Both the production and absorption of CNS toxins are inhibited with various types of medications. Medical therapy is directed toward stabilizing the animal with neurological deficits prior to any surgical intervention. This can be confirmed by an exploratory laparotomy, mesenteric portography, or possibly ultrasonography. Confirmation of this disease is by the negative findings of a single extrahepatic or intrahepatic shunt during surgery and the results of a liver biopsy.Īnother differential diagnosis should include acquired shunts secondary to primary liver disease. This is consistent with a disease called hepatic microvascular dysplasia. However, the biochemical changes are mild (BUN, albumin, hematocrit levels are usually normal) and the serum bile acids are mildly elevated. Occasionally, dogs will present with mild signs of liver disease that would be consistent with a PSS. It cannot, however, differentiate single from multiple shunts or intrahepatic from extrahepatic shunts. In referral institutions, rectal portoscintigraphy is used as a screening test for PSS and can predict the approximate percentage of blood being shunted away from the liver. Finding the shunt vessel is very difficult and highly dependent on the skill of the sonographer. Ultrasonography will demonstrate a small liver, confirm renal and/or cystic uroliths, and may reveal a shunt vessel. Serum bile acids are elevated (resting and postprandial).Ībdominal radiography will show microhepatica, occasionally renomegaly, and possibly uroliths. Biochemical tests usually reveal a low blood urea nitrogen (BUN), hypoalbuminemia, hypoglycemia, and occasionally increased liver enzymes. Neurological signs may be noticeable during the physical examination.Ī complete blood count (CBC) usually demonstrates an anemia (microcytic, normochromic). Other anomalies that may coexist with PSS include cryptorchidism and a heart murmur. Physical examination findings usually include a small body size, nonpalpable liver, and prominent kidneys. Urolithiasis is seen in about 30% of dogs with PSS. On some occasions, urinary signs may be the only reason for owner's seeking veterinary care. Urinary tract signs include pollakiuria, polydypsia, polyuria, stranguria, and occasionally urolithiasis. Animals are often presented underweight and have a history of intermittent diarrhea, vomiting, and nonspecific gastrointestinal signs. The second most common signs are related to the gastrointestinal system. The CNS signs are usually intermittent and progressive in nature. The severity of CNS signs varies and are often worse after eating especially if it is a protein-rich meal. Signs in dogs with PSS usually include some neurological deficits (temporary blindness, ataxia, head pressing, circling, depression, lethargy, and seizures). It is not uncommon to see dogs with a single extrahepatic shunt present as young adults. Most animals show signs within the first 6 months of life. HE develops from toxins entering the systemic circulation that are normally filtered or metabolized by the liver. This decreases hepatic function and the development of neurological signs due to hepatoencephalopathy (HE). The diversion of blood away from the liver results in its underdevelopment. The most common breeds affected are the Yorkshire terrier, Miniature Schnauzers and other toy breeds. Purebred dogs are at higher risk for portosystemic shunts. Extrahepatic shunts are anomalous vessels that leave the portal system before it enters the liver and communicates with the vena cava or another systemic vessel. Dogs with intrahepatic shunts are usually presented at an earlier age than dogs with extrahepatic shunts because of the greater volume of splanchnic blood bypassing the liver. Intrahepatic shunts are most commonly seen in the large breed dogs. PSS is either intrahepatic or extrahepatic in location. Persistent patent ductus venosus, portacaval, gastrocaval, portoazygos and portomesenteric shunts are the more common ones. There are several anomalous connections between the portal system and the systemic circulation (PSS). Books & VINcyclopedia of Diseases (Formerly Associate).
VINcyclopedia of Diseases (Formerly Associate).
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