Reflux nephropathy (RN)

5. Reflux nephropathy (RN)

Definition

Reflux nephropathy (RN) is the renal scarring usually associated with VUR. VUR is retrograde flow of urine from the bladder to the kidneys. The main complication of VUR is scar formation that affects one or both kidneys in adults and is called RN.

Progressive renal scarring can lead to ESRD, although scarring may occur without VUR.

RN may be congenital (also called primary), a result of abnormal renal development leading to focal renal dysplasia, or acquired, resulting from pyelonephritis-induced renal injury.

Epidemiology

RN is commonly seen in childhood or early adulthood and is more common in females than males.

In adults, RN is commonly seen in pregnant women and postrenal transplant patients.

RN can occur with other conditions that lead to blockage of urine flow. Common causes of bladder outlet obstruction include posterior urethral valve in children, enlarged prostate in men; urinary bladder stones; neurogenic bladder (in people with multiple sclerosis, spinal cord injury or other neurological conditions) and can also be caused by swelling of ureters after kidney transplant or from injury to the ureter. The causes are summarized in Box 10.12.2.5.1.

BOX 10.12.2.5.1

CAUSES

Vesicoureteric reflux (M/C)

• Bladder outlet obstruction
- • Posterior urethral valve (child)
- • Enlarged prostate (adult)
• Urinary bladder stones
• Neurogenic bladder

Pathology

VUR leads to high-pressure sterile urine reflux (i.e. urine flows backwards from the bladder into the ureters and occasionally into the renal pelvis) which stunts the normal growth of the kidneys and often exacerbated by the recurrent infections. VUR ultimately results in the chronic interstitial nephritis, tubular atrophy and renal scarring along with glomerular hypertrophy and secondary focal segmental glomerular sclerosis (FSGS).

Clinical features

Usually asymptomatic but few patients may present with fever, dysuria, frequency, lethargy, loin pain and lumbar tenderness. If severe, patients may present with hypertension and/or renal insufficiency.

Complication

Complications of RN are insidious in onset and have slow progression. In adults, the consequences of VUR and RN are numerous and include UTI, urinary calculi, hypertension, complications during pregnancy, proteinuria and renal failure.

The potential complications in adults with RN are well established during pregnancy. These complications were significantly more common in those with bilateral renal scarring or impaired renal function at conception.

Pregnant females with RN may have accelerated hypertension, renal impairment and might lead to maternofoetal comorbidities.

The complications are summarized in Box 10.12.2.5.2.

BOX 10.12.2.5.2

COMPLICATIONS

• Urinary tract infection
• Urinary calculi
• Proteinuria
• Hypertension
• Focal segmental glomerular sclerosis (FSGS)
• Renal failure

Imaging

Micturating cystourethrogram (MCUG):

Used to investigate patients with recurrent UTIs to test for the presence of reflux. Depending on the degree of retrograde filling and dilation of the ureters VUR is classified into five grades (Fig. 10.12.2.5.1):

Grade I: Reflux of urine into the ureter only without dilatation of ureter.
Grade II: Reflux of urine into the ureter, renal pelvis and calyces without dilatation of ureter.
Grade III: Reflux of urine into the ureter and collecting system with mild dilatation of ureter.
Grade IV: Reflex of urine into the ureter and collecting system with moderate dilatation of ureter and moderate blunting of the calyces.
Grade V: Reflux of urine into the ureter and collecting system with severely dilated, tortuous ureter and blunting of calyces (Fig. 10.12.2.5.2).