Non-traumatic bladder rupture showing less than 10 Hounsfield units of ascites

The diagnostic challenge of non-traumatic bladder rupture: a pictorial essay

Non-traumatic bladder rupture (NTBR) is relative rare pathology including spontaneous rupture and iatrogenic injury. As increasing the medical intervention for the pelvic malignancy or elderly population, NTBR will be encountered more frequently. There are few previous studies summarizing the imaging features of NTBR. We reviewed imaging characteristics of 18 previous cases of NTBR experienced. In addition, 3 presentative cases that can be a pitfall to differentiate from NTBR. The aim of this article is to clarify the key CT findings of NTBR and its pitfalls.

Need for routine preoperative insertion of indwelling urinary catheter prior to endovascular repair of abdominal aortic aneurysm

OBJECTIVE

Evaluate outcomes following urinary catheter (UC) vs. no urinary catheter (NUC) insertion in elective endovascular repair (EVAR) of abdominal aortic aneurysm (AAA).

METHODS

Retrospective record review of all elective EVAR at a university affiliated medical center over a 5-year period. Statistical analysis included Chi Sq, Independent Student T Test.

RESULTS

Six surgeons performed 272 elective EVAR. Three surgeons preferred selective insertion of indwelling UC, such that 86 (32%) EVAR were completed without indwelling urinary catheters (NUC). Differences between NUC vs. UC included; male: (86% vs. 70%; P= 0.004), CAD: (45% vs.33%; p= .046), conscious sedation: (36% vs. 8%; P < 0.001), bilateral percutaneous EVAR (PEVAR): (100% vs. 90%; P= 0.01), within Proglide^TM IFU guidelines (87% vs 75%; P= .05), major adverse operative event (MAOE): (3.5% vs. 10%; P= 0.05) and mean operative time (185 ± 73 vs. 140 ± 37; P < 0.001). Intra-operative catheterization was never required among NUC. Postoperative adverse urinary events (AUE) were more common among UC (11.4% vs. 8.1%; P= 0.41); with longer times to straight catheterization/reinsertion (1575 ± 987 vs 522 ± 269 minutes; P= 0.015) and lower likelihood of eligibility for same day discharge (SDD); (41% vs.59%; P= 0.008). Ineligibility for SDD was due to AUE in 18% of UC patients.

CONCLUSION

Selective preoperative UC insertion should be considered for EVAR, with particular consideration to no preoperative catheterization in men meeting Proglide IFU. Adverse urinary events occurred less frequently among NUC and were identified/ treated earlier. Moreover, AUEs were the most common reason for potential SDD ineligibility among UC patients. Selective policies may facilitate SDD.

A novel use of attenuation value (Hounsfield unit) in non-contrast CT: diagnosis of pyonephrosis in obstructed systems

PURPOSE

To evaluate the predictive value of attenuation value (HU) in renal pelvis urine for detecting renal pelvis urine culture (RPUC) positivity in obstructed urinary systems.

METHODS

The study group consisted of patients who had nephrostomy insertion performed because of obstructed system and suspicion of pyonephrosis and percutaneous nephrolithotomy (PCNL) patients who had obstructed calculi. Group 1 consisted of RPUC positive 28 patients during nephrostomy insertion or needle access in PCNL and group 2 consisted of 23 patients with negative RPUC. RPUC results and non-contrast computed tomography measurements [Hounsfield unit (HU)] were compared between group 1 and group 2. A cut-off value was determined for HU. All patients were grouped according to whether they were above or below this value.

RESULTS

The median HU calculated from the renal pelvis was - 8.5 (range - 29/- 1) and 10 (range- 4/+ 17) (p < 0.001) in group 1 and group 2, respectively. The cut-off value of HU that predicted positive RPUC was 0. Sensitivity and specificity of HU when considering this cut-off value were 100% and 96%, respectively (p < 0.001). Whereas RPUC positivity was found in 96.6% (28/29) of patients with HU < 0, there were no patients with HU > 0 where RPUC positivity was detected (p < 0.001).

CONCLUSION

In this cohort, we found that HU of the urine in the renal pelvis can be used to predict RPUC positivity.

A novel use of attenuation value (Hounsfield unit) in non-contrast CT: diagnosis of urinary tract infection

PURPOSE

To investigate the utility of attenuation value (Hounsfield unit) of the filled bladder on computed tomography (CT) images and the association of these values with simultaneously obtained urine culture results.

METHODS

Between January 2016 and December 2017, retrospective data of 58 patients who were admitted to the emergency department for various symptoms were examined. All patients were evaluated with urine dipstick microscopy, urine culture, and abdominal CT simultaneously. Group 1 consisted of patients with positive urine culture (n = 28) and Group 2 consisted of patients with negative urine culture (n = 30). The attenuation value of urine in the bladder at the level of the bladder trigone was measured inside an elliptical drawing covering all the urine inside the bladder excluding the bladder wall on axial non-contrast CT images. The predictive value of this calculated attenuation value for urine culture positivity was evaluated.

RESULTS

The median attenuation value was - 6 (range - 17.8 to + 11) and 12 (range 0-32) in group 1 and group 2 (p < 0.001). According to cut-off value of - 1 attenuation value, sensitivity for predicting urine culture positivity was 92.9%, whereas specificity was 100% (AUC: 0.977 p < 0.001). Urine culture was positive in all of the 26 patients with attenuation value < - 1, whereas only two of the 32 patients with attenuation value > - 1 had urine culture positivity (p < 0.001 OR 14).

CONCLUSION

The attenuation value of the urine in the defined area of the bladder may aid in the diagnosis of urinary infection with high sensitivity and specificity and without any additional cost.

Estimation of Hounsfield unit conversion parameters for pelvic CT images

Linear scaling is used to convert raw computed tomography (CT) pixel values into Hounsfield units corresponding to different tissue values. Analysis of a benchmarking study, presented here, where the same CT scan was imported into and then exported from multiple radiotherapy treatment planning systems, found inconsistencies in HU scaling parameter values exported along with the images, particularly when images were exported using the Radiation Therapy Oncology Group format. Several methods of estimating conversion parameters, based on estimating pixel values corresponding to air and water within the image, for pelvic CT images from a large multi-centre trial were compared against original Digital Imaging and Communications in Medicine export parameters. In general using the mean of a sample region at the centroid of the bladder to estimate the value of water was more accurate than using the minimum or maximum or a single value at the centroid. Accuracy of methods of air estimation tested were dependent in part on features of the CT scanners and treatment planning systems, making it difficult to pick one method as superior that was independent of scanner and treatment planning system type. Based on the above analysis, methods for estimating air and water were selected for use in performing linear scaling of a set of pelvic CT images prior to their use in an interpatient image registration application. The selected methods were validated against a more recent and homogeneous dataset. Estimation error was found to be much lower within the validation set.