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Biomedical subjects

R G McWilliams

Publications and source records attributed to R G McWilliams.

At least 19 recordsLinked to original sources
PubMed2004

Late complications after ligation and bypass for popliteal aneurysm.

BACKGROUND: Ligation and bypass is standard treatment for popliteal aneurysm. This technique does not abolish collateral circulation to the aneurysm, which may continue to expand and/or rupture. This study assessed whether complete thrombosis of the aneurysm sac occurs after operation and examined the long-term clinical outcome. METHODS: The records of all patients who underwent popliteal aneurysm repair in a university hospital over 10 years were reviewed. Patients who had undergone ligation and bypass were recalled for clinical and ultrasonographic examination to determine the fate of the aneurysm sac. RESULTS: Persistent blood flow in the aneurysm sac was present in 12 of 36 legs a median of 48 months after operation. This was associated with symptomatic enlargement of the aneurysm in six patients. The incidence of sac enlargement was lower in bypassed aneurysms with no intrasac flow on duplex examination. CONCLUSION: Ligation and bypass does not always abolish blood flow in the sac of a popliteal aneurysm. It may be associated with continued expansion and late complications.

Aged↗
PubMed2003

Aortic side branch perfusion alone does not account for high intra-sac pressure after endovascular repair (EVAR) in the absence of graft-related endoleak.

OBJECTIVE: to examine the effect of stent-graft deployment on pressure within an aneurysm sac and to investigate the potential sources of intra-sac pressure. MATERIAL AND METHODS: intra-sac pressure was monitored during and immediately after endovascular repair via an indwelling catheter. Intra-sac pressure was also monitored during conventional open repair and was compared with the pressure measured within patent lumbar and inferior mesenteric side-branches, both before and after restoration of iliac arterial blood flow. Intra-sac and side-branch pressures were recorded and expressed as ratios of simultaneously measured radial artery pressure. RESULTS: in the absence of a graft-related endoleak (23/25 patients), endovascular repair resulted in a significant reduction in intra-sac pulse pressure (median ratio 0.31 IQR 0.10-0.46). There was no corresponding reduction in mean intra-sac pressure (median ratio 0.91; IQR 0.83-1.00). Application of clamps at conventional open repair resulted in a fall in both intra-sac pressure (median ratio 0.39, IQR 0.32-0.64) and pressure within side-branches (median ratio 0.45, IQR 0.33-0.64). Restoration of iliac blood flow resulted in a modest recovery of the side-branch pressure (median ratio 0.63, IQR 0.57-0.81), which nonetheless remained significantly less than the intra-sac pressure recorded after EVAR (p=0.01). CONCLUSION: reperfusion of the aneurysm sac through patent side-branches seems insufficient to account for persistent pressurisation of the aneurysm after endovascular repair. This finding supports the hypothesis that pressure may be transmitted directly through stent-graft fabric.

Aortic Aneurysm↗
PubMed2002

The role of gadolinium-enhanced MR imaging in the preoperative evaluation of inflammatory abdominal aortic aneurysm.

Inflammatory abdominal aortic aneurysm is an uncommon variant of abdominal aortic aneurysms. Thorough preoperative imaging of the extent of the aneurysm and inflammation and the associated complications are crucial in the management of this condition. We report a case of inflammatory abdominal aortic aneurysm where, after the initial contrast-enhanced CT, gadolinium-enhanced MR imaging was used to define the true extent of the inflammation and differentiate inflammation from mural thrombus at the iliac extension of the aneurysm. The imaging appearances are presented and the impact of MR imaging on further surgical management options including endovascular repair are discussed.

Aortic Aneurysm, Abdominal↗
PubMed2002

Complications following endovascular abdominal aortic aneurysm repair.

There is a growing population of patients who have undergone endovascular abdominal aortic aneurysm repair (EVAR) and thus there is an increasing likelihood that radiologists who are unfamiliar with this technique and its complications will have to report radiological investigations on one of these patients. The purpose of this review is to describe and illustrate the normal and abnormal radiological appearances after EVAR on plain radiography, ultrasound and CT.

Aorta, Abdominal↗
PubMed2001

Perianeurysmal fibrosis: a relative contra-indication to endovascular repair.

OBJECTIVE: Perianeurysmal fibrosis (PAF) with involvement of neighbouring viscera can render open repair of inflammatory aneurysms technically difficult and therefore hazardous. For this reason, endovascular repair (EVAR) has been advocated as the preferred approach for this condition. EVAR is known to induce a systemic inflammatory response in patients but the nature of the local response remains unknown. If significant, such a response could exacerbate rather than ameliorate PAF. The aim of the study was to examine the incidence, course and consequences of perianeurysmal fibrosis detected by computerised tomography (CT) before and after EVAR. MATERIAL AND METHODS: The clinical records of patients treated by EVAR and followed for at least 6 months were reviewed. Pre and post-operative CT images were independently graded for PAF by three radiologists according to a standard protocol. RESULTS: PAF was documented preoperatively in six out of a total of 61 patients. In two of these PAF worsened after EVAR resulting in ureteric obstruction and hydronephrosis requiring ureteric stents. In the remaining 4 patients PAF did not reduce postoperatively. PAF of low grade developed postoperatively in 10 out of 55 patients (18%) in whom there was no evidence of PAF on preoperative imaging. Median follow-up was 18 months (range 6-36 months). The development of periaortic fibrosis de novopostoperatively was statistically significant (McNemar's test p=0.002). CONCLUSION: EVAR does not seem to reverse PAF if this is present preoperatively and it induces this condition in approximately one sixth of patients without evidence of preoperative PAF. The potential for this adverse inflammatory local response should be taken into account when considering EVAR for treatment of aneurysms with perianeurysmal fibrosis and must be weighed against the perceived benefits of this approach.

Aged↗
PubMed2000

Doppler ultrasound diagnosis of a superficial ulnar artery.

The ulnar artery may lie in a superficial position in the forearm as a normal anatomical variant. We report a case where this variant was clinically mistaken for phlebitis but was diagnosed correctly with Doppler ultrasound. In this report, we discuss the anatomy and clinical relevance of the superficial ulnar artery.

Adult↗
PubMed2000

Freedom from endoleak after endovascular aneurysm repair does not equal treatment success.

OBJECTIVE: To determine whether freedom from endoleak after endovascular repair of abdominal aortic aneurysm (EVAR) is a reliable guide to freedom from persistent or recurrent pressurisation of the aneurysm sac (endotension) and therefore freedom from risk of rupture. PATIENTS AND METHODS: The records of 55 patients followed for more than 3 months after EVAR were reviewed to correlate the presence or absence of endoleak on contrast-enhanced CT and/or angiography with changes in maximum aneurysm diameter (DMAX). RESULTS: in 22 (40%) patients there was no significant change in DMAX during follow-up. In 21 of these no endoleak was observed on CT or angiography. One patient developed a secondary side-branch endoleak which remains under observation. In 18 (33%) patients, DMAX decreased during follow-up. Thirteen of these remained free of endoleak. Four patients developed secondary endoleaks which were treated by secondary intervention. One patient with persistent primary endoleak suffered fatal aneurysm rupture three days before planned intervention. DMAX increased in 15 (27%) patients. In only five of these could an endoleak be identified on CT and/or angiography. One primary side-branch endoleak persists following failed embolisation. Four secondary endoleaks have been corrected by secondary intervention. Four of the remaining 10 patients died suddenly from unknown cause. All had DMAX greater than 65 mm at last follow-up. One patient underwent late conversion, which suggested continued pressurisation through thrombus at the site of a "sealed" primary proximal endoleak. Two patients are scheduled to undergo embolisation of patent side-branches revealed only by Levovist enhanced Duplex scanning and three patients remain under observation. CONCLUSION: Freedom from endoleak on conventional imaging incorrectly suggested freedom from endotension in 10 (18%) of our patients. Follow-up after endovascular repair must include regular measurement of DMAX and/or aneurysm sac volume to identify those patients who remain at risk of rupture.

Aged↗
PubMed1999

Use of contrast-enhanced ultrasound in follow-up after endovascular aortic aneurysm repair.

PURPOSE: To investigate the use of contrast-enhanced ultrasound in the detection of endoleak after endovascular repair of abdominal aortic aneurysm. MATERIALS AND METHODS: Eighteen patients underwent follow-up on 20 occasions after endovascular aortic aneurysm repair by arterial-phase contrast-enhanced spiral computed tomography (CT). All patients had unenhanced color Doppler ultrasound and Levovist-enhanced ultrasound on the same day. The ultrasound examinations were reported in a manner that was blind to the CT results. CT was regarded as the gold standard for the purposes of the study. RESULTS: There were three endoleaks shown by CT. Unenhanced ultrasound detected only one endoleak (sensitivity, 33%). Levovist-enhanced ultrasound detected all three endoleaks (sensitivity, 100%). Levovist-enhanced ultrasound indicated an additional six endoleaks that were not confirmed by CT (specificity, 67%; positive predictive value, 33%). In one of these six cases, the aneurysm increased in size, which indicates a likelihood of endoleak. Two of the remaining false-positive results occurred in patients known to have a distal implantation leak at completion angiography. CONCLUSION: In this small group of patients, contrast-enhanced ultrasound appears to be a reliable screening test for endoleak. The false-positive results with enhanced ultrasound may be due to the failure of CT to detect slow flow collateral pathways. Although the number of patients in this study is small, enhanced ultrasound may be more reliable than CT in detecting endoleak.

Aged↗
PubMed1998

Sources of error in intra-arterial pressure measurements across a stenosis.

OBJECTIVE: To investigate potential errors associated with different techniques of intra-arterial pressure measurement at angiography. MATERIALS AND METHODS: An experimental model of an arterial stenosis was developed. Experiments were performed to assess the relevance of catheter position, catheter direction and catheter type on the recorded intraluminal pressure. Transstenotic pressure gradients were recorded with and without angiographic catheters crossing the stenosis. RESULTS: At physiological flow rates angiographic catheter type does not influence the recorded pressure. At high flow rates through tight stenoses there is a significant catheter-related difference in recorded pressure adjacent to a stenosis. Downstream pressures may be altered by up to 85 mmHg when standard angiographic catheters are placed across a stenosis. CONCLUSION: The different techniques employed to measure pressure differences across a model stenosis may introduce significant errors up to 85 mmHg. Care must be taken when pressure measurements alone are used to interpret the clinical significance of a stenosis. In low flow conditions there may not be a detectable pressure gradient across a 95% stenosis.

Angiography↗
PubMed1997

Pseudolipoma of inverted Meckel's diverticulum: clinical, radiological and pathological correlation.

Three cases of isolated inverted Meckel's diverticulum are described. In two cases an initial pathological diagnosis of small bowel lipoma was suggested. In a third case central fat was demonstrated on CT and peristalsis of the intraluminal polypoid mass was observed during US examination. In all three cases small bowel enema examination demonstrated the lesion. Correlation of the clinical, radiological and pathological features is emphasised, as this will allow the correct diagnosis.

Adult↗
PubMed1996

Case report: The "veiled right kidney sign"--an ultrasound finding in retroperitoneal perforation of the duodenum.

We report a case of traumatic duodenal perforation where the diagnosis was first considered during abdominal ultrasound examination. A subsequent CT scan identified the site of perforation which was confirmed at laparotomy. This condition typically produces few clinical signs or symptoms initially but has a high mortality related to delayed diagnosis. The ultrasound findings that prompted early diagnosis are described.

Adult↗