Diagnostic Ultrasound - Abdomen and Pelvis

Hypoechoic Kidney
Differential Diagnoses: Kidney
DIFFERENTIAL DIAGNOSIS
Common
• Acute Pyelonephritis
• Severe Fatty Liver (Mimic)
• Renal Parenchymal Disease
Less Common
• Perinephric Hematoma or Other Fluid Collection
• Acute Renal Transplant Rejection
• Acute Renal Vein Thrombosis
• Acute Renal Artery Thrombosis
• Renal Cell Carcinoma
• Upper Tract Urothelial Carcinoma
• Multiple Myeloma
• Renal Leukemia
• Renal Lymphoma
• Hypoechoic Renal Fat With Atrophic Kidneys
Rare but Important
• Acute Amyloidosis
• Acute Cortical Necrosis
• Xanthogranulomatous Pyelonephritis
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
• Determine if there is diffuse hypoechogenicity or focal
hypoechoic lesion
○ And if there is distortion of normal architecture by
infiltration
• Use color Doppler to look for vascular flow or distortion of
normal vessels
• Most commonly related to nonneoplastic conditions
○ Infection
○ Inflammation
○ Vascular thrombosis or arteritis
○ Deposition of abnormal proteins
• Neoplasms
○ Typically of infiltrative type
– Renal lymphoma, leukemia and multiple myeloma
○ Less commonly renal cell or urothelial carcinoma
– May be large and infiltrative
– Tend to be more heterogeneous
Helpful Clues for Common Diagnoses
• Acute Pyelonephritis
○ Ascending bacterial infection
○ Manifestations include
– Diffuse hypoechoic renal parenchyma
– Focal hypoechoic or hyperechoic round or wedgeshaped
lesions
– May progress to thick-walled abscesses
– Urothelial thickening
– Decreased color Doppler flow secondary to
vasoconstriction
• Severe Fatty Liver (Mimic)
○ Highly attenuating fatty liver may cause spurious
decreased echogenicity of kidney
○ Attempt ultrasound imaging directly and posteriorly
• Renal Parenchymal Disease
○ Acute forms of glomerulonephritis and lupus nephritis
○ May cause enlarged hypoechoic kidney but typically
hyperechoic
○ Diseases affecting tubules and interstitium tend to
increase cortical echogenicity
Helpful Clues for Less Common Diagnoses
• Perinephric Hematoma or Other Fluid Collection
○ May occur spontaneously in patients with coagulopathy
– Or after spontaneous forniceal rupture in acute
ureteral obstruction
○ Also after trauma, surgery, interventional procedure
○ May compress kidney and cause renal dysfunction
○ Perirenal or subcapsular collection of blood, urine,
lymphatic or serous fluid
○ Hematomas have variable echogenicity
○ Other collections are hypoechoic to anechoic
○ Color/power Doppler helpful to identify kidney
• Acute Renal Transplant Rejection
○ Swollen and hypoechoic kidney
○ Urothelial thickening
○ Resistive index may be elevated
○ Color perfusion may be decreased
○ Diagnosis requires biopsy
• Acute Renal Vein Thrombosis
○ Enlarged and relatively hypoechoic native or transplant
kidney
○ Usually segmental or subsegmental venous thrombus
○ Abnormally high resistive index with reversal of arterial
flow in diastole
○ Absence of venous flow, complete or partial
○ Secondary to hypercoagulability
– Direct tumor invasion from renal or adrenal carcinoma
– Nephrotic syndrome
– Dehydration and sepsis in children particularly
○ After renal transplantation
– May be iatrogenic from surgical injury or technical
difficulties
– May be due to fluid collections or compartment
syndrome
• Acute Renal Artery Thrombosis
○ May affect main or segmental artery of native or
transplant renal artery
○ Main renal artery embolism results in swollen kidney
with decreased renal echogenicity
○ Absence of color flow may be segmental or total
○ Secondary to dissection, trauma, embolism, hypotension
○ After renal transplantation
– Etiologic factors as above
– Additionally associated with severe acute or chronic
rejection
• Renal Cell Carcinoma
○ Variable size and echogenicity
○ Large tumors tend to be hypoechoic and can be necrotic
○ Smaller tumors are more echogenic
• Upper Tract Urothelial Carcinoma
○ Typically soft tissue mass in renal pelvis
○ Causes obstruction, resulting in hydronephrosis
○ Aggressive tumors can diffusely infiltrate kidney with
preservation of renal contour
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