Hypoplastic Vessels Research Articles

Абдоминальный крипторхизм на фоне полной диссоциации яичка и семявыносящего протока, имитирующей синдром тестикулярной регрессии.

Introduction. Complete separation of the deferent duct from the epididymis with the testicle in abdominal cryptorchidism cases is an extremely rare variation of abnormal development of genitals in boys. Available sources mention just 3 clinical cases similar to our observations. The unique anatomic details of the abnormality and extreme rarity of its exposure pave the way for a failure to reveal an intra-abdominal testis, and determine the need for particular attention during diagnostic laparoscopy. Materials and methods. Two patients with non-palpable left-sided cryptorchidism underwent a diagnostic laparoscopy, which revealed an intra-abdominal testis with epididymis on testicular vessels that was completely separated from the deferent duct. The difference between the described clinical cases was in the distance between the deep inguinal ring and the crossing of testicular vessels from the retroperitoneal location to the intraperitoneal position, which was approximately 3- 4 cm in the first patient and 4-5 mm in the second one. The second difference was in the "closed" deep inguinal ring found on the left side in the first case while the second patient had a patent processus vaginalis case. In both cases an incision was made in the left inguinal area, the inguinal canal was opened, and exploration thereof revealed blind-ended deferent ducts. The testicle in both cases was brought down through the inguinal canal and attached in the scrotum. Results. No complications occurred during the early postoperative care period, the check-up examination in 6 months following the surgery revealed no signs of testis atrophy or malposition in both patients. Conclusion. In diagnostic laparoscopy for abdominal cryptorchidism, it is important to consider the possibility of complete separation of the testicle and vas deferens. Detection of the deferent duct passing through the «closed» deep inguinal ring together with hypoplastic vessels does not rule out the chances for an ipsolateral intra-abdominal testis; therefore, a careful examination of the abdominal cavity along the embryological testicular migration path is necessary.

Age-related changes in the completeness of the circle of Willis in children.

The circle of Willis is a circulatory anastomosis that supplies blood to the brain. If any of the bridging segments arehypoplastic or absent, the capacity for collateral flow in the setting of large vessel occlusion may be decreased. Outside of the neonatal period, the prevalence of a complete circle of Willis (CoW) in the pediatric population has not been well described. Our objectives include determining the prevalence of a complete CoW in children and identifying if there is an age-related "loss" of arterial segments. Following IRB approval, angiograms of the CoW performed on a 3-T MR platform from 2016 to 2020 on patients 21years or younger were retrospectively reviewed. Any patient with underlying arterial pathology that may affect the CoW was excluded. Patient age and gender at the time of imaging were obtained. In total, 592 pediatric CoW were assessed. Frequencies of completeness were calculated in two different fashions: scenario 1 where a CoW was characterized as complete even if it contained hypoplastic vessels (88.8%), and scenario 2 where it was characterized as complete after excluding hypoplastic vessels (44.0%). In both scenarios, our data showed that older age was more associated with an incomplete CoW (p < 0.0001). In addition, we found a higher percentage of males with an incomplete CoW compared with females (p < 0.0001). The presence of a complete CoW is greater in our pediatric population than what has been reported in adults. The prevalence of an incomplete circle of Willis also increases significantly with age.

Defective development and microcirculation of intestine in Npr2 mutant mice

Intractable gastrointestinal (GI) diseases often develop during infancy. Our group previously reported that natriuretic peptide receptor B (NPR-B)-deficient Npr2slw/slw mice exhibit severe intestinal dysfunction, such as stenosis and distention, which resembles the dysfunction observed in Hirschsprung’s disease-allied disorders. However, the root cause of intestinal dysfunction and the detailed of pathophysiological condition in the intestine are not yet clear. Here, we report that the intestine of preweaning Npr2slw/slw mice showed bloodless blood vessels, and nodes were found in the lymphatic vessel. Additionally, the lacteals, smooth muscle, blood vessel, and nerves were barely observed in the villi of preweaning Npr2slw/slw mice. Moreover, intramuscular interstitial cells of Cajal (ICC-IM) were clearly reduced. In contrast, villi and ICC-IM were developed normally in surviving adult Npr2slw/slw mice. However, adult Npr2slw/slw mice exhibited partially hypoplastic blood vessels and an atrophied enteric nervous. Furthermore, adult Npr2slw/slw mice showed markedly reduced white adipose tissue. These findings suggest that the cause of GI dysfunction in preweaning Npr2slw/slw mice is attributed to defective intestinal development with microcirculation disorder. Thus, it is suggested that NPR-B signaling is involved in intestinal development and control of microcirculation and fat metabolism. This report provides new insights into intractable GI diseases, obesity, and NPR-B signaling.

Is the Vertebral Posterior Line a Safety Landmark for Cervical Posterior Screw Insertion? - Radiological Study of the Vertebral Artery in the Cervical Spine.

At posterior cervical fixation, iatrogenic injury of the vertebral artery (VA) must be avoided. As the VA is usually located in front of the posterior line of the vertebral body, intraoperative lateral fluoroscopy is used to identify the line. We investigated in how many of 105 patients (210 VAs) this line is a safe marker. We also inspected the original cervical magnetic resonance angiograms (MRA) of 105 consecutive patients who had been treated for other than cervical spine diseases to study some anatomical characteristics of the VA in the cervical spine. The distance from the posterior line of the vertebral body to the posterior VA surface was classified as safe, as requiring attention, and as unsafe. Among the 210 VAs, four hypoplastic vessels were excluded from this study; consequently, 206 VAs were available for assessment. The average distance exceeded 6 mm, it was shorter at the upper cervical level. Although in at least 200 VAs (97.1%) the distance between C4 and C7 was safe, in only 170 VAs (82.5%) was it safe at C3. We observed a total of 31 tortuous loops in 17 VAs; their presence had a significant negative effect on the usefulness of the safety line. Although the posterior line of the vertebral body may be useful for safe screw insertion at the C4–C7 level, it may be less useful at C3. In the presence of tortuous VA loops, close attention must be paid to the reliability of the safety line during cervical spine surgery.

The Geometry of the Circle of Willis Anatomical Variants as a Potential Cerebrovascular Risk Factor.

To correlate the anatomical variants of the circle of Willis with their effects on the hemodynamic and geometrical parameters responsible for the pathogenesis of neurological diseases. The circle of Willis and the proximal segments of the main arteries were dissected and measured on ten formalin-fixed human brains. The anatomical variants were systematized using descriptive statistics. The mathematical models for brain perfusion and wall shear stress were developed by optimally approximating resistance to flow, vascular conductance, and branching. Eighty percent of the brains presented asymmetries, especially in the posterior communicating (70%) and anterior cerebral (40%) arteries. The posterior circulation had more variations (65.21%). Nine hypoplastic vessels were found in 7 brains. Atypical origins were observed in eight specimens. According to the mathematical models, which integrated each anatomical change in the global circle of Willis anatomy, the circle of Willis' geometry could represent a risk factor for intracranial aneurysms and atherosclerosis, mostly when hypoplastic arteries are present, due to high resistance to flow and imbalanced bifurcation geometry. Accessory vessels are less associated with cerebrovascular risk. We described anatomical variants of both the anterior and posterior circulations and their specific effects on the hemodynamic balance of cerebral blood flow.

Abstract 18055: Induced Growth of Hypoplastic Cardiac Structures to Facilitate Repair of Congenital Defects

Introduction: Congenital heart defects (CHD) may include hypoplastic valves, ventricles and vessels which complicate repairs. Our hypotheses were that hypoplastic structures are developmental rather than primarily genetic in origin and the correct biomechanical signal would induce catch up growth. Our corollary hypothesis was that the growth signal is provided by flow, not pressure. First stage operations, therefore, were designed to increase flow and induce growth. Once growth was sufficient, a second operation would often complete the repair. We report our results using flow induced growth of hypoplastic structures to facilitate repair in 3 types of CHD. Methods: Three groups of CHD patients with associated hypoplastic structures: unbalanced atrioventricular canal defects (UAVC); pulmonary atresia with intact ventricular septum (PAIVS); and coarctation of the aorta (CoA) were reviewed. Operations increased flow through the hypoplastic structures, such as creating restrictive septal defects to increase flow through the hypoplastic AV valves and ventricles (UAVC, PAIVS) or relieving obstruction (CoA) to enhance aortic valve and arch flow. Results: On follow up, virtually all (85/90) hypoplastic structures reached normal size and the rest had nearly comparable growth (Table). Conclusions: 1) Operations designed to increase flow through hypoplastic structures reliably induced catch up growth of UAVC, PAIVS and CoA lesions. 2) The growth response supported underdevelopment as the cause of hypoplasia and flow as the growth signal to reverse it. 3) Growth induction allowed two ventricle repairs in UAVC and PAIVS patients and avoided extended arch repairs in CoA; all with decreased operative risk. 4) Following catch up growth of the hypoplastic lesions, the outlook improved to that of patients with balanced AVCs, normal sized RVs in pulmonary atresia and well repaired CoA. 5) Once normal size was reached growth continued, producing a durable result.

Circle of Willis Configuration as a Determinant of Intracranial Dolichoectasia

Background: Circle of Willis (COW) variants might influence arterial caliber in the brain. We hypothesized that these variants would be associated with the prevalence of intracranial dolichoectasia (DE). Methods: We examined COW variants and DE in a sample of stroke-free participants (n = 436) undergoing magnetic resonance angiography (MRA) as part of a population-based study. Large intracranial arterial diameters were obtained when available; if not, the artery was defined as hypoplastic or absent according to its visibility on MRA. Subscores for the anterior and the posterior circulations were created. DE was defined as arterial diameters ≥2 SD above the population mean for that artery, adjusting for intracranial volume. Generalized linear models with a Poisson distribution were used to evaluate predictors of both absent and hypoplastic vessels, and logistic regression was used to assess the odds ratio (OR) and 95% confidence interval (95% CI) of DE depending on COW variants. Results: Only 44% of the sample had all 14 arteries present, 32% lacked 1 artery, 18% lacked 2 and 6% lacked 3 or more. DE of at least 1 artery was not associated with the total number of hypoplastic or absent arteries, but DE in a posterior circulation artery was weakly associated with the number of absent arteries in the posterior circulation (β coefficient = 0.36, p = 0.06). DE of at least 1 artery was more frequent in those with 1 or more absent arteries (OR 1.27, 95% CI 1.03-1.57). Posterior circulation DE was more frequent in participants with at least 1 or more absent arteries at any location (OR 1.35, 95% CI 1.02-1.78). Participants with an incomplete posterior COW were more likely to have DE in the anterior circulation (OR 1.52, 95% CI 1.01-2.33). Having an absent left anterior cerebral artery (ACA) A1 segment was associated with right ACA DE (OR 34.1, 95% CI 3.16-368.2); an absent right ACA was associated with left ACA DE (OR 14.1, 95% CI 1.69-118.28). Absence of 1 (OR 1.9, 95% CI 1.1-3.4) or 2 (OR 3.0, 95% CI 1.4-6.6) of the 2 arteries connecting the anterior to the posterior circulation was associated with basilar artery DE. Conclusion: The COW is a pleomorphic structure that allows collateral flow to compensate for an insufficient or absent arterial component at the base of the skull. By presumed flow diversion, arteries might undergo outward remodeling. Whether this compensatory arterial dilatation is beneficial or not remains unknown.

Average dimensions of the vessels at the base of the brain and the embryological basis of its variations

Abstract Background and aims: The cerebral circulation is constantly maintained by the anastomotic circle of Willis which is often anomalous in more than 50% of the normal adult brains. These anomalies increase the risk of the stroke and transient ischemic attack in older patients. Adequate blood flow through the circle of Willis is often necessary to prevent these ischemic infarctions. The anomalies of cerebral vessels are directly related to the differential growth of various parts of the brain. A detailed knowledge of the individual measurements of the cerebral arteries is useful to neurosurgeon in planning the shunt operations and in the choice of their patients. The present study is aimed to analyze the average dimensions of the vessels at the base of brain and an attempt to explain the common form of variations in terms of embryological development. Materials and methods: Fifty adult cadaveric brains were obtained from routine cadaveric dissections. The base of the brain with the circle of Willis was fixed in 10% formalin and preserved. The circle was analyzed for variations in the size, length and number of the component vessels and any asymmetry in the configuration. The dimensions of the vessels forming the circle were measured using graduated calipers. The observations were recorded and tabulated. Results: Asymmetry was observed in 10% to 36% of the circles in this study. Anomalies were more common in the posterior than in the anterior part of the circle. The posterior anomalies included hypoplastic vessels, absent vessels and embryonic derivation while anterior anomalies were predominantly of accessory vessels. Middle cerebral artery exhibited the least variations. In majority of the circles, left sided vessels were larger in diameter than the right. Conclusions: Variations are more common in the posterior than in the anterior part of the circle and on the right than on the left side of the brain. There was no correlation between the variations of circle of Willis of the right side and the left cerebral dominance. There seems to be no difference between races, concerning the anatomic variations of the brain circulation.

State of the art and science for clinical translation of regenerative cardiac surgery

Cardiac surgery is entering a new era in which complex tissue reconstructions will be performed with bioengineered and tissue engineered constructs that reflect current discoveries in regenerative tissue methodologies. Cells of appropriate phenotype will be restored in well-designed functioning scaffolds using various methodologies including directed cell homing and seeding with pluripotent cells. Small children will benefit as hypoplastic vessels can be reconstructed with growth capable replacements obviating multiple reoperations. There has been a major need for pediatric heart valves that will allometrically grow and remodel synchronously with patient, somatic growth, this may be realized utilizing such technologies. The focus in this issue of Progress in Pediatric Cardiology is the clinical translation needed for the achievement of a tissue engineered heart valve. The numerous potential barriers are reviewed including scientific, surgical, logistical, regulatory challenges. Tissue engineered constructs will straddle the traditional definition of devices (the scaffold component) and biologics (the restored cell population component) and thus, may be defined as combination products. The central role of intellectual property in translational research may require different models of institutional research infrastructure and funding. Pediatric academic medical centers are adapting to these new realities, and instituting research programs, laboratories and collaborative science teams to tackle development of new regenerative surgical methodologies.

Abstract 052: Epicardial-derived Adrenomedullin Drives Cardiac Hyperplasia During Embryogenesis

The multi-functional peptide adrenomedullin ( Adm = gene, AM = protein) plays important roles in embryonic development and disease. Previous studies demonstrated that Adm knockout mice die at embryonic day 13.5 with small, disorganized hearts and hypoplastic lymphatic vessels, highlighting the importance of this peptide in normal cardiovascular development. Since Adm knockout animals are embryonic lethal, our goal was to generate and characterize a novel model of Adm over-expression to study the role of Adm during development and disease processes. Through gene targeting techniques, we generated a novel mouse model of Adm over-expression, abbreviated as Adm hi/hi . When we assessed gene expression of Adm from 10 different tissues, we found Adm hi/hi mice express 3- to 15-fold more Adm than wildtype littermates. Additionally, peptide levels of AM in lung and kidney, as well as circulating plasma levels of AM were elevated 3-fold over wildtype mice, indicating a functional increase in AM. Our initial analysis revealed that adult Adm hi/hi mice have larger heart weight to body weight ratios than wildtype littermates (4.93±0.23 vs. 5.96±0.29, n = 11-12). We found that compared to wildtype, Adm hi/hi embryos have more proliferating cells during heart development (14.46±1.11 vs. 31.97±2.84, n=4), indicating that hyperplasia drives Adm hi/hi heart enlargement. By crossing the Adm hi/hi line to different tissue-specific Cre lines, we were able to excise the stabilizing bovine growth hormone 3’UTR, thereby returning Adm expression levels back to wildtype in cells with active Cre recombinase. Using this approach, we identified the epicardium as a major source of AM during cardiac development. In conclusion, we found that AM derived primarily from the epicardium drives cardiac hyperplasia during embryonic development resulting in persistent, enlarged hearts of adult Adm hi/hi mice. Since our Adm hi/hi mice recapitulate the 3-fold plasma elevation of AM observed during human disease, this mouse line will be a useful tool for studying the role of elevated AM during disease.

Vertebrobasilar variants and their basic clinical implications

Objectives: Cerebrovascular diseases are the leading illness affecting the modern world with a high mortality rate. The posterior circulation of the brain consists of vertebrobasilar system, shows a high incidence of anomalies in the form of hypoplasia, fenestrations and asymmetry of the vessels, which precipitate the development of vertebrobasilar insufficiency and posterior circulation stroke. A detailed knowledge of the vertebrobasilar variants is essential in the diagnosis, treatment as well as in educating the patients suffered fro m posterior circulation stroke. The present study is aimed to analyze the size, asymmetry and anomalies of the vertebrobasilar system and their implications in posterior circulation infarcts. Materials and methods: Fifty adult brains were studied during routine dissection of the cadavers. The base of the brain with intact vertebral, basilar and posterior cerebral arteries were dissected, preserved in 10% formalin and analyzed for the variations in the size, length and asymmetry in the configuration. The dimensions of the vessels were measured using graduated calipers. Results: Anomalies of the basilar artery were found in 14% of the bra ins, in the form of hypoplasia, fenestration and terminal expansion at its bifurcation . The vertebral arteries showed asymmetry with right vertebral were hypoplastic in majority of the brains . Conclusions: The variations of the vertebrobasilar system increase the risk of vertebrobasilar insufficiency and posterior circulation stroke. Anomalies of the vertebrobasilar arteries were also found to be associated with aneurysms. The right vertebral artery has been frequently hypoplastic and there was no consistent correlation between the left vertebral dominance and right handedness of the person. Hypoplastic vessels were frequently associated with vertebrobasilar territory ischemic stroke .

Average dimensions of the vessels at the base of the brain and the embryological basis of its variations

Background and aims: The cerebral circulation is constantly maintained by the anastomotic circle of Willis which is often anomalous in more than 50% of the normal adult brains. These anomalies increase the risk of the stroke and transient ischemic attack in older patients. Adequate blood flow through the circle of Willis is often necessary to prevent these ischemic infarctions. The anomalies of cerebral vessels are directly related to the differential growth of various parts of the brain. A detailed knowledge of the individual measurements of the cerebral arteries is useful to neurosurgeon in planning the shunt operations and in the choice of their patients. The present study is aimed to analyze the average dimensions of the vessels at the base of brain and an attempt to explain the common form of variations in terms of embryological development. Materials and methods: Fifty adult cadaveric brains were obtained from routine cadaveric dissections. The base of the brain with the circle of Willis was fixed in 10% formalin and preserved. The circle was analyzed for variations in the size, length and number of the component vessels and any asymmetry in the configuration. The dimensions of the vessels forming the circle were measured using graduated calipers. The observations were recorded and tabulated. Results: Asymmetry was observed in 10% to 36% of the circles in this study. Anomalies were more common in the posterior than in the anterior part of the circle. The posterior anomalies included hypoplastic vessels, absent vessels and embryonic derivation while anterior anomalies were predominantly of accessory vessels. Middle cerebral artery exhibited the least variations. In majority of the circles, left sided vessels were larger in diameter than the right. Conclusions: Variations are more common in the posterior than in the anterior part of the circle and on the right than on the left side of the brain. There was no correlation between the variations of circle of Willis of the right side and the left cerebral dominance. There seems to be no difference between races, concerning the anatomic variations of the brain circulation.

Morphometric analysis of Willis circle arteries

Introduction: Willis arterial circle (circulus arteriosus cerebri Willisi) is the most important part of the collateral circulatory system of the brain. It functions in normal and pathological situations such as valvular mechanism and thus allows optimal blood supply of all parts of the brain tissue, which reduces the risk of transient ischemic attack (TIA) and stroke. The main pre-requisite for the normal function of the circle is its completeness and the lack of hypoplastic vessels. Materials and Methods: In this research, we used 100 angiograms of carotid system shown by serial angiography by Seldinger taken from the archives of the Department of Radiology, Clinical Center University of Sarajevo. For morphometric analysis of blood vessels, we used specially designed software program ELLIPSE (ViDiTo, Zoltan Tomoris, Kosice, Slovak Republic, tomori@saske.sk. In this way, it was possible to more easily store and analyze angiograms that were used for morphometric analysis. Results: In our study, larger diameters of blood vessels in Willis circle were observed in the younger subjects compared to older except the diameter of the internal carotid artery, which was about 0.2 to 0.3 mm larger in the older subjects. In both age groups among males, we recorded larger diameters of the internal carotid artery and segment before the circle of the posterior cerebral artery in relation to the female population, while the rear communicating artery in females was 0.1 mm wider in diameter compared to men in category of younger respondents.

Tbx1 Genetically Interacts With the Transforming Growth Factor-β/Bone Morphogenetic Protein Inhibitor Smad7 During Great Vessel Remodeling

Growth and remodeling of the pharyngeal arch arteries are vital for the development of a mature great vessel system. Dysmorphogenesis of the fourth arch arteries can result in interruption of the aortic arch type B, typically found in DiGeorge syndrome. Tbx1 haploinsufficient embryos, which model DiGeorge syndrome, display fourth arch artery defects during formation of the vessels. Recovery from such defects is a documented yet unexplained phenotype in Tbx1 haploinsufficiency. To understand the nature of fourth arch artery growth recovery in Tbx1 haploinsufficiency and its underlying genetic control. We categorized vessel phenotypes of Tbx1 heterozygotes as hypoplastic or aplastic at the conclusion of pharyngeal artery formation and compared these against the frequency of vessel defects scored at the end of great vessel development. The frequency of hypoplastic vessels decreased during embryogenesis, whereas no reduction of vessel aplasia was seen, implying recovery is attributable to remodeling of hypoplastic vessels. We showed that Smad7, an inhibitory Smad within the transforming growth factor-β pathway, is regulated by Tbx1, is required for arch artery remodeling, and genetically interacts with Tbx1 in this process. Tbx1 and Tbx1;Smad7 haploinsufficiency affected several remodeling processes; however, concurrent haploinsufficiency particularly impacted on the earliest stage of vascular smooth muscle cell vessel coverage and subsequent fibronectin deposition. Conditional reconstitution of Smad7 with a Tbx1Cre driver indicated that the interaction between the 2 genes is cell autonomous. Tbx1 acts upstream of Smad7 controlling vascular smooth muscle and extracellular matrix investment of the fourth arch artery.

Preferential involvement of hypoplastic vessels in vertebral artery dissection: a comparative study

Background and Purpose: The etiology of spontaneous vertebral artery dissection (sVAD) has been poorly understood until today. The aim of this clinical study was to analyze ultrasonographic measurements, in particular regarding the size of vessels, and clinical characteristics such as vascular risk factors.

Evaluation of the vessels of the lower leg before microsurgical fibular transfer. Part II: magnetic resonance angiography for standard preoperative assessment

The peroneal artery is the dominant supply of the osteomyocutaneous fibular flap. It has been shown that there can be anatomical variants that could jeopardise the blood supply to the lower limb during harvest of the flap. To avoid postoperative ischaemia of the lower leg, preoperative evaluation of adequate collateral perfusion is essential. We investigated whether magnetic resonance angiography (MRA) accurately shows anatomical variants and pathological stenoses of the vessels of the lower leg and whether it can replace conventional invasive techniques. Conventional digital subtraction angiography (DSA) was used in a prospective study of 15 patients, and contrast-enhanced MRA postoperatively. Arteries were evaluated by three radiologists for: size of vessel at the trifurcation; hypoplastic or missing vessels; appreciable stenosis or vascular occlusion, or both; atherosclerotic malformations; and overall vascular topography. High resolution MRA enabled a reliable judgement to be made of the vessels of the lower leg. MRA definitively detected hypoplastic vessels, stenoses, occlusion, or atherosclerotic changes of the vessels, and enabled both accurate assessment of the quality of vessels and the preferred site for the harvest of the flap. As it is a low risk procedure, it can be done in the outpatient department with no risk of radiation. It can easily replace conventional DSA.

Hypoplastic Gonadal Vessels Exiting the Deep Ring During Laparoscopy for Impalpable Testes: When Is Inguinal Exploration Necessary?

During laparoscopy for impalpable testes (IT), if the vas and vessels are found exiting the deep ring, many surgeons proceed to inguinal exploration as a routine, regardless of the adequacy of the vessels or the presence or absence of the processus vaginalis (PV). We tried to find out whether this was necessary in cases with hypoplastic vessels. This was a retrospective study of cases of IT where during laparoscopy, the vas deferens and the gonadal vessels were seen passing through the deep inguinal ring. Cases were divided into four groups, according to the condition of the PV: present (whether patent or closed) or absent and the adequacy of the vessels. Findings at inguinal exploration and histopathologic examination were compared. Over a period of 4 years, 27 children had laparoscopy for 36 IT. Twenty-three cases (64%) had the vas and vessels passing through the deep ring. Eleven cases (48%) had hypoplastic vessels: 5 (22%) with PV, and on inguinal exploration, 3 (60%) had atrophic testes, and 2 small "nubbins," and 6 (26%) with no PV; 3 with blind ended vas and vessels and 3 with small "nubbins." No case in the last group showed testicular tissue on histopathology. In cases with hypoplastic vessels exiting the deep inguinal ring, it is the presence or absence of PV that should determine the next step. If it is present, inguinal exploration should follow. If it is absent, exploration is unnecessary.

A model of autoregulated blood flow in the cerebral vasculature

The circle of Willis is a ring-like arterial structure located in the base of the brain, and is responsible for the distribution of oxygenated blood throughout the cerebral mass. Among the general population, approximately 50 per cent have a complete circle of Willis; for the others a multitude of possible anatomical variations are present, with absent or hypoplastic vessels being common. Certain conditions such as a build-up of atherosclerotic plaque on the arterial wall can result in ischaemic damage and stroke-like symptoms. A three-dimensional computer model has been developed based on the results of magnetic resonance imaging data, incorporating a numerical algorithm to simulate the body's autoregulation mechanism, such that oxygen delivery to the cerebral territories can be predicted in response events, leading to a reduction in cerebral blood flow. Sample results are presented for combinations of occlusion and stenosis.

Comprehensive MR evaluation of renovascular disease in five breath holds.

To detect a renal artery stenosis and assess its hemodynamic and functional significance in five breath holds. In a single MR exam, T1 weighted FLASH and T2 weighted fast spin echo techniques are used to assess renal morphology, multiphase 3D gadolinium (Gd) MRA to evaluate the renal arteries, and a segmented EPI cine phase-contrast technique to measure renal artery blood flow. A standardized image analysis is performed to assess kidney size, corticomedullar differentiation (CMD), parenchymal enhancement, the degree of renal artery stenosis, abnormalities in blood flow pattern, and any associated abdominal vascular disease. Multiphase 3D-Gd-MRA accurately assesses atherosclerotic renal artery disease particularly in the presence of an associated aortic aneurysm. Delayed parenchymal enhancement, loss of CMD, and decrease in kidney size can be detected. In combination with decreased systolic velocity components, the diagnosis of a hemodynamically and functionally significant stenosis can be made. High-resolution single-phase 3D-Gd-MRA is preferable for evaluation of fibromuscular dysplasia or hypoplastic vessels. The combination of different breath hold techniques in a single, standardized MR exam allows to detect the hemodynamic and functional significance of a renal artery stenosis.

Renal afferent arteriole in the spontaneously hypertensive rat.

We conducted morphometric studies on the afferent arteriole of spontaneous hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats to gain a better understanding of its changes with the development of hypertension. Differences may be related to the SHRs' increased renal vascular resistance. Methacrylate vascular casts were made of the renal vasculature after perfusion fixation with glutaraldehyde. These vascular casts were then examined and measurements made with the scanning electron microscope. Results from this examination of the scanning electron microscope demonstrated a smaller afferent arteriolar diameter in the SHR, compared to the WKY, for both the inner and outer cortical glomeruli. This difference was seen in the 6-week-old SHR, prior to a statistically different blood pressure from the WKY controls, as well as in the 12-week-old hypertensive SHR. However, this afferent diameter difference between rat strains was more pronounced in rats at 12 weeks of age. The tapering of the afferent arteriole (difference between proximal and distal afferent diameters) was greater in the 12-week-old SHR than in the age-matched WKY or 6-week-old SHR. We conclude that the smaller caliber afferent arterioles of the SHR may predispose and play a role in the pathogenesis of the subsequent hypertension. The increased afferent arteriolar tapering seen in the hypertensive SHR relates to the already present increased blood pressure. Wall thickness/radius ratios are not different between rat strains (SHR and WKY) at either 6 or 12 weeks of age. These results suggest increased vascular constriction or hypoplastic vessels as the cause of the smaller caliber vessels in the SHR rather than increased wall thickness.