Classification of portosystemic shunts entering the caudal vena cava at the omental foramen in dogs.

OBJECTIVE: To re-evaluate the anatomy and classification of congenital extrahepatic portosystemic shunts entering the caudal vena cava at the level of the omental foramen. MATERIAL AND METHODS: A retrospective review of a consecutive series of dogs undergoing CT angiography as part of the diagnostic work-up for a congenital extrahepatic portosystemic shunt. RESULTS: In total, 53 dogs met the inclusion criteria revealing four anatomically distinct omental foramen shunt types; one of which (32 of 53 dogs) showed no shunting blood flow through the right gastric vein and three of which (21 of 53 dogs) involved shunting flow through this vessel. The anatomy of these four distinct shunt types, as defined by CT angiography, was found to be highly consistent. In all cases, regardless of the tributary vessels, the left gastric vein was the final vessel that communicated with the caudal vena cava. Using these findings, a more accurate naming classification for congenital portosystemic shunts entering the caudal vena cava at the level of the omental foramen was proposed. CLINICAL SIGNIFICANCE: A precise pre-treatment anatomical classification of congenital extrahepatic portosystemic shunts entering the caudal vena cava at the level of the omental foramen is important for a more complete understanding of the severity of clinical signs and prognosis, and for the better communication between clinicians and researchers in this clinical field.

Modified functional end-to-end stapled intestinal anastomosis: technique and clinical results in 15 dogs.

OBJECTIVES: To evaluate the use of a gastrointestinal anastomosis (GIA) stapling device to perform small intestinal anastomosis in the dog. METHODS: A retrospective study to evaluate the use of a GIA stapling device to perform small intestinal anastomosis in 15 dogs. RESULTS: Reasons for intervention included dehiscence of a previous enterotomy (four of 15), intestinal neoplasia (five of 15), vascular compromise (three of 15), intussusception (two of 15) and foreign body (one of 15). The mean time taken to perform the anastomosis was 7.7 minutes (range five to 12 minutes). No operative complications were recorded and all dogs recovered from the surgery. Major (two dogs) and minor (six dogs) short-term complications of pyrexia and anorexia were recorded in six dogs. In five of these, the cause was considered to be related to a pre-existing peritonitis. One dog was euthanased five months postoperatively for a multi-centric recurrence of intestinal lymphoma. Six month follow-up confirmed an unremarkable and complete recovery in all remaining dogs. No major or minor long-term complications were recorded in any individual. CLINICAL SIGNIFICANCE: A modified stapled functional end-to-end intestinal anastomosis holds merit and should be considered a viable alternative to other stapled and sutured anastomosis techniques.

Post-temporary ligation intraoperative mesenteric portovenography: comparison with CT angiography for investigation of portosystemic shunts.

OBJECTIVES: Comparison of pre-operative CT angiography and post-temporary, full-ligation, intraoperative, mesenteric portovenography for the characterisation of intrahepatic portal vasculature in patients with single extrahepatic portosystemic shunts. METHODS: Descriptive analysis of previously collected images from 14 dogs and five cats. RESULTS: With the exception of shunts involving the right gastric vein, intrahepatic arborisation appeared similar on both modalities. Portovenography improved contrast enhancement and slightly enlarged the intrahepatic portal vasculature. CLINICAL SIGNIFICANCE: CT angiography cannot replace intraoperative mesenteric portovenography after temporary full ligation, which provides information on intrahepatic portal vascularity. It is a practical and dynamic procedure, providing results that are instantaneously available at the time of surgery. In addition, intraoperative post-temporary, full-ligation, mesenteric portography confirmed that the single shunting vessel had both been recognised and ligated.

Implications of shunt morphology for the surgical management of extrahepatic portosystemic shunts.

OBJECTIVE: To describe the implications of extrahepatic portosystemic shunt morphology for the chosen site of shunt closure in dogs and cats. METHODS: A retrospective review of a consecutive series of dogs and cats managed for congenital extrahepatic portosystemic shunts. RESULTS: In total, 54 dogs and 10 cats met the inclusion criteria, revealing five distinct shunt types: left gastrophrenic, right gastrocaval (types Ai, Aii and Aiii), splenocaval, colocaval and left gastro-azygos. Without exception, findings of computed tomography angiography and direct gross observations at the time of surgery confirmed four consistent sites of communication between the anomalous shunting vessel and the systemic venous system: the caudal vena cava at the level of the epiploic foramen; the left phrenic vein at the level of the oesophageal hiatus; the azygos vein at the level of the aortic hiatus; and the caudal vena cava or iliac vein at the level of the 6th or 7th lumbar vertebrae. The use of intraoperative mesenteric portography was effective for confirming that at the time of surgery all portal tributary vessels were proximal to the point of shunt attenuation. CONCLUSIONS: Findings confirmed that for the common types of extrahepatic portosystemic shunts there were only four consistent sites of communication between the shunt and the systemic venous system. This information supports the use of a systematic approach for the location and attenuation of shunts in dogs and cats.

Improved survival in a retrospective cohort of 28 dogs with insulinoma.

OBJECTIVES: To determine the survival times for a cohort of dogs with insulinoma and to describe the impact of medical therapy both in non-surgical cases and in surgical cases following relapse. METHODS: A retrospective study of dogs with insulinoma is presented. The Kaplan-Meier method is used to evaluate the survival characteristics of this population. RESULTS: Twenty-eight dogs were included in the study. The median survival time for all dogs was 547 days. Nineteen patients underwent partial pancreatectomy. The median survival time for this group was 785 days and for those subsequently receiving prednisolone therapy on relapse it was 1316 days. Perioperative complications are discussed. CLINICAL SIGNIFICANCE: Survival times in this study exceed those in other studies published previously. In part, this is explained by an improved remission duration following surgery compared with previous reports. More striking though is the longevity of patients following institution of medical therapy. These data give strong objective support to the role of medical therapy in the management of canine insulinoma, including following relapse after surgically induced remission.

Comparison of computed tomographic angiography and intraoperative mesenteric portovenography for extrahepatic portosystemic shunts.

OBJECTIVES: Comparison of intra-operative mesenteric portovenography and computed tomographic angiography for the documentation of the portal vasculature in patients with single extrahepatic portosystemic shunts. METHODS: Retrospective study of patients with extrahepatic portosystemic shunts that underwent preoperative computed tomographic angiography and intra-operative mesenteric portography. Studies were compared for identification of the intra- and extrahepatic portal vasculature. RESULTS: Computed tomographic angiography demonstrated all four portal vein tributaries and sub-tributaries. Intra-operative mesenteric portography inconsistently demonstrated the cranial mesenteric vein, the gastroduodenal vein (12 of 49 dogs and 0 of 10 cats), splenic vein (46 of 49 dogs and 8 of 10 cats) and caudal mesenteric vein (3 of 49 dogs and 2 of 10 cats). Computed tomographic angiography showed the intrahepatic portal vein with shunts emanating from the left gastric vein, splenocaval shunts or shunts involving the left colic vein. It showed intrahepatic portal branching in 5 of 12 patients with shunts involving the right gastric vein. Intra-operative mesenteric portography showed the intrahepatic portal vein in 29 of 59 patients but was outperformed by computed tomographic angiography in all cases except those patients with a shunt involving the right gastric vein. CLINICAL SIGNIFICANCE: In cases that have undergone diagnostic preoperative computed tomographic angiography there is no indication for diagnostic intra-operative mesenteric portovenography before ligation. In contrast, portovenography performed "after" temporary full ligation of the shunt provides clinical useful information and might be considered an integral investigation during shunt attenuation surgery.

New perspectives on the development of extrahepatic portosystemic shunts.

In this essay we use clinical evidence and knowledge of anatomy to examine the relationship between blood flow and formation of congenital extrahepatic portosystemic shunts in dogs and cats. First we report on the clinical findings in a series of 50 dogs and 10 cats and then systematically review peer-reviewed data on the detailed anatomy of shunts in dogs and cats. In dogs four types of shunt: spleno-caval, left gastro-phrenic, left gastro-azygos and those involving the right gastric vein account for 94% of extrahepatic shunts. Cats also exhibit four types of shunt: spleno-caval, left gastrophrenic, left gastro-caval and left gastro-azygos, and the first three of these account for 92% shunts in this species. Our findings lead us to propose that preferential blood flow influences the subsequent formation of one of a number of defined and consistent congenital extrahepatic portosystemic shunts in dogs and cats.

Morphology of splenocaval congenital portosystemic shunts in dogs and cats.

OBJECTIVE: To describe the anatomy of congenital portosystemic shunts involving the splenic vein communicating with the caudal vena cava at the level of the epiploic foramen. MATERIALS AND METHODS: A retrospective review of a consecutive series of dogs and cats managed for congenital portosystemic shunts. RESULTS: Ninety-eight dogs and eight cats met the inclusion criteria of a congenital portosystemic shunt involving the splenic vein communicating with the prehepatic caudal vena cava plus recorded intra-operative mesenteric portovenography or computed tomography angiography and gross observations at surgery. All cases (both dogs and cats) had a highly consistent shunt that involved a distended gastrosplenic vein that communicated with the caudal vena cava at the level of the epiploic foramen via an anomalous left gastric vein. CLINICAL SIGNIFICANCE: The morphology of the shunt type described appeared to be a result of an abnormal communication between the left gastric vein and the caudal vena cava and the subsequent development of preferential blood flow through an essentially normal portal venous system. The abnormal communication (shunt) was through the left gastric vein and not the splenic vein, as might have been expected. This information may help with surgical planning in cases undergoing shunt closure surgery.

Morphology of congenital portosystemic shunts involving the left colic vein in dogs and cats.

OBJECTIVE: To describe the anatomy of congenital portosystemic shunts involving the left colic vein in dogs and cats. METHODS: Retrospective review of a consecutive series of dogs and cats managed for congenital portosystemic shunts. For inclusion a shunt involving the left colic vein with recorded intraoperative mesenteric portovenography or computed tomography angiography along with direct gross surgical observations at the time of surgery was required. RESULTS: Six dogs and three cats met the inclusion criteria. All cases had a shunt which involved a distended left colic vein. The final communication with a systemic vein was variable; in seven cases (five dogs, two cats) it was via the caudal vena cava, in one cat it was via the common iliac vein and in the remaining dog it was via the internal iliac vein. In addition, two cats showed caudal vena cava duplication. CLINICAL SIGNIFICANCE: The morphology of this shunt type appeared to be a result of an abnormal communication between either the left colic vein or the cranial rectal vein and a pelvic systemic vein (caudal vena cava, common iliac vein or internal iliac vein). This information may help with surgical planning in cases undergoing shunt closure surgery.

Portal vein anatomy in the dog: comparison between computed tomographic angiography (CTA) and intraoperative mesenteric portovenography (IOMP).

OBJECTIVES: To compare and contrast the findings of intra-operative mesenteric portovenography (IOMP) and computed tomography angiography (CTA) for the visualisation and identification of the extrahepatic and intrahepatic portal venous system in the normal dog. METHODS: Retrospective study of dogs with raised post-prandial bile acids concentrations, normal portal venous pressures and grossly normal portal vasculature that had undergone both CTA and IOMP was performed. Images and video were compared with the published anatomic literature. RESULTS: Ten dogs met the inclusion criteria. CTA documented the portal vein and its tributaries in all 10 dogs. IOMP documented the portal vein and the cranial mesenteric vein in all 10 dogs and the splenic vein in 1 dog but failed to show the caudal mesenteric and gastroduodenal veins in any dog. CTA documented more extrahepatic portal venous tributaries than IOMP. Both techniques documented the intrahepatic portal vasculature completely with equal clarity. CLINICAL SIGNIFICANCE: There was a large difference between the ability of the two techniques to delineate the normal portal vasculature; CTA consistently visualised the extrahepatic portal vasculature more completely than the IOMP and, as such, might be considered the modality of choice for imaging the normal portal vasculature in the dog.

Morphology of congenital portosystemic shunts involving the right gastric vein in dogs.

OBJECTIVE: To describe the anatomy of congenital portosystemic shunts involving the right gastric vein in dogs. MATERIALS AND METHODS: Retrospective review of a consecutive series of dogs managed for congenital portosystemic shunt. RESULTS: Twenty-two dogs met the inclusion criteria of a congenital portosystemic shunt involving the right gastric vein with recorded intraoperative mesenteric portovenography or computed tomography angiography and gross observations at the time of surgery. Of these, 20 (91%) had a shunt that entered the pre-hepatic caudal vena cava at the level of the epiploic foramen and two (9%) had a shunt that entered the post-hepatic caudal vena cava at the level of the diaphragm. Shunts entering the pre-hepatic caudal vena cava could be further classified into three consistent subdivisions. CLINICAL SIGNIFICANCE: The morphology of each shunt type described appeared to be a result of an abnormal communication between the left gastric vein and the caudal vena cava, the presence or absence of an abnormal communication between the splenic, left gastric and portal veins and the subsequent development of preferential blood flow through essentially normal portal vessels within the portal venous system. The abnormal communication (shunt) was through the left gastric vein and not the right gastric vein, as might have been expected. This information may help with surgical planning in cases undergoing shunt closure surgery.

The effect of temperature on myogenesis in embryonic development of the Atlantic salmon (Salmo salar L.).

From fertilisation to hatching one group of salmon embryos was reared at ambient temperatures (fluctuating around 1.6 degrees C) and another at 10 degrees C. At Gorodilov stages 28, 30 and 33 transverse sections of whole embryos were obtained for light and electron microscopy. Total cross-sectional areas, fibre numbers, fibre diameters and myofibrillar areas of the white muscle of m. lateralis were measured. At hatching (stage 33, which occurred much earlier at the higher temperature), the higher temperature embryos had significantly larger (P less than 0.01) but fewer (P less than 0.05) muscle fibres. These larger fibres contained significantly more myofibrillar material (P less than 0.05) than the smaller fibres of the lower temperature embryos. Lesser differences were found at pre-hatching stages. Higher temperatures caused myofibre hypertrophy to increase at a greater rate than hyperplasia. Hence, the cellularity of the tissue produced under the different temperature regimes was quite different.

The angiographic anatomy of the portal venous system in the neonatal dog.

The angiographic anatomy of the portal venous system in 50 dead, neonatal Labrador/Retriever type puppies is described. Angiography was performed by the injection of radioopaque contrast media through a catheter placed within the umbilical vein. In 49 pups the ductus venosus was a straight vessel arising from the left main portal vein and terminating in an ampulla into which the left hepatic and left phrenic veins entered prior to the ampulla entering the caudal vena cava. The diameter of the ductus venosus was significantly narrower (P<0.001) in pups born alive (n=10) when compared to stillborn individuals (n=39). No discreet narrowing of the ductus venosus indicating a sphincter was found, with closure appearing to be uniform along the vessel's length. A well-developed, patent portal venous system was present in the majority of individuals. One pup showed variation from the others studied having a vascular connection between the portal sinus and the vena cava within the liver. This may represent a normal variant of the ductus venosus, or may be an anatomical abnormality leading to the development of an intrahepatic portosystemic shunt. If this was an intrahepatic shunt, no concurrent ductus venosus was present.

Iron status and erythrocyte volume in dogs with congenital portosystemic vascular anomalies.

Microcytosis, hypochromasia, and low mean corpuscular hemoglobin are frequent hematologic abnormalities in dogs with portosystemic vascular anomalies (PSVA). The relationship of iron status to these abnormalities is unclear. We evaluated iron status and hematologic and biochemical parameters in dogs with congenital PSVA before (25 dogs) and after (11 dogs) partial ligation of the vascular anomaly. Serum iron concentration and total iron binding capacity were subnormal in 56% and 20% of dogs with PSVA, respectively. Transferrin saturation was normal in 68%, decreased in 20%, and increased in 12% of the dogs. Plasma ferritin concentration was either normal (56%) or high (44%), and was not associated with increases in ceruloplasmin concentration. Hepatic stainable iron was increased in 10 of 16 dogs. Mean corpuscular volume (MCV), mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration were decreased in more than 60% of dogs with PSVA. Serum biochemical abnormalities included high bile acid concentration and alanine transaminase (ALT) and alkaline phosphatase (ALP) activities; and low urea, creatinine, cholesterol, and total protein concentrations. Serum iron concentration and clinical status (normal or PSVA) significantly influenced MCV (P = .003 and P < .001, respectively), whereas age, ceruloplasmin, ferritin, cholesterol, bile acids, and total iron binding capacity did not. Partial ligation of PSVA was associated with resolution of clinical signs and the return to normal of iron status and all clinicopathologic abnormalities, except total fasting bile acid concentrations. These findings indicate that iron status is frequently abnormal in dogs with PSVA and that low serum iron concentration appears to be related to the development of microcytosis. The normalization of iron status and clinicopathologic abnormalities after treatment suggests that they are direct consequences of PSVA.

Surgical management of constipation.

There are many recognised causes of constipation in the cat and the management of the condition depends on the clinician's ability to recognise the appropriate aetiology in each case. Most surgery therapies for constipation in the cat are related to the management of idiopathic megacolon, although causes such as pelvic outlet obstruction, complications of neutering surgery, perineal herniation, and malunion pelvic fractures may also require surgical intervention. Currently, the surgical management of megacolon consists of subtotal colectomy with the recommendation that the ileocolic junction be preserved. The procedure, in general, is associated with few life-threatening complications although the majority of individuals will experience a transient period of loose stool formation in the immediate post-operative period. In the majority of cases, the long-term outcome following subtotal colectomy is considered excellent.

Anatomy of the patent ductus venosus in the cat.

The biplanar mesenteric vein portovenograms of 10 cats with left divisional intrahepatic portosystemic shunts consistent with a patent ductus venosus (PDV) were reviewed. A corrosion cast of the hepatic portal vasculature was made post mortem from one individual that died post operatively following surgical attenuation of the shunting vessel. On the basis of the combined surgical, post mortem and imaging data, these left divisional shunts were found to have consistent anatomy, each having a straight vessel which drained into a venous ampulla before draining into the caudal vena cava at the level of the diaphragm. The left phrenic vein and left hepatic vein both entered the ampulla independently of the shunting vessel. The anatomical similarity between these findings in the cat and the PDV in the dog suggest that it is appropriate to describe this particular portosystemic shunt as a PDV.

Cholelithiasis and hyperthyroidism in a cat.

A 14-year-old domestic short-hair cat presented with a history of intermittent malaise and increased drinking. A diagnosis of hyperthyroidism and cholelithiasis was made by a combination of blood testing, radiography and ultrasonography. After medical management of hyperthyroidism, thyroidectomy and cholecystectomy were successfully performed. Removed choleliths were comprised of calcium carbonate and bilirubinate. Histopathological analysis of tissue suggested low grade pancreatic and hepatobiliary disease, as well as hyperthyroidism, might have contributed to stone formation.

Anatomy of the patent ductus venosus in the dog.

The biplanar umbilical vein portovenograms of 49 newborn puppies and the biplanar mesenteric vein portovenograms, obtained during surgery, of 42 adult dogs with left divisional intrahepatic portosystemic shunts consistent with a patent ductus venosus (PDV) were reviewed. On the basis of the combined surgical, postmortem and imaging data, the left divisional intrahepatic portosystemic shunts were consistent, each having a straight vessel which drained into a venous ampulla before draining into the caudal vena cava at the level of the diaphragm. The left phrenic vein and the left hepatic vein both entered the ampulla independently of the shunting vessel. The morphology of the ductus venosus in the pups was similar and consistent with the morphology of the left divisional intrahepatic PDV shunt of the adult dogs. It is concluded that this form of left divisional shunt is correctly named a PDV and is the result of the persistence of the fetal ductus venosus. From the surgical records it is concluded that all the shunts described as a PDV were attenuated by the direct manipulation of the ductus venosus before its entry into the ampulla.

Morphology of congenital intrahepatic portacaval shunts in dogs and cats.

The preoperative ultrasound images and biplanar operative mesenteric portograms of 28 dogs and six cats with congenital intrahepatic portacaval shunts were reviewed retrospectively. On the basis of the combined surgical, postmortem and imaging data, the shunts were classified according to their location within the liver and their shape. Thirteen dogs and four cats had a left-divisional shunt with a relatively consistent bent tubular shape that drained into the left hepatic vein. Another 13 dogs had a central-divisional shunt that took the form of a foramen between dilated portions of the intrahepatic portal vein and caudal vena cava. One cat with a central-divisional shunt had a tortuous vessel. The remaining two dogs and one cat had right-divisional shunts that were large, tortuous vessels. The morphology of a left-divisional shunt is compatible with patent ductus venosus, but the pathogenesis of central and right-divisional shunts is unknown. It is concluded that intrahepatic portacaval shunts in dogs and cats may be classified as left, central or right divisional. Ultrasound enables a preoperative morphological assessment that correlates well with the results of portography and may aid surgical planning.

An application of sinography in small animal practice.

Sinography is a well recognised aid to clinical diagnosis in human medicine; it is used in equine practice but is less commonly used in small animal practice. The technique was used to investigate four dogs with sinuses associated with radiolucent foreign bodies secondary to penetration wounds.