NC.com

Pyelonephritis

Acute Pyelonephritis

• Diagnosis: made clinically (not radiographically), fever + flank pain, lower urinary symptoms may (not) be present, DO NOT diagnose based on CT findings
• Complicated pyelonephritis: high fever, leukocytosis, vomiting, dehydration, sepsis, immunocompromised, male, DM
• Blood cultures: obtain in all men, or woman with systemic symptoms or risk factors
• Imaging: not required for diagnosis, can obtain renal US to assess for stones/hydronephrosis, CT warranted in patient with systemic symptoms or presumed complicated pyelonephritis, also obtain CT if persistent fever and symptoms > 72hr despite antibiotics
• Uncomplicated management: can be treated outpatient with PO antibiotics (ciprofloxacin 500mg BID or levofloxacin 750mg QD x1 wk +/- IV ceftriaxone 1g x1 or aminoglycoside x1)
• Complicated management: admit and give IV antibiotics (fluoroquinolone, aminoglycoside +/- ampicillin, cephalosporin or extended spectrum penicillin +/- aminoglycoside, carbapenem), treat with 2 weeks abx once cultures result
• "Test of cure" UCx: recommended, 10-30% will relapse after initial abx course, consider repeat 2-6wk course

Acute Focal/Multifocal Bacterial Nephritis

• Definition: infection of parenchyma creases inflammatory mass(es) without abscess, likely transition between pyelonephritis and renal abscess, approximately 1/4 patients will progress to renal abscess
• Symptoms: severe pyelonephritis symptoms, lower tract symptoms may be absent if hematogenous spread (IV drug use or cutaneous infection)
• Diagnosis: CT with contrast shows area of decreased enhancement, nephromegaly, decreased contrast uptake
• Management: obtain BCx/UCx, admit and start IV antibiotics, given antibiotics for 2+ weeks, reimage if no improvement within 72hrs to assess for abscess or obstruction
• VCUG: up to 50% have reflux, may benefit from workup after treatment of initial infection

Chronic pyelonephritis

• Diagnosis: atrophic/poorly functional kidney from prior episodes pyelonephritis, diagnosed radiographically (not clinically)
• Management: avoid UTI risk factors, control HTN
• Nephrectomy indications: normal contralateral kidney and affected kidney causing pain, symptomatic infections, or renin-mediated HTN

Emphysematous Pyelonephritis

• Definition: severe parenchymal infection with gas-forming infection
• Risk factors: diabetes + obstruction
• Mortality rate 19-43%
• Presentation: fever, vomiting, flank pain
• Diagnosis: made by demonstrating air in renal parenchyma on CT imaging
• Antibiotics: 3rd-gen cephalosporin + aminoglycoside (or carbapenem + vancomycin if concern for cephalosporin resistance)
• Management: glucose control, treat w/ drain(s) placement, consider nephrectomy only if extensive gas w/ renal destruction (25% mortality rate)
• Emphysematous pyelitis: air in collecting system only, treat with antibiotics + foley drainage (no need for stent/PCN)

Xanthogranulomatous pyelonephritis (XGP kidney)

• Definition: chronic infection destroying parenchyma, can locally extend through parenchyma and through Gerota fascia into retroperitoneum and adjacent organs
• Presentation: flank pain, fever, persistent bacteruria, anemia, 60% have a flank mass
• CT triad: present in 50-80% patients, unilateral enlargement + little/no function + large stone in renal pelvis
• Malignancy: often cannot distinguish XGP from malignancy, may require nephrectomy for confirmation
• Diagnosis:
can only be made with pathology specimen, shows accumulation of lipid-filled macrophages
• Management: usually requires nephrectomy (often difficult due to severe inflammation), imaging may underestimate degree of inflammation and adjacent organ involvement, give vaccinations prior to L side nephrectomy (in case splenectomy required), can attempt treating stones with PCNL to salvage residual function
• Antibiotic coverage: > 4wks abx prior to surgery decreases length of stay and complication risks (per Xie 2021)

Abscesses and Pyonephrosis

Renal Abscess

• Presentation: fever, chills, abdominal/flank pain, weight loss, cystitis, may have flank mass, 50% have positive blood cultures
• Risk factors: DM (50%), rUTI (65%)
• Management: if < 3-5cm (depending on reference) treat with antibiotics and observe, otherwise drain percutaneously if larger or patient is clinically unstable or immunocompromised

Perinephric and paranephric abscesses

• Perinephric abscess: abscess outside renal capsule but contained within Gerota fascia, can be caused by abscess rupture, extravasation of infected urine, or spread from another source
• Paranephric abscess: abscess outside Gerota fascia, extends from perinephric abscess or adjacent organ abscess
• Psoas abscess: presents with limping, pain on flexion and external rotation of hip
• Management: similar criteria/recommendations as for renal abscess
• Symptom course: usually have symptoms > 5 days, and remain febrile for longer than 4 days

Infected Hydronephrosis +/- Pyonephrosis

• Infected hydronephrosis: bacterial infection in a hydronephrotic kidney
• Pyonephrosis: infected of chronic hydronephrosis, leading to decreased renal function and parenchymal destruction
• Diagnosis: imaging shows hydronephrosis with abnormal fluid and fat stranding, urinalysis may not show abnormalities if completely obstructed
• Management: place stent or PCN, may require nephrectomy if symptoms do not resolve