This presentation is part of the PEER Liberia Radiology Lecture Series. This presentation provides an overview of the basics of renal ultrasound

Harris, Robert D.

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University of Massachusetts Medical School eScholarship@UMMS PEER Liberia Project UMass Medical School Collaborations in Liberia 2021-01-07 Basics of Renal Ultrasound Robert D. Harris RAD-AID Let us know how access to this document benefits you. Follow this and additional works at: https://escholarship.umassmed.edu/liberia_peer  Part of the Diagnosis Commons, Family Medicine Commons, Medical Education Commons, Nephrology Commons, and the Radiology Commons Repository Citation Harris RD. (2021). Basics of Renal Ultrasound. PEER Liberia Project. https://doi.org/10.13028/7f04-pm57. Retrieved from https://escholarship.umassmed.edu/liberia_peer/68 This material is brought to you by eScholarship@UMMS. It has been accepted for inclusion in PEER Liberia Project by an authorized administrator of eScholarship@UMMS. For more information, please contact Lisa.Palmer@umassmed.edu. Basics of Renal Ultrasound-2021Robert D Harris, MD, MPHKeck School of Medicine at USCProfessor of Clinical RadiologyRAD-AID Chapter Director, USCLos Angeles, CA 90033Why kidneys and US?• U/S primary screening modality• Renal insufficiency-can’t get contrast for CT or MRI• Most often call case-frequent exam on call- to r/o hydronephrosis• Thin pts, pediatrics, OB pts-first line imaging in developed world, go-to imaging in developing world• Radiation risk of CT-i.e., multiple exams to evaluate renal stone burdenRenal physiology• Kidneys prime function to excrete metabolic waste• Filter about 1700 liters of blood day• Generate 1-2 liters of concentrated urine• Maintain homeostasis by regulating salt/water and acid/base balance• Secrete many hormones including erythropoetin, renin, and prostaglandinsRenal embryology• 3 sets of kidneys in embryo– Pronephros-4th gestational week, rudimentary– Mesonephros-interim, between 5-9th week– Metanephros-permanent kidneys• Metanephros develops from 2 sources– Ureteric bud (ureter, pelvis, calices, collecting ducts)– Metanephric blastema – renal cortex/med/coll ducts• Kidneys form in pelvis, ascend and rotate by 9thweekPediatric kidneys – Unique Considerations• Infantile kidneys large relative to body size• More echogenic cortex (> liver) for 2-3 years• Due to more cellular cortex and large concentration of glomeruli• Pediatric renal pyramids relatively large c/w renal cortex• Fetal lobations common, usually regress with age Adult Kidneys• Normal range 9-13 cm.• Unilateral agenesis-get hypertrophy (12-15 cm)• Parenchyma– Cortex– Medulla• Echogenic or hyperechoic renal cortex: – Definition: brighter than the liver, prominent renal pyramids– High specificity (96%), PPV (67%) for abnormal renal function, low sensitivity (20%)Harmonics in kidney imagingHarmonicsFundamental imagingHarmonic imagingColor Doppler in Renal Imaging• Excellent depiction of vascularity• Useful for differentiating mild hydronephrosis from renal vesselsPower Doppler in Kidney• Advantages over color– Not angle dependent– Less sensitive to noise artifacts– Amplitude sensitive, not directional (higher sensitivity for slow flow)• Disadvantages– Susceptible to flash artifact– No info re direction or velocity of flowMedullary pyramidsMay see prominent medullary pyramids in infants, thin adults, renal transplant patientsRenal trauma due to car accidentMarch 2009Renal atrophy secondary to ischemia/traumaMarch 2009Renal atrophyOctober 2009Fetal lobation/lobulation (FL)• Normal embryologic process• May persist into adulthood• Differentiation from scarring sometimes difficult– Fetal Lobations are thin, linear, sharply defined– Small, triangular notch at cortical end– Parenchymal thinning not present• Scar-larger, irregular, often calyceal dilatation underlyingFetal lobationsRenal “pseudomasses”Fetal lobation Dromedary humpColumn or Septum of BertinHilar “ lips “Renal pseudomassOther normal variants• Junctional parenchymal defect– Mostly anterior, upper 1/3 of kidney– Seen only on longitudinal image– Oblique echogenic line, may course to sinus• Column of Bertin (or septum)– Unusually thick cortex intervening between medullary pyramids– Triangular or oval in shape vs. spherical shape of tumor– Isoechoic, isovascular on color DopplerJunctional parenchymal defectColumn of Bertin52 yo woman s/p left partial nephrectomy for oncocytomaRenal ScarAcute Renal Failure• Pre-Renal– Renal US minor role (if any)• Renal-Medical Renal Disease– U/S helpful but not essential, biopsy often performed (size important on U/S)• Post-Renal-5% of Pts. With Acute Renal Failure– U/S plays significant part in work-up– Select pts appropriately• Low-risk for obstruction: PPV of 1%• High-risk: PPV of 30%Hydronephrosis• Definition:  Distention of the kidney with urine. Due to obstruction of urine outflow (for example, by a stone blocking the ureter). • If obstruction not known, prefer term “pelvicaliectasis”-anatomic• Grades– Mild– Moderate– SevereCauses of False +/- of Hydronephrosis• False positive– Renal hilar vessels– Peripelvic cysts– Chronic vesico-ureteral reflux – Severe papillary necrosis• False negative– Acute or partial obstruction– Dehydration– Observer error in mild hydronephrosisMild Pelviectasis (Hydro)Moderate pelviectasisSevere pelviectasisTsai, J.-D. et al. Pediatrics 2006;117:139-146Echogenic Kidneys due to ARFProminent Medullary Pyramids-Cr 1.6 (eGFR ~ 40 cc/min)Renal Cysts• Most common renal lesion or “mass”• Incidence increases with age– ½ of pts > 50 y.o. have 1 or more cyst• Etiology--Epithelial overgrowth of tubules or collecting ducts• 4 simple cyst characteristics– Anechoic– Well-defined and smooth wall– Acoustic enhancement– Imperceptible wallBenign renal cystsJanuary 2008 RadioGraphics, 28, 65-79.Benign renal cysts• Doesn’t have to fit 4 criteria on all views• May have internal artifactual echoes– Role for harmonics technique in Ultrasound• May have limited # thin septations– 5% of benign cysts have thin septations– Thin calcifications in wall• Hemorrhagic cysts– 5% of all cysts– Low-level internal echoes– Fluid-debris level, fibrin membranes, internal clotsRenal cystic disease• Complex cysts– Hemorrhagic cyst– Infected cyst– Proteinaceous cyst– Multi-septated cyst– Abscess– Hematoma– Cystic RCC– Multilocular cystic nephromaHyperdense Renal cystOctober 2004 RadioGraphics, 24, S101-S115.Complex cysts• Hyperdense cyst on CT– Due to protein or hemorrhage– Most appear simple on U/S• Calcifications– 1-3% of cysts– Prior hemorrhage, infection, or ischemia– Thin, curvilinear generally benign– Thick, irregular more worrisome for malignancyPolycystic Kidney DiseaseBenign renal cysts inVon Hippel LindauSimple ComplexJanuary 2008 RadioGraphics, 28, 65-79.Peripelvic cysts-need to use real-time• Due to dilated pelvic lymphatics-vertical align• May be mistaken for hydronephrosis-horizontal orientationParapelvic cysts-real-time U/SHydronephrosisRenal stones• Urolithiasis-stones in collecting system– 12% of population by age 70– United States epidemic?– White, male, Southern climates– Affluence??– Risk factors• Low fluid intake• High animal protein diet– Conditions that promote urinary stasis -> stones• Nephrolithiasis-stones in renal parenchymaRenal stone-echogenic focusColor twinkle artifactRenal Stones• Predisposing factors– UPJ obstruction– ADPK disease– Caliceal diverticula– Tubular ectasia (medullary sponge kidney)– Horseshoe kidney• Calcium containing most common-85%• Uric acid 5-10%• Cystine  < 5%Renal stones• U/S vizualization depends on size, not composition• Not very accurate in stone size• Larger than 5 mm detectable with U/S (newer equipment, thin pts.--down to 2-3 mm)• Smaller stones may not shadow, difficult to differentiate from vascular calcifications• Tips– Use highest frequency probe (7-4 vs. 4-1 Mhz)– Color twinkle artifactNephrocalcinosis• Medullary nephrocalcinosis– Tubular ectasia (Med Sponge Kidney)– Renal tubular acidosis (type IV)– Hyperparathyroidism– Sickle Cell disease• Cortical nephrocalcinosis– Cortical necrosis, infarction– Oxaluria (Hyper)– Chronic GN– Alport’s SyndromeMedullary nephrocalcinosisMedullary NephrocalcinosisMedullary NephrocalcinosisCortical Necrosis3 day old male, mother had placental insufficiencyUreteral CalculusUreteral Calculi video clipUnusual cause of echogenic fociPt s/p bladder instrumentation, reflux, presumed air in collecting system4/0910/09Urinary Tract Infection• U/S has no role in uncomplicated UTI’s responding to ABX• Real role in persistent, chronic, or recurrent infections• Urosepsis• 2 functions– ID calculi, hydro, congenital anomalies– Detect complicated infections (i.e., abscess) or XGPFocal pyelonephritisFocal pyelonephritisFungal ballsPyonephrosis—fluid/debris levelDDX echoes in collecting systemblood, pus, fungal balls, tumor, crystalsRenal masses• RCC-80-85% of renal neoplasms• Uroepithelial tumors-5-10%• Wilm’s tumor-3-5%• Miscellaneous-5%– Mets– Lymphoma– Leukemia– AML– OncocytomaRCC-clinical• Peak incidence 6th decade• Hematuria, back/flank pain, palpable mass cardinal signs or sx• Weight loss, malasise, hypertension also common• Incidental discovery more common (Cross-Sectional imaging for other reasons)• Smaller tumors (< 3 cm) have good survival ratesRCC on ultrasound• Most hypoechoic to isoechoic• 10% are hyperechoic• Larger tumors are heterogeneous– Necrosis– Hemorrhage– Calcification• Poorly defined borders (except for small RCC)RCC-U/SRCCHypoechioc Renal Sinus and TCC• Difficult to distinguish renal pelvic tumors vs. hypoechoic fat• Benign findings– Irregular and poorly defined margins– Central and symmetric location in renal sinus– Posterior acoustic attenuation with non-viz. of posterior border– Unaffected peripheral hyperechoic sinus– Traversing hilar vessels on color DopplerJUM 2002, 21:993-999, Seong et alHypoechoic renal sinus• Renal sinus tumors– Well defined margin– Eccentric location in sinus– Partial/complete obliteration of hyperechoic sinus– Visible posterior margin– No posterior shadowing– Vessel displacement by mass– Rarely, associated caliectasisCopyright © 2008 by the American Roentgen Ray SocietySchmidt, T. et al. Am. J. Roentgenol. 2003;180:1639-164771-year-old man with transitional cell carcinoma (35 mm in diameter) of left kidneyNot TCC-probably sinus fatNo change in lesion size in 12 months……CT guided bx negative.Hypoechoic renal sinus lesionsColumn of BertinSolid, hypoechoic massRenal lymphoma13 yo boy with renal mass in 2004Renal Mass in 2009Probable old hemorrhage into cyst or focus of infection, now calcified,  AML less likelyRenal mass?Both cases are cystic renal cell carcinomaTypical RCC-atypical behavior• 87 yo female with multiple med. problems• Bx proven Furman Gr III chromophobe RCC• No change in 2+ years• Negative metastatic w/u• Conservative RXOncocytomaAngiomyolipomaRenal AMLEnlarged kidneys DDX• Hydronephrosis/cystic disorders• Diabetes mellitus• Acute GN• Acute vasculitis (lupus)• AIDS-related nephropathy• Lymphoma/leukemia• Amyloidosis• Acute renal vein thrombosisEnlarged, Echogenic kidneys42 yo male s/p suicide attempt, ingested ethylene glycolDDX: medical renal disease: acute GN, acute nephrotic syndrome, acute toxic nephritis, acute tubular necrosis, diabetic nephropathyLithium Toxicity2/08 1/11Lithium Toxicity video clipLithium Toxicity• 10,000 case per year• Narrow therapeutic window• 3 meds that aggravate situation– NSAID’s– ACE inhibitors– Sodium wasting diuretics• US--Echogenic kidneys with punctate calcs.• Chronic-renal atrophyConclusions• Renal ultrasound generally excellent screening test• Good for cysts, masses, r/o hydro, stones– Small stones still difficult, like to obviate CT’s– > 5 mm. stones seen generally• Color Doppler essential• Parapelvic cysts may mimic hydronephrosis• Most solid renal masses malignant

Basics of Renal Ultrasound

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Basics of Renal Ultrasound

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