An 8-year-old child suffering from recurrent attacks of polyurea since childhood presents to the paediatrics OPD. On examination the child is short statured vitals and B.P. are normal. Serum Creatinine – 6 mg%, HCO3– 16 meq, Na– 134, K+ 4.2 On USG bilateral small kidneys are seen. Diagnosis is -
The lab investigations and symptoms of the child suggest Juvenile nephronophthisis.
Juvenile nephronophthisis 

It is the most common genetic cause of end-stage renal disease (renal failure) in childhood and adolescence.
It is an autosomal recessive disease.
The patients present before the age of 20 years.
The pt. presents with
Inability to conserve sodium because of defect of tubules leading to polyuria and polydipsia (Polyurea is resistant to vasopressin
Anaemia
Growth retardation (growth retardation, malaise & pallor are secondary to anaemia which is attributed to a def. of erythropoietin production by failing kidneys)
No hypertension (As nephronophthisis is salt-losing nephropathy)
Proteinuria and hematuria usually are absent
Sonography shows b/1 small kidneys with multiple cysts only in the medulla (cysts may only be seen if they are large enough. They are rarely visible early in disease)
Juvenile nephronophthisis is usually associated with many extra-renal conditions, one of which is hepatic fibrosis, which explains the high level of alkaline phosphatase in this patient.

Radiographic features

Small kidneys       
Loss of corticomedullary junction &
Multiple cysts        

About other options
Medullary cystic disease

Patient with medullary cystic disease presents with similar features as Juvenile Nephronophthisis but it can be differentiated by -
The absence of Growth Retardation
Age of presentation is 3rd or 4th Decade.
Hypertension may occur (in JN, hypertension is not seen).

In polycystic kidney disease, there is bilateral enlargement of the kidney.
In reflux Nephropathy the kidneys do not decrease in size and there will be a history of frequent urinary tract infections.
Reflux Nephropathy
Nephronophthisis
Polycystic kidney disease
Medullary cystic kidney disease