suprapubic cystostomies are performed for a variety of indications that require either temporary or permanent placement of suprapubic catheters . the placement of percutaneous suprapubic catheters using a punch trocar technique involves some risks and should not be considered an innocuous procedure . among the wide variety of complications , the most serious complication is bowel injury . bowel injuries include perforation of the ileum [ 2 - 6 ] and colon   as well as small bowel obstruction and volvulus [ 3,7 - 9 ] . because the percutaneous tract is blindly made at 3 to 4 cm above the symphysis pubis in the midline , the risk of bowel injury is constantly present . therefore , before a percutaneous cystostomy is performed , especially if there has been prior abdominal or pelvic surgery , or if the bladder is not full , it is strongly advised to consider using ultrasound for the detection of interposed bowel along the percutaneous tract , because the bowel may be in close proximity to the tract . however , that method does not totally guarantee the nonexistence of bowel crossing the tract , because it may be difficult for the ultrasound to detect a collapsed bowel . despite this clinical setting , there has been little study of the risk factors for bowel injury associated with percutaneous cystostomy . this may be largely due to the practical limitations in demonstrating bowel injury before and after suprapubic cystostomy . in this study , we investigated the risk factors for possible bowel interposition between the bladder and the skin at the routine puncture site of suprapubic cystostomy by computed tomography ( ct ) , assuming that a hypothetical suprapubic cystostomy was performed . we retrospectively reviewed 795 consecutive adult abdominopelvic ct scans performed for various reasons in our hospital from september to october 2009 . among them , we selected 226 patients whose bladders were distended more than 6 cm above the upper margin of the symphysis pubis . their medical charts at the time of the ct scan were analyzed retrospectively . through the ct scan images , we determined whether the bowel was interposed between the urinary bladder and the skin at a point along the midline of the abdomen , 3 cm above the upper margin of the symphysis pubis ( fig . we investigated whether the age , gender , height , history of radical pelvic surgery , or the distance between the upper margin of the symphysis pubis and the umbilicus influenced the possibility of bowel interposition between the bladder and the skin at the suprapubic puncture site . statistical analyses were performed by applying the chi - square test and multiple logistic regression using commercially available software spss ver . 14.0 ( spss inc . , chicago , il , usa ) . a p - value of < 0.05 was considered statistically significant . the patients ' mean age was 63 years ( range , 26 - 84 years ) . among the 226 patients , 22 ( 9.7% ) had undergone radical pelvic surgery previously . the mean distance between the upper margin of the symphysis pubis and the umbilicus was 14.4 cm ( range , 7.2 - 21.0 cm ) ( table 1 ) . the univariate analysis showed that sex ( female , p=0.028 ) , obesity ( body mass index [ bmi]25 kg / m , p=0.006 ) , a positive history of radical pelvic surgery ( p<0.001 ) , and a short distance ( 11 cm , p=0.016 ) between the upper margin of the symphysis pubis and the umbilicus were significantly correlated with bowel interposition at the routine suprapubic puncture site ( table 2 ) . among the 22 patients who had a radical pelvic operation , 20 had lower anterior resection , and the other 2 had segmental resection of the rectum due to rectal or colon cancer . in the multivariate analysis , obesity ( p=0.019 ) , a positive history of pelvic surgery ( p=0.001 ) , and a short distance ( p=0.016 ) between the upper margin of the symphysis pubis and the umbilicus were independent predictors for the bowel passing through the percutaneous tract ( table 3 ) . in our multivariate analysis , obesity , a history of pelvic surgery , and a short distance between the symphysis pubis and the umbilicus were independent predictors of bowel interposition through the percutaneous suprapubic cystostomy tract . prior pelvic surgery is a well known risk factor for bowel injury after percutaneous cystostomy . after a pelvic operation , the bowel can move downward through the opened space of retzius , and associated postoperative adhesions may develop between the anterior abdominal wall and peritoneum , both of which may increase the probability of bowel injury during a suprapubic cystostomy procedure . in our study , 9 of the 22 patients ( 40.9% ) who had radical pelvic surgery had an interposed bowel at the routine suprapubic cystostomy tract , whereas 17 of the 204 ( 8.3% ) without a history of pelvic surgery had bowel interposition . all of the prior pelvic surgeries were opened lower anterior resections because of rectal or colon cancer . obesity has also been considered as a risk factor for bowel injury when performing a suprapubic cystostomy because it is difficult to localize the bladder in such patients . our study presented the novel hypothesis that obesity itself is an independent predictor for bowel interposition through the cystostomy tract . we do not know the exact reason for the above finding , but assumed that because obese patients have relatively larger bowel contents as well as omental fat , the bowel tended to move downward in the limited intra - abdominal space . similarly , the correlation of bowel interposition with a short distance between the symphysis pubis and the umbilicus can be understood in the same manner . as we mentioned above , 8.3% of the patients without a history of pelvic surgery had interposition of the bowel through the routine cystostomy tract . this was much higher than the general consensus , because the placement of a suprapubic tube for urinary diversion is generally an uneventful procedure . for the safe placement of a suprapubic catheter , the most important point is the full distension of the urinary bladder before the procedure . in this study , we considered bladder distension more than 6 cm above the upper margin of the symphysis pubis as a cutoff point on the basis of data from voiding cystourethrograms performed in 20 adult patients with neuropathic bladder . in their films , the average distance between the symphysis pubis and the upper margin of the cystogram at full bladder distension was 6.2 cm . we therefore defined 6 cm as the assumptive point of full bladder distension . because a fully distended bladder in a normal patient without neuropathic bladder can rise more than 6 cm above the symphysis pubis , it seemed likely that our results overdetected the bowel interposition through the cystostomy tract . however , we should take into consideration that , clinically , the complications of suprapubic cystostomy are commonly seen in small capacity bladder with neuropathic deficits . in the practical setting , although a small capacity bladder itself would be the major risk factor for complications in performing suprapubic cystostomy , the retrospective nature of our study could not reveal that relationship . the high exclusion rate ( 71.6% ) was another major pitfall of this study , because patients who underwent abdominopelvic ct scan were not instructed to endure the urge to urinate . to our knowledge , this is the first study that attempted to reveal the risk factors of possible bowel injury related to suprapubic cystostomy , even though the study was performed by an indirect approach . this study demonstrated the risk factors for the bowel being interposed at the routine suprapubic puncture site as detected by ct scan . when performing a suprapubic cystostomy , extreme caution is needed to avoid possible bowel injury in patients who are obese , who have had previous radical pelvic operations , and who have a short distance ( 11 cm ) between the upper margin of the symphysis pubis and the umbilicus .
purposethe most serious complication of suprapubic cystostomy is bowel injury . by computed tomography ( ct ) , we investigated the risk factors of possible bowel interposition through the percutaneous suprapubic cystostomy tract.materials and methodsfrom september to october 2009 , we consecutively reviewed 795 abdominopelvic ct scans of adult patients performed for various reasons in our hospital . from these scans 
 , we selected the films wherein the urinary bladder was distended more than 6 cm above the symphysis pubis . 
 we then determined whether the bowel was interposed between the bladder and the skin at the routine puncture site of suprapubic cystostomy ( the midline of the abdomen 3 cm above the upper margin of the symphysis pubis ) . 
 we analyzed which factors influenced the possibility of the bowel being interposed between the bladder and the skin at the suprapubic puncture site.resultsa total of 226 ct ( 148 males , 78 females ) scans were selected . 
 the mean patient age was 63 years ( range , 26 - 84 years ) . 
 the mean distance between the upper margin of the symphysis pubis and the umbilicus was 14.4 cm ( range , 7.2 - 21.0 cm ) . in the multivariate analysis , obesity , a positive history of radical pelvic surgery , and a short distance ( 11 cm ) between the symphysis pubis and the umbilicus had significant correlations with bowel interposition in the assumed tract.conclusionswhen performing a suprapubic cystostomy , extreme caution is needed to avoid possible bowel injury in patients who are obese , had a previous radical pelvic operation , or have a short distance between the upper margin of the symphysis pubis and the umbilicus .