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Concept: Renal artery

168

BACKGROUND: Renal scintigraphy using 99mTc-mercaptoacetyltriglycine (99mTc-MAG3) is widely used for the assessment of renal function in humans. However, the application of this method to animal models of renal disease is currently limited, especially in rodents. Here, we have applied 99mTc-MAG3 renal scintigraphy to a mouse model of unilateral ureteral obstruction (UUO) and evaluated its utility in studying obstructive renal disease. METHODS: UUO mice were generated by complete ligation of the left ureter. Sham-operated mice were used as a control. Renal function was investigated on days 0, 1, 3, and 6 post-surgery using dynamic planar imaging of 99mTc-MAG3 activity following retro-orbital injection. Time-activity curves (TACs) were produced for individual kidneys and renal function was assessed by 1) the slope of initial 99mTc-MAG3 uptake (SIU), which is related to renal perfusion; 2) peak activity; and 3) the time-to-peak (TTP). The parameters of tubular excretion were not evaluated in this study as 99mTc-MAG3 is not excreted from UUO kidneys. RESULTS: Compared to sham-operated mice, SIU was remarkably (>60%) reduced in UUO kidneys at day 1 post surgery and the TACs plateaued, indicating that 99mTc-MAG3 is not excreted in these kidneys. The plateau activity in UUO kidneys was relatively low (~40% of sham kidney’s peak activity) as early as day1 post surgery, demonstrating that uptake of 99mTc-MAG3 is rapidly reduced in UUO kidneys. The time to plateau in UUO kidneys exceeded 200 sec, suggesting that 99mTc-MAG3 is slowly up-taken in these kidneys. These changes advanced as the disease progressed. SIU, peak activity and TTPs were minimally changed in contra-lateral kidneys during the study period. CONCLUSIONS: Our data demonstrate that renal uptake of 99mTc-MAG3 is remarkably and rapidly reduced in UUO kidneys, while the changes are minimal in contra-lateral kidneys. The parametric analysis of TACs suggested that renal perfusion as well as tubular uptake is reduced in UUO kidneys. This imaging technique should allow non-invasive assessments of UUO renal injury and enable a more rapid interrogation of novel therapeutic agents and protocols.

Concepts: Kidney, Urinary system, Ureter, Renal artery, Renal vein, Hydronephrosis

151

Conventional ultrasound in combination with colour Doppler imaging is still the standard diagnostic procedure for patients after renal transplantation. However, while conventional ultrasound in combination with Doppler imaging can diagnose renal artery stenosis and vein thrombosis, it is not possible to display subtle microvascular tissue perfusion, which is crucial for the evaluation of acute and chronic allograft dysfunctions. In contrast, real-time contrast-enhanced sonography (CES) uses gas-filled microbubbles not only to visualize but also to quantify renal blood flow and perfusion even in the small renal arterioles and capillaries. It is an easy to perform and non-invasive imaging technique that augments diagnostic capabilities in patients after renal transplantation. Specifically in the postoperative setting, CES has been shown to be superior to conventional ultrasound in combination with Doppler imaging in uncovering even subtle microvascular disturbances in the allograft perfusion. In addition, quantitative perfusion parameters derived from CES show predictive capability regarding long-term kidney function.

Concepts: Kidney, Nephrology, Blood, Medical terms, Blood vessel, Renal physiology, Artery, Renal artery

31

A previously healthy 36-year-old Japanese woman presented with blood pressure that was difficult to control after an emergency cesarean section. CT revealed a disrupted abdominal aorta, severe stenosis of the renal arteries, and development of numerous collateral arteries.

Concepts: Kidney, Artery, Abdominal aorta, Renal artery, Caesarean section, Takayasu's arteritis, Arteritis, Angiology

28

Morphological changes that occur during kidney injury involve actin skeleton remodeling. Here we tested whether heat-shock protein 27 (HSP27), a small stress response protein involved in cytoskeletal remodeling, protects the kidney from tubulointerstitial fibrosis in obstructive nephropathy. Tubular cell HSP27 immunostaining was significantly increased in human kidneys with ureteropelvic junction obstruction, supporting the clinical relevance of our studies. To develop an animal model for mechanistic studies, we generated transgenic mice that specifically overexpress human HSP27 in renal tubules, under the kidney androgen-regulated protein promoter, and determined the effects of HSP27 overexpression on epithelial-to-mesenchymal transition and tubulointerstitial fibrosis following unilateral ureteral obstruction. This was associated with decreased fibrogenesis as evidenced by significant declines in phosphorylated p38MAPK, collagen III, α-smooth muscle actin, 4-hydroxynonenal, and reduced trichrome staining following obstruction. Notably, E-cadherin and β-catenin remained at the cell membrane of tubular cells in transgenic mice with an obstructed ureter. Monocyte/macrophage infiltration, however, was not significantly affected in these transgenic mice. Thus, tubular HSP27 inhibits fibrogenesis in obstructive nephropathy. Further studies are needed to determine pathways regulating the interactions between HSP27 and the E-cadherin-β-catenin complex.

Concepts: Protein, Kidney, Gene, Gene expression, Urinary bladder, Ureter, Actin, Renal artery

28

A 31-year-old woman was referred to our hospital because of gross hematuria. Radiologic examinations with computed tomography and magnetic resonance imaging revealed renal arteriovenous malformation in the right kidney and an entrapped retroaortic left renal vein. Because the patient was free of hematuria, she refused additional treatment for economic reasons. Renal arteriovenous malformation associated with the posterior nutcracker phenomenon is a very rare condition.

Concepts: Kidney, Patient, Medical imaging, Ureter, Radiology, Renal artery, Renal vein, Minor calyx

28

Abstract A 53-year-old man presented with a 6-month history of intermittent right flank pain. Radiological imaging confirmed the diagnosis of retrocaval ureter (RCU) and ureteral calculus. Retroperitoneal laparoendoscopic single-site surgery (LESS) ureterolithotomy and ureteroureterostomy was successfully performed. The operative time was 185 min and the blood loss was approximately 20 ml. The patient’s postoperative course was uneventful. Postoperative analgesia was not needed. The patient was discharged on the third postoperative day. The drain and double-J stent were respectively removed at 1 and 8 weeks postoperatively. At the 3-month follow-up, nuclear scan showed no evidence of obstruction of the right kidney and the patient also remained symptom free. It may be concluded that retroperitoneal LESS repair for RCU is a feasible and safe procedure, which can be considered as a option for the management of RCU even if it is complicated by the presence of a ureteral calculus.

Concepts: Kidney, Medical terms, Urine, Urinary system, Ureter, Radiology, Renal artery

27

Nutcracker syndrome (NCS), which is caused by compression of the left renal vein between the abdominal aorta and the superior mesenteric artery, leads to a series of clinical symptoms including hematuria, proteinuria, flank pain, and varicocele. The diagnosis of NCS is difficult due to variations in normal anatomy. Treatment, which ranges from observation to nephrectomy, remains controversial. We conducted a review based on the related literature and our experience with hundreds of cases. We summarize the characteristics of NCS, the different measurements used in diagnosis, and the current treatment options. We present our diagnostic criteria and recommend endovascular stenting as the primary option for NCS.

Concepts: Kidney, Greek loanwords, Abdominal aorta, Renal artery, Renal vein, Inferior vena cava, Superior mesenteric artery, Nutcracker syndrome

24

Vas deferens ectopia is a rare congenital anomaly frequently associated with anorectal abnormalities and hypospadias. We present a Currarino syndrome case with an ectopic vas deferens terminating in a distal retroiliac ureter. A left vasectomy, ureteral decussation over the iliac vessels and a Cohen’s type ureteral reimplantation were performed. The objectives are to preserve renal function, prevent epididymitis and preserve fertility. There is no evidence in the literature that recommends surgical correction of the vas deferens. Microsurgical epididymal sperm aspiration or testicular sperm extraction combined with intracytoplasmic sperm injection (ICSI) might be a viable strategy for these affected individuals.

Concepts: Kidney, Sperm, Ureter, Renal artery, Epididymis, Vas deferens, Vasectomy

11

There have been several recent attempts to generate, de novo, a functional whole kidney from stem cells using the organogenic niche or blastocyst complementation methods. However, none of these attempts succeeded in constructing a urinary excretion pathway for the stem cell-generated embryonic kidney. First, we transplanted metanephroi from cloned pig fetuses into gilts; the metanephroi grew to about 3 cm and produced urine, although hydronephrosis eventually was observed because of the lack of an excretion pathway. Second, we demonstrated the construction of urine excretion pathways in rats. Rat metanephroi or metanephroi with bladders (developed from cloacas) were transplanted into host rats. Histopathologic analysis showed that tubular lumina dilation and interstitial fibrosis were reduced in kidneys developed from cloacal transplants compared with metanephroi transplantation. Then we connected the host animal’s ureter to the cloacal-developed bladder, a technique we called the “stepwise peristaltic ureter” (SWPU) system. The application of the SWPU system avoided hydronephrosis and permitted the cloacas to differentiate well, with cloacal urine being excreted persistently through the recipient ureter. Finally, we demonstrated a viable preclinical application of the SWPU system in cloned pigs. The SWPU system also inhibited hydronephrosis in the pig study. To our knowledge, this is the first report showing that the SWPU system may resolve two important problems in the generation of kidneys from stem cells: construction of a urine excretion pathway and continued growth of the newly generated kidney.

Concepts: Kidney, Urine, Urinary bladder, Urinary system, Urination, Ureter, Renal pelvis, Renal artery

7

The management of atherosclerotic renal artery stenosis in patients with hypertension or impaired renal function remains a clinical dilemma. The current general consensus, supported by the results of the Angioplasty and Stenting for Renal Atherosclerotic Lesions and Cardiovascular Outcomes for Renal Artery Lesions trials, argues strongly against endovascular intervention in favor of optimal medical management. We discuss the limitations and implications of the contemporary clinical trials and present our approach and formulate clear recommendations to help with the management of patients with atherosclerotic narrowing of the renal artery.

Concepts: Renal failure, Nephrology, Myocardial infarction, Atherosclerosis, Hypertension, Blood pressure, Renal artery, Renal artery stenosis