COMPARISON OF PER‐RECTAL PORTAL SCINTIGRAPHY USING ^99mTECHNETIUM PERTECHNETATE TO MESENTERIC INJECTION OF RADIOACTIVE MICROSPHERES FOR QUANTIFICATION OF PORTOSYSTEMIC SHUNTS IN AN EXPERIMENTAL DOG MODEL

Abstract

Per‐rectal portal scintigraphy using tech‐netium‐99m pertechnetate (99mTcO4‐) was performed in 8 normal dogs before and after surgical creation of a portacaval shunt. Shunt fractions were calculated by computer assisted analysis of dynamic images (IMG) and compared to shunt fractions determined by mesenteric venous injection of radioactive microspheres (MIC). The mean pre‐operative shunt fraction was 1.59% using IMG and 3.00% using MCI. The mean postoperative shunt fraction was 64.56% using IMG and 69.56% using MIC. There was excellent correlation between both methods (r2 0.94). Per‐rectal portal scintigraphy is an easily performed, inexpensive method to diagnose and quantify portosystemic shunts in dogs.

Evaluation of interoperator variance in shunt fraction calculation after transcolonic scintigraphy for diagnosis of portosystemic shunts in dogs and cats

“…When administered rectally, approximately 14% of the administered dose is rapidly absorbed through the colonic mucosa and into the portal vasculature. Daniel et al 9 found good correlation between scintigraphy fraction values obtained via rectal administration of Na 99m TcO 4 and values obtained via injection of radiolabeled microspheres into mesenteric veins. Shunting is diagnosed if radiopharmaceutical activity is identified in the heart prior to the liver or if simultaneous activity in both organs is detected.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] The current imaging agent of choice for portoscintigraphy is sodium pertechnetate Tc 99m (Na 99m TcO 4 ). Several radiopharmaceuticals and methods of administration have been investigated.…”

“…1,9 Because Na 99m TcO 4 is neither extracted nor bound to the tissues it perfuses, a nuclear portogram results. 9 In comparing scintigraphy via rectal administration of Na 99m TcO 4 versus rectal administration of iodoamphetamine I 123 (IMP), Koblik et al 7 determined that Na 99m TcO 4 overestimated shunt fraction values, particularly in large shunts. When radiopharmaceutical activity is detected in the liver a minimum of 2 seconds before it is detected in the heart, shunting is ruled out.…”

Per Rectal Portal Scintigraphy Using 99mTechnetium Pertechnetate to Diagnose Portosystemic Shunts in Dogs and Cats

“…Shunt fractions calculated by this method have been verified by microsphere techniques in dogs with surgically created PSS. 22 All the animals with PSS had shunt fraction values that were easily distinguished from the control dog values. The cat with a gastrosplenic-caval shunt had the lowest shunt fraction value, as expected, since portal blood from the colon does not normally pass through 27 this vessel.…”

“…The severity of the shunt can be determined by quantifying the activity in the liver and heart during the first passage of the radiopharmaceutica1. 20,22 The purpose of this study was to determine whether per rectal portal scintigraphy using 99mT~04-could be used to diagnose a portosystemic shunt in dogs and cats. Teaching Hospital (UTVTH) for possible portosystemic shunts between April 1988 and July 1989.…”