Whether patients with hydronephrosis can drink water depends on whether the hydronephrosis has been resolved. Hydronephrosis occurs due to a blockage in the urinary system, often caused by inflammation, scarring, or adhesions of the ureters, or by obstructions such as stones or tumors in the urinary tract, or possibly by an enlarged prostate, leading to the inability of the bladder to properly expel urine. In summary, when the urine produced by the kidneys cannot be properly expelled from the body, it leads to the expansion of the renal pelvis and calyces, known as hydronephrosis. Drinking water at this time can certainly aggravate the condition of hydronephrosis if the body is already struggling to expel fluids. Therefore, if this blockage remains unresolved, patients should limit their intake of fluids. However, if the obstruction is cleared and the urinary tract is smooth, allowing urine to be expelled normally, drinking water is permissible.