Pyelonephritis Flashcards
What is pyelonephritis?
Infection of the renal pelvis and parenchyma associated with an ascending bacterial infection of the bladder
What is the aetiology of pyelonephritis?
Usually caused by an ascending bacterial infection of the bladder
Less commonly due to hematogenous spread of infection to the kidney
Pathogens - gram positive and negative bacteria
What are they risk factors?
Most common in women due to shorter urethras
UTI’s
Cystitis
Recent administration of antibiotics (possible antibiotic resistance)
Immunosuppression
Renal transplant
What are the classifications?
Uncomplicated pyelonephritis - in an immunocompetent, non pregnant female with normal genitourinary anatomy and renal function
Complicated pyelonephritis - associated with any of the following risk factors - Failure of outpatient therapy
Sepsis
Male sex
Age > 60 years
Urinary tract abnormalities (e.g., obstruction, indwelling catheter)
History of surgery to the urinary tract or kidneys
Hospital-acquired infection
Renal impairment
History of nephrolithiasis
Immunosuppression and/or severe comorbidities (e.g., diabetes mellitus, chronic corticosteroid use)
Pregnancy
What are the clinical features?
Fever
Chills
Flank pain
Costovertebral angle tenderness: pain upon percussion of the flank (usually unilateral, may be bilateral)
Dysuria as well as other symptoms of cystitis (e.g., frequency, urgency)
Weakness, nausea, vomiting (diarrhea may also be present)
Possible abdominal or pelvic pain
What are the lab tests?
Urinalysis [6]
Nonspecific findings of UTI
Pyuria (positive esterase on dipstick test)
Leukocyturia (WBCs > 5/hpf)
Bacteriuria
Positive nitrites on dipstick test indicate bacteria that convert nitrates to nitrites. [9]
Hematuria (including microhematuria)
Other findings
WBC casts: rare finding, but considered to be a strong indicator for pyelonephritis [6][10]
Urine pH of ≥ 7.5–8.0: associated with urease-producing organisms [1][11][12]
Epithelial cells > 5/hpf: suggests contamination.
Gram stain: direct visualization of bacteria (seldom performed)
Urine culture with susceptibilities
Perform in all patients with suspected pyelonephritis to determine the pathogen and any associated drug resistance.
≥ 105 colony-forming units/mL suggests bacterial infection (See “Urine culture” for more details.) [13][14]
Blood cultures (2 sets): should be performed in all patients with suspected complicated pyelonephritis
Urine pregnancy test in women of childbearing age
Additional blood tests
CBC: leukocytosis
Inflammatory markers: ↑ CRP, ESR
BMP: may be normal or show elevated BUN and creatinine
Which imaging studies are done? And what are the indications and findings?
Indications - not routinely indicated in patients with suspected acute uncomplicated pyelonephritis
Imaging serves to identify obstruction, abscess or emphysematous pyelonephritis
Consider in the following conditions - Complicated pyelonephritis
Sepsis or septic shock
Known or suspected nephrolithiasis [16]
New decline in eGFR to < 40
Recurrent pyelonephritis [5]
No response to therapy within 2 days
What are the findings on a CT abdomen with and without iV contrast
Findings supportive of pyelonephritis - renal parenchyma may appears normal or edematous
Infected parenchyma may be visible as wedge shaped areas of streaky contrast enhancement
Findings supportive of urinary tract obstruction - hydroureter, hydronephrosis, nephrolithiasis, urolithiasis
Other findings that may be present - congenital abnormalities off the renal tract, abscess, haemorrhage in the parenchyma
What are the findings of an ultrasound of kidneys and bladder? And indication
Indication - patients with contraindication to CT scan eg allergy to contrast
Findings supportive of pyelonephritis - renal enlargement, loss of corticomedullary differentiation, oedema, haemorrhage in tghe parenchyma, abscess
Findings supportive of urinary tract obstruction - hydroureter, hydronephrosis, thickened bladder wall, high bladder residual volume, prostate enlargement
What is the treatment for uncomplicated and complicated pyelonephritis?
Uncomplicated - empiric antibiotic therapy - most patients treated with oral fluoroquinolone for 5-7 days
Alternatives - trimeothprim-sulfamethoxazole for 10-14 days
Amoxicillin-calvulanate for 10-14 days
Cefpodoxime for 10-14 days
Can consider a single dose of broad spectrum parenteral antibiotic priory to administration of oral antibiotics eg ceftriaxone or gentamicin
Supportive therapy - drink plenty of fluids
For complicated pyelonephritis - admitted to hospital and started on parenteral empiric antibiotic therapy ASAP.
If patient is not severely ill and no risk factors for multi drug resistant bacterial infection - can give a fluorquinolone or an extended spectrum cephalosporin, or an extended spectrum penicillin with a beta lactamase inhibitor, consider adding an amniglycoside until culture results are available
If patient is severely ill and or with risk factors for multi drug resistant gram negative bacterial infection - can. Give a carbapenem, or an extended spectrum penicillin with a beta lactamase inhibitor, or aztreonam, or an extended spectrum cephalosporin, and consider giving an aminoglycoside until culture results are available
If the patient is suspected with enterococcus or MRSA - consider adding vancomycin, or if there is a concern for VRE, add one of the following: adptomycin, linezolid
Supportive therapy - analgesics, antiemetics
Additional considerations - aggressive IV resuscitation for patients with sepsis
Subsequent management - duration of antibiotic therapy - 10-14 days
What are the complications of pyelonephritis?
Urosepsis, septic shock
Perinephric abscess, renal abscess
Renal papillary necrosis
Emphysematous pyelonephritis
Recurrent bacterial infection
Atrophic kidneys
End stage renal disease
What is chronic pyelnonephritis?
A consequence of redcurrant or persistent acute pyelonephritis
What are the clinical features of chronic pyelonephritis?
Non specific eg fever, anorexia, malaise
Abdomina or flank pain
What is the diagnosis for chronic pyelonephritis?
Urinalysis - pyuria, proteinuria, WBC casts
Imaging - corticomedullary scarring, blunt/clubbed renal calyces
Biopsy - thyroidization of the kidney
What is the treatment for chronic pyelonephritis?
Treat underlying cause
Antibiotics
