Pathology of the Kidneys and Upper Urinary Tract

Hydronephrosis

Blockage of urine flow down the ureter.

Causes of hydronephrosis

Internal: calculi (kidney stones), scarring in the ureter, tumours blocking the vesicoureteric junction (VUJ)

External:  mass effect compressing ureter

Vesicoureteric reflux: failure of bladder to empty properly

Hydronephrosis Clinical Presentation

Flank pain, haematuria, fever, Leukocytosis

Vesicoureteric reflux

Failure of the bladder to empty properly, common in babies and young children, leading to urine reflux from the bladder back into the kidney.

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.

Pyelonephritis

Urinary tract infection that starts in the urethra or bladder and travels to the kidneys.

Main cause of pyelonephritis

Gram-negative bacteria (i.e., E. coli).

Pyelonephritis Clinical Presentation

Fever, nausea, frequent urination, and pain in the back, side, or groin.

Leukocytosis

Pyelonephritis US 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

Complication of pyelonephritis

Can be a renal abscess or perirenal abscess

Renal abscess US presentation

Forms a distinct walled-off cavity

Perirenal abscess US presentation

Appears more diffuse between renal capsule and fascia

Renal abscess clinical presentation

Flank pain’

Fever

Leukocytosis

Pyonephrosis

Pus, debris, or haemorrhage seen within a dilated pelvicalyceal system.

Pyonephrosis US presentation

• 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

Inflammation of the glomeruli; acute or chronic

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

Causes of Glomerulonephritis

Staphylococcal infection (strep throat) and Immunologic illnesses.

Glomerulonephritis Clinical Presentation

Asymptomatic

Proteinuria

Oliguria

Hypertension

Haematuria

Fatigue

Oedema

Glomerulonephritis US presentation

• Hyperechoic kidneys, collecting system not dilating

Renal Scarring

Usually due to recurrent UTIs, reflux, or pyelonephritis which causes permanent damage to renal parenchyma and reduces kidney function.

Renal Scarring US Presentation

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

Renal Atrophy

Kidneys are smaller than expected for a person's age and height

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

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

Kidneys no longer adequately filter the blood of waste products or control fluid levels.

Renal Failure Clinical Presentation

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

Chronic

• Elevated BUN and creatinine

• Proteinuria

• Polyuria

• Headaches

• Fatigue

• Weakness

• Anaemia

US presentation of Renal Failure

Acute – may appear normal in size or be enlarged and hypoechoic with parenchymal disease;

Chronic – small, echogenic kidneys with loss of normal anatomy.

Duplex Kidney Pathology

Characterized by the presence of two collecting systems or ureters.

Ureters may join before the bladder or have separate openings.

Why are ectopic ureters more susceptible to reflux?

Due to abnormal placement, leading to hydronephrosis, particularly in the upper moiety.

 

What is the key to distinguish between pyelonephritis and glomerulonephritis?

would be patient hx - urinary infection (pyelonephritis)