Urinary Tract infections common and uncommon kidney diseases jassin m. Jouria, md


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Urinary Tract INFECTIONS


Dr. Jassin M. Jouria is a practicing Emergency Medicine physician, professor of academic medicine, and medical author. He graduated from Ross University School of Medicine and has completed his clinical clerkship training in various teaching hospitals throughout New York, including King’s County Hospital Center and Brookdale Medical Center, among others. Dr. Jouria has passed all USMLE medical board exams, and has served as a test prep tutor and instructor for Kaplan. He has developed several medical courses and curricula for a variety of educational institutions. Dr. Jouria has also served on multiple levels in the academic field including faculty member and Department Chair. Dr. Jouria continues to serve as a Subject Matter Expert for several continuing education organizations covering multiple basic medical sciences. He has also developed several continuing medical education courses covering various topics in clinical medicine. Recently, Dr. Jouria has been contracted by the University of Miami/Jackson Memorial Hospital’s Department of Surgery to develop an e-module training series for trauma patient management. Dr. Jouria is currently authoring an academic textbook on Human Anatomy & Physiology.


The kidneys serve as the body’s filtration system. Waste and excess fluids are filtered out of the blood and excreted through the urine. When the kidneys are not working as they should, fluid, electrolytes, and wastes can build up to dangerous levels in the body, even to the point of being fatal. Because kidney disease often does not create noticeable symptoms until the disease is advanced, it is important that medical clinicians are able to recognize the symptoms as soon as they are present and take immediate steps to resolve or mitigate the impact.

Policy Statement

This activity has been planned and implemented in accordance with the policies of NurseCe4Less.com and the continuing nursing education requirements of the American Nurses Credentialing Center's Commission on Accreditation for registered nurses. It is the policy of NurseCe4Less.com to ensure objectivity, transparency, and best practice in clinical education for all continuing nursing education (CNE) activities.

Continuing Education Credit Designation

This educational activity is credited for 3 hours. Nurses may only claim credit commensurate with the credit awarded for completion of this course activity.

Pharmacology hours include .5 hours (30 minutes).

Statement of Learning Need

Clinicians need to understand the symptoms of the varied stages of kidney disease and the types of blood or urine laboratory testing that are available to detect abnormalities indicating early stages of kidney disease in order to take immediate steps to resolve or mitigate serious health outcomes.

Course Purpose

To provide health clinicians with knowledge about the varied types of kidney disease, as well as diagnostic methods to achieve early recognition of and to initiate and effectively treat kidney disease.

Target Audience

Advanced Practice Registered Nurses and Registered Nurses

(Interdisciplinary Health Team Members, including Vocational Nurses and Medical Assistants may obtain a Certificate of Completion)

Course Author & Planning Team Conflict of Interest Disclosures

Jassin M. Jouria, MD, William S. Cook, PhD, Douglas Lawrence, MA

Susan DePasquale, MSN, FPMHNP-BC – all have no disclosures

Acknowledgement of Commercial Support

There is no commercial support for this course.

Please take time to complete a self-assessment of knowledge, on page 4, sample questions before reading the article.

Opportunity to complete a self-assessment of knowledge learned will be provided at the end of the course.

  1. The most common organism causing urinary tract infection is ___________________, which is responsible for up to 80% of kidney and urinary infections.

    1. Klebsiella

    2. Enterococcus

    3. Staphylococcus saprophyticus

    4. Escherichia coli
       (E. coli)

  1. True or False: Kidney stones do not increase the development of urinary tract infections because the mineral and salt deposits that usually compose kidney stones inhibit the growth of infections.

    1. True

    2. False

  1. Urinary tract infections are more common in women than in men because

    1. the length of the urethra is shorter in women.

    2. the hormone estrogen makes women more susceptible.

    3. of gastrointestinal tract bacteria.

    4. of the higher incidence of epispadias in women.

  1. When a patient presents with symptoms of pyelonephritis (kidney infection) the clinician will perform two common laboratory tests, which are examining a urine specimen for red and white blood cell counts and

    1. a urine culture.

    2. a helical (spiral) computed tomography.

    3. a cystoscopy.

    4. a urethral swab for STD testing.

  1. If a clinician suspects a patient has pyelonephritis,

    1. antibiotics are started after laboratory test results are reviewed.

    2. antibiotics are started immediately only if the patient may have contracted the infection in the hospital.

    3. antibiotics are started immediately only if the patient’s immune system is impaired.

    4. antibiotics are started immediately.


A urinary tract infection can develop in any part of the urinary system, including the urethra, bladder, ureters, or kidneys. A person’s body is able to defend against a urinary tract infection if urine is able to flow normally from the kidneys, through the ureters to the bladder. This allows bacteria that enters the urinary system to be flushed out when a person urinates. Bacteria are able to remain in the urinary tract and cause infection when there is an obstruction to the flow of urine, or if urine flow is slowed. The classification of urinary tract infections is based on clinical assessment and existing research. While clinical findings based on urine microscopy and culture tests are the standard for diagnosing a urinary tract infection, the detection of bacteria in sterile (uncontaminated) urine samples and of bacteria that is difficult to culture poses challenges to prior treatment. While future research and efforts are underway to develop improved methods to identify causes of urinary tract infections for effective treatment, existing proven methods to test and diagnose infections in urologic patients are the primary focus.

Etiology And Basic Treatment Strategies For UTI

Urinary tract infections may be caused by bacteria invading the urine, which is normally a sterile body fluid. Bacteria most commonly gain access to the urine through the urethra, which can be exposed to bacteria from outside of the body. Common sources of bacteria that enter the urinary system are from the skin, anus, or vagina. Kidney infection, pyelonephritis, may be facilitated by the introduction of bacteria into the urinary system, from these outside sources, through the urethra.42 Because of the shorter length of the urethra in women, a urinary tract infection (UTI) is more common in women compared to men.

There are some factors that may predispose people to urinary tract infections. Sexual intercourse may increase the risk of urinary tract infections in women. Pregnant women may also be at higher risk for developing urinary tract infections. This may be caused by slower transit of urine from the ureters into the bladder because of increased pressure on the ureters from the enlarged uterus. Approximately 10% of pregnant women may develop urinary tract infections during their pregnancy.43
Kidney stones are another factor that may increase the likelihood of urinary tract infection. Stones can cause partial or complete obstruction to the flow of urine from the kidneys and ureters. This obstruction may act as a focus of infection in the urinary system, leading to urinary tract infections. Bladder catheters (i.e., Foley catheters) are sometimes placed into the bladder in order to aid the outflow of urine from the bladder. These are used in many settings, for example, paralysis with nerve damage to the bladder causing accumulation of urine without adequate emptying, bladder obstruction from an enlarged prostate, or immobilized or hospitalized patients who are not able to independently urinate. These catheters may act as a vehicle for bacteria to gain access to the urine inside the bladder causing urinary infections. In children some risk factors include female gender, an uncircumcised male, or a structural abnormality of the urinary system.44

The most common bacteria causing urinary tract infection are those that are normally seen in the vagina, gastrointestinal tract, or skin. By far, the most common organism causing urinary tract infection is Escherichia coli
 (E. coli), which is responsible for up to 80% of kidney and urinary infections. Other common bacteria include Klebsiella, Proteus, Pseudomonas, Enterococcus, and Staphylococcus saprophyticus.45

The diagnosis of a urinary tract infection is based on testing of a urinalysis, urine culture and, if needed, imaging tests. Typical symptoms of kidney infection or pyelonephritis lead physicians to do two common laboratory tests to determine whether the kidneys are infected; examining a urine specimen under a microscope to count the number of red and white blood cells and bacteria and a urine culture, in which bacteria from a urine sample are grown in a laboratory setting to identify the numbers and type of bacteria. Blood tests may be done to check for elevated white blood cell levels (suggesting infection), bacteria in the blood, or kidney damage. Imaging tests are done in people who have intense back pain that is typical of renal colic and who do not respond to antibiotic treatment within 72 hours, have symptoms return shortly after completion of antibiotic treatment, have long-standing or recurring pyelonephritis, have blood test results indicate kidney damage, and are performed in men (because they rarely develop pyelonephritis). Ultrasonography or helical (spiral) computed tomography (CT) studies done in these situations may reveal kidney stones, structural abnormalities, or other causes of urinary obstruction.46

Treatment of a urinary tract infection includes use of antibiotics and occasionally surgery (to correct abnormality of the urinary tract). Antibiotics are started as soon as the medical clinician suspects pyelonephritis and samples have been taken for laboratory tests. The choice of drug or its dosage may be modified based on the laboratory test results (including culture results), illness severity, and whether the infection started in the hospital, where bacteria tend to be more resistant to antibiotics. Other factors that can alter the choice or dosage of drug treatment include whether the person's immune system is impaired and whether the person has a urinary tract abnormality (such as an obstruction).47

Outpatient treatment with antibiotics given by mouth is usually successful if the person has no nausea or vomiting, signs of dehydration, other disorders that weaken the immune system, such as certain cancers, diabetes mellitus, or AIDS, signs of very severe infection, such as low blood pressure or confusion, and pain that is controlled with drugs taken by mouth.48 Otherwise, the person is usually treated initially in the hospital.

If hospitalization is needed and the person needs antibiotics, the antibiotics are given intravenously for 1 or 2 days, then they can usually be given by mouth. Antibiotic treatment of pyelonephritis is given for 5 to 14 days so that infection will not recur. However, antibiotic therapy may continue for up to 6 weeks for men in whom the infection is due to prostatitis, which is more difficult to eradicate. A final urine sample is usually taken shortly after the antibiotic treatment is finished to make sure the infection has been eradicated.39,50
Surgery is necessary only occasionally if tests show that something is chronically blocking the urinary tract, such as a structural abnormality or a particularly large stone. Removal of the infected kidney may be necessary for people with chronic pyelonephritis who are about to undergo kidney transplantation since a patient’s kidneys generally are not taken out when a donor kidney is transplanted. Spread of infection to the transplanted kidney is particularly risky because the person takes immunosuppressant drugs, which prevent rejection of the transplanted kidney but also weaken the body's ability to fight infection.51
People who have frequent episodes of a urinary tract infection or whose infection returns after antibiotic treatment is finished may be advised to take a small dose of antibiotic on a long-term basis. The ideal duration of such therapy is unknown. If the infection returns, preventive therapy may be continued indefinitely. If a woman of child-bearing age is taking an antibiotic, she should avoid pregnancy or talk to her medical clinician about whether to use an antibiotic that is safe during pregnancy in case she becomes pregnant.52

Bacterial Urinary Tract Infections

Bacterial urinary tract infections (UTIs) can involve the urethra, prostate, bladder, or kidneys. Symptoms may be absent or include urinary frequency, urgency, dysuria, lower abdominal pain, and flank pain. Systemic symptoms and even sepsis may occur with kidney infection. Diagnosis is based on analysis and culture of urine. Treatment is with antibiotics and removal of any urinary tract catheters and obstructions. Among adults aged 20 to 50 years, UTIs are about 50-fold more common in women. In women in this age group, most UTIs are cystitis or pyelonephritis. In men of the same age, most UTIs are urethritis or prostatitis. The incidence of UTI increases in patients great than 50 years of age, but the female:male ratio decreases because of the increasing frequency of prostate enlargement and instrumentation in men.53

The urinary tract, from the kidneys to the urethral meatus, is normally sterile and resistant to bacterial colonization despite frequent contamination of the distal urethra with colonic bacteria. The major defense against UTI is complete emptying of the bladder during urination. Other mechanisms that maintain the tract’s sterility include urine acidity, vesicoureteral valve, and various immunologic and mucosal barriers.51
About 95% of UTIs occur when bacteria ascend the urethra to the bladder and, in the case of pyelonephritis, ascend the ureter to the kidney. The remainder of UTIs are hematogenous. Systemic infection can result from UTI, particularly in the elderly. About 6.5% of cases of hospital-acquired bacteremia are attributable to UTI.46
Uncomplicated UTI
 is usually considered to be cystitis or pyelonephritis that occurs in premenopausal adult women with no structural or functional abnormality of the urinary tract and who are not pregnant and have no significant comorbidity that could lead to more serious outcomes. Also, some experts consider UTIs to be uncomplicated even if they affect postmenopausal women or patients with well-controlled diabetes. In men, most UTIs occur in children or elderly patients, are due to anatomic abnormalities or instrumentation, and are considered complicated.54

The rare UTIs that occur in men aged 15 to 50 years are usually in men who have unprotected anal intercourse or in those who have an uncircumcised penis, and they are generally considered uncomplicated. UTIs in men this age who do not have unprotected anal intercourse or an uncircumcised penis are very rare and, although also considered uncomplicated, warrant evaluation for urologic abnormalities.55

Complicated UTI can involve either sex at any age. It is usually considered to be pyelonephritis or cystitis that does not fulfill criteria to be considered uncomplicated. A UTI is considered complicated if the patient is a child, is pregnant, or has any of the following:56

  • A structural or functional urinary tract abnormality and obstruction of urine flow

  • A comorbidity that increases risk of acquiring infection or resistance to treatment, such as poorly controlled diabetes, chronic kidney disease, or immunocompromise

  • Recent instrumentation or surgery of the urinary tract 

Risk factors for development of UTI in women include the following:

  • Sexual intercourse

  • Diaphragm and spermicide use

  • Antibiotic use

  • New sex partner within the past year

  • History of UTIs in 1st-degree female relatives

  • History of recurrent UTIs

  • First UTI at early age

Even use of condoms that are spermicide-coated increases risk of UTI in women. The increased risk of UTI in women using antibiotics or spermicides probably occurs because of alterations in vaginal flora that allow overgrowth of Escherichia coli. In elderly women, soiling of the perineum due to fecal incontinence increases risk.47,48

Anatomic, structural, and functional abnormalities are risk factors for UTI. A common consequence of anatomic abnormality is vesicoureteral reflux (VUR), which is present in 30 to 45% of young children with symptomatic UTI. Vesicoureteral reflux is usually caused by a congenital defect that results in incompetence of the ureterovesical valve. Vesicoureteral reflux can also be acquired in patients with a flaccid bladder due to spinal cord injury or after urinary tract surgery. Other anatomic abnormalities predisposing to UTI include urethral valves (a congenital obstructive abnormality), delayed bladder neck maturation, bladder diverticulum, and urethral duplications.52

Structural and functional urinary tract abnormalities that predispose to UTI usually involve obstruction of urine flow and poor bladder emptying. Urine flow can be compromised by calculi and tumors. Bladder emptying can be impaired by neurogenic dysfunction, pregnancy, uterine prolapse, cystocele, and prostatic enlargement. Urinary tract infections caused by congenital factors manifests most commonly during childhood. Most other risk factors are more common in the elderly. Other risk factors for UTI include instrumentation (i.e., bladder catheterization, stent placement, cystoscopy) and recent surgery.57

The bacteria that most often cause cystitis and pyelonephritis include:

  • Enteric, usually gram-negative aerobic bacteria (most often)

  • Gram-positive bacteria (less often)

In normal genitourinary (GU) tracts, strains of Escherichia coli with specific attachment factors for transitional epithelium of the bladder and ureters account for 75% to 95% of cases. The remaining gram-negative urinary pathogens are usually other enterobacteria, typically Klebsiella or Proteus mirabilis, and occasionally Pseudomonas aeruginosa. Among gram-positive bacteria, Staphylococcus saprophyticus is isolated in 5% to 10% of bacterial UTIs. Less common gram-positive bacterial isolates are Enterococcus faecalis (group D streptococci) and Streptococcus agalactiae (group B streptococci), which may be contaminants, particularly if they were isolated from patients with uncomplicated cystitis.44,46

In hospitalized patients, E. coli accounts for about 50% of cases. The gram-negative species KlebsiellaProteusEnterobacterPseudomonas, and Serratia account for about 40%, and the gram-positive bacterial cocci, E. faecalisS. saprophyticus, and Staphylococcus aureus account for the remainder.


Nephritis is used to describe inflammation of one or both kidneys. If a kidney is inflamed, the functions of the kidney are disrupted to varying degrees depending on the type, cause and extent of inflammation. This disturbance is known as nephropathy. While the acute stages may cause only a temporary dysfunction, chronic inflammation can permanently damage kidney tissue, lead to scarring within the kidney, and even result in kidney failure. Both acute and chronic nephritis can be life-threatening if not treated and managed appropriately.75

Nephritis can be classified in several ways but the most common approaches is by the part of the kidney or nephron that is inflamed or by the cause and/or underlying disease responsible for the inflammation.76

  • Glomerulonephritis is inflammation of the glomerulus of the nephron.

  • Tubulointerstitial nephritis is inflammation of the tubule of the nephron and the surrounding interstitial tissue of the kidney. This is often referred to simply as interstitial nephritis.

  • Pyelonephritis is inflammation of the kidney, usually the renal pelvis, and the urinary tract associated with a urinary tract infection (UTI).

All these types of nephritis can be either acute or chronic. When nephritis is classified according to the cause, for example lupus nephritis associated with systemic lupus erythematosus or infectious nephritis associated with an infection, the entire kidney is often affected. If left untreated and depending on the severity and duration of the inflammation, the entire kidney may be destroyed. The following table outlines the varied types of nephritis and the potential health risks and adverse outcomes that can occur.75,77-82


Glomerulonephritis literally means inflammation of the glomerulus but includes a number of disorders that affect the structure and function of the glomerulus without any prominent inflammation. It is therefore also referred to as glomerular disease or glomerulopathy.

In glomerulonephritis, various known and unknown causes trigger immune activity against the glomeruli which damages it. The glomerulus is the head of the nephron which is responsible for filtering fluid from the blood. This fluid is later processed in the tubule (the rest of the nephron) until urine is eventually formed.

Each kidney has about 1 million nephrons that act together to complete the various functions including removing waste substances from the blood, regulating blood volume and blood pressure. If a significant number of nephrons are damaged, these functions will be significantly hampered.
The kidney is constantly losing nephrons with age. This is a slow process and only commences after the age of 40 years. For every decade of life thereafter, the kidney loses about 10% of its functioning nephrons. Since the progression is so gradual, the remaining healthy nephrons are able to compensate without any significant impairment of normal kidney functioning. In glomerulonephritis, however, there is a more rapid and extensive damage of the nephrons.
Glomerulonephritis is known to be an immune reaction mediated by antigen-antibody complexes. An antigen is the trigger substance against which antibodies are formed by the immune system. The antibodies then bind with the antigen and this antigen-antibody complex can instigate a number of immune activities designed to protect the body. In the process, inflammation arises in whichever tissue that the targeted immune response is occurring. Although the exact cause of glomerulonephritis is not always understood, the mechanism by which it occurs is proposed in two different models –immune complex deposition and circulating immune complexes.

Other mechanisms may involve cell-mediated injury or cytotoxic antibodies. In immune complex deposition, it is believed that antibodies are directed against antigens that are “planted” in the glomerulus or against antigens that are normal components of the glomerulus, specifically the glomerular basement membrane (GBM). The immune activity is therefore specifically targeted at the glomerulus. With circulating immune complexes, the antigen-antibody complexes are circulating in the bloodstream and eventually reach the glomerulus during glomerular filtration. These complexes form in the backdrop of several autoimmune or infectious diseases and the antigen may be endogenous (created within the body) or exogenous (from foreign matter or microorganisms) in nature.

In these cases, immune activity is targeted at the circulating immune complex and can lead to inflammation at other sites in the body as well as the glomerulus. In response to the inflammation, different histologic alterations may be seen in the glomerulus. This includes:

  • Increase in the number of cells (capillary endothelium or mesangial cells)

  • Thickening of the basement membrane

  • Tissue degeneration – hyalinosis and sclerosis

Glomerulonephritis may be primary or secondary. Primary glomerulonephritis arises on its own without any other underlying disease. Secondary glomerulonephritis occurs as a consequence of some other disease, which may not even involve the kidney. Furthermore, glomerulonephritis can be classified as acute or chronic.

In acute glomerulonephritis, the condition starts suddenly and the tissue damage progresses rapidly. With chronic glomerulonephritis, the condition develops gradually and damage becomes extensive after months or years.
There is a wide range of causes of glomerulonephritis. Some may solely involve the kidney while others are due to systemic disease which affect a number of organs simultaneously. Sometimes the cause of glomerulonephritis is unknown – idiopathic. The causes of glomerulonephritis may include:

  • Infections – post-streptococcal, subacute bacterial endocarditis, viral infections, parasitic infections like malaria and less commonly fungal infections.

  • Autoimmune diseases – systemic lupus erythematosus (SLE), Goodpasture’s syndrome, vasculitis (Wegener granulomatosis and polyarteritis nodosa), Henoch-Schönlein purpura.

  • Immune-mediated hypersensitivity (atopy) particularly in children.

  • Medication like those drugs used in the treatment of SLE and hemolytic-uremic syndrome.

  • Diabetes mellitus

  • Malignant hypertension (high blood pressure)

  • Amyloidosis
  • Inherited diseases like Alport’s syndrome.

  • Hodgkin’s lymphoma (mainly in adults).

Tubulointerstitial Nephritis

Tubulointerstitial nephritis is a group of diseases that affect the tubule of the nephron and/or surrounding interstitial tissue. It should be differentiated from similar diseases that predominantly affect the glomerulus, known as glomerulonephritis. However, tubulointerstitial disease may sometimes be related to glomerulonephritis but in these cases, the glomerular damage is minimal causing a mild disturbance.
Tubulointerstitial nephritis may be acute or chronic.

The acute stages are characterized by rapid onset of inflammation of the renal tubule that compromises its function. This tubular dysfunction is usually temporary. Inflammation is also present in chronic tubulonephritis along with structural damage to the tubule and/or interstitium. The injury is often irreversible in chronic states.

Tubulointerstitial nephritis is more commonly seen in women as the two most common causes, analgesic use and kidney infections, are more prevalent in females. However, it can affect men with the same risk factors equally. The two most common mechanisms associated with tubulonephritis is cellular injury by bacteria (infection) and toxins, and drug hypersensitivity which leads to an inappropriate immune response. 
Acute tubulointerstitial nephritis is marked by inflammation with associated swelling of the affected area.
Leukocyte infiltration of the renal tissue, particularly eosinophils and neutrophils, are prominent and in severe cases there is confined areas of cell death (necrosis). Most cases of acute tubulointerstitial nephritis are largely reversible since the tubules can regenerate if the basement membrane is intact.

With chronic tubulointerstitial nephritis, the long term inflammation and subsequent fibrotic scarring tends to lead to irreversible changes. If a small amount of the total nephrons are affected then kidney function is not severely compromised. However, it tends to lead to progressive chronic renal insufficiency. Infections of the upper urinary tract and kidney (pyelonephritis) accounts for a large number of cases of acute tubulointerstitial nephritis.

Chronic pyelonephritis associated with reflux nephropathy may also be a cause. Most infections are bacterial in nature, although viruses (HIV, HBV, CMV), fungi (histoplasmosis) and parasites can also cause tubulointerstitial nephritis. Drug hypersensitivity is largely responsible for acute tubulointerstitial nephritis and associated with drugs like NSAIDs, certain antibiotics, diuretics, anticonvulsants and proton pump inhibitors. It is known as acute-hypersensitivity interstitial nephritis.
Chronic cases are more often associated with toxicity caused by long term and/or excessive use of drugs like analgesics and lithium. Heavy metal toxicity, lead, mercury and cadmium poisoning may also be responsible for chronic tubulointerstitial nephritis but has decreased substantially with greater awareness of the toxicity associated with these metals.
Other toxins may include fungal toxins like ochratoxin (possibly related to Balkan endemic nephropathy) or plant toxins like aristolochic acid (Chinese herb nephropathy).

A number of immunologic diseases can cause acute and chronic tubulointerstitial nephritis. This includes:

  • Goodpasture syndrome

  • Systemic lupus erythematosus (SLE)

  • Sjogren syndrome

  • Sarcoidosis

  • Vasculitis

  • Wegener’s granulomatosis

Acute transplant rejection and chronic transplant nephropathy also need to be considered in patients following a kidney transplant.

The clinical features of tubulointerstitial nephritis may be non-specific and it is difficult to differentiate with other kidney disorders. It can, however, be differentiated from glomerulonephritis by the absence of nephrotic and nephritic syndrome as discussed under signs and symptoms of glomerulonephritis. The clinical presentation may also vary slightly depending on the causative factor and other underlying diseases.

The presentation in tubulointerstitial nephritis includes:

  • Polyuria. Passing of large amounts of urine, seen as frequent urination and waking at night to urinate (nocturia).

  • Hematuria (blood in the urine) may not be seen in every case of tubulointerstitial nephritis.

  • Metabolic acidosis. Accumulation of acids in the body fluid due to decreased excretion.

  • Changes in blood pressure – hypertension, hypotension or normal blood pressure.

  • Congestive heart failure

  • Headaches

  • Vomiting and/or diarrhea

  • Weight loss


Pyelonephritis is the medical term for inflammation of the renal pelvis, tubules and interstitium most commonly associated with an infection. It is a serious complication of a urinary tract infection (UTI), typically extending from the infected bladder (cystitis) as a result of an ascending infection.

A kidney infection may vary in severity but can be life-threatening and contribute to a host of other complications involving various systems other than the renal system. Although it can affect any age group and gender, pyelonephritis is more common in women who are generally prone to UTIs in comparison to men, given the shorter urethra. Most urinary tract infections (UTIs) affect the lower tract – urethra, bladder and rarely the lower half of the ureters. Since UTIs are more frequently due to an ascending infection – pathogens gain entry to the urethra and travel higher up the tract – there is risk of kidney infection if treatment is poor or delayed or there are other underlying urinary tract disorders. Typically, an infection of the lower urinary tract, particularly of the urethra (urethritis), is asymptomatic or causes very mild symptoms. Therefore, treatment may be delayed.

Treatment is usually sought early for a bladder infection (cystitis) due to the intensity of symptoms. However, the severity of the clinical presentation in pyelonephritis, which can vary, generally prompts a patient to immediately seek medical treatment. Failure to do so can permanently damage the kidney or even become life-threatening in a short period of time.
Pyelonephrititis (kidney infection) can be acute or chronic. Both cases are most commonly due to a bacterial infection although viruses, fungi and rarely parasites may be responsible. In the majority of the cases, the bacteria originate from the person’s own fecal matter.
It is more likely to occur in women due to a shorter urethra but personal hygiene is a significant contributing factor. The causative bacteria adhere to the urinary tract and its toxins causes localized inflammation.
A kidney infection most commonly occurs when there is an obstruction within the urinary tract which prevents urine outflow to some degree. Usually regular urination prevents an infection by the constant flushing of the urinary tract. Once the bacteria colonizes the distal urethra, it rapidly spreads up the urethra to eventually gain entry into the bladder. The vesicoureteral valve is designed to prevent backward flow of urine up into the ureter from the bladder. However, the inflammation associated with a bladder infection (cystitis) and other contributing factors allows for the backward flow (vesicoureteral reflux) which then introduces the bacteria into the ureters. From here, reflux may push urine n the ureter as high up as the renal pelvis (part of the kidney that communicates with the ureter) thereby allowing bacteria to invade the kidney.

Acute pyelonephritis is mainly due to bacterial invasion of the renal substance, and most commonly a result of E. coli (Escherichia coli) infection. As discussed, a kidney infection may arise as a complication of a UTI, therefore the modes of transmission and causative organisms are the same as the causes of a bladder infection. Less commonly, the causative organism may invade the kidney from surrounding organs or distant sites when it travels through the bloodstream (hematogenous spread). Risk factors include:

  • Urinary stones

  • Prostate enlargement (benign prostatic hyperplasia)

  • Urinary tract obstruction

  • Pregnancy

  • Sexually transmitted infections (STIs)

  • Diabetes mellitus

  • Immune deficiency

  • Surgery to the urinary tract

  • Urinary catheter

  • Anatomical abnormalities of the kidney and/or urinary tract

Chronic pyelonephritis is due to recurrent kidney infections or a persistent infection. The structural damage to the kidney in chronic pyelonephritis contributes to various other renal disorders like reflux nephropathy and even end-stage renal disease. The risk factors associated with chronic pyelonephritis may be the same as that of acute pyelonephritis and is more likely to occur in a person who is immunocompromised and/or with other urinary tract pathology. The signs and symptoms of pyelonephritis includes:

  • Back pain and/or flank pain which may extend to the groin.

  • Urinary frequency – frequent urination

  • Urinary tenesmus – constant urge to urinate

  • Dysuria – pain, usually burning, when urinating

  • Pyuria – pus in urine which presents as cloudy urine

  • Hematuria – blood in the urine

  • Fever

  • Nausea and vomiting

The presentation may vary in acute and chronic pyelonephritis. The onset of signs and symptoms in acute pyelonephritis is usually sudden. Usually most, if not all, of the signs and symptoms mentioned above are present in acute pyelonephritis and are intense. It will rapidly ease and resolve within a few days if the appropriate antibiotic therapy is commenced as early as possible.

Chronic pyelonephritis is generally more insidious in onset. In some cases, it may remain silent for periods of time, or present with only a few clinical manifestations, until it is diagnosed by the presence of systemic disturbances. Since chronic pyelonephritis is more likely to occur in the presence of pre-existing kidney disease, this may mask the onset of the infection.

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