Pathology of the Kidneys and Upper Urinary Tract

Hydronephrosis Causes

• Blockage: Blockage of urine flow down the ureter.

• Internal Blockage:

  • Calculi (kidney stones)

  • Scarring in the ureter

  • Tumors blocking the vesicoureteric junction (VUJ)

• External Blockage:

  • Mass effect compressing ureter

• Vesicoureteric Reflux:

  • Failure of bladder to empty properly

  • Common in babies and young children

  • Can be unilateral or bilateral

  • Urine flows back from bladder to kidneys, which can lead to infections and damage.

Hydronephrosis Grading System

• Grade I: Into nondilated ureter.

• Grade II: Into pelvis and calyces without dilatation.

• Grade III: Mild to moderate dilatation of ureter and renal pelvis.

• Grade IV: Moderate dilatation or tortuosity of ureter.

• Grade V: Severe dilatation and tortuosity of ureter, renal pelvis, and calyces.

• SFU Grading:

  • 1 and 2 mild, 3 moderate, 4 severe

    

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Pyelonephritis

• Definition: Urinary tract infection that originates in the urethra or bladder, traveling to the kidneys.

• Causes: Mainly caused by Gram-negative bacteria (e.g. E. coli) from fecal matter.

• Symptoms:

  • Fever

  • Nausea

  • Frequent urination

  • Pain in back, side, or groin

• Sonographic Presentation:

  • Can affect one or both kidneys.

  • Can be focal or diffuse.

  • Echogenic wedge defect in partial cases. - not the same as the congenital defect

  • Loss of blood flow seen on colour Doppler.

    

Renal Abscess

• Definition: A complication arising from pyelonephritis.

• Types: Both start with tubular necrosis

  • Renal Abscess: Forms a distinct walled-off cavity.

  • Perirenal Abscess: Appears more diffuse between renal capsule and fascia.

• Perirenal Abscess

  

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Pyonephrosis

• Definition: Presence of pus, debris, or haemorrhage within a dilated pelvicalyceal system.

• Sonographic Appearance:

  • Echoes within pelvicalyceal system.

  • May appear solid.

  • Can sometimes get layering - like sludge in the GB

  • Put colour on to see if it moves

    

Glomerulonephritis

• Definition: Inflammation of the glomeruli; acute or chronic.

• Implications: Usually affects both kidneys; early diagnosis and treatment are vital to prevent renal failure.

• Causes: Can arise from staphylococcal infections or immunologic illnesses.

• Sonographic appearance: hyperechoic kidneys, collecting system not dilating

• Key to distingush between pyelonephritis and glomerulonephritis would be patient hx - urinary infection (pyleonephirits)

  

Renal Scarring

• Causes: Usually due to recurrent UTIs, reflux, or pyelonephritis.

• Effect: Causes permanent damage to renal parenchyma and reduces kidney function.

• Sonographic Signs: Appears atop medullae, not between them; shows thinned parenchyma; fat fills the spot where the scarring occurs, which can lead to a characteristic echogenicity, indicating loss of normal renal architecture.

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Renal Atrophy

• Definition: Kidneys are smaller than expected for a person's age and height.

• Causes: Can be congenital (renal hypoplasia) or acquired due to chronic infections or hydronephrosis.

• Significance: Congenital cases typically do not require treatment unless parenchyma thickness is abnormally smaller

• Acquired due to lower blood supply to the kidneys and or loss of nephrons

  

Renal Failure

• Definition: End-stage kidney disease (ESKD) where kidneys cannot adequately filter blood or control bodily fluid levels.

• Progression: GFR decreases significantly, with ESKD being defined as GFR <15 ml/min.

• Sonographic Features:

  • Acute: Size may appear normal or enlarged with hypoechoic areas.

  • Chronic: Small, echogenic kidneys with structural abnormalities.

Duplex Kidney Pathology

• Definition: Characterized by the presence of two collecting systems or ureters.

• Anatomical Variations: Ureters may join before the bladder or have separate openings.

• Issues: Ectopic ureters are more susceptible to reflux due to abnormal placement, leading to hydronephrosis, particularly in the upper moiety.

• Sonographic Considerations: Identifying the location and functional status of both moieties is crucial.

Review Points

• Describe pathologies using appropriate sonographic terminology and distinguish differential diagnoses.

• Detail sonographic features of varying grades of hydronephrosis.

• List and explain pathologies encountered in duplex kidneys using sonographic terminology.