Answer by  
                                                                                          janaki (6)
                                                            
                          
                          
                                                           You can never come to a conclusion that underweight is due to Kidney disease.Underweight in children may be due to many reasons.They are Digestive disease, Hereditary from parents,Eating disorder, Thyroid disease  children symptoms of kidney disease includes increased in fatigue and sleepy,decrease in appetite and last poor stead of guessing and concluding better to consult the Doctor.