Contrast-enhanced MR urography in the evaluation of renal transplants with urological complications

Effect of ureteral stricture in transplant kidney and choice of treatment on long-term graft survival

BACKGROUND

To explore the risk factors of ureteral stricture in transplant kidney and the clinical effects of different treatment methods.

METHODS

The 62 patients with transplant kidney ureteral stenosis as the experimental group, and another group of recipients from the same donor as the control group (n = 59 cases). The risk factors for ureteral stricture and the survival rate of transplant kidney were analyzed and compared. The 62 patients were divided into open operation, luminal operation, and magnetic compression anastomosis (MCA) operation group. The effect of the operation and the survival rate of transplant kidney among the three groups were compared.

RESULTS

In our study, we found that the above differences were statistically significant in clinical data such as gender, multiple donor renal arteries, history of infection, and delayed graft function (DGF) between the two groups (P < 0.05). Urinary tract infection and DGF history were the independent risk factors for the development of ureteral stricture. The open operation had the best treatment effect and the survival rate of the transplant kidney, followed by the MCA, the stricture recurrence rate in the luminal operation was the highest.

CONCLUSION

The ureteral stricture has a negative correlation with the long-term survival rate of the transplant kidney, the curative rate and long-term effect of open surgery are the best, stricture recurrence rate of luminal surgery is high, and it may require multiple operations in the future, the MCA is a new breakthrough and innovation in the treatment of ureteral stricture.

Diagnostic and therapeutic management of vesico-ureteral reflux in pediatric kidney transplantation-Results of an online survey on behalf of the European Society for Paediatric Nephrology

BACKGROUND

Vesico-ureteral reflux (VUR) is considered to be a risk factor for recurrent febrile urinary tract infections and impaired renal transplant survival.

METHODS

An online survey supported by the European Society for Paediatric Nephrology was designed to evaluate current management strategies of VUR in native and transplanted kidneys of recipients aged <18 years.

RESULTS

Seventy-three pediatric transplant centers from 32 countries contributed to the survey. All centers performed urological evaluation prior to pediatric kidney transplantation (KTx) with subsequent interdisciplinary discussion. Screening for VUR in native kidneys (30% in all, 70% in selected patients) led to surgical intervention in 78% (11% in all, 89% in selected patients) with a decided preference of endoscopic intervention over ureterocystoneostomy. Following KTx, continuous antibiotic prophylaxis was applied in 65% of the patients and screening for allograft VUR performed in 93% of selected patients. The main management strategies of symptomatic allograft VUR were continuous antibiotic prophylaxis (83%) and surgical treatment (74%) (endoscopic intervention 55%, redo ureterocystoneostomy 26%).

CONCLUSIONS

This survey demonstrates the high variability in the management of VUR in pediatric KTx recipients, points to knowledge gaps, and might serve as a starting point for improving the care for patients with VUR in native and transplanted kidneys.

Contrast-enhanced magnetic resonance urography at 3T: clinical feasibility

OBJECTIVE

The objective of this study was to assess the feasibility of performing diagnostic-quality contrast-enhanced excretory magnetic resonance urography (eMRU) at 3T, examining both image quality and diagnostic accuracy for a range of urinary tract abnormalities.

METHODS

The diuretic-enhanced 3T eMRUs of 37 patients were reviewed to assess for the diagnostic conspicuity of urinary tract abnormalities, extent of urinary tract visualization on excretory images, and presence and severity of image artifacts.

RESULTS

Excretory images allowed greater than 75% visualization in 90.8% of renal collecting systems, 90.8% of ureters, and 82.3% of bladders. Common artifacts included susceptibility (21.3%), contrast mixing (21.3%), patient motion (20.4%), signal inhomogeneity (19.4%), and peristaltic motion (17.6%). Severe artifacts occurred in 21.6% of studies. Five of 8 urothelial neoplasms were detected, with 1 false-positive lesion in the bladder. Urolithiasis was correctly diagnosed in 7 of 9 patients.

CONCLUSIONS

Although image artifacts can hamper eMRU at 3T, initial results are promising for evaluation of the urothelium.

MR urography: techniques and clinical applications

Magnetic resonance (MR) urography comprises an evolving group of techniques with the potential for allowing optimal noninvasive evaluation of many abnormalities of the urinary tract. MR urography is clinically useful in the evaluation of suspected urinary tract obstruction, hematuria, and congenital anomalies, as well as surgically altered anatomy, and can be particularly beneficial in pediatric or pregnant patients or when ionizing radiation is to be avoided. The most common MR urographic techniques for displaying the urinary tract can be divided into two categories: static-fluid MR urography and excretory MR urography. Static-fluid MR urography makes use of heavily T2-weighted sequences to image the urinary tract as a static collection of fluid, can be repeated sequentially (cine MR urography) to better demonstrate the ureters in their entirety and to confirm the presence of fixed stenoses, and is most successful in patients with dilated or obstructed collecting systems. Excretory MR urography is performed during the excretory phase of enhancement after the intravenous administration of gadolinium-based contrast material; thus, the patient must have sufficient renal function to allow the excretion and even distribution of the contrast material. Diuretic administration is an important adjunct to excretory MR urography, which can better demonstrate nondilated systems. Static-fluid and excretory MR urography can be combined with conventional MR imaging for comprehensive evaluation of the urinary tract. The successful interpretation of MR urographic examinations requires familiarity with the many pitfalls and artifacts that can be encountered with these techniques.

Magnetic resonance urography in pediatric urology

PURPOSE OF REVIEW

Magnetic resonance urography (MRU) has emerged as a powerful diagnostic tool in the evaluation of the pediatric genitourinary tract. The purpose of this review is to familiarize the reader with the basic techniques, strengths and limitations, as well as the current and potential future applications of MRU in pediatric urology.

RECENT FINDINGS

MRU can provide detailed anatomical information and assess renal function and drainage in a single study. MRU does not employ ionizing radiation and may be utilized in patients with iodine-based contrast allergy or impaired renal function. MRU has been most often applied to the evaluation of hydronephrosis and provides valuable insight into a wide range of obstructive uropathies. MRU was shown to be superior to renal scintigraphy for the diagnosis of pyelonephritis and renal scarring. The use of MRU for the assessment of urolithiasis and vesicoureteral reflux is limited and technical refinements are required. Potential future applications include fetal MRU, virtual endoscopy, and MRU-guided procedures. The development of new contrast agents and new image-processing software will further enhance the diagnostic potential of MRU in pediatric urology.

SUMMARY

MRU is currently thought of as a problem-solving tool to define anatomy and function when conventional methods fall short. This technique is likely to emerge as the imaging modality of choice for children with complex genitourinary pathology.

Renal transplant failure due to urologic complications: Comparison of static fluid with contrast-enhanced magnetic resonance urography

PURPOSE

Postrenal reasons of renal transplant failure can be assessed by magnetic resonance urography. This study was designed to retrospectively compare the diagnostic accuracy of static fluid (T2-)MRU compared to contrast enhanced (CE-)MRU in patients with renal transplant failure.

MATERIAL AND METHODS

Thirty-five consecutive patients (14 female, 21 men; mean age 48.6 years) with renal transplant failure and sonographically detected hydronephrosis were examined both with T2-MRU as well as CE-MRU resulting in 39 MRU examinations. MRU was performed both using T2-weighted HASTE-sequence (T2-MRU) as well as Gadolinium-enhanced 3D-FLASH-sequence (CE-MRU) on a 1.5-T clinical MRI scanner (Magnetom Vision, Siemens Medical Solutions). Subjective image quality of resulting maximum intensity projection was assessed in consensus by two readers blinded to the final diagnosis, using a five point scale. MRU findings were correlated to sonography, operative results or clinical follow up.

RESULTS

CE-MRU yielded a sensitivity of 85.7% (T2-MRU 76.2%), and a specificity of 83.3% (T2-MRU: 73.7%), however statistical significance was not reached. The subjective image quality was significantly better in CE-MRU.

CONCLUSIONS

Only concerning subjective image quality CE-MRU proved superior to T2-MRU. Yet, there was no significant difference in diagnostic accuracy between T2- and CE-MRU. Thinking of incipient nephrogenic systemic fibrosis, T2-MRU can be used as reliable alternative in patients with decreased renal transplant function due to urological complications.