Pyelonephritis - Causes, Symptoms and Treatments
One of the most common renal diseases, acute pyelonephritis (also known as acute infective tubulointerstitial nephritis) is a sudden inflammation caused by bacteria that primarily affects the interstitial area and the renal pelvis or, less often, the renal tubules. With treatment and continued follow-up care, the prognosis is good, and extensive permanent damage is rare.
Pyelonephritis occurs more often in females, probably because of a shorter urethra and the proximity of the urinary meatus to the vagina and the rectum-both conditions allow bacteria to reach the bladder more easily-and a lack of the antibacterial prostatic secretions produced in the male.
Incidence increases with age and is higher in certain groups. Sexually active women are more prone to pyelonephritis because intercourse increases the risk of bacterial contamination. About 5% of pregnant women develop asymptomatic bacteriuria; if untreated, about 40% develop pyelonephritis. In diabetics neurogenic bladder causes incomplete emptying and urinary stasis and glycosuria may support bacterial growth in the urine. Persons with other renal diseases have compromised renal function that aggravates susceptibility.
Causes of Pyelonephritis:
Acute pyelonephritis results from bacterial infection of the kidneys. The infecting bacteria usually are normal intestinal and fecal flora that grow readily in urine. The most common causative microbe is Escherichia coli, but Proteus, Pseudomonas, Staphylococcus aureus, and Enterococcusfaecalis (formerly Streptococcus faecalis) may also cause such infections.
Typically, the infection spreads from the bladder to the ureters, then to the kidneys, as in vesicoureteral reflux. Vesicoureteral reflux may result from congenital weakness at the junction of the ureter and the bladder. Bacteria refluxed to intrarenal tissues may create colonies of infection within 24 to 48 hours. Infection may also result from instrumentation (such as catheterization, cystoscopy, or urologic surgery), from a hematogenic infection (as in septicemia or endocarditis), or possibly from lymphatic infection.
Pyelonephritis may also result from an inability to empty the bladder (for example, in patients with neurogenic bladder), urinary stasis, or urinary obstruction due to tumors, strictures, or benign prostatic hyperplasia.
Signs and symptoms of Pyelonephritis:
Typical clinical features include urgency, frequency, burning during urination, dysuria, nocturia, and hematuria (usually microscopic but may be gross). Urine may appear cloudy and have an ammonia-like or fishy odor. Other common symptoms include a temperature of 102 F (38.9° C) or higher, shaking chills, unilateral or bilateral flank pain, anorexia, and general fatigue.
These symptoms characteristically develop rapidly over a few hours or a few days. Although the symptoms may disappear within days, even without treatment, residual bacterial infection is likely and may cause symptoms to recur later.
Diagnosis of Pyelonephritis:
Diagnosis requires urinalysis and culture.
Typical findings include:
t Pyuria (pus in urine): Urine sediment reveals the presence ofleukocytes singly, in clumps, and in casts; and, possibly, a few red blood cells.
t Signillcant bacteriuria: urine culture reveals more than 100,000 organisms/ul of urine.
t Low specific gravity and osmolality: These findings result from a temporarily decreased ability to concentrate urine.
t Slightly alkaline urine pH.
t Proteinuria, glycosuria, and ketonuria: These conditions are less common.
X-rays also help in the evaluation of acute pyelonephritis. A plain film of the kidneys-ureters-bladder may reveal calculi, tumors, or cysts in the kidneys and the urinary tract. Excretory urography may show asymmetrical kidneys.
Other conditions to consider are acute glomerulonephritis, acute renal artery dissection, acute renal vein thrombosis, renal infarct, obstructive uropathy, hepatitis, pancreatitis, cholecystitis, appendicitis, perforated viscus, splenic infarct, aortic dissection, and pelvic inflammatory disease.
Treatment of Pyelonephritis:
Treatment centers on antibiotic therapy appropriate to the specific infecting microbe after identification by urine culture and sensitivity studies. For example, Enterococcus requires treatment with ampicillin, penicillin G, or vancomycin. Staphylococcus requires penicillin G or, if resistance develops, a semisynthetic penicillin, such as nafcillin, or a cephalosporin. Escherichia coli may be treated with sulfisoxazole, nalidixic acid, and nitrofurantoin; Proteus. with ampicillin, sulllsoxazole, nalidixic acid, and a cephalosporin; and Pseudomonas, with gentamicin, tobramycin, and carbenicillin.
When the infecting microbe cannot be identified, therapy usually consists of a broad-spectrum antibiotic, such as ampicillin or cephalexin. lf the patient is pregnant, antibiotics must be prescribed cautiously. Urinary analgesics such as phenazopyridine are also appropriate.
Symptoms may disappear after several days of antibiotic therapy. Although urine usually becomes sterile within 48 to 72 hours, the course of such therapy is 10 to 14 days. Follow-up treatment includes reculturing urine 1 week after drug therapy stops, then periodically for the next year to detect residual or recurring infection. Most patients with uncomplicated infections respond well to therapy and don't suffer reinfection.
In infection from obstruction or Vesicoureteral reflux, antibiotics may he less effective; treatment may then necessitate surgery to relieve the obstruction or correct the anomaly. Patients at high risk of recurring urinary tract and kidney infections, such as those with prolonged use of an indwelling catheter or maintenance antibiotic therapy, require long-term follow-up.
Recurrent episodes of acute pyelonephritis can eventually result in chronic pyelonephritis.
Special considerations and Prevention tips of Pyelonephritis:
1. Administer antipyretics for fever.
2. Force fluids to achieve urine output of more than 2,000 ml/day. This helps to empty the bladder of contaminated urine. Don't encourage intake of more than 2 to 3 qt (2 to 3 L) because this may decrease the effectiveness of the antibiotics.
3. Provide an acid-ash diet to prevent stone formation.
4. Teach proper technique for collecting a clean-catch urine specimen. Be sure to refrigerate or culture a urine specimen within 30 minutes of collection to prevent overgrowth of bacteria.
5. Stress the need to complete prescribed antibiotic therapy, even after symptoms subside. Encourage long-term followup care for high-risk patients.
6. Observe strict sterile technique during catheter insertion and care.
Instruct female patients to avoid bacterial contamination by wiping the perineum from front to back after defecation. Advise routine checkups for patients with a history of urinary tract infections. Teach them to recognize signs of infection, such as cloudy urine, burning on urination, urgency, and frequency, especially when accompanied by a low-grade fever.
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