ANATOMY OF THE PORTAL AND HEPATIC VEINS OF THE DOG: A BASIS FOR SYSTEMATIC EVALUATION OF THE LIVER BY ULTRASONOGRAPHY

The objective of this study was to define, in detail, the anatomy of the portal and hepatic veins in the dog in order to establish a procedure for the systematic evaluation of the liver by ultrasonography. Anatomical details were obtained from the formalin fixed livers of ten dogs. The hepatic and portal veins were removed intact from these livers so that a detailed pattern of distribution could be established and the numbers of branches could be counted. Silastic casts were also made of the hepatic and portal veins of two livers, one in situ and one in which it had been removed. The former was to enable the relationship of the portal to the hepatic veins to be established as closely as possible within the animal and the other to provide a model of the distribution of each venous system within the liver. Contrast medium was infused into two other livers and radiographs taken to establish the relationship of each branch to each lobe. It was found that there was a consistent pattern of venous branching to each lobe of the liver in the dog with little variation between individual specimens. All liver lobes contained definite venous branches so that the left lateral and medial, quadrate, right medial and lateral, caudate and papillary veins could be distinguished in each venous system. We believe that an appreciation of this venous distribution will aid in the systematic evaluation of the liver during ultrasonography by enabling identification of each liver lobe. It should be of value for differentiating portal from hepatic veins and veins from dilated bile ducts.     

Ultrasonographic differentiation between portal venous and parenchymal gas may be important for the prognosis of canine and feline hepatic emphysema: 37 cases

The aim of this retrospective, cross‐sectional, study was to evaluate clinical findings and outcomes for different ultrasonographic patterns of hepatic emphysema in dogs and cats. Dogs and cats with an ultrasonographic diagnosis of hepatic emphysema and a known outcome, from January 2010 to January 2018, were enrolled. The following data were recorded from medical and ultrasonographic records: ultrasonographic patterns of hepatic emphysema (parenchymal, portal venous, biliary), clinical signs, laboratory findings, and outcomes (favorable, poor). A total of 33 dogs and four cats met the inclusion criteria. Among these, 23 cases were classified as hepatic portal venous gas, 10 as parenchymal emphysema, and four as biliary emphysema. Clinical diagnosis categories were as follows: infection/sepsis (9), gastro‐intestinal disease (9), iatrogenic (9), trauma (5), and liver neoplasia (5). An increase in serum liver enzymes was significantly associated with parenchymal emphysema (P = .03). Other clinical and laboratory findings were not associated with the type of hepatic emphysema. Hepatic portal venous gas was mostly transient in patients with ultrasonographic follow‐up. The overall mortality was 40.5%. A significant difference was found between mortality by portal venous gas (21.7%) and mortality by parenchymal emphysema (90%) (P = .003). In conclusion, the ultrasonographic differentiation of hepatic emphysema between hepatic portal venous gas and parenchymal emphysema may be important for the prognosis of hepatic emphysema. The presence of parenchymal emphysema may be a poor prognostic indicator, while hepatic portal venous gas may be more benign. However, ultrasound findings should be carefully evaluated in the context of clinical findings.     

Radiography and ultrasonography of pneumatosis intestinalis in a cat

An adult cat was presented for acute history of vomiting and collapse. Radiographs showed the presence of air within small intestinal walls and arborizing gas patterns within the liver, compatible with pneumatosis intestinalis and presumed portal venous gas, respectively. An abdominal ultrasound the following day was suggestive of gas within the intestinal wall, however, gas within the hepatic vasculature, parenchyma, or biliary tree was not evident. Due to progressive clinical deterioration of the patient, the owners elected humane euthanasia. Necropsy revealed severe necrotizing hemorrhagic enterotyphlocolitis secondary to Clostridium difficile toxin.     

E．stiedai感染兔免疫器官内球虫抗原的免疫组化定位

用免疫组化SABC法，对斯氏艾关耳球虫感染后兔肝脏、脾脏和肝门淋巴结中球虫抗原的分布进行了观察。结果表明，在肝脏窦状隙、胆管上皮细胞、肝门淋巴结和脾脏内可见到明显的呈棕黄色阳性反应区，表明在这些区域和部位有相应的E．stiedai孢子囊、裂殖子或子孢子抗原存在，且抗原数量以肝脏内最多，其次为脾脏，最少者为肝门淋巴结；显微镜下还可见到大量坏死的肝细胞、淋巴细胞以及朗罕氏巨细胞，说明多核巨细胞也参与了对球虫的吞噬和处理过程。     

Hepatic lesions associated with intrahepatic arterioportal fistulae in dogs

Seven cases of hepatic arterioportal fistulae in young dogs (mean age 6 months) are described. All cases were presumed to be congenital in origin. The onset of clinical signs, which frequently included gastrointestinal and neurological disturbances, was usually sudden. All dogs had clinical evidence of portal hypertension in the form of ascites, and all developed multiple extrahepatic portacaval venous shunts consequential to portal hypertension. The neurological disturbances were likely the result of portacaval shunting. The arterial and venous vessels involved in the fistulae had markedly altered wall structure. Hepatic regions adjacent to the fistulae frequently evidenced marked bile duct proliferation. Hepatic parenchymal atrophy, relative collapse of distributing portal veins, dilatation of hepatic arterial branches and proliferation of hepatic arterioles were seen throughout the liver; these changes closely resembled those present with portacaval shunting in the absence of hepatic arterioportal fistulae. The importance of recognizing that hepatic arterioportal fistulae and multiple extrahepatic portacaval shunts usually coexist and separately influence the morphological appearance of the liver is stressed.     

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.     

TRANS-SPLENIC PORTAL SCINTIGRAPHY IN NORMAL DOGS

The purpose of this study was to (1) establish a technique for ultrasound-guided trans-splenic portal scintigraphy (TSPS) using 99mTcO4(-), (2) evaluate portal vein morphology, (3) compare the radiation exposures for TSPS vs. per-rectal portal scintigraphy (PRPS), and (4) compare the quality of numerical data from the TSPS vs. PRPS. Eight juvenile dogs underwent PRPS and TSPS (minimum of 48h between studies) after initial screening tests. PRPS was done according to established protocol using 425 +/- 36MBq (mean +/- SD) of 99mTcO4(-). TSPS was done with the dogs in right lateral recumbency over the gamma camera. 99mTcO4(-) (57 +/- 13.9 MBq) was injected into the spleen 1-2s following initiation of the dynamic acquisition. The frame rate was 4 frames/s for 5 min. There was significantly lower radioactivity of 99mTcO4(-) given and significantly higher total counts recorded in the liver and heart during the TSPS compared with PRPS. The total counts for the TSPS and PRPS were 7120 +/- 4386 and 830 +/- 523, respectively. Percent absorption from the spleen was 52.5 +/- 19.1% compared with 9.2 +/- 5.7% for the colon. Calculated transit time for the TSPS studies was 7 +/- 2.3s. In TSPS studies, the splenic and portal veins were clearly identified. Radiation exposure levels of the dogs were significantly lower following TSPS than after PRPS. TSPS appears superior to PRPS as a method to image the portal venous system representing a valid alternative diagnostic test for animals with suspected portosystemic shunts.     

ANGIOGRAPHY OF THE HEPATIC AND PORTAL VENOUS SYSTEM IN THE DOG AND CAT: AN INVESTIGATIVE METHOD*

The investigators studied the hepatic angiographic technics used in human medicine with respect to their applicability for the investigation of circulatory liver diseases in the dog and cat. The technics were performed in 11 normal dogs and 2 normal cats, and the normal radiographic anatomy of the hepatic portal system and its tributaries was described. The potential indications for the angiographic technics were defined and their respective advantages and disadvantages discussed. Splenoportography was a valuable method for outlining the intrahepatic portal vein branches and for percutaneous prehepatic portal vein pressure determination. Percutaneous transhepatic portography was more difficult to perform, but it provided better detail of the intrahepatic portal veins than splenoportography. Transjugular transhepatic portography was the most versatile but also the most cumbersome of all technics tested. Percutaneous kinetic hepatography proved impractical in dogs and cats. The mesenteric tributaries to the hepatic portal system were best outlined by cranial mesenteric arterial portography or by operative mesenteric venous portography. Operative mesenteric venous portography, in contrast to cranial mesenteric arterial portography, was also useful for prehe-patic portal vein pressure determination. Free and wedged hepatic venography provided an opportunity for the functional and morphologic investigation of the hepatic sinusoid circula-tion.     

Ultrasonography of the spleen,liver, gallbladder,caudal vena cava and portal vein in healthy calves from birth to 104?days of age

Background

Many of the ultrasonographic abdominal findings of adult cattle probably also apply to calves. However, significant changes associated with ruminal growth and transition from a milk to a roughage diet occur in young calves during the first few months, and it can be expected that ultrasonographic features of organs adjacent to the rumen such as spleen and liver also undergo significant changes. These have not been investigated to date and therefore the goal of this study was to describe ultrasonographic findings of the spleen, liver, gallbladder, caudal vena cava and portal vein in six healthy calves from birth to 104 days of age. Standing calves were examined ultrasonographically six times at three-week intervals starting on the first or second day of life using a 5.0-MHz transducer and techniques described previously.

Results

The spleen was imaged on the left at the 5th to 12th intercostal spaces. The dorsal and ventral visible limits ran from cranioventral to caudodorsal because of superimposition of the lungs. The size of the spleen was largest at the 7th and 8th intercostal spaces and the maximum thickness was measured at the 9th to 12th intercostal spaces. The liver was seen in all calves on the right and could be imaged at the 5th to 12th intercostal spaces and the area caudal to the last rib. Similar to the spleen, the dorsal visible margin of the liver ran parallel to the ventral border of the lungs. The visible size of the liver was largest at the 8th to 11th intercostal spaces and the maximum thickness was measured at the 8th and 9th intercostal spaces. The parenchymal pattern consisted of numerous fine echoes homogeneously distributed over the entire organ. The gallbladder was most commonly seen at the 9th intercostal space and was circular, oval or pear-shaped on ultrasonograms. It extended beyond the ventral border of the liver depending on the amount of bile. The caudal vena cava was triangular in cross section but sometimes had a round or oval profile and was always seen in at least one intercostal space. The maximum circumference was measured at the 10th and 11th intercostal spaces. The portal vein was circular or oval in cross section and was characterised by stellate ramifications branching into the liver parenchyma. The portal vein could always be imaged at the 7th to 11th intercostal spaces and its mean diameter at the 9th to 11th intercostal spaces ranged from 1.2 cm to 1.8 cm.

Conclusions

The ultrasonographic findings of the spleen, liver, gallbladder, caudal vena cava and portal vein in six healthy Holstein-Friesian calves from birth to 104 days of age serve as reference values for the examination of these anatomical structures in diseased calves.     

Assessment of acid-base status and plasma lactate concentrations in arterial,mixed venous,and portal blood from dogs during experimental hepatic blood inflow occlusion

OBJECTIVE: To determine the effects of extended experimental hepatic blood flow occlusion (ie, portal triad clamping [PTC]) in dogs by measuring acid-base status and plasma lactate concentrations in arterial, mixed venous, and portal blood and evaluating the relationship between metabolic and concurrent hemodynamic changes. ANIMALS: 6 healthy Beagles. PROCEDURE: During anesthesia with isoflurane, cardiac output and arterial blood pressure were measured. Arterial, mixed venous, and portal blood samples were collected simultaneously for blood gas analyses and plasma lactate measurements before PTC and at 8-minute intervals thereafter. RESULTS: PTC resulted in severe hemodynamic and metabolic alterations. Eight minutes after PTC, significant decreases in cardiac index from a baseline value of 3.40 +/- 0.27 to 1.54 +/- 0.26 L/min/m2 and in mean arterial blood pressure from a baseline value of 74 +/- 6 to 43 +/- 6 mm Hg were recorded. After PTC, results indicative of lactic acidosis were found in portal blood at 16 minutes, in mixed venous at 32 minutes, and in arterial blood at 48 minutes. Significant differences in measured variables were also found between arterial and portal blood samples, between mixed venous and portal blood samples, and between arterial and mixed venous blood samples after PTC, compared with differences at baseline. CONCLUSIONS AND CLINICAL RELEVANCE: Analysis of mixed venous blood is preferable to analysis of arterial blood in the assessment of metabolic derangement. In a clinical setting, occluded portal blood is released to the systemic circulation, and the degree of reperfusion injury may depend on the metabolic status of pooled portal blood.     

The pathology of disseminated Aspergillus terreus infection in dogs

Disseminated Aspergillus terreus infection was diagnosed in ten previously healthy adult dogs--nine German shepherds and one dalmatian. The disease was characterized by the presence of multiple granulomas and infarcts in a wide range of organs. The kidney, spleen, and skeletal system were most commonly and severely affected. Fungal hyphae were demonstrated in large numbers within granulomas and thrombi, and A. terreus was readily isolated by culture. This disseminated mycosis appears unique; in this series of cases there was no apparent predisposing factor, portal of entry, or primary focus for dissemination of the infection.     

Acute and chronic gas bubble lesions in cetaceans stranded in the United Kingdom

The first evidence suggestive of in vivo gas bubble formation in cetacea, including eight animals stranded in the UK, has recently been reported. This article presents the pathologic findings from these eight UK-stranded cetaceans and two additional UK-stranded cetacean cases in detail. Hepatic gas-filled cavitary lesions (0.2-6.0 cm diameter) involving approximately 5-90% of the liver volume were found in four (two juvenile, two adult) Risso's dolphins (Grampus griseus), three (two adult, one juvenile) common dolphins (Delphinus delphis), an adult Blainville's beaked whale (Mesoplodon densirostris), and an adult harbour porpoise (Phocoena phocoena). Histopathologic examination of the seven dolphin cases with gross liver cavities revealed variable degrees of pericavitary fibrosis, microscopic, intrahepatic, spherical, nonstaining cavities (typically 50-750 microm in diameter) consistent with gas emboli within distended portal vessels and sinusoids and associated with hepatic tissue compression, hemorrhages, fibrin/organizing thrombi, and foci of acute hepato-cellular necrosis. Two common dolphins also had multiple and bilateral gross renal cavities (2.0-9.0 mm diameter) that, microscopically, were consistent with acute (n = 2) and chronic (n = 1) arterial gas emboli-induced renal infarcts. Microscopic, bubblelike cavities were also found in mesenteric lymph node (n = 4), adrenal (n = 2), spleen (n = 2), pulmonary associated lymph node (n = 1), posterior cervical lymph node (n = 1), and thyroid (n = 1). No bacterial organisms were isolated from five of six cavitated livers and one of one cavitated kidneys. The etiology and pathogenesis of these lesions are not known, although a decompression-related mechanism involving embolism of intestinal gas or de novo gas bubble (emboli) development derived from tissues supersaturated with nitrogen is suspected.     

Endotoxin Concentrations Measured by a Chromogenic Assay in Portal and Peripheral Venous Blood in Ten Dogs With Portosystemic Shunts

A chromogenic Limulus amebocyte lysate assay was used to measure portal and peripheral venous endotoxin concentrations in ten medically managed dogs undergoing surgery for correction of a single extrahepatic portosystemic shunt. In all dogs, both peripheral and portal venous blood samples were obtained at the time of surgical manipulation of the anomalous vessel. In six dogs, peripheral venous samples were obtained an average of 8.0 months after surgery. Five physically normal dogs without biochemical or histologic evidence of liver disease served as controls. Data analysis failed to demonstrate significant differences in peripheral and portal venous endotoxin concentrations between the control and study groups. Postoperatively five of six dogs showed a measurable reduction in peripheral venous endotoxin concentration over intraoperatively obtained values, but the differences were not statistically significant (P = 0.06). Based on results of this study it was concluded that systemic endotoxemia was not present in dogs with a single extrahepatic portosystemic shunt that were medically stable prior to surgery.     

CONTRAST AGENT Gd‐EOB‐DTPA (EOB·Primovist®) FOR LOW‐FIELD MAGNETIC RESONANCE IMAGING OF CANINE FOCAL LIVER LESIONS

Contrast‐enhanced magnetic resonance (MR) imaging with a new liver‐specific contrast agent gadolinium‐ethoxybenzyl‐diethylenetriamine penta‐acetic acid (Gd‐EOB‐DTPA; EOB·Primovist®) was studied in 14 normal beagles and 9 dogs with focal liver lesions. Gd‐EOB‐DTPA accumulates in normally functioning hepatocytes 20 min after injection. As with Gd‐DTPA, it is also possible to perform a dynamic multiphasic examination of the liver with Gd‐EOB‐DTPA, including an arterial phase and a portal venous phase. First, a reliable protocol was developed and the appropriate timings for the dynamic study and the parenchymal phase in normal dogs using Gd‐EOB‐DTPA were determined. Second, the patterns of these images were evaluated in patient dogs with hepatic masses. The optimal time of arterial imaging was from 15 s after injection, and the optimal time for portal venous imaging was from 40 s after injection. Meanwhile, the optimal time to observe changes during the hepatobiliary phase was from 20 min after injection. In patient dogs, 11 lesions were diagnosed as malignant tumors; all were hypointense to the surrounding normal liver parenchyma during the hepatobiliary phase. Even with a low‐field MR imaging unit, the sequences afforded images adequate to visualize the liver parenchyma and to detect tumors within an appropriate scan time. Contrast‐enhanced MR imaging with Gd‐EOB‐DTPA provides good demarcation on low‐field MR imaging for diagnosing canine focal liver lesions.     

Detection and Localization of Aleutian Disease Virus and its Antigens in vivo by Immunoferritin Technique

Tissues from mink infected with aleutian disease virus were examined by the electron microscope for the presence of virus particles. Virus-like particles, measuring 22 nm in diameter, were observed in macrophages of spleen, mesenteric lymph node and in Kupffer cells in liver of mink ten to 13 days after infection. The virus-like particles were usually present in vacuoles inside the cytoplasm of macrophages and Kupffer cells and, occasionally, similar particles were observed inside the nucleus. Cells from uninfected mink did not contain such patricles. To correlate the existence of these virus-like particles with the presence of aleutian disease virus antigen in infected cells, tissues were processed for immunoferritin technique. It was found that aleutian disease virus antigen was present in vacuoles inside the cytoplasm of cells from the infected spleen, lymph node and liver, and that the location was similar to that of the 22 nm virus-like particles. In addition, some viral antigen was also detected as cytoplasmic granular material. The nuclei of some cells also contained aleutian disease virus antigen. The pattern of aleutian disease virus antigen was similar to the distribution of virus-like particles in cells of infected tissue. It is suggested that virus replication occurs inside the nucleus with subsequent accumulation of virus in the vacuoles of the cytoplasm.     

Liver haemodynamics as they relate to portosystemic shunts in the dog: a review

There are several factors at play in the homeostatic regulation of hepatic blood flow. These include neovascularisation and other intrahepatic shunting of blood away from sinusoids and obstructed hepatic veins. Current surgical techniques used in the management of portosystemic shunts in the dog modify the flow of portal blood to the liver or of hepatic venous blood from the liver. Such modifications may have significant consequences in terms of long term liver perfusion. This review considers the haemodynamics within the normally perfused liver as well as those within the liver who’s blood supply has been modified.     

ULTRASONOGRAPHIC DIAGNOSIS OF PORTOSYSTEMIC SHUNTING IN DOGS AND CATS

The value of ultrasonography was evaluated in 85 dogs and 17 cats presented with a clinically suspected portosystemic shunt (PSS). A PSS was confirmed in 50 dogs and nine cats (single congenital extrahepatic in 42, single congenital intrahepatic in 11, and multiple acquired in six). Six dogs and one cat had hepatic microvascular dysplasia, and 29 dogs and seven cats had a normal portal system. Ultrasonography was 92% sensitive, 98% specific, and had positive and negative predictive values of 98% and 89%, respectively, in identifying PSS, with an overall accuracy of 95%. When a PSS was identified with ultrasonography, extrahepatic, intrahepatic, and multiple acquired PSS could be correctly differentiated in 53/54 patients (98%). The combination of a small liver, large kidneys, and uroliths had positive and negative predictive values of 100% and 51% for the presence of a congenital PSS in dogs. The portal vein/aorta (PV/Ao) and portal vein/caudal vena cava (PV/ CVC) ratios were smaller in animals with extrahepatic PSSs compared with animals with microvascular dysplasia, intrahepatic PSSs and those without portal venous anomalies (P<0.001). All dogs and cats with a PV/Ao ratio of < or = 0.65 had an extrahepatic PSS or idiopathic noncirrhotic portal hypertension. Dogs and cats with PV/Ao and PV/CVC ratios of > or = 0.8 and > or = 0.75, respectively, did not have an extrahepatic PSS. Reduced or reversed portal flow was seen in four of four patients with multiple acquired PSSs secondary to portal hypertension. The presence of turbulence in the caudal vena cava of dogs had positive and negative predictive values of 91% and 84%, respectively, for the presence of any PSS terminating into that vein.     

家兔亚硒酸中毒的病理形态学研究

给家兔分别肌肉注射不同剂量的亚硒酸钠，历时入周，复制出亚急性硒中毒的动物模型。病理形态学变化为：家兔的生长受到明显抑制，肝，肾，心，脾等组织器官损害严重如肝实质细胞变性，坏死；肾实质退行病变；心肌纤维变性，充血，肺淤血，水肿：脾萎缩，淋巴细胞坏死，肝，肾，心细胞内线粒高度肿胀，嵴减少，断裂或消失成空泡。     

Statistical relevance of ultrasonographic criteria in the assessment of diffuse liver disease in dogs and cats

OBJECTIVE: To determine whether objectively applied ultrasonographic interpretive criteria are statistically useful in differentiating among 7 defined categories of diffuse liver disease in dogs and cats. SAMPLE POPULATION: Ultrasonographic images of 229 dogs and 104 cats. PROCEDURES: Liver parenchymal or related sonographic criteria established by the authors were retrospectively and independently applied by 3 radiologists who were not aware of patient status or patient laboratory data. Seven histologic or cytologic categories of diffuse (infiltrative but not nodular) liver diseases were jointly established by the authors and included normal liver; inflammation; round-cell neoplasia; non-round-cell infiltrative, prenodular (early) metastatic neoplasia; lipidosis; vacuolar hepatopathy; and other. Liver parenchymal sonographic criteria included parenchymal sound attenuation with increasing depth, comparative organ echogenicity (liver, spleen, and kidneys), diffuse or patchy hyperechoic or hypoechoic echotexture, uniform or coarse echotexture, portal venous clarity, and liver lobe geometry. Related extrahepatic criteria included gallbladder wall thickness, bile duct diameter, amount and character of gallbladder precipitate, nondependent shadowing in the gallbladder, hepatic vein diameter versus caudal vena cava diameter, peritoneal fluid, spleen echotexture (normal vs abnormal [characterized]), and kidney echotexture. Ultrasonographic criteria were statistically compared to the 7 categories of diffuse liver disease in search of clinically exploitable relationships. RESULTS: Statistical evaluation of the applied ultrasonographic criteria did not yield clinically acceptable accuracy for discrimination among the 7 categories of diffuse liver diseases (including normal liver) in either species. CONCLUSIONS AND CLINICAL RELEVANCE: Criterion-based ultrasonographic appearance was insufficient to discriminate among canine and feline diffuse infiltrative liver diseases.     

Idiopathic noncirrhotic portal hypertension in dogs: 33 cases (1982-1998)

OBJECTIVE: To describe clinical signs, diagnostic findings, and outcome in dogs with idiopathic intrahepatic portal hypertension. DESIGN: Retrospective study. ANIMALS: 33 dogs. PROCEDURE: Medical records of dogs with portal hypertension of intra-abdominal origin were reviewed. Dogs with intra-abdominal portal hypertension of vascular causes or with hepatic histopathologic changes consistent with severe diffuse hepatobiliary disease were excluded. History and results of physical examination, clinicopathologic tests, diagnostic imaging studies, histologic examination, and treatment were summarized. Outcome was determined in 26 dogs. RESULTS: Dogs were referred most often because of ascites, intermittent vomiting or diarrhea, and polydipsia of several months' duration. Microcytosis, high serum alkaline phosphatase and alanine transaminase activities, hepatic dysfunction, urine specific gravity < or = 1.021, and abdominal transudate were the predominant clinicopathologic features. Microhepatia, abdominal effusion, and multiple anomalous venous anastomoses were the major findings of diagnostic imaging. Hepatic histopathologic changes were consistent with idiopathic noncirrhotic portal hypertension and were indistinguishable from those of dogs with surgically created portocaval anastomosis. Outcome was determined for 19 dogs released from hospital; 13 dogs remained healthy with mostly palliative treatment for periods of 5 months to 9 years. CONCLUSIONS AND CLINICAL RELEVANCE: The clinical signs, clinicopathologic test results, portal pressure, and gross appearance of the liver of dogs with idiopathic noncirrhotic portal hypertension may be identical to those of dogs with cirrhosis; therefore liver biopsy is crucial. Because the prognosis for idiopathic noncirrhotic portal hypertension is generally favorable, owners of affected dogs should be discouraged from choosing euthanasia.