Diagnostic Ultrasound - Abdomen and Pelvis

Acute Pyelonephritis
Diagnoses: Urinary Tract
Gross Pathologic & Surgical Features
• Polar abscesses: Microabscesses on renal surface
• Narrowed calyces and enlarged kidney
Microscopic Features
• Mononuclear cell infiltrate and fibrosis
○ Accumulated neutrophils in tubules can coalesce and be
passed in urine as casts
• Interstitial or tubular necrosis
CLINICAL ISSUES
Presentation
• Most common signs/symptoms
○ Fever, malaise, dysuria, flank pain, and tenderness are
typical
– Young children may have nonspecific symptoms:
Fussiness and poor feeding
– Elderly patients may present with mental status
changes or failure to thrive
• Lab data
○ Serum: ↑ ESR, ↑ WBC, ↑ proteinuria
○ Urine: ↑ WBC, WBC casts, proteinuria, positive urine
culture for bacilli
– Remember: Especially in children, absence of lower
UTI does not exclude AP
Demographics
• Age
○ Common in adults (also seen in children)
• Gender
○ F > M
• Epidemiology
○ ↑ incidence: M > 65 years, F < 40 years
○ Pregnant women are at increased risk for upper UTI due
to hormonal changes affecting ureteral peristalsis and
gravid uterus causing ureteral compression
○ Diabetic patients are at increased risk for upper and
lower UTI
Natural History & Prognosis
• Good
○ Potential complications
– Abscess formation
– Renal vein thrombosis
– Pyonephrosis
– Cortical scarring
○ Rare complications, more common in patients with
diabetes mellitus
– Papillary necrosis
– Emphysematous pyelonephritis
Treatment
• Acute: Antibiotic therapy
Image Interpretation Pearls
• Pyelonephritis usually asymmetric
• Sonographic changes may be subtle in acute setting
SELECTED REFERENCES
1. Lee YJ et al: Unilateral and bilateral acute pyelonephritis: differences in
clinical presentation, progress and outcome. Postgrad Med J. 90(1060):80-5,
2014
2. Faletti R et al: Diffusion-weighted imaging and apparent diffusion coefficient
values versus contrast-enhanced MR imaging in the identification and
characterisation of acute pyelonephritis. Eur Radiol. 23(12):3501-8, 2013
3. Fontanilla T et al: Acute complicated pyelonephritis: contrast-enhanced
ultrasound. Abdom Imaging. 37(4):639-46, 2012
4. Ifergan J et al: Imaging in upper urinary tract infections. Diagn Interv
Imaging. 93(6):509-19, 2012
5. Chen KC et al: The role of emergency ultrasound for evaluating acute
pyelonephritis in the ED. Am J Emerg Med. 29(7):721-4, 2011
6. Cavorsi K et al: Acute pyelonephritis. Ultrasound Q. 26(2):103-5, 2010
7. Dell'Atti L et al: Clinical use of ultrasonography associated with color Doppler
in the diagnosis and follow-up of acute pyelonephritis. Arch Ital Urol Androl.
82(4):217-20, 2010
8. Craig WD et al: Pyelonephritis: radiologic-pathologic review. Radiographics.
28(1):255-77; quiz 327-8, 2008
9. Demertzis J et al: State of the art: imaging of renal infections. Emerg Radiol.
14(1):13-22, 2007
10. Browne RF et al: Imaging of urinary tract infection in the adult. Eur Radiol. 14
Suppl 3:E168-83, 2004
11. Dacher JN et al: Power Doppler sonographic pattern of acute pyelonephritis
in children: comparison with CT. AJR Am J Roentgenol. 166(6):1451-5, 1996
12. Talner LB et al: Acute pyelonephritis: can we agree on terminology?
Radiology. 192(2):297-305, 1994
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DIAGNOSTIC CHECKLIST
Consider
• Focused US evaluation for ureteral stones if pyelonephritis
is suspected, including transvaginal images for distal ureter
stones
○ Presence of stones alters management