Why thiazides diuretics contraindication with impaired renal failure?

Thiazides in CKD. Thiazides are not contraindicated in renal failure for any medical reason. They are not used as they are ineffective of making patients urinate. Patients with chronic kidney disease are placed on loop diuretics which are able to evoke a diuretic response in patients with it. Patients on dialysis are given these drugs when they still have residual renal function so they can eliminate urine.
Renal filtration . The renal tubules are effected adversely with thiazides , preventing distal resorption of sodium and water , thus aggravating the renal clearance of BUN , cr, and other toxins in the blood.