PYELONEPHRITIS, CHRONIC

The 5 Minute Urology Consult 3rd Ed.

Debra L. Fromer, MD

Drew A. Freilich, MD

BASICS

DESCRIPTION

• Injury to the kidney with inflammation and fibrosis of the renal parenchyma, pelvis, and calyces. It is most often caused by recurrent or chronic renal infection

• Not usually diagnosed based on clinical presentation, chronic pyelonephritis is usually a radiologic or pathologic diagnosis

• Clinical signs and symptoms are often vague but can be related to the infection and the severity and location of injury within the kidney:

– Often an incidental finding, it may present as asymptomatic bacteriuria, dysuria and frequency (lower urinary tract symptoms), vague complaints of flank or abdominal discomfort, and intermittent low-grade fevers.

– Synonym(s): Chronic interstitial nephritis

EPIDEMIOLOGY

Incidence

• Occurs in males and females of all ages:

– More common in childhood, especially with congenital anomalies such as vesicoureteral reflux (VUR) (1)[B]

• Chronic pyelonephritis accounts for 15–20% of cases of chronic renal failure

• Less common in patients having no underlying functional or structural urinary tract abnormalities

Prevalence

4:1,000 asymptomatic adults

RISK FACTORS

• Female sex

• In 50% of cases, history of a previous episode of acute pyelonephritis

• VUR/reflux nephropathy

• Congenital urinary tract anomalies

• Neurogenic bladder dysfunction

• Pregnancy

• Urinary tract obstruction with complicated UTI can result in renal insufficiency:

– Mechanical obstruction includes prostatic hyperplasia, calculi, retroperitoneal fibrosis, neoplasms, and congenital anomalies

Genetics

Susceptibility to acute pyelonephritis may have a familial component and may be associated with decreased CXCR1 expression.

PATHOPHYSIOLOGY

• Progressive localized immune response to bacterial infection

• Hyaline casts in tubule may cause resemblance to thyroid colloid known as renal thyroidization

• Fibrosis around the glomeruli replaces kidney parenchyma in patches:

– Calyceal clubbing with nonuniform localized scarring

ASSOCIATED CONDITIONS

• VUR

• Spinal cord injury

• Xanthogranulomatous pyelonephritis (XGP) is a form of chronic pyelonephritis

– Presents with foamy lipid laden macrophages

– Often unilateral and associated with longstanding obstructing nephrolithiasis

GENERAL PREVENTION

• Upper urinary tract evaluation in patients with recurrent bacteriuria or recurrent acute pyelonephritis

• Early detection, evaluation, and treatment of childhood UTIs

• Prompt detection and management of VUR

• Detection and treatment of obstructive uropathy

Geriatric Considerations

• Chronic pyelonephritis can present with atypical symptoms and signs (ie, failure to thrive, low-grade fevers). Diagnosis requires a high level of suspicion.

Pregnancy Considerations

• Antibiotic prophylaxis during pregnancy in patients with risk factors including:

– History of acute pyelonephritis during pregnancy

– Recurrent bacteriuria after treatment during pregnancy

– History of recurrent UTIs on previous antibiotic prophylaxis before being pregnant

Pediatric Considerations

• Assess UTI with:

– Voiding cystourethrogram (VCUG) (to check for VUR or anatomical abnormality)

– DMSA (to detect scar formation/progression)

– Renal US (to assess for hydronephrosis)

DIAGNOSIS

HISTORY

• Frequently asymptomatic and discovered incidentally

• UTIs in childhood and during pregnancy

• Presence of HTN, especially in children with known reflux nephropathy

• Proteinuria, polyuria, nocturia, frequency

• Patients with spinal cord injury present with cloudy or malodorous urine, vague abdominal discomfort, malaise, lethargy, leakage between catheterizations, or increased spasticity or autonomic dysreflexia.

• Fever of unknown origin

• Failure to thrive in infant or child

PHYSICAL EXAM

• HTN may be present

• Nonspecific, unless associated with an episode of acute pyelonephritis

• May be mild flank pain or CVA tenderness

DIAGNOSTIC TESTS & INTERPRETATION

Lab

• Urinalysis may be normal or indicate pyuria or proteinuria. WBC casts can be seen.

• Urine culture is usually only positive with an active, symptomatic infection. Culture is often negative.

• Microalbuminuria/proteinuria is an adverse prognostic sign.

Imaging

• CT reveals the typical findings of chronic pyelonephritis

– Small or atrophic kidney, unilaterally or bilaterally

– Compensatory hypertrophy with unilateral atrophy

– Blunted and dilated calyces

– Renal cortical scarring and thinning of the cortex

• Renal US to evaluate for hydronephrosis, renal anatomy, or stones. Not a good test to identify active reflux, but dilated ureters suggest obstruction or reflux

• VCUG for the evaluation of reflux

• CT is more sensitive than US for nephrolithiasis; also to rule out obstruction, hydronephrosis, stone disease, urinary tract abnormality. Pyonephrosis or abscesses are usually identified if present

• Technetium-99m DMSA is the best study to evaluate for renal scarring

Diagnostic Procedures/Surgery

• Cystoscopy in selected cases

• Renal biopsy

Pathologic Findings

• Gross kidney is often diffusely contracted, scarred at periphery with thin cortex

• Microscopically, an interstitial infiltrate of lymphocytes, plasma cells, and occasional neutrophils is present

• Scarring is often polar with underlying calyceal blunting. Histologic changes are patchy:

– Periglomerular fibrosis is often seen

– Leukocytes and hyaline casts can be present in tubules, and the hyaline casts may resemble thyroid colloid, hence the description renal thyroidization

DIFFERENTIAL DIAGNOSIS

• Analgesic nephropathy

• Diabetic nephropathy

• Gouty nephritis

• Hypertensive renal disease

• Psoas and subdiaphragmatic abscess

• Renal artery stenosis

• Renal malakoplakia

• Renal tuberculosis

• Urolithiasis

• Xanthogranulomatous pyelonephritis (XGP) (2)[B]

TREATMENT

GENERAL MEASURES

• Chronic pyelonephritis is difficult to manage as it is an irreversible process

• With mild VUR, suppressive antibiotics are used until resolution or puberty in children

• Severe reflux may require reimplantation

• Correct anatomic anomalies or stones if possible

MEDICATION

First Line

• Acute episodes of pyelonephritis should be treated (See Section I: “Pyelonephritis, Acute”) (3)[B]

• Suppressive antibiotics VUR in children has become controversial:

– In children <3–6 mo, use low-dose amoxicillin or cephalexin, cefazolin, or other 1st-generation cephalosporin can be considered

– In children >6 mo, switch to nitrofurantoin, trimethoprim-sulfamethoxazole, or trimethoprim alone can be considered

• Hypertension is best treated by ACE inhibitors (lisinopril, enalapril, ramipril) that may also protect the kidney from progressive renal failure

– ACE inhibitors are contraindicated in pregnancy

Second Line

Based upon urine culture sensitivities, prior treatment attempts and patient presenting symptoms

SURGERY/OTHER PROCEDURES

• Correction of reflux may be necessary in children with high-grade reflux (Grade 4–5). Low-grade reflux (Grade 1–3) often resolves with time

• Nephrectomy for persistent/recurrent infection unresponsive to systemic treatment, markedly decreased function (ie, 10%), pain, or refractory HTN, XGP

ADDITIONAL TREATMENT

Radiation Therapy

N/A

Additional Therapies

N/A

Complementary & Alternative Therapies

Little data to support

ONGOING CARE

PROGNOSIS

• 24-hr protein excretion may be an important prognostic indicator of progressive deterioration of renal function due to focal and segmental glomerulosclerosis superimposed on tubulointerstitial disease

• Radionuclide renal scan can assess renal function and scarring

COMPLICATIONS

• Emphysematous pyelonephritis

• End-stage renal disease (rare)

• Focal segmental glomerulosclerosis

• HTN

• Perinephric abscess: Requires surgical drainage

• Polyuria, nocturia from loss of tubular concentrating ability

• Pregnancy-related miscarriages in women with chronic reflux

• Proteinuria

• Pyonephrosis

• XGP

FOLLOW-UP

Patient Monitoring

• Annual serum creatinine to monitor chronic kidney disease

• Blood pressure monitoring (good control of BP may limit renal damage over time)

– 15% of patients with reflux nephropathy who reach adulthood have HTN

– Some advocate screening renal scan or VCUG of siblings who have reflux

• Urine analysis to monitor for proteinuria and bacteruria (4)[A]

• Selective long-term antibiotics to limit infection (5)[A]

Patient Resources

National Kidney and Urologic Diseases Information Clearinghouse (NIH). http://kidney.niddk.nih.gov/kudiseases/pubs/pyelonephritis/

REFERENCES

1. Peters C, Rushton HG. Vesicoureteral reflux associated renal damage: Congenital reflux nephropathy and acquired renal scarring. J Urol. 2010;184(1):265–273.

2. Guzzo TJ, Bivalacqua TJ, Pierorazio PM, et al. Xanthogranulomatous pyelonephritis: Presentation and management in the era of laparoscopy. BJU Int. 2009;104(9):1265–1268.

3. Rivera JA, O’Hare AM, Harper GM. Update on the management of chronic kidney disease. Am Fam Physician. 2012;86(8):749–754.

4. Nicolle LE, Bradley S, Colgan R, et al. Infectious Diseases Society of America guidelines for the diagnosis and treatment of asymptomatic bacteriuria in adults. Clin Infect Dis. 2005;40(5):643–654.

5. Dai B, Liu Y, Jia J, et al. Long-term antibiotics for the prevention of recurrent urinary tract infection in children: A systematic review and meta-analysis. Arch Dis Child. 2010;95(7):499–508.

ADDITIONAL READING

N/A

See Also (Topic, Algorithm, Media)

• Pyelonephritis, Acute

• Pyelonephritis, Chronic Image