Pattern recognition in five-phase bone scintigraphy: diagnostic patterns of reflex sympathetic dystrophy in adults

EANM position paper on challenges and opportunities of full-ring 360° CZT bone imaging: it's time to let go of planar whole-body bone imaging

The introduction of smaller footprint, more sensitive Cadmium-Zinc-Telluride (CZT)-based detectors with improved spatial and energy resolution has enabled the design of innovative full-ring 360° CZT SPECT/CT systems (e.g., VERITON® and StarGuide™). With this transformative technology now aiming to become mainstream in clinical practice, several critical questions need to be addressed. This EANM position paper provides practical recommendations on how to use these devices for routine bone SPECT/CT studies, facilitating the transition from traditional planar whole-body imaging and conventional SPECT/CT to these novel systems. In particular, initial guidance is provided on imaging acquisition and reporting workflows, image reconstruction, and CT acquisition parameters. Given the emerging nature of this technology, the available evidence base is still limited, and the proposed adaptations in workflows and scan protocols will likely evolve before being integrated into definitive guidelines. In the meantime, this EANM position paper serves as a comprehensive guide for integrating these advanced hybrid SPECT/CT imaging systems into clinical practice and outlining areas for further study.

Technical concepts on blood pool phase SPECT (acquisition, reconstruction)

Guidelines for bone scintigraphy are well established and recommend the use of planar early phase images to investigate a number of clinical indications. With recent advances in gamma camera technology the use of SPECT/CT imaging in the early phases is now possible, offering the potential of improved diagnostic confidence and prognostic value. To date little work has been carried out to optimize the acquisition of early phase bone images using SPECT/CT with most of the available studies acquiring SPECT images after the traditional planar images to allow comparison of the two techniques. Imaging durations of 7 to 10 minutes have been commonly used. However, the use of iterative reconstruction algorithms has been investigated with rapid SPECT imaging to allow imaging durations as low as 4 minutes. The use of CZT based systems with increased sensitivity and improved energy and spatial resolution also offers the potential to reduce imaging times. The optimization of projection measurement order has been investigated as a method of reducing image artefacts as a result of changing tracer distribution during the SPECT acquisition. In this article we consider the current state of early phase SPECT imaging and possible areas for future investigation as well as recommendations for departments looking to adopt blood pool SPECT imaging as part of their routine clinical practice.

Three-phase Bone Scintigraphy Can Predict the Analgesic Efficacy of Ketamine Therapy in CRPS

OBJECTIVES

The efficacy of ketamine in relieving complex regional pain syndrome (CRPS) lacks predictive factors. The value of three-phase bone scintigraphy (TPBS) was assessed for this purpose.

MATERIALS AND METHODS

TPBS was performed in 105 patients with unilateral, focal CRPS of type 1 before 5 days of ketamine infusions. Tracer uptake was measured in the region of interest concerned by CRPS and the contralateral homologous region. For the 3 scintigraphic phases (vascular, tissular, and bone phases), an asymmetry ratio of fixation was calculated between the affected and the unaffected sides (vascular phase [VPr], tissular phase [TPr], and bone phase [BPr]). Ketamine efficacy was assessed on pain intensity scores.

RESULTS

Ketamine-induced pain relief did not correlate with VPr, TPr, and BPr, but with the ratios of these ratios: BPr/TPr (r=0.32, P=0.009), BPr/VPr (r=0.34, P=0.005), and TPr/VPr (r=0.23, P=0.02). The optimum cut-off value for predicting the response to ketamine therapy was >1.125 for BPr/TPr, >1.075 for BPr/VPr, and >0.935 for TPr/VPr. The combination of increased values of BPr/TPr, BPr/VPr, and TPr/VPr was highly significantly associated with ketamine therapy outcome.

CONCLUSIONS

The relative hyperfixation of the radioactive tracer in the limb region concerned by CRPS in phases 2 and 3 versus phase 1 of TPBS correlated positively to the analgesic efficacy of ketamine. This study shows for the first time the potential predictive value of TPBS regarding ketamine therapy outcome. In addition, these results suggest that the analgesic action of ketamine is not restricted to "central" mechanisms, but may also involve "peripheral" mechanisms related to tissue inflammation and bone remodeling.

Usefulness of bone scintigraphy for the diagnosis of Complex Regional Pain Syndrome 1: A systematic review and Bayesian meta-analysis

BACKGROUND

Since 2007, the Budapest criteria are recommended for the diagnosis of Complex Regional Pain Syndrome (CRPS) 1. The usefulness of bone scintigraphy (BS, index test) for the diagnosis of CRPS 1 remains controversial. Imperfect reference tests (RT) result in underestimation of the diagnostic accuracy of BS. Further, biased results can occur when a dependency between the RT and BS exists. The objective was to assess the impact of different RTs, specifically the Budapest criteria, and the assumed imperfect nature of the RT on the diagnostic accuracy of BS. Further, we analyzed the association between baseline characteristics and positive BS in patients with CRPS 1.

METHODS

Systematic literature review and Bayesian meta-analysis to assess the test accuracy of BS with and without accounting for the imperfect nature of the RT. We examined correlations (Spearman correlation coefficients / Wilcoxon tests) between baseline characteristics and the proportion of positive BS in patients with CRPS 1.

RESULTS

The pooled sensitivity was 0.804 (95% credible interval (CI) 0.225-1.0, 21 studies) and specificity 0.853 (95%CI 0.278-1.00). Sensitivity and specificity of BS increased when accounting for the imperfect nature of the RT. However, in studies using Budapest criteria as reference, the sensitivity decreased (0.551; 95% CI 0.046-1) and the specificity increased (0.935; 95% CI 0.306-1). Shorter disease duration and a higher proportion of males were associated with a higher proportion of positive BS (27 studies, disease duration <52 weeks Wilcoxon test p = 0.047, female proportion Spearman correlation -0.63, p = 0.009).

CONCLUSION

Compared to the accepted Budapest diagnostic criteria BS cannot be used to rule-in the diagnosis of CRPS 1. In patients with negative BS CRPS 1 is less likely the underlying illness. Studies using older or no diagnostic criteria should not be used to evaluate the diagnostic accuracy of BS in CRPS 1.

Bayesian meta-analysis of test accuracy in the absence of a perfect reference test applied to bone scintigraphy for the diagnosis of complex regional pain syndrome

There is conflicting evidence about the accuracy of bone scintigraphy (BS) for the diagnosis of complex regional pain syndrome 1 (CRPS 1). In a meta-analysis of diagnostic studies, the evaluation of test accuracy is impeded by the use of different imperfect reference tests. The aim of our study is to summarize sensitivity and specificity of BS for CRPS 1 and to identify factors to explain heterogeneity. We use a hierarchical Bayesian approach to model test accuracy and threshold, and we present different models accounting for the imperfect nature of the reference tests, and assuming conditional dependence between BS and the reference test results. Further, we include disease duration as explanatory variable in the model. The models are compared using summary ROC curves and the deviance information criterion (DIC). Our results show that those models which account for different imperfect reference tests with conditional dependence and inclusion of the covariate are the ones with the smallest DIC. The sensitivity of BS was 0.87 (95% credible interval 0.73-0.97) and the overall specificity was 0.87 (0.73-0.95) in the model with the smallest DIC, in which missing values of the covariate are imputed within the Bayesian framework. The estimated effect of duration of symptoms on the threshold parameter was 0.17 (-0.25 to 0.57). We demonstrate that the Bayesian models presented in this paper are useful to address typical problems occurring in meta-analysis of diagnostic studies, including conditional dependence between index test and reference test, as well as missing values in the study-specific covariates.

Concordance of qualitative bone scintigraphy results with presence of clinical complex regional pain syndrome 1: meta-analysis of test accuracy studies

BACKGROUND

To date, no attempt has been made to investigate the agreement between qualitative bone scintigraphy (BS) and the presence of complex regional pain syndrome 1 (CRPS 1) and the agreement between a negative BS in the absence of CRPS 1.

AIMS

To summarize the existing evidence quantifying the concordance of qualitative BS in the presence or absence of clinical CRPS 1.

DATA SOURCES

We searched Medline, Embase, Dare and the Cochrane Library and screened bibliographies of all included studies.

STUDY ELIGIBILITY CRITERIA

We selected diagnostic studies investigating the association between qualitative BS results and the clinical diagnosis of CRPS 1. The minimum requirement for inclusion was enough information to fill the two-by-two tables.

RESULTS

Twelve studies met our inclusion criteria and were included in the meta-analysis. The pooled mean sensitivity of 12 two-by-two tables was 0.87 (95% CI, 0.68-0.97) and specificity was 0.69 (95% CI, 0.47-0.85). The pooled mean sensitivity for the subgroup with clearly defined diagnostic criteria (seven two-by-two tables) was 0.80 (95% CI, 0.44-0.95) and specificity was 0.73 (95% CI, 0.40-0.91).

CONCLUSIONS

Based on this study, clinicians must be advised that a positive BS is not necessarily concordant with presence of absence or CRPS 1. Given the moderate level of concordance between a positive BS in the absence of clinical CRPS 1, discordant results potentially impede the diagnosis of CRPS 1.

Neuropeptides, neurogenic inflammation and complex regional pain syndrome (CRPS)

This review explains symptoms and nature of neuropeptide signaling and its importance for clinical symptoms of CRPS. Neurogenic inflammation regularly accompanies excitation of primary afferent nociceptors. It has two major components-plasma extravasation and vasodilatation. The most important mediators are the calcitonin gene-related peptide (CGRP) and substance P (SP). After peripheral trauma immune reaction (e.g. cytokines) and the attempts of the tissue to regenerate (e.g. growth factors) sensitize nociceptors and amplify neurogenic inflammation. This cascade of events has been demonstrated in rat models of CRPS. Clinical findings in these animals strongly resemble clinical findings in CRPS, and can be prevented by anti-cytokine and anti-neuropeptide treatment. In CRPS patients, there is meanwhile also plenty of evidence that neurogenic inflammation contributes to clinical presentation. Increased cytokine production was demonstrated, as well as facilitated neurogenic inflammation. Very recently even "non-inflammatory" signs of CRPS (hyperhidrosis, cold skin) have been linked to neuropeptide signaling. Surprisingly, there was even moderately increased neurogenic inflammation in unaffected body regions. This favors the possibility that CRPS patients share genetic similarities. The future search for genetic commonalities will help us to further unravel the "mystery" CRPS.

Imaging in Early Posttraumatic Complex Regional Pain Syndrome

OBJECTIVES

The complex regional pain syndrome type I (CRPS I) still is difficult to diagnose in posttraumatic patients. As CRPS I is a clinical diagnosis the characteristic symptoms have to be differentiated from normal posttraumatic states. Several diagnostic procedures are applied to facilitate an early diagnosis, although their value for diagnosing posttraumatic CRPS I is unclear.

METHODS

One hundred fifty-eight consecutive patients with distal radial fracture were followed up for 16 weeks after trauma. To assess the diagnostic value of the commonly applied methods a detailed clinical examination was carried out 2, 8, and 16 weeks after trauma in conjunction with bilateral thermography, plain radiographs of the hand skeleton, three phase bone scans (TPBSs), and contrast-enhanced magnetic resonance imaging (MRI). All imaging procedures were assessed blinded.

RESULTS

At the end of the observation period 18 patients (11%) were clinically identified as having CRPS I and 13 patients (8%) revealed an incomplete clinical picture which were defined as CRPS borderline cases. The sensitivity of all diagnostic procedures used was poor and decreased between the first and the last examinations (thermography: 45% to 29%; TPBS: 19% to 14%; MRI: 43% to 13%; bilateral radiographs: 36%). In contrast a high specificity was observed in the TPBS and MRI at the eighth and sixteenth-week examinations (TPBS: 96%, 100%; MRI: 78%, 98%) and for bilateral radiographs 8 weeks after trauma (94%). The thermography presented a fair specificity that improved from the second to the sixteenth week (50% to 89%).

DISCUSSION

The poor sensitivity of all tested procedures combined with a reasonable specificity produced a low positive predictive value (17% to 60%) and a moderate negative predictive value (79% to 86%). These results suggest, that those procedures cannot be used as screening tests. Imaging methods are not able to reliably differentiate between normal posttraumatic changes and changes due to CRPS I. Clinical findings remain the gold standard for the diagnosis of CRPS I and the procedures described above may serve as additional tools to establish the diagnosis in doubtful cases.

Quantitative three-phase bone scintigraphy in the evaluation of intravenous regional blockade treatment in patients with stage-I reflex sympathetic dystrophy of upper extremity

OBJECTIVE

To investigate the role of quantitative three phase bone scintigraphy (QTPBS) in the evaluation of efficacy of intravenous regional blockade treatment in patients having reflex sympathetic dystrophy (RSD) of the upper extremity.

MATERIAL AND METHODS

Twenty-six patients with stage-I RSD were focused on in this study. Patients were treated with physical therapy and intravenous (I.V.) regional blockade therapy consisting of dexamethasone and lidocaine. All patients were clinically evaluated before and 1 month after the completion of the therapy protocol. QTPBS was applied to patients before therapy and 1 month after the therapy. As a control group, 11 healthy subjects also underwent QTPBS. Perfusion, hyperemic and fixation indices were calculated from three-phase bone scintigraphy.

RESULTS

All patients showed statistically significant clinical improvement after the therapy (p < 0.01). Pre-treatment, perfusion (1.67 +/- 0.63), hyperemic (1.44 +/- 0.48) and fixation (1.69 +/- 0.48) indices of patients were higher than those of healthy subjects (PI: 0.95 +/- 0.05, HI: 0.94 +/- 0.06, FI: 1.01 +/- 0.2) (p < 0.01) and all indices significantly decreased after the treatment (PI: 1.33 +/- 0.46, HI: 1.18 +/- 0.23, FI: 1.42 +/- 0.26) (p < 0.01).

CONCLUSION

I.V. regional blockade therapy combined with corticosteroids is a simple, safe and effective method for the treatment of patients with stage-I RSD in the upper extremity. QTPBS is a valuable and objective method to evaluate the response to therapy and may be useful for staging of patients and predicting the response to therapy.

The predictive value of additional late blood pool imaging to the three-phase bone scan in the diagnosis of reflex sympathetic dystrophy in hemiplegic patients

Reflex sympathetic dystrophy (RSD) is a relative common sequel after hemiplegia. The diagnosis of RSD in hemiplegic patients presents difficult clinical problems, as the symptoms and signs of RSD are not specific and RSD may be due to reasons other than hemiplegia. Bone scintigraphy has been routinely used for the diagnosis of RSD; however, the optimal acquisition protocols, diagnostic patterns and the utility of quantitation are controversial. This prospective study was conducted to demonstrate the higher predictive value of an additional late blood pool image to the three-phase bone scan compared to the regular three-phase bone scans in RSD patients associated with hemiplegia. Thirty-four RSD patients were enrolled into the study. Bone scans according to the new protocol were obtained for all patients. Those patients with either negative or positive bone scans with no evidence of RSD were followed for 6 months. The patients had positive bone scan findings and were symptomatic at the time of the study. Of these, seven patients (58.3%) subsequently became symptomatic and five patients (41.7%) remained asymptomatic at 6 months. None of the patients with negative bone scans had symptoms of RSD on presentation except one case. We conclude that the addition of a late blood pool image increases the predictive value and has an impact on initiating early treatment in asymptomatic patients.

Interobserver Reproducibility in the Interpretation of Bone Scans From Patients Suspected of Having Reflex Sympathetic Dystrophy

OBJECTIVE

This work was undertaken to identify scintigraphic patterns obtained in patients suspected of having reflex sympathetic dystrophy (RSD), now often referred to as complex regional pain syndrome, whose interpretations could be difficult.

METHODS

Ten patients had bone scans because of clinical suspicion of RSD in the lower legs. They were selected retrospectively to have a wide sample of scintigraphic patterns. The radionuclide images and a multiple-choice questionnaire were presented as a PowerPoint file that was sent electronically on the Internet to 54 Belgian nuclear medicine physicians. They had to determine whether the images were in favor of the diagnosis of RSD.

RESULTS

Twenty-eight answers (52%) were received. There was near-complete interobserver agreement for perfectly normal scans, for scans showing diffuse uptake with enhancement of periarticular activity, and for scans showing only focal hyperactivity at the site of previous trauma. Results were more discordant when the hyperactivity was mild and when there was a diffuse hypoactivity, with or without focal hyperactivity.

CONCLUSION

This study shows that using very simple methodology, it is possible to identify some scintigraphic patterns in which there is disagreement among observers and whose interpretations vary. As the results are returned to the participants, they can compare their own interpretations with those of their peers. This aspect could be useful in continuing education in medical imaging.

Complex regional pain syndrome type I: use of the International Association for the Study of Pain diagnostic criteria defined in 1994

OBJECTIVES

The objective was to assess the reported use in recent publications of the diagnostic criteria for complex regional pain syndrome type I (CRPS I) proposed by the International Association for the Study of Pain (IASP) in 1994.

METHODS

A literature search of MEDLINE (January 1996 to July 2000) was performed with use of the medical subject heading "reflex sympathetic dystrophy" and the free texts words "complex," "regional," "pain," and "syndrome." Publications in English, German, and Dutch were analyzed. From the search, 65 original publications were selected. Another 27 publications (referenced publications) that were referenced in the 65 original publications for the description of diagnostic criteria for CRPS I also were included. A standard form was used to assess a total of 92 publications. A sensitivity analysis was performed by means of analyzing three scenarios in which the diagnostic criteria were used as proposed and two combinations of less stringent criteria.

RESULTS

Use of the diagnostic criterion pain was reported in 35 (38%) of the analyzed publications. None of the original publications satisfied the proposed IASP diagnostic criteria. Four (15%) of the referenced publications satisfied the proposed IASP diagnostic criteria. Ten (15%) of the original publications referred correctly to the referenced publications. With the less strict criteria used in scenarios 2 and 3, 2 (3%) and 3 (5%), respectively, of the original publications fulfilled these criteria.

CONCLUSIONS

If the diagnostic criteria for CRPS I are not used uniformly, the populations in clinical studies may not be uniform either. Whether different authors are describing the same syndrome and whether their findings can be compared is open to question. On the basis of the results of this study, it is concluded that the IASP criteria for CRPS I are poorly used in clinical studies.

Despite clinical similarities there are significant differences between acute limb trauma and complex regional pain syndrome I (CRPS I)

In order to analyze the pathophysiology behind the clinical similarity acutely after limb trauma and in acute stages of complex regional pain syndrome (CRPS), 20 patients with external fixation after distal radius fracture (3.5 days after surgery) without signs of CRPS and 24 patients suffering from acute CRPS I (without nerve lesion; duration, 5 weeks) were investigated. Hyperalgesia to heat was tested by a feedback-controlled thermode, and to mechanical stimuli by an impact stimulator. The sympathetic nervous system was examined by measuring skin temperature (infra-red thermography), testing different sympathetic vasoconstrictor reflexes (laser-Doppler flowmetry) and quantitative sudometry after thermal load (thermoregulatory sweat test). We found hyperalgesia to heat after trauma (P<0.001), but not in CRPS, whereas mechanical hyperalgesia was present in both patient groups (trauma: P<0.001; CRPS: P<0.005). Skin temperature was significantly increased on the affected side in both patient groups (acute trauma: P<0.001; CRPS: P<0.005). However, sympathetic failure, as indicated by impairment of sympathetic vasoconstrictor reflexes (P<0.02) and hyperhidrosis (P<0.01), was found exclusively in CRPS patients. Our results indicate that pain and vasomotor disturbances may be generated by different mechanisms acutely after trauma and in acute CRPS. Despite the clinical similarity, additional changes in the peripheral or central nervous system are required for CRPS. In the light of our observations, it seems unlikely that CRPS is a simple exaggeration of post-traumatic inflammation.

The persistently irritable joint in childhood an orthopaedic perspective

Persistent joint or periarticular irritability and pain in children can have numerous explanations. This overview explores the diverse range of orthopaedic conditions, both acquired and congenital, that may lead to such a presentation.

Advantages of diagnostic nuclear medicine part 1: musculoskeletal disorders

Radionuclide scans with improved imaging techniques such as single-photon-emission tomography and three-phase scanning have become safe, well-established, and highly effective diagnostic tools in sports medicine. The greatest strengths of the techniques include providing early physiologic information about injury sites and evaluating large areas or the whole body in a single examination. As described and illustrated here, bone scans are particularly useful for diagnosing such musculoskeletal injuries as stress fractures, avulsion fractures, periostitis, myositis ossificans, and rhabdomyolysis.

Autonomic regulation of lymphatic flow in the lower extremity demonstrated on lymphoscintigraphy in patients with reflex sympathetic dystrophy

PURPOSE

Nuclear medicine techniques were used to show that the peripheral lymphatics are under autonomic control in much the same way as the blood vessels that supply the same anatomic region.

METHODS

Three patients with complex regional pain syndrome type 1 (reflex sympathetic dystrophy) involving a lower extremity were evaluated using three-phase bone scintigraphy and peripheral lymphoscintigraphy. Each patient was treated with ipsilateral chemical lumbar sympathectomy, and lymphoscintigraphy was repeated within several days of the procedure.

RESULTS

All three patients had evidence of decreased flow (compared with the contralateral extremity) to normal flow after ipsilateral sympathectomy. Bone scintigraphy, before and after sympathectomy, was difficult to interpret because of the effects of altered weight bearing. Two patients who had unilateral peripheral edema showed marked improvement after sympathectomy and increased lymphatic flow.

CONCLUSIONS

Peripheral lymphatic function is controlled by the autonomic nervous system. In reflex sympathetic dystrophy, peripheral edema may be caused by an increased sympathetic stimulus to the lymphatics. Further study of this phenomenon may show that nuclear medicine studies, such as bone scintigraphy and lymphoscintigraphy, can be used to distinguish patients who will benefit from sympathectomy from those who will not, thereby obviating invasive testing and unnecessary invasive treatment.

The usefulness of quantitative evaluation of three-phase scintigraphy in the diagnosis of post-traumatic reflex sympathetic dystrophy

Quantitative analysis of three-phase bone scintigrams was done in 70 patients with reflex sympathetic dystrophy (RSD) and in 30 patients who did not have RSD after injury to the hand or wrist. Regions of interest were selected and the uptake ratios (affected/unaffected) were calculated. Significant differences between affected and unaffected patients were seen in the metacarpal area in phase 2 of the scintigrams as well as in the metacarpophalangeal joints and metacarpal bones in phase 3. Combination of these images had the greatest diagnostic value. Sensitivity and specificity of 80% were achieved in the regions of interest in phase 3. The duration of RSD and the predisposing injury significantly affected the results of bone scintigraphy. It was also noted that a fracture may cause increased fixation of the tracer in each phase of three-phase bone scintigraphy in asymptomatic patients.

Bone atrophy in complex regional pain syndrome patients measured by microdensitometry

PURPOSE

To determine the usefulness of quantitative measurement of bone atrophy in the diagnosis and the long-term follow-up of patients with complex regional pain syndrome (CRPS). The bone-sparing effect of a 5-hydroxytriptamine (5-HT2) antagonist was also studied.

METHODS

Bone mass was measured by computerized micro-densitometry at the middle position of the second metacarpal. The effect of repeated stellate ganglion blocks (SGBs) three times per week with mepivacaine (n = 11), administration of a 5-HT2 antagonist (sarpogrelate hydrochloride, 300 mg a day po) (n = 12), and combined therapy (n = 10) were compared by micro-densitometry and conventional visual analogue scale (VAS) for analgesia after three months of treatment.

RESULTS

In CRPS patients, metacarpal index (cortical bone thickness), maximum bone density (cortical bone density), minimum bone density (trabecular bone density), and average bone density were reduced on the affected side (14.1%, 12.1%, 25.0% and 19.3% respectively). The rate of reduction in bone mass correlated with the duration of the disease (P < 0.05). Therapy with the 5-HT2 receptor antagonist (with or without repeated SGBs) decreased pain intensity (from 6.10 to 3.81 with SGB, from 6.30 to 2.91 without SGB, respectively; P < 0.01) and bone atrophy evaluated by micro-densitometry (P < 0.05). In contrast, repeated SGBs alone reduced pain intensity (from 6.30 to 2.91; P < 0.01) but did not ameliorate bone atrophy.

CONCLUSION

Bone micro-densitometry is useful in the assessment and follow-up of CRPS and for evaluation of treatment. The 5-HT2 antagonist, sarpogrelate hydrochloride, is a promising treatment for CRPS patients.

Increased lymphoscintigraphic flow pattern in the lower extremity under evaluation for lymphedema

OBJECTIVE

To analyze the clinical and scintigraphic features in four postoperative patients with lower limb edema.

DESIGN

Four case reports are presented, and causes of increased lymphatic flow are discussed.

MATERIAL AND METHODS

Filtered 99mTc-sulfur colloid (0.1 mL; 20 MBq) was administered by subcutaneous injection into the second web space of each foot. Sequential local (inguinal) and whole-body imaging was performed periodically up to 24 hours after the injections. The patients were three women who were 40, 51, and 86 years of age and an 81-year-old man.

RESULTS

Each patient had unilateral lower extremity swelling and had recently undergone an ipsilateral lower limb operation. One female patient had previously undergone proximal femoral vein ligation, and another female patient had venous insufficiency demonstrated by Doppler ultrasonography. The male patient had a history of severe arterial insufficiency, and the remaining female patient had no venous or arterial abnormalities. On lymphoscintigraphy, all patients showed increased lymphatic flow in the edematous lower limb. Only the male patient also demonstrated abnormal dermal backflow pattern.

CONCLUSION

Increased lymphatic flow most likely is a normal response to lower limb edema in the presence of normal peripheral lymphatic structures. In the four described cases, a recent lower limb surgical procedure may have resulted in disturbance of normal proximal lymphatic channels. The role of sympathetic innervation of the peripheral lymphatic system is a potential factor determining lymphatic response to trauma or surgical intervention. Increased flow on lymphoscintigraphy may not necessarily represent normal flow, especially if other scintigraphic features of abnormal lymphatic function-such as dermal backflow pattern-are present.