The pathophysiology of ureteral obstruction

A novel in vivo model of ureteral fibrosis induced by calcium oxalate beads in C57BL/6J mice

The global incidence of ureteroliths in humans is increasing, particularly posing a problem in developed countries. The most common stone type is calcium oxalate, which is associated with a high recurrence rate. In veterinary medicine, stones are the most common cause of ureteral obstruction in cats, accounting for 72-87% of cases. In cats, stones cause irreversible ureteral damage, necessitating stone treatment as well as ureteral therapy. However, the mechanisms underlying the ureteral damage caused by stones remain unclear. Therefore, this study aimed to create a mouse model suitable for studying the ureteral fibrosis caused by oxalate stones by artificially embedding calcium oxalate in the ureter. Pathological tissue analysis was used to compare normal ureters without ligation and ureters with sham or oxalate bead implantation. The ureters of the sham and oxalate bead groups showed granulation tissue formation, transitional epithelium exfoliation, and densely packed connective tissue in the proprietary and muscle layer regions. Particularly in the oxalate bead group, infiltration of degenerated neutrophils, presence of foreign body giant cells, and hyperplasia of the transitional epithelium were observed. The proportion of fibrosis was higher in the oxalate group than in the sham group. Overall, this mouse model created using oxalate bead implantation has the potential to efficiently induce ureteral obstruction. This mouse model is expected to be used for elucidating the molecular mechanisms of ureteral fibrosis and evaluating therapeutic drugs in future.

GSDME-mediated pyroptosis promotes inflammation and fibrosis in obstructive nephropathy

Renal tubular cell (RTC) death and inflammation contribute to the progression of obstructive nephropathy, but its underlying mechanisms have not been fully elucidated. Here, we showed that Gasdermin E (GSDME) expression level and GSDME-N domain generation determined the RTC fate response to TNFα under the condition of oxygen-glucose-serum deprivation. Deletion of Caspase-3 (Casp3) or Gsdme alleviated renal tubule damage and inflammation and finally prevented the development of hydronephrosis and kidney fibrosis after ureteral obstruction. Using bone marrow transplantation and cell type-specific Casp3 knockout mice, we demonstrated that Casp3/GSDME-mediated pyroptosis in renal parenchymal cells, but not in hematopoietic cells, played predominant roles in this process. We further showed that HMGB1 released from pyroptotic RTCs amplified inflammatory responses, which critically contributed to renal fibrogenesis. Specific deletion of Hmgb1 in RTCs alleviated caspase11 and IL-1β activation in macrophages. Collectively, our results uncovered that TNFα/Casp3/GSDME-mediated pyroptosis is responsible for the initiation of ureteral obstruction-induced renal tubule injury, which subsequentially contributes to the late-stage progression of hydronephrosis, inflammation, and fibrosis. This novel mechanism will provide valuable therapeutic insights for the treatment of obstructive nephropathy.

Is robotic-assisted radical cystectomy (RARC) with intracorporeal diversion becoming the new gold standard of care?

BACKGROUND

Totally intracorporeal robotic-assisted radical cystectomy (RARC) has perceived difficulties compared to open radical cystectomy (ORC). As the technique is increasingly adopted around the world, the benefits of RARC with intra- or extracorporeal urinary diversion or ORC for the patients are still unclear. In this article, we consider the current evidence for this issue.

METHODS

We assessed two questions through using expert opinion and the medical literature: (A) Is RARC better than ORC for removing the cancer surgery and outcome? (B) Is RARC better than ORC for the urinary diversion?

OUTCOMES

(A) RARC is better than ORC for shorter length of stay, blood loss and complication rates. (B) Intracorporeal orthotopic neobladder may have a significant physiological and surgical benefit to the patient recovery.

CONCLUSIONS

RARC with total intracorporeal reconstruction has potential benefits to the patient. We recommend that all surgeons document patient-related outcome measures, urodynamics and enhanced recovery protocols for cystectomy patients to help us understand the real improvements within bladder cancer surgery and reconstruction.

Syndrome de levée d'obstacle : physiopathologie et prise en charge

RéSUMé: Le syndrome de levée d'obstacle est une polyurie massive faisant suite au traitement d'une insuffisance rénale obstructive. Les mécanismes physiopathologiques sont multiples : un état de surcharge hydrique qui dépend du caractère complet ou incomplet de l'obstacle, des anomalies tubulaires (atteinte de la capacité de dilution et de concentration des urines, diminution de la réabsorption du sodium, fuites de potassium, troubles de l'acidification des urines, insensibilité des cellules tubulaires à l'hormone antidiurétique), ainsi que des facteurs biochimiques et immunologiques sont mis en jeu. La levée d'un obstacle nécessite une surveillance clinique et biologique stricte (diurèse horaire, état hémodynamique, état d'hydratation, créatininémie, urémie, ionogramme sanguin). Le traitement a pour but d'éviter les troubles hémodynamiques et métaboliques graves, et repose sur le principe de la compensation des pertes hydroélectrolytiques.

Voie excrétrice supérieure : physiologie, physiopathologie des obstructions et explorations fonctionnelles

The urine is transported from the renal papilla to the bladder through the upper urinary tract which allows this transport to be safe and comfortable, i.e., without any risk or pain for the kidney. This active transport depends on the smooth muscle contractile properties. The upper urinary tract is totally autonomous; this feature allows the preservation of its function after renal transplantation. However, despite its accessory role, the autonomous nervous system can modulate its activity. Upper urinary tract obstruction involves adaptative mechanisms which are different depending on the type (acute, chronic, acquired or congenital) of obstruction. Functional evaluations of the upper urinary tract are aimed at identify the urine transport conditions and the relationship between obstruction and clinical conditions such as hydronephrosis, pain or impaired renal function.

Partial unilateral ureteral obstruction in rats

This review comprises an overview of the current knowledge on experimental partial unilateral ureteral obstruction (PUUO) and a summary of our latest original experimental PUUO studies in rats. Neonatal PUUO is the type of obstruction that is most often encountered in pediatric clinical practice. However, the pathogenesis of PUUO is still incompletely understood. Most of our knowledge on PUUO has been derived from experimental studies in a variety of animal models. Although progress has been made, the natural history of congenital hydronephrosis is still incompletely described. The effects on kidney functions of long-term urinary tract obstruction, especially PUUO, have been less intensively studied. Recently, we created models with mild and severe PUUO in young rats by embedding the upper one fourth or the upper two thirds of the left ureter into the psoas muscle, respectively. Thereafter, the technique was used to create mild and severe PUUO in newborn rats and magnetic resonance imaging studies showed that both mild and severe obstruction caused a time-dependent decrease in renal blood flow. Compensatory increase in total kidney volume and renal vein blood flow in contralateral non-obstructed kidneys was not detectable when functional deterioration in the partially obstructed kidneys was present. Finally, we investigated the dynamic changes in renal relative signal intensity (RSI) of gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) using magnetic resonance imaging in rats with partial, complete unilateral ureteral obstruction and sham-operated controls. The results showed that changes in Gd-DTPA RSI are compatible with the known physiological and anatomical changes in kidneys in response to ureteral obstruction and useful for distinguishing an obstructed from a non-obstructed collecting system and also for differentiating a partially obstructed from a completely obstructed collecting system.

Perioperative changes in serum creatinine after gynecologic surgery

OBJECTIVE

The purpose of this study was to prospectively determine the normal range of postoperative changes in serum creatinine levels when bilateral ureteral patency was confirmed by cystoscopy.

STUDY DESIGN

A total of 187 consecutive patients who had undergone major gynecologic surgery were evaluated prospectively. All patients had undergone perioperative cystoscopy to evaluate for ureteral patency, and creatinine levels had been determined before and 24 hours after surgery.

RESULTS

The mean change in serum creatinine level was 0.01 mg/dL, and the changes for the central 95% ranged from -0.2 to 0.3 mg/dL. With a previously defined cutoff value of an increase of >0.2 mg/dL after operation to indicate ureteral obstruction, specificity and negative predictive values (when compared with cystoscopic findings) were 98% and 100%, respectively.

CONCLUSION

Creatinine levels change minimally during the immediate postoperative period in the absence of ureteral compromise. If bilateral ureteral patency was demonstrated after operation in our population, creatinine level elevations were always <0.3 mg/dL.

Acute ureteral obstruction and glomerulotubular function in rats

Urinary tract obstruction is a common cause of acute renal failure (ARF). During unilateral ureteral obstruction (UUO) arteriolar vasoconstriction, increase in tubular pressure, and ultrafiltrate retrodiffusion occur. We studied renal function of rats with surgical UUO for 24 hr. After this period of UUO, the contralateral kidney was removed and the right ureter was deobstructed. The control uninephrectomized group consisted of normal rats submitted to left uninephrectomy (UNx). Functional studies were performed 12 and 24 hr, and 7 days after deobstruction and UNx. We measured creatinine clearance, and fractional excretion of sodium and lithium. Using conventional formulas we calculated fractional proximal and distal sodium reabsorption. Initially we observed a reduction in glomerular filtration rate (GFR) after deobstruction (12 and 24 hr). However, after 7 days, the GFR was significantly higher in deobstructed rats than in controls (340.3 +/- 18.3 vs. 286.4 +/- 9.3 microL/min/100 g, p < 0.01). The dry kidney weight was also increased in these rats. The fractional sodium excretion was increased in deobstructed rats, mainly in early studies (12 and 24 hr). Whereas fractional proximal reabsorption was reduced in both groups, the fractional distal reabsorption was significantly decreased in the deobstructed group compared to UNX controls (93.9 +/- 0.9 vs. 98.9 +/- 0.1% after 24 hr, p < 0.01). Our data showed that UUO influenced both glomerular and tubular functions. A salient finding was the overcorrection of GFR 7 days after deobstruction. The renal release of hormones and growth factors could mediate these alterations in renal function through their vascular, tubular, and proliferative actions.

Contemporary management of ureteral stones

The management of ureteral stones has undergone revolutionary changes in the past 15 years. The parallel advances in extracorporeal shock wave lithotripsy, percutaneous and retrograde endoscopic access to the collecting system, and intracorporeal lithotripsy devices almost completely have supplanted the need for a traditional ureterolithotomy. The merits of the various technologies that are available are discussed as they apply to treating calculi in different ureteral segments.

MRI evaluation of cavitation induced by laser prostatectomy

Magnetic resonance images obtained by endorectal surface coils have shown histopathological changes in the prostate. In patients who underwent laser prostatectomy, MR imaging demonstrated how deeply the laser energy penetrated and how different changes were induced by the coagulation and vaporization techniques. Cavitation effects were quantitatively analyzed, and the processes of reepithelization after sloughing of necrotic tissues were observed in gadolinium-enhanced T1-weighted images.