Urinary Tract Flashcards
(31 cards)
USF of nephrolithiasis
Medullary nephrocalcinosis:
• Cortical nephrocalcinosis: 95% 5% • Earliest sign of medullary nephrocalcinosis: of hypoechoic papillary structures
• Solitary focus of hyperechogenicity near fornix at tip of pyramid
• Hyperechoic rim at corticomedullary junction and along periphery of pyramids
• Generalized increased echogenicity of renal pyramids +/- shadowing
Checklist for nephrolithiasis
Focal areas of dystrophic calcification in masses or infection are not considered nephrocalcinosis
USF of urolithiasis
Calculi seen as crescent-shaped echogenic foci with sharp distal acoustic shadowing
• Calculi best visualized in kidney and at UV]
• Stone in ureter visualized if ureter is dilated
• Stones in non-dilated ureter poorly visualized due to overlying bowel gas and deep location
• Most urinary tract stones show twinkling artifacts: Useful ancillary finding in equivocal cases
• Ureteric jet: visualization of “jet” of urine into bladder excludes obstructing distal stone
• Resistive index> 0.7 in symptomatic kidney
Checklist for urolithiasis
Use tissue harmonics to enhance posterior acoustic shadowing if small calculi suspected
• CT more sensitive for calculi in course of ureter with perinephric stranding ± hydronephrosis
USF of hydronephrosis
Best diagnostic clue: Dilated renal pelvis communicating with anechoic fluid-filled calyces
• Mild hydronephrosis: Small separation of calyceal pattern (splaying), normal bright sinus echoes, normal parenchymal thickness
• Moderate hydronephrosis: Ballooning of major and minor calyces, diminished sinus echoes, normal or thinned parenchymal thickness
• Fetal renal pelvis diameter ~ 8 mm at 20-30 week or ~ 10 mm beyond 30 week gestation requires post natal follow-up
Checklist for hydronephrosis
Complicated by spontaneous urinary extravasation from forniceal/pelvic tear if acute obstruction
• Superimposed infection, calculus formation if chronic obstruction
• Parenchymal atrophy if chronic obstruction, leading to renal impairment
USF of simple renal cyst
Typically appears as anechoic, unilocular, thin-walled, round/oval renal lesion
• Adjacent blood vessels seen to be displaced
• Best imaging tool: Ultrasound is ideal for characterizing simple or complex renal cysts
• Has good sound transmission giving rise to characteristic distal acoustic enhancement
• Has no internal echoes, septum or solid component
• Small cysts « 3 mm in diameter) may appear as echo-free lesions without posterior acoustic enhancement
• US is more accurate than CT in demonstrating internal cyst morphology
• If multiple simple cysts are found, it is important to rule out polycystic kidney disease
• Lack of intracystic color signal
Checklist for simple renal cysts
Anechoic intra cystic content with good through transmission, no internal septation
• Always distinguish simple renal cyst from other complex cystic renal lesions
USF of complex renal cysts
Best diagnostic clue: Fluid-filled renal lesion shows either calcification, septations, turbid internal content, internal nodules, vascularity, or wall thickening
• Infected cyst: Thick wall with scattered internal echoes ± debris-fluid level representing pus
• Hydatid cyst: Simple; multiloculated with endocyst and membranes; calcified or solid (chronic)
• Hemorrhagic cyst: Appearance varies with age of blood
• Proteinaceous cysts: May contain low level echoes, with bright reflectors or even layers of echoes
• Calcified cyst: Wall or septal calcification ± shadowing
Milk-of-calcium cyst: “Comet-tail” artifact + line of calcium debris
• Neoplastic wall: Tumor nodule or wall thickening
• Cystic RCC: Thick septa, septal or peripheral calcification, wall or septal nodularity
• Localized cystic disease: Conglomerate of simple cysts simulating multiloculated cystic mass
• Cyst vascularity greatly t risk of malignancy
• Contrast-enhanced ultrasound + harmonic imaging: t Sensitivity and useful in characterizing complex renal cysts
Checklist for complex renal cyst
Consider CHECKLIST
• Imaging generally more reliable than clinical correlation
Image Interpretation Pearls
• Image evaluation and classification of cystic masses is key to management
USF findings of urolithiasis
Calculi seen as crescent-shaped echogenic foci with sharp distal acoustic shadowing • Calculi best visualized in kidney and at UV] • Stone in ureter visualized if ureter is dilated • Stones in non-dilated ureter poorly visualized due to overlying bowel gas and deep location
• Most urinary tract stones show twinkling artifacts: Useful ancillary finding in equivocal cases
• Ureteric jet: visualization of “jet” of urine into bladder excludes obstructing distal stone
• Resistive index> 0.7 in symptomatic kidney
Checklist for urolithiasis
Use tissue harmonics to enhance posterior acoustic shadowing if small calculi suspected
• CT more sensitive for calculi in course of ureter with perinephric stranding ± hydronephrosis
USF of renal papillary necrosis
Best diagnostic clue: Echogenic papilla with ring calcification, surrounded by fluid in medulla
• Ultrasound: Insensitive for early necrotic changes
• Apparent pelvicaliceal dilatation
• Echogenic “rings” in medulla (necrotic papillae)
• Rim of fluid around necrotic papillae
• Single/multiple cystic cavities in medullary pyramids continuous with calyces ± calcification
Sloughed papillae appear as echogenic lesions in collecting system simulating calculi
• Hydronephrosis is a common association
Checklist for renal papillary necrosis
Echogenic “rings” in medullary pyramids ± obstruction
USF of perinephric fluid collections
Appearance depends on nature of fluid collection
• Urinoma usually localized, well-defined, thin-walled, anechoic with no septations
• Hematoma: Sonographic features vary with time
• Acute hematoma: Echogenic internal echoes
• Hematoma may become anechoic or cystic containing low level echoes ± septations
• Hematoma may resemble urinoma or abscess depending on stage of formation or liquefaction
• Subcapsular hematoma may mimic or mask neoplasms
• Abscess: Depicted as hypoechoic or nearly anechoic mass displacing kidney ± fluid-debris level and thick irregular wall
• Echogenicity of abscesses t if gas-containing
Lymphocele: Well-defined, anechoic ± septations
• Pancreatic pseudocyst: Well-defined, loculated, anechoic ± debris-fluid level, depicted as complex masses if hemorrhagic or infected
• Ultrasound: Sensitive to reveal perinephric fluid collections but nonspecific to characterize them
• Color Doppler: May be helpful to identify soft tissue component in subcapsular hematoma due to tumor rupture; arteriovenous fistula in bleeding angiomyolipoma
• Ultrasound is initial investigation for perinephric fluid collection and guided aspiration
Checklist for perinephric fluid collections
Must identify underlying etiology in spontaneous perinephric hematoma to exclude malignancy
Image Interpretation Pearls
• Ultrasound along with clinical characteristics may facilitate specific diagnosis and treatment
USF of pyelonephritis
Best diagnostic clue: Renal enlargement with thickened urothelium and microabscesses
• Normal or swollen kidney &~renal echogenicity
• Loss of corticomedullary (CM) differentiation effacement of sinus echoes
• Thickened renal pelvic urothelium
Microabscesses or areas of necrosis
• Power Doppler: May show ~renal vascularity or vascular defect due to vasoconstriction
• Protocol advice: Initial investigation by ultrasound followed by CT for delineation of complicatio
Checklist for pyelonephritis
Swollen kidney & poor CM differentiation & sinus echoes effacement ~ usually AP
USF of UT TB
Best diagnostic clue: Calcification, cavities and strictures in urinary tract (UT)
• Appearance is non-specific and variable
• Useful to demonstrate non-excreting kidney on IVP
• Useful to reveal extrarenal spread to adnexa in females and testes in males
• May detect intra-abdominal lymphadenopathy
• Early: Normal kidney or small focal cortical lesions with poorly defined border ± calcification
• Progressive
• Papillary destruction with echogenic masses near calyces
• Distorted renal parenchyma
• Irregular hypoechoic masses connecting to collecting system; no renal pelvic dilatation
Mucosal thickening ± ureteric and bladder involvement •
Small, fibrotic thick-walled bladder
• Echogenic foci or calcification (granulomas) in bladder wall near ureteric orifice
• Localized or generalized pyonephrosis
• Late
• Small, shrunken kidney, “paper-thin” cortex & dense dystrophic calcification in collecting system
• May resemble chronic renal disease
• USunable to evaluate renal function
Checklist for UT TB
TB if concurrent multiple abnormalities exist in UT
• Chest radiography to look for primary TB focus
• Biopsy of lesions, urinalysis & culture
Image Interpretation Pearls
• Abnormalities in multiple sites: Renal parenchymal mass/cavitation ± hydro calices/hydronephrosis calcifications ± small and thick-walled bladder
USG of renal cell carcinoma
Variable appearance: Solid, cystic or complex
• Hyperechoic (48°/il), isoechoic (42%), or hypoechoic (10%)
• Most common appearance: Hyperechoic and vascular
• Small tumors are usually hyperechoic; simulate AML
• Large tumors tend to be hypoechoic, exophytic with anechoic necrotic areas
• Hypoechoic rim resembling “pseudocapsule”
• Papillary RCC: Unilocular, often hypoechoic; calcification common (30%)
• Cystic RCC: Unilocular; hypoechoic mass with fluid-debris levels (hemorrhage and necrosis) + thick and irregular wall
• Cystic RCC: Multilocular; multiple thick septations with nodules ± calcification
Calcifications may be detected (6-20%)
• Discernible tumor vascularity; most prominent around tumor periphery
• RVthrombosis (23%) and rvc tumor extension (7%)
• May show high velocity signal from AVF
• USideal for screening RCC and surveillance of tumor recurrence after nephrectomy
Checklist for RCC
Rule out RCC in all solid renal lesions
• Hyperechoic renal lesions with calcifications and hypoechoic rim => RCC
USF for renal mets
Usually small and round, occasionally wedge-shaped mimicking infarction
• Usually intraparenchymal; contour or capsule rarely disrupts renal
• May be isoechoic, hypo echoic or hyperechoic
• Majority are hypo echoic
• Perinephric hemorrhage may be seen in melanoma
• Insensitive to detect small metastatic lesions
Mostly avascular or hypovascular
• Melanoma metastasis: Hypervascular; may stimulate renal cell carcinoma (RCC)
Diagnostic checklist for renal mets
Renal metastasis in presence of extrarenal primary cancer and widespread systemic metastasis
• Biopsy for suspected lesions
