Acute flank pain in children: Imaging considerations

Transcription

1 Acute flank pain in children: Imaging considerations Carlos J. Sivit MD Rainbow Babies and Children s Hospital Case Western Reserve School of Medicine Flank pain Results from distention of ureter or renal capsule Pain associated with inflammation not as sudden or severe as that caused by acute obstruction Pain severity usually related to acuteness of onset 1

2 Flank pain Often associated with other symptoms including fever, nausea and vomiting Association with fever requires prompt diagnosis and relief of obstruction Infection associated with obstruction causes rapid renal damage and risk for sepsis Urolithiasis Acute pyelonephritis Obstructive uropathy 2

3 Urolithiasis Urolithiasis Calcium based stones % Calcium oxalate and calcium phosphate Struvite stones % Magnesium ammonium phosphate Uric acid stones % Occur in acidic urine; dissolved with alkanization Cysteine, xanthine & protein matrix <5% 3

4 Urolithiasis Risk factors Conditions that alter urine composition Hypercalciuria, hyperoxaluria, hyperuricosuria, hypercitrauria Medical conditions Neurogenic bladder, obstructive uropathy, diabetes, hypertension Medications that crystallize urine Urolithiasis Flank pain and hematuria in most Renal colic due to ureteral obstruction Similar rates of flank pain and hematuria with and without calculi History of fever negative predictor Personal history strong predictor 4

5 Urolithiasis Role of imaging Establish diagnosis Provide information regarding stone burden and distribution Identify associated hydronephrosis Diagnose predisposing abnormalities Urolithiasis Location of calculi Ureteral 52% Renal 24% Renal & ureteral 21% Bladder 4% Persaud. Pediatrics 2009;124:888 5

6 US High sensitivity for renal (>90%) Low sensitivity for ureteral (<40%) Sonographic findings Echogenic foci within collecting system Acoustic shadowing >5 mm Color doppler twinkling artifact Hydronephrosis (indirect) LONG TRAN TRAN 6

7 Twinkling artifact Observed at color Doppler when insonating tough reflective surfaces Discrete focus of alternating colors with or without a comet tail Increases detection of stones Many false-negatives and positives Dillman. AJR 2011;259:911 7

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10 CT Unenhanced CT exam of choice High diagnostic sensitivity Low dose protocols (< 3 msv) effective since imaging high contrast lesions 10

11 CT Primary finding Visualization of stone within collecting system Attenuation value higher than surrounding soft tissue Calcium 1000 H.U.; Uric acid H.U. Exception unmineralized matrix stones & stones related to Indavir 11

12 CT Secondary findings Hydronephrosis Perinephric fat stranding Hydroureter Soft tissue rim sign Hydronephrosis 12

13 Hydroureter 13

14 Fat stranding Fluid in bridging septa of perinephric fat due to increased lymphatic pressure 14

15 Soft tissue rim sign Halo of soft tissue attenuation around calcification Represents wall of ureter Pitfall - Phleboliths Absence of soft tissue rim Comet tail sign Linear soft tissue area adjacent to calcification 15

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17 Acute Pyelonephritis Acute Pyelonephritis Infection of collecting system uroepithelium & renal interstitium Most commonly ascending infection but may be hematogenous Increased risk with obstruction or vesicoureteral reflux E. Coli responsible for >90% 17

18 Acute Pyelonephritis Role of Imaging Establish diagnosis Identify complications requiring surgical or percutaneous drainage Diagnose predisposing abnormalities US Low diagnostic sensitivity Gray scale: 25-45% Color & Power Doppler: 63-75% Sonographic findings Renal enlargement Increased or decreased echogenicity Loss of corticomedullary differentiation Decreased cortical blood flow 18

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20 LT RT LT 20

21 CT Highly sensitive for diagnosis Single or multifocal wedged- or oval-shaped peripheral lowattenuation defects Striated nephrogram Renal enlargement (diffuse) Perirenal inflammatory changes Focal 21

22 Multifocal 22

23 Striated nephrogram Enlargement 23

24 Inflammatory changes Perinephric space Perirenal fascia Urothelium 24

25 MR Similar findings as CT Increased signal intensity on contrast enhanced imaging Alternative to CT to avoid radiation exposure Ddx Segmental infarct Leukemia Lymphoma 25

26 Complications Renal abscess Pyonephrosis Renal abscess Necrotic cavity filled with pus Typically result from inadequately treated parenchymal infection Most commonly with DM, SSD or in immunocompromised children Conservative treatment if small Drainage required if large 26

27 Renal abscess Rounded low-attenuation lesion(s) that fail to enhance CT/MR Hypoechoic or anechoic thick walled mass +/- septations & debris US Air may be seen with gas forming organisms Inflammation may extend into or outside of perirenal space 27

28 Pyonephrosis Pyelonephritis + Obstruction Infection associated with obstructive uropathy Collecting system dilated (under pressure) with pus Present with urosepsis Rapid parenchymal destruction Hydronephrosis with debris +/- gas RT LT 28

29 Scarring Almost exclusively < 6 years Only at sites of acute pyelonephritis Acute pyelonephritis results in scarring in approximately 1/2 of cases Scarring begins w/in 24 hrs of infection Risk of hypertension & end stage renal disease directly linked to scarring Initial CT DMSA 8 months later 29

30 Obstructive uropathy Obstructive uropathy UPJ obstruction Ureterocele Urolithiasis 30

31 UPJ obstruction Most common urinary tract obstruction 10% of neonatal hydronephrosis Abnormal development of short segment of ureteral smooth muscle at UPJ (adynamic segment) versus extrinsic factors including bands or aberrant crossing vessels UPJ obstruction Imaging findings Dilated renal pelvis (AP diameter >10 mm) & calices Secondary cortical thinning or dysplasia may be present 31

32 1 day 9 months 2 years 32

33 Diagnosis UPJ obstruction Requires functional examination to confirm impediment in urine flow Sonography can not address functional significance of hydronephrosis Diuretic radionuclide renography with Tc-99m MAG3 current exam of choice 33

34 MAG 3 Post lasix Ureterocele Cystic dilatation of intravesical segment of distal ureter Ureteral meatal obstruction vs incomplete muscularization of distal ureter vs excessive dilatation of distal ureter Associated with duplex > single ureter 34

35 Duplex ureter with ureterocele 2 separate collecting systems Ectopic insertion of upper pole ureter below trigone, bladder neck, urethra or genital structures 35

36 Simple ureterocele Obstruction of normally positioned ureteral orifice Congenital stenosis Inflammatory stricture Balloning of proximal ureteral segment Secondary hydronephrosis 36

37 Acute flank pain in children: Imaging considerations 37