Acute pyelonephritis

Although acute pyelonephritis is defined as inflammation of the kidney and renal pelvis, this diagnosis is clinical. The term "urinary tract infection" is used when infection is certainly present but there are no obvious signs of direct kidney damage. The term "bacteriuria" is used to indicate that bacteria are not only constantly present in the urinary tract but are actively multiplying.

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Causes acute pyelonephritis

Acute pyelonephritis is an acute bacterial infection that manifests itself as inflammation of the renal pelvis and parenchyma. Most often, urinary tract infections are caused by bacteria that live in the large intestine. Escherichia coli, which is present in large quantities in feces, causes 80 to 90% of primary urinary tract infections.

Strains of E. coli isolated during bacteriological examination of urine are also found on the skin around the external opening of the urethra, in the vagina, and in the rectum. Not all strains of E. coli have virulence factors. Of the numerous strains of E. coli (over 150), only some are uropathogenic, in particular serotypes 01.02.04.06,07,075.0150.

Frequent causative agents of urinary tract infections also include other gram-negative (Klebsiella pneumoniae, Enterobacter aerogenes/agglomerans; Proteus spp.) and gram-positive (Enterococcus faecalis, Staphylococcus saprophyticus) bacteria of the Enterobacteriaceae family. Anaerobic bacteria, which are present in the intestine in much larger quantities, very rarely affect the kidneys. It should also be noted that chlamydia and ureaplasma do not act as causative agents of acute pyelonephritis. Diseases such as atrophic vaginitis, sexually transmitted diseases (caused by chlamydia, gonococci, herpesvirus infection), as well as candidal and trichomonas vaginitis, which also cause frequent urination, are not classified as urinary tract infections.

Among the pathogenic agents, Proteus mirabilis plays a major role. It produces urease, which breaks down urea into carbon dioxide and ammonia. As a result, urine becomes alkaline, and triple phosphate stones are formed. The bacteria that settle in them are protected from the action of antibiotics. The reproduction of Proteus mirabilis promotes further alkalization of urine, precipitation of triple phosphate crystals, and the formation of large coral stones.

Urease-producing microorganisms also include:

• Ureaplasma urealyticum:
• Proteus spp.
• Staphylococcus aureus;
• Klebsiella spp.
• Pseudomonas spp.
• E. coli.

Mixed urinary tract infections, when several pathogens are isolated from the urine, are rare in primary acute pyelonephritis. However, in complicated acute pyelonephritis caused by hospital-acquired strains of microorganisms, especially in patients with various catheters and drains, stones in the urinary tract, after intestinal plastic surgery of the bladder, a mixed infection is often isolated.

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Pathogenesis

The development of acute bacterial pyelonephritis, of course, begins with the introduction of bacteria into the urinary tract. The process then proceeds depending on factors inherent in the micro- and macroorganisms and their interactions. The state of the general and local defense mechanisms determines susceptibility to urinary tract infections. The corresponding anatomical lesion in the kidney consists of a significant number of polymorphonuclear leukocytes in the interstitial space of the kidney and the lumen of the tubules, sometimes with sufficient density to form an abscess. Abscesses may be multifocal, suggesting metastatic spread from the bloodstream (bacteremia), or, more commonly, appear as a focal infection diverging in the renal papilla within a segment of the kidney, forming a wedge-shaped lesion that extends to the renal cortex (ascending route of infection).

In severe acute pyelonephritis (acute lobar nephronia), a localized, aliment-free bulge involving one or more renal lobules may be seen on intravenous urograms, CT scans, or ultrasound scans. The lesion may be difficult to distinguish from a tumor or abscess.

There are 3 known ways for pathogenic microorganisms to enter the urinary tract:

• ascending (colonization of the external opening of the urethra with intestinal bacteria, from where they penetrate into the urethra and bladder);
• hematogenous (for example, the spread of the pathogen to the kidneys with the formation of an abscess in staphylococcal bacteremia;
• contact (spread of microorganisms from neighboring organs, for example, with vesicointestinal fistula, formation of the bladder from a segment of the intestine).

Bacteria usually do not enter the urinary tract through glomerular filtration.

The most common route is ascending. Through the short female urethra, uropathogenic microorganisms that have colonized its external opening easily penetrate into the bladder, especially during sexual intercourse, which is why urinary tract infections are more common in women who are sexually active. In men, the risk of ascending infections is lower due to the greater length of the urethra, the distance of its external opening from the anus, and the antimicrobial properties of prostatic secretions. In infants with uncircumcised foreskin, in young men who are sexually active, and in elderly men, the accumulation of bacteria in the folds of the foreskin, poor hygiene, and fecal incontinence contribute to the colonization of the urinary tract with uropathogenic bacteria. Catheterization of the bladder and other endoscopic interventions on the urinary tract increase the risk of infection in both sexes. After a single catheterization, the risk is 1-4%; With constant catheterization and the use of open drainage systems, infection of the urine and urinary tract inevitably occurs within a few days.

Microorganisms, including mycobacteria and fungi, can penetrate the kidneys, bladder and prostate by the hematogenous route from the primary focus of infection in other organs (for example, renal abscess and paranephritis caused by staphylococci or pyogenic streptococci). Direct spread of infection from the intestine to the bladder occurs with vesicointestinal fistulas (as a complication of diverticulitis, colon cancer, Crohn's disease), while a large number of different types of enterobacteria (mixed infections), gas (pneumaturia) and feces are often found in the urine.

Until now, in domestic literature it is accepted to consider the hematogenous route of infection of the kidney as the main and almost the only route of infection of the kidney. This idea has been artificially created since the time of Moskalov and other experimenters who administered the pathogen intravenously to animals, thereby creating supravesical obstruction of the ureter by ligating it. However, even the classics of urology at the beginning of the last century clearly divided topical forms of acute infectious and inflammatory process in the kidney into "pyelitis, acute pyelonephritis and purulent nephritis". Most authors of modern foreign literature, as well as WHO experts in their latest classification (ICD-10) consider the urinogenous route of infection of the kidneys to be the main one.

The ascending (urinogenic) route of infection has been confirmed in experimental works by a large number of domestic and foreign researchers. It has been shown that bacteria (Proteus, E. coli and other microorganisms of the Enterobacteriaceae family) introduced into the urinary bladder quickly multiply and spread up the ureter, reaching the pelvis. The fact of the ascending process in the lumen of the ureter was proven by fluorescent microscopy on bacteria by Teplitz and Zangwill. From the pelvis, microorganisms, multiplying, reach the medulla with spreading towards the renal cortex.

The introduction of microorganism cultures into the bloodstream has convincingly shown that microorganisms do not penetrate from the bloodstream into the urine through intact kidneys, i.e. the generally accepted concept among doctors that a carious tooth can be the cause of acute pyelonephritis does not stand up to criticism for this reason and for the different pathogens of acute pyelonephritis and caries.

The predominantly ascending route of infection of the urinary tract and kidney is consistent with clinical data: a high frequency of unilateral uncomplicated acute pyelonephritis in women, a connection with cystitis, the presence of P-fimbriae in E. coli, with the help of which it adheres to the urothelial cell, and the genetic identity of bacteria isolated from urine, feces and vagina in women with primary acute pyelonephritis.

Various topical forms of acute inflammation of the kidney are characterized by different routes of infection: for pyelitis, the ascending (urinogenic) route of infection is common, for pyelonephritis - urinogenic and urinogenic-hematogenous, for purulent nephritis - hematogenous.

Hematogenous infection or reinfection of the kidney can complicate the course of uncomplicated urinogenic acute pyelonephritis with the development of bacteremia, when the affected kidney itself serves as the source of infection in the body. According to the international multicenter study PEP-study, in acute pyelonephritis, urosepsis is diagnosed in 24% of cases in different countries, and according to researchers, only in 4%. Apparently, in Ukraine, the severity of purulent acute pyelonephritis complicated by bacteremia is underestimated, which foreign authors interpret as urosepsis.

Risk factors for the development of a kidney abscess include a history of urinary tract infection, urolithiasis, vesicoureteral reflux, neurogenic bladder dysfunction, diabetes mellitus and pregnancy, as well as the properties of the microorganisms themselves, which produce and acquire pathogenicity genes, high virulence genes and resistance to antibacterial drugs. The localization of the abscess depends on the route of infection. In the case of hematogenous spread, the renal cortex is affected, and in the case of ascending spread, as a rule, the medulla and cortex.

The course of acute pyelonephritis and the risk of complications are determined by the primary or secondary nature of the infection. Primary (uncomplicated) acute pyelonephritis responds well to antibacterial therapy and does not cause kidney damage. Severe primary acute pyelonephritis may cause cortical shrinkage, but the long-term impact of this complication on renal function is unknown. Secondary kidney infections may cause severe renal parenchyma lesions, abscess, and paranephritis.

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Symptoms acute pyelonephritis

Symptoms of acute pyelonephritis can vary from sepsis caused by gram-negative bacteria to signs of cystitis with mild pain in the lumbar region.

Symptoms of acute pyelonephritis are most often manifested in weakly expressed local signs of inflammation. The patient's condition is moderate or severe. The main symptoms of acute pyelonephritis are as follows: malaise, general weakness, increased body temperature to 39-40 °C, chills, sweating, pain in the side or in the lumbar region, nausea, vomiting, headache.

Symptoms of cystitis are often observed. Characteristic are pain on palpation and percussion in the costovertebral angle on the affected side, facial flushing, and tachycardia. Patients with uncomplicated acute pyelonephritis usually have normal blood pressure. Patients with acute pyelonephritis against the background of diabetes mellitus, structural or neurological abnormalities may have arterial hypertension. Micro- or macrohematuria is possible in 10-15% of patients. In severe cases, urosepsis caused by gram-negative bacteria, necrosis of the renal papillae, acute renal failure with oliguria or anuria, renal abscess, and paranephritis develop. Bacteremia is detected in 20% of patients.

In secondary complicated acute pyelonephritis, including in hospitalized patients and patients with permanent urinary catheters, clinical symptoms of acute pyelonephritis range from asymptomatic bacteriuria to severe urosepsis and infectious toxic shock. Deterioration of the condition may begin with a sharp increase in pain in the lumbar region or an attack of renal colic due to impaired urine outflow from the renal pelvis.

Hectic fever is typical, when hyperthermia up to 39-40 °C is replaced by a critical drop in body temperature to subfebrile numbers with profuse sweating and a gradual decrease in pain intensity, up to complete disappearance. However, if the obstruction to the outflow of urine is not eliminated, the patient's condition worsens again, pain in the kidney area increases and fever with chills reappears. The severity of the clinical picture of this urological disease varies depending on age, gender, previous condition of the kidneys and urinary tract, the presence of hospitalizations before the current admission, etc. In elderly and senile patients, in weakened patients, as well as in the presence of severe concomitant diseases against the background of an immunosuppressive state, the clinical manifestations of the disease are erased or distorted.

In children, symptoms of acute pyelonephritis include fever, vomiting, abdominal pain, and sometimes loose stools. In infants and small children, symptoms of acute pyelonephritis may be vague and include only excitability and fever. The mother may notice an unpleasant odor to the urine and signs of straining to urinate. The diagnosis is made if pus, leukocytes, and bacteria are found in the analysis of freshly released urine.

The pathogens causing complicated urinary tract infections are often mixed, more difficult to treat, more virulent and resistant to antibacterial drugs. If a hospitalized patient suddenly develops signs of septic shock (especially after bladder catheterization or endoscopic interventions on the urinary tract), even in the absence of symptoms of urinary tract infection, urosepsis should be suspected. In complicated (secondary) urinary tract infections, the risk of urosepsis, renal papillary necrosis, renal abscess and paranephritis is especially high.

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Diagnostics acute pyelonephritis

The diagnosis of uncomplicated (non-obstructive) acute pyelonephritis is confirmed by a positive urine culture (bacterial count over 10 ⁴ CFU/ml) associated with pyuria. This clinical syndrome is virtually exclusive to women, most often between the ages of 18 and 40. Approximately 50% of patients with low back pain and/or fever have lower urinary tract bacteriuria. Conversely, the upper urinary tract may often be the source of bacteriuria in patients with or without symptoms of cystitis. Approximately 75% of patients with uncomplicated acute pyelonephritis have a history of lower urinary tract infection.

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Clinical diagnostics of acute pyelonephritis

Diagnosis of acute pyelonephritis is important due to the severity of the patient's condition, detection of urinary tract obstruction. Sometimes it is difficult to determine the stage of development of the infectious and inflammatory process in the kidney, which does not always correspond to the clinical picture of the disease. Although lower and upper urinary tract infections are differentiated by clinical data, it is impossible to accurately determine the localization of infection by them. Even such signs as fever and pain in the side are not strictly diagnostic for acute pyelonephritis, as they occur with lower urinary tract infection (cystitis) and vice versa. Approximately 75% of patients with acute pyelonephritis had a history of previous lower urinary tract infections.

Physical examination often reveals muscle tension on deep palpation at the costovertebral angle. Acute pyelonephritis may simulate gastrointestinal symptoms with abdominal pain, nausea, vomiting, and diarrhea. Asymptomatic progression of acute pyelonephritis to chronicity in the absence of obvious symptoms may occur in patients with immune deficiency.

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Laboratory diagnostics of acute pyelonephritis

Diagnosis of acute pyelonephritis is based on general urine analysis and bacteriological examination of urine for microflora and sensitivity to antibacterial drugs. If acute pyelonephritis is suspected, in addition to clinical symptoms, it is necessary to use methods to clarify the localization of the infection.

A general blood test usually reveals leukocytosis with a left shift in the white blood cell count. The concentration of urea and creatinine in the blood serum is usually within normal limits. Patients with a long-term complicated infection may have azotemia and anemia if both kidneys are involved in the inflammatory process. Proteinuria is also possible, both in uncomplicated and complicated acute pyelonephritis. A decrease in the concentrating ability of the kidneys is the most constant sign of acute pyelonephritis.

Proper collection of urine for testing is of great importance. Contamination of urine with the microflora of the urethra can only be avoided with a suprapubic puncture of the bladder. This method can be used to obtain urine from infants and patients with spinal cord injury. In other cases, it is used when it is impossible to obtain urine by other methods.

For the study, a midstream portion of urine is taken during independent urination. In men, the foreskin is first pulled back (in uncircumcised men) and the head of the penis is washed with soap and water. The first 10 ml of urine is a wash from the urethra, then urine from the bladder. In women, the probability of contamination is much higher.

Leukocyturia and bacteriuria are not detected in urine tests in all patients with acute pyelonephritis. When examining urine in patients with predominantly cortical locations of infection foci (apostematous acute pyelonephritis, renal abscess, perinephritic abscess) or with obstructive acute pyelonephritis (when urine flow from the affected kidney is blocked), leukocyturia and bacteriuria may not be present.

In urine tests, erythrocytes may indicate the presence of necrotic papillitis, stones in the urinary tract, an inflammatory process in the neck of the bladder, etc.

If acute pyelonephritis is suspected, a bacteriological analysis of urine for microflora and sensitivity to antibiotics is mandatory. It is generally accepted that a diagnostically significant microbial titer of 10 ⁴ CFU/ml is used to diagnose uncomplicated acute pyelonephritis in women. With a cultural study of urine, identification of microorganisms is possible only in a third of cases. In 20% of cases, the concentration of bacteria in urine is below 10 ⁴ CFU/ml.

Patients also undergo a bacteriological blood test for microflora (the result is positive in 15-20% of cases). A study of the culture of microorganisms in the blood, especially when multiple microorganisms are detected, more often indicates a paranephric abscess.

Thus, quite often antibacterial treatment is prescribed empirically, i.e. based on knowledge of bacteriological monitoring data in the clinic (department), data on the resistance of pathogens, based on clinical studies known from the literature and our own data.

Instrumental diagnostics of acute pyelonephritis

Diagnostics of acute pyelonephritis also includes radiation diagnostic methods: ultrasound scanning, X-ray and radionuclide methods. The choice of method, the sequence of application and the volume of studies should be sufficient to establish a diagnosis, determine the stage of the process, its complications, identify the functional state and urodynamics of the affected and contralateral kidneys. Among diagnostic methods, ultrasound scanning of the kidneys ranks first. However, if necessary, the study begins with chromocystoscopy to detect obstruction of the urinary tract or with an X-ray examination of the kidneys and urinary tract.

Ultrasound diagnostics of acute pyelonephritis

The ultrasound picture in acute pyelonephritis changes depending on the stage of the process and the presence or absence of urinary tract obstruction. Primary (non-obstructive) acute pyelonephritis in the initial period, in the phase of serous inflammation, may be accompanied by a normal ultrasound picture during kidney examination. In secondary (complicated, obstructive) acute pyelonephritis, at this stage of inflammation, only signs of urinary tract obstruction can be detected: an increase in the size of the kidney, expansion of its calyces and pelvis. As the infectious and inflammatory process progresses and interstitial edema increases, the echogenicity of the renal parenchyma increases, its cortex and pyramids are better differentiated. In apostematous nephritis, the ultrasound picture may be the same as in the phase of serous inflammation. However, the mobility of the kidney is often reduced or absent, sometimes the boundaries of the kidney become less clear, the cortical and medullary layers are less differentiated, and sometimes shapeless structures with heterogeneous echogenicity are revealed.

In case of kidney carbuncle, its external contour may bulge, hypoechoic structures may be heterogeneous, and there is no differentiation between the cortex and medulla. In case of abscess formation, hypoechoic structures are detected, sometimes the fluid level and abscess capsule are observed. In case of paranephritis, when the purulent process goes beyond the fibrous capsule of the kidney, the echograms show a picture of a heterogeneous structure with a predominance of echo-negative components. The external contours of the kidney are uneven and unclear.

With various obstructions (stones, strictures, tumors, congenital obstructions, etc.) of the upper urinary tract, dilation of the calyces, pelvis, and sometimes the upper third of the ureter is observed. In the presence of pus, inflammatory detritus, heterogeneous and homogeneous echo-positive structures appear in them. Ultrasound monitoring is widely used for dynamic observation of the development of acute pyelonephritis.

X-ray diagnostics of acute pyelonephritis

In the past, excretory urography was used mainly. However, this examination reveals changes in only 25-30% of patients. Only 8% of patients with uncomplicated acute pyelonephritis were found to have abnormalities that affected management.

Radiological symptoms in non-obstructive acute pyelonephritis in the early stages (serous inflammation) are weakly expressed. Intravenous urography is not recommended for the first few days after the onset of acute pyelonephritis for the following reasons:

• the kidney is not able to concentrate the contrast agent;
• a dilated segment of the proximal ureter may be confused with ureteral obstruction;
• RVC may cause acute renal failure in a dehydrated patient.

Intravenous urography is not indicated as a routine investigation in women with symptomatic urinary tract infection.

Kidney function, urodynamics on excretory urograms may be within normal limits. A slight increase in the size of the kidney contours and limitation of its mobility are possible. However, if the process passes into a purulent phase with the formation of carbuncles or abscess, the development of paranephritis, the X-ray picture takes on characteristic changes.

On general urograms one can see an increase in the size of the kidney contours, limited or no mobility (on inhalation and exhalation), a rarefaction halo around the kidney due to edematous tissue, bulging of the kidney contours due to a carbuncle or abscess, the presence of calculi shadows, blurring, smoothing of the contours of the large lumbar muscle, curvature of the spine due to rigidity of the lumbar muscles and sometimes displacement of the kidney. Excretory urography allows obtaining important information about renal function, urodynamics, X-ray anatomy of the kidneys and urinary tract. Due to inflammation and edema of the interstitial tissue, 20% of patients have an enlarged kidney or part of it. In the nephrographic phase, striation of the cortex can be seen. Stagnation of urine in the tubules caused by edema and narrowing of the renal vessels slow down the excretion of the contrast agent. In case of urinary tract obstruction, symptoms of blockage are revealed: "silent or white" kidney (nephrogram), kidney contours are enlarged, its mobility is limited or absent. In case of partial urinary tract obstruction, on excretory urograms after 30-60 minutes, dilated calyces, renal pelvis, ureter up to the level of obstruction can be seen. Retention of RVC in dilated renal cavities can be observed for a long time.

In acute necrotic papillitis (with obstruction of the urinary tract or against the background of diabetes mellitus), it is possible to see the destruction of the papillae, the erosion of its contours, deformation of the fornix arches, and penetration of the contrast agent into the renal parenchyma by the type of tubular reflux.

Computer tomography

CT with ultrasound sonography is the most specific method for assessing and localizing renal and perinephritic abscesses, but it is expensive. Often a wedge-shaped dense area can be seen on scans, which disappears after several weeks of successful treatment. In acute pyelonephritis, arterioles narrow, causing ischemia of the renal parenchyma.

Ischemic areas are detected by CT with contrast. On tomograms, they appear as single or multiple foci of low density. Diffuse renal damage is also possible. CT reveals kidney displacement and fluid or gas in the perirenal space associated with a perinephric abscess. Currently, CT is a more sensitive method than ultrasound. It is indicated for patients with obstructive acute pyelonephritis, bacteremia, paraplegia, diabetes mellitus, or patients with hyperthermia that is not relieved within a few days by drug therapy.

Other X-ray diagnostic methods - nuclear magnetic resonance imaging, angiographic methods in acute pyelonephritis - are used rarely and according to special indications. They can be indicated in the differential diagnosis of late purulent manifestations or complications of carbuncles, abscesses, paranephritis, suppurating cysts with tumors and other diseases, if the listed methods do not allow an accurate diagnosis to be established.

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Radionuclide diagnostics of acute pyelonephritis

These methods of research for emergency diagnostics of acute pyelonephritis are rarely used. They provide valuable information about the function, blood circulation of the kidneys and urodynamics, but at the stages of dynamic observation and detection of late complications.

Renal scintigraphy has the same sensitivity as CT in detecting ischemia in the setting of acute pyelonephritis. Radiolabeled 11Tc localizes to proximal tubular cells in the renal cortex, allowing visualization of functioning renal parenchyma. Renal scanning is particularly useful in detecting renal involvement in children and helps differentiate reflux nephropathy from focal acute pyelonephritis.

In renograms of primary non-obstructive acute pyelonephritis, the vascular and secretory segments are flattened and extended by 2-3 times, the excretion phase is weakly expressed or not traced. In the phase of purulent inflammation, due to circulatory disorders, the contrast of the vascular segment is significantly reduced, the secretory segment is flattened and slowed down, the excretory segment is weakly expressed. In case of total damage to the kidney by the purulent process, an obstructive curved line can be obtained in the absence of obstruction of the upper urinary tract. In secondary (obstructive) acute pyelonephritis, an obstructive type of curve can be obtained on renograms at all stages of inflammation, the vascular segment is low, the secretory segment is slowed down, and the excretory segment is absent on the affected side.

Differential diagnosis

Occasionally, a patient with acute pyelonephritis may complain of lower abdominal pain rather than the characteristic flank or renal pain. Acute pyelonephritis may be confused with acute cholecystitis, appendicitis, or diverticulitis and may occasionally have bacteriuria and pyuria. Appendiceal, tubo-ovarian, or diverticular abscesses adjacent to the ureter or bladder may be associated with pyuria. Pain from passing a stone through the ureter may mimic acute pyelonephritis, but the patient usually does not have fever or leukocytosis. Urine often shows red blood cells without bacteriuria or pyuria unless there is a concomitant urinary tract infection.

Treatment acute pyelonephritis

Indications for hospitalization

In the absence of nausea, vomiting, dehydration and symptoms of sepsis (systemic generalized reaction of the body), treatment of acute pyelonephritis is carried out on an outpatient basis, but on condition that the patient follows the doctor's instructions. In other cases, patients with primary pyelitis and acute pyelonephritis (as well as pregnant women) are hospitalized.

Drug treatment of acute pyelonephritis

For all forms of acute pyelonephritis, bed rest is indicated.

Antibacterial treatment of acute pyelonephritis is prescribed to outpatients for a period of 2 weeks. The European Urological Association Guidelines (2006) recommend using oral fluoroquinolones for 7 days as first-line therapy for mild acute pyelonephritis in regions with persistently low rates of E. coli resistance to fluoroquinolones (<10%). If a gram-positive microorganism is detected by microscopy of a Gram-stained smear, therapy with inhibitor-protected aminopenicillins may be recommended.

In more severe cases of uncomplicated acute pyelonephritis, hospitalization of the patient and parenteral treatment of acute pyelonephritis with fluoroquinolones (cilrofloxacin or levofloxacin), third-generation cephalosporins or inhibitor-protected amino/acylaminopenicillins are indicated, depending on the patient's condition and taking into account local data on the sensitivity of the pathogen to antibiotics. If the patient's condition improves, oral fluoroquinolones can be used to complete a 1- or 2-week course of treatment, respectively. In regions with an observed increase in E. coli resistance to fluoroquinolones, as well as in patients with contraindications to them (e.g., pregnancy, lactation, childhood), oral dosage forms of second- or third-generation cephalosporins are recommended.

In the absence of symptoms of the disease, a urine culture test after treatment is not indicated; for subsequent monitoring, a regular urine test using test strips is sufficient. In women with a relapse of symptoms of acute pyelonephritis within 2 weeks after treatment, a repeat urine culture test should be performed to determine the sensitivity of the isolated pathogen to antibiotics and additional studies should be performed to exclude structural disorders of the urinary tract.

In case of recurrent infection, antibacterial treatment of acute pyelonephritis is continued for up to 6 weeks. If fever and pain in the lumbar region and lateral abdomen persist for more than 72 hours after the start of treatment of uncomplicated acute pyelonephritis, repeated bacteriological tests of urine and blood, as well as ultrasound and CT of the kidneys are indicated to exclude complicating factors: urinary tract obstruction, anatomical anomalies, renal abscess and paranephritis. Bacteriological analysis of urine is repeated 2 weeks after treatment. In case of exacerbation of urinary tract infection against the background of urolithiasis, nephrosclerosis, diabetes mellitus, necrosis of the renal papillae, a 6-week course of antibacterial therapy is usually necessary, although a 2-week course can be limited and continued only in case of recurrent infection.

All pregnant women with acute pyelonephritis are hospitalized and parenteral antibiotics (inhibitor-protected beta-lactams, cephalosporins, aminoglycosides) are administered for several days until body temperature normalizes. Subsequently, oral antibiotics can be used. The duration of treatment is 2 weeks. After receiving the results of bacteriological analysis of urine, the treatment is adjusted.

Fluoroquinolones are contraindicated during pregnancy. It should be remembered that the use of sulfamethoxazole/trimethoprim in urinary tract infections and acute pyelonephritis is not recommended due to the high frequency of resistant strains of microorganisms causing urinary infections (over 20-30%). In pregnant women, sulfonamides interfere with the binding of bilirubin to albumin and can provoke hyperbilirubinemia in newborns. Gentamicin should be prescribed with caution due to the risk of damage to the vestibulocochlear nerve in the fetus.

Correct treatment of acute pyelonephritis leads to complete recovery, leaving no consequences. In children, when the formation of the kidney is not yet complete, acute pyelonephritis can lead to nephrosclerosis and renal failure. The most dangerous complications of acute pyelonephritis are sepsis and infectious-toxic shock. It is possible to form a kidney abscess, which requires its drainage.

When selecting an antibacterial drug for empirical therapy of clinically expressed complicated, secondary acute pyelonephritis, it is necessary to take into account the relatively large number of possible pathogens and the severity of the disease. Hospitalized patients with acute pyelonephritis and sepsis are initially empirically prescribed broad-spectrum antibiotics active against Pseudomonas aeruginosa, the Enterobacteriaceae family, Enterococcus spp. (ticarcillin/clavulanate or amoxicillin/clavulanate + gentamicin or amikacin; third-generation cephalosporins, aztreonam, ciprofloxacin, levofloxacin or carbapenems). After obtaining bacteriological analysis of urine and blood, therapy is adjusted depending on the results.

In secondary, complicated acute pyelonephritis, treatment is continued for 2-3 weeks, depending on the clinical picture of the disease. 1-2 weeks after the end of therapy, a bacteriological analysis of urine is repeated. In case of clinically expressed recurrent infection, longer antibacterial therapy is prescribed - up to 6 weeks.

When treating complicated or secondary acute pyelonephritis, it is important to remember that acute pyelonephritis will recur if anatomical or functional disorders of the urinary tract, stones, and drainages are not eliminated. Patients with permanent drainage in the urinary tract will have constant bacteriuria and exacerbation of urinary tract infection, despite successful treatment. The risk of such infections can be reduced by observing aseptic rules and using closed drainage systems. It is strictly recommended not to flush the drainage to avoid flushing biofilms into the renal pelvis with subsequent bacteremia and re-infection of the kidney! Periodic intermittent catheterization of the bladder is less likely to cause bacteriuria than the installation of permanent catheters. Drug prophylaxis of urinary tract infections in patients with permanent catheters and drainages is not effective.

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Surgical treatment of acute pyelonephritis

Although antibacterial drugs are necessary to control sepsis and spread of infection, when a renal abscess or perinephric abscess is detected, drainage is the first step. An increase in the detailed outcome (65%) is noted in patients treated only with medications compared with patients who underwent surgery for a renal abscess (23%). Surgery or nephrectomy are classic treatments for a non-functioning or severely infected kidney; some authors consider percutaneous aspiration and drainage of the abscess under ultrasound and CT control possible; however, percutaneous drainage is contraindicated in large abscesses filled with thick pus.

Surgical treatment of acute purulent pyelonephritis is usually performed for emergency indications. Catheterization of the ureter in case of its occlusion is not always an adequate method of drainage of the urinary tract. However, it is indicated for obstructive acute pyelonephritis due to a stone, ureteral stricture, tumor, etc.

It can be performed during the patient's preparation for surgery, as well as in the presence of severe concomitant diseases in the patient, when surgical treatment is impossible. The use of ureteral stents (self-retaining catheters) to restore urine passage in acute pyelonephritis is limited due to the impossibility of monitoring the stent function and determining renal diuresis, as well as due to possible reflux of urine into the kidney. Percutaneous puncture nephrostomy can be used according to indications for obstructive acute pyelonephritis. In case of deterioration of the patient's condition, the first signs of purulent inflammation in the kidney, despite the functioning nephrostomy, open surgery is used to drain purulent foci (renal abscess, paranephric abscess).

Before surgery, the patient must be informed of possible complications, in particular during nephrectomy, for which he must give his written consent.

It is important to remember that delay in diagnosis of renal abscess and perinephric abscess is of great importance for the prognosis of the disease. The importance of differential diagnosis between acute pyelonephritis and renal abscess, perinephric abscess is of fundamental importance. There are 2 factors that can help in differential diagnosis:

• In most patients with uncomplicated acute pyelonephritis, clinical symptoms of the disease developed less than 5 days before hospitalization, while in most patients with perinephric abscess, the clinical picture of the disease was more than 5 days;
• In patients with acute pyelonephritis, febrile body temperature lasts no more than 4 days after the start of antibacterial therapy: and in patients with perinephric abscess, fever persists for more than 5 days, on average about 7 days.

Patients with chronic renal failure, polycystic kidney disease are particularly susceptible to the progression of acute urinary tract infection to perinephric abscesses.

Before surgery, in addition to an ECG, chest X-ray, pulse and blood pressure, information about the function of the contralateral kidney is necessary.

The main stages and options for performing organ-preserving surgeries are as follows: after lumbotomy, the paranephric tissue is opened, examined for edema and signs of inflammation. Then the renal pelvis and ureteropelvic junction are isolated. In case of pedunculitis, pararenal and paraurethral sclerosis, the altered tissues are removed. The renal pelvis is opened most often in the form of a posterior transverse intrasinus pyelotomy.

If there is a stone in the renal pelvis or in the upper third of the ureter, it is removed. Stones located lower in the ureter are removed at subsequent stages of treatment, after the inflammatory process has subsided, most often by DLT. During revision of the kidney, its enlargement, edema, venous congestion, accumulation of serous-purulent fluid under the fibrous capsule, abscesses, carbuncles, apostemas, infarctions, paranephritis are noted. Further tactics depend on the changes detected. If it is necessary to drain the kidney, it is better to install a nephrostomy before opening the fibrous capsule of the kidney. A curved clamp is inserted into the pelvis through an incision and the renal parenchyma is perforated through the middle or lower cup. A nephrostomy drain is inserted into the pelvis so that the tip is located freely in its lumen and fixes it to the renal parenchyma together with the fibrous capsule. After suturing the renal pelvis, the kidneys are decapsulated if indicated (to relieve edema and ischemia of the renal tissue, to drain purulent foci). Pieces of the inflammatoryly altered renal parenchyma are sent for both histological and bacteriological examination. If carbuncles are present, they are excised, the renal abscess is either opened or excised with the capsule. The operation is completed with wide drainage of the perirenal space, areas of excision of carbuncles, abscesses and paranephric purulent cavities. Safety drains are installed. Ointments and antibiotics should not be used locally.

The decision to perform nephrectomy in purulent acute pyelonephritis is difficult and requires a consultation of doctors. There is no consensus and no evidence-based studies on the outcome of purulent acute pyelonephritis. There is no data on nephrosclerosis and kidney shrinkage after organ-preserving operations. There are no clear criteria for assessing the anatomical and functional disorders in the kidney in acute pyelonephritis to decide on nephrectomy.

In each specific case, indications for nephrectomy should be determined strictly individually, taking into account morphological and functional disorders in the kidney, the state of the body, the state of the other kidney, the patient's age (especially in children), the presence of concomitant diseases, the nature of the inflammatory process, including the possibility of sepsis and other complications in the postoperative period. Nephrectomy may be absolutely indicated in the case of purulent-destructive changes in the kidney with signs of thrombosis and involvement in the purulent process of more than 2/3 of the kidney mass, with multiple confluent carbuncles, a long-term purulent process in a blocked and non-functioning kidney.

Indications for nephrectomy in purulent acute pyelonephritis may arise in weakened patients due to concomitant diseases in the sub- and decompensation stage, in elderly and senile patients, as well as in urosepsis and after infectious toxic shock in the unstable state of vital organs. Sometimes nephrectomy is performed during surgery due to life-threatening bleeding from a kidney affected by a purulent process. Sometimes the kidney is removed in the second stage in weakened patients for whom in the acute period, for vital indications, it was possible to perform only drainage of a perirenal abscess or a kidney abscess, including percutaneous puncture nephrostomy. If antibacterial, detoxification therapy, local treatment are ineffective in the postoperative period, a decision is made to repeat the operation - nephrectomy with wide excision of the perirenal tissue and drainage of the wound.

It should be noted that, according to international studies, nosocomial acute pyelonephritis is complicated by urosepsis in 24%. If there is a suspicion of septic complications, which include signs of a systemic inflammatory response in the presence of at least one purulent focus of infection, it is necessary to decide on the use of extracorporeal methods of blood purification and detoxification.

Forecast

Uncomplicated acute pyelonephritis usually responds well to antibiotic therapy with minimal residual renal damage. Recurrent episodes are rare. In children, the acute changes of acute pyelonephritis are usually reversible and do not lead to new renal scarring or loss of renal function in most cases. Small scars demonstrated by dynamic renal scintigraphy do not reduce the glomerular filtration rate, and there is no difference in renal function between children with and without residual scarring. Children with repeated episodes of acute pyelonephritis and large scars have lower glomerular filtration rates on excretory urograms than healthy children.

In adult patients, residual renal function loss or scarring is rare after uncomplicated acute pyelonephritis. Renal scarring is usually due to reflux nephropathy that the patient had in childhood. Despite the benign course of uncomplicated acute pyelonephritis, isolated cases of acute renal failure associated with this clinical form of acute pyelonephritis have been described, whether in patients with a single kidney, or in those who abused analgesics, or in pregnant women. All patients recovered without the use of hemodialysis.

Septic syndrome, characterized by hypotension and disseminated intravascular coagulation, is also relatively rare in patients with acute pyelonephritis. It is more common in patients with diabetes mellitus.

[ 31 ], [ 32 ], [ 33 ], [ 34 ], [ 35 ]