Liver transplantation in rats using small-for-size grafts: a study of hemodynamic and morphological changes.
BACKGROUND
Damage to a small-for-size liver graft after reperfusion is frequently observed but the mechanism of injury remains unclear.


OBJECTIVE
Injury to a small-for-size liver graft is related to the changes of portal pressure and blood flow.


METHODS
Survival rates, portal hemodynamics, microcirculatory changes, and morphological changes (by light microscopy and electron microscopy).


METHODS
A rat model of nonarterialized orthotopic liver transplantation comparing 2 groups of rats transplanted with whole grafts (100% of recipient liver weight) and small-for-size grafts (30% of recipient liver weight).


RESULTS
Median survival of the rats with small-for-size grafts was 30 hours (range, 27-37 hours). During the first 15 minutes after reperfusion, mean arterial pressure of the small-for-size graft group was significantly lower than that of the whole graft group (10-minute: 100 vs 132 mm Hg, P =.04; 15-minute: 96 vs 127 mm Hg, P =.04). Portal pressure (in centimeters of water) of the small-for-size graft group was significantly higher in the first 20 minutes after reperfusion than the level before the anhepatic phase (5-minute: 15.1 vs 9.3, P =.02; 10-minute: 16.1 vs 9.3, P =.03; 15-minute, 13.5 vs 9.3, P =.03; 20-minute: 13.4 vs 9.3, P =.03) and was significantly higher than that of the whole graft group in the first 10 minutes after reperfusion (5-minute: 15.1 vs 9.6, P =.02; 10-minute: 16.1 vs 10.3, P =.04). Hepatic microcirculatory blood flow (in milliliters per minute per 100 g) was also significantly higher in the small-for-size graft group during the first 40 minutes after reperfusion (5-minute: 16.3 vs 9.3, P =.02; 10-minute: 14.9 vs 6.6, P =.02; 15-minute: 14.8 vs 5.5, P =.02; 20-minute: 13.1 vs 7.0, P =.02; 30-minute: 13.2 vs 8.8, P =.04; 40-minute: 14.6 vs 7.1, P =.02). Light and electron microscopy showed normal morphological features of whole graft up to 24 hours after reperfusion. The small-for-size graft, however, showed sinusoidal congestion, tremendous swelling of mitochondria of hepatocytes, irregular large gap of sinusoidal lining cells, and collapse of the space of Disse.


CONCLUSIONS
In a rat model, the portal hemodynamic changes in small-for-size grafts are transient. Progressive damage of the graft may result from microcirculatory failure due to irreversible endothelial injury after reperfusion.
Man
K
K
Department of Surgery, The University of Hong Kong Medical Centre, Queen Mary Hospital, 102 Pokfulam Rd, Hong Kong, China.
Lo
C M
CM
Ng
I O
IO
Wong
Y C
YC
Qin
L F
LF
Fan
S T
ST
Wong
J
J
D000818:Animals; D004730:Endothelium, Vascular / Q000473:pathology; D008099:Liver / Q000098:blood supply* / Q000473:pathology; D016031:Liver Transplantation / Q000473:pathology*; D008930:Mitochondria, Liver / Q000473:pathology; D009929:Organ Size / Q000502:physiology; D017082:Portal Pressure / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012039:Regional Blood Flow / Q000502:physiology; D015427:Reperfusion Injury / Q000473:pathology*