AN INFECTION of the kidney parenchyma and renal pelvis, primarily by Gram-negative bacteria, pyelonephritis can be acute or chronic.1 Untreated and/or recurrent pyelonephritis can lead to complications such as renal abscess or fibrosis, sepsis, acute kidney injury, or chronic kidney disease.2 The infection is more common in women.3
Bacteria commonly reach the kidney by ascending from the lower urinary tract, and less commonly, from the bloodstream. Contributing factors for infections include vesicoureteral reflux, neurogenic bladder, and urinary tract obstruction such as from ureteral calculi.1,4
Additional risk factors for pyelonephritis include diabetes mellitus, chronic urinary tract infections (UTIs), pregnancy, benign prostatic hyperplasia, fecal incontinence, older age, immobility, and use of urinary catheters.2,5
Signs and symptoms of pyelonephritis can vary from mild to severe. Often, patients report that they've “strained their back.” Other common signs and symptoms include fever, chills, dysuria, urinary urgency and frequency, hematuria, nausea, vomiting, anorexia, costovertebral angle tenderness, and suprapubic and/or flank pain. Older adults may present with confusion or malaise. Signs and symptoms that indicate a need to seek immediate care are a change in level of consciousness, fever above 101° F (38° C), severe pain, or vomiting.2
Making a diagnosis
Lab studies for pyelonephritis include a urinalysis and urine culture and sensitivity, complete blood cell count, and possibly blood cultures. The presence of white cell casts, protein, red blood cells, and bacteria in the urine indicates acute pyelonephritis.2,6 In chronic pyelonephritis, bacteria may be absent with higher levels of protein in the urine.6 A positive leukocyte esterase (an enzyme released by bacteria) indicates pyuria, and a positive nitrite indicates infection with Enterobacteriaceae.2,6 Imaging studies such as computed tomography (CT), magnetic resonance (MR) imaging, ultrasound, or CT/MR urography may be performed if recurrent infections exist or if the patient has persistent signs and symptoms despite treatment in order to rule out genitourinary abnormalities.3
Microorganisms that commonly cause pyelonephritis include Escherichia coli (75% to 90% of cases), Staphylococcus saprophyticus, Enterobacteriaceae, Proteus mirabilis, Klebsiella pneumoniae, or Pseudomonas aeruginosa.2,7 Patients can be treated with oral antibiotics if signs and symptoms don't require hospital admission.
If patients experience no improvement in signs and symptoms within 1 to 2 days of therapy or they develop complications, hospital admission and I.V. antibiotics may be indicated. Length of antibiotic therapy can range from 5 to 14 days, though longer therapy may be indicated in some circumstances, such as the presence of a renal abscess.4,8,9 Antibiotics can be given empirically using a broad-spectrum drug such as ciprofloxacin; therapy is then adjusted based on the organism identified by culture and sensitivity results.9 Antipyretics, antiemetics, pain management, increased fluid intake, and rest are also key components of treatment. Treating structural abnormalities and lower UTIs is important to help prevent recurrence.
Advise patients to drink plenty of fluids, urinate as soon as they have the urge, empty the bladder completely before bed, promptly report signs and symptoms of UTI or pyelonephritis, and complete the course of antibiotic therapy as prescribed. Women should perform perineal care daily and before and after intercourse, and drink cranberry juice daily to increase urine acidity, which helps prevent infection.2,10
1. Porth CM. Essentials of Pathophysiology
. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2010.
3. Abraham G, Reddy YN, George G. Diagnosis of acute pyelonephritis with recent trends in management. Nephrol Dial Transplant
6. Brunzel NA.Fundamentals of Urine and Body Fluid Analysis
. 2nd ed. Philadelphia, PA: Saunders; 2004.
7. Hooton TM, Gupta K. Acute uncomplicated cystitis and pyelonephritis in women. UpToDate. 2013. http://www.uptodate.com
9. Gupta K, Hooton TM, Naber KG, et al. International clinical practice guidelines for the treatment of acute uncomplicated cystitis and pyelonephritis in women: a 2010 update by the Infectious Diseases Society of America and the European Society for Microbiology and Infectious Diseases. Clin Infect Dis