"Paint brush-like" pattern in intravenous urography is seen in:

Medullary sponge kidney: The medullary and papillary poions of the collecting ducts are dysplastic and dilated and in most cases develop medullary nephrocalcinosis. Most patients with medullary sponge kidney remain asymptomatic throughout life, with the diagnosis only made incidentally when the renal tract is imaged for other reasons. The pathology is a developmental defect affecting formation of collecting tubules results in cystic dilatation of medullary and papillary poions of collecting ducts. Intravenous urogram demonstrates the bright brush-like or "paintbrush" pattern of contrast collection along the ectatic medullary collecting tubules uniformly directing the cupping of papillae. Ref: Harrisons principles of internal medicine, 18th edition, Page: 2360.