BEHAVIOR OF CHROMED CATGUT AND POLYGLECAPRONE 25 SUTURES IN THE URINARY BLADDER OF RATS, WITH SPECIAL REFERENCE TO STONE FORMATION

BEHAVIOR OF CHROMED CATGUT AND POLYGLECAPRONE 25 SUTURES IN THE URINARY BLADDER OF RATS, WITH SPECIAL REFERENCE TO STONE FORMATION ¹

Maria de Lourdes Pessole Biondo-Simões²

Luis Martins Collaço ²

Cristina Veronese ³

Marlene Miranda Ribas³

Silvana Negrelli Flores³

BONDO-SIMÕES, M.L.P.; COLLAÇO, L.M.; VERONESE, C.; RIBAS, M.M.; FLORES, S.N. - Behavior of chromed catgut and polyglecaprone 25 sutures in the urinary bladder of rats, with special reference to stone formation. Acta Cir. Bras., 13(1):26-29, 1998.

SUMMARY: In order to determine and compare the behavior of chromed catgut and polyglecaprone 25 sutures, 49 female rats anesthetized with ether were submitted to laparotomy, cystotomy and cystorrhaphy with separate stitches using catgut for group C and polyglecaprone 25 for group E. When the bladders were observed 3, 7, 15, 30 and 50 days after suture application, stone formation was observed in 6 group C animals (p = 0.0058), with two stones (one per stitch) in 3 of them. No stones were detected in group E bladders. Microscopy revealed a similar course for the healing process and crystals were observed only in group C (p = 0.0159). We conclude that: 1) the tissue behavior of chromed catgut and polyglecaprone 25 sutures is similar, 2) catgut sutures produce lithiasis in 46.15% of the bladders sutured with it up to 50 days after surgery (p = 0.0058), and 3) polyglecaprone 25 sutures do not produce lithiasis up to 50 days after surgery.

SUBJECT HEADINGS: Suture, Bladder, Stone

INTRODUCTION

Suture materials in the urinary tract are foreign bodies with the ability to attract calcium ions which crystallize. This ability is not uniform for all materials. YUDOFSKY and SCOTT⁷ reported that absorbable sutures showed a lower incidence of stone formation. In a study comparing different types of suture, MORRIS, BAQUERO, REDOVAN, MAHONEY and BANNETT⁴ observed a lower frequency of stone formation when they employed chromed catgut. HANKE, TIMM, FALK and KRAMER² stated that among absorbable sutures, polyglactine 910 may be the least lithogenic material. However, these same authors believe that the ideal material for synthesis of the urinary tract has not yet been found.

Polyglecaprone 25, an absorbable synthetic monofilament suture prepared from a copolymer of the glycolide epsilon caprolactone, recently became available on the market. We found no report in the literature of the use of this material for urinary tract synthesis.

The objective of the present study was to monitor the behavior of polyglecaprone 25 in the healing of the urinary bladder and its lithogenic ability in comparison with chromed catgut sutures.

METHOD

The study was conducted on 49 female Wistar-TECPAR rats (Rattus norvegicus albinus, Rodentia, Mammalia) aged 210 days and weighing 198 to 307 g (mean: 253.71 g), provided by the Technological Institute of Parana. The animals were housed in propylene cages of standard dimensions in groups of 5 animals and maintained at the Laboratory of Clinical and Surgical Experimentation of the Evangelical Faculty of Medicine of Parana, under a light-dark cycle, at ambient temperature and humidity, with no artificial regulation. The animals had free acces to commercial ration and water throughout the experiment.

The rats were divided at random into two groups: 24 control animals (group C) and 25 experimental animals (group E). Under ether anesthesia, the animals were depilated on the ventral abdominal wall by pulling out the hairs and fixed to a surgical board in dorsal decubitus and the skin was disinfected with polyvinylpyrrolidone-iodine. The abdominal cavity was exposed through a median incision of approximately 3.0 cm starting at the upper margin of the pubis and involving all planes of the ventral abdominal wall.

Cystotomy of approximately 0.5 cm was performed in the fundus of the bladder. C animals were submitted to synthesis with two separate total stitches using 5-0 chromed catgut, and E animals were submitted to similar synthesis using polyglecaprone 25 sutures. During laparorrhaphy, carried out on two suture planes with continuous stitching, the first involving the peritoneum-muscle-aponeurosis and the second the skin, 5.0 monofilament nylon was used. After recovery from anesthesia, the rats were identified and placed in their cages with free acces to ration and water. The animals were sacrificed in groups of 5 by excess ether inhalation on the 3rd, 7th, 15th, 30th and 50th postoperative day for examination. The abdominal cavity was opened with left and right paramedian incisions joined by a transverse incision that passed above the upper margin of the pubis, thus permitting upper lifting of the ventral abdominal wall. The animals were examined for the presence of adhesions on the bladder and the organs involved. Photographic documentation was obtained and the urinary bladder was resected. The surgical piece was opened through a longitudinal incision and inspected for the presence of stones and for the aspect of the mucosa. When stones were present, they were measured with a Digimatic electronic pachymeter (Mitutoyo Corporation) of millesimal sensitivity.

The bladders were fixed in 10% formalin and submitted to histopathological examination. Blocks were cut into 5-µm sections and stained with hematoxylin-eosin and the material was examined for epithelialization, presence, characteristics and intensity of the inflammatory reaction, necrosis, muscle regeneration, and presence of crystals and cysts.

Data were analyzed statistically by the Chi-square test for analysis of 2x2 tables. When the Cochran limitations were present, the exact Fisher test was used. The level of significance was set at 5% and the significant results are marked with an asterisk.

RESULTS

Two animals died of evisceration and 47 were left in the experiment. Free fluid was not observed and adherence of the mesosalpinx to the bladder was present in all groups at all times studied.

At times the dimensions of the bladder were increased and the presence of stones was observed when the organs were opened. Adipose tissue was present on the serosal surface over the stitches. The mucosal surface showed a depression at the level of the suture, with no other particular characteristics.

Stones were present only in the bladders of group C rats, i.e., in the bladders sutured with chromed catgut. The presence of calculi was observed starting on the 15th day. At that time, one stone was detected in the bladder of a group C animal and no stones were detected in group E animals (p = 0.5000). On the 30th day there were stones in 2 group C bladders and no stones in group E (p = 0.2776) and on the 50th day there were stones in 3 group C bladders and none in group E (p = 0.0833).

Stones were observed in 6 of the 13 animals in group C and in none of the 14 animals in group E from the 15th to the 50th day (p = 0.0058). Thus the frequency of bladders with stones in group C was 46.15%. Group C bladders containing stones are illustrated in Figures 1 and 2. On the 50th day, more than one stone was present in 3 group C animals, adhering to the sutures. The stones measured 0.51 to 9.23 mm in their widest diameter.

The microscopic findings were similar for the 2 groups. All bladders presented full epithelialization starting on the 7th day. An inflammatory reaction was present in both groups at similar frequency and with similar intensity. The inflammatory reaction was of the acute type, with a predominance of polymorphonuclear cells, and acute-chronic on the 3rd day. At the remaining times it showed chronic characteristics, with a predominance of lymphocytes and monocytes. Tissue necrosis was observed on the 3rd and 7th day in both groups, with no significnat difference. Muscle regeneration was observed in all groups and was more intense with time, with no significant differences between groups. Crystals were present only in group C starting on the 15th day (p = 0.0159). Cysts were detected at identical frequencies in both groups at all times studies.

DISCUSSION

The frequency of stone formation after urinary tract surgery is quite elevated. Suture material seems to make a considerable contribution to the etiology of formation of these stones. Despite a large number of disadvantages, absorbable sutures are generally thought to cause a lower incidence of stones^1-7 and the type most often employed is catgut^2-7. YUDOFSKY and SCOTT⁷ reported the appearance of stones when they used catgut starting on the 22nd day⁷. In the present study stones were present as early as on 15th day. MORRIS et al.⁴ found that 14% of the bladders in their study that had been sutured with chromed catgut contained stones. SAKAI et al.⁵ reported the absence of stones in bladders sutured with single catgut and an 81.2% incidence of stones after 6 weeks in bladders in which, in addition to using single catgut, they left a zinc mold.

In the present study, using chromed catgut we noted the presence of stones starting on the 15th day, with a 46.15% incidence in the bladders followed up for 50 days. It is interesting to note that bladders sutured with polyglecaprone 25 presented no stones during the same period of time. On the 50th day, 60% of the bladders had 2 stones, i.e., 1 stone per stitch, whose formation was related to them since the stones were adhering to the sutures.

Histologically, the course of the inflammatory reaction and of wall regeneration was similar for both sutures. However, crystals were observed only starting on the 15th day in sections of bladders sutured with chromed catgut (p = 0.0159), a fact that leads us to assume that stones would also form in these bladders. The absence of crystals or stones in bladders sutured with polyglecaprone 25 suggests that the lithogenesis potential of this suture is very low and that this will eventually become the preferred suture for the urinary tract. However, studies on the bladder of other animals are needed before drawing a definitive conclusion.

CONCLUSIONS

Analysis of the results obtained in the present experiment permits us to conclude that in the rat:

1) the tissue behavior of chromed catgut and polyglecaprone 25 sutures is similar,

2) catgut sutures produce lithiasis in 46.15% of the bladders sutured with it up to 50 days after surgery (p = 0.0058), and

3) polyglecaprone 25 sutures do not produce lithiasis up to 50 days after surgery.

REFERENCES

1. BARTONE, F.F. & STINSON, W. - Reaction of the urinary tract to polypropylene sutures. Invest. Urol., 14:44, 1976.

2. HANKE, P.R.; TIMM, P.; FALK, G.; KRAMER, W. - Behavior of different suture materials in the urinary bladder of the rabbit with special reference to wound healing, epithelization and crystallization. Urol. Int., 52:26-33, 1994.

3. HEALEY, G.B. & WARREN, M.M. - Stone formation on polypropylene suture. J. Urol., 121:836-7, 1979.

4. MORRIS, M.C.; BAQUERO, A.; REDOVAN, E.; MAHONEY, E.; BANNETT, A.D. - Urolithiasis on absorbable and non-absorbable suture materials in the rabbit bladder. J. Urol., 135:602-3, 1986.

5. SAKAI, A.T.; SROUGI, M.; SAKAI, Y.I.; MIES, S. - Modelo de litíase urinária em ratos. Acta Cir. Bras., 7:64-5, 1992.

6. TREVINO, R.; GOLDSTEIN, A.M.B.; VARTANIAN, N.L. - Vesical bladder stones formed around non-absorbable sutures and possible explanation for their delayed appearance. J. Urol., 122:849, 1979.

7. YODOFSKI, S. & SCOTT, F.B. - Urolithiasis on suture materials: its importance pathogenesis and prophylaxis ; an introduction to the monofilament teflon suture. J. Urol., 102;745-9, 1969.

¹

Work performed at the Division of Scientific Methodology and Clinical and Surgical Experimentation, Evangelical Faculty of Medicine of Parana (FEMPAR).

²

M.D.

³

Medical students

Publication Dates

• Publication in this collection
  18 Nov 1998
• Date of issue
  Jan 1998