inflammatory diseases Flashcards
What are the two main groups of renal infection?
1 - glomerulonephritis - immunologic injury to the glomerulus
2 - interstitial nephritis - infection/toxic injury to renal parenchyma
What bug is most common in UTI?
E coli, due to p fimbriae protein that allows the bug to climb the urinary tract
What is the sex predilection for UTI?
50, male (stasis due to BPH)
Which population is at higher risk for complications of renal infections?
Diabetics
What is the pathophysiology of pyelonephritis? How do chronic abscess form?
Infiltration of the interstitium with PMN resulting in swelling. Can coalesce to form microabscesses
If small microabscesses coalesce, liquefaction can occur and form an abscess, with fibroblast migration to this area that forms a wall, resulting in chronic abscess.
If incomplete wall formation, a perinephric abscess can occur as the infection can spread past the capsule
What is pyonephrosis?
Infection confined to the collecting system with ureteral obstruction.
Collecting system is filled with pus, can have inflammatory changes in the renal parenchyma
What nm test is used in kids to detect renal parenchymal infection?
Tc99m DMSA
What percentage of uncomplicated pyelonephritis cases are normal on imaging?
75%
What are the imaging features of acute pyelonephritis?
ct
us
1 - Diffuse enlargement, due to enlargement, focal bulge in renal contour
2- delayed enhancement of collecting system
3 - attenuation of renal collecting system due to edema
4 - decrease in density of nephrogram in affected kidney
5 - wedge shaped striated enhancement of parenchyma
6 - perinephric fat stranding
US - normal or diffuse hypoechoic parenchyma
US - can have focal pyelonephritis with poorly marginated sonolucent mass, lowlevel echoes that disrupt corticomedullary junction
Decrease in power doppler flow
How does partially treated pyelonephritis appear on CT?
Rounded or ovioid area of decreased enhancement with poorly defined margins, more masslike with homogeneous hypoattenuation/enhancement
What is the flare pattern on nm scan?
Striate distribution of decreased radioactivity
What is the disadvantage of using gallium for pyelonephritis?
Normally excreted by kidney in 24 hours
Cant differentiate between kidney and perinephric stranding
How does an acute pyelonephritis appear on US? CT?
US - sonolucent lesion with low amplitude echoes reflecting necrosis. Poor through transmission. “Complex mass”
CT - low attenuation (10-20HU) round/ovioid mass without enhancement (Walled off). Borders are indistinct due to surrounding inflammation. +/- gas, can have perinephric inflammation too
How does a chronic pyelonephritis abscess appear?
Hypoattenuation core with hypervascular rim on CT.
How does a perinephric abscess form?
1 - intrarenal anscess breaks through the capsule
2 - obstruction with urine extravasation
3 - direct extension from adjacent infection
What are the risk factors for perinephric abscesses?
Staghorn calculi
Pyonephrosis
Diabetes
Neurogenic bladder
How do perinephric abscesses appear on US?CT?
US - masses of variable echogenicity with gas (dirty shadowing)
CT - loculated fluid collection with rim enhancement adjacent to kidney
What are the imaging findings in pyonephrosis?
XR - urinary tract calculi
US - dependent echoes, shifting urine debris levels, dense peripheral echoes with shadowing secondary to gas, low level echoes within the dilated collecting system with poor through transmission
CT - grossly dilated collecting system with urine debris level or air fluid level. Will have hydronephrosis. Can have layering of contrast material above purulent material
What patients/bugs are prone to emphysematous pyelonephritis?
E coli, klebsiella, aerobacter, proteus
Diabetics
Extension of gas into the perirenal space is important why?
Increased mortality than with gas confined to parenchyma
Good survival with nephrectomy
What is emphysematous pyelitis?
Gas within the lumen of the renal pelvis or calyces with/without pyelogram or gas within the walls of the renal pelvis
Describe
Emphysematous pyelonephritis
Renal abscess
Emphysematous pyelitis
Air infiltrating renal parenchyma
Focal parenchymal air collection with fluid
Air in the walls of the renal pelvis or calyces
What is the difference between emphysematous pyelonephritis and pyelitis?
Pyelonephritis - gas within the parenchyma, poor prognosis
Pyelitis - gas within the collecting system, benign, better prognosis
Where is the most common renal fistula formed?
Colon
What is xanthogranulomatous pyelonephritis?
Presence of lipid laden macrophages (xanthoma cells), and other inflammatory cells (plasma, leukocytes, histiocytes)
Usually staghorn calculus
Is there a sex predominance in XGP?
FEmale 4:1
What are the features of XGP?
Indolent process, rarely fulminant
Nonfunctiong kidney
Female predominance
What are the two types of XGP?
Diffuse involvement or focal infection (tumefactive, can simulate mass)
What is the imaging in XGP?
US - diffuse renal enlargement with central echogenic focus representing stone. Dissue anechoic parenchyma due to inflammation/abscess, calyceal fluid may simulate pyonephrosis
CT - enlarged kidney with poorly defined pelvis. Calculi usually present. High density peripheral areas representing atrophic parenchyma with inflamed columns of bertin
Enhanced scan shows hyperemia at the periphery, around the calyces and into the renal fascia
Tumefactive may simulate a localized water density mass with calculus
What is malacoplakia?
Granulomatous renal inflammation with presence of distinct histiocytes with basophilic stained inclusion bodies (Michaelis Gutmann bodies) - represent phagocytozed bacterial fragments
Due to enzymatic defect in histiocytes that result in fragmented phagocytaion of bacteria
What are the two types of malacoplakia? Which sex gets it more?
Female
Multifocal
Unifocal - masslike
What are the imaging features of malacoplakia?
Multifocal - diffuse enlargement, diminished excretion of contrast enhancement, secondary to extensive renal replacement
US - can have multiple soft tissue masses with less enhancement than normal parenchyma
Can extend to retroperitoneum
Rarely diagnosed preoperatively as it simulates masses and or pyelonephritis
How does most chronic atrophic pyelonephritis and scarring occur?
Due to papillary anatomy, especially at the poles with compound calyceal opening being more circular and prone to reflux.
What is the characteristic appearance of intrarenal reflux scarring?
Extends entire thickness of renal parenchyma and associated with deformity of the calyx adjacent tot eh scar
Scar with compensatory hypertrophy of the adjacent normal tissue
US- focal parenchymal loss with hyperechoic scar
Who gets reflux scarring most commonly?
Kids, usually
How does TB affect the kidney (route)
Hematogenous spread with bacterial lodging in the corticomedullary junction
Usually bilateral due to hematogenous spread
The lesions spread along nephron and rupture into pelvocalyceal system
What are the classic findings of renal TB
Parenchymal calcification Parenchymal scars Papillary necrosis Infundibular structures Autonephrectomy
What are the appearances of the following with TB
Papilla
Parenchyma
Calyces
Papilla - ends will have moth eaten irregular appearance. Extensive papillary necrosis develops with formation of frank cavities
Parenchyma - amorphous granular calcification with granulomatous masses, or dense punctate calcification with healed tuberculomas. Can scar as well.
Calyceal - multiple irregular infundibular stenoses or strictures with subsequent hydrocalycosis. “Large calyces with stenosed pelvis and ureter”.
What is a putty kidney?
Dystrophic calcification within the renal parenchyma seen in TB
What is the US appearance of renal TB?
Dilated renal calyces without hydropelvis
What is the most common fungal agent in renal infection?
Candida
What is the pattern of involvement of candida in the kidney?
Bacteria lodge in the distal tubule, causing multiple medullary and cortical abscesses, leading to acute fungal pyelonephritis.
Fungal involvement of the renal papilla leads to papillary necrosis, which then extrudes into the collecting system leading to mycetoma formation.
What is the characteristic finding of candida on imaging?
Demonstration of multiple filling defects 1-4cm within the collecting system representing fungus balls
Also get scalloping of the ureters due to submucosal edema
US - multiple nonshadowing fungus balls in dilated calyces
What are the findings with infection by
Coccidiomycosis
Cryptococcus
Brucellosis
Actinomycosis
Coccidio - papillary necrosis, cavitation, parenchymal calcification
Crypto - cavitation, papillary necrosis, multiple parenchymal abscesses
B - extensive calcification, cavitation, and infundibular strictures
A - usually through GI fistula. Acute pyelonephritis, pyonephrosis, granulomatous renal abscess
Who gets brucellosis
Meat packers, unpasteurized milk
What is the renal appearance of hydatid disease?
3 layered hydatid cyst that rapidly grows and destroy the kidney parenchyma, or can be indolent
Daugher cysts form within the mother cyst
Well defined ST mass in renal fossa with curvilinear calcification
Crescent sign - distortion of renal pelvis or calyces
What is the crescent sign?
Hydatid disease results in distortion of the renal pelvis or calyces
What is the bunch of grapes sign?
Filling of daugther cysts in connection with pelvis
What is the falling snowflake sign
Movement of internal echoes within the hydatid cyst (“sand”, hooks, scolices, brood capsules) when patient moves
Which type of AIDS (sex vs IDVA) has more renal symptoms
IVDA
What is the renal appearance of pneumocystis carinii involvement
Multiple punctate calcifications
Can be seen in MAI and CMV as well
Calcification is seen only in the active forms of what diseases? when is it seen in both active and inactive disease?
TB, candidiasis
Pneumocystis, CMV, MAI
