Colonic ischaemia (CI), Intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) are devastating complications after abdominal aortic aneurysm (AAA) surgery. The aims of this thesis were to study the incidence and clinical consequences of IAH/ACS and the association between CI and intra-abdominal pressure (IAP) among patients undergoing OR for ruptured AAA (rAAA), to compare extraluminal pHi monitoring, with standard intra-luminal monitoring among patients operated on for AAA, and to study the frequency and clinical consequences of IAH/ACS after endovascular repair (EVAR) for rAAA. The incidence of ACS was 26% in a retrospective study of 27 patients undergoing OR for rAAA. Consensus definitions on IAH/ACS were appropriate for patients after OR for rAAA: 78% (7/9) of patients with IAH grade III or IV developed organ failure and all patients who developed CI had some degree of IAH. Active fluid resuscitation treating hypovolaemia to avoid CI may partly cause IAH. The association between CI and IAP was investigated in a prospective study on 29 patients operated on for rAAA, 86% (25/29) were treated for hypovolaemia and ten (34%) had both IAH and CI. Since monitoring colonic perfusion is very important and there is no ideal method, a new technique, extraluminal colonic tonometry to detect colonic perfusion was compared with standard intraluminal tonometry. Although, this new method was not able to determine the severity of ischaemia it may serve as a screening test. EVAR of rAAA is feasible and patients may benefit from this less invasive procedure. Of 29 patients treated with this technique, 10% developed ACS, and all patients except one with preoperative shock developed some degree of IAH. In conclusion, IAP/ACS is common after both OR and EVAR for rAAA, and is associated with adverse outcome. Monitoring IAP and colonic perfusion with timely intervention may improve outcome.