USE OF TRANSCOLONIC ¹²³I‐IODOAMPHETAMINE TO DIAGNOSE SPONTANEOUS PORTOSYSTEMIC SHUNTS IN 18 DOGS

Abstract

Transcolonic 123I‐Iodoamphetamine is rapidly absorbed across the colonic mucosa and binds to amine receptors in the liver and lungs. During the first ten minutes following colonic administration, a simple ratio of lung counts to lung counts plus liver counts provides an accurate estimate of the fraction of portal blood that bypasses hepatic sinusoids in dogs with portosystemic shunts. Studies were performed on 24 dogs with suspect portosystemic shunt. Shunt fraction values for 18 dogs with surgically confirmed portosystemic shunt were obviously higher than published values for normal dogs, and also significantly higher than values for the other six dogs, later confirmed to lack shunts. Postoperative studies were repeated on ten dogs with single shunt vessels 1–2 days after shunt closure. Total shunt ligation resulted in normal postoperative shunt fraction, whereas partial shunt ligation resulted in persistant elevation of shunt fraction. Transcolonic iodoamphetamine scintigraphy is noninvasive, easy to perform, and provides an accurate method to diagnose dogs with portosystemic shunt.

Dynamic computed tomographic quantitation of hepatic perfusion in dogs with and without portal vascular anomalies

“…The perfusion variables calculated in our study by use of dynamic CT agreed well with values report-ed in the literature, 1,6,11,13,[16][17][18][19] which lends credence to its use in determining perfusion noninvasively. Further studies are required to validate the repeatability of hepatic perfusion in a single dog, as portal perfusion can vary after feeding and with different composition of diets.…”

“…7 One of the more common hemodynamic methods used to diagnose and monitor dogs with portosystemic shunts is the shunt fraction. 17 This scintigraphic technique quantifies the fraction of blood that bypasses the liver through a portosystemic shunt and has been shown to be correlated with outcome of surgery to correct the shunt. 18,19 Limitations to the shunt fraction exist such as inaccuracy, 19,20 and the shunt fraction does not measure perfusion of the liver directly.…”

Association between hepatic histopathologic lesions and clinical findings in dogs undergoing surgical attenuation of a congenital portosystemic shunt: 38 cases (2000–2004)

“…This variation may partly reflect differences in the shunt fraction (ie, the proportion of total portal blood flow that passes through the shunt). Variable preoperative shunt fraction in dogs with a CPSS has been observed fluoroscopically 15 and when rectal scintigraphy is used, [30][31][32] but preoperative shunt fraction consistently exceeds 90% when portal scintigraphy is used. 33,34 Any true differences in shunt fraction would presumably de-pend on the number and caliber of the intrahepatic portal vessels as well as the caliber of the shunting vessel itself.…”

Progressive remission of portosystemic shunting in 23 dogs after partial closure of congenital portosystemic shunts

“…Transcolonic portal scintigraphy has often been used for the diagnosis and assessment of portosystemic shunts in dogs (Koblik and others 1989, Daniel and others 1990, 1991, Lawrence and others 1992, van Vechten and others 1994, Koblik and Hornof 1995, Vogt and others 1996). However, this procedure has several disadvantages; it needs large quantities of radiopharmaceutical, there are difficulties in determining the optimum time for imaging (leading to high shunt fractions in healthy dogs), it is inaccurate with large and small shunts (van Vechten and others 1994), and it has a low sensitivity in detecting shunts (Lawrence and others 1992).…”