Diagnostic Ultrasound - Abdomen and Pelvis

Enlarged Kidney
948
Differential Diagnoses: Kidney
DIFFERENTIAL DIAGNOSIS
Common
• Hydronephrosis
• Acute Pyelonephritis
• Primary Renal Tumors: Benign and Malignant
• Compensatory Renal Hypertrophy
• Duplex Kidney
• Renal Parenchymal Diseases
○ Acute Glomerulonephritis, Lupus Nephritis, Diabetic
Nephropathy, Acute Tubular Necrosis
• Renal Vascular Diseases
○ Acute renal vein thrombosis, acute renal infarction, acute
cortical necrosis
• Renal Abscess
• Pyonephrosis
• Perinephric Fluid Collections
• Renal Trauma
Less Common
• HIV Nephropathy
• Autosomal Dominant Polycystic Kidney Disease (ADPKD)
• Multicystic Dysplastic Kidney (MDK)
• Horseshoe Kidney
• Crossed Fused Renal Ectopia
Rare but Important
• Autosomal Recessive Polycystic Kidney Disease (ARPKD)
• Renal Lymphoma
• Renal Leukemia
• Xanthogranulomatous Pyelonephritis
• Renal Amyloidosis
• Renal Tuberculosis
• Exercise-Induced Nonmyoglobinuric Acute Renal Failure
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
• Establish if renal enlargement is unilateral or bilateral and if
enlargement is focal or diffuse
• Acute causes: Obstruction, infection, inflammation
• Chronic causes: Cellular hypertrophy, abnormal protein
deposition, malignancies, infection, glomerular or
microvascular proliferation
Helpful Clues for Common Diagnoses
• Hydronephrosis
○ Splitting of central renal echocomplex by branching fluid
filled pelvis
○ Dilated calyces may be variable in size
○ Cortical thinning in chronic hydronephrosis
○ Look for dilated ureter and determine if simply dilated or
truly obstructed (VCUG/MAG 3 renogram)
○ Gross hydronephrosis may mimic multicystic dysplastic
kidney, ovarian or mesenteric cyst (in infants), or large
collection
○ Causes include stones, tumors, congenital
malformations, clot, infection, extrinsic compression,
bladder outlet obstruction, and vesico ureteral reflux
• Acute Pyelonephritis
○ Normal renal size or diffuse enlargement
○ Echogenicity variable: Decreased or increased
○ Focal pyelonephritis
– Focal alteration of cortical echogenicity
– Wedge shaped, triangular, or round
– May produce a focal external cortical bulge
– Wedge-shaped perfusion defect extending from
papilla on color and power Doppler or contrastenhanced
ultrasound
□ Cortical vascularity decreased secondary to cortical
vasoconstriction and edema
• Primary Renal Tumors: Benign and Malignant
○ Renal Cell Carcinoma
– Varied size and appearance
– Exophytic echogenic renal mass when large
– Hypoechoic rim, cystic change from necrosis,
calcification
– Diffuse infiltration is less common
○ Upper Tract Urothelial Carcinoma
– Hydronephrosis and dilated calyces secondary to
pelvic or ureteral tumor
– Infiltrating soft tissue mass in renal pelvis or pelvic wall
thickening
○ Renal Angiomyolipoma (AML)
– Echogenic mass with posterior shadowing, single or
multiple
– Variable size and lipid content
□ Lipid poor are less echogenic
□ Usually require confirmation with CT or MR
– Large AML may be indistinguishable from other renal
solid tumors
○ Multilocular Cystic Nephroma
– Multilocular encapsulated cystic lesion, which may
herniate into renal pelvis
○ Mesoblastic Nephroma
– Typically solid unilateral mass in neonate or fetus
• Compensatory Renal Hypertrophy
○ Enlarged, otherwise unremarkable kidney
○ Occurs with contralateral renal disease, aplasia/dysplasia,
or nephrectomy
• Duplex Kidney
○ Splitting of central echogenic renal sinus into upper and
lower pole moieties
○ 2 distinct draining ureters may be seen if they are dilated
• Renal Parenchymal Diseases
○ Acute Glomerulonephritis
– Bilateral enlarged kidneys with hyperechoic cortex
and prominent pyramids
○ Lupus Nephritis
– Acute: Normal or increased size bilaterally; cortical
echogenicity increased or normal
– May also have multiple focal infarcts
○ Diabetic Nephropathy
– Bilateral enlarged bright kidneys in early stage
○ Acute Tubular Necrosis
– Normal or diffuse bilateral renal swelling
– Prominent pyramids due to edema
• Renal Vascular Diseases
○ Acute Renal Vein Thrombosis
– Common in membranous glomerulonephritis