Pyelonephritis: infection of the kidneys

Pyelonephritis

Acute pyelonephritis is defined as the upper urinary tract infection that affects the pelvis and the renal parenchyma. It is a clinical syndrome characterized by back pain, fever and chills; However, only 60% of patients with this triad is checked after having a pyelonephritis.
Its importance is due to the serious complications that can cause, even though most of the times early diagnosis and early treatment make it possible to allow the patient to evolve favourably. Acute pyelonephritis is divided into complicated or not complicated, as it exists or not an anatomical or functional disorder of the urinary tract which can influence the response to treatment and the clinical evolution of the patient. The presence of cystitis recurrent, kidney calculi (stones) or normal alterations in the form of the kidneys or urinary tract infections increase the risk of developing the disease.
Pyelonephritis is one of the diseases that most often affect the kidney, although it is not as frequent as lower urinary tract infections. Occur about 4-8 cases per 10,000 inhabitants. It is more frequent in women than in men, due to the anatomy of the female genital tract (urethra is shorter and is more exposed to the outside, so that access to it is easier), which facilitates the bacteria colonize the bladder and reach the kidneys through the ureters, causing pyelonephritis. With age, the incidence of pyelonephritis is increased in males, due to the development and enlargement of the prostate.

Causes of pyelonephritis

The most frequent mechanism by which acute pyelonephritis occurs is the rise of micro-organisms from faecal flora through the ureters, which are the tubes that connect the kidneys to the bladder. Less commonly, occurs by Hematogenous spread, i.e. through the blood. The germs that tend to invade the urinary tract by this method include Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella spp and Mycobacterium tuberculosis.
Microorganisms causing pyelonephritis most often, are enterobacteria as Escherichia coli, Klebsiella spp and Proteus spp, being E. Coli cause more frequent of pyelonephritis in patients without known urologic diseases (produces more than 80% of cases).
On the other hand, in patients with risk factors (recent handling of the urinary tract, urinary catheters carriers, which have been treated with antibiotics recently, or who have acquired the infection in hospital) are more common germs resistant to conventional antibiotics.

Symptoms of pyelonephritis

The most common symptoms that appear in patients with pyelonephritis are as follows:
• Fever (body temperature higher than 38.5 ° C) and chills.
• Pain in the lower back, although occasionally may radiate to other parts of the abdomen. If the pain is cramping (spasmodic, intense, that it begins and ends suddenly) and radiates to the groin is suggestive of renal lithiasis (presence of stones or stones in the kidney).
• Nausea and vomiting. Decreased appetite.
• Headache.
• Up to 30% of patients develop symptoms of infection of the lower urinary tract, which may precede the symptoms typical of pyelonephritis in 1 or 2 days. These symptoms are:
Increase in frequency of urination, but in small quantity (frequency).
Burning or pain when urinating (dysuria).
Feeling not have urinated completely (bladder tenesmus).
Feeling of not being able to contain urine and the need to urinate urgently by risk of urinary incontinence (urinary urgency).
Abdominal pain in the lower abdomen.
The persistence of fever within 72 hours after initiating treatment, or worsening of symptoms at any time of evolution, can be due to infection by a microorganism resistant provided treatment, or the presence of complications such as renal abscess , or sepsis.

Diagnosis of pyelonephritis

The presence of the triad of symptoms consisting of fever, chills and back pain suggests the existence of an acute pyelonephritis, but as he has been said previously only in 60% of patients with these symptoms is checked subsequently that they have the disease. The physical examination is important to try to guide the diagnosis of pyelonephritis, although physical findings are highly variable. In fact, in many cases it can be completely normal. One of the most characteristic is the presence of pain on percussion in the lumbar region on the affected side.
Suspected pyelonephritis following complementary tests must be made:
• Blood: must include a complete blood count (analytical test that provides information about the different types of cells present in the blood, mainly white blood cells, red blood cells and platelets), and a biochemistry that allows to check the function of the kidney.
In the blood is often an increase in the number of WBCs, even in advanced cases the number of these may be normal or even low. This information (presence of few white blood cells) is considered poor prognosis, since it increases the possibility of developing sepsis of renal origin. In biochemistry are poor prognosis data parameters lift as creatinine or urea, indicating kidney failure (the measurement of these substances in blood is used to monitor the correct function of the kidneys).
• Urinalysis: the presence of pyuria (pus in the urine) is a nearly constant finding, although it may not be present in some cases. On the other hand, the presence of nitrites in urine is also quite frequent, although some cavity-causing pyelonephritis germs do not produce nitrites (nitrates are substances present in urine which are converted to nitrites by the action of bacteria, suggesting the existence of urinary tract infection).
• Cultivation of urine or urine culture: is the key test to establish which microorganism is causing pyelonephritis. You must collect half of the Jet, discarding the first part of urination, and having previously wash the genital region. The sample must be collected before initiating treatment with antibiotics.
• Blood or blood culture: must be obtained if the patient presents fever. It is only positive in 20-30% of the patients, being more frequent in elderly people, diabetics, patients with kidney failure, or if there is obstruction of the urine flow.
• Imaging: Imaging tests are not needed in the non-complicated acute pyelonephritis. Simple abdomen radiography is indicated if the existence of urolithiasis is suspected by the symptoms that describes the patient, by their background, or if the patient is diabetic and suffers a severe pyelonephritis. Abdominal ultrasound is indicated only in patients with significant involvement of the general condition, signs of sepsis, or risk factors for urinary tract abnormalities, to rule out the existence of obstruction. The persistence of fever after 48-72 hours despite a correct antibiotic treatment, is also indication for an abdominal ultrasound to rule out the existence of a renal abscess.

Treatment of pyelonephritis

Given that it is a disease of infectious cause, the treatment of acute pyelonephritis is based on the administration of antibiotics, either orally or intravenously, depending on each case. The duration of treatment should be 14 days in the not complicated pyelonephritis, and 14-21 days at the complex.
Most of the time treatment of acute pyelonephritis is empirical; i.e. begins treatment with antibiotic blindly, without knowing really what germ is causing the infection. The antibiotics used in an empirical way must have the following characteristics: be active against more than 95% of the strains of Escherichia coli, reach high and maintained in the urinary tract and the blood concentrations, and respect the vaginal and rectal flora (if they do not, increases the risk of recurrences).
The treatment of pyelonephritis can be outpatients sometimes; i.e., the patient can be treated at home, while in others is necessary to enter the hospital. Entry criteria are the existence of sepsis, local complications (pain intense, emission of blood in the urine, acute renal failure...), than the patient present important diseases that might influence the response to the treatment (diabetes, cirrhosis, tumors, transplants, problems associated with aging...), that you can not meet treatment orally, or there is a bad evolution after 6-12 hours of observation once antibiotic treatment has started.
Antibiotics to choose depend on each specific case. For example, in those patients at risk develop pyelonephritis by resistant germs are used more powerful antibiotics that in patients who do not have them. In addition, in each area of the world, the resistance of germs to antibiotics is different.
Apart from the treatment with antibiotics is important to introduce General measures, such as:
• Rest in bed, if there is impairment of general condition.
• Abundant intake of fluids (about three litres a day), to increase the amount of urine. In case of existence of obstruction of the urinary tract the hydration of the patient must be performed with caution, because if no complications can appear.
• Administration of drugs to reduce fever and pain relievers.
• If there are other associated symptoms (vomiting, etc.) are treated with drugs suitable for this.

Prognosis of pyelonephritis

If antibiotic treatment begins quickly and in a proper way, the prognosis of acute pyelonephritis is usually good most of the time, and patients evolving pretty well. However, the existence of important diseases (diabetes, cirrhosis, renal failure...), or the appearance of complications severe sepsis increases the risk and they may complicate the course of this disease.
The main complications that may occur in acute pyelonephritis are the existence of a permanent kidney damage (may cause chronic renal failure), the development of an renal abscess (accumulation of pus in the kidney), or the appearance of a sepsis, which is a potential cause of death, especially in elderly patients.
Other complications of acute pyelonephritis is the evolution towards a chronic pyelonephritis, which is the consequence in the adult of renal damage due to recurrent infections that affect the kidney in children (acute pyelonephritis recurrence). It is more typical of women, and its most common cause is vesicoureteral reflux (urine flows from the bladder upwards by the ureters, thus increasing the risk of infections and can cause permanent damage in the kidney). If the disease is bilateral it may condition chronic renal failure. Findings on Imaging tests are very characteristic, being able to see scars on the walls of the kidney, thinning, or decrease in kidney size.

Article contributed for educational purposes