Symptomatic portal system thrombosis in soldiers due to extended stay at extreme altitude

Background: With induction of Indian Army to heights over 5000 m above mean sealevel (MSL), several new complications of long-term stay at extreme altitude have come to light. The authors' experience with soldiers who developed symptomatic portal system thrombosis (SPST) is described here. Methods: Clinical data were prospectively collected between April 1998 and April 2003, on all patients hospitalized for SPST from high-altitude areas (HAA, > 3000 m above MSL) and those from non-high-altitude areas (NHAA). Site of thrombosis was confirmed by imaging and included splenic, portal, superior mesenteric, or inferior mesenteric vein thrombosis. Patients were investigated to rule out known predisposing factors and prothrombotic conditions. Results: A total of 37 cases of SPST were seen during the study period, of which 26 were from HAA. Mean age of cases from HAA was 27 +/- 4.6 years and all were male. Mean stay at high altitude was 11.7 +/- 6.2 months. First symptom was pain in abdomen in almost all the cases, later followed by gastrointestinal bleeding and fever in 14 each, and vomiting in 19. Clinical examination showed ascites (81%), splenomegaly (76.9%), and hepatomegaly (69.2%). Diagnosis was made by imaging scans (23 cases) and on surgery in three cases. A known prothrombotic state was detected in five cases from HAA and in eight cases from NHAA (P <= 0.01). Ultrasound Doppler scan picked up collaterals as early as 12-45 days after onset of symptoms. Conclusions: Extended stay at HAA may be a risk factor for development of symptomatic portal system thrombosis. (C) 2005 Blackwell Publishing Asia Pty Ltd.