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What is the significance of increased renal echogenicity on Ultrasound?
Solid organs, such as the liver and spleen, have intermediate echogenicity, and the kidney parenchyma, consisting of the cortex and medulla, is normally isoechoic (equal in brightness) or hypoechoic (darker) compared with the normal liver or normal spleen.
Increased renal echogenicity on ultrasound refers to a finding where the kidneys appear brighter or more echogenic than expected. This finding can have various implications depending on the clinical context and other associated findings.
Increased renal echogenicity is an indication of parenchymal disease but is nonspecific for the type of parenchymal disease, which may include the below
- Acute or chronic glomerulonephritis
- Acute interstitial nephritis
- Diabetes mellitus
- Systemic lupus erythematosus
- HIV nephropathy
- Amyloidosis
Increased renal echogenicity in infants changes gradually in the adult pattern.
Several reports have stated that increased echogenicity of the renal parenchyma is an indicator of renal disease
Percutaneous renal biopsy is therefore frequently required for a definitive diagnosis.
Echogenicity of the renal cortex relative to liver or spleen can be evaluated both qualitatively and quantitatively, though qualitative method is commonly used.
Here are some potential significances of increased renal echogenicity:
- Renal Parenchymal Disease: Increased renal echogenicity can be indicative of renal parenchymal disease, which refers to structural abnormalities or damage to the functional tissue of the kidneys. Conditions such as chronic kidney disease, diabetic nephropathy, glomerulonephritis, and renal fibrosis can cause increased echogenicity.
- Renal Infection or Inflammation: Infections or inflammatory conditions affecting the kidneys, such as pyelonephritis or interstitial nephritis, can lead to increased renal echogenicity. These conditions are often associated with other signs such as renal enlargement, presence of renal calculi, or focal areas of hypoechogenicity.
- Renal Scarring: Scarring of the renal tissue, often resulting from previous infections, inflammation, or trauma, can cause increased echogenicity. This may be observed as focal or diffuse areas of increased echogenicity within the renal parenchyma.
- Renal Stones: Renal stones (nephrolithiasis) can cause increased echogenicity when they are present within the collecting system or renal parenchyma. The presence of stones can cause acoustic shadowing, resulting in increased echogenicity in the surrounding tissue.
- Renal Fat Infiltration: In some cases, increased renal echogenicity can be attributed to the infiltration of fat into the renal parenchyma. This can occur in conditions such as renal lipomatosis or obesity-related changes in the kidneys.
When the right kidney is more echogenic than the normal liver and the left kidney is isoechoic or more echogenic than the normal spleen, the kidneys can be characterized as being abnormally echogenic.
Normal renal cortex is usually hypoechoic (less bright) or sometimes isoechoic (similar brightness) to that of liver or spleen.
Thus, liver and spleen echogenicity must be normal for comparison to be valid; in particular, fatty infiltration of the liver can increase its echogenicity, making evaluation of the echogenicity of the right kidney more difficult.
The normal renal cortex in older infants, children, and adults should be less echogenic than the liver parenchyma.
Only in neonates and infants is increased echogenicity of the renal parenchyma a normal finding.
It’s important to note that increased renal echogenicity is a nonspecific finding, and further evaluation is usually required to determine the underlying cause. This may involve additional imaging studies, laboratory tests, or clinical correlation. Consulting with a healthcare professional, such as a nephrologist or radiologist, is recommended for a comprehensive evaluation and appropriate management based on individual circumstances and findings.
- A study report data on newborn infants with increased renal echogenicity observed at the Division of Neonatal Intensive Care of Pavia during a five-year period.
- Review of 1600 abdominal ultrasonic evaluations revealed 103 newborn infants (56 females and 47 males, with birth weight from 560 to 3700 g and gestational age from 25 to 42 weeks) whose kidneys showed increased echogenicity.
- Three patients with infantile polycystic kidney disease, two with renal candidiasis, three with dysplastic kidney and two with renal vein thrombosis showed diffuse hyperechogenicity.
- Three patients with hemolytic-uremic syndrome showed cortical hyperechogenicity. Increased medullary echogenicity was observed in 90 infants with renal disease secondary to perinatal asphyxia.
- In 76 of these patients the evaluation of renal echogenicity and the renal function improved, while in the remaining 14 newborns the renal alteration persisted until death.
Sources
- Chiara A, Chirico G, Comelli L, De Vecchi E, Rondini G. Increased renal echogenicity in the neonate. Early Hum Dev. 1990 Apr;22(1):29-37. doi: 10.1016/0378-3782(90)90023-c. PMID: 2185929.https://pubmed.ncbi.nlm.nih.gov/2185929/
