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The Quarterly Journal of Nuclear Medicine 1999 March;43(1):83-92


language: English

The role of radiolabeled leukocyte imaging in the management of patients with acute appendicitis

Kipper S. L.

From the Nuclear Medicine Department of Imaging Tri-City Medical Center, Oceanside, California, USA


Acute appen­di­citis is a clin­i­cal­ly chal­leng­ing sur­gi­cal dis­ease par­tic­u­lar­ly dif­fi­cult to diag­no­sis in wom­en and chil­dren. An atyp­i­cal pres­en­ta­tion of ­acute appen­di­citis is a ­major fac­tor lead­ing to ­delay in diag­no­sis and unnec­es­sary sur­gery. Delay in diag­no­sis is asso­ciat­ed ­with mor­bid­ity ­from per­fo­ra­tion, ­abscess and pro­longed hos­pi­tal­iza­tion. The rou­tine use of adjunc­tive imag­ing stud­ies has not ­improved the diag­nos­tic accu­ra­cy for ­acute appen­di­citis nor has impact­ed clin­i­cal out­come. 99mTc ­HMPAO-­labeled leu­ko­cyte imag­ing is one diag­nos­tic imag­ing ­test ­that has the poten­tial of alter­ing the clin­i­cal man­age­ment of ­acute appen­di­citis. 99mTc ­HMPAO-­labeled leu­ko­cyte imag­ing is high­ly sen­si­tive for detect­ing ­even ­small inflam­ma­to­ry pro­cess­es in the abdo­men ­because of ­high tar­get to back­ground and ear­ly rap­id ­uptake at ­sites of inflam­ma­tion. We stud­ied the use of 99mTc ­HMPAO-­labeled leu­ko­cytes for diag­no­sis and man­age­ment of sus­pect­ed ­acute appen­di­citis in 124 ­patients ­with an atyp­i­cal clin­i­cal pres­en­ta­tion. Emergent imag­ing was per­formed imme­di­ate­ly fol­low­ing injec­tion of ­labeled leu­ko­cytes and con­tin­ued ­until pos­i­tive or ­through 2 ­hours if neg­a­tive. The ­scan cor­rect­ly and rap­id­ly detect­ed ­acute appen­di­citis in 50 of 51 ­patients ­with sur­gi­cal con­fir­ma­tion for a sen­si­tiv­ity of 98%. The spec­i­fic­ity was 82% lead­ing to an over­all accu­ra­cy of 90%. The ­high neg­a­tive pre­dict­ed val­ue of 98% ­allowed ear­ly dis­charge ­from the emer­gen­cy depart­ment and avoid­ed cost­ly obser­va­tion in the hos­pi­tal and poten­tial­ly unnec­es­sary sur­gery in ­these ­patients ­with neg­a­tive ­scans. The neg­a­tive explor­a­to­ry lap­a­rot­o­my ­rate was 4% in ­this ­patient pop­u­la­tion com­pared to 9% in a sim­i­lar pop­u­la­tion of ­patients who ­were not ­scanned. These ­data ­have ­been con­firmed now in ­over 600 ­patients scan­ned in our depart­ment. The ­main draw­backs of 99mTc ­HMPAO-­labeled leu­ko­cyte imag­ing are the require­ment of ­blood han­dling and a ­delay in diag­no­sis ­because of the 2-hours prep­ar­a­tion ­time ­prior to imag­ing. There are new radio­phar­ma­ceu­ti­cals on the hori­zon ­which ­have the poten­tial of replac­ing 99mTc ­HMPAO-­labeled leu­ko­cyte imag­ing and ­offer advan­tag­es of a short­er prep­ar­a­tion ­time and no ­blood han­dling. These ­include 99mTc ­labeled mono­clo­nal anti­bod­ies and chem­o­tac­tic pep­tides. The 99mTc ­anti-­SSEA-1 IgM anti­body (LeuTech) is cur­rent­ly ­under inves­ti­ga­tion for use in ­acute appen­di­citis. In sum­mary, nuclear medicine can ­play a key ­role in the diag­no­sis of ­acute appen­di­citis in ­patients ­with an atyp­i­cal pres­en­ta­tion. This tech­nique is ­cost effec­tive and ­appears to ­impact favor­ably on clin­i­cal out­come.

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