Long term tissue responses to catgut and collagen sutures.

Reaction of catgut and collagen sutures in both wounded and nonwounded bladder, kidney, muscle, and liver tissue was studied in guinea pigs up to 130 days after implantation. A minimal amount of degradation of ths so-called absorbable sutures was observed. There was little difference in absorption rates in the tissues studied although there seemed to be slightly greater absorption in the kidney than in other tissues. Tissue responses were characterized by the formation of a bilaminar connective tissue capsule. The inner zone contained primarily fibroblasts and histiocytes, while lymphocytes, neutrophils, and eosinophils were scattered throughout both layers. Multinucleated giant cells were often observed in the inner layer, and aggregates of lymphocytes and mast cells were occasionally found in the pericapsular areas. Calculi formed on those suture loops that were loosely tied and thus projected into the bladder lumen.