Prenatal Development of the Caudal Vena Cava in Mammals: Review of the Different Theories with Special Reference to the Dog

Levopositioned caudal vena cava and circumcaval left ureter with subsequent hydronephrosis and hydroureter in a dog

The presentation and investigation of a levopositioned caudal vena cava, a rare congenital vascular abnormality seen mainly in Bernese Mountain Dogs, which resulted in ureteral compression, hydronephrosis and hydroureter. Surgical transection, transposition and anastomosis were performed to reposition the circumcaval ureter. A 19-month-old male neutered Bernese Mountain Dog was presented with a 13-month history of vague signs including intermittent abdominal pain, inappetence and diarrhoea, which were poorly responsive to medical management. Abdominal ultrasound revealed left-sided hydronephrosis and hydroureter. Further investigation included abdominal computed tomography and pre- and post-intravenous iodinated contrast, which revealed a levopositioned caudal vena cava with associated ureteral displacement to a circumcaval position, resulting in ureteral compression and proximal dilation affecting both the proximal ureter and the left kidney. The patient was also found to have concomitant gall bladder agenesis. Surgery was performed to transect, transpose and anastomose the ureter in a normal anatomical position, and the patient made an excellent clinical recovery. All gastrointestinal signs resolved within 2 weeks of surgery and remained resolved 12 months later. Follow-up ultrasound and pyelography were performed at 4-month post-surgery, revealing a mild improvement in the hydronephrosis and hydroureter. Although rare, circumcaval ureter should be considered a differential in dogs presenting with hydroureter and hydronephrosis, especially Bernese Mountain Dogs.

Anatomical variants of the retroaortic left renal vein

BACKGROUND

Anatomical variants of the left renal vein (LRV), such as the retroaortic (RLRV) and circumaortic (CLRV) course, are of surgical importance. Different morphological and topographical possibilities of the RLRV could occur. It was aimed at documenting the anatomical variables of the RLRV.

METHOD

A retrospective study on 375 computed tomography angiograms was performed. Five different anatomical types of LRV were documented: preaortic types 1 and 2 and retroaortic types 3-5.

RESULTS

In 344/375 cases, preaortic LRVs were found. In 31/375 cases, different types of RLRV were found: type 3a - single RLRV, 41.94%; type 3b - single RLRV with bifid caval end, 9.68%; type 3c - single RLRV with trifid caval end, 3.23%; type 4a - CLRV with extrahilar origin, 29.03%; type 4b - CLRV with renal sinus origin, 12.9%; type 5 - triple LRV (one preaortic LRV and two RLRVs), 3.23%. Reference vertebral levels were recorded for the prevertebral segment of the RLVR. The vertebral level of type 3a varied from the L1/L2 disc to the upper third of the L4 vertebra. Type 3b was found in 3/31 RLRV cases; in one of these, the hemiazygos vein was inserted by two roots into the LRV and its upper caval end trunk. There was a significant statistical association between type 3b and the vertebral level, all cases being centered on the middle third of the L4 vertebra.

CONCLUSIONS

New morphological possibilities of the LRV were distinguished, and a new anatomical classification system of the RLRV results. The RLRV variant should be documented case-by-case as it has its anatomical variables.

Anatomical Characteristics of Duplicated Caudal Vena Cava in Cats-A Case Report

Precise knowledge of the species-/breed-specific anatomy is important for accurate diagnosis and treatment. Existing literature has also been increasing in accordance with the growing demands of biomedical research, wherein mammals, including cats, have been used worldwide. Based on a vascular corrosion cast, complete duplication of the caudal vena cava (dCVC) was accidentally found in a 10-year-old male cat. The two separate symmetric veins corresponding to two caudal venae cavae cranially directed on both sides of the aorta; their first tributaries were the duplicated right and left deep circumflex iliac veins, and the median sacral vein ended in the right common iliac vein. At the L4 vertebra level, the left caudal vena cava crossed the aorta ventrally. It united with the right CVC immediately above the renal veins at the level of the cranial mesenteric artery (L2-L3). Embryologic knowledge is essential to understand the differences between the CVC variants in domestic mammals and the inferior vena cava in humans. However, views regarding the post-hepatic segment of the CVC during development vary considerably. Therefore, our case report also includes a summary of the CVC developmental theories and their clinical impact. We believe that this case and literature review contribute to the knowledge regarding the deep abdominal veins' variability, concomitant pathologies, and accurate diagnosis and surgery. Additionally, the latest robust studies demonstrating the exclusive participation of the caudal cardinal veins in the CVC development are discussed.

Computed tomographic appearance of transcaval ureter in two dogs and three cats: A novel CVC congenital malformation

Transcaval ureter is a rarely reported human congenital malformation of the prerenal segment of the inferior vena cava (IVC) not yet reported in veterinary medicine. The objective of this multicenter retrospective case series study was to describe the computed tomography (CT) features of transcaval ureters in dogs and cats. Patients referring to pre- and post-contrast CT exams of the abdomen and presenting this abnormality were retrospectively included. Multiple qualitative features were described for each ureteral abnormality detected. Three cats and two dogs with transcaval ureter were identified consisting of a segmental duplication of the CVC at the prerenal level creating a vascular ring through which the ureter extended, identified as a double-barrel gun sign. The malformation was divided into two types according to the symmetry of the caval branches and location in relation to the aorta, namely, type I symmetrical branches and right-lateral to the aorta, and type II asymmetrically branches and right-dorsal to the aorta. In one case, the malformation was associated with hydroureter and mild pyelectasis. In three cases, the anomaly was incidental and, in the remaining two cases, the clinical significance was uncertain. This is the first study describing the presence of transcaval ureter in dogs and cats. CT was a suitable method for the diagnosis of transcaval and a focal double-barrel gun sign of the CVC is proposed as the hallmark feature of this anomaly. The clinical relevance of this congenital vascular malformation is unclear and needs to be further investigated.

Case report: Application of three-dimensional technologies for surgical treatment of portosystemic shunt with segmental caudal vena cava aplasia in two dogs

This case report describes the application of three-dimensional (3D) technologies for the surgical treatment of portosystemic shunt (PSS) with segmental caudal vena cava (CVC) aplasia. Two client-owned dogs were diagnosed with PSS along with segmental CVC aplasia using computed tomography. Through 3D volume and surface rendering, the vascular anatomic anomaly of each patient was identified in detail. A patient-specific 3D vascular model was used for preoperative planning. According to the plan established based on the 3D rendered image and printed model, shunt occlusion was performed using cellophane banding in the first case. An ameroid constrictor was used in the second case. Both patients showed good recovery without any clinical symptoms or complications. The use of 3D technologies in small animals has many advantages, and its use in vascular surgery, as in these cases, is also a therapeutic option worth considering.

Computed tomography diagnosis of a caval-azygos communication in a dog with cor triatriatum dexter

An 18-month-old Springer Spaniel was presented for investigation of ascites, exercise intolerance and suspected cor triatriatum dexter. Division of the right atrium into two separate chambers by an anomalous perforated membrane consistent with cor triatriatum dexter was confirmed during echocardiography. However, a routine agitated saline contrast (bubble) study yielded results that could not be explained by the congenital heart defect alone. Computed tomography angiography was performed and revealed a dilated ventral internal vertebral venous plexus and a short, dilated vessel in the midlumbar region redirecting blood flow away from the caudal vena cava and into the azygos vein. Balloon dilatation of the orifice within the cor triatriatum dexter membrane successfully reduced pressure within the caudal chamber of the right atrium and enhanced return via the caudal vena cava with subsequent resolution of clinical signs. This case report highlights the use of cross-sectional imaging in dogs with cor triatriatum dexter and unexpected contrast study results, as a means by which concurrent vascular anomalies may be identified.

Duplicated Inferior Vena Cava in a Patient With Ampullary Adenocarcinoma: A Case Report and Literature Review of Anatomical Variations

Duplicated inferior vena cava (IVC) is a rare anatomical anomaly as a result of failed regression of the left supracardinal vein during the embryonic stage. This anatomical variation has certain surgical implications and could lead to potential catastrophe perioperatively. We hereby report a case of a 54 years old male in whom a whipple procedure was performed with type 1 duplicated IVC for ampullary adenocarcinoma. Review of current literature of such anatomical anomaly will also be discussed. This venous anomaly must be kept in mind in all surgical procedures involving the retroperitoneum to minimise the risk of incomplete lymph node dissection and life-threatening bleeding, and to guide management for deep vein thrombosis in the post-operative setting.

Percutaneous Cava Stenting in a Dog with Symptomatic Azygos Continuation of the Caudal Vena Cava

This report describes the successful placement of a nitinol stent within the azygos continuation of the caudal vena cava in a 2-year-old, neutered female, English Bulldog with clinical and imaging signs related to venous return chronic obstruction, renal venous thrombi, and chronic renal insufficiency. This noninvasive, interventional radiology procedure was safe and clinically effective for the patient. The clinical signs were rapidly eliminated, and three years later, the patient is still in good clinical condition, with normal renal function. Venous stenting appears to be a useful, new, minimally invasive treatment option for symptomatic cavo-azygos vascular connection.

CT variants of the caudal vena cava in 121 small breed dogs

Computed tomography is increasingly used as a treatment planning method in canine patients with diseases of the retroperitoneum, however, published information on normal variations in the caudal vena cava (CVC) are currently lacking. The objectives of this retrospective descriptive study were to characterize CVC variants using CT angiography in a sample of small breed dogs and localize the CVC bifurcations for each variant. Inclusion criteria were small breed dogs (weight ≤ 15) that underwent contrast-enhanced CT scans of the CVC, abdominal aorta, and CVC tributaries. A total of 121 small breed dogs were sampled. Four right-sided and one left-sided CVC variations were identified: normal (88/121, 72.7%), caudal-partial split (17/121, 14.0%), partial duplication (8/121, 6.6%), complete duplication (7/121, 5.8%), and left-sidedness (1/121, 0.8%). The mean lumbar vertebral levels of the CVC bifurcation were L6.39 ± 0.41, L5.70 ± 0.35, L4.39 ± 0.42, L2.74 ± 0.38, and L6.4 in the normal, caudal-partial split, partial duplication, complete duplication, and left-sidedness types, respectively. The location of the CVC bifurcation, the relationship between the aortic trifurcation and the CVC bifurcation, and the location of the bilateral deep circumflex iliac veins with respect to the CVC bifurcation were significantly different among the right-sided types (P ≤ .001). Bilateral deep circumflex iliac veins joined to the ipsilateral common iliac veins and the CVC in the caudal-partial split and duplication types, respectively. The results of this study indicated that canine CVC variants may be frequent and should be considered during surgery or diagnostic imaging of the retroperitoneum.

Anomalies of the Portal Venous System in Dogs and Cats as Seen on Multidetector-Row Computed Tomography: An Overview and Systematization Proposal

This article offers an overview of congenital and acquired vascular anomalies involving the portal venous system in dogs and cats, as determined by multidetector-row computed tomography angiography. Congenital absence of the portal vein, portal vein hypoplasia, portal vein thrombosis and portal collaterals are described. Portal collaterals are further discussed as high- and low-flow connections and categorized in hepatic arterioportal malformation, arteriovenous fistula, end-to-side and side-to-side congenital portosystemic shunts, acquired portosystemic shunts, cavoportal and porto-portal collaterals. Knowledge of different portal system anomalies helps understand the underlying physiopathological mechanism and is essential for surgical and interventional approaches.

Common venous renal trunk in two dogs: Multidetector computed tomographic imaging findings

In dogs, variation in the branching pattern of renal veins is rare with only few patterns reported. This report describes two unusual anomalies of the renal vein branching patterns in two dogs. In dog 1, a common renal trunk drained both kidneys, in a T-shape pattern, in the caudal vena cava after a long right perirenal course. In dog 2, a common venous trunk branched cranially from the pre-renal segment of an azygos-caudal vena cava venous trunk and divided into the renal veins in a Y-shape pattern. Proper knowledge of the possible anatomical variations in renal venous drainage may be helpful during imaging assessment and surgical planning of several canine diseases involving the abdominal vasculature and retroperitoneal space.

Infrahepatic inferior caval and azygos vein formation in mammals with different degrees of mesonephric development

Controversies regarding the development of the mammalian infrahepatic inferior caval and azygos veins arise from using topography rather than developmental origin as criteria to define venous systems and centre on veins that surround the mesonephros. We compared caudal-vein development in man with that in rodents and pigs (rudimentary and extensive mesonephric development, respectively), and used Amira 3D reconstruction and Cinema 4D-remodelling software for visualisation. The caudal cardinal veins (CCVs) were the only contributors to the inferior caval (IVC) and azygos veins. Development was comparable if temporary vessels that drain the large porcine mesonephros were taken into account. The topography of the CCVs changed concomitant with expansion of adjacent organs (lungs, meso- and metanephroi). The iliac veins arose by gradual extension of the CCVs into the caudal body region. Irrespective of the degree of mesonephric development, the infrarenal part of the IVC developed from the right CCV and the renal part from vascular sprouts of the CCVs in the mesonephros that formed 'subcardinal' veins. The azygos venous system developed from the cranial remnants of the CCVs. Temporary venous collaterals in and around the thoracic sympathetic trunk were interpreted as 'footprints' of the dorsolateral-to-ventromedial change in the local course of the intersegmental and caudal cardinal veins relative to the sympathetic trunk. Interspecies differences in timing of the same events in IVC and azygos-vein development appear to allow for proper joining of conduits for caudal venous return, whereas local changes in topography appear to accommodate efficient venous perfusion. These findings demonstrate that new systems, such as the 'supracardinal' veins, are not necessary to account for changes in the course of the main venous conduits of the embryo.

Left Retrocaval Ureter around the Ipsilateral Limb of a Double Caudal Vena Cava in a Cat

Necropsy examination of an adult neutered male cat, which was humanely destroyed as it had feline immunodeficiency virus (FIV) infection, demonstrated the presence of a left retrocaval ureter that was entrapped around the left limb of a double caudal vena cava. These associated anomalies originate from the complex embryofetal development of the caudal vena cava. Since no clinical signs had been reported and no gross lesions related to this anomaly were observed, this manifestation should be simply considered as an anatomical variation.

Development of the human infrahepatic inferior caval and azygos venous systems

Differences in opinion regarding the development of the infrahepatic inferior caval and azygos venous systems in mammals centre on the contributions of 'caudal cardinal', 'subcardinal', 'supracardinal', 'medial and lateral sympathetic line' and 'sacrocardinal' veins. The disagreements appear to arise from the use of topographical position rather than developmental origin as criterion to define separate venous systems. We reinvestigated the issue in a closely spaced series of human embryos between 4 and 10 weeks of development. Structures were visualized with the Amira(®) reconstruction and Cinema4D(®) remodelling software. The vertebral level and neighbouring structures were used as topographic landmarks. The main results were that the caudal cardinal veins extended caudally from the common cardinal vein between CS11 and CS15, followed by the development of the subcardinal veins as a plexus sprouting ventrally from the caudal cardinal veins. The caudal cardinal veins adapted their course from lateral to medial relative to the laterally expanding lungs, adrenal glands, definitive kidneys, sympathetic trunk and umbilical arteries between CS15 and CS18, and then became interrupted in the part overlaying the regressing mesonephroi (Th12-L3). The caudal part of the left caudal cardinal vein then also regressed. The infrarenal part of the inferior caval vein originated from the right caudal cardinal vein, while the renal part originated from subcardinal veins. The azygos veins developed from the remaining cranial part of the caudal cardinal veins. Our data show that all parts of the inferior caval and azygos venous systems developed directly from the caudal cardinal veins or from a plexus sprouting from these veins.

Prevalence of circumcaval ureters and double caudal vena cava in cats

OBJECTIVE

To determine the prevalence of circumcaval ureters and other caudal vena cava variations in cats and determine whether circumcaval ureters were associated with macroscopic evidence of ureteral obstruction.

SAMPLE

301 domestic cat cadavers obtained from an animal shelter.

PROCEDURES

All cat cadavers were examined, and anatomic variations of the ureters and caudal vena cava were recorded. In cadavers with a circumcaval ureter, kidney length, width, and height were measured, and the ureters were examined macroscopically to determine whether there was gross evidence of ureteral obstruction in cats with circumcaval ureters.

RESULTS

At least 1 circumcaval ureter was present in 106 of the 301 (35.2%) cats, with a right circumcaval ureter identified in 92 (30.6%) cats, a left circumcaval ureter identified in 4 (1.3%), and bilateral circumcaval ureters identified in 10 (3.3%). Twenty-one (7.0%) cats had a double caudal vena cava, including 2 cats in which the double caudal vena cava was the only anatomic abnormality identified. No sex predilection for anatomic abnormalities was found. Mean right kidney length was significantly greater than mean left kidney length in cats with a right circumcaval ureter.

CONCLUSIONS AND CLINICAL RELEVANCE

Circumcaval ureter was present in approximately a third of cats in this study. Variation in the development of the caudal vena cava is the proposed cause. The clinical relevance of this variation is unknown.

Situs ambiguus in a Brown Swiss cow with polysplenia: case report

Background

Laterality defects are rare in cattle and usually manifest as asplenia or polysplenia syndrome. These syndromes may be associated with situs ambiguus, which is a dislocation of some but not all internal organs. The objective of this report was to describe the clinical and post-mortem findings including the macroscopic and microscopic anatomy of selected organs in a cow with polysplenia and situs ambiguus.

Case presentation

A 3.5-year-old Brown Swiss cow was referred to the Department of Farm Animals, Vetsuisse Faculty, University of Zurich, because of poor appetite and recurrent indigestion. A diagnosis of situs ambiguus was based on the results of physical examination, ultrasonography, exploratory laparotomy and post-mortem examination. The latter revealed that the rumen was on the right side and lacked compartmentalisation. There were two spleens, one on the left (26.5 x 12.0 cm) and one on the right (20.5 x 5.5 cm), and the omasum was located craniolateral to the ruminoreticulum on the left. The abomasum was located on the right, although it had initially been displaced to the left. The three-lobed liver occupied the left and central cranioventral aspect of the abdominal cavity (cavum abdominis). Only the right and left hepatic veins (vena hepatica dextra and sinistra) drained into the thoracic segment of the caudal vena cava (vena cava caudalis), and histological changes in the liver were indicative of impaired haemodynamics. The mesojejunum was not fused with the mesentery of the spiral loop (ansa spiralis) of the ascending colon (colon ascendens). The latter was folded and the transverse colon (colon transversum) ran caudal to the cranial mesenteric artery (arteria mesenteria cranialis). Fibrotic constrictions were seen in the lumen of the caecum and proximal loop (ansa proximalis) of the ascending colon. Both kidneys were positioned retroperitoneally in a lumbar position. The lumbar segment of the caudal vena cava did not descend to the liver and instead drained into the right azygous vein (vena azygos dextra).

Conclusions

Recurrent digestive problems and poor production in this patient may have been caused by a lack of rumen compartmentalisation, abnormal abomasal motility, constrictions in the large intestine (intestinum crassum) and fibrosis of the liver. The abomasum had abnormal motility most likely because it was anchored inadequately and only at its cranial aspect to the liver by the lesser omentum (omentum minus) and to the dorsal abdominal wall and rumen by a short greater omentum (omentum majus).

Computed tomography findings in portal vein aneurysm of dogs

In this retrospective study, the appearances of extrahepatic and intrahepatic portal vein aneurysms (PVAs) in dogs were evaluated using multidetector computed tomography (CT). Data from 3060 dogs that underwent abdominal CT were reviewed for focal portal vein dilatation. PVAs were detected in 15/3060 (0.49%) dogs. The bodyweights of dogs with PVAs were significantly higher than the bodyweights of dogs without aneurysms (P=0.0001). Male sex was also significantly associated with PVAs (OR=6.23). Boxers were predisposed to the development of PVA (OR=11.88). Extrahepatic PVAs were always located in the portal vein at the level of the gastroduodenal vein insertion and were saccular in 10/15 dogs and fusiform in 5/15 dogs. One dog had an additional intrahepatic aneurysm of the umbilical part of the left intrahepatic portal branch. No dogs had clinical signs related to the PVA(s), although one dog developed a portal vein thrombosis in the site of the aneurysm.

Origin of the infrarenal part of the caudal vena cava in the pig

The vascular topography in the lumbar region of pig embryos and young fetuses was three-dimensionally reconstructed to study some controversial aspects of the origin and development of the infrarenal part of the caudal vena cava. Contrary to general belief, it was found that the supracardinal veins, which form the azygos veins in the thorax, do not take part in the construction of the caudal vena cava in the lumbar region. These veins do appear in the abdomen, but they are only involved in the formation of the lumbar and ascending lumbar veins. The infrarenal part of the caudal vena cava arises from the lumbar part of the right caudal cardinal vein. Whilst this venous pattern is established, the lumbar part of the left caudal cardinal vein disappears and its former location is occupied by large lymphatic connections between the cysterna chyli and the retroperitoneal mesenteric lymphatic sac. On the basis of these findings, a number of hypotheses on the development of anatomical variations of the caudal vena cava should be reconsidered.