Lymphatic Transit Research Articles

Evaluation of three different 99mTc-based mock-venom agents for lymphoscintigraphy studies in preclinical models of peripheral snakebite envenomation

Snakebite envenomation is one of the major public health concerns across many countries; with the WHO designating it as a ‘priority neglected tropical disease’ and stressing for a need to develop novel therapeutic strategies to reduce death and disability rate by end of 2030. Since a major component of venom; the high molecular weight (HMw) toxins enter the bloodstream through lymphatic system, research is focusing on modulating the lymphatic flow rate after topical application of suitable drug candidates. Present study compared the suitability of three radiopharmaceutical agents, namely 99mTc-Sulfur colloid (SC), 99mTc-Phytate (Phy) and 99mTc-Human serum albumin (HSA), to be used as mock-venom agent in studying modulation in lymphatic flow rate in preclinical models of peripheral snakebite envenomation using lymphoscintigraphy studies. The study was performed in 72 Sprague Dawley rats; divided into six groups of 12 rats each. Control groups were given intradermal injection (1.29–1.48 MBq in 100 μl normal saline) of either 99mTc-Phy/ 99mTc-SC/ 99mTc-HSA into the tail as ‘mock-venom’. In respective test groups, commercially available topical formulation (Anobliss® Cream) containing Nifedipine (Nif; 0.3% w/w) and Lidocaine (Lid; 1.5% w/w) was applied topically over the animals' lower body (tail and hind limbs) immediately within 20s of administering intradermal injection of the radiopharmaceutical. Any modulation in lymph transit time from periphery to systemic circulation was assessed using lymphoscintigraphy by taking dynamic gamma-scintigraphy images of 60s each till 1 h post-injection of the test radiopharmaceuticals. Significant difference in movement of the three radiopharmaceuticals was noted in terms of their lymphatic movement. 99mTc-Phy did not show significant travel through the lymphatics and the liver was faintly visualized in control as well as test intervention groups. In case of 99mTc-SC, significant changes in movement of the radiotracer after topical application of Nif/Lid in the test intervention groups were clearly noted in comparison to control (P < 0.05). Multiple numbers of lymph nodes (LNs) could be clearly visualized in control (5 ± 1 LNs) and test intervention groups (3 ± 1 LNs). Liver uptake was more prominent in control animals and it reduced significantly in test intervention groups. On the other hand, 99mTc-HSA showed lesser number of lymph nodes and higher accumulation in liver as compared to 99mTc-SC, suggesting very fast movement of this radiopharmaceutical. Results indicates that 99mTc-SC could be used as a suitable agent to mimic lymphatic transit behavior of HMw toxin components of snake venom and could therefore be used as a model in studying the effect of any test pharmacological intervention in modulating lymphatic transit rate. Additional advantage could be a significant reduction in the need for sacrificing large number of animals, particularly during initial screening phase of drug development cycle.

Multi-drug loaded microneedles for emergency treatment of snakebite envenomation

Snakebite envenomation is a WHO classified priority neglected disease, which manifests multiple local and systemic toxic effects. Intravenous antivenom therapy is the treatment of choice in clinical settings but it cannot be employed for pre-hospital management of envenomation cases due to certain limitations. On-field first-aid measures presently include use of pressure bandage immobilization (PBI), which has sub-optimal efficacy in managing snakebite casualties. There is therefore an urgent need for developing non-immunological, therapeutic interventions that could be self-administered immediately after snakebite, alone or in tandem with PBI, to reduce the morbidity and mortality. Venom toxins enter into the bloodstream via lymphatic pathway [e.g., high molecular weight (HMw) toxins] or directly ingress into the vasculature due to cytotoxic endothelium disruption [e.g., low molecular weight (LMw) toxins]. Recent literature has identified some pharmacological targets, which when applied topically impede the systemic absorption of HMw venom toxins by modulating lymphatic transit time, whereas a few others act as direct inhibitors of LMw toxins, when injected parentally. Based on available evidences our hypothesis shall lead to deliver formulation containing combination of drugs applied topically through convenient, self-administrated microneedles, either to delay absorption and lymphatic transit of HMw venom toxins into the bloodstream or to inhibit the mechanistic pathway of LMw toxins, and could therefore be more useful for pre-hospital management following snakebite as compared to PBI alone.

ICG lymphographic findings following immediate lymphatic reconstruction in breast cancer patients

Immediate lymphatic reconstruction (ILR), performed at the time of axillary lymph node dissection (ALND), has demonstrated promising reductions in breast cancer-associated lymphedema. However, questions remain over the effects of adjuvant therapies on the continued patency of the lymphaticovenous anastomosis. Our study aimed to assess lymphographic outcomes, including ICG pattern and LVB patency, in patients at high risk for breast cancer-associated lymphedema following axillary ILR. Baseline ICG lymphography studies performed during ILR of 15 patients were compared to repeat ICG studies obtained during second-stage breast reconstructive procedures to assess for changes in lymphatic flow patterns through the at-risk arm and transit into the axilla. All 15 patients in this study demonstrated linear lymphatic flow in baseline lymphography. Repeat lymphographic studies showed linear lymphatic transit in 12/15 patients. Of these 12 patients, 10 received chemotherapy, and all 12 received post-mastectomy radiation (PMRT). Dermal backflow patterns were recorded in 3/15 patients. All 3 patients received chemotherapy and 2/3 underwent PMRT. Additionally, repeat ICG studies of 7/12 lymphedema-free patients demonstrated clear visualization of linear ICG flow from the lymphatics of the arm into the axilla. We have demonstrated that ICG lymphography can be implemented as a postoperative tool to assess lymphatic function in patients who have undergone ILR in the axilla. Repeat ICG studies in the majority of patients demonstrated linear ICG flow similar to baseline studies. Additionally, ICG flow patterns through the axilla in repeat lymphography provided visual evidence supporting sustained LVB patency, despite axillary irradiation.

6: ICG-Fluorescence Lymphography After Immediate Lymphatic Reconstruction

Purpose:Immediate lymphatic reconstruction (ILR), performed at the time of axillary lymph node dissection (ALND), has demonstrated promising reductions in the development of breast-cancer associated lymphedema. However, questions remain regarding the effects of adjuvant therapies on the continued patency of the lymphaticovenous anastomosis. The aim of our study is to assess lymphographic outcomes, including ICG pattern and LVB patency, following axillary ILR in patients at high risk for breast cancer associated lymphedema..Methods:Baseline ICG studies of 15 patients who underwent ILR were compared to studies obtained during secondary stage breast reconstructive procedures to assess for any changes in lymphatic morphology and transit in the at-risk arm.Results:All 15 patients in this study demonstrated linear lymphatic flow in intra-operative lymphography studies performed during the initial lymphatic reconstruction. An average of 2.4 (range 1-4) LVBs were performed per patient. Only 1 patient in this study group had preservation of in-continuity lymphatics at time of ALND. Followup lymphographic studies showed clear, linear lymphatic transit in 12/15 patients. Of these 12 patients, an average of 2.5 LVBs were performed, 10 received chemotherapy (7 neoadjuvant, 3 adjuvant), and all 12 received post mastectomy radiation (PMRT). Dermal backflow patterns of varying severity were recorded in 3/15 patients, two of whom showed signs of lymphedema prior to their followup study and the last went on to develop clinically detectable lymphedema. Of these 3 patients, an average of 2 LVBs were performed, all received chemotherapy (2 neoadjuvant, 1 adjuvant) and 2/3 underwent PMRT. Of the 12 patients that remain lymphedema-free, 7 post-operative studies demonstrated clear visualization of linear ICG flow from the lymphatics of the arm into the axilla without evidence of lymphatic collateralization. An average of 3 LVBs were performed in this group and 100% of these patients received adjuvant radiation.Conclusion:We have demonstrated that ICG lymphography can be implemented as a post-operative tool to assess lymphatic function in patients who have undergone ILR in the axilla. Post-operative imaging studies in the majority of patients demonstrated linear ICG flow with evidence of lymphatic contractility and velocity similar to baseline studies obtained at the time of lymphadenectomy and ILR. Additionally, ICG flow patterns through the axilla in post-operative imaging studies provided visual evidence supporting sustained LVB patency despite inflammation and tissue fibrosis associated with axillary irradiation.

Pathophysiological and anatomical basis of lymphatic transit of cancer cells and role of the lymphatic system: a review of published literature

Cancer metastasis involves dissemination of malignant cells from the primary tumor, via local lymphatic vessels to gain access to systemic circulation, while evading the destruction by immune cells, followed by successful extravasation and initiation of malignant growth in the distant organ. Despite the obvious contribution of the lymphatic system to the metastatic spread of cancer, basic research regarding the mechanisms leading to tumor dissemination via lymphatic vessels has been limited for years. Recent identification of molecular growth factors of lymphangiogenesis have led to new advances in our understanding of the underlying mechanisms of tumor metastasis. These growth factors have enabled scientists to better identify peritumoral lymphatics and to visualize precisely the ingrowth of tumor cells into the lumen of lymphatic capillaries. Moreover, it has been shown that these molecular markers secreted from a primary tumor can induce lymphangiogenesis in close regional lymph nodes, even prior to tumor cells arrival, which may facilitate metastasis spread. Comprehensive research of the multiplex interactions between tumor cells, lymphatics and the immune system will be crucial to further enhance the development of therapeutic and prognostic approaches to cancer. This review presents the ontogeny and anatomy of the lymphatic vasculature, discuss the immunological, molecular and physiological control of lymphatic vessel function, and explore the contribution of the lymphatic system to the development of metastases.

Impact of Locally Administered Carboxydextran-Coated Super-Paramagnetic Iron Nanoparticles on Cellular Immune Function.

Interstitially administered iron oxide particles are currently used for interoperative localization of sentinel lymph nodes (LNs) in cancer staging. Several studies have described concerns regarding the cellular accumulation of iron oxide nanoparticles relating them to phenotype and function deregulation of macrophages, impairing their ability to mount an appropriate immune response once an insult is present. This study aims to address what phenotypic and functional changes occur during lymphatic transit and accumulation of these particles. Data show that 60 nm carboxydextran-coated iron nanoparticles use a noncellular mechanism to reach the draining LNs and that their accumulation in macrophages induces transient phenotypic and functional changes. Nevertheless, macrophages recover their baseline levels of response within 7 days, and are still able to mount an appropriate response to bacterially induced inflammation.

Lymphatic transit rate as a predictive parameter for nodal metastasis in primary limb malignant melanoma

BackgroundThe status of sentinel lymph node (SLN) is one of the most predictive prognostic factors in patients with clinically localized malignant melanomas (MMs). However, since the positive SLN metastatic rate is as low as 20%, it is desirable to minimize SLN biopsy performance with imaging. By dynamic lymphoscintigraphy, we have proposed the lymphatic transit rate (LTR), the value that the distance between the primary lesion and SLN is divided by scintigraphic saturation time. LTR represents the scintigraphic saturation velocity and can be used for evaluation of metastasis of skin cancers. MethodsDynamic lymphoscintigraphy data from 36 lymph nodes in 36 patients with primary MM on the limb were analyzed. The initial sites of the MMs were the lower limb in 24 patients and the upper limb in 12 patients. Histopathologically, nodal metastasis was found in 10 patients. ResultsIn the lower limb MM, the mean LTRs were 3.49 cm/min in histologically non-metastatic SLNs and 4.49 cm/min in histologically metastatic SLNs (P = 0.0056). In the upper limb MM, the mean LTRs were 2.59 cm/min in non-metastatic SLNs and 3.94 cm/min in metastatic SLNs (P = 0.0162). Thus, significantly higher LTRs were obtained in the metastatic SLNs. All SLNs with LTR < 4.0 cm/min in the lower limb MM and those with LTR < 3.0 cm/min in the upper limb MM were non-metastatic. ConclusionLTR is a useful predictive indicator for nodal metastasis and SLN biopsy performance in MMs.

Quantity of Lymph Nodes in the Vascularized Lymph Node Transfer Influences Its Lymphaticovenous Drainage.

The purpose of this study was to: (1) evaluate the mechanism of lymph drainage through a vascularized lymph node (VLN) flap, and (2) investigate if the number of VLNs impacts lymph transit time through the flap. Twenty-seven axillary VLN flaps were elevated in 14 Sprague-Dawley rats and divided into three groups (n = 9 each) based on the number of lymph nodes present: group 1 (0-VLNs), group 2 (2-VLNs), and group 3 (4-VLNs). Indocyanine green (n = 8/group) and Alexa680-albumin (n = 1/group) were injected into the edge of flaps and the latency period between injection and fluorescence in the axillary vein was recorded. Stereomicroscopic fluorescent lymphography was performed to directly visualize lymphatic transit through VLNs. Fluorescence was detected in the axillary vein after 229s [47-476], 79s [15-289], and 56s [16-110] in group 1, 2, and 3, respectively (p < 0.01). There was a negative correlation between the number of VLNs in the flap and the latency period (r = -0.59; p < 0.05). Median flap weights were comparable in group 1, 2, and 3 (258 mg [196-349], 294 mg [212-407], 315 mg [204-386], respectively; p = 0.54). Stereoscopic lymphography allowed direct visualization of lymphatic fluid transit through VLNs. Lymphatic fluid in VLN flaps drains into the venous system mainly by passing through the afferent lymphatics and lymph nodes. A secondary mechanism appears to be the diffusion of fluid into the venous system via intratissue lymphaticovenous connections created during flap elevation. Increasing the number of lymph nodes in the flap is associated with a more rapid transit of fluid.

Use of Sequential Pneumatic Compression Devices to Facilitate Propagation of Contrast during Intranodal Lymphangiography

PurposeTo examine effects of lower extremity sequential compression devices (SCDs) on lymphatic transit during intranodal lymphangiography (IL) and thoracic duct interventions. Materials and MethodsA retrospective review of 19 SCD-assisted IL (IL-SCD) procedures was performed. The control group comprised 18 consecutive IL-guided procedures performed in the immediately preceding time period. For IL-SCD procedures, SCDs were placed onto patients’ calves before sterile preparation. Total procedure time and lymphatic transit time were measured. Mean age was 52 years in the IL-SCD group and 64 years in the control group. In the control group, 100% (18/18) of patients had a chylous leak, whereas only 74% (14/19) of patients in the IL-SCD group had a leak. ResultsIn the IL-SCD group, mean total procedure time was 75 minutes (range, 34–126 min), and mean lymphatic transit time was 29 minutes (range, 8–63 min). In the control group, mean total procedure time was 105 minutes (range, 51–203 min), and mean lymphatic transit time was 56 minutes (range, 28–117 min). Lymphatic transit time and procedure time were significantly reduced in the IL-SCD group (P < .01 and P < .05, respectively). ConclusionsUse of lower extremity SCDs reduces lymphatic transit time and IL-dependent procedure time.

Lymphatic transit rate as a novel predictive parameter for nodal metastasis in primary truncal skin cancers.

Prediction of nodal metastasis in skin cancer before sentinel lymph node (SLN) biopsies is ideal to avoid unnecessary SLN biopsy performance. Primary truncal skin cancers are characterized by the lymphatic flow that drains from the primary lesion, occasionally to plural nodal basins. The scintigraphic appearance time (SAT), defined as the time between radionuclide injection and first SLN visualization, can potentially predict nodal metastasis, and a short SAT is a predictive parameter for metastasis. We recently introduced a novel method to measure the lymphatic flow rate using dynamic lymphoscintigraphy exhibiting a time-activity curve in the SLN. The time at which the count reaches a plateau in the SLN is termed the scintigraphic saturation time (SST) and can be a good alternative to the SAT. Moreover, the value obtained by division of the distance between the primary lesion and the SLN by the SST was termed the lymphatic transit rate (LTR), which represents the scintigraphic saturation velocity. In the present study, we evaluated LTR as a predictive parameter for nodal metastasis. Data for 22 lymph nodes from 18 patients with primary truncal skin cancers were used. Histopathologically, nodal metastasis was determined in nine nodes of eight patients. Because the mean LTR were 1.84cm/min in non-metastatic SLN and 2.38cm/min in metastatic SLN, the LTR was significantly higher in metastatic SLN than in non-metastatic SLN. All SLN with LTR of less than 1.8cm/min were histopathologically evaluated as non-metastatic. The LTR may be a predictive indicator for nodal metastasis.

A unifying theory of tonsillitis, intratonsillar abscess and peritonsillar abscess

We review existing models of the pathogenesis of peritonsillar abscess (PTA) and intra-tonsillar abscess (ITA) and present a novel pathophysiologic model based upon observed histopathology in 2 ITAs and 10 PTAs and acute tonsillitis cases. ITA is rare, and prevailing models are only able to account for a minority of cases. The tonsillar lymphatic ultrastucture and the rapid nature of intratonsillar lymphatic transit, offer the framework for a unifying model of the development and progression of tonsillitis, PTA and ITA.

Measurement of cutaneous lymphatic flow rates in patients with skin cancer: area extraction method.

Some recent reports have revealed that the long scintigraphic appearance time (SAT), defined as the time between radionuclide injection and first sentinel lymph node (SLN) visualization in lymphoscintigraphy, is a negative predictive parameter of nodal metastasis in patients with melanoma. However, most of the methods used to measure the SAT were ambiguous because they utilized visualization in lymphoscintigraphy. We herein introduce a novel method by which to measure the SAT and lymphatic flow rate. The data of 33 patients with primary skin cancer were used. Sequential images were obtained using dynamic lymphoscintigraphy, and a time-activity curve of the SLN was created. The time at which the counts reached plateau was newly defined as an alternative to the SAT and was termed the scintigraphic saturation time (SST). The figure obtained by division of the distance by the SST was newly defined as an alternative to the lymphatic flow rate and termed the lymphatic transit rate (LTR). The SST was clearly determined. It ranged from 220 to 1430 s (mean, 805 s). Pathological examination revealed nodal metastasis in five patients. In 28 patients without metastasis, the mean LTR was in the order of lower limbs (4.07 ± 0.35 cm/min), upper limbs (2.67 ± 0.33 cm/min), trunk (1.79 ± 0.47 cm/min), and head and neck (1.11 ± 0.22 cm/min). The LTRs were higher in patients with nodal metastasis than those without. This method may be effective for accurate measurement of the SAT and lymphatic flow rate.

3:30 PM Abstract No. 45 - Dynamic magnetic resonance lymphangiography (MRL): a new technique to image the central conducting lymphatics (CCL)

Purpose Previous MR techniques for CCL using heavily T2-weighted sequences or digital contrast injection have limitations:inability to distinguish edema from small lymphatics, variable opacification of CCL,venous contamination, lack of functional information and artifacts.We describe a new MR technique that provides rapid,selective opacification of the CCL with reliable visualization of thoracic duct (TD) and cisterna chyli (CC), dynamic imaging of lymphatic transit and lack of venous contamination. Materials and Methods 3 MRLs were performed: Patient 1 : 13/F:Recurrent chylopericardium,nevi,renal and splenic cysts,lytic bone lesions,interstitial lung disease, lung AVM’s.MRL to rule out TD obstruction Patient 2 : 20/F:post Whipple's for pancreatic SPEN with chronic protein losing enteropathy imaged for mesenteric CLR Patient 3 : 29/F:left leg chronic lymphedema, pelvic and retroperitoneal cysts to screen for CCL anomalies Method : Under ultrasound guidance, 22/20G angiocatheters were placed within the medulla of bilateral inguinal lymph nodes followed by intranodal injection of gadolinium and dynamic MR imaging with the following parameters: torso phased array coil with a large FOV to cover lower neck to inguinal region,single dose contrast with appropriate dilution of 1:1 or 1:2 with normal saline injected simultaneously into both inguinal nodes,dynamic 3D T1 FFE volumetric sequence repeated every 2 minutes until contrast noted in retroperitoneal lymphatics,then every minute to study transit to cisterna chyli and TD. Results Patient 1 : CLR from the TD into dysplastic lymphatic channels in the mediastinum, pericardium, left lower lobe and left pleural cavity suggestive of lymphangiectasia. No delay in opacification of the central TD excluding obstruction. Patient 2 : Normal retroperitoneal lymphatics,CC, TD,no mesenteric CLR Patient 3 : Lymphatic outflow from right leg into large aneurysmal dysplastic lymphatic channels in the pelvis and retroperitoneum with poor visualization of TD. Extensive collateral lymphatic pathways in body wall. Conclusion Dynamic MRL is a new, minimally-invasive tool to evaluate the central lymphatics, providing structural and functional information that is critical to therapeutic decision making.

The Antibody Drug Absorption Following Subcutaneous or Intramuscular Administration and Its Mathematical Description by Coupling Physiologically Based Absorption Process with the Conventional Compartment Pharmacokinetic Model

The main objective of this paper is to propose a quantitative model to describe the absorption process for monoclonal antibody (mAb) following subcutaneous (SC) or intramuscular (IM) administration. A hybrid model was established by coupling the physiologically based absorption process with a conventional pharmacokinetic-pharmacodynamic (PK-PD) or PK model associated with intravenous infusion. Key physiological parameters evaluated include the volume distribution before systemic absorption, mAb drug clearance during lymphatic transport, the neonatal Fc receptor (FcRn) capacity, the intrinsic drug clearance via lysosomal proteolytic process, and the lymphatic flow rate. Sensitivity analyses were performed to identify those physiological parameters significantly impacting time to peak concentration (T(max)) or drug bioavailability. Simulation results showed that lymphatic flow rate is the only influential factor to T(max). Lymphatic transit time and drug clearance during lymphatic transport are most influential to bioavailability but not identifiable in their effects. Bioavailability is positively related to the lymphatic flow only at its low range (i.e., at <0.5-fold of the selected value of 0.043 mL/min). The rest of physiological parameters only have marginal effects on either drug bioavailability or T(max). Finally, simulation results confirmed lymphatic transport as the major route of mAb delivery.

W1970 Increased Extracellular Pressure Enhances Cancer Cell β1-Integrin Binding Affinity Through Phosphorylation of β1-Integrin At Threonine 788/789

Exposure to increased extracellular pressure activates intracellular signals that stimulate cancer cell adhesion to matrix proteins and endothelial cell monolayers In Vitro, and surgical wounds In Vivo by a β1-integrin-dependent mechanism. Such increased adhesiveness may contribute to the metastatic potential of cancer cells exposed to increased pressure during vascular and lymphatic transit, in the tumor microenvironment, or through surgical manipulation and postoperative bowel edema. We sought to assess whether pressure-induced cell adhesion is mediated by changes in β1-integrin binding affinity or avidity and whether these changes are phosphorylation-dependent. 15 mmHg increased pressure was applied for 30 minutes to suspended cells using a temperatureand pressure-controlled box. We used a flow cytometric assay to quantify changes in integrin affinity and clustering by measuring differences in binding between single Arg-Gly-Asp (RGD)-Fc ligands and RGD-Fc-F(ab')2 multimeric complexes. We then assessed pressure-stimulated phosphorylation of β1-integrin S785 and T788/9 residues in human SW620 colon cancer cells and primary malignant colonocytes. Finally, we employed GD25 β1-integrin null murine fibroblasts stably transfected with either wild-type β1-integrin, S785A, or T788/9A phosphorylation site mutants to assess the dependence of pressure-stimulated cell adhesion on β1-integrin site-specific phosphorylation. RGD-Fc, but not RGD-Fc-F(ab')2, binding to SW620 cells was significantly increased (23±4%; p<0.02; n=4) under elevated pressure, suggesting pressure modulates β1-integrin affinity, but fails to induce integrin clustering. Increased pressure stimulated β1-integrin phosphorylation at both S785 (31±7%; p<0.02; n=5) and T788/9 (28±5%; p<0.01; n=5) residues in SW620 cells. Primary human colon cancer cells responded similarly. GD25 β1-integrin wild-type cells displayed a 30±8% (p<0.02; n=6) increase in adhesion to collagen I under elevated pressure, an effect absent in GD25 β1-integrin null cells (n=6). GD25 cells expressing the S785A β1-integrin phosphorylation mutant also displayed a 19±3% (p<0.01; n=6) increase in adhesion under pressure. However, expression of T788/ 9A β1-integrin completely blocked this effect (n=6). These results suggest that the observed increase in cell adhesion accompanying exposure to elevated pressure reflects enhanced β1integrin affinity and requires phosphorylation of the cytoplasmic tail of β1-integrin at T788/ 9. The β1-integrin T788/9 phosphorylation site may offer a unique therapeutic target for the modulation of pressure-stimulated cell adhesion and subsequent tumor metastasis.

Interpretation of lymphoscintigrams in suspected lymphoedema: contribution of delayed images.

Interpretation of lymphoscintigrams in patients with extremity oedema may be adversely affected by any variation in the acquisition protocol. The purpose of this study was to determine whether delayed (2-24 h post-injection) views provide information incremental to the first 60 min of acquisition. In a 5-year period, 31 patients (10 males, 21 females, mean age 46 years) with extremity oedema or recurrent cellulitis underwent lymphoscintigraphy using 99Tcm-antimony trisulphide colloid (99Tcm-Sb2S3). All subjects underwent an initial dynamic acquisition of the pelvis and legs for 60 min, with further images obtained after 2-24 h. Films and reports were retrospectively reviewed by an experienced observer to determine whether delayed views provided information incremental to early images. Using standard qualitative criteria, lymphoscintigrams were classified as normal (n = 12) or consistent with lymphoedema (n = 19). However, 6 of 19 (32%) patients with lymphoedema displayed normal transit of radiopharmaceutical and a normal appearance of regional lymph nodes on views acquired up to 1 h after injection; localized dermal backflow (n = 5) or lymphocoele (n = 1) were seen only on delayed images (P < 0.02). These data indicate that delayed lymphoscintigraphy images are important for the diagnosis of lymphoedema and should be obtained even when lymphatic transit of 99Tcm-Sb2S3 and lymph node appearance at 1 h are normal.

Lymphatic flow rates and first‐aid in simulated peripheral snake or spider envenomation

To demonstrate and define normal lymphatic transit times by lymphoscintigraphy and to evaluate the efficacy of the currently recommended first-aid measures for the management of snake or spider envenomation. The nuclear medicine department of a major teaching hospital. Twenty-four subjects received either intradermal or subcutaneous injections of 99mtechnetium antimony sulfur colloid (0.1 mL) in both hands/forearms and feet/legs. This simulated a snake or spider bite. Fifteen of the subjects had first-aid in the form of firm bandages and splints applied to an upper and a lower limb immediately after injection. The progress of the radiotracer was followed with a large field of view gamma camera. If no egress of radiotracer was seen in the bandaged limbs, the subject walked until radioactivity was detected. The mean (+/- SEM) periphery-to-systemic circulation transit time after subcutaneous injection was 58 (+/- 7) minutes. The first-aid was found to be very effective when applied with bandage pressures ranging from 40 to 70 mmHg (5.3-9.3 kPa) in the upper limb and 55 to 70 mmHg (7.3-9.3 kPa) in the lower limb. Lower and higher bandage pressures were ineffective. However, despite first-aid measures, egress of radiotracer, even in the upper limbs, was seen in all subjects who walked for 10 minutes or more. Firm pressure bandaging is an effective means of restricting the lymphatic flow of toxins after envenomation, provided the bandage is applied within the defined pressure range. Strict limb immobilisation is necessary to minimise lymphatic flow, and walking after upper or lower limb envenomation will inevitably result in systemic envenomation despite first-aid measures.