Occlusive and aneurysmal disease of the renal arterial circulation

Kidney Intrinsic Mechanisms as Novel Targets in Renovascular Hypertension

Almost a hundred years have passed since obstruction of the renal artery has been recognized to raise blood pressure. By now chronic renovascular disease (RVD) due to renal artery stenosis is recognized as a major source of renovascular hypertension and renal disease. In some patients, RVD unaccompanied by noteworthy renal dysfunction or blood pressure elevation may be incidentally identified during peripheral angiography. Nevertheless, in others, RVD might present as a progressive disease associated with diffuse atherosclerosis, leading to loss of renal function, renovascular hypertension, hemodynamic compromise, and a magnified risk for cardiovascular morbidity and mortality. Atherosclerotic RVD leads to renal atrophy, inflammation, and hypoxia but represents a potentially treatable cause of chronic renal failure because until severe fibrosis sets in the ischemic kidney, it retains a robust potential for vascular and tubular regeneration. This remarkable recovery capacity of the kidney begs for early diagnosis and treatment. However, accumulating evidence from both animal studies and randomized clinical trials has convincingly established the inadequate efficacy of renal artery revascularization to fully restore renal function or blood pressure control and has illuminated the potential of therapies targeted to the ischemic renal parenchyma to instigate renal regeneration. Some of the injurious mechanisms identified as potential therapeutic targets included oxidative stress, microvascular disease, inflammation, mitochondrial injury, and cellular senescence. This review recapitulates the intrinsic mechanisms that orchestrate renal damage and recovery in RVD and can be harnessed to introduce remedial opportunities.

FMD and SCAD: Sex-Biased Arterial Diseases With Clinical and Genetic Pleiotropy

Multifocal fibromuscular dysplasia (FMD) and spontaneous coronary artery dissection are both sex-biased diseases disproportionately affecting women over men in a 9:1 ratio. Traditionally known in the context of renovascular hypertension, recent advances in knowledge about FMD have demonstrated that FMD is a systemic arteriopathy presenting as arterial stenosis, aneurysm, and dissection in virtually any arterial bed. FMD is also characterized by major cardiovascular presentations including hypertension, stroke, and myocardial infarction. Similar to FMD, spontaneous coronary artery dissection is associated with a high prevalence of extracoronary vascular abnormalities, including FMD, aneurysm, and extracoronary dissection, and recent studies have also found genetic associations between the two diseases. This review will summarize the relationship between FMD and spontaneous coronary artery dissection with a focus on common clinical associations, histopathologic mechanisms, genetic susceptibilities, and the biology of these diseases. The current status of disease models and critical future research directions will also be addressed.

Effects of tigecycline and vancomycin administration on established Clostridium difficile infection

The glycylcycline antibiotic tigecycline was approved in 2005 for the treatment of complicated skin and soft tissue infections and complicated intra-abdominal infections. Tigecycline is broadly active against both Gram-negative and Gram-positive microorganisms, including Clostridium difficile. Tigecycline has a low MIC against C. difficile in vitro and thus may represent an alternate treatment for C. difficile infection (CDI). To assess the use of tigecycline for treatment of established CDI, 5- to 8-week-old C57BL/6 mice were colonized with C. difficile strain 630. After C. difficile colonization was established, mice (n = 10 per group) were treated with either a 5-day course of tigecycline (6.25 mg/kg every 12 h subcutaneously) or a 5-day course of vancomycin (0.4 mg/ml in drinking water) and compared to infected, untreated control mice. Mice were evaluated for clinical signs of CDI throughout treatment and at 1 week posttreatment to assess potential for disease development. Immediately following a treatment course, C. difficile was not detectable in the feces of vancomycin-treated mice but remained detectable in feces from tigecycline-treated and untreated control mice. Toxin activity and histopathological inflammation and edema were observed in the ceca and colons of untreated mice; tigecycline- and vancomycin-treated mice did not show such changes directly after treatment. One week after the conclusion of either antibiotic treatment, C. difficile load, toxin activity, and histopathology scores increased in the cecum and colon, indicating that C. difficile-associated disease occurred. In vitro growth studies confirmed that subinhibitory concentrations of tigecycline were able to suppress toxin activity and spore formation of C. difficile, whereas vancomycin did not. Taken together, these data show how tigecycline is able to alter C. difficile pathogenesis in a mouse model of CDI.

Clinical and biochemical profiles suggest fibromuscular dysplasia is a systemic disease with altered TGF-β expression and connective tissue features

Fibromuscular dysplasia (FMD) is a rare, nonatherosclerotic arterial disease for which the molecular basis is unknown. We comprehensively studied 47 subjects with FMD, including physical examination, spine magnetic resonance imaging, bone densitometry, and brain magnetic resonance angiography. Inflammatory biomarkers in plasma and transforming growth factor β (TGF-β) cytokines in patient-derived dermal fibroblasts were measured by ELISA. Arterial pathology other than medial fibrodysplasia with multifocal stenosis included cerebral aneurysm, found in 12.8% of subjects. Extra-arterial pathology included low bone density (P<0.001); early onset degenerative spine disease (95.7%); increased incidence of Chiari I malformation (6.4%) and dural ectasia (42.6%); and physical examination findings of a mild connective tissue dysplasia (95.7%). Screening for mutations causing known genetically mediated arteriopathies was unrevealing. We found elevated plasma TGF-β1 (P=0.009), TGF-β2 (P=0.004) and additional inflammatory markers, and increased TGF-β1 (P=0.0009) and TGF-β2 (P=0.0001) secretion in dermal fibroblast cell lines from subjects with FMD compared to age- and gender-matched controls. Detailed phenotyping of patients with FMD allowed us to demonstrate that FMD is a systemic disease with alterations in common with the spectrum of genetic syndromes that involve altered TGF-β signaling and offers TGF-β as a marker of FMD.

Heightened suspicion and rapid evaluation with CT for early diagnosis of partial renal infarction

BACKGROUND AND OBJECTIVE

Although renal infarction has been well studied and clearly defined, it remains greatly underdiagnosed, resulting in significant morbidity. Acute segmental renal infarction is a diagnosis even more problematic, as the problem can appear insidiously and masquerade as other entities including stone, infection, and even tumor. The clinical manifestations and evaluation of partial renal infarction in our patients were reviewed.

PATIENTS AND METHODS

Seven patients presenting to the emergency department who were subsequently found to have partial renal infarction were identified from the 5-year records of a single institution. Patients were evaluated for presenting complaints, physical findings, temperature, and blood pressure. Laboratory analysis consisted of a complete blood count (CBC); measurements of creatinine, lactate dehydrogenase (LDH), aspartate transaminase/alanine transaminase (AST/ALT), and alkaline phosphatase; and urinalysis. The sequence of the work-up was recorded, as well as time to diagnosis. The etiology of infarction was identified for all patients.

RESULTS

All seven patients were eventually discovered to have partial renal infarction as a result of dysrhythmia (N = 4), mural thrombus (N = 2), or septic emboli (N = 1). The average time to diagnosis was 65.2 hours with a range of 9.5 to 168 hours. The chief complaint was flank pain (N = 3), nonspecific abdominal pain (N = 2), left lower-quadrant pain (N = 1), and mental status change (N = 1). The presenting signs and symptoms included abdominal tenderness (N = 4), nausea and vomiting (N = 4), temperature >100.5 degrees F (N = 3), and hypertension (N = 3). Laboratory studies revealed a white cell count >11,000/microL in six, microhematuria in four, proteinuria in four, elevated LDH in all patients, elevated AST/ALT in two, and elevated alkaline phosphatase in one. The work-up varied by presentation, but definitive diagnosis was made by CT in all five patients scanned and by angiography in two. Angiography confirmed the CT findings in four of the five patients.

CONCLUSION

In evaluating partial renal infarction, a strong clinical suspicion is necessary. We found a history of dysrhythmia or other cardiac disease, the presence of abdominal or flank pain, fever with an elevated white cell count, and an elevated LDH to be clinically significant, and their presence should alert the clinician to the possibility of renal infarction. Once a degree of suspicion exists, early evaluation with CT should speed the diagnosis and effect decreased morbidity.

Alternative methods of renal revascularization

Saphenous vein aortorenal bypass is the most commonly used surgical procedure for relief of renovascular hypertension. Years of experience have shown the procedure to be effective with satisfactory long-term results. Coexisting disease conditions of the aorta sometimes make alternative methods of renal revascularization preferable, especially when more than one renal artery is involved. Such alternative procedures include transaortic endarterectomy, bilateral renal endarterectomy via a transverse incision across both renal arteries, or extra-anatomic bypass from the splenic, hepatic, or iliac arteries. Two hundred twenty-five renal revascularization procedures performed either alone or in combination with other abdominal vascular procedures during the last 5 years is reported. In 18 patients, one of the above procedures was performed. This experience with these various types of renal revascularization will be discussed with particular reference to indications, technique, and potential pitfalls of each procedure.