Definition

 • Renal scarring associated with vesicoureteric reflux (VuR), a congenital disorder in which urine regurgitates from the bladder into the upper urinary tract.

Epidemiology

 • An important cause of CKD, responsible for up to 30% of cases in children and 10% of cases in adults.

 Aetiology

 • VuR.

* Note not all VuR cases are complicated by reflux nephropathy.

 Pathogenesis

 • Thought to be the result of reflux of infected urine into the kidney.

• Intra- renal reflux tends to occur at the poles of the kidneys where compound papillae are found.

• Compound papillae are more susceptible to reflux, as the papillary ducts open at less oblique angles onto a flat or concave surface.

 • Repeated inflammatory response to the infection causes tubulointerstitial injury and nephron loss, with replacement of nephrons by scarring.

• As more and more nephrons are lost, CKD progresses.

 Presentation

• Patients typically present with hypertension and/ or proteinuria and/ or CKD.

Macroscopy

 • The poles of the kidneys show macroscopic areas of renal cortical scarring.

 Histopathology

 • The scarred areas show features of chronic tubulointerstitial nephritis, with or without features of chronic pyelonephritis.

• In chronic tubulointerstitial nephritis, there is tubular atrophy and interstitial fibrosis, associated with a predominantly mononuclear inflammatory cell infiltrate. Some tubules show regular atrophy with thickened basement membranes and a reduced diameter, whereas others may be dilated and filled with proteinaceous material (‘thyroidization’). There is extensive global sclerosis of glomeruli; non- sclerosed glomeruli may show hypertrophy and secondary focal and segmental glomerulosclerosis.

• The microscopic features of chronic tubulointerstitial nephritis are not specific to reflux nephropathy and may be seen in other causes of CKD.

• In chronic pyelonephritis, neutrophils may be present in tubules and/ or in the interstitium in the case of ongoing infection. The collecting system shows marked chronic inflammation often with lymphoid aggregates and follicles.

Complications

• Recurrent urinary tract infection (UTI).

 • Renal stones.

 • CKD.