Pyelonephritis refers to an inflammatory disorder of the kidney that may be acute, recurrent, or chronic. In simple words, chronic pyelonephritis (CP) is a long-standing kidney infection.
An acute inflammation that occurs repeatedly can lead to chronic pyelonephritis which permanently damages the kidney and can lead to end-stage renal disease. A kidney with chronic pyelonephritis has scarring and clubbing in place of functional kidney tissue which decimates its filtration capacity. Routine dialysis or kidney transplant is then required to sustain life.
CP occurs mostly in children and is 3 times more[i] prevalent in white children than African-American children. It is also most common in children younger than 2 years old because the leading cause of CP (discussed below) is a congenital anomaly that manifests in early life.
Causes and Risk Factors
The urinary tract consists of the kidneys, a pair of ureters that lead to the urinary bladder, and the urethra that leads urine to the urinary outlet. Any obstruction in this tract can cause stagnation and retrograde of urine which is toxic for the body tissues.
- An obstruction in the urinary tract – such as stones or other organs that enlarge and obstruct the passageway of urine.
- Reflux nephropathy (because of an obstruction or a urinary tract anomaly) – is a disease of the kidney caused by the reflux of urine in the urinary tract and back to the kidney.
Obstruction of the UT can also lead to reflux nephropathy, so the mechanism may be linked in some patients. Let us now take a look at some important causes of CP:
The most common pathology underlying CP is vesicoureteral reflux (VUR) – a weakening of the valve between the ureters and the urinary bladder. This valve ensures that urine flow remains one-way within the body. However, if it is leaky, urine can reflux back up the ureter and into the kidney. If the urine or the bladder contains bacteria, it can cause inflammation and set off pyelonephritis.
Additionally, the pressure in the bladder is normally higher than the urine. The reflux of urine from a higher-pressure organ to the kidneys that are usually exposed to low pressure can damage the functional tissue and cause scarring and loss of filtration units.
Since the valve is congenitally weak, VUR remains a consistent complaint and infection occurs repeatedly – leading to chronic pyelonephritis. 30-40% of children that present with UTIs also present with VUR, and almost all children with renal scarring have VUR. This shows the significance of VUR in the causation of urinary tract diseases.
If you suffer from UTIs repeatedly, you should consult a physician to rule out VUR. Usually, VUR is diagnosed in childhood and runs in the family. If a child is found to suffer from this condition, their siblings should be checked. If an adult is diagnosed with VUR, their children – especially their daughters – should be checked, too.
Kidney stones are a common problem in developed countries, with about 1.2 million Americans affected each year. They are pebble-like pieces that can form inside the kidney and can accumulate in any part of the urinary tract from the kidney to the bladder. They are formed from minerals like calcium, uric acid, and struvite.
Accumulation of kidney stones in the urinary tract can create an obstruction that leads to reflux nephropathy. It can also cause a rare form of CP called xanthogranulomatous pyelonephritis (XGPN)[iii] which is an inflammatory response in the kidney that leads to the destruction of kidney tissues.
Some Other Risk Factors of CP
There are a few other risk factors for CP that originate from non-renal disorders:
- A neurogenic bladder (due to spina bifida)[iv] has incompetent muscular control and can allow reflux of urine. Since spina bifida is congenital, the reflux is recurrent and can lead to CP.
- If a woman already suffers from some sort of renal injury, renal insufficiency during pregnancy may aggravate her condition and lead to CP and loss of renal function.
- In men, benign prostatic hyperplasia[v] is an enlargement of the prostate that constricts the urethra and prevents emptying of the bladder. This pressure can also cause thickening of the bladder wall which can lead to reflux and infection of the upper urinary tract. Men with BPH must seek immediate medical treatment to prevent the progression to CP.
What Are The Symptoms Of Chronic Pyelonephritis?
CP is asymptomatic in its early stages. The usual symptoms are similar to that of kidney infection or chronic kidney disease, like:
- Burning sensation while peeing
- Difficulty in peeing
- Flank pain (on one side of the affected kidney) or back and abdominal pain
- Needing to urinate during the night
- History of recurrent UTIs since childhood
- Ankle swelling
- Tiredness, fatigue
Children with CP may report these symptoms, too:
- Failure to thrive
- High blood pressure
- Tenderness on the sides
If CP has progressed to late stages, the patient will experience renal insufficiency and hypertension.
How Is Chronic Pyelonephritis Diagnosed?
Sometimes, CP does not produce any symptoms. However, there are some key diagnostic factors[vi] doctors use to identify CP. If the patient has a history of renal obstruction, kidney infection, or VUR, it is strongly indicative of CP.
Blood tests, urinalysis, and imaging are done to distinguish CP from any differential diagnoses. Blood test shows high blood creatinine and urinalysis may show renal epithelial cells, white blood cells, proteins, and bacteria.
Imaging techniques include ultrasound, helical CT, or intravenous urography (IVU). Classically, the kidney shows a deep segmental scar that runs within the kidney. Some segments of the kidney may show enlarged cells to compensate for the loss of tissue in other areas. The ureters may also be dilated due to chronic reflux.
In XGPN, the urine culture will almost always show E. coli or P. mirabilis, and a CT scan will detect the kidney stones that appear as a mass that may be causing distension of the kidney.
Treatment of Chronic Pyelonephritis
If an obstruction is causing CP, the treatment plan will aim to correct the obstruction. This involves the elimination of kidney stones and treatment of BPH if the patient suffers from either condition.
For reflux nephropathy that cannot be fixed, the patient must undergo long-term antibiotic therapy that may be required for the rest of their life. In XPGN, local infection is controlled with a course of antibiotics. Then, the scarred/granulomatous tissue of the kidney is surgically removed to prevent the further spreading of infection and preserve the remaining kidney.
If chronic pyelonephritis has progressed to end-stage renal disease, the patient must undergo routine dialysis or kidney transplantation to continue living.
See Also: Uti In Pregnant Women
The Bottom Line
The prognosis for CP is variable in all patients. If treated early on, the condition can be managed and patients may experience rare kidney infections. Others may require constant care under a kidney specialist. If you think you have any of the risk factors of chronic pyelonephritis, you should consult a physician immediately.
The urinary tract is susceptible to many other disorders and infections. Family Medicine Austin (FMA) specializes in diagnostic and preventative care in a wide array of fields. If you are facing any urinary tract problems, consult now with a UTI specialist at FMA!