Pyelonephritis

Key takeaways

Pyelonephritis belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Pyelonephritis to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Pyelonephritis from memory before moving on to harder problems.

Reference excerpt

Pyelonephritis is inflammation of the kidney, typically due to a bacterial infection. Symptoms most often include fever and flank tenderness. Other symptoms may include nausea, burning with urination, and frequent urination. Complications may include pus around the kidney, sepsis, or kidney failure. It is typically due to a bacterial infection, most commonly Escherichia coli. Risk factors include sexual intercourse, prior urinary tract infections, diabetes, structural problems of the urinary tract, and spermicide use. The mechanism of infection is usually spread up the urinary tract. Less often infection occurs through the bloodstream. Diagnosis is typically based on symptoms and supported by urinalysis. If there is no improvement with treatment, medical imaging may be recommended. Pyelonephritis may be preventable by urination after sex and drinking sufficient fluids. Once present it is generally treated with antibiotics, such as ciprofloxacin or ceftriaxone. Those with severe disease may require treatment in hospital. In those with certain structural problems of the urinary tract or kidney stones, surgery may be required. Pyelonephritis affects about 1 to 2 per 1,000 women each year and just under 0.5 per 1,000 males. Young adult females are most often affected, followed by the very young and old. With treatment, outcomes are generally good in young adults. Among people over the age of 65 the risk of death is about 40%, though this depends on the health of the elderly person, the precise organism involved, and how quickly they can get care through a provider or in hospital.

Signs and symptoms

Signs and symptoms of acute pyelonephritis generally develop rapidly over a few hours or a day. It can cause high fever, pain on passing urine, and abdominal pain that radiates along the flank towards the back. There is often associated vomiting. Chronic pyelonephritis causes persistent flank or abdominal pain, signs of infection (fever, unintentional weight loss, malaise, decreased appetite), lower urinary tract symptoms and blood in the urine. Chronic pyelonephritis can in addition cause fever of unknown origin. Furthermore, inflammation-related proteins can accumulate in organs and cause the condition AA amyloidosis. Physical examination may reveal fever and tenderness at the costovertebral angle on the affected side.

Causes Most cases of community-acquired pyelonephritis are due to bowel organisms that enter the urinary tract. Common organisms are E. coli (70–80%) and Enterococcus faecalis. Hospital-acquired infections may be due to coliform bacteria and enterococci, as well as other organisms uncommon in the community (e.g., Pseudomonas aeruginosa and various species of Klebsiella). Most cases of pyelonephritis start off as lower urinary tract infections, mainly cystitis and prostatitis. E. coli can invade the superficial umbrella cells of the bladder to form intracellular bacterial communities (IBCs), which can mature into biofilms. These biofilm-producing E. coli are resistant to antibiotic therapy and immune system responses, and present a possible explanation for recurrent urinary tract infections, including pyelonephritis. Risk is increased in the following situations:

Mechanical: any structural abnormalities in the urinary tract, vesicoureteral reflux (urine from the bladder flowing back into the ureter), kidney stones, urinary tract catheterization, ureteral stents or drainage procedures (e.g., nephrostomy), pregnancy, neurogenic bladder (e.g., due to spinal cord damage, spina bifida or multiple sclerosis) and prostate disease (e.g., benign prostatic hyperplasia) in men Constitutional: diabetes mellitus, immunocompromised states Behavioral: change in sexual partner within the last year, spermicide use Positive family history (close family members with frequent urinary tract infections)

Diagnosis

Laboratory examination Analysis of the urine may show signs of urinary tract infection. Specifically, the presence of nitrite and white blood cells on a urine test strip in patients with typical symptoms are sufficient for the diagnosis of pyelonephritis, and are an indication for empirical treatment. Blood tests such as a complete blood count may show neutrophilia. Microbiological culture of the urine, with or without blood cultures and antibiotic sensitivity testing are useful for establishing a formal diagnosis, and are considered mandatory.

Imaging studies If a kidney stone is suspected (e.g. on the basis of characteristic colicky pain or the presence of a disproportionate amount of blood in the urine), a kidneys, ureters, and bladder x-ray (KUB film) may assist in identifying radioopaque stones. Where available, a noncontrast helical CT scan with 5 millimeter sections is the diagnostic modality of choice in the radiographic evaluation of suspected nephrolithiasis. All stones are detectable on CT scans except very rare stones composed of certain drug residues in the urine. In patients with recurrent ascending urinary tract infections, it may be necessary to exclude an anatomical abnormality, such as vesicoureteral reflux or polycystic kidney disease. Investigations used in this setting include kidney ultrasonography or voiding cystourethrography. CT scan or kidney ultrasonography is useful in the diagnosis of xanthogranulomatous pyelonephritis; serial imaging may be useful for differentiating this condition from kidney cancer.

Ultrasound findings that indicate pyelonephritis are enlargement of the kidney, edema in the renal sinus or parenchyma, bleeding, loss of corticomedullary differentiation, abscess formation, or an areas of poor blood flow on doppler ultrasound. However, ultrasound findings are seen in only 20–24% of people with pyelonephritis. A DMSA scan is a radionuclide scan that uses dimercaptosuccinic acid in assessing the kidney morphology. It is now the most reliable test for the diagnosis of acute pyelonephritis.

Classification

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Illustrations

Pyelonephritis: Diagram showing the typical location of pain[8] — Diagram showing the typical location of pain[8]

Worked examples

Example 1 — a first encounter with Pyelonephritis

Start with the simplest possible case. Write down what Pyelonephritis claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Pyelonephritis before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Pyelonephritis ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Pyelonephritis

In research: Pyelonephritis appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Pyelonephritis in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Pyelonephritis is common in secondary-school and first-year university syllabi. It links to neighbouring topics Inflammations, Kidney diseases, Nephrology, so understanding it makes those chapters shorter.
In everyday life: Look for Pyelonephritis outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Pyelonephritis in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Pyelonephritis means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Pyelonephritis out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Pyelonephritis in simple terms?

Pyelonephritis is inflammation of the kidney, typically due to a bacterial infection. Symptoms most often include fever and flank tenderness.

Why does Pyelonephritis matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Pyelonephritis?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Pyelonephritis.