unilateral or bilateral, which radiates along the side towards the back.
The onset of fever is variable, but usually its onset causes violent chills and is associated with a bad state of general health (fatigue, weakness, anorexia, etc.).
Pyelonephritis is often associated with symptoms of infection in the lower urinary tract, such as frequent urination, haematuria (the urine may present blood) or dysuria (emission of urine with difficulty, not necessarily accompanied by pain). The bacteriological examination of urine is essential to confirm the diagnosis of infection. Urine is cloudy due to the presence of cells (pyuria) or bacteria (bacteriuria).
The patient suffering from acute pyelonephritis commonly presents lumbar pain (at the level of one or both kidneys), which occurs suddenly and may have a variable intensity (generally moderate, the patient accuses sensitivity of the kidney to palpation, in the course of diagnosis).
