Pathophysiological aspects of ureterorenoscopic management of upper urinary tract calculi.

PURPOSE OF REVIEW: Indications for ureterorenoscopy are expanding without hard scientific evidence to support its efficacy. Therefore, it is extremely important to focus on potential harmful effects of the procedure itself. This review explores how physiology of the upper urinary tract reacts to ureterorenoscopy, potentially translating into harmful effects, and how such pathophysiological processes may be minimized. RECENT FINDINGS: Complications to ureterorenoscopy and postoperative pain seem to be related to intrarenal pressure and/or access. Mean intrarenal pressures in the range of 60-100 mmHg during ureterorenoscopy without access sheaths have been measured, thus by far exceeding the threshold for intrarenal backflow, potentially resulting in septic complications. Intrarenal pressure may be reduced by use of ureteral access sheaths, which, however, may cause ureteral damage due to the limited size of the ureter and strain-induced ureteral contractions (peristalsis). Different receptor types modulate this peristaltic activity. ß-receptor agonists have been investigated in animal and human trials for the purpose of relaxing the ureter. In randomized, placebo-controlled trials in pigs and humans, usage of the ß-receptor agonist isoproterenol in the irrigation fluid has shown a potential for reducing both intrarenal pressure and ureteral tone during ureterorenoscopy. SUMMARY: Upper urinary tract physiology has unique features that may be pushed into pathophysiological processes by the unique elements of ureterorenoscopy: access and irrigation. Pharmacological ureteral relaxation during ureterorenoscopy deserves further attention with regard to reducing complications and postoperative pain.

Bosniak classification system: inter-observer and intra-observer agreement among experienced uroradiologists.

BACKGROUND: The Bosniak classification is a diagnostic tool for the differentiation of cystic changes in the kidney. The process of categorizing renal cysts may be challenging, involving a series of decisions that may affect the final diagnosis and clinical outcome such as surgical management. PURPOSE: To investigate the inter- and intra-observer agreement among experienced uroradiologists when categorizing complex renal cysts according to the Bosniak classification. MATERIAL AND METHODS: The original categories of 100 cystic renal masses were chosen as "Gold Standard" (GS), established in consensus by two experienced uroradiologists. Three experienced uroradiological readers were blinded from the previous CT reports. Weighted κ was calculated to assess agreement, defined as: fair, 0.21-0.40; moderate, 0.41-0.60; good, 0.61-0.80; and very good, 0.81-1.00. RESULTS: For readers the distribution of correctly classified lesions were as follows: BI, 95-100%; BII, 59-93%; BIIF, 54-92%; BIII, 58-95%; and B IV, 77-100% for the first review. Weighted κ for inter-observer/intra-observer variation was for Reader A: 0.85/0.99, Reader B: 0.97/0.99, and Reader C: 0.98/0.99, (P ≤ 0.001). CONCLUSION: According to the calculated weighted κ all readers performed "very good" for both inter-observer and intra-observer variation. Most variation was seen in cysts catagorized as Bosniak II, IIF, and III. These results show that radiologists who evaluate complex renal cysts routinely may apply the Bosniak classification reproducibly.

Can the CT planning image determine whether a kidney stone is radiopaque on a plain KUB?

Almost all kidney stones are CT positive. Before a CT scan can be done a CT planning image (CTI) is generated in order to select the exact scanning area. The CTI looks approximately like a normal kidney-ureter-bladder abdominal radiography (KUB) but with reduced quality. It has been used as a guide, assuming that if the kidney stone could be seen on the CTI the kidney stone also would be visible on a conventional plain KUB (radiopaque). From the perspective of diagnosis and treatment as well as follow-up it is of importance to know whether a kidney stone is radiopaque or not. The aim of this study was to evaluate whether the CTI actually can predict radiopacity. CT scans and corresponding KUB's were analysed in 76 consecutive kidney stone patients. The CT scan and the KUB were performed on the same day. All patients were examined with the same CT scanner (64 slice GE light speed VCT). Three radiologists evaluated the images in plenum. The following was recorded regarding the kidney stones: X-ray positive (radiopaque on KUB), CTI positive (radiopaque on CTI), location (a kidney, b upper two-thirds of ureter and c lower one-thirds of ureter including the bladder), size and Hounsfield units (HU). We also measured the patient's 'anterior-posterior depth' (APD) at the kidney stone level in axial plane, and whether the stone was homogeneous/inhomogeneous. 54 of the 76 patients (71%) had radiopaque stones on KUB. 43 (57%) of these also could be seen on the CTI, resulting in a positive predicting value (PPV) of 100% and a negative predictive value (NPV) of 67%. In the 54 KUB positive kidney stones the mean kidney stone diameter was 7 mm (2-30 mm), mean HU's 1,007 (294-1,782 HU), location: a:32, b:9 and c:13 patients. APD was mean 23.6 cm (13-39 cm). In the KUB positive and CTI negative kidney stones (11 patients) mean kidney stone diameter was 4 mm (2-9 mm), mean HU's 742 (294-1,253 HU), location: a:32, b:9 and c:13 patients. APD in this group was mean 26.1 cm (13-37 cm). If the kidney stone can be seen on the CTI it is also visible on a plain KUB (PPV 100%). The CTI do, however, underestimate the radiopacity of a stone on a plain KUB (NPV 67%). Kidney stone HU > 742, stone location in the kidney and proximal ureter and APD < 26 cm independently predict agreement between CTI and KUB with regard to radiopacity.

Retrograde ureteroscopic holmium laser endopyelotomy in a selected population of patients with ureteropelvic junction obstruction.

OBJECTIVE: Significant controversy remains concerning the best way to treat ureteropelvic junction obstruction (UPJO). This study evaluates subjective and objective outcomes of retrograde holmium laser endopyelotomy in a selected population with UPJO. MATERIAL AND METHODS: Forty-seven patients with UPJO were referred to retrograde endopyelotomy between April 2004 and March 2007. Patients with a very large pelvis, a high insertion of the ureter, a renal split function below 20% or a long (>2 cm) stenosed ureteropelvic segment, and patients younger than 18 years were not selected for endopyelotomy, but subjected to laparoscopic pyeloplasty. Renal function was estimated on renal diuretic scan before and after surgery with a mean renographic follow-up of 35 weeks. Subjective results were based on questionnaires which were returned from 44 patients with primary (n=37) or secondary (n=7) obstruction (mean follow-up 110 weeks). Success criteria were defined as symptom relief and improved or preserved renal function. RESULTS: Twenty-nine patients (66%) experienced complete symptom resolution and 10 patients (23%) had significant symptom improvement (i.e. no need for pain-killing medication). Five patients (11%) had unchanged symptoms. No difference in postoperative renal function was observed between these three groups of patients. The differences between preoperative and postoperative renal function were non-significant in each group. No major complications were observed. Five patients (11%) were referred to retreatment owing to unchanged symptoms. CONCLUSION: Retrograde ureteroscopic endopyelotomy is a safe and effective treatment option in patients with primary and secondary UPJO when selected properly.