Handheld Doppler for measurement of systolic pressure for ABPI
When Doppler tests indicate arterial insufficiency, arterial Duplex ultrasonography will (noninvasively) provide accurate anatomic and hemodynamic information on the site and extent of the arterial disease. When indicated, further detailed anatomic information for treatment planning can be obtained from magnetic resonance angiography, computer tomographic angiography, or digital subtraction angiography .
Ankle-brachial indices (ABIs) and toe digital pressures with pulse volume recordings can provide good clues to the perfusion of the foot. Findings are also predictive of wound healing, although they may be misleading in patients with diabetes and calcified noncompressible arteries. An ankle pressure greater than 55 mmHg suggests adequate leg perfusion. Research suggests that venous ulcers require a higher ABI for healing than arterial ulcers. The diagnosis of critical limb ischemia is supported by either an ankle systolic pressure of 50 mmHg or less or digital pressures less than 30 mmHg. Limitation of ABI is calcified atherosclerotic arteries mostly in diabetics giving higher false value of ABI due reduced compressibility caused by calcification.
Xenon–133 clearance to measure blood flow can help estimate the chance of wound healing. A rate of 2.6 mL/100 g is believed to be adequate for healing.
Transcutaneous oxygen tension may be measured; however, a wide discrepancy exists with the minimal level below which wound healing does not occur. Most agree that a pressure of 30–35 mmHg is sufficient for healing of more than 90 % of wounds.
7.5.1 Leg Ulcer Measurement Tools (LUMT)
Accurate and regular measurement of the wound is important to give an objective assessment of the effectiveness of the current management plan. The leg ulcer measurement tool (LUMT) is a validated tool that has been developed to quantify leg ulcer assessment and can be used to track change in wound status over time. Various methods have been used to document an ulcer of the lower extremity (Fig. 7.3). They can be broadly classified into the following:
Leg ulcer measurement tools
Graduated swab stick method
Structured light techniques
Alfred/Medseed wound imaging system
Video image analysis
Magnetic resonance imaging
Role of ulcer measurement tools is to see progress of wound healing, and these are instrumental in monitoring of wound healing after different modes of interventions. Only limited role of ulcer measurement tools is well defined in experimental studies of chronic ulcers.
7.5.2 Doppler Duplex Scanning
Due to rapid, easy, and inexpensive assessment, Duplex ultrasound can be considered as a screening tool for detecting vascular pathology in chronic ulcers. Combination of ultrasound with Doppler detects the distribution and extent of vascular disease. It is regarded as the investigation of choice for the diagnosis of venous reflux, thrombosis, arterial obstruction, and aneurysms [13, 14]. Stenosis and occlusion can be clearly demonstrated and differentiated with adequate information about surface characteristics and plaque content to direct the treatment plan according to etiology and anatomical delineation of pathology of the vascular segment affected. In chronic cases or during follow-up, collateral pathways and flow dynamics are demonstrated leading to the identification of acute, chronic, or recurrent thrombosis. Duplex scan is an excellent tool to differentiate tumors, cysts, hematoma, clots, thrombus, and foreign body in vascular tree. Considering its excellent sensitivity and availability, it is integral in the diagnosis and follow-up with effect on treatment, progression of disease, or developments of new pathology. Duplex is superior in the detection of venous reflux with a sensitivity greater than 75 %, compared to approximately 40 % for descending venography. Neglen and Raju suggest that combining Duplex scanning with air plethysmography helps differentiate severe venous disease from mild venous disease .
Considering the surgical options in chronic ulcers, plethysmography is used to detect and quantify arterial and venous diseases [16, 17]. Several types of plethysmography have been evolved such as air, photo, and strain gauge. Depending on the device used, pressure and flow measurements, waveform patterns, volume changes, amount of reflux, degree of venous obstruction, and the efficiency of calf muscle pumps can be calculated. All these parameters are important as the severity of the disease can be demonstrated to determine the impact of ulceration. So, these are good tests to assess treatment and progression of the disease. Venous pressure data are important in determining the need for surgical bypass or valve replacement. Quantitative data on venous obstruction, calf muscle pump ejection fraction, and reflux are provided by air plethysmography, whereas venous pressure studies assess the physiological importance of anatomic obstruction because the collaterals may or may not provide adequate compensation for an obstructed pathway. Dual significance with both diagnostic and prognostic efficacies is associated with plethysmography, but its use is limited mostly to academic and research purpose.
CT angiography showing popliteal artery aneurysm. Patient presented with ulceration of foot
CT angio showing bilateral femoral block at variable levels
In chronic ulcer, spiral CT angiography (CTA) is an accurate modality to assess the presence and extent of peripheral arterial disease (PAD). This investigation is done only if the active intervention is required to salvage the limb and improve the quality of life by reducing rate of limb loss and persistent pain. Modes of interventions are either endovascular, open surgery, or hybrid techniques. CT angiography has become popular due to rapid technical developments in terms of shorter acquisition times, thinner slices, higher spatial resolution, and improvement of multidetector computed tomographic scanners that enable the scanning of the whole vascular tree in a limited period with limited contrast . CT venography (CTV) is also accurate to determine proximal venous obstruction, but as it is relatively static, one cannot evaluate reflux. CT can also detect aneurysms, AV fistulae, and any other pathologies like neoplasms and can determine the extent of disease and involvement of surrounding structures. Both CT arteriography and CT venography are considered as excellent tools for differential diagnosis to detect vascular lesion in chronic ulcers .
18.104.22.168 Magnetic Resonance Imaging (MR Arteriography and MR Venography)
Despite limited availability and skilled interpretation of findings, magnetic resonance arteriography (MRA) equivalent to CT angiography is a noninvasive method to visualize the peripheral vasculature, to detect hemodynamically significant stenosis, and to distinguish focal from long-segment occlusive disease . Advantage of its use is that it does not need any contrast, so the patients with deranged renal functions may undergo MRA. But the disadvantage is that it takes a much longer time to perform and also cannot be used in the patients on pacemakers and any other prosthesis. Further claustrophobia and the sounds produced during the procedure may not be palatable to the patients. MRA has the ability to define the pattern of the disease and help in planning for arterial access sites (retrograde or antegrade). More specifically, MRA has proven useful in detecting occult runoff channels, which can be used for distal bypass . Ulcerations should be bright on T2-weighted imaging, with peripheral enhancement of the ulcer base. Magnetic resonance venography has a great accuracy in detecting proximal vein obstruction and may differentiate acute from chronic thrombosis . Drawback of MRV is failure to demonstrate venous reflux. MRA and MRV can be easily compared to CTA and CTV for excellency in differential diagnosis tool for vascular lesions.
Magnetic resonance angiography (MRA) can also be useful when evaluating lower extremity disease. Yucel et al. found that MRA was 94 % accurate in evaluating lower extremity vessels when compared to conventional angiography or surgery  Owen and coworkers found that MRA detected all runoff vessels when compared to conventional angiography and, in fact, was more sensitive than conventional arteriography for visualizing both runoff vessels and arterial stenosis .
Phlebography is usually not done because of the availability of noninvasive tests such as Duplex and relatively less invasive such as CT or MRI, but it can identify the location and extent of blood clots and enables the condition of the deep leg veins to be assessed. It is especially useful when there is a strong suspicion of deep vein thrombosis, after noninvasive tests have failed to identify the disease. Ascending venography also may be considered to obtain detailed anatomic information. This study can reveal axial channel patency, perforator incompetence, obstruction, and the presence of deep venous thrombosis. Phlebography can also be used to evaluate congenital vein problems and assess the function of the deep vein valves. Phlebography is a great method to demonstrate the extension of obstruction and all the collateral pathways. It can guide treatment and at the same time assess its effect. It is not used often, because it is painful, expensive, and time-consuming, exposes the patient to a fairly high dose of radiation, and can cause phlebitis, tissue damage, and the formation of deep vein thrombosis in a healthy leg. It is reserved for evaluating limbs that may need deep vein reconstruction or to open proximal vein obstruction .