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CT Imaging of the Kidney
Anthony Powell Gillian Lieberman, MD September 2001 CT Imaging of the Kidney Images: Netter, FH: Atlas of Human Anatomy, 2nd ed. Novartis, 1997 Images: BIDMC, Dept of Radiology, 2001. Anthony Powell, HMS IV Beth Israel Deaconess Medical Center Gillian Lieberman, MD 1 Anthony Powell Gillian Lieberman, MD Renal Anatomy: Axial View Peritoneum Right Kidney Renal Vein Renal Capsule Renal Artery Pararenal fat Perinephric fat Gerota’s Fascia Images: Netter, FH: Atlas of Human Anatomy, 2nd ed. Novartis, 1997 2 Anthony Powell Gillian Lieberman, MD Renal Anatomy: Sagittal View Renal Cortex Minor Calices Renal Pyramids Major Calices Renal Column (of Bertin) Renal Pelvis Ureter Images: Netter, FH: Atlas of Human Anatomy, 2nd ed. Novartis, 1997 3 Anthony Powell Gillian Lieberman, MD Standard CT Technique for Renal Imaging • 5mm-10mm collimation usually adequate to demonstrate kidneys • IV contrast allows differentiation of pathologic processes from nl parenchyma – Corticomedullary differentiation max at 30 sec – Nephrographic phase best seen at 70-100 sec • Non-contrast Helical CT for uro/nephrolithiasis 4 Anthony Powell Gillian Lieberman, MD Congenital Abnormalities • Duplicated collecting system/partial duplication bifid renal pelvis • Horseshoe Kidney – Connecting isthmus across midline, usu between lower poles • Crossed Ectopia – The ureter of the ectopic kidney inserts into the bladder orthotopically (I.e. on opposite side) • Pelvic or Intrathoracic Kidney • Renal hypoplasia • Renal agenesis 5 Anthony Powell Gillian Lieberman, MD Crossed Ectopia • Lower kidney is usually the ectopic one • In 90% there is fusion of both kidneys (crossedfused ectopia) • Incidence 1:1000 births • Slightly increased incidence of calculi, however, incidence of other assoc anomalies is low 6 Anthony Powell Gillian Lieberman, MD Crossed Ectopia Axial abdominal CT, contrast enhanced, nehrogram phase Right orthotopic kidney Left crossed ectopic kidney 7 Images: BIDMC, Dept of Radiology, 2001. Anthony Powell Gillian Lieberman, MD Nephrocalcinosis Causes: • Renal Artery Atherosclerosis • Nephrolithiasis= stones in the collecting system • Medullary Nephrocalcinosis (95%)= calcium deposition in medulla – Renal Tubular Acidosis, Medullary Sponge Kidney, HyperCa2+ states (hyperPTH, Paraneoplastic), Papillary necrosis (Diabetes Mellitus, sickle cell), TB • Cortical Nephrocalcinosis (5%)= calcium deposition in cortex – Chronic poststrep glomerulonephritis, Oxalosis, Alport synd, Acute cortical necrosis • Infection, Cyst, Tumor, Hematoma 8 Anthony Powell Gillian Lieberman, MD Nephrolithiasis • Epidemiology – Up to 10% by age 70, usu in 3rd to 4th decade – 4:1 M to F ratio – More prevalent in the South • Risk Factors – Hypercalcemic states, Crohn’s, stents, RTA, infection, gout, hypercalciuria, hyperuricosuria, cystinuria • Symptoms – Asymptomatic, flank pain, hematuria 9 Anthony Powell Gillian Lieberman, MD Composition OPAQUE contains calcium +/ phosphate • Calcium calculi – Ca oxalate, Ca phosphate • Struvite calculi – Magnesium ammonium phosphate= triple phosphate SEMI OPAQUE contains sulphur • Cystine calculi LUCENT • Uric acid stones;Xanthine • Matrix (coagulated mucoid material) 10 Anthony Powell Gillian Lieberman, MD CT Imaging of Stones • Essentially all renal and ureteral calculi have high attenuation on non-contrast CT (all but matrix stones have atten of > 100HU) • CT has sensitivity of 97% and specificity of 96% • Can also see hydronephrosis, hydroureter, renal enlargement, or perirenal stranding • Must differentiate from phlebolith which is a calcified blood clot in a pelvic vein.(appearance: round/ovoid, smooth, central lucency, in true pelvis) 11 Anthony Powell Gillian Lieberman, MD Nephrolithiasis Radio opaque stone in calyx 12 Images: BIDMC, Dept of Radiology, 2001. Anthony Powell Gillian Lieberman, MD Hydronephrosis Dilated urine filled pelvis Stent Images: BIDMC, Dept of Radiology, 2001. 13 Anthony Powell Gillian Lieberman, MD Hydroureter Stent 14 Images: BIDMC, Dept of Radiology, 2001. Anthony Powell Gillian Lieberman, MD Pyelonephritis • Bacterial infection of portions of renal parenchyma • Usually via ascending infection from the bladder • Risk Factors include vesicoureteral reflux, DM, pregnancy, immunocompromised states, prolonged catheterization, neurogenic bladder • Sx’s include flank pain, fever, pyuria, leukocytosis • Usual suspects Æ E. coli, proteus, klebsiella 15 Anthony Powell Gillian Lieberman, MD CT Imaging of Pyelonephritis • Focal or diffuse renal enlargement • Parenchyma may be low in attenuation on noncontrast (C-) images • Usually wedge-shaped regions of decreased enhancement on C+ images • Perinephric stranding or fluid collections, often w/ thickening of Gerota’s fascia 16 Anthony Powell Gillian Lieberman, MD Pyelonephritis 17 Images: BIDMC, Dept of Radiology, 2001. Anthony Powell Gillian Lieberman, MD Xanthogranulomatous Pyelonephritis (XGP) • Bacterial renal infection with an unusual/characteristic immune response • Parenchyma infiltrated with lipid-laden macrophages • Proteus mirabilis is usual causative organism • Associated with staghorn calculus • Often chronic, non-spec sx’s Æ fever, malaise, pain, leukocytosis 18 Anthony Powell Gillian Lieberman, MD CT Characteristics of XGP • May demonstrate classic finding of staghorn calculus • Low-attenuation renal mass; decreased excretion of contrast • Enlarged kidney • Perinephric inflammatory changes • 85% of cases have diffuse renal involvement 19 Anthony Powell Gillian Lieberman, MD Xanthogranulomatous Pyelonephritis Sephern calcubus Perirephric inflammatory change 20 Images: BIDMC, Dept of Radiology, 2001. Anthony Powell Gillian Lieberman, MD XGP with Staghorn Calculus 21 Images: BIDMC, Dept of Radiology, 2001. Anthony Powell Gillian Lieberman, MD Perinephric Stranding from XGP 22 Images: BIDMC, Dept of Radiology, 2001. Anthony Powell Gillian Lieberman, MD Renal Cystic Disease • Very commonÆ 50% of pts over age of 50 • Assoc w/ many syndromes, etiology unknown, probably arise from obstructed tubules or ducts • Most commonly asymptomatic • Rarely, may have hematuria, HTN, cyst infection, or mass effect 23 Anthony Powell Gillian Lieberman, MD CT Characteristics of Simple Cysts • Smooth, imperceptible cyst wall • Sharp demarcation from surrounding renal parenchyma • Water attenuation (<15 HU), homogenous throughout lesion • Non-enhancing • Simple cysts are w/o septations or calcification • May have slight elevation of adjacent renal parenchyma Æ Beak sign 24 Anthony Powell Gillian Lieberman, MD Complex Cysts: Categorized using the Bosniak Classification • Categories based on imaging features that are intended to serve as guideline for estimating likelihood of malignancy Type I- simple cyst Type II- mildly complicated cystÆ mild Ca2+, thin septations, no enhancement IIF- slightly more complex type II lesions Type III- complex cystsÆ thick wall; multiple, irreg, thick septations/calcifications, no enhancement Type IV- cystic neoplasmÆ enhancing wall or solid component 25 Anthony Powell Gillian Lieberman, MD Treatment • • • • • Type I – no f/u required Type II – no f/u required Type IIF – f/u CT after 3-6 months Type III – Excision Type IV - Excision 26 Anthony Powell Gillian Lieberman, MD Type I Simple Cyst Bird Beak Sign Aortic aneurysm Simple Cyst Inferior vena cava with filters 27 Images: BIDMC, Dept of Radiology, 2001. Anthony Powell Gillian Lieberman, MD Type IV Cystic Neoplasm Complex renal mass infiltrating lvc 28 Images: BIDMC, Dept of Radiology, 2001. Anthony Powell Gillian Lieberman, MD Conditions Associated with Multiple Cysts • • • • • • Autosomal Dominant PCKD Autosomal Recessive PCKD Acquired Cystic Disease (hemodialysis pts) Von-Hippel-Lindau disease Tuberous Sclerosis Medullary Sponge Kidney 29 Anthony Powell Gillian Lieberman, MD Benign Masses • • • • • Cysts Angiomyolipoma Oncocytoma (via epithelial cells of prox tubule) Renal Adenoma Mesoblastic Nephroma (hamartomatous tumor, usu present at birth) • Hemangioma • Various Renal Pelvic Tumors(papilloma, angioma, fibroma) • Hematoma 30 Anthony Powell Gillian Lieberman, MD Angiomyolipoma • Hamartomas containing fat, smooth muscle, and blood vessels • Usually asymptomatic, but may spontaneously bleed • Large AMLs resected or embolized • Multiple AMLS usually Associated w/ tuberous sclerosis • On CTÆ *fat attenuation in mass*, strong contrast enhancement (RCCs rarely contain fat), no Ca2+ 31 Anthony Powell Gillian Lieberman, MD Angiomyolipoma Note fat content 32 Images: BIDMC, Dept of Radiology, 2001. Anthony Powell Gillian Lieberman, MD Malignant Masses • • • • Renal Cell Cancer Transitional Cell Cancer Wilm’s Tumor Nephroblastomatosis (multiple rests of embryologic metanephric blastoma) • Lymphoma • Metastases (lung, breast, colon, melanoma) 33 Anthony Powell Gillian Lieberman, MD Renal Cell Ca • Most common primary renal malignancy (85% of primary renal tumors) • Assoc w/ smoking, family hx, age, Von HippelLindau, Acquired Cystic Disease/chronic dialysis, phenacetin abuse • Presentation: Hematuria, flank pain, wt loss, palp mass, fever, anemia, paraneoplastic syndromes • liver enzymes w/o metsÆ Stauffer syndrome 34 Anthony Powell Gillian Lieberman, MD CT characteristics • VariableÆfrom complex cyst to large, heterogeneous renal mass • Generally enhancing • May have calcifications • May have hemorrhage and central necrosis • Usually no fat 35 Anthony Powell Gillian Lieberman, MD Robson Staging • Stage I – contained w/in renal capsule • Stage II – contained w/in Gerota’s fascia • Stage III A – venous invasion (renal v, IVC) B – lymphatic invasion C – both • Stage IV – distant metastasis (lungs, liver, lytic bone, adrenal, contra renal) 36 Anthony Powell Gillian Lieberman, MD Renal Cell Ca 37 Images: BIDMC, Dept of Radiology, 2001. Anthony Powell Gillian Lieberman, MD RCC 38 Images: BIDMC, Dept of Radiology, 2001. Anthony Powell Gillian Lieberman, MD References • • • • • Netter, FH: Atlas of Human Anatomy, 2nd ed. Novartis, 1997 Slone RM, Fisher AJ, Pickhardt PJ, Gutierrez FR, Balfe DM: Body CT, A Practical Approach, 1st ed. McGraw-Hill, 2000 Weissleder R, Rieumont MJ, Wittenberg J: Primer of Diagnostic Imaging, 2nd ed. Mosby, 1997 Beth Israel Deaconess Medical Center, Dept of Radiology, Teaching Files, 2001 Gay SB, Woodcock RJ: Radiology Recall, 1st ed. Lippincott Williams and Wilkins, 2000 39 Anthony Powell Gillian Lieberman, MD Acknowledgements • • • • • Pamela Lepkowski Gillian Lieberman M.D. Richard Cooper M.D. Joe Barry M.D. Mary Keogan M.D. 40
