Hydronephrosis and urine retention in estrogen-implanted athymic nude mice.

Subcutaneous estrogen pellet implantation is commonly practiced to induce tumor promotion in nude (Nu-FOXn1(nu)) mice for xenograft tumor modeling. Twelve of 23, 18-week-old nude mice developed dysuria after estrogen pellet implantation. Physical examination revealed variably distended abdomens with palpable distended bladders. All mice were euthanatized and postmortem examinations were made. Blood samples of the mice were collected, and serum estrogen concentration was measured. Postmortem examination revealed variable dilation of the urinary bladder and unilateral or bilateral dilations of ureters and kidneys. Microscopically, 12 of 23 mice and 13 of 23 mice showed dilated urinary bladder and hydronephrosis, respectively.