Regeneration of the renal calyces after calycectomy: an experimental study

On 14 rabbits, 21 kidneys were subjected to a calycectomy or the tip of the papilla was cut off by caudal nephrotomy. During an observation period of 2, 4, 6, 8 and 10 days, and further after 3 and 6 weeks the macroscopic and microscopic investigations led to the following results clearly answering the question put at the beginning of the inquiry: (1) even if parts of the renal calyces are removed, a complete regeneration of the renal pelvic mucosa takes place in the damaged area; (2) regeneration of the mucosa begins in neighbouring renal pelvic epithelium and the epithelium of the collecting tubes; (3) regeneration starts on the 4th day and is essentially ended by the 3rd week; this regeneration extends over the whole of the injured area; after the 6th week the process is finished and no inflammatory changes are to be found in the damaged area, and (4) in the process of healing no fibrous tissue is formed at the occlusion of the lamina cribrosa in the area of the papilla; there is no demonstrable necrosis of the renal parenchyma where the mucosa was removed. Hydronephrosis in this area is evident, beginning on the 3rd or 4th day and is to be regarded as the result of inflammatory process or of the operation itself. It is partly in evidence after 6 weeks but is clearly in a regressive stage. Morphologically a functional loss of the affected area of renal tissue cannot be demonstrated. The four questions made and answered by this animal experiment allow the following conclusion: calycectomy can be successfully undertaken. Regeneration of the mucosa is almost finished after 3 weeks and finally completed after 6 weeks. Considerable cicatrisation in the area of the mucous membrane injury or of its nephrons is morphologically unimportant. Calycectomy should be preferred to polar resection as there is a smaller parenchymal loss.